According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservo...According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservoirs in the Jinan Sag,eastern Junggar Basin,are clarified,and the hydrocarbon accumulation model of these reservoirs is established.The results are obtained in four aspects.First,the main body of the thick salified lake basin source rocks in the Lucaogou Formation has reached the mature stage with abundant resource base.Large-scale reservoirs are developed in the Jingjingzigou,Wutonggou and Lucaogou formations.Vertically,there are multiple sets of good regional seals,the source-reservoir-caprock assemblage is good,and there are three reservoir-forming assemblages:sub-source,intra-source and above-source.Second,dissolution,hydrocarbon charging and pore-preserving effect,and presence of chlorite film effectively increase the sub-source pore space.Oil charging is earlier than the time when the reservoir becomes densified,which improves the efficiency of hydrocarbon accumulation.Third,buoyancy and source-reservoir pressure difference together constitute the driving force of oil charging,and the micro-faults within the formation give the advantage of"source-reservoir lateral docking"under the source rock.Microfractures can be critical channels for efficient seepage and continuous charging of oil in different periods.Fourth,the Jingjingzigou Formation experienced three periods of oil accumulation in the Middle-Late Permian,Middle-Late Jurassic and Late Neogene,with the characteristics of long-distance migration and accumulation in early stage,mixed charging and accumulation in middle stage and short-distance migration and high-position accumulation in late stage.The discovery and theoretical understanding of the Permian reservoirs in the Jinan Sag reveal that the thrust belt has good conditions for forming large reservoirs,and it is promising for exploration.The study results are of guidance and reference significance for oil and gas exploration in the Jinan Sag and other geologically similar areas.展开更多
Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western sectio...Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western section of the foreland thrust belt in southern Junggar Basin are investigated. The target reservoirs are characterized by superimposition of conglomerates, sandy conglomerates and sandstones, with high content of plastic clasts. The reservoir space is mainly composed of intergranular pores. The reservoirs are overall tight, and the sandy conglomerate has the best physical properties. The coupling of short deep burial period with low paleotemperature gradient and formation overpressure led to the relatively weak diagenetic strength of the reservoirs. Specifically, the sandy conglomerates show relatively low carbonate cementation, low compaction rate and high dissolution porosity. The special stress-strain mechanism of the anticline makes the reservoirs at the top of the anticline turning point more reformed by fractures than those at the limbs, and the formation overpressure makes the fractures in open state. Moreover, the sandy conglomerates have the highest oil saturation. Typical anticline reservoirs are developed in deep part of the thrust belt, but characterized by "big trap with small reservoir". Significantly, the sandy conglomerates at the top of anticline turning point have better quality, lower in-situ stress and higher structural position than those at the limbs,with the internal hydrocarbons most enriched, making them high-yield oil/gas layers. The exponential decline of fractures makes hydrocarbon accumulation difficult in the reservoirs at the limbs. Nonetheless, plane hydrocarbon distribution is more extensive at the gentle limb than the steep limb.展开更多
Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is s...Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is still insufficient, which constrains the oil and gas exploration in deep-water areas. Based on comprehensive data of magnetic anomalies, seismic survey, and drilling, this study determines the structure characteristics of the Scotian Basin and its hydrocarbon accumulation conditions in deep waters and evaluates the deep-water hydrocarbon exploration potential. The transform faults and basement structures in the northern basin control the sedimentary framework showing thick strata in east and thin strata in west of the basin. The bowl-shaped depression formed by thermal subsidence during the transitional phase and the confined environment (micro basins) caused by salt tectonics provide favorable conditions for the development of source rocks during the depression stage (also referred to as the depression period sequence) of the basin. The progradation of large shelf-margin deltas during the drift phase and steep continental slope provide favorable conditions for the deposition of slope-floor fans on continental margins of the basin. Moreover, the source-reservoir assemblage comprising the source rocks within the depression stage and the turbidite sandstones on the continental margin in the deep waters may form large deep-water turbidite sandstone reservoirs. This study will provide a valuable reference for the deep-water hydrocarbon exploration in the Scotian Basin.展开更多
The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservo...The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.展开更多
Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration ...Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration direction of Termit superimposed marine–continental rift basin are discussed. The Termit basin is superimposed with two-phase rifts(Early Cretaceous and Paleogene). The subsidence curves from two wells on the Trakes slope in the east of the basin show high subsidence rate in the Late Cretaceous, which is believed to be high deposition rate influenced by transgression. However, a weak rift may also be developed. The depositional sequences in the Termit basin were controlled by the Late Cretaceous marine transgression cycle and the Paleogene lacustrine transgression cycle, giving rise to two types of superimposed marine–continental “source-sink” deposits. The marine and continental mixed source rocks developed universally in the whole basinduring the marine transgression period, and are overlaid by the Paleogene Sokor 1 reservoir rocks and Sokor 2 caprocks developed during the lacustrine transgression period, forming the unique superimposed marine–continental basin in WCARS. The early low geothermal gradient in the Termit basin resulted in the late hydrocarbon generated by the source rock of Upper Cretaceous Yogou in Paleogene. Mature source rock of Upper Cretaceous Donga developed in the Trakes slope, so that the double-source-supply hydrocarbon and accumulation models are proposed for the Trakes slope in which formed the oil fields. Due to virtue of the newly proposed hydrocarbon accumulation model and the exploration activities in recent years in the Termit superimposed marine–continental rift basin, an additional effective exploration area of about 2500 km2has been confirmed in the east of the basin. It is believed that potential domains such as Sokor 1, Donga and Upper Cretaceous lithologic traps in the southeast of the basin are key expected targets for exploration and frontier evaluation in future.展开更多
Based on the oil and gas exploration practice in the Songliao Basin,combined with the latest exploration and development data such as seismic,well logging and geochemistry,the basic geological conditions,oil and gas t...Based on the oil and gas exploration practice in the Songliao Basin,combined with the latest exploration and development data such as seismic,well logging and geochemistry,the basic geological conditions,oil and gas types and distribution characteristics,reservoir-forming dynamics,source-reservoir relationship and hydrocarbon accumulation model of the whole petroleum system in shallow and medium strata in the northern part of Songliao Basin are systematically studied.The shallow-medium strata in northern Songliao Basin have the conditions for the formation of whole petroleum system,with sufficient oil and gas sources,diverse reservoir types and well-developed transport system,forming a whole petroleum system centered on the source rocks of the Cretaceous Qingshankou Formation.Different types of oil and gas resources in the whole petroleum system are correlated with each other in terms of depositional system,lithologic association and physical property changes,and they,to a certain extent,have created the spatial framework with orderly symbiosis of shallow-medium conventional oil reservoirs,tight oil reservoirs and shale oil reservoirs in northern Songliao Basin.Vertically,the resources are endowed as conventional oil above source,shale oil/tight oil within source,and tight oil below source.Horizontally,conventional oil,tight oil,interlayer-type shale oil,and pure shale-type shale oil are developed in an orderly way,from the margin of the basin to the center of the depression.Three hydrocarbon accumulation models are recognized for the whole petroleum system in northern Songliao Basin,namely,buoyancy-driven charging of conventional oil above source,retention of shale oil within source,and pressure differential-driven charging of tight oil below source.展开更多
Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regiona...Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.展开更多
