Carbonate rocks in the first member of the Middle Permian Maokou Formation in the Sichuan Basin(hereinafter“Mao 1 Member”for short)have been taken as a set of carbonate source rocks,and they have not been specifical...Carbonate rocks in the first member of the Middle Permian Maokou Formation in the Sichuan Basin(hereinafter“Mao 1 Member”for short)have been taken as a set of carbonate source rocks,and they have not been specifically studied from the aspects of reservoir evaluation and testing.By referring the exploration ideas of unconventional natural gas,the Mao 1 Member in Fuling area of southeastern Sichuan Basin has obtained industrial gas flow in development wells in recent years.In order to further clarify the natural gas exploration potential of the Mao 1 Member in this area,it is necessary to study its sedimentary characteristics,natural gas accumulation conditions and main control factors based on the data of field section measurement,systematic coring in drilling and laboratory testing.The following research results were obtained.First,the gas reservoir in the Mao 1 Member in the Fuling area is of sourceereservoir integration,and its natural gas ismainly enriched in blackish graymarlite and nodularmarlite.Second,its reservoir spaces are dominated by grainmargin pores(fractures),diagenetic shrinkage pores(fractures),organic pores and fractures.Third,the pores aremostly in nanometer scale,and the main pore diameter is in the range of 5-50 nm,which is between shale reservoir and conventional reservoir,with strong heterogeneity.Fourth,the gas reservoir is characterized by source-reservoir coexistence,lithology controlling reservoir and extensive layered distribution,presenting two-stage differential hydrocarbon enrichment,namely intraformational near-source enrichment in the early stage and interformational blowdown adjustment in the late stage.Fifth,the development of blackish gray organic-rich fine marlite which is deposited with the episodic upwelling in the outer ramp facies belt is the foundation for the natural gas accumulation,the transformation of clay minerals controls the development of higher-quality reservoirs,good preservation conditions are the key to the natural gas accumulation,and fracture development is favorable for the enrichment and high yield of natural gas.In conclusion,theMao 1Member in this area is a special type of gas reservoir,i.e.,carbonate source rock gas reservoir,which has greater potential of natural gas exploration and industrial gas flow have been obtained in several wells.The discovery of such type of gas reservoirs not only expands the domain of natural gas exploration in the Sichuan Basin,but provides the reference for the natural gas exploration in other areas of South China.展开更多
The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial...The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.展开更多
Well Taiye 1 in the Fuling area of the eastern Sichuan Basin has obtained a high-yield industrial gas flow(7.5×10^(4) m^(3)/d gas and 9.8 m^(3)/d oil)from the Middle Jurassic Lianggaoshan Formation,presenting a g...Well Taiye 1 in the Fuling area of the eastern Sichuan Basin has obtained a high-yield industrial gas flow(7.5×10^(4) m^(3)/d gas and 9.8 m^(3)/d oil)from the Middle Jurassic Lianggaoshan Formation,presenting a good test production effects,which means the realization of a major breakthrough in the exploration of Jurassic lacustrine shale oil and gas in the Sichuan Basin.In order to further determine the exploration potential of lacustrine shale oil and gas in this area and realize the large-scale efficient development and utilization of lacustrine shale oil and gas,this paper analyzes the geological conditions for the accumulation of lacustrine shale oil and gas in this area by using the drilling data of 10 key wells,such as wells Taiye 1 and Fuye 10.Then,the main factors controlling the enrichment of lacustrine shale oil and gas are discussed,and the exploration potential and favorable target zones of Jurassic lacustrine shale oil and gas in the Fuling area are defined.And the following research results are obtained.First,the quality Jurassic semi-deep lake shale in the Fuling area is characterized by high organic matter abundance,high porosity and high gas content,and it is the geological base of shale oil and gas enrichment.Second,the developed large wide and gentle syncline,good preservation condition and higher pressure coefficient(generally>1.2)are the key to the enrichment and high yield of shale oil and gas.Third,the developed microfractures in lacustrine shale are conducive to the enrichment and later fracturing of shale oil and gas.In conclusion,the Lianggaoshan Formation lacustrine shale in the Fuling area is widely distributed with moderate burial depth,developed microfractures and moderate thermal evolution,and its shale gas resource extent and shale oil resource extent are 1922×10^(8)m^(3)and 2800×10^(4)t,respectively,indicating greater potential of shale oil and gas exploration,so shale oil and gas is the important field of oil and gas reserves and production increase in this area in the following stage.展开更多
Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shal...Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shale gas development in China.Research shows shale gas has dynamic accumulations with early preservation and late reconstruction and proposes high-quality shale developed in deep-water shelf as the base and good preservation conditions as the key factor for shale gas accumulation.Key technologies and facilities were developed for geophysical survey of shale gas,design and optimization of shale gas development,drilling and completion of horizontal wells,and fracturing stimulation.As the first and largest shale gas field in China,the discovery and successful development of Fuling Shale Gas Filed has made China the first country to achieve large-scale development of shale gas after North America.By August 2017,Fuling Shale Gas Field had declared 6008.14×10^(8)m^(3) proven reserves,76.8×10^(8)m^(3) production capacity and 133.9×10^(8)m^(3) cumulative production.The construction of Fuling Shale Gas Field with high level,high speed and high quality has been a good example of shale gas development in China.Its successful experiences can be used to other fields and play an important role in optimizing energy structure and improving environment.展开更多
Statistical analysis of massive laboratory analytical data shows that for intervals in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Fuling area,Sichuan Basin,the total organic...Statistical analysis of massive laboratory analytical data shows that for intervals in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Fuling area,Sichuan Basin,the total organic carbon content is 0.55%-5.89%with an average of 2.54%,presenting a gradual increase trend from top to bottom.Based on whole-rock X-ray diffraction data,the content of clay minerals of the shale is 16.6%-62.8%with an average of 40.9%,gradually decreasing from top to bottom.The content of brittle minerals gradually increases from top to bottom,ranging from 37.2%to 83.4%with an average of 59.1%.Porosity is 1.17%-7.98%with an average of 4.61%through the helium injection method.The horizontal permeability is 0.002-335.209 mD with an average of 23.785 mD by the steady-state method.Massive analytical data from the high-pressure mercury injection method show the micropores are well developed in the shale,and mainly provide the primary specific surface area of pores,while the micropores,transitional pores and mesopores primarily contribute to permeability.The pore types were observed using SEM in combination with argon ion polishing technology.From top to bottom of the shale interval,the organic pores increase and the inorganic pores decrease.Gas desorption data show that the total gas content is 0.44-5.19 m^(3)/t with an average of 1.97 m^(3)/t,and gradually increase from top to bottom of the shale interval.The development of marine shale gas reservoir in Well A is controlled by mineral compositions,the development characteristics of organic matter.TOC is not only a major intrinsic factor controlling the lower reservoir interval,but also an important material to provide the reservoir space for the shale gas.In the late diagenetic stage,the clay mineral assemblages changed from montmorillonite to illite,forming new micropores and leading to an increase of the porosity and great influences on the upper reservoir interval.The content of brittle minerals is more than 50%,facilitating formation of fractures,and the permeability performance can be enhanced significantly.In general,the Wufeng Formation and the bottom interval of the Longmaxi Formation are both high-quality reservoirs and primary pay intervals.展开更多
