Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehens...Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehensive review of commonly employed coalbed methane extraction technologies.It then delves into several critical issues in the current stage of CBM exploration and development in China,including the compatibility of existing technologies with CBM reservoirs,the characteristics and occurrence states of CBM reservoirs,critical desorption pressure,and gas generation mechanisms.Our research indicates that current CBM exploration and development technologies in China have reached an internationally advanced level,yet the industry is facing unprecedented challenges.Despite progress in low-permeability,high-value coal seams,significant breakthroughs have not been achieved in exploring other types of coal seams.For different coal reservoirs,integrated extraction technologies have been developed,such as surface pre-depressurisation and segmented hydraulic fracturing of coal seam roof strata.Additionally,techniques like large-scale volume fracturing in horizontal wells have been established,significantly enhancing reservoir stimulation effects and coalbed methane recovery rates.However,all of these technologies are fundamentally based on permeation.These technologies lack direct methods aimed at enhancing the diffusion rate of CBM,thereby failing to fully reflect the unique characteristics of CBM.Current CBM exploration and development theories and technologies are not universally applicable to all coal seams.They do not adequately account for the predominantly adsorbed state of CBM,and the complex and variable gas generation mechanisms further constrain CBM development in China.Finally,continuous exploration of new deep CBM exploration technologies is necessary.Integrating more effective reservoir stimulation technologies is essential to enhance technical adaptability concerning CBM reservoir characteristics,gas occurrence states,and gas generation mechanisms,ultimately achieving efficient CBM development.We conclude that while China possesses a substantial foundation of deep fractured CBM resources,industry development is constrained and requires continuous exploration of new CBM exploration and development technologies to utilize these resources effectively.展开更多
PetroChina Changqing Oilfield Company(hereinafter referred to as Changqing Oilfield)built the largest oil and gas production base of China in the Ordos Basin in 2013,achieving the yearly natural gas production of 375&...PetroChina Changqing Oilfield Company(hereinafter referred to as Changqing Oilfield)built the largest oil and gas production base of China in the Ordos Basin in 2013,achieving the yearly natural gas production of 375×10^(8) m^(3) in 2015.For the further sustainable and stable production and quality and benefit improvement,such great achievements made in the 12th Five-Year Plan were first summarized,and the relevant favorable conditions for natural gas development were also analyzed as follows:abundant natural gas resources;increasingly mature E&P technologies;continuously improved delicacy management;and a surging demand for natural gas.Then,challenges to natural gas development were also discussed,including obvious deterioration of natural gas resources;diminished capacity of stable production of produced gasfields;increasing number of low-yield wells;and prominent supplyedemand contradiction in present natural gas market.Finally,its prospect in the 13th Five-Year Plan was studied:to carry out natural gas exploration with focus on Upper Paleozoic tight gas,Lower Paleozoic carbonate rocks,and new areas and new domains,so as to achieve rapid growth of natural gas reserves and orderly replacement in exploration domains;to make rational development planning with focus on the stable production of mature gasfields;and to enhance tight gas recovery and strengthen capacity building in new areas,so as to achieve a steady rise of annual gas production in the giant gas province.It is expected that by the end of 13th Five-Year Plan period,Changqing Oilfield will achieve its annual gas production of up to 400×10^(8) m^(3).展开更多
The Zhaotong national shale gas demonstration area in Yunnan(hereinafter referred to as demonstration area)is China's third largest national shale gas production base after ChangningeWeiyuan in Sichuan and Fuling ...The Zhaotong national shale gas demonstration area in Yunnan(hereinafter referred to as demonstration area)is China's third largest national shale gas production base after ChangningeWeiyuan in Sichuan and Fuling in Chongqing.And after more than ten years of deep and careful cultivation,a series of important achievements have been obtained in the exploration and development.From the perspective of exploration and development history,theory and technology,this paper systematically summarizes the exploration discovery process and productivity construction progress of shale gas in the demonstration area,expounds the geological exploration theories and key technologies of mountain shale gas,and predicts their development prospect and direction.And the following research results are obtained.First,the exploration and development in the demonstration area has gone through five development stages,and so far,three major productivity construction zones have been formed,including Huangjinba and Zijinba middleedeep shale gas zones and Taiyang shallow shale gas zone,with cumulative proved geological reserves more than 3100×10^(8) m^(3) and cumulative gas production more than 72×10^(8) m^(3).It has been constructed into the third largest green shale gas demonstration base in China.Second,the“multi-field coordination and multi-element coupling”mountain shale gas enrichment,accumulation and occurrence theory of“sedimentary background controlling source rock and reservoir,reworking intensity