The Tongnan secondary negative structure in central Sichuan Basin has controls and influences on the structural framework and petroleum geological conditions in the Gaoshiti-Moxi area.To clarify the controls and influ...The Tongnan secondary negative structure in central Sichuan Basin has controls and influences on the structural framework and petroleum geological conditions in the Gaoshiti-Moxi area.To clarify the controls and influences,the deformation characteristics,structural attributes and evolution process of the Tongnan negative structure were investigated through a series of qualitative and quantitative methods such as balanced profile restoration,area-depth-strain(ADS)analysis,and structural geometric forward numerical simulation,after comprehensive structural interpretation of high-precision 3D seismic data.The results are obtained in three aspects.First,above and below the P/AnP(Permian/pre-Permian)unconformity,the Tongnan negative structure demonstrates vertical differential structural deformation.It experiences two stages of structural stacking and reworking:extensional depression(from the Sinian Dengying Formation to the Permian),and compressional syncline deformation(after the Jurassic).The multi-phase trishear deformation of the preexisting deep normal faults dominated the extensional depression.The primary depression episodes occurred in the periods from the end of Late Proterozoic to the deposition of the 1st–2nd members of the Dengying Formation,and from the deposition of Lower Cambrian Longwangmiao Formation–Middle–Upper Cambrian until the Ordovician.Second,the multi-stage evolution process of the Tongnan negative structure controlled the oil and gas migration and adjustment and present-day differential gas and water distribution between the Tongnan negative structure and the Gaoshiti and Moxi-Longnüsi structural highs.Third,the Ordovician,which is limitedly distributed in the Tongnan negative structure and is truncated by the P/AnP unconformity on the top,has basic geological conditions for the formation of weathering karst carbonate reservoirs.It is a new petroleum target deserving attention.展开更多
Vertical differential structural deformation(VDSD),one of the most significant structural characteristics of strike-slip fault zones(SSFZs)in the Shunbei area,is crucial for understanding deformation in the SSFZ and i...Vertical differential structural deformation(VDSD),one of the most significant structural characteristics of strike-slip fault zones(SSFZs)in the Shunbei area,is crucial for understanding deformation in the SSFZ and its hydrocarbon accumulation significance.Based on drilling data and high-precision 3-D seismic data,we analyzed the geometric and kinematic characteristics of the SSFZs in the Shunbei area.Coupled with the stratification of the rock mechanism,the structural deformations of these SSFZs in different formations were differentiated and divided into four deformation layers.According to comprehensive structural interpretations and comparisons,three integrated 3-D structural models could describe the VDSD of these SSFZs.The time-space coupling of the material basis(rock mechanism stratification),changing dynamic conditions(e.g.,changing stress-strain states),and special deformation mechanism of the en echelon normal fault array uniformly controlled the formation of the VDSD in the SSFZs of the Shunbei area.The VDSD of the SSFZs in this area controlled the entire hydrocarbon accumulation process.Multi-stage structural superimposing deformation influenced the hydrocarbon migration,accumulation,distribution,preservation,and secondary adjustments.展开更多
The evolution of shale reservoirs is mainly related to two functions:mechanical compaction controlled by ground stress and chemical compaction controlled by thermal effect.Thermal simulation experiments were conducted...The evolution of shale reservoirs is mainly related to two functions:mechanical compaction controlled by ground stress and chemical compaction controlled by thermal effect.Thermal simulation experiments were conducted to simulate the chemical compaction of marine-continental transitional shale,and X-ray diffraction(XRD),CO2 adsorption,N2 adsorption and high-pressure mercury injection(MIP)were then used to characterize shale diagenesis and porosity.Moreover,simulations of mechanical compaction adhering to mathematical models were performed,and a shale compaction model was proposed considering clay content and kaolinite proportions.The advantage of this model is that the change in shale compressibility,which is caused by the transformation of clay minerals during thermal evolution,may be considered.The combination of the thermal simulation and compaction model may depict the interactions between chemical and mechanical compaction.Such interactions may then express the pore evolution of shale in actual conditions of formation.Accordingly,the obtained results demonstrated