In September 2013,the National Energy Administration approved the establishment of Fuling national shale gas demonstration area(hereinafter referred to as the demonstration area),whose construction was completed in De...In September 2013,the National Energy Administration approved the establishment of Fuling national shale gas demonstration area(hereinafter referred to as the demonstration area),whose construction was completed in December 2015.After nearly one decade of development,it has grown into the main shale gas production base in China.In order to speed up the integration and breakthrough of China's shale gas theoretical understanding and exploration and development technology and effectively promote the great development of marine shale gas in China,this paper reviews and summarizes the development and construction history of the demonstration area,geological theory understanding,engineering technology and key equipment progress.And based on this,the future development direction of the demonstration area is predicted.And the following research results are obtained.First,shale gas exploration and development in the demonstration area is divided into three stages,i.e.,exploration evaluation,phase I and II construction,and stacked development and adjustment.Second,the“binary enrichment”theory for marine shale gas and the engineering theory for efficiently developing gas reservoirs are innovatively established.Third,a series of supporting technologies are innovatively developed,such as optimized and fast drilling technology for shale gas cluster horizontal wells,differentiated network fracturing technology,high-efficiency gas production,gathering and transportation technology,and green development technology for karst mountains,and the localization of key equipment and tools is realized.Fourth,the efficient development of shallow overpressure shale gas reservoirs above 3500 m in depth and the effective development of shale gas reservoirs at the depth of 3500e4000 m are realized in the demonstration area.Fifth,the construction of the demonstration area in the future includes accelerating the development of normal-pressure deep shale gas,continuously tackling key shale gas EOR technologies,actively promoting the field application of new technologies and methods,and powerfully strengthening the construction of green demonstration areas.In conclusion,this demonstration area is the earliest one of four national shale gas demonstration areas,and its achievements will provide continuous guidance for the shale gas exploration and development in China and play a demonstrative and guiding role in promoting the development of shale gas geological theories and exploration and development technologies in China.展开更多
Bedding fractures are among the key factors affecting the production efficiency of shale oil and gas,but relatively little research has been conducted on the effectiveness of bedding fractures.Based on field outcrops ...Bedding fractures are among the key factors affecting the production efficiency of shale oil and gas,but relatively little research has been conducted on the effectiveness of bedding fractures.Based on field outcrops and drill cores from the Fuling area in the Sichuan Basin,this work discusses the development,filling,and opening characteristics of bedding fractures and their quantitative impact on physical properties.Multiple methods were employed,e.g.,immersion testing,wet illumination,high-power microscanning,imaging logging identification and experimental measurement.The results indicate that the highest density reaches 437 fractures per meter,with apertures less than 0.5µm being the majority.The average permeability of the shale samples with vertical bedding is 44.6 times that of the shale samples with parallel bedding,while the porosity exhibits less anisotropy.Many open bedding fractures with gas outlets in the core are shown by on-site immersion experiments and electron microscopy scanning experiments.Each dark stripe on the imaging logging map corresponds to a bedding fracture,and the thickness of the dark stripes corresponds to the aperture of the bedding fracture.There is no need to consider unfilled bedding fractures,as fractures filled with calcite veins and pyrite crystals can also become effective seepage channels because of the pores within the calcite veins and between the pyrite crystals.The utilization and transformation of bedding fractures during fracturing is one of the key steps in producing shale oil and gas.It is necessary to combine the in situ stress field,bedding fracture characteristics,and fracturability of shales to reasonably utilize bedding fractures to transform oil and gas reservoirs.展开更多
基金supported by the Special and Significant Project of National Science and Technology“Enrichment law and exploration evaluation methods of shale gas in key areas”(No.2017ZX05036001)Sinopec Major Science and Technology Project“Target evaluation and key exploration techniques for large marine gas fields in Sichuan Basin”(No.P16082).