controlling preservation,and three-dimensional sealing controlling enrichment”is put forward innovatively,and the“three-dimensional sealing system”accumulation model of extrabasinal shallow shale gas is established.Third,a series of zone selection and evaluation technologies for mountain shale gas in strongly reworked complex structural areas have been developed,and the concept of geologyeengineering integration has first been adopted to create transparent shale gas reservoirs and cultivate high-yield wells.A major exploration breakthrough has been achieved from marginal basin medium deep shale gas layers to extrabasin ultra shallow to medium shallow ones,and domestic first large-scale monoblock shallow shale gas field with reserves over 2570×10^(8) m^(3) has been discovered.Fourth,a landmark technological achievement and efficient development model with geologyeengineering integration and shale geomechanical evaluation as the core has been formed,which leads the clean,green and efficient exploration and development of mountain shale gas.In conclusion,it is necessary to implement the exploration strategic idea of“two outgoing”in the demonstration area,i.e.,“walking out of the stable area of the basin and marching into the complex structure areas in the Dianqianbei Depression”and“walking out of the WufengeLongmaxi Formation and exploring other layers for breakthrough”.What's more,it is recommended to carry out the double-layer stereoscopic horizontal well pattern deployment of“Leping Formation CBM(coal measure gas)þLongmaxi Formation shale gas”appropriately in a large scale,so as to establish a new integrated development model for the three-dimensional efficient development of mountain shale gas and CBM.展开更多
The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geologic...The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.展开更多
Exploration of the Sinian-Lower Paleozoic formations in the Sichuan Basin starts from the 1950s,and is tortuous and complex.To summarize the exploration experiences is of great significance of reference for exploratio...Exploration of the Sinian-Lower Paleozoic formations in the Sichuan Basin starts from the 1950s,and is tortuous and complex.To summarize the exploration experiences is of great significance of reference for exploration of oil and gas in deep carbonate rocks of the Sichuan Basin.Gas accumulation in the Anyue oversize gasfield is chiefly controlled by the Deyang-Anyue intra-platform rift and central Sichuan paleouplift.The intra-platform rift controls the scale hydrocarbon generation center and effective hydrocarbon plays.The Anyue gasfield is characterized by near-source hydrocarbon accumulation.The marginal zone of intra-platform rift and high part of the paleouplift control the scale distribution of favorable facies belts of reservoir development,and overlapped by paleokarstic reformation,the reservoirs are widely distributed.The intra-platform rift and paleouplift jointly control formation of the scale traps and hydrocarbon enrichment.Gas reservoir features and major controlling factors for hydrocarbon accumulation have some differences in the main play strata,such as Longwangmiao Formation,and Member 4 and Member 2 of Dengying Formation.The gas reservoir in the Longwangmiao Formation is a lithologic gas reservoir under the tectonic setting,and the inherited paleouplift is a key for reservoir formation and hydrocarbon accumulation.The gas reservoir in the Member 4 of Dengying Formation is mainly controlled by large structural-stratigraphic composite traps,and the gas reservoir in the Member 2 of Dengying Formation is the structural trap.Distribution of the large gasfields in the Dengying Formation is controlled by the intra-platform rift,near-source hydrocarbon-reservoir configuration controlled by the ancient erosion plane and stratigraphic sealing in the updip direction.For exploration and development of the Anyue gasfield,four series of technologies are developed,namely,reservoir seismic fine description technology,well logging fine evaluation technology of gas layers,fast drilling technology of complex strata,and stimulation technology for high temperature and high pressure gas layers.Technical progresses provide powerful guarantee for efficient exploration and development of the oversize gasfields.展开更多
The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrializatio...The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world.Although the high-rank coal field is characterized by low pressure,low permeability,low saturation and strong heterogeneity,the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior.As main productive intervals,No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system.The coal seam has large thickness,and is mostly composed of humic coal and mainly contains vitrinite.Affected by tectonic thermal events in the Yanshanian period,the coal rank is high,the adsorption capacity is strong,and the gas content is large.Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation,gas phase transformation and sealing of hydrodynamics and roof and floor.In view of the characteristics of the Qinshui Basin topography and the high rank coal,a series of key technologies for exploration and development are developed,including mountainous region seismic acquisition,processing and interpretation technology,drilling and completion technology of multiple wells,drilling and completion technology of multiple horizontal wells dominated by compound V type,deplugging secondary fracturing stimulation technology,control technology of high rank CBM drainage,and CBM gathering and transportation technology,which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.展开更多
基金supported by the National Natural Science Foundation of China(52074045,52274074)the Science Fund for Distinguished Young Scholars of Chongqing(CSTB2022NSCQ-JQX0028).