Transfer zones are structural areas of faults interactions where fault motion or displacement can be transferred from one fault to another, regional strain maintains laterally constant. Transfer zones are widely devel...Transfer zones are structural areas of faults interactions where fault motion or displacement can be transferred from one fault to another, regional strain maintains laterally constant. Transfer zones are widely developed in rift basins and have significance on hydrocarbon accumulation. In this review article, we attempt to summarize recent advances on the types, distance-displacement curves, evolutionary stages and controlling factors of transfer zones in rift basins and their effects on sedimentary systems, reservoir properties, trap formation and hydrocarbon migration. The formation of transfer zones is genetically related to the segmented growth of normal faults. Depending on the degree of interaction between these normal faults, transfer zones in rift basins could be divided into two types: soft-linked and hard-linked, which are further subdivided into transfer slope, oblique anticline, horst and transfer fault based on the combination patterns of normal faults. In general, the development of transfer zones experiences several stages including isolated normal faulting, transfer slope forming, complicating and breaking. During the interaction and growth of segmented normal faults, stress-strain and spatial array of faults, pre-existing basement structures, and mechanical conditions of rocks have a great influence on the location and development processes of transfer zones. A transfer zone is commonly considered as a pathway for conveying sediments from provenance to basin, and it hence exerts an essential control on the distribution of sandbodies. In addition, transfer zone is the area where stresses are concentrated, which facilitates the formation of various types of structural traps, and it is also a favorable conduit for hydrocarbon migration. Consequently, there exists great hydrocarbon potentials in transfer zones to which more attention should be given.展开更多
Gypsum/salt beds are widely developed in petroliferous basins across the world.Most basins with gypsum/salt beds have been proven to host abundant hydrocarbon resources.Previous studies on the effects of gypsum/salt b...Gypsum/salt beds are widely developed in petroliferous basins across the world.Most basins with gypsum/salt beds have been proven to host abundant hydrocarbon resources.Previous studies on the effects of gypsum/salt beds on hydrocarbon reservoirs primarily focused on their excellent sealing property as cap rocks.However,an increasing number of exploration discoveries have shown that gypsum/salt beds have the potential to promote the formation of high-quality source rocks and hydrocarbon reservoirs.Gypsum/salt beds influence the generation,preservation and accumulation of hydrocarbons.Based on the systematic analysis of the generation of hydrocarbons in global gypsum/saltbearing sequences,the study discussed the control of gypsum/salt beds on play elements,and explore the relationship between the development of gypsum/salt beds and global large-and medium-scale hydrocarbon reservoirs.Furthermore,we analyzed the correlation between typical gypsum/saltbearing sequences and their hydrocarbon generation potentials in China.In-depth analysis shows three patterns in terms of the spatial superimposition of gypsum/salt beds and source rocks,that is,postsalt pattern,inter-salt pattern and pre-salt pattern.Among others,the source rocks of the inter-salt pattern are widely developed in salt basins and of great potential for hydrocarbon exploration.展开更多
The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in...The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in this Group.Systematic investigation about the gas reservoir in Pingqiao anticline was consequently carried out in terms of characteristics of reservoir bitumen,the geochemical characteristics of natural gas,diagenetic minerals,and fluid inclusions.Based on this,combined with the reconstruction of the burial history,thermal evolution history and uplifting history of strata,and analysis of the regional tectonic settings,the hydrocarbon sources were identified and the formation and evolutionary processes of the gas reservoirs in Xixiangchi Group was revealed in this study.It was shown that the gas reservoirs have mixed gas sources from the shale source rocks in the Lower Cambrian Qiongzhusi Formation and in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation,and experienced several evolutionary stages,including the paleo-oil reservoir stage from the Late Siliurian to the Middle Permian,the paleo-gas reservoir stage from the Late Permian to the Early Cretaceous,and the superimposed accumulation and mixed-source gas reservoir stage since the Late Cretaceous.The mixed-source gas reservoir is formed by the adjustment of the Xixiangchi Group paleo-gas reservoirs and depressurization of the overpressure Wufeng-Longmaxi shale gas reservoirs and the charging of gas into the Xixiangchi Group reservoir of the Pingqiao anticline since the Late Cretaceous,which show obvious superimposed accumulation characteristics.There are different accumulation patterns in different geological periods.The accumulation pattern of the“old source-young reservoir”(i.e.hydrocarbons generated from older source rocks accumulating in younger reservoirs)dominates before the Late Cretaceous,and that of“juxtaposed young source-old reservoir”(i.e.hydrocarbons generated from younger source rocks accumulating in juxtaposed older reservoirs)dominates after the Early Cretaceous.Moreover,faults acted as critical vertical pathways for hydrocarbon migration during the evolution of the Xixiangchi Group gas reservoirs.This model provides new insights and theoretical basis for evaluation and mapping of the Xixiangchi Group play fairway in eastern Sichuan Basin.展开更多
Broom-shaped structures are widely seen in transtensional basins, including those discovered in many sags of the Bohai Bay Basin. Broom-shaped transtensional structural zones are generally petroliferous and thus impor...Broom-shaped structures are widely seen in transtensional basins, including those discovered in many sags of the Bohai Bay Basin. Broom-shaped transtensional structural zones are generally petroliferous and thus important targets for hydrocarbon exploration. This study analyzed the evolution and genetic mechanisms of the broom-shaped transtensional structures in the Gaoqing area of the Dongying Sag using the 3D seismic flattening technique and a physical simulation experiment. Furthermore, the control effects of the broom-shaped transtensional structures on hydrocarbon accumulation and distribution were discussed. The research results are as follows. The Gaoqing area is of a broom-shaped transtensional structure in planar view, composed of several arc-shaped secondary faults intersecting with high-level main fault in the same direction. On the seismic section, it appears as a typical semi-flower-like structure. In the early stage (that is, during the deposition of the Kongdian Formation to the lower submember of the 4th member of the Shahejie Formation, Es4(L)), single-fault pattern consisting of single or multiple faults in alignment was developed under extensional stress. While with the change of structural stress (that is, during the deposition of the Es4(U) to the Es2(L)), more secondary faults were formed, and came in a pattern of broom-shaped structure together with the major fault. In the late stage (that is, during the deposition of the Es1 to the Guantao Formation), the en echelon fault pattern was formed, as the major fault broke into multiple secondary faults. The divergent end of the broom-shaped transtensional structure has many secondary faults developed, the fault planes are gentle, and small-scale fan deltas are the predominant type of deposits. The hydrocarbon tends to laterally migrate far away and accumulate mianly in structural and lithologic-structural traps. On the other hand, in the convergent end, the fault planes are relatively steep, resulting in small-scale subaqueous fans or large-scale deltas deposited along the major fault, with hydrocarbon accumulating minaly in structural-lithologic traps proximal to the provenances.展开更多
The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconve...The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconventional oil production in the USA accounted for 41%of the total oil production;and unconventional natural gas production in China accounted for 35%of total gas production,showing strong growth momentum of unconventional hydrocarbons explorations.Unconventional hydrocarbons generally coexist with conventional petroleum resources;they sometimes distribute in a separate system,not coexisting with a conventional system.Identification and prediction of unconventional resources and their potentials are prominent challenges for geologists.This study analyzed the results of 12,237 drilling wells in six representative petroliferous basins in China and studied the correlations and differences between conventional and unconventional hydrocarbons by comparing their geological features.Migration and accumulation of conventional hydrocarbon are caused dominantly by buoyance.Wepropose a concept of buoyance-driven hydrocarbon accumulation depth to describe the deepest hydrocarbon accumulation depth driven dominantly by buoyance;beyond this depth the buoyance becomes unimportant for hydrocarbon accumulation.We found that the buoyance-driven hydrocarbon accumulation depth in petroliferous basins controls the different oil/gas reservoirs distribution and resource potentials.Hydrocarbon migration and accumulations above this depth is dominated by buoyancy,forming conventional reservoirs in traps with high porosity and permeability,while hydrocarbon migration and accumulation below this depth is dominated by non-buoyancy forces(mainly refers to capillary force,hydrocarbon volumeexpansion force,etc.),forming unconventional reservoirs in tight layers.The buoyance-driven hydrocarbon accumulation depths in six basins in China range from 1200mto 4200 m,which become shallowerwith increasing geothermal gradient,decreasing particle size of sandstone reservoir layers,or an uplift in the whole petroliferous basin.The predicted unconventional resource potential belowthe buoyance-driven hydrocarbon accumulation depth in six basins in China is more than 15.71×10^(9) t oil equivalent,among them 4.71×10^(9) t reserves have been proved.Worldwide,94%of 52,926 oil and gas reservoirs in 1186 basins are conventional reservoirs and only 6%of them are unconventional reservoirs.These 94%conventional reservoirs show promising exploration prospects in the deep area below buoyance-driven hydrocarbon accumulation depth.展开更多