文摘Carbonate rocks in the first member of the Middle Permian Maokou Formation in the Sichuan Basin(hereinafter“Mao 1 Member”for short)have been taken as a set of carbonate source rocks,and they have not been specifically studied from the aspects of reservoir evaluation and testing.By referring the exploration ideas of unconventional natural gas,the Mao 1 Member in Fuling area of southeastern Sichuan Basin has obtained industrial gas flow in development wells in recent years.In order to further clarify the natural gas exploration potential of the Mao 1 Member in this area,it is necessary to study its sedimentary characteristics,natural gas accumulation conditions and main control factors based on the data of field section measurement,systematic coring in drilling and laboratory testing.The following research results were obtained.First,the gas reservoir in the Mao 1 Member in the Fuling area is of sourceereservoir integration,and its natural gas ismainly enriched in blackish graymarlite and nodularmarlite.Second,its reservoir spaces are dominated by grainmargin pores(fractures),diagenetic shrinkage pores(fractures),organic pores and fractures.Third,the pores aremostly in nanometer scale,and the main pore diameter is in the range of 5-50 nm,which is between shale reservoir and conventional reservoir,with strong heterogeneity.Fourth,the gas reservoir is characterized by source-reservoir coexistence,lithology controlling reservoir and extensive layered distribution,presenting two-stage differential hydrocarbon enrichment,namely intraformational near-source enrichment in the early stage and interformational blowdown adjustment in the late stage.Fifth,the development of blackish gray organic-rich fine marlite which is deposited with the episodic upwelling in the outer ramp facies belt is the foundation for the natural gas accumulation,the transformation of clay minerals controls the development of higher-quality reservoirs,good preservation conditions are the key to the natural gas accumulation,and fracture development is favorable for the enrichment and high yield of natural gas.In conclusion,theMao 1Member in this area is a special type of gas reservoir,i.e.,carbonate source rock gas reservoir,which has greater potential of natural gas exploration and industrial gas flow have been obtained in several wells.The discovery of such type of gas reservoirs not only expands the domain of natural gas exploration in the Sichuan Basin,but provides the reference for the natural gas exploration in other areas of South China.
基金supported by the National Major Science and Technology Project“Hydrocarbon generation and expulsion mechanism of marine source strata and evaluation technology”(No.:2017ZX05005-001-003)the Science&Technology Project of Sinopec Exploration Company“Evaluation on hydrocarbon generation potential in Mao 1 Member,Fuling area”(No.:35450003-17-ZC0607-0032).
文摘The acidolysis gas in source rocks is the desorbed hydrocarbon gas in non-connected pores and carbonate crystal lattice,while the absorbed gas lies in the connected pores and is absorbed by surface.It is controversial about whether to use absorbed gas or acidolysis gas in gas source correlation.Using the absorbed gas and acidolysis gas in the first member of the Middle Permian Maokou Fm(hereinafter referred to as Mao 1 member)of Fuling area in the Sichuan Basin,the differences of components and carbon isotopes between absorbed gas and acidolysis gas and their applicable conditions in gas source correlation were discussed.The results show that:(1)there are larger differences of components and isotopes between absorbed gas and acidolysis gas.The absorbed gas has more heavy hydrocarbons and heavier carbon isotope.This difference can be attributed to the easier diffusion of methane and light hydrocarbons in absorbed gas,leading to relatively enriched heavy hydrocarbons and heavier carbon isotope in absorbed gas;(2)acidolysis gas is a mixture of hydrocarbon gas formed during different stages,while absorbed gas is the result of equilibrium between diffusion and supply of hydrocarbon gas,which can result in the differences on carbon isotope sequences between them;(3)the characteristics of natural gas produced after acid fracturing in the Mao 1 member in Fuling area resembles those of acidolysis gas in source rocks,while the characteristics of natural gas produced without acid fracturing are more similar to those of adsorbed gas;(4)the natural gas pool of the Mao 1 member is a carbonate gas pool with self-generation and self-storage.It is concluded that for the gas pool formed after migration,its producing pays have not been processed by acid fracturing,the produced gas should be correlated with the adsorbed gas in source rocks;for the carbonate gas pool with self-generation and self-storage,acid fracturing is usually needed,and the produced gas should be correlated with the acidolysis gas in source rocks.
基金Project supported by the National Major Science and Technology Project“Target Assessment and Exploration Technologies of Shale Gas Play”(No.:2017ZX05036)the Sinopec“Ten Major”Scientific and Technological Projects“Exploration and Evaluation Techniques of Jurassic Continental Shale Oil and Gas”(No.:P21078-1).
