The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to...The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.展开更多
The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation ...The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-cluster horizontal well, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×10^(4) t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.展开更多
Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displ...Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displacement parameters on oil displacement efficiency.The research shows that,in the displacement method with water injected from the edge of the reservoir,early depletion production is conducive to the elastic expansion of the gas cap,forming the three-dimensional displacement of"upper pressure and lower pushing",and the oil displacement effect is good.When gas injection at the top and water injection at the edge are used for synergistic displacement,the injection timing has different influences on the oil displacement effects of high and low parts.Considering the overall oil displacement efficiency,the injection pressure should be greater than the bubble point pressure of crude oil.Two displacement methods are recommended with the reasonable injection time at 20–25 MPa.The injection speed has the same influence on different injection media.Appropriately reducing the injection speed is conducive to the stability of the displacement front,delaying the breakthrough of injection media and improving the oil displacement effect.The reasonable injection rate of water flooding is 0.075 mL/min,the reasonable injection rates of water and gas are 0.15 mL/min and 0.10 mL/min,respectively in gas-water synergistic displacement.Gas-water synergistic displacement is conducive to the production of crude oil at high position,and has crude oil recovery 5.0%–14.8%higher than water flooding from the edge,so it is recommended as the development mode of Khasib reservoir at the middle and late stages.展开更多
Dynamic performance on solids flow with water in deviated tubing is essential for the reliability of pump and normal operation of horizontal and directional wells.Compared with coal-water flow in vertical tubing and s...Dynamic performance on solids flow with water in deviated tubing is essential for the reliability of pump and normal operation of horizontal and directional wells.Compared with coal-water flow in vertical tubing and sand-oil flow with high production in deviated tubing,solids deposition with water shows obvious non-symmetric distributions in deviated tubing from simulations and experiments.The mathematical model of two phase flow was developed under coupling conditions of deviated tubing,low flow rate and viscosity based on the kinetic theory of granular flow and first-order discrete scheme.The results show that solid-water stratified flow in deviated tubing can be divided into two zones of suspension bed and the moving bed throughout the flow field.The solid flowing velocity with water is negative and particles slide down at the bottom of moving bed zone.The process of solids flow with water in deviated tubing will produce pressure loss and consume the kinetic energy.The thickness of deposited layer and the flowing velocity of solids flow downward with water at the moving bed zone enhance with the decreased inlet flow rate and the increased particle size,tubing inside diameter(ID)and inclination angle.Solids are easier into suspension from the upper part of moving bed zone to suspension bed zone and more solid particles flow with water towards the tubing outlet with the increase of inlet flowing velocity.The decision is made to reduce the screen width,tubing ID and inclination angle to maintain to be greater than critical deposition velocity in order to prevent solids settling.And it provides the theoretical basis and technical reserves for solid control and offers an effective approach to enhance tubing cleaning in deviated strings.展开更多
D-T_(2)two-dimensional nuclear magnetic resonance(2D NMR)logging technology can distinguish pore fluid types intuitively,and it is widely used in oil and gas exploration.Many 2D NMR inversion methods(e.g.,truncated si...D-T_(2)two-dimensional nuclear magnetic resonance(2D NMR)logging technology can distinguish pore fluid types intuitively,and it is widely used in oil and gas exploration.Many 2D NMR inversion methods(e.g.,truncated singular value decomposition(TSVD),Butler-Reds-Dawson(BRD),LM-norm smoothing,and TIST-L1 regularization methods)have been proposed successively,but most are limited to numerical simulations.This study focused on the applicability of different inversion methods for NMR logging data of various acquisition sequences,from which the optimal inversion method was selected based on the comparative analysis.First,the two-dimensional NMR logging principle was studied.Then,these inversion methods were studied in detail,and the precision and computational efficiency of CPMG and diffusion editing(DE)sequences obtained from oil-water and gas-water models were compared,respectively.The inversion results and calculation time of truncated singular value decomposition(TSVD),Butler-Reds-Dawson(BRD),LM-norm smoothing,and TIST-L1 regularization were compared and analyzed through numerical simulations.The inversion method was optimized to process SP mode logging data from the MR Scanner instrument.The results showed that the TIST-regularization and LM-norm smoothing methods were more accurate for the CPMG and DE sequence echo trains of the oil-water and gas-water models.However,the LM-norm smoothing method was less time-consuming,making it more suitable for logging data processing.A case study in well A25 showed that the processing results by the LM-norm smoothing method were consistent with GEOLOG software.This demonstrates that the LM-norm smoothing method is applicable in practical NMR logging processing.展开更多
Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the ...Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined.The Cambrian platform margin mound-shoal complex is divided into mound base,mound core,mound front,mound back and mound flat microfacies,which are composed of dolomites of seven textures with facies indication.The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed,and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established:namely,the first stage of gentle slope symmetric accretion type,the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type.Their microfacies are respectively characterized by-mound base-mound back+(small)mound core+mound front-mound flat"symmetric vertical accretion structure,"mound base-(large)mound core+mound front-mound flat"asymmetric vertical accretion structure,"mound base-(small)mound core+mound front-mound flat"asymmetric lateral progradation structure.With most developed favorable reservoir facies belt,the steep slope asymmetric accretion type mound-shoal complex with the characteristics of"large mound and large shoal"is the exploration target for oil and gas reservoir.展开更多
Fluid typing from nuclear magnetic resonance(NMR)logging in oil-wet tight sandstone reservoirs is proving to be diffi cult;thus,research into the NMR logging response mechanism and analysis methods is critical.The NMR...Fluid typing from nuclear magnetic resonance(NMR)logging in oil-wet tight sandstone reservoirs is proving to be diffi cult;thus,research into the NMR logging response mechanism and analysis methods is critical.The NMR response mechanism and theoretical method were investigated based on the oil-water distribution in the pores under oil-wet conditions.The data processing method is studied based on NMR dual-TW activation principle,and the equations of macroscopic magnetization vector,fl uid volume,and relaxation parameters are derived,which is a nonlinear inversion problem.The simulated annealing algorithm is used,and the fl uid relaxation parameters,oil volume,and water volume of the fl ushing zone are calculated.An ideal reservoir model is set up,and simulation results indicate that the above-mentioned NMR relaxation theory and algorithms are valid.A case study is conducted in Huanjiang Oilfi eld in the Ordos Basin,China.The calculated oil saturation of the fl ushing zone is consistent with the oil saturation calculated using the Archie formula,and the test results indicated that the new method is applicable.Moreover,the fl uid-typing cross-plot combined with oil test data is constructed on the basis of the saturation of the fl ushing zone,improving the accuracy of fl uid identifi cation.展开更多
Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate...Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate recovery(EUR) of shale oil and gas of the wells are predicted by using two classical EUR estimation models, and the average values predicted excluding the effect of engineering factors are taken as the final EUR. Key geological factors controlling EUR of shale oil and gas are fully investigated. The reservoir capacity, resources, flow capacity and fracability are the four key geological parameters controlling EUR. The storage capacity of shale oil and gas is directly controlled by total porosity and hydrocarbon-bearing porosity, and indirectly controlled by total organic carbon(TOC) and vitrinite reflectance(Ro). The resources of shale oil and gas are controlled by hydrocarbon-bearing porosity and effective shale thickness etc. The flow capacity of shale oil and gas is controlled by effective permeability, crude oil density, gas-oil ratio, condensate oil-gas ratio, formation pressure gradient, and Ro. The fracability of shale is directly controlled by brittleness index, and indirectly controlled by clay content in volume. EUR of shale oil and gas is controlled by six geological parameters: it is positively correlated with effective shale thickness, TOC and fracture porosity, negatively correlated with clay content in volume, and increases firstly and then decreases with the rise of Ro and formation pressure gradient. Under the present upper limit of horizontal well fracturing effective thickness of 65 m and the lower limit of EUR of 3×10^(4) m^(3), when TOC<2.3%, or Ro<0.85%, or clay content in volume larger than 25%, and fractures and micro-fractures aren’t developed, favorable areas of shale oil and gas hardly occur.展开更多
Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as l...Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.展开更多
Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change.As the end-product of peatlands,coals have preserved a large amount of palaeoenvironmental information.The carbon accu...Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change.As the end-product of peatlands,coals have preserved a large amount of palaeoenvironmental information.The carbon accumulation rate and the net primary productivity(NPP)of coal-forming peatlands can be used as proxies for recovering palaeoenvironments.A super-thick coal seam(42°35'N,91°25'E)was developed in the Middle Jurassic Xishanyao Formation in the Shaerhu coalfield in the southern margin of the Tuha(Turpan-Hami)Basin,northwestern China.In this study,we use the time series analysis to identify the periods of Milankovitch orbital cycles in the Gamma-ray curve of this super-thick(124.85 m)coal and then use the obtained cycle periods of 405 ka,173 ka,44 ka,37.6 ka,22.5 ka to calculate the timeframe of the coalforming peatlands which ranges from 2703.44 to 2975.11 ka.Considering that the carbon content of the coal seam is 78.32%and the carbon loss during the coalification is about 25.80%,the carbon accumulation rate of the targeted coal seam is estimated to be 58.47-64.34 g C/m^(2)·a,and the NPP is estimated to be252.28-277.63 g C/m^(2)·a.The main palaeoenvironmental factors controlling the NPP of peatlands are CO_2content,palaeolatitude and palaeotemperature.The reduced NPP values of the palaeo-peatlands in the Shaerhu coalfield can be attributed to the mid-palaeolatitude and/or too low atmospheric CO_2contents.To a certain extent,the NPP of palaeo-peatlands reflects the changes in atmospheric CO_2,which can further reveal the dynamic response of the global carbon cycle to climate change.Therefore,predicting the level of NPP in the Middle Jurassic and studying the final destination of carbon in the ecosystem are beneficial to understanding the coal-forming process and palaeoenvironment.展开更多
To improve the oil recovery and economic efficiency in heavy oil reservoirs in late steam flooding,taking J6 Block of Xinjiang Oilfield as the research object,3D physical modeling experiments of steam flooding,CO2-foa...To improve the oil recovery and economic efficiency in heavy oil reservoirs in late steam flooding,taking J6 Block of Xinjiang Oilfield as the research object,3D physical modeling experiments of steam flooding,CO2-foam assisted steam flooding,and CO2 assisted steam flooding under different perforation conditions are conducted,and CO2-assisted steam flooding is proposed for reservoirs in the late stage of steam flooding.The experimental results show that after adjusting the perforation in late steam flooding,the CO2 assisted steam flooding formed a lateral expansion of the steam chamber in the middle and lower parts of the injection well and a development mode for the production of overriding gravity oil drainage in the top chamber of the production well;high temperature water,oil,and CO2 formed stable low-viscosity quasi-single-phase emulsified fluid;and CO2 acted as a thermal insulation in the steam chamber at the top,reduced the steam partial pressure inside the steam chamber,and effectively improved the heat efficiency of injected steam.Based on the three-dimensional physical experiments and the developed situation of the J6 block in Xinjiang Oilfield,the CO2 assisted steam flooding for the J6 block was designed.The application showed that the CO2 assisted steam flooding made the oil vapor ratio increase from 0.12 to 0.16 by 34.0%,the oil recovery increase from 16.1%to 21.5%,and the final oil recovery goes up to 66.5%compared to steam flooding after perforation adjustment.展开更多
The growth and structure of anionic micelles of sodium dodecyl trioxyethylene sulfate (AES) in the presence of multivalent counterion Al3+ were investigated by means of dynamic rheological methods. It has been obtaine...The growth and structure of anionic micelles of sodium dodecyl trioxyethylene sulfate (AES) in the presence of multivalent counterion Al3+ were investigated by means of dynamic rheological methods. It has been obtained by themeasurements of shear viscosity, complex viscosity anddynamic moduli, as well as the application of Cox-Merz rule and Cole-Cole plot that wormlike micelle and networkstructure could be formed in AES/AlCl3 aqueous solutions. The structure was of a character of nonlinear viscoelasticfluid and departure from the simple Maxwell model. Thetechnique of freeze-fracture transmission electronmicroscopy (FF-TEM) was also used to confirm theformation of this interesting structure.展开更多
The secondary migration mechanism,enrichment factors of Jurassic tight oil in central Sichuan Basin were well investigated through physical simulation experiment of reservoir formation,casting and fluorescent thin sec...The secondary migration mechanism,enrichment factors of Jurassic tight oil in central Sichuan Basin were well investigated through physical simulation experiment of reservoir formation,casting and fluorescent thin sections,field emission scanning electron microscope(FESEM)and environment scanning electron microscope(ESEM).The results show that migration of Jurassic tight oil in central Sichuan Basin is a low-velocity non-Darcy flow through low-efficient migration path under the huge migration driving force,and has three migration and seepage stages,i.e.viscous flow stage,nonlinear seepage stage,and quasi-liner seepage stage.Microscopically,the migration pathway of tight oil is the porefracture composite conduction;macroscopically,the migration mode of tight oil is the large-scale shortedistance migration.Distribution of favorable zones of tight oil is controlled by distribution of high-quality source rocks.The hydrocarbon-generation strength of 0.4106 t/km2 can be as a threshold to determine favorable zone of tight oil in the study area.The reservoirs with high permeability and high porosity can form tight oil sweet spots,and the development degree of fractures is closely related to well with high yield of tight oil well.展开更多