that shales having low kaolinite possess higher porosity at the same burial depth and clay mineral content,proving that other clay minerals such as illite-smectite mixed layers(I/S)and illite are conducive to the development of pores.Shales possessing a high clay mineral content have a higher porosity in shallow layers(<3500 m)and a lower porosity in deep layers(>3500 m).Both the amount and location of the increase in porosity differ at different geothermal gradients.High geothermal gradients favor the preservation of high porosity in shale at an appropriate Ro.The pore evolution of the marine-continental transitional shale is divided into five stages.Stage 2 possesses an Ro of 1.0%-1.6%and has high porosity along with a high specific surface area.Stage 3 has an Ro of 1.6%-2.0%and contains a higher porosity with a low specific surface area.Finally,Stage 4 has an Ro of 2.0%-2.9%with a low porosity and high specific surface area.展开更多
Methanogens and sulfate reducing bacteria were detected by the 16SrRNA sequencing of coalbed methane(CBM)co-produced water in the south of the Qinshui Basin,which is indicative of the presence of secondary biological ...Methanogens and sulfate reducing bacteria were detected by the 16SrRNA sequencing of coalbed methane(CBM)co-produced water in the south of the Qinshui Basin,which is indicative of the presence of secondary biological gas in the south of this basin,in contradiction to the previous understanding of thermogenic gas.This work systematically collected water samples from the CBM wells in the Shizhuangnan Block and analyzed the microbial geochemical characteristics from the aspects of water ions,hydrogen and oxygen isotopes,dissolved inorganic carbon and microbial diversity.It is shown that the Shizhuangnan Block has a nearly SN-trending monoclinic structure,and the elevation of coal seam decreases gradually from the east to west.Because of the water blocking effect of Sitou fault in the west,the precipitation flowed from the east to west,and gradually transited to stagnant flow area.The concentration variation of some ions such as Na^+,K^+,Ca2^+,Mg2^+,Cl^-,HCO3^-and total dissolved solids(TDS)suggest the variation of redox condition in the coal reservoir water.The 16SrDNA sequencing analysis of the collected water samples detected the presence of methanogens and sulfate reduction bacteria.The presence of methane production zone and sulfate methane transition zone(SMTZ)was identified.The effect of methanogens in the methane production zone leads to an increase in the methane concentration,resulting in a high gas content in the study area.In the SMTZ,most methane is consumed by anaerobic oxidation due to high sulfate concentrations.展开更多
Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quatern...Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials,very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescentshaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in Si O_2, Na_2 O, and Mg O relative to the sand dam sediment in the lakeshore.Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.展开更多
In long-term water drive reservoir, small dose and short radius profile control cannot meet the needs, so deep profile control and flooding are needed. During the placement and processing of conventional deep profile ...In long-term water drive reservoir, small dose and short radius profile control cannot meet the needs, so deep profile control and flooding are needed. During the placement and processing of conventional deep profile control and flooding agent, the zone classification formed by the changes of pressure field and fluid field are not taken into account. In order to better develop these reservoirs, we proposed a novel deep profile control method, that is, the iso-pressure drop gradient progressive deep profile control method. The key features of the method include: 1) the method took into account the reservoir pressure distribution;2) it proposed a novel standard to divide the orders of zone;3) the method has been successfully applied in 4 wells in China Oilfield. The method divided the formation into near wellbore zone, well-far zone and deep zone according to the drawdown curve. As each zone of the pressure gradient is different and therefore require different intensity of slug. Then design the agent slugs according to iso-pressure drop gradient rule, and the breakthrough pressure gradient of agent is equal to the formation pressure gradient, and it achieved the fluid diversion of whole course by combining the different intensity of blocking agent. The method was applied successfully in 2 wells in China Oilfield from May to November in 2008. The method can smartly improve the sweep efficiency, and field test shows that it can play a very good efficiency of reducing water and increasing oil production. This method is becoming more of a concern in the oilfield develop.展开更多