文摘Well Taiye 1 in the Fuling area of the eastern Sichuan Basin has obtained a high-yield industrial gas flow(7.5×10^(4) m^(3)/d gas and 9.8 m^(3)/d oil)from the Middle Jurassic Lianggaoshan Formation,presenting a good test production effects,which means the realization of a major breakthrough in the exploration of Jurassic lacustrine shale oil and gas in the Sichuan Basin.In order to further determine the exploration potential of lacustrine shale oil and gas in this area and realize the large-scale efficient development and utilization of lacustrine shale oil and gas,this paper analyzes the geological conditions for the accumulation of lacustrine shale oil and gas in this area by using the drilling data of 10 key wells,such as wells Taiye 1 and Fuye 10.Then,the main factors controlling the enrichment of lacustrine shale oil and gas are discussed,and the exploration potential and favorable target zones of Jurassic lacustrine shale oil and gas in the Fuling area are defined.And the following research results are obtained.First,the quality Jurassic semi-deep lake shale in the Fuling area is characterized by high organic matter abundance,high porosity and high gas content,and it is the geological base of shale oil and gas enrichment.Second,the developed large wide and gentle syncline,good preservation condition and higher pressure coefficient(generally>1.2)are the key to the enrichment and high yield of shale oil and gas.Third,the developed microfractures in lacustrine shale are conducive to the enrichment and later fracturing of shale oil and gas.In conclusion,the Lianggaoshan Formation lacustrine shale in the Fuling area is widely distributed with moderate burial depth,developed microfractures and moderate thermal evolution,and its shale gas resource extent and shale oil resource extent are 1922×10^(8)m^(3)and 2800×10^(4)t,respectively,indicating greater potential of shale oil and gas exploration,so shale oil and gas is the important field of oil and gas reserves and production increase in this area in the following stage.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05060).
文摘Although shale gas resources are abundant in China,commercial discoveries have not been made before the discovery of Fuling Shale Gas Field.SINOPEC has done lots of theoretical and technological studies on marine shale gas development in China.Research shows shale gas has dynamic accumulations with early preservation and late reconstruction and proposes high-quality shale developed in deep-water shelf as the base and good preservation conditions as the key factor for shale gas accumulation.Key technologies and facilities were developed for geophysical survey of shale gas,design and optimization of shale gas development,drilling and completion of horizontal wells,and fracturing stimulation.As the first and largest shale gas field in China,the discovery and successful development of Fuling Shale Gas Filed has made China the first country to achieve large-scale development of shale gas after North America.By August 2017,Fuling Shale Gas Field had declared 6008.14×10^(8)m^(3) proven reserves,76.8×10^(8)m^(3) production capacity and 133.9×10^(8)m^(3) cumulative production.The construction of Fuling Shale Gas Field with high level,high speed and high quality has been a good example of shale gas development in China.Its successful experiences can be used to other fields and play an important role in optimizing energy structure and improving environment.
基金This studywas jointly supported by the National Natural Science Foundation of China(No.41672134)the Programme of Introducing Talents of Scientific Disciplines to Universities(No.B14031)+1 种基金the 13th“Five-Year”Plan of the Ministry of Science and Technology of China(No.2016ZX05034002-003)the Shale Gas Survey of National Geological Survey(No.12120114055801).
文摘Statistical analysis of massive laboratory analytical data shows that for intervals in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Fuling area,Sichuan Basin,the total organic carbon content is 0.55%-5.89%with an average of 2.54%,presenting a gradual increase trend from top to bottom.Based on whole-rock X-ray diffraction data,the content of clay minerals of the shale is 16.6%-62.8%with an average of 40.9%,gradually decreasing from top to bottom.The content of brittle minerals gradually increases from top to bottom,ranging from 37.2%to 83.4%with an average of 59.1%.Porosity is 1.17%-7.98%with an average of 4.61%through the helium injection method.The horizontal permeability is 0.002-335.209 mD with an average of 23.785 mD by the steady-state method.Massive analytical data from the high-pressure mercury injection method show the micropores are well developed in the shale,and mainly provide the primary specific surface area of pores,while the micropores,transitional pores and mesopores primarily contribute to permeability.The pore types were observed using SEM in combination with argon ion polishing technology.From top to bottom of the shale interval,the organic pores increase and the inorganic pores decrease.Gas desorption data show that the total gas content is 0.44-5.19 m^(3)/t with an average of 1.97 m^(3)/t,and gradually increase from top to bottom of the shale interval.The development of marine shale gas reservoir in Well A is controlled by mineral compositions,the development characteristics of organic matter.TOC is not only a major intrinsic factor controlling the lower reservoir interval,but also an important material to provide the reservoir space for the shale gas.In the late diagenetic stage,the clay mineral assemblages changed from montmorillonite to illite,forming new micropores and leading to an increase of the porosity and great influences on the upper reservoir interval.The content of brittle minerals is more than 50%,facilitating formation of fractures,and the permeability performance can be enhanced significantly.In general,the Wufeng Formation and the bottom interval of the Longmaxi Formation are both high-quality reservoirs and primary pay intervals.