Efficient large-scale development of ultra-low-permeability reservoirs(0.3-1 mD)has been achieved in the Changqing Oilfield,Ordos Basin of China.According to unique features of petroleum exploration and development in...Efficient large-scale development of ultra-low-permeability reservoirs(0.3-1 mD)has been achieved in the Changqing Oilfield,Ordos Basin of China.According to unique features of petroleum exploration and development in this basin,tight oil herein refers to petroleum that occurs in oil-bearing shales and interbedded tight sandstone reservoirs adjacent to source rocks with ambient air permeability<0.3 mD.Tight oil in tight sandstone and shale have generally not yet experienced large-scale long-distance migration.In the Yanchang Formation,tight oil has mainly accumulated in the semi-deep to deep lacustrine facies,typically in oil-bearing shales and tight sandstones of the 7th member oil-bearing formation and tight sandstones of the 6th member oil-bearing formation in the center of the basin.Tight oil resource in the Ordos Basin is characterized by wide spatial distribution,excellent source rocks,extremely tight sandstone reservoirs,complex pore throat structures,poor physical properties,high oil saturation,good crude-oil properties,and low reservoir pressure.A fundamental feature of the continuous oil and gas accumulation in tight oil reservoirs is the widespread development of nano-scale pore-throat systems.In the Yanchang Formation,most of connected pore throats in tight sandstone reservoirs have diameters greater than critical pore throat diameter,allowing oil and gas migration in the tight reservoirs.According to contact relationship between tight reservoirs and source rocks,three types of tight oil reservoirs are identified in the Yanchang Formation,i.e.,tight massive sandstone reservoir,sand-shale interbed reservoir,and oil-bearing shale reservoir.In the Ordos Basin,tight oil is widely distributed in the 6th and 7th members of the Yanchang Formation,with total resources estimated to be 3×10^(9) t.These include>1×10^(9) t of oil resources in shale in the 7th member of the Yanchang Formation and approximately 0.9×10^(9) t and 1.1×10^(9) t of tight sandstone oil resource in the 6th and 7th members of the Yanchang Formation,respectively.These tight oil resources are the realistic resources addition for the oilfield,which can ensure an annual production of 50×10^(6) t of oil and gas equivalent and maintain long-term stable oil production in the Changqing Oilfield,Ordos Basin,China.展开更多
Water-sensitivity is a factor that must be paid attention to in the reservoir development stage of oil and gas fields.As a clastic reservoir,the water effect of Ahe formation in the northern structural belt of Kuqa is...Water-sensitivity is a factor that must be paid attention to in the reservoir development stage of oil and gas fields.As a clastic reservoir,the water effect of Ahe formation in the northern structural belt of Kuqa is strong as a whole,but the mechanism analysis of medium and strong water-sensitivity effect is restricted by the evaluation method with permeability damage rate as the main parameter.Taking the shape of water-sensitivity test curve as the starting point,combined with the analysis of microscopic pore throat and clay minerals,the difference of permeability change rate measured by samples is characterized.The strong to medium water-sensitivity effects in the study layer are divided into three types:The permeability gradually decreases in the early stage-the rapid decrease in the late stage,the continuous decrease in the permeability,and the rapid decrease in the early stage-the slow decrease in the later stage.As awidely developed reservoir space in the study section,the micropore not only has the characteristics of fine pore size and easy blockage,but also serves as the occurrence space of the main water-sensitive mineral illite-smectite mixed layer.Therefore,the change types of the above different water sensitivity test curves are mainly controlled by the difference of micropore content.When the micropore content is low,the permeability decreases slowly in the early stage and decreases rapidly in the later stage(type Ⅰ),while when the micropore content is high,the permeability decreases rapidly in the early stage and slowly decreases in the later stage(type Ⅱ),while when the micropore content is medium,the permeability decreases continuously,and there is no obvious rate change(type Ⅲ)before and after the micropore content.The results show that the structural characteristics and relative content differences of micropores in the samples are the internal mechanism of the difference of water sensitivity effect types.展开更多
基金funded by the National Natural Science Foundation of China(No.U22B6002)the“14th Five-Year”Forward-looking Basic Science and Technology Project of China National Petroleum Company Limited(No.2022DJ2107).
文摘The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.
基金Supported by the PetroChina Science and Technology Major Project(2021DJ1806,2023ZZ15).
文摘The reservoirs in the seventh member of the Triassic Yanchang Formation (Chang 7 Member) in the Qingcheng Oilfield of the Ordos Basin are characterized by thin sandbody, tight rocks, high heterogeneity, low formation pressure coefficient, and complex geomorphology. Through the efforts in the stages of exploration, appraisal, pilot testing and development, a series of key technologies have been formed, including “sweet spot” optimization, differentiated three-dimensional well deployment, fast drilling and completion of large-cluster horizontal well, intensively-staged volume fracturing in long horizontal well, and optimization of rational production system. Furthermore, a production organization mode represented by factory-like operations on loess platform has been implemented. Application of these technologies has enabled to significantly improve the single-well production of the Qingcheng Oilfield, reduce the investment cost, and realize a large-scale and beneficial development at a full cost below $55 per barrel. In 2022, the annual production of Chang 7 shale oil in the Ordos Basin reached 221×10^(4) t, accounting for 70% of the annual shale oil production of China. The practice of development technologies in the Qingcheng Oilfield provides valuable references for efficient development of continental shale oil.