The Silurian stratigraphic sequence has recently become one of the most important exploration targets in the Tarim Basin, with a considerable amount of profitable hydrocarbon pools discovered in the central Tarim Basi...The Silurian stratigraphic sequence has recently become one of the most important exploration targets in the Tarim Basin, with a considerable amount of profitable hydrocarbon pools discovered in the central Tarim Basin. Previous exploration activities indicate that the Silurian stratigraphic sequence in the eastern Tarim Basin has great hydrocarbon exploration potential. The Silurian reservoirs comprise a set of tight marine sandstones, whose diagenetic sequence and genetic mechanism are still poorly understood. The complex relationship of hydrocarbon generation, the timing of the peak expulsion of the source rocks and the evolution of the reservoirs remains unclear. An integrated description and analysis have been carried out on core samples from eleven wells selected from the eastern Tarim Basin. A range of petrographic and geochemical analyses were conducted. By using an integrated approach with thin-section petrography, scanning electron microscopy(SEM), cathodoluminescence(CL), carbon and oxygen isotope geochemistry, formation water analysis, X-ray diffractometry(XRD), electron probe microanalysis and fluid inclusion microthermometry, the genesis and occurrence of individual diagenetic events were documented to reconstruct the diagenetic sequence and diagenetic model for the Silurian sandstone. Additionally, the tight nature of the Silurian reservoirs can mainly be attributed to the compaction processes and cementation. In particular, the destructiveness of the compactional processes to the original porosity is far greater than that from the cementation. Furthermore, fluid inclusion analyses also indicate that the Silurian sandstone has experienced three phases of hydrocarbon charge. The first two phases occurred during the eodiagenesis stage(from the Late Silurian to the Early Devonian and from the Late Carboniferous to the end of the Late Permian), when the Silurian sandstone was not tight and had a porosity of greater than 20%. The third phase occurred during the stage B of mesodiagenesis(since the Late Cretaceous), when the Silurian sandstone was fully tight.展开更多
Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wetta...Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.展开更多
Many studies have focused on the Cretaceous evolution of NE China,including the 973 Scientific Exploration Well Work program,which completed two drill holes in this area.The Cretaceous Basin Group of eastern NE China ...Many studies have focused on the Cretaceous evolution of NE China,including the 973 Scientific Exploration Well Work program,which completed two drill holes in this area.The Cretaceous Basin Group of eastern NE China is highly altered,so the evolution,controlling factors and interpretation of the Early Cretaceous Dasanjiang Basin are controversial,and fundamental aspects of the rocks are poorly understood.The Boli Basin is the largest Cretaceous basin within NE China,but the temporal and spatial extent of Mesozoic strata within this basin,especially the Dongshan Formation,arc not well-known.展开更多
The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian ...The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian Series in the Tarim Craton has not yet been established due to the scarcity of fossils and the absence of the Steptoean Positive Carbon Isotope Excursion(SPICE),which is the primary global carbon isotope excursion of the Furongian Series.In this study,the SPICE was discovered by examining the carbon isotopes of the representative drilling wells in the West Platform and East Basin.A positive carbon isotope anomaly withδ13C values ranging from 1.5‰to 1.9‰(PDB),were found in the middle of the Xiaqiulitag Formation of the three drilling wells in the West Platform,and a positive excursion withδ13C values up to 4.0‰(PDB),which is correlated with the SPICE,was found in the lower limestone of the Tuershaketag Formation in the East Basin.Based on the carbon isotopic data and chemostratigraphic correlation,the chronostratigraphic framework of the Furongian Series across different facies in the Tarim Craton is preliminarily established.The basal boundary of the Furongian Series was preliminarily defined by the occurrence of the SPICE.Aweak positive anomaly ofδ13C was observed at the base of the Penglaiba Formation of the three boreholes in the West Platform and the top of the Tuershaketag Formation of Tadong-2 well.We propose that the positive anomaly of the carbon isotope above the weak negative anomaly at the base of the Penglaiba Formation and the top of the Tuershaketag Formation can be used to define the Cambrian-Ordovician boundary in the Tarim Craton.展开更多
