During the hydraulic fracturing of shale gas in the southern Sichuan Basin,China,field monitoring data have shown that hydraulic fracture(HF)propagation is restricted by height and cannot sufficiently cover vertical p...During the hydraulic fracturing of shale gas in the southern Sichuan Basin,China,field monitoring data have shown that hydraulic fracture(HF)propagation is restricted by height and cannot sufficiently cover vertical pay layers.The geomechanical behavior of gas shale in this region creates heterogeneity between the layers,which is responsible for the height restriction of HF propagation and limits the safe and efficient development of shale gas reservoirs in this region.To study vertical HF propagation,we conducted a series of laboratory hydraulic fracturing experiments under true triaxial loading.Three kinds of heterogeneity factors were tested:stress,elasticity,and interface strength.Analysis of fracture morphology and injection pressure curves resulted in several findings:(