基金Supported by the Scientific Research and Technology Development Project of CNPC(2019D-4410)。
文摘Based on the oil,gas and water distribution characteristics of Khasib reservoir in Halfaya oilfield,Iraq,a core displacement experiment is designed to evaluate the influence of different displacement methods and displacement parameters on oil displacement efficiency.The research shows that,in the displacement method with water injected from the edge of the reservoir,early depletion production is conducive to the elastic expansion of the gas cap,forming the three-dimensional displacement of"upper pressure and lower pushing",and the oil displacement effect is good.When gas injection at the top and water injection at the edge are used for synergistic displacement,the injection timing has different influences on the oil displacement effects of high and low parts.Considering the overall oil displacement efficiency,the injection pressure should be greater than the bubble point pressure of crude oil.Two displacement methods are recommended with the reasonable injection time at 20–25 MPa.The injection speed has the same influence on different injection media.Appropriately reducing the injection speed is conducive to the stability of the displacement front,delaying the breakthrough of injection media and improving the oil displacement effect.The reasonable injection rate of water flooding is 0.075 mL/min,the reasonable injection rates of water and gas are 0.15 mL/min and 0.10 mL/min,respectively in gas-water synergistic displacement.Gas-water synergistic displacement is conducive to the production of crude oil at high position,and has crude oil recovery 5.0%–14.8%higher than water flooding from the edge,so it is recommended as the development mode of Khasib reservoir at the middle and late stages.
基金funded by National Natural Science Foundation of China(Grant No.52074161)National Science and Technology Major Project of China(Grant No.2016ZX05065-001)+2 种基金Taishan Scholar Project of Shandong Province(Grant No.tsqn202211177)Shandong Provincial Plan for Introduction and Cultivation of Young Pioneers in Colleges and Universities(Grant No.2021-QingChuang-30613019)Natural Science Foundation of Shandong Province(Grant No.ZR2022ME173).
文摘Dynamic performance on solids flow with water in deviated tubing is essential for the reliability of pump and normal operation of horizontal and directional wells.Compared with coal-water flow in vertical tubing and sand-oil flow with high production in deviated tubing,solids deposition with water shows obvious non-symmetric distributions in deviated tubing from simulations and experiments.The mathematical model of two phase flow was developed under coupling conditions of deviated tubing,low flow rate and viscosity based on the kinetic theory of granular flow and first-order discrete scheme.The results show that solid-water stratified flow in deviated tubing can be divided into two zones of suspension bed and the moving bed throughout the flow field.The solid flowing velocity with water is negative and particles slide down at the bottom of moving bed zone.The process of solids flow with water in deviated tubing will produce pressure loss and consume the kinetic energy.The thickness of deposited layer and the flowing velocity of solids flow downward with water at the moving bed zone enhance with the decreased inlet flow rate and the increased particle size,tubing inside diameter(ID)and inclination angle.Solids are easier into suspension from the upper part of moving bed zone to suspension bed zone and more solid particles flow with water towards the tubing outlet with the increase of inlet flowing velocity.The decision is made to reduce the screen width,tubing ID and inclination angle to maintain to be greater than critical deposition velocity in order to prevent solids settling.And it provides the theoretical basis and technical reserves for solid control and offers an effective approach to enhance tubing cleaning in deviated strings.
基金sponsored by the National Natural Science Foundation of China(Nos.42174149,41774144)the National Major Projects(No.2016ZX05014-001).
文摘D-T_(2)two-dimensional nuclear magnetic resonance(2D NMR)logging technology can distinguish pore fluid types intuitively,and it is widely used in oil and gas exploration.Many 2D NMR inversion methods(e.g.,truncated singular value decomposition(TSVD),Butler-Reds-Dawson(BRD),LM-norm smoothing,and TIST-L1 regularization methods)have been proposed successively,but most are limited to numerical simulations.This study focused on the applicability of different inversion methods for NMR logging data of various acquisition sequences,from which the optimal inversion method was selected based on the comparative analysis.First,the two-dimensional NMR logging principle was studied.Then,these inversion methods were studied in detail,and the precision and computational efficiency of CPMG and diffusion editing(DE)sequences obtained from oil-water and gas-water models were compared,respectively.The inversion results and calculation time of truncated singular value decomposition(TSVD),Butler-Reds-Dawson(BRD),LM-norm smoothing,and TIST-L1 regularization were compared and analyzed through numerical simulations.The inversion method was optimized to process SP mode logging data from the MR Scanner instrument.The results showed that the TIST-regularization and LM-norm smoothing methods were more accurate for the CPMG and DE sequence echo trains of the oil-water and gas-water models.However,the LM-norm smoothing method was less time-consuming,making it more suitable for logging data processing.A case study in well A25 showed that the processing results by the LM-norm smoothing method were consistent with GEOLOG software.This demonstrates that the LM-norm smoothing method is applicable in practical NMR logging processing.