Quartz is an important mineral component in the Late Ordovician–Early Silurian Wufeng-Longmaxi Formation with various forms and sources and has a significant impact on the properties of shale gas reservoirs.In this s...Quartz is an important mineral component in the Late Ordovician–Early Silurian Wufeng-Longmaxi Formation with various forms and sources and has a significant impact on the properties of shale gas reservoirs.In this study,geochemical analysis,scanning electron microscopy(SEM)observation,and rock mechanics testing were performed on shale samples from the Wufeng-Longmaxi Formation in north-western Hunan,South China.Quartz is classified into four types based on morphological features and cathodoluminescence(CL)images under SEM–terrigenous detrital quartz,quartz overgrowths,biogenic skeletal quartz and microquartz.The quartz in Upper Longmaxi Formation is predominantly of terrigenous origin and contains a small amount of quartz formed by clay transformation.The quartz in the Wufeng-Lower Longmaxi Formation is predominantly biogenic.The biogenic quartz has a direct effect on organic matter(OM)abundance,pore structure and brittleness.It is indicated by the positive correlation with TOC content and biogenic Ba content that biogenic quartz-rich strata have high paleoproductivity.The rigid frameworks formed by biogenic quartz during the early diagenesis stage facilitated the preservation of the primary pores.The interparticle pores of biogenic quartz are the space for OM preservation and migration,creating conditions for the development of OM pores.Additionally,the calculated brittleness index(BI)shows a positive correlation with biogenic quartz content,indicating that layers rich in biogenic quartz are more conducive to fracture.Therefore,the Wufeng-Lower Longmaxi Formation has higher OM content,porosity and represents a more favorable exploration and development target.展开更多
Abundant unminable coal in deep strata and abandoned mines are also precious sources of clean gas energy,under which biotransformation is a potential path.In recent years,substantial progress has been made in laborato...Abundant unminable coal in deep strata and abandoned mines are also precious sources of clean gas energy,under which biotransformation is a potential path.In recent years,substantial progress has been made in laboratory research on coal degradation to produce methane by microbial metabolism.This paper systematically reviews the research progress of microbial enhancement and microbial stimulation of coal,physicochemical pretreatments of coal,and environmental factors affecting coal biotransformation.The research idea of coal biotransformation should aim at field production increase and gradually clarify the microbial mechanism of coal degradation and the regional distribution and functional composition of microbial communities on the block scale.The research on coal biotransformation helps improve the development level of coalbed methane and the sustainable development of unconventional natural gas resources.展开更多
基金Supported by the National Natural Science Foundation of China(U19B6003-01).
文摘The Tongnan secondary negative structure in central Sichuan Basin has controls and influences on the structural framework and petroleum geological conditions in the Gaoshiti-Moxi area.To clarify the controls and influences,the deformation characteristics,structural attributes and evolution process of the Tongnan negative structure were investigated through a series of qualitative and quantitative methods such as balanced profile restoration,area-depth-strain(ADS)analysis,and structural geometric forward numerical simulation,after comprehensive structural interpretation of high-precision 3D seismic data.The results are obtained in three aspects.First,above and below the P/AnP(Permian/pre-Permian)unconformity,the Tongnan negative structure demonstrates vertical differential structural deformation.It experiences two stages of structural stacking and reworking:extensional depression(from the Sinian Dengying Formation to the Permian),and compressional syncline deformation(after the Jurassic).The multi-phase trishear deformation of the preexisting deep normal faults dominated the extensional depression.The primary depression episodes occurred in the periods from the end of Late Proterozoic to the deposition of the 1st–2nd members of the Dengying Formation,and from the deposition of Lower Cambrian Longwangmiao Formation–Middle–Upper Cambrian until the Ordovician.Second,the multi-stage evolution process of the Tongnan negative structure controlled the oil and gas migration and adjustment and present-day differential gas and water distribution between the Tongnan negative structure and the Gaoshiti and Moxi-Longnüsi structural highs.Third,the Ordovician,which is limitedly distributed in the Tongnan negative structure and is truncated by the P/AnP unconformity on the top,has basic geological conditions for the formation of weathering karst carbonate reservoirs.It is a new petroleum target deserving attention.