To reveal the causes of differences in the hydrocarbon accumulation in continental marginal basins in the centralsouthern South China Sea,we used gravity-magnetic,seismic,drilling,and outcrop data to investigate the t...To reveal the causes of differences in the hydrocarbon accumulation in continental marginal basins in the centralsouthern South China Sea,we used gravity-magnetic,seismic,drilling,and outcrop data to investigate the tectonic histories of the basins and explore how these tectonic events controlled the hydrocarbon accumulation conditions in these basins.During the subduction of the Cenozoic proto-South China Sea and the expansion of the new South China Sea,the continental margin basins in the central-southern South China Sea could be classified as one of three types of epicontinental basins:southern extensional-foreland basins,western extensional-strike slip basins,and central extensional-drift basins.Because these basins have different tectonic and sedimentary histories,they also differ in their accumulated hydrocarbon resources.During the Cenozoic,the basin groups in the southern South China Sea generally progressed through three stages:faulting and subsidence from the late Eocene to the early Miocene,inversion and uplift in the middle Miocene,and subsidence since the late Miocene.Hydrocarbon source rocks with marine-continental transitional facies dominated byⅡ-Ⅲkerogen largely developed in extremely thick Miocene sedimentary series with the filling characteristics being mainly deep-water deposits in the early stage and shallow water deposits in the late stage.With well-developed sandstone and carbonate reservoirs,this stratum has a strong hydrocarbon generation potential.During the Cenozoic,the basin groups in the western South China Sea also progressed through the three developmental stages discussed previously.Hydrocarbon source rocks with lacustrine facies,marine-continental transitional facies,and terrigenous marine facies dominated byⅡ2-Ⅲkerogen largely developed in the relatively thick stratum with the filling characteristics being mainly lacustrine deposits in the early stage and marine deposits in the late stage.As a reservoir comprised of self-generated and self-stored sandstone,this unit also has a high hydrocarbon generation potential.Throughout those same three developmental stages,the basin groups in the central South China Sea generated hydrocarbon source rocks with terrigenous marine facies dominated byⅢkerogen that have developed in a stratum with medium thicknesses with the filling characteristics being mainly sandstone in the early stage and carbonate in the late stage.This reservoir,which is dominated by lower-generation and upper-storage carbonate rocks,also has a high hydrocarbon generation potential.展开更多
Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development char...Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.展开更多
Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpr...Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpressure evolution simulation is carried out.Based on the measured formation pressure,drilling fluid density and well logging data,overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure,genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure,and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs.The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt,the deeper the formation,the bigger the scale of the overpressure is.Laterally,overpressure is least developed in the mountain front belt,most developed in the fold anticline belt,and relatively developed in the slope belt.The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts.The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area.The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects:When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent,expanding the exploration depth of deep reservoirs;reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation;under the background of overall overpressure,both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation,and the pressure coefficient between 1.6 and 2.1 is the best.展开更多
The Yunkai low uplift with low exploration degree is close to the Baiyun sag,and has hydrocarbon exploration potential in the deepwater area of the Pearl River Mouth Basin.Based on seismic and drilling data,balanced p...The Yunkai low uplift with low exploration degree is close to the Baiyun sag,and has hydrocarbon exploration potential in the deepwater area of the Pearl River Mouth Basin.Based on seismic and drilling data,balanced profiles and growth strata,this paper mainly discusses geological structures and formation processes of the Yunkai low uplift,and also analyzes the characteristics of fault system and their influence on hydrocarbon migration and accumulation.The EWtrending basement faults divide the Yunkai low uplift into two parts,i.e.the southern sector and the northern sector.The northern sector is a relatively wide and gentle uplift,while the southern sector is composed of two secondary half-grabens with faulting in the south and overlapping in the north.The Yunkai low uplift experienced three major formation stages,including the rapid uplifting stage during the deposition period of the Eocene Wenchang Formation,the slow uplifting stage during the deposition period of the Late Eocene-Middle Miocene Enping-Hanjiang formations,and the whole burial stage from the Middle Miocene to present.The extensional faults in the Yunkai low uplift and its adjacent areas strike mainly along the NW,NWW and near-EW directions.Also,the strikes of faults present a clockwise rotation from the deep to the shallow strata.According to effects of faults on hydrocarbon accumulation the faults in the Yunkai low uplift and its adjacent areas can be divided into trap-controlled faults and source-controlled faults.The trap-controlled faults control trap development and can effectively seal oil and gas.The source-controlled faults connect directly source rocks and reservoirs,which are highly active during the rifting stage and weakly active since the Miocene.This activity features of the source-controlled faults is beneficial to migration of the early crude oil from the Baiyun sag to the high part of the Yunkai low uplift,but is not good for migration of the late natural gas.In the Yunkai low uplift and its adjacent areas,the traps in the deep Zhuhai and Enping formations that are close to source rocks in the Baiyun sag should be the favorable exploration objectives.展开更多
Continental shale strata in China are rich in petroleum resources and are an important area to strengthen domestic oil exploration and development.Based on the latest progress in geological research and exploration an...Continental shale strata in China are rich in petroleum resources and are an important area to strengthen domestic oil exploration and development.Based on the latest progress in geological research and exploration and development of petroleum inside continental source kitchens of China National Petroleum Corporation exploration areas in recent two years,we have achieved the following results:(1)The geological connotations of continental hydrocarbon accumulation inside source kitchen and"sweet spot"have been proposed.The intra-source petroleum accumulation refers to the accumulation of liquid-rich hydrocarbons retained or captured in the continental organic-rich shale strata,and"sweet spot"refers to the favorable reservoir with higher oil content,better physical properties,easier to stimulate and higher in commercial development value in the overall oil-bearing continental source rock series,they can be divided into three types,interlayer,hybrid sediment and shale.(2)High-quality shale formations in both salt water and freshwater lacustrine basins can generate hydrocarbons on a large scale,shale strata have multiple types of favorable reservoirs with large-scale storage capacity,the intra-source shale strata are overall oil-bearing and large in resource scale,and there are multiple favorable shale series for development.The exploration and development practice is propelling the formation of a series of exploration and development key technologies with"sweet spot exploration"and"volume development"as the core.Some pilot tests of these technologies have provided an important scientific basis for the economic and effective development of hydrocarbon accumulation inside source kitchen,and popularization of these technologies have achieved encouraging results preliminarily.(3)Two types of continental intra-source petroleum resources in China have great potential,including medium-high maturity with liquid-rich hydrocarbons and medium-low maturity with organic-rich matter.The Ordos,Songliao,Bohai Bay and Junggar basins are the main areas of these resources.By addressing the theoretical and technical challenges in the exploration and development,the two types of resources inside continental source kitchens will become the realistic and major strategic replacement oil resources respectively in the future.展开更多