基金Supported by the National Natural Science Foundation of China(41772103)China National Science and Technology Major Project(2016ZX05007-002)Petrochina Science and Technology Major Project(2016E-0204)。
文摘Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined.The Cambrian platform margin mound-shoal complex is divided into mound base,mound core,mound front,mound back and mound flat microfacies,which are composed of dolomites of seven textures with facies indication.The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed,and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established:namely,the first stage of gentle slope symmetric accretion type,the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type.Their microfacies are respectively characterized by-mound base-mound back+(small)mound core+mound front-mound flat"symmetric vertical accretion structure,"mound base-(large)mound core+mound front-mound flat"asymmetric vertical accretion structure,"mound base-(small)mound core+mound front-mound flat"asymmetric lateral progradation structure.With most developed favorable reservoir facies belt,the steep slope asymmetric accretion type mound-shoal complex with the characteristics of"large mound and large shoal"is the exploration target for oil and gas reservoir.
基金This work was supported by the National Natural Science Foundation of China(41774144)the National Science and Technology Major Project“The Demonstration Project for Exploration and Development of Large Lithostratigraphic Oil and Gas Reservoirs in the Ordos Basin(2016ZX05050).
文摘Fluid typing from nuclear magnetic resonance(NMR)logging in oil-wet tight sandstone reservoirs is proving to be diffi cult;thus,research into the NMR logging response mechanism and analysis methods is critical.The NMR response mechanism and theoretical method were investigated based on the oil-water distribution in the pores under oil-wet conditions.The data processing method is studied based on NMR dual-TW activation principle,and the equations of macroscopic magnetization vector,fl uid volume,and relaxation parameters are derived,which is a nonlinear inversion problem.The simulated annealing algorithm is used,and the fl uid relaxation parameters,oil volume,and water volume of the fl ushing zone are calculated.An ideal reservoir model is set up,and simulation results indicate that the above-mentioned NMR relaxation theory and algorithms are valid.A case study is conducted in Huanjiang Oilfi eld in the Ordos Basin,China.The calculated oil saturation of the fl ushing zone is consistent with the oil saturation calculated using the Archie formula,and the test results indicated that the new method is applicable.Moreover,the fl uid-typing cross-plot combined with oil test data is constructed on the basis of the saturation of the fl ushing zone,improving the accuracy of fl uid identifi cation.
基金Supported by the PetroChina Science and Technology Department Project(2012A-4802-02)National Key Basic Research and Development Program(2014CB239000)。
文摘Based on 991 groups of analysis data of shale samples from the Lower Member of the Cretaceous Eagle Ford Formation of 1317 production wells and 72 systematic coring wells in the U.S. Gulf Basin, the estimated ultimate recovery(EUR) of shale oil and gas of the wells are predicted by using two classical EUR estimation models, and the average values predicted excluding the effect of engineering factors are taken as the final EUR. Key geological factors controlling EUR of shale oil and gas are fully investigated. The reservoir capacity, resources, flow capacity and fracability are the four key geological parameters controlling EUR. The storage capacity of shale oil and gas is directly controlled by total porosity and hydrocarbon-bearing porosity, and indirectly controlled by total organic carbon(TOC) and vitrinite reflectance(Ro). The resources of shale oil and gas are controlled by hydrocarbon-bearing porosity and effective shale thickness etc. The flow capacity of shale oil and gas is controlled by effective permeability, crude oil density, gas-oil ratio, condensate oil-gas ratio, formation pressure gradient, and Ro. The fracability of shale is directly controlled by brittleness index, and indirectly controlled by clay content in volume. EUR of shale oil and gas is controlled by six geological parameters: it is positively correlated with effective shale thickness, TOC and fracture porosity, negatively correlated with clay content in volume, and increases firstly and then decreases with the rise of Ro and formation pressure gradient. Under the present upper limit of horizontal well fracturing effective thickness of 65 m and the lower limit of EUR of 3×10^(4) m^(3), when TOC<2.3%, or Ro<0.85%, or clay content in volume larger than 25%, and fractures and micro-fractures aren’t developed, favorable areas of shale oil and gas hardly occur.
基金Project(2017QHZ031)supported by Scientific Research Starting Project of Southwest Petroleum University,ChinaProject(18TD0013)supported by Science and Technology Innovation Team of Education Department of Sichuan for Dynamical System and Its Applications,ChinaProject(2017CXTD02)supported by Youth Science and Technology Innovation Team of Southwest Petroleum University for Nonlinear Systems,China。
文摘Faulted gas reservoirs are very common in reality,where some linear leaky faults divide the gas reservoir into several reservoir regions with distinct physical properties.This kind of gas reservoirs is also known as linear composite(LC)gas reservoirs.Although some analytical/semi-analytical models have been proposed to investigate pressure behaviors of producing wells in LC reservoirs based on the linear composite ideas,almost all of them focus on vertical wells and studies on multiple fractured horizontal wells are rare.After the pressure wave arrives at the leaky fault,pressure behaviors of multiple fractured horizontal wells will be affected by the leaky faults.Understanding the effect of leaky faults on pressure behaviors of multiple fractured horizontal wells is critical to the development design.Therefore,a semi-analytical model of finite-conductivity multiple fractured horizontal(FCMFH)wells in LC gas reservoirs is established based on Laplace-space superposition principle and fracture discrete method.The proposed model is validated against commercial numerical simulator.Type curves are obtained to study pressure characteristics and identify flow regimes.The effects of some parameters on type curves are discussed.The proposed model will have a profound effect on developing analytical/semi-analytical models for other complex well types in LC gas reservoirs.