基金financially supported by the China Petroleum&Chemical Corporation(SINOPEC)(Grant No.P18047-2)the National Natural Science Foundation of China(Grant No.U19B6003-01)the National Key Research and Development Program of China(Grant No.2017YFC0601405)。
文摘Vertical differential structural deformation(VDSD),one of the most significant structural characteristics of strike-slip fault zones(SSFZs)in the Shunbei area,is crucial for understanding deformation in the SSFZ and its hydrocarbon accumulation significance.Based on drilling data and high-precision 3-D seismic data,we analyzed the geometric and kinematic characteristics of the SSFZs in the Shunbei area.Coupled with the stratification of the rock mechanism,the structural deformations of these SSFZs in different formations were differentiated and divided into four deformation layers.According to comprehensive structural interpretations and comparisons,three integrated 3-D structural models could describe the VDSD of these SSFZs.The time-space coupling of the material basis(rock mechanism stratification),changing dynamic conditions(e.g.,changing stress-strain states),and special deformation mechanism of the en echelon normal fault array uniformly controlled the formation of the VDSD in the SSFZs of the Shunbei area.The VDSD of the SSFZs in this area controlled the entire hydrocarbon accumulation process.Multi-stage structural superimposing deformation influenced the hydrocarbon migration,accumulation,distribution,preservation,and secondary adjustments.
文摘The evolution of shale reservoirs is mainly related to two functions:mechanical compaction controlled by ground stress and chemical compaction controlled by thermal effect.Thermal simulation experiments were conducted to simulate the chemical compaction of marine-continental transitional shale,and X-ray diffraction(XRD),CO2 adsorption,N2 adsorption and high-pressure mercury injection(MIP)were then used to characterize shale diagenesis and porosity.Moreover,simulations of mechanical compaction adhering to mathematical models were performed,and a shale compaction model was proposed considering clay content and kaolinite proportions.The advantage of this model is that the change in shale compressibility,which is caused by the transformation of clay minerals during thermal evolution,may be considered.The combination of the thermal simulation and compaction model may depict the interactions between chemical and mechanical compaction.Such interactions may then express the pore evolution of shale in actual conditions of formation.Accordingly,the obtained results demonstrated that shales having low kaolinite possess higher porosity at the same burial depth and clay mineral content,proving that other clay minerals such as illite-smectite mixed layers(I/S)and illite are conducive to the development of pores.Shales possessing a high clay mineral content have a higher porosity in shallow layers(<3500 m)and a lower porosity in deep layers(>3500 m).Both the amount and location of the increase in porosity differ at different geothermal gradients.High geothermal gradients favor the preservation of high porosity in shale at an appropriate Ro.The pore evolution of the marine-continental transitional shale is divided into five stages.Stage 2 possesses an Ro of 1.0%-1.6%and has high porosity along with a high specific surface area.Stage 3 has an Ro of 1.6%-2.0%and contains a higher porosity with a low specific surface area.Finally,Stage 4 has an Ro of 2.0%-2.9%with a low porosity and high specific surface area.