A new method for reconstructing the geological history of hydrocarbon accumulation is developed, which are constrained by U-Pb isotope age and clumped isotope((35)47) temperature of host minerals of hydrocarbon-bearin...A new method for reconstructing the geological history of hydrocarbon accumulation is developed, which are constrained by U-Pb isotope age and clumped isotope((35)47) temperature of host minerals of hydrocarbon-bearing inclusions. For constraining the time and depth of hydrocarbon accumulation by the laser in-situ U-Pb isotope age and clumped isotope temperature, there are two key steps:(1) Investigating feature, abundance and distribution patterns of liquid and gaseous hydrocarbon inclusions with optical microscopes.(2) Dating laser in-situ U-Pb isotope age and measuring clumped isotope temperature of the host minerals of hydrocarbon inclusions. These technologies have been applied for studying the stages of hydrocarbon accumulation in the Sinian Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin. By dating the U-Pb isotope age and measuring the temperature of clumped isotope((35)47) of the host minerals of hydrocarbon inclusions in dolomite, three stages of hydrocarbon accumulation were identified:(1) Late Silurian: the first stage of oil accumulation at(416±23) Ma.(2) Late Permian to Early Triassic: the second stage of oil accumulation between(248±27) Ma and(246.3±1.5) Ma.(3) Yanshan to Himalayan period: gas accumulation between(115±69) Ma and(41±10) Ma. The reconstructed hydrocarbon accumulation history of the Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin is highly consistent with the tectonic-burial history, basin thermal history and hydrocarbon generation history, indicating that the new method is a reliable way for reconstructing the hydrocarbon accumulation history.展开更多
The Sahul Platform where the Sunset-Loxton Shoals and Chuditch gas fields were discovered is located between the Timor Trough to the north and the Malita Graben to the south. These areas are located respectively 440 k...The Sahul Platform where the Sunset-Loxton Shoals and Chuditch gas fields were discovered is located between the Timor Trough to the north and the Malita Graben to the south. These areas are located respectively 440 km and 380 km northwest of Darwin in the northern Bonaparte Basin, Australia. Based on the structural evolution of the northern Bonaparte Basin, data from the wells Loxton Shoals 1, Sunset 1 and Chuditch 1 in the Sahul Platform and Heron 1 in the Malita Graben depocentre, and the Seismic Line N11606 were used to clarify the geological conditions and reconstruct the hydrocarbon accumulation processes in the study area. BasinMod 1-D, 2-D, and 3-D software was used for modeling. The Plover Formation source rock was a poor-to-good hydrocarbon generative potential and reached the middle to late mature oil window in the Sunset-Loxton Shoals field whereas in the Chuditch field, it was an overall fair-to-good hydrocarbon generative potential, and attained the Late mature oil window. The Flamingo, and the Echuca Shoals formations source rocks in the same field were a fair and good hydrocarbon generation potential respectively, and both reached mid-mature oil window. In the Malita Graben depocentre, the Petrel (Frigate) and the Echuca Shoals formations source rocks were a poor-to-very good hydrocarbon generating potential, and had attained wet gas window at the present day. The analyses of organic matter showed that the source rocks in the study area and Malita Graben were gas prone with kerogen types II2 & III and III predominantly. The Middle Jurassic Plover Formation sandstone reservoir in the Sunset-Loxton field was a poor-to-very good quality and potential for gas beds, and it was a very poor-to-very good quality and potential for gas beds in the Chuditch field. The intensities of gas generation and expulsion were more than of oil ones either in the Sahul Platform or in the Malita Graben. The Plover, Petrel (Frigate) and Echuca Shoals formations source rocks in the wells Chuditch 1 and Heron 1, except for the Flamingo Formation in the well Chuditch 1, had higher gas and oil expelling efficiencies than the Plover Formation source rock of the wells in the Sunset-Loxton Shoals field. The hydrocarbon migrated mainly from the Upper Jurassic Frigate Shale source rock in the Malita Graben depocentre (structurally lower) to the Plover Formation sandstone reservoir in the Sunset-Loxton Shoals field during the Late Cretaceous at 66 Ma. In the Chuditch field, the hydrocarbon migration to the Plover Formation sandstone reservoir was initiated during the Late Miocene at 7.5 Ma from the Middle Jurassic Plover Formation source rock in the well Chuditch 1. Nowadays, the main migration pathways are from the southeastward and southward of the Sunset-Loxton Shoals field, and from southward and eastward of the Chuditch field, precisely from the hydrocarbon source kitchens of the Malita Graben depocentre. The traps in the Sahul Platform have been effective to receive the migrated hydrocarbon.展开更多
Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution la...Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution law of pores and fractures in the Cretaceous tight reservoir in the Liuhe Basin,and reveals its controlling effect on tight oil and gas accumulation.The results show that intercrystalline pores,intergranular pores and dissolution pores are scattered and only developed in shallow tight reservoirs,while microfractures are developed in both shallow and deep layers,which are the main type of reservoir space in the study area.The results of mercury intrusion porosimetry and nitrogen gas adsorption show that with the increase of depth,the proportion of macropores(microcracks)increases,while the proportion of micropores decreases.There are two stages of microfractures developed in the study area,corresponding to the initial fault depression stage from late Jurassic to early late Cretaceous and compressional uplift at the end of late Cretaceous.According to the principle of“inversion and back-stripping method”,combined with the data of optical microscopy and inclusions,the time of each key diagenesis and its contribution to porosity are revealed,and the porosity evolution history of reservoirs in different diagenetic stages is quantitatively restored.The porosity reduction rate of compaction can reach more than 80%,which is the main reason for reservoir densification.The relationship between pore evolution history and oil and gas accumulation history reveals that during the oil and gas filling period of the Xiahuapidianzi Formation(90-85 Ma),the reservoir porosity is only 1.15%,but the development of microfractures in the first stage of the reservoir is conducive to oil and gas accumulation.展开更多
基金Supported by the PetroChina Oil&Gas and New Energy Company Project(2022KT0405)PetroChina Science and Technology Major Project(2021DJ0605)Basic and Prospective Science and Technology Project of Petrochina Science and Technology Management Department(2021DJ0404).
文摘According to the latest drilling and the analysis of the burial history,source rock evolution history and hydrocarbon accumulation history,the sub-source hydrocarbon accumulation characteristics of the Permian reservoirs in the Jinan Sag,eastern Junggar Basin,are clarified,and the hydrocarbon accumulation model of these reservoirs is established.The results are obtained in four aspects.First,the main body of the thick salified lake basin source rocks in the Lucaogou Formation has reached the mature stage with abundant resource base.Large-scale reservoirs are developed in the Jingjingzigou,Wutonggou and Lucaogou formations.Vertically,there are multiple sets of good regional seals,the source-reservoir-caprock assemblage is good,and there are three reservoir-forming assemblages:sub-source,intra-source and above-source.Second,dissolution,hydrocarbon charging and pore-preserving effect,and presence of chlorite film effectively increase the sub-source pore space.Oil charging is earlier than the time when the reservoir becomes densified,which improves the efficiency of hydrocarbon accumulation.Third,buoyancy and source-reservoir pressure difference together constitute the driving force of oil charging,and the micro-faults within the formation give the advantage of"source-reservoir lateral docking"under the source rock.Microfractures can be critical channels for efficient seepage and continuous charging of oil in different periods.Fourth,the Jingjingzigou Formation experienced three periods of oil accumulation in the Middle-Late Permian,Middle-Late Jurassic and Late Neogene,with the characteristics of long-distance migration and accumulation in early stage,mixed charging and accumulation in middle stage and short-distance migration and high-position accumulation in late stage.The discovery and theoretical understanding of the Permian reservoirs in the Jinan Sag reveal that the thrust belt has good conditions for forming large reservoirs,and it is promising for exploration.The study results are of guidance and reference significance for oil and gas exploration in the Jinan Sag and other geologically similar areas.