基金supported by Science Fund for Creative Research Groups of the National Natural Science Foundation of China (Grant No.42321002)the National Natural Science Foundation of China (41572090)。
文摘Peatlands have obvious carbon storage capacity and are crucial in mitigating global climate change.As the end-product of peatlands,coals have preserved a large amount of palaeoenvironmental information.The carbon accumulation rate and the net primary productivity(NPP)of coal-forming peatlands can be used as proxies for recovering palaeoenvironments.A super-thick coal seam(42°35'N,91°25'E)was developed in the Middle Jurassic Xishanyao Formation in the Shaerhu coalfield in the southern margin of the Tuha(Turpan-Hami)Basin,northwestern China.In this study,we use the time series analysis to identify the periods of Milankovitch orbital cycles in the Gamma-ray curve of this super-thick(124.85 m)coal and then use the obtained cycle periods of 405 ka,173 ka,44 ka,37.6 ka,22.5 ka to calculate the timeframe of the coalforming peatlands which ranges from 2703.44 to 2975.11 ka.Considering that the carbon content of the coal seam is 78.32%and the carbon loss during the coalification is about 25.80%,the carbon accumulation rate of the targeted coal seam is estimated to be 58.47-64.34 g C/m^(2)·a,and the NPP is estimated to be252.28-277.63 g C/m^(2)·a.The main palaeoenvironmental factors controlling the NPP of peatlands are CO_2content,palaeolatitude and palaeotemperature.The reduced NPP values of the palaeo-peatlands in the Shaerhu coalfield can be attributed to the mid-palaeolatitude and/or too low atmospheric CO_2contents.To a certain extent,the NPP of palaeo-peatlands reflects the changes in atmospheric CO_2,which can further reveal the dynamic response of the global carbon cycle to climate change.Therefore,predicting the level of NPP in the Middle Jurassic and studying the final destination of carbon in the ecosystem are beneficial to understanding the coal-forming process and palaeoenvironment.
基金Supported by the China National Science and Technology Major Project(2016ZX05012-002).
文摘To improve the oil recovery and economic efficiency in heavy oil reservoirs in late steam flooding,taking J6 Block of Xinjiang Oilfield as the research object,3D physical modeling experiments of steam flooding,CO2-foam assisted steam flooding,and CO2 assisted steam flooding under different perforation conditions are conducted,and CO2-assisted steam flooding is proposed for reservoirs in the late stage of steam flooding.The experimental results show that after adjusting the perforation in late steam flooding,the CO2 assisted steam flooding formed a lateral expansion of the steam chamber in the middle and lower parts of the injection well and a development mode for the production of overriding gravity oil drainage in the top chamber of the production well;high temperature water,oil,and CO2 formed stable low-viscosity quasi-single-phase emulsified fluid;and CO2 acted as a thermal insulation in the steam chamber at the top,reduced the steam partial pressure inside the steam chamber,and effectively improved the heat efficiency of injected steam.Based on the three-dimensional physical experiments and the developed situation of the J6 block in Xinjiang Oilfield,the CO2 assisted steam flooding for the J6 block was designed.The application showed that the CO2 assisted steam flooding made the oil vapor ratio increase from 0.12 to 0.16 by 34.0%,the oil recovery increase from 16.1%to 21.5%,and the final oil recovery goes up to 66.5%compared to steam flooding after perforation adjustment.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 29973023) the State Key Laboratory of Oil & Gas Reservoir Geology and Exploitation ofSouthwest Petroleum Institute+1 种基金 Nanchang China.
文摘The growth and structure of anionic micelles of sodium dodecyl trioxyethylene sulfate (AES) in the presence of multivalent counterion Al3+ were investigated by means of dynamic rheological methods. It has been obtained by themeasurements of shear viscosity, complex viscosity anddynamic moduli, as well as the application of Cox-Merz rule and Cole-Cole plot that wormlike micelle and networkstructure could be formed in AES/AlCl3 aqueous solutions. The structure was of a character of nonlinear viscoelasticfluid and departure from the simple Maxwell model. Thetechnique of freeze-fracture transmission electronmicroscopy (FF-TEM) was also used to confirm theformation of this interesting structure.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05046-001).