基金granted by the National Science and Technology Major Project of China (grant No. 2017ZX05064003)the National Natural Science Foundation of China (grant No. 41772159/D0208)the Fundamental Research Funds for the Central Universities (grant No. 2652018233)
文摘Methanogens and sulfate reducing bacteria were detected by the 16SrRNA sequencing of coalbed methane(CBM)co-produced water in the south of the Qinshui Basin,which is indicative of the presence of secondary biological gas in the south of this basin,in contradiction to the previous understanding of thermogenic gas.This work systematically collected water samples from the CBM wells in the Shizhuangnan Block and analyzed the microbial geochemical characteristics from the aspects of water ions,hydrogen and oxygen isotopes,dissolved inorganic carbon and microbial diversity.It is shown that the Shizhuangnan Block has a nearly SN-trending monoclinic structure,and the elevation of coal seam decreases gradually from the east to west.Because of the water blocking effect of Sitou fault in the west,the precipitation flowed from the east to west,and gradually transited to stagnant flow area.The concentration variation of some ions such as Na^+,K^+,Ca2^+,Mg2^+,Cl^-,HCO3^-and total dissolved solids(TDS)suggest the variation of redox condition in the coal reservoir water.The 16SrDNA sequencing analysis of the collected water samples detected the presence of methanogens and sulfate reduction bacteria.The presence of methane production zone and sulfate methane transition zone(SMTZ)was identified.The effect of methanogens in the methane production zone leads to an increase in the methane concentration,resulting in a high gas content in the study area.In the SMTZ,most methane is consumed by anaerobic oxidation due to high sulfate concentrations.
基金funding support from the Qinghai Oilfield Company of the China National Petroleum Corporation
文摘Influenced by neo-tectonic movement, the Sanhu area of China's Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials,very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescentshaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in Si O_2, Na_2 O, and Mg O relative to the sand dam sediment in the lakeshore.Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.
文摘In long-term water drive reservoir, small dose and short radius profile control cannot meet the needs, so deep profile control and flooding are needed. During the placement and processing of conventional deep profile control and flooding agent, the zone classification formed by the changes of pressure field and fluid field are not taken into account. In order to better develop these reservoirs, we proposed a novel deep profile control method, that is, the iso-pressure drop gradient progressive deep profile control method. The key features of the method include: 1) the method took into account the reservoir pressure distribution;2) it proposed a novel standard to divide the orders of zone;3) the method has been successfully applied in 4 wells in China Oilfield. The method divided the formation into near wellbore zone, well-far zone and deep zone according to the drawdown curve. As each zone of the pressure gradient is different and therefore require different intensity of slug. Then design the agent slugs according to iso-pressure drop gradient rule, and the breakthrough pressure gradient of agent is equal to the formation pressure gradient, and it achieved the fluid diversion of whole course by combining the different intensity of blocking agent. The method was applied successfully in 2 wells in China Oilfield from May to November in 2008. The method can smartly improve the sweep efficiency, and field test shows that it can play a very good efficiency of reducing water and increasing oil production. This method is becoming more of a concern in the oilfield develop.
基金supported by the China National Science and Technology Major Project (No. 2011ZX05009-002)
文摘The Silurian stratigraphic sequence has recently become one of the most important exploration targets in the Tarim Basin, with a considerable amount of profitable hydrocarbon pools discovered in the central Tarim Basin. Previous exploration activities indicate that the Silurian stratigraphic sequence in the eastern Tarim Basin has great hydrocarbon exploration potential. The Silurian reservoirs comprise a set of tight marine sandstones, whose diagenetic sequence and genetic mechanism are still poorly understood. The complex relationship of hydrocarbon generation, the timing of the peak expulsion of the source rocks and the evolution of the reservoirs remains unclear. An integrated description and analysis have been carried out on core samples from eleven wells selected from the eastern Tarim Basin. A range of petrographic and geochemical analyses were conducted. By using an integrated approach with thin-section petrography, scanning electron microscopy(SEM), cathodoluminescence(CL), carbon and oxygen isotope geochemistry, formation water analysis, X-ray diffractometry(XRD), electron probe microanalysis and fluid inclusion microthermometry, the genesis and occurrence of individual diagenetic events were documented to reconstruct the diagenetic sequence and diagenetic model for the Silurian sandstone. Additionally, the tight nature of the Silurian reservoirs can mainly be attributed to the compaction processes and cementation. In particular, the destructiveness of the compactional processes to the original porosity is far greater than that from the cementation. Furthermore, fluid inclusion analyses also indicate that the Silurian sandstone has experienced three phases of hydrocarbon charge. The first two phases occurred during the eodiagenesis stage(from the Late Silurian to the Early Devonian and from the Late Carboniferous to the end of the Late Permian), when the Silurian sandstone was not tight and had a porosity of greater than 20%. The third phase occurred during the stage B of mesodiagenesis(since the Late Cretaceous), when the Silurian sandstone was fully tight.