基金Supported by the National Natural Science Foundation of China (41902118)Natural Science Foundation of Xinjiang Uygur Autonomous Region (2022D01B141)+1 种基金Natural Science Foundation of Heilongjiang Province (LH2021D003)Heilongjiang Postdoctoral Fund (No.LBH-Z20045)。
文摘Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western section of the foreland thrust belt in southern Junggar Basin are investigated. The target reservoirs are characterized by superimposition of conglomerates, sandy conglomerates and sandstones, with high content of plastic clasts. The reservoir space is mainly composed of intergranular pores. The reservoirs are overall tight, and the sandy conglomerate has the best physical properties. The coupling of short deep burial period with low paleotemperature gradient and formation overpressure led to the relatively weak diagenetic strength of the reservoirs. Specifically, the sandy conglomerates show relatively low carbonate cementation, low compaction rate and high dissolution porosity. The special stress-strain mechanism of the anticline makes the reservoirs at the top of the anticline turning point more reformed by fractures than those at the limbs, and the formation overpressure makes the fractures in open state. Moreover, the sandy conglomerates have the highest oil saturation. Typical anticline reservoirs are developed in deep part of the thrust belt, but characterized by "big trap with small reservoir". Significantly, the sandy conglomerates at the top of anticline turning point have better quality, lower in-situ stress and higher structural position than those at the limbs,with the internal hydrocarbons most enriched, making them high-yield oil/gas layers. The exponential decline of fractures makes hydrocarbon accumulation difficult in the reservoirs at the limbs. Nonetheless, plane hydrocarbon distribution is more extensive at the gentle limb than the steep limb.
基金supported by the National Science and Technology Major Project of China(2016ZX05033)the Project of SINOPEC Science and Technology Department(P19021-2)the Basic Prospective Research Project of SINOPEC(P22214-2).
文摘Commercial hydrocarbon reservoirs have been discovered in shallow-water areas of the Scotian Basin, Eastern Canada. However, knowledge about the structure and hydrocarbon accumulation characteristics of the basin is still insufficient, which constrains the oil and gas exploration in deep-water areas. Based on comprehensive data of magnetic anomalies, seismic survey, and drilling, this study determines the structure characteristics of the Scotian Basin and its hydrocarbon accumulation conditions in deep waters and evaluates the deep-water hydrocarbon exploration potential. The transform faults and basement structures in the northern basin control the sedimentary framework showing thick strata in east and thin strata in west of the basin. The bowl-shaped depression formed by thermal subsidence during the transitional phase and the confined environment (micro basins) caused by salt tectonics provide favorable conditions for the development of source rocks during the depression stage (also referred to as the depression period sequence) of the basin. The progradation of large shelf-margin deltas during the drift phase and steep continental slope provide favorable conditions for the deposition of slope-floor fans on continental margins of the basin. Moreover, the source-reservoir assemblage comprising the source rocks within the depression stage and the turbidite sandstones on the continental margin in the deep waters may form large deep-water turbidite sandstone reservoirs. This study will provide a valuable reference for the deep-water hydrocarbon exploration in the Scotian Basin.
基金Supported by PetroChina Science and Technology Development Project(2023ZZ0206,2021DJ0303,2021DJ0105,2021DJ0203)National Natural ScienceFoundation of China(U22B6002).
文摘The complexity of diagenesis and hydrocarbon accumulation in the deep reservoirs in southern Junggar Basin restricts hydrocarbon exploration in the lower reservoir assemblage. The lithofacies and diagenesis of reservoirs in the Cretaceous Qingshuihe Formation in the Gaoquan structure of the Sikeshu Sag, southern Junggar Basin were analyzed. On this basis, the thermal history was calibrated using calcite in-situ U-Pb dating and fluid inclusion analysis to depict the hydrocarbon accumulation process in the Gaoquan structure. The results show that the Qingshuihe reservoir experienced two phases of calcite cementation and three phases of hydrocarbon charging. The calcite cements are dated to be (122.1±6.4) Ma, (14.4±1.0) Ma - (14.2±0.3) Ma. The hydrocarbon charging events occurred at around 14.2-30.0 Ma (low-mature oil), 14.2 Ma (mature oil), and 2 Ma (high-mature gas). The latter two phases of hydrocarbon charging contributed dominantly to the formation of reservoir. Due to the S-N compressive thrust activity during the late Himalayan period since 2 Ma, the traps in the Gaoquan structure were reshaped, especially the effective traps which developed in the main reservoir-forming period were decreased significantly in scale, resulting in weak hydrocarbon shows in the middle-lower part of the structure. This indicates that the effective traps in key reservoir-forming period controlled hydrocarbon enrichment and distribution in the lower reservoir assemblage. Calcite U-Pb dating combined with fluid inclusion analysis can help effectively describe the complex diagenesis and hydrocarbon accumulation process in the central-west part of the basin.
基金Supported by CNPC Scientific Research and Technology Development Project (2021DJ3103)CNODC Overseas Rresearch and Development Support Project (2023-YF-01-04)。
文摘Based on the seismic and drilling data, casting thin sections, geochemical analysis of oil and rock samples, and hydrocarbon generation history simulation, the hydrocarbon accumulation characteristics and exploration direction of Termit superimposed marine–continental rift basin are discussed. The Termit basin is superimposed with two-phase rifts(Early Cretaceous and Paleogene). The subsidence curves from two wells on the Trakes slope in the east of the basin show high subsidence rate in the Late Cretaceous, which is believed to be high deposition rate influenced by transgression. However, a weak rift may also be developed. The depositional sequences in the Termit basin were controlled by the Late Cretaceous marine transgression cycle and the Paleogene lacustrine transgression cycle, giving rise to two types of superimposed marine–continental “source-sink” deposits. The marine and continental mixed source rocks developed universally in the whole basinduring the marine transgression period, and are overlaid by the Paleogene Sokor 1 reservoir rocks and Sokor 2 caprocks developed during the lacustrine transgression period, forming the unique superimposed marine–continental basin in WCARS. The early low geothermal gradient in the Termit basin resulted in the late hydrocarbon generated by the source rock of Upper Cretaceous Yogou in Paleogene. Mature source rock of Upper Cretaceous Donga developed in the Trakes slope, so that the double-source-supply hydrocarbon and accumulation models are proposed for the Trakes slope in which formed the oil fields. Due to virtue of the newly proposed hydrocarbon accumulation model and the exploration activities in recent years in the Termit superimposed marine–continental rift basin, an additional effective exploration area of about 2500 km2has been confirmed in the east of the basin. It is believed that potential domains such as Sokor 1, Donga and Upper Cretaceous lithologic traps in the southeast of the basin are key expected targets for exploration and frontier evaluation in future.
基金Supported by the PetroChina Major Science and Technology Project (2016E0201,2021ZZ10,2021DJ0101)。
文摘Based on the oil and gas exploration practice in the Songliao Basin,combined with the latest exploration and development data such as seismic,well logging and geochemistry,the basic geological conditions,oil and gas types and distribution characteristics,reservoir-forming dynamics,source-reservoir relationship and hydrocarbon accumulation model of the whole petroleum system in shallow and medium strata in the northern part of Songliao Basin are systematically studied.The shallow-medium strata in northern Songliao Basin have the conditions for the formation of whole petroleum system,with sufficient oil and gas sources,diverse reservoir types and well-developed transport system,forming a whole petroleum system centered on the source rocks of the Cretaceous Qingshankou Formation.Different types of oil and gas resources in the whole petroleum system are correlated with each other in terms of depositional system,lithologic association and physical property changes,and they,to a certain extent,have created the spatial framework with orderly symbiosis of shallow-medium conventional oil reservoirs,tight oil reservoirs and shale oil reservoirs in northern Songliao Basin.Vertically,the resources are endowed as conventional oil above source,shale oil/tight oil within source,and tight oil below source.Horizontally,conventional oil,tight oil,interlayer-type shale oil,and pure shale-type shale oil are developed in an orderly way,from the margin of the basin to the center of the depression.Three hydrocarbon accumulation models are recognized for the whole petroleum system in northern Songliao Basin,namely,buoyancy-driven charging of conventional oil above source,retention of shale oil within source,and pressure differential-driven charging of tight oil below source.
基金Supported by the National Natural Science Foundation Project of China(U22B6002)Prospective Basic Technology Research Project of PetroChina(2021DJ0605).