文摘The secondary migration mechanism,enrichment factors of Jurassic tight oil in central Sichuan Basin were well investigated through physical simulation experiment of reservoir formation,casting and fluorescent thin sections,field emission scanning electron microscope(FESEM)and environment scanning electron microscope(ESEM).The results show that migration of Jurassic tight oil in central Sichuan Basin is a low-velocity non-Darcy flow through low-efficient migration path under the huge migration driving force,and has three migration and seepage stages,i.e.viscous flow stage,nonlinear seepage stage,and quasi-liner seepage stage.Microscopically,the migration pathway of tight oil is the porefracture composite conduction;macroscopically,the migration mode of tight oil is the large-scale shortedistance migration.Distribution of favorable zones of tight oil is controlled by distribution of high-quality source rocks.The hydrocarbon-generation strength of 0.4106 t/km2 can be as a threshold to determine favorable zone of tight oil in the study area.The reservoirs with high permeability and high porosity can form tight oil sweet spots,and the development degree of fractures is closely related to well with high yield of tight oil well.
基金This work was suppor ted by National Science and Technology Major Project of China(Grant No.2011ZX05044,2011ZX05001)National Key Basic Research Program(973 Program)of China(2014CB239003).
文摘Efficient large-scale development of ultra-low-permeability reservoirs(0.3-1 mD)has been achieved in the Changqing Oilfield,Ordos Basin of China.According to unique features of petroleum exploration and development in this basin,tight oil herein refers to petroleum that occurs in oil-bearing shales and interbedded tight sandstone reservoirs adjacent to source rocks with ambient air permeability<0.3 mD.Tight oil in tight sandstone and shale have generally not yet experienced large-scale long-distance migration.In the Yanchang Formation,tight oil has mainly accumulated in the semi-deep to deep lacustrine facies,typically in oil-bearing shales and tight sandstones of the 7th member oil-bearing formation and tight sandstones of the 6th member oil-bearing formation in the center of the basin.Tight oil resource in the Ordos Basin is characterized by wide spatial distribution,excellent source rocks,extremely tight sandstone reservoirs,complex pore throat structures,poor physical properties,high oil saturation,good crude-oil properties,and low reservoir pressure.A fundamental feature of the continuous oil and gas accumulation in tight oil reservoirs is the widespread development of nano-scale pore-throat systems.In the Yanchang Formation,most of connected pore throats in tight sandstone reservoirs have diameters greater than critical pore throat diameter,allowing oil and gas migration in the tight reservoirs.According to contact relationship between tight reservoirs and source rocks,three types of tight oil reservoirs are identified in the Yanchang Formation,i.e.,tight massive sandstone reservoir,sand-shale interbed reservoir,and oil-bearing shale reservoir.In the Ordos Basin,tight oil is widely distributed in the 6th and 7th members of the Yanchang Formation,with total resources estimated to be 3×10^(9) t.These include>1×10^(9) t of oil resources in shale in the 7th member of the Yanchang Formation and approximately 0.9×10^(9) t and 1.1×10^(9) t of tight sandstone oil resource in the 6th and 7th members of the Yanchang Formation,respectively.These tight oil resources are the realistic resources addition for the oilfield,which can ensure an annual production of 50×10^(6) t of oil and gas equivalent and maintain long-term stable oil production in the Changqing Oilfield,Ordos Basin,China.
文摘Water-sensitivity is a factor that must be paid attention to in the reservoir development stage of oil and gas fields.As a clastic reservoir,the water effect of Ahe formation in the northern structural belt of Kuqa is strong as a whole,but the mechanism analysis of medium and strong water-sensitivity effect is restricted by the evaluation method with permeability damage rate as the main parameter.Taking the shape of water-sensitivity test curve as the starting point,combined with the analysis of microscopic pore throat and clay minerals,the difference of permeability change rate measured by samples is characterized.The strong to medium water-sensitivity effects in the study layer are divided into three types:The permeability gradually decreases in the early stage-the rapid decrease in the late stage,the continuous decrease in the permeability,and the rapid decrease in the early stage-the slow decrease in the later stage.As awidely developed reservoir space in the study section,the micropore not only has the characteristics of fine pore size and easy blockage,but also serves as the occurrence space of the main water-sensitive mineral illite-smectite mixed layer.Therefore,the change types of the above different water sensitivity test curves are mainly controlled by the difference of micropore content.When the micropore content is low,the permeability decreases slowly in the early stage and decreases rapidly in the later stage(type Ⅰ),while when the micropore content is high,the permeability decreases rapidly in the early stage and slowly decreases in the later stage(type Ⅱ),while when the micropore content is medium,the permeability decreases continuously,and there is no obvious rate change(type Ⅲ)before and after the micropore content.The results show that the structural characteristics and relative content differences of micropores in the samples are the internal mechanism of the difference of water sensitivity effect types.