基金supported by the Science and Technology Research Project of China Petroleum&Chemical Corporation“Research on technology for enhancing the recovery in Fuling Shale Gas Field”(No.P22183).
文摘In September 2013,the National Energy Administration approved the establishment of Fuling national shale gas demonstration area(hereinafter referred to as the demonstration area),whose construction was completed in December 2015.After nearly one decade of development,it has grown into the main shale gas production base in China.In order to speed up the integration and breakthrough of China's shale gas theoretical understanding and exploration and development technology and effectively promote the great development of marine shale gas in China,this paper reviews and summarizes the development and construction history of the demonstration area,geological theory understanding,engineering technology and key equipment progress.And based on this,the future development direction of the demonstration area is predicted.And the following research results are obtained.First,shale gas exploration and development in the demonstration area is divided into three stages,i.e.,exploration evaluation,phase I and II construction,and stacked development and adjustment.Second,the“binary enrichment”theory for marine shale gas and the engineering theory for efficiently developing gas reservoirs are innovatively established.Third,a series of supporting technologies are innovatively developed,such as optimized and fast drilling technology for shale gas cluster horizontal wells,differentiated network fracturing technology,high-efficiency gas production,gathering and transportation technology,and green development technology for karst mountains,and the localization of key equipment and tools is realized.Fourth,the efficient development of shallow overpressure shale gas reservoirs above 3500 m in depth and the effective development of shale gas reservoirs at the depth of 3500e4000 m are realized in the demonstration area.Fifth,the construction of the demonstration area in the future includes accelerating the development of normal-pressure deep shale gas,continuously tackling key shale gas EOR technologies,actively promoting the field application of new technologies and methods,and powerfully strengthening the construction of green demonstration areas.In conclusion,this demonstration area is the earliest one of four national shale gas demonstration areas,and its achievements will provide continuous guidance for the shale gas exploration and development in China and play a demonstrative and guiding role in promoting the development of shale gas geological theories and exploration and development technologies in China.
基金sponsored by the China Postdoctoral Science Foundation(No.2021M703000):Formation mechanism of a compressive fracture network constrained by weak surfaces of shale bedding.
文摘Bedding fractures are among the key factors affecting the production efficiency of shale oil and gas,but relatively little research has been conducted on the effectiveness of bedding fractures.Based on field outcrops and drill cores from the Fuling area in the Sichuan Basin,this work discusses the development,filling,and opening characteristics of bedding fractures and their quantitative impact on physical properties.Multiple methods were employed,e.g.,immersion testing,wet illumination,high-power microscanning,imaging logging identification and experimental measurement.The results indicate that the highest density reaches 437 fractures per meter,with apertures less than 0.5µm being the majority.The average permeability of the shale samples with vertical bedding is 44.6 times that of the shale samples with parallel bedding,while the porosity exhibits less anisotropy.Many open bedding fractures with gas outlets in the core are shown by on-site immersion experiments and electron microscopy scanning experiments.Each dark stripe on the imaging logging map corresponds to a bedding fracture,and the thickness of the dark stripes corresponds to the aperture of the bedding fracture.There is no need to consider unfilled bedding fractures,as fractures filled with calcite veins and pyrite crystals can also become effective seepage channels because of the pores within the calcite veins and between the pyrite crystals.The utilization and transformation of bedding fractures during fracturing is one of the key steps in producing shale oil and gas.It is necessary to combine the in situ stress field,bedding fracture characteristics,and fracturability of shales to reasonably utilize bedding fractures to transform oil and gas reservoirs.