文摘Based on outcrop,seismic and drilling data,the main regional unconformities in the Sichuan Basin and their controls on hydrocarbon accumulation were systematically studied.Three findings are obtained.First,six regional stratigraphic unconformities are mainly developed in the Sichuan Basin,from the bottom up which are between pre-Sinian and Sinian,between Sinian and Cambrian,between pre-Permian and Permian,between middle and upper Permian,between middle and upper Triassic,and between Triassic and Jurassic.Especially,16 of 21l conventional(and tight)gas fields discovered are believed to have formed in relation to regional unconformities.Second,regional unconformity mainly controls hydrocarbon accumulation from five aspects:(1)The porosity and permeability of reservoirs under the unconformity are improved through weathering crust karstification to form large-scale karst reservoirs;(2)Good source-reservoir-caprock assemblage can form near the unconformity,which provides a basis for forming large gas field;(3)Regional unconformity may lead to stratigraphic pinch-out and rugged ancient landform,giving rise to a large area of stratigraphic and lithologic trap groups;(4)Regional unconformity provides a dominant channel for lateral migration of oil and gas;and(5)Regional unconformity is conducive to large-scale accumulation of oil and gas.Third,the areas related to regional unconformities are the exploration focus of large gas fields in the Sichuan Basin.The pre-Sinian is found with source rocks,reservoir rocks and other favorable conditions for the formation of large gas fields,and presents a large exploration potential.Thus,it is expected to be an important strategic replacement.
基金funded by the National Natural Science Foundation of China(No.42072149).
文摘Transfer zones are structural areas of faults interactions where fault motion or displacement can be transferred from one fault to another, regional strain maintains laterally constant. Transfer zones are widely developed in rift basins and have significance on hydrocarbon accumulation. In this review article, we attempt to summarize recent advances on the types, distance-displacement curves, evolutionary stages and controlling factors of transfer zones in rift basins and their effects on sedimentary systems, reservoir properties, trap formation and hydrocarbon migration. The formation of transfer zones is genetically related to the segmented growth of normal faults. Depending on the degree of interaction between these normal faults, transfer zones in rift basins could be divided into two types: soft-linked and hard-linked, which are further subdivided into transfer slope, oblique anticline, horst and transfer fault based on the combination patterns of normal faults. In general, the development of transfer zones experiences several stages including isolated normal faulting, transfer slope forming, complicating and breaking. During the interaction and growth of segmented normal faults, stress-strain and spatial array of faults, pre-existing basement structures, and mechanical conditions of rocks have a great influence on the location and development processes of transfer zones. A transfer zone is commonly considered as a pathway for conveying sediments from provenance to basin, and it hence exerts an essential control on the distribution of sandbodies. In addition, transfer zone is the area where stresses are concentrated, which facilitates the formation of various types of structural traps, and it is also a favorable conduit for hydrocarbon migration. Consequently, there exists great hydrocarbon potentials in transfer zones to which more attention should be given.
基金This study was funded by a key project of the National Natural Science Fund of China(41930426)a key project of the Petrochemical Joint Fund(U1663201).
文摘Gypsum/salt beds are widely developed in petroliferous basins across the world.Most basins with gypsum/salt beds have been proven to host abundant hydrocarbon resources.Previous studies on the effects of gypsum/salt beds on hydrocarbon reservoirs primarily focused on their excellent sealing property as cap rocks.However,an increasing number of exploration discoveries have shown that gypsum/salt beds have the potential to promote the formation of high-quality source rocks and hydrocarbon reservoirs.Gypsum/salt beds influence the generation,preservation and accumulation of hydrocarbons.Based on the systematic analysis of the generation of hydrocarbons in global gypsum/saltbearing sequences,the study discussed the control of gypsum/salt beds on play elements,and explore the relationship between the development of gypsum/salt beds and global large-and medium-scale hydrocarbon reservoirs.Furthermore,we analyzed the correlation between typical gypsum/saltbearing sequences and their hydrocarbon generation potentials in China.In-depth analysis shows three patterns in terms of the spatial superimposition of gypsum/salt beds and source rocks,that is,postsalt pattern,inter-salt pattern and pre-salt pattern.Among others,the source rocks of the inter-salt pattern are widely developed in salt basins and of great potential for hydrocarbon exploration.
基金supported by the National Key R&D Program of China grant(2017YFC0603105).
文摘The Xixiangchi Group in eastern Sichuan Basin has great potential for natural gas exploration.However,there is a lack of in-depth studies of the hydrocarbon sources and the formation and evolution of gas reservoirs in this Group.Systematic investigation about the gas reservoir in Pingqiao anticline was consequently carried out in terms of characteristics of reservoir bitumen,the geochemical characteristics of natural gas,diagenetic minerals,and fluid inclusions.Based on this,combined with the reconstruction of the burial history,thermal evolution history and uplifting history of strata,and analysis of the regional tectonic settings,the hydrocarbon sources were identified and the formation and evolutionary processes of the gas reservoirs in Xixiangchi Group was revealed in this study.It was shown that the gas reservoirs have mixed gas sources from the shale source rocks in the Lower Cambrian Qiongzhusi Formation and in the Upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation,and experienced several evolutionary stages,including the paleo-oil reservoir stage from the Late Siliurian to the Middle Permian,the paleo-gas reservoir stage from the Late Permian to the Early Cretaceous,and the superimposed accumulation and mixed-source gas reservoir stage since the Late Cretaceous.The mixed-source gas reservoir is formed by the adjustment of the Xixiangchi Group paleo-gas reservoirs and depressurization of the overpressure Wufeng-Longmaxi shale gas reservoirs and the charging of gas into the Xixiangchi Group reservoir of the Pingqiao anticline since the Late Cretaceous,which show obvious superimposed accumulation characteristics.There are different accumulation patterns in different geological periods.The accumulation pattern of the“old source-young reservoir”(i.e.hydrocarbons generated from older source rocks accumulating in younger reservoirs)dominates before the Late Cretaceous,and that of“juxtaposed young source-old reservoir”(i.e.hydrocarbons generated from younger source rocks accumulating in juxtaposed older reservoirs)dominates after the Early Cretaceous.Moreover,faults acted as critical vertical pathways for hydrocarbon migration during the evolution of the Xixiangchi Group gas reservoirs.This model provides new insights and theoretical basis for evaluation and mapping of the Xixiangchi Group play fairway in eastern Sichuan Basin.
文摘Broom-shaped structures are widely seen in transtensional basins, including those discovered in many sags of the Bohai Bay Basin. Broom-shaped transtensional structural zones are generally petroliferous and thus important targets for hydrocarbon exploration. This study analyzed the evolution and genetic mechanisms of the broom-shaped transtensional structures in the Gaoqing area of the Dongying Sag using the 3D seismic flattening technique and a physical simulation experiment. Furthermore, the control effects of the broom-shaped transtensional structures on hydrocarbon accumulation and distribution were discussed. The research results are as follows. The Gaoqing area is of a broom-shaped transtensional structure in planar view, composed of several arc-shaped secondary faults intersecting with high-level main fault in the same direction. On the seismic section, it appears as a typical semi-flower-like structure. In the early stage (that is, during the deposition of the Kongdian Formation to the lower submember of the 4th member of the Shahejie Formation, Es4(L)), single-fault pattern consisting of single or multiple faults in alignment was developed under extensional stress. While with the change of structural stress (that is, during the deposition of the Es4(U) to the Es2(L)), more secondary faults were formed, and came in a pattern of broom-shaped structure together with the major fault. In the late stage (that is, during the deposition of the Es1 to the Guantao Formation), the en echelon fault pattern was formed, as the major fault broke into multiple secondary faults. The divergent end of the broom-shaped transtensional structure has many secondary faults developed, the fault planes are gentle, and small-scale fan deltas are the predominant type of deposits. The hydrocarbon tends to laterally migrate far away and accumulate mianly in structural and lithologic-structural traps. On the other hand, in the convergent end, the fault planes are relatively steep, resulting in small-scale subaqueous fans or large-scale deltas deposited along the major fault, with hydrocarbon accumulating minaly in structural-lithologic traps proximal to the provenances.