文摘Developing deep fragmented soft coalbed methane(CBM)can significantly enhance domestic natural gas supplies,reduce reliance on imported energy,and bolster national energy security.This manuscript provides a comprehensive review of commonly employed coalbed methane extraction technologies.It then delves into several critical issues in the current stage of CBM exploration and development in China,including the compatibility of existing technologies with CBM reservoirs,the characteristics and occurrence states of CBM reservoirs,critical desorption pressure,and gas generation mechanisms.Our research indicates that current CBM exploration and development technologies in China have reached an internationally advanced level,yet the industry is facing unprecedented challenges.Despite progress in low-permeability,high-value coal seams,significant breakthroughs have not been achieved in exploring other types of coal seams.For different coal reservoirs,integrated extraction technologies have been developed,such as surface pre-depressurisation and segmented hydraulic fracturing of coal seam roof strata.Additionally,techniques like large-scale volume fracturing in horizontal wells have been established,significantly enhancing reservoir stimulation effects and coalbed methane recovery rates.However,all of these technologies are fundamentally based on permeation.These technologies lack direct methods aimed at enhancing the diffusion rate of CBM,thereby failing to fully reflect the unique characteristics of CBM.Current CBM exploration and development theories and technologies are not universally applicable to all coal seams.They do not adequately account for the predominantly adsorbed state of CBM,and the complex and variable gas generation mechanisms further constrain CBM development in China.Finally,continuous exploration of new deep CBM exploration technologies is necessary.Integrating more effective reservoir stimulation technologies is essential to enhance technical adaptability concerning CBM reservoir characteristics,gas occurrence states,and gas generation mechanisms,ultimately achieving efficient CBM development.We conclude that while China possesses a substantial foundation of deep fractured CBM resources,industry development is constrained and requires continuous exploration of new CBM exploration and development technologies to utilize these resources effectively.
文摘PetroChina Changqing Oilfield Company(hereinafter referred to as Changqing Oilfield)built the largest oil and gas production base of China in the Ordos Basin in 2013,achieving the yearly natural gas production of 375×10^(8) m^(3) in 2015.For the further sustainable and stable production and quality and benefit improvement,such great achievements made in the 12th Five-Year Plan were first summarized,and the relevant favorable conditions for natural gas development were also analyzed as follows:abundant natural gas resources;increasingly mature E&P technologies;continuously improved delicacy management;and a surging demand for natural gas.Then,challenges to natural gas development were also discussed,including obvious deterioration of natural gas resources;diminished capacity of stable production of produced gasfields;increasing number of low-yield wells;and prominent supplyedemand contradiction in present natural gas market.Finally,its prospect in the 13th Five-Year Plan was studied:to carry out natural gas exploration with focus on Upper Paleozoic tight gas,Lower Paleozoic carbonate rocks,and new areas and new domains,so as to achieve rapid growth of natural gas reserves and orderly replacement in exploration domains;to make rational development planning with focus on the stable production of mature gasfields;and to enhance tight gas recovery and strengthen capacity building in new areas,so as to achieve a steady rise of annual gas production in the giant gas province.It is expected that by the end of 13th Five-Year Plan period,Changqing Oilfield will achieve its annual gas production of up to 400×10^(8) m^(3).
基金Project supported by the Scientific Research and Technology Development Project PetroChina Company Limited“Research on microscopic characteristics and enrichment mechanism of shallow shale gas reservoirs in Zhaotong”(No.2021DJ1903)“Field test of downhole fiber intelligent monitoring technology”(No.2020F-44).