文摘Hydraulic fracturing technique is widely used for methane drainage and has achieved good effects in numerous coal mines,but negative effects may occur as the fracturing fluids are absorbed into the coal seam.Gas wettability alteration(GWA)technology can be used as it can enhance the gas and water mobility during dewatering process as a result of capillary pressure change.However,there have been few reported field tests in coal mines using GWA technology.This paper describes a pilot-scale field test in Xinjing coal mine,Yangquan,China.The fluorocarbon surfactants perfluorooctyl methacrylate monomer-containing polymethacrylate(PMP)was used to alter the wettability of coal seam to strong gas-wetness during the hydraulic fracturing process.The study focuses on the comparison of two boreholes(Boreholes#9 and#10)and one other borehole(Borehole#8)with and without using GWA approach.A well-defined monitoring program was established by measuring the dewatering volume of the fracturing fluid and the drainage volume of methane as well as the concentration.The field test results showed that the average methane drainage rates of Boreholes#9(39.28 m^(3)/d)and#10(51.04 m^(3)/d)with GWA treatment exceeded that of Borehole#8(21.09 m^(3)/d)without GWA treatment,with an increase of 86.3%and 142.1%,respectively.The average methane concentrations of Boreholes#9(4.05%)and#10(6.18%)were 64.6%and 151.2%higher than that of Borehole#8(2.46%),respectively.On the other hand,the dewatering ratio of Boreholes#9(4.36%)and#10(3.11%)was almost 19 times and 13 times greater than that of Borehole#8(0.22%).These field test results were in agreement with the experimental data.The significant increase in both methane concentration and dewatering ratio demonstrated that GWA technology could be applied for enhanced methane drainage in coal mines.Important lessons learned at Xinjing coal mine might be applied to other coal mines in China and elsewhere.
基金the National Natural Science Foundation(grant no.41472173)the Ministry of Land and Resources Outstanding Youth Science and Technology Talent Training Program of China(grant no.201311111)the National Oil Shale Geological Survey and Evaluation Program(grant no.dkyd201908-02).
文摘Many studies have focused on the Cretaceous evolution of NE China,including the 973 Scientific Exploration Well Work program,which completed two drill holes in this area.The Cretaceous Basin Group of eastern NE China is highly altered,so the evolution,controlling factors and interpretation of the Early Cretaceous Dasanjiang Basin are controversial,and fundamental aspects of the rocks are poorly understood.The Boli Basin is the largest Cretaceous basin within NE China,but the temporal and spatial extent of Mesozoic strata within this basin,especially the Dongshan Formation,arc not well-known.