基金by the National Natural Science Foundation of China(No.U19B6003-02)the National Basic Research Program(973)of China(No.2011CB201100).
文摘The discovery of unconventional hydrocarbon resources since the late 20th century changed geologists’understanding of hydrocarbon migration and accumulations and provides a solution to energy shortage.In 2016,unconventional oil production in the USA accounted for 41%of the total oil production;and unconventional natural gas production in China accounted for 35%of total gas production,showing strong growth momentum of unconventional hydrocarbons explorations.Unconventional hydrocarbons generally coexist with conventional petroleum resources;they sometimes distribute in a separate system,not coexisting with a conventional system.Identification and prediction of unconventional resources and their potentials are prominent challenges for geologists.This study analyzed the results of 12,237 drilling wells in six representative petroliferous basins in China and studied the correlations and differences between conventional and unconventional hydrocarbons by comparing their geological features.Migration and accumulation of conventional hydrocarbon are caused dominantly by buoyance.Wepropose a concept of buoyance-driven hydrocarbon accumulation depth to describe the deepest hydrocarbon accumulation depth driven dominantly by buoyance;beyond this depth the buoyance becomes unimportant for hydrocarbon accumulation.We found that the buoyance-driven hydrocarbon accumulation depth in petroliferous basins controls the different oil/gas reservoirs distribution and resource potentials.Hydrocarbon migration and accumulations above this depth is dominated by buoyancy,forming conventional reservoirs in traps with high porosity and permeability,while hydrocarbon migration and accumulation below this depth is dominated by non-buoyancy forces(mainly refers to capillary force,hydrocarbon volumeexpansion force,etc.),forming unconventional reservoirs in tight layers.The buoyance-driven hydrocarbon accumulation depths in six basins in China range from 1200mto 4200 m,which become shallowerwith increasing geothermal gradient,decreasing particle size of sandstone reservoir layers,or an uplift in the whole petroliferous basin.The predicted unconventional resource potential belowthe buoyance-driven hydrocarbon accumulation depth in six basins in China is more than 15.71×10^(9) t oil equivalent,among them 4.71×10^(9) t reserves have been proved.Worldwide,94%of 52,926 oil and gas reservoirs in 1186 basins are conventional reservoirs and only 6%of them are unconventional reservoirs.These 94%conventional reservoirs show promising exploration prospects in the deep area below buoyance-driven hydrocarbon accumulation depth.
基金granted by the National Science and Technology Major Project(No.2016ZX05026-004)National Natural Science Foundation of China(No.91528303)。
文摘To reveal the causes of differences in the hydrocarbon accumulation in continental marginal basins in the centralsouthern South China Sea,we used gravity-magnetic,seismic,drilling,and outcrop data to investigate the tectonic histories of the basins and explore how these tectonic events controlled the hydrocarbon accumulation conditions in these basins.During the subduction of the Cenozoic proto-South China Sea and the expansion of the new South China Sea,the continental margin basins in the central-southern South China Sea could be classified as one of three types of epicontinental basins:southern extensional-foreland basins,western extensional-strike slip basins,and central extensional-drift basins.Because these basins have different tectonic and sedimentary histories,they also differ in their accumulated hydrocarbon resources.During the Cenozoic,the basin groups in the southern South China Sea generally progressed through three stages:faulting and subsidence from the late Eocene to the early Miocene,inversion and uplift in the middle Miocene,and subsidence since the late Miocene.Hydrocarbon source rocks with marine-continental transitional facies dominated byⅡ-Ⅲkerogen largely developed in extremely thick Miocene sedimentary series with the filling characteristics being mainly deep-water deposits in the early stage and shallow water deposits in the late stage.With well-developed sandstone and carbonate reservoirs,this stratum has a strong hydrocarbon generation potential.During the Cenozoic,the basin groups in the western South China Sea also progressed through the three developmental stages discussed previously.Hydrocarbon source rocks with lacustrine facies,marine-continental transitional facies,and terrigenous marine facies dominated byⅡ2-Ⅲkerogen largely developed in the relatively thick stratum with the filling characteristics being mainly lacustrine deposits in the early stage and marine deposits in the late stage.As a reservoir comprised of self-generated and self-stored sandstone,this unit also has a high hydrocarbon generation potential.Throughout those same three developmental stages,the basin groups in the central South China Sea generated hydrocarbon source rocks with terrigenous marine facies dominated byⅢkerogen that have developed in a stratum with medium thicknesses with the filling characteristics being mainly sandstone in the early stage and carbonate in the late stage.This reservoir,which is dominated by lower-generation and upper-storage carbonate rocks,also has a high hydrocarbon generation potential.
基金funded by the National Key Research and Development Program‘Deep Land Resources Exploration and Exploitation’special project(2017YFC0603106)the Project of Science and Technology Department of the Southwest Oil and Gas Field Company,Petrochina(20210301-02)。
文摘Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.
基金PetroChina Science and Technology Development Project(2021DJ0105,2021DJ0203,2021DJ0303)National Natural Science Foundation of China(42172164,42002177)。
文摘Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpressure evolution simulation is carried out.Based on the measured formation pressure,drilling fluid density and well logging data,overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure,genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure,and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs.The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt,the deeper the formation,the bigger the scale of the overpressure is.Laterally,overpressure is least developed in the mountain front belt,most developed in the fold anticline belt,and relatively developed in the slope belt.The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts.The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area.The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects:When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent,expanding the exploration depth of deep reservoirs;reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation;under the background of overall overpressure,both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation,and the pressure coefficient between 1.6 and 2.1 is the best.
基金funded by the National Science and Technology Major Project of China(2016ZX05026-007)the National Natural Science Foundation of China(42072149)。
文摘The Yunkai low uplift with low exploration degree is close to the Baiyun sag,and has hydrocarbon exploration potential in the deepwater area of the Pearl River Mouth Basin.Based on seismic and drilling data,balanced profiles and growth strata,this paper mainly discusses geological structures and formation processes of the Yunkai low uplift,and also analyzes the characteristics of fault system and their influence on hydrocarbon migration and accumulation.The EWtrending basement faults divide the Yunkai low uplift into two parts,i.e.the southern sector and the northern sector.The northern sector is a relatively wide and gentle uplift,while the southern sector is composed of two secondary half-grabens with faulting in the south and overlapping in the north.The Yunkai low uplift experienced three major formation stages,including the rapid uplifting stage during the deposition period of the Eocene Wenchang Formation,the slow uplifting stage during the deposition period of the Late Eocene-Middle Miocene Enping-Hanjiang formations,and the whole burial stage from the Middle Miocene to present.The extensional faults in the Yunkai low uplift and its adjacent areas strike mainly along the NW,NWW and near-EW directions.Also,the strikes of faults present a clockwise rotation from the deep to the shallow strata.According to effects of faults on hydrocarbon accumulation the faults in the Yunkai low uplift and its adjacent areas can be divided into trap-controlled faults and source-controlled faults.The trap-controlled faults control trap development and can effectively seal oil and gas.The source-controlled faults connect directly source rocks and reservoirs,which are highly active during the rifting stage and weakly active since the Miocene.This activity features of the source-controlled faults is beneficial to migration of the early crude oil from the Baiyun sag to the high part of the Yunkai low uplift,but is not good for migration of the late natural gas.In the Yunkai low uplift and its adjacent areas,the traps in the deep Zhuhai and Enping formations that are close to source rocks in the Baiyun sag should be the favorable exploration objectives.