文摘The Zhaotong national shale gas demonstration area in Yunnan(hereinafter referred to as demonstration area)is China's third largest national shale gas production base after ChangningeWeiyuan in Sichuan and Fuling in Chongqing.And after more than ten years of deep and careful cultivation,a series of important achievements have been obtained in the exploration and development.From the perspective of exploration and development history,theory and technology,this paper systematically summarizes the exploration discovery process and productivity construction progress of shale gas in the demonstration area,expounds the geological exploration theories and key technologies of mountain shale gas,and predicts their development prospect and direction.And the following research results are obtained.First,the exploration and development in the demonstration area has gone through five development stages,and so far,three major productivity construction zones have been formed,including Huangjinba and Zijinba middleedeep shale gas zones and Taiyang shallow shale gas zone,with cumulative proved geological reserves more than 3100×10^(8) m^(3) and cumulative gas production more than 72×10^(8) m^(3).It has been constructed into the third largest green shale gas demonstration base in China.Second,the“multi-field coordination and multi-element coupling”mountain shale gas enrichment,accumulation and occurrence theory of“sedimentary background controlling source rock and reservoir,reworking intensity controlling preservation,and three-dimensional sealing controlling enrichment”is put forward innovatively,and the“three-dimensional sealing system”accumulation model of extrabasinal shallow shale gas is established.Third,a series of zone selection and evaluation technologies for mountain shale gas in strongly reworked complex structural areas have been developed,and the concept of geologyeengineering integration has first been adopted to create transparent shale gas reservoirs and cultivate high-yield wells.A major exploration breakthrough has been achieved from marginal basin medium deep shale gas layers to extrabasin ultra shallow to medium shallow ones,and domestic first large-scale monoblock shallow shale gas field with reserves over 2570×10^(8) m^(3) has been discovered.Fourth,a landmark technological achievement and efficient development model with geologyeengineering integration and shale geomechanical evaluation as the core has been formed,which leads the clean,green and efficient exploration and development of mountain shale gas.In conclusion,it is necessary to implement the exploration strategic idea of“two outgoing”in the demonstration area,i.e.,“walking out of the stable area of the basin and marching into the complex structure areas in the Dianqianbei Depression”and“walking out of the WufengeLongmaxi Formation and exploring other layers for breakthrough”.What's more,it is recommended to carry out the double-layer stereoscopic horizontal well pattern deployment of“Leping Formation CBM(coal measure gas)þLongmaxi Formation shale gas”appropriately in a large scale,so as to establish a new integrated development model for the three-dimensional efficient development of mountain shale gas and CBM.
基金supported by the National Research Council of Science and Technology Major Project of China(No.2016ZX05050,No.2017ZX05001002)National Key Basic Research Project of China(973 Program)(No.2014CB239003).
文摘The Qingcheng oilfield,the largest shale oil field in China,was discovered in 2019 in source rock of Chang 7 Member of Mesozoic Yanchang Formation,Changqing Oilfield in Ordos Basin,with newly increased proven geological reserves of 358 million tons,predicted geological reserves of 693 million tons,and a total of 1.051 billion tons of shale oil resources.This achieves a historic breakthrough in exploration of shale oil in Chang 7 Member.In recent years,focusing on key issues,such as whether there develop sweet spots in source rock,whether commercial oil production capacity can be formed,and whether scale-effective development can be achieved,studies about geological conditions for shale oil accumulation have been continuously carried out,key supporting technologies have been developed,and a series of theoretical innovations and technological breakthroughs have been achieved in oil exploration in source rocks.The results indicate that shale oil accumulation in Chang 7 Member is controlled by following factors.Firstly,lacustrine black shale,dark mudstone and other high-quality source rocks lay a material foundation for shale oil formation.Secondly,sandy deposits intercalated within black shale and dark mudstones are exploration sweet spots,and sandbody combination types are controlled by morphology of bottom of the lacustrine basin.Thirdly,reservoir properties are good due to development of micro-nano pore throats.Finally,reservoirs with high oil saturation and high gas-oil ratio are formed due to high-intensity oil charging in source rock.Effective matching of multiple factors is a key for shale oil accumulation in Chang 7 Member in Ordos Basin.Through innovation of key supporting technologies,exploration and development technologies for shale oil are developed,and substantial breakthrough on exploration and development of shale oil is realized.The first application of logging-seismic combination technology in loess plateau improves significantly quality of 3D seismic data,which effectively guides prediction of sandy sweet spots.Three-quality well logging technology is used for further evaluation of geological and engineering sweet spots of shale oil.With volumetric fracturing technology based on precise segmentation of long horizontal wells,initial daily oil production of individual well is increased from previously 10 tons to more than 18 tons.The exploration breakthrough in source rocks in Chang 7 Member in Qingcheng oilfield provides an important resource base for the second accelerated development of Changqing Oilfield.It is predicated that oil production from shale in Chang 7 Member in Qingcheng oilfield will reach three million tons in 2022 and five million tons in 2025.