基金supported by the National Science and Technology Major Project(Grant Nos.2016ZX05004-004&2017ZX05008-005)。
文摘The Furongian Series of the Cambrian in the Tarim Craton(NW China)is mainly composed of crystalline dolostones,and is an important target for oil and gas exploration.The chronostratigraphic framework of the Furongian Series in the Tarim Craton has not yet been established due to the scarcity of fossils and the absence of the Steptoean Positive Carbon Isotope Excursion(SPICE),which is the primary global carbon isotope excursion of the Furongian Series.In this study,the SPICE was discovered by examining the carbon isotopes of the representative drilling wells in the West Platform and East Basin.A positive carbon isotope anomaly withδ13C values ranging from 1.5‰to 1.9‰(PDB),were found in the middle of the Xiaqiulitag Formation of the three drilling wells in the West Platform,and a positive excursion withδ13C values up to 4.0‰(PDB),which is correlated with the SPICE,was found in the lower limestone of the Tuershaketag Formation in the East Basin.Based on the carbon isotopic data and chemostratigraphic correlation,the chronostratigraphic framework of the Furongian Series across different facies in the Tarim Craton is preliminarily established.The basal boundary of the Furongian Series was preliminarily defined by the occurrence of the SPICE.Aweak positive anomaly ofδ13C was observed at the base of the Penglaiba Formation of the three boreholes in the West Platform and the top of the Tuershaketag Formation of Tadong-2 well.We propose that the positive anomaly of the carbon isotope above the weak negative anomaly at the base of the Penglaiba Formation and the top of the Tuershaketag Formation can be used to define the Cambrian-Ordovician boundary in the Tarim Craton.
基金This study was financially supported by the National Science and Technology Major Project of China(No.2017ZX05035).
文摘Quartz is an important mineral component in the Late Ordovician–Early Silurian Wufeng-Longmaxi Formation with various forms and sources and has a significant impact on the properties of shale gas reservoirs.In this study,geochemical analysis,scanning electron microscopy(SEM)observation,and rock mechanics testing were performed on shale samples from the Wufeng-Longmaxi Formation in north-western Hunan,South China.Quartz is classified into four types based on morphological features and cathodoluminescence(CL)images under SEM–terrigenous detrital quartz,quartz overgrowths,biogenic skeletal quartz and microquartz.The quartz in Upper Longmaxi Formation is predominantly of terrigenous origin and contains a small amount of quartz formed by clay transformation.The quartz in the Wufeng-Lower Longmaxi Formation is predominantly biogenic.The biogenic quartz has a direct effect on organic matter(OM)abundance,pore structure and brittleness.It is indicated by the positive correlation with TOC content and biogenic Ba content that biogenic quartz-rich strata have high paleoproductivity.The rigid frameworks formed by biogenic quartz during the early diagenesis stage facilitated the preservation of the primary pores.The interparticle pores of biogenic quartz are the space for OM preservation and migration,creating conditions for the development of OM pores.Additionally,the calculated brittleness index(BI)shows a positive correlation with biogenic quartz content,indicating that layers rich in biogenic quartz are more conducive to fracture.Therefore,the Wufeng-Lower Longmaxi Formation has higher OM content,porosity and represents a more favorable exploration and development target.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.42102216 and 41972173)the NSFC-Shanxi Coal-based Low Carbon Joint Fund of China(No.U1910205)+2 种基金the Scientific Research Foundation for Young Teachers of Anhui University of Science and Technology(No.XCZX2021-04)the University-level key projects of Anhui University of science and technology(No.xjzd2020-05)the Scientific Research Foundation for High-level Talents of Anhui University of Science and Technology。
文摘Abundant unminable coal in deep strata and abandoned mines are also precious sources of clean gas energy,under which biotransformation is a potential path.In recent years,substantial progress has been made in laboratory research on coal degradation to produce methane by microbial metabolism.This paper systematically reviews the research progress of microbial enhancement and microbial stimulation of coal,physicochemical pretreatments of coal,and environmental factors affecting coal biotransformation.The research idea of coal biotransformation should aim at field production increase and gradually clarify the microbial mechanism of coal degradation and the regional distribution and functional composition of microbial communities on the block scale.The research on coal biotransformation helps improve the development level of coalbed methane and the sustainable development of unconventional natural gas resources.