基金Supported by the National Key Basic Research and Development Program(973 Program),China(2014CB239000)China National Science and Technology Major Project(2016ZX05046)
文摘Continental shale strata in China are rich in petroleum resources and are an important area to strengthen domestic oil exploration and development.Based on the latest progress in geological research and exploration and development of petroleum inside continental source kitchens of China National Petroleum Corporation exploration areas in recent two years,we have achieved the following results:(1)The geological connotations of continental hydrocarbon accumulation inside source kitchen and"sweet spot"have been proposed.The intra-source petroleum accumulation refers to the accumulation of liquid-rich hydrocarbons retained or captured in the continental organic-rich shale strata,and"sweet spot"refers to the favorable reservoir with higher oil content,better physical properties,easier to stimulate and higher in commercial development value in the overall oil-bearing continental source rock series,they can be divided into three types,interlayer,hybrid sediment and shale.(2)High-quality shale formations in both salt water and freshwater lacustrine basins can generate hydrocarbons on a large scale,shale strata have multiple types of favorable reservoirs with large-scale storage capacity,the intra-source shale strata are overall oil-bearing and large in resource scale,and there are multiple favorable shale series for development.The exploration and development practice is propelling the formation of a series of exploration and development key technologies with"sweet spot exploration"and"volume development"as the core.Some pilot tests of these technologies have provided an important scientific basis for the economic and effective development of hydrocarbon accumulation inside source kitchen,and popularization of these technologies have achieved encouraging results preliminarily.(3)Two types of continental intra-source petroleum resources in China have great potential,including medium-high maturity with liquid-rich hydrocarbons and medium-low maturity with organic-rich matter.The Ordos,Songliao,Bohai Bay and Junggar basins are the main areas of these resources.By addressing the theoretical and technical challenges in the exploration and development,the two types of resources inside continental source kitchens will become the realistic and major strategic replacement oil resources respectively in the future.
基金Supported by the China National Science and Technology Major Project(2016ZX05004-002)Basic Research and Strategic Reserve Technology Research Fund of Institutes Directly Under CNPC(2018D-5008-03)PetroChina Science and Technology Project(2019D-5009-16)。
文摘A new method for reconstructing the geological history of hydrocarbon accumulation is developed, which are constrained by U-Pb isotope age and clumped isotope((35)47) temperature of host minerals of hydrocarbon-bearing inclusions. For constraining the time and depth of hydrocarbon accumulation by the laser in-situ U-Pb isotope age and clumped isotope temperature, there are two key steps:(1) Investigating feature, abundance and distribution patterns of liquid and gaseous hydrocarbon inclusions with optical microscopes.(2) Dating laser in-situ U-Pb isotope age and measuring clumped isotope temperature of the host minerals of hydrocarbon inclusions. These technologies have been applied for studying the stages of hydrocarbon accumulation in the Sinian Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin. By dating the U-Pb isotope age and measuring the temperature of clumped isotope((35)47) of the host minerals of hydrocarbon inclusions in dolomite, three stages of hydrocarbon accumulation were identified:(1) Late Silurian: the first stage of oil accumulation at(416±23) Ma.(2) Late Permian to Early Triassic: the second stage of oil accumulation between(248±27) Ma and(246.3±1.5) Ma.(3) Yanshan to Himalayan period: gas accumulation between(115±69) Ma and(41±10) Ma. The reconstructed hydrocarbon accumulation history of the Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin is highly consistent with the tectonic-burial history, basin thermal history and hydrocarbon generation history, indicating that the new method is a reliable way for reconstructing the hydrocarbon accumulation history.
文摘The Sahul Platform where the Sunset-Loxton Shoals and Chuditch gas fields were discovered is located between the Timor Trough to the north and the Malita Graben to the south. These areas are located respectively 440 km and 380 km northwest of Darwin in the northern Bonaparte Basin, Australia. Based on the structural evolution of the northern Bonaparte Basin, data from the wells Loxton Shoals 1, Sunset 1 and Chuditch 1 in the Sahul Platform and Heron 1 in the Malita Graben depocentre, and the Seismic Line N11606 were used to clarify the geological conditions and reconstruct the hydrocarbon accumulation processes in the study area. BasinMod 1-D, 2-D, and 3-D software was used for modeling. The Plover Formation source rock was a poor-to-good hydrocarbon generative potential and reached the middle to late mature oil window in the Sunset-Loxton Shoals field whereas in the Chuditch field, it was an overall fair-to-good hydrocarbon generative potential, and attained the Late mature oil window. The Flamingo, and the Echuca Shoals formations source rocks in the same field were a fair and good hydrocarbon generation potential respectively, and both reached mid-mature oil window. In the Malita Graben depocentre, the Petrel (Frigate) and the Echuca Shoals formations source rocks were a poor-to-very good hydrocarbon generating potential, and had attained wet gas window at the present day. The analyses of organic matter showed that the source rocks in the study area and Malita Graben were gas prone with kerogen types II2 & III and III predominantly. The Middle Jurassic Plover Formation sandstone reservoir in the Sunset-Loxton field was a poor-to-very good quality and potential for gas beds, and it was a very poor-to-very good quality and potential for gas beds in the Chuditch field. The intensities of gas generation and expulsion were more than of oil ones either in the Sahul Platform or in the Malita Graben. The Plover, Petrel (Frigate) and Echuca Shoals formations source rocks in the wells Chuditch 1 and Heron 1, except for the Flamingo Formation in the well Chuditch 1, had higher gas and oil expelling efficiencies than the Plover Formation source rock of the wells in the Sunset-Loxton Shoals field. The hydrocarbon migrated mainly from the Upper Jurassic Frigate Shale source rock in the Malita Graben depocentre (structurally lower) to the Plover Formation sandstone reservoir in the Sunset-Loxton Shoals field during the Late Cretaceous at 66 Ma. In the Chuditch field, the hydrocarbon migration to the Plover Formation sandstone reservoir was initiated during the Late Miocene at 7.5 Ma from the Middle Jurassic Plover Formation source rock in the well Chuditch 1. Nowadays, the main migration pathways are from the southeastward and southward of the Sunset-Loxton Shoals field, and from southward and eastward of the Chuditch field, precisely from the hydrocarbon source kitchens of the Malita Graben depocentre. The traps in the Sahul Platform have been effective to receive the migrated hydrocarbon.
基金founded by the National Natural Science Foundation of China(41922015)。
文摘Tight oil and gas in the Cretaceous has been found in the Liuhe Basin,but the rules of tight reservoir and oil and gas accumulation are not clear.This paper discusses the developmental characteristics and evolution law of pores and fractures in the Cretaceous tight reservoir in the Liuhe Basin,and reveals its controlling effect on tight oil and gas accumulation.The results show that intercrystalline pores,intergranular pores and dissolution pores are scattered and only developed in shallow tight reservoirs,while microfractures are developed in both shallow and deep layers,which are the main type of reservoir space in the study area.The results of mercury intrusion porosimetry and nitrogen gas adsorption show that with the increase of depth,the proportion of macropores(microcracks)increases,while the proportion of micropores decreases.There are two stages of microfractures developed in the study area,corresponding to the initial fault depression stage from late Jurassic to early late Cretaceous and compressional uplift at the end of late Cretaceous.According to the principle of“inversion and back-stripping method”,combined with the data of optical microscopy and inclusions,the time of each key diagenesis and its contribution to porosity are revealed,and the porosity evolution history of reservoirs in different diagenetic stages is quantitatively restored.The porosity reduction rate of compaction can reach more than 80%,which is the main reason for reservoir densification.The relationship between pore evolution history and oil and gas accumulation history reveals that during the oil and gas filling period of the Xiahuapidianzi Formation(90-85 Ma),the reservoir porosity is only 1.15%,but the development of microfractures in the first stage of the reservoir is conducive to oil and gas accumulation.