基金The work was supported by the National Science and Technology Major Project of China(No.2016ZX05004005,2016ZX05007004).
文摘Exploration of the Sinian-Lower Paleozoic formations in the Sichuan Basin starts from the 1950s,and is tortuous and complex.To summarize the exploration experiences is of great significance of reference for exploration of oil and gas in deep carbonate rocks of the Sichuan Basin.Gas accumulation in the Anyue oversize gasfield is chiefly controlled by the Deyang-Anyue intra-platform rift and central Sichuan paleouplift.The intra-platform rift controls the scale hydrocarbon generation center and effective hydrocarbon plays.The Anyue gasfield is characterized by near-source hydrocarbon accumulation.The marginal zone of intra-platform rift and high part of the paleouplift control the scale distribution of favorable facies belts of reservoir development,and overlapped by paleokarstic reformation,the reservoirs are widely distributed.The intra-platform rift and paleouplift jointly control formation of the scale traps and hydrocarbon enrichment.Gas reservoir features and major controlling factors for hydrocarbon accumulation have some differences in the main play strata,such as Longwangmiao Formation,and Member 4 and Member 2 of Dengying Formation.The gas reservoir in the Longwangmiao Formation is a lithologic gas reservoir under the tectonic setting,and the inherited paleouplift is a key for reservoir formation and hydrocarbon accumulation.The gas reservoir in the Member 4 of Dengying Formation is mainly controlled by large structural-stratigraphic composite traps,and the gas reservoir in the Member 2 of Dengying Formation is the structural trap.Distribution of the large gasfields in the Dengying Formation is controlled by the intra-platform rift,near-source hydrocarbon-reservoir configuration controlled by the ancient erosion plane and stratigraphic sealing in the updip direction.For exploration and development of the Anyue gasfield,four series of technologies are developed,namely,reservoir seismic fine description technology,well logging fine evaluation technology of gas layers,fast drilling technology of complex strata,and stimulation technology for high temperature and high pressure gas layers.Technical progresses provide powerful guarantee for efficient exploration and development of the oversize gasfields.
基金This research is supported by the National Basic Research Program of China(973 Program)(2009CB219600)National Science and Technology Major Project(2016ZX05003-002).
文摘The Qinshui Basin has been explored for more than 60 years through two stages of oil and gas reconnaissance survey and exploration&development of coalbed methane(CBM),it has become the largest CBM industrialization base in China and also is a model which successfully realize commercialization of CBM of high rank coal-bearing basin in the world.Although the high-rank coal field is characterized by low pressure,low permeability,low saturation and strong heterogeneity,the exploration practice and research show that the accumulation conditions of CBM reservoir in the Qinshui Basin are superior.As main productive intervals,No.15 coal seam of Taiyuan Formation and No.3 coal seam of Shanxi Formation respectively belong to the epicontinental-sea carbonate platform sedimentary system and the epicontinental-sea shallow-water delta sedimentary system.The coal seam has large thickness,and is mostly composed of humic coal and mainly contains vitrinite.Affected by tectonic thermal events in the Yanshanian period,the coal rank is high,the adsorption capacity is strong,and the gas content is large.Formation of the CBM reservoir goes through three stages including two stages of hydrocarbon generation,gas phase transformation and sealing of hydrodynamics and roof and floor.In view of the characteristics of the Qinshui Basin topography and the high rank coal,a series of key technologies for exploration and development are developed,including mountainous region seismic acquisition,processing and interpretation technology,drilling and completion technology of multiple wells,drilling and completion technology of multiple horizontal wells dominated by compound V type,deplugging secondary fracturing stimulation technology,control technology of high rank CBM drainage,and CBM gathering and transportation technology,which effectively supports the scale and industrialization development of high rank CBM in the Qinshui Basin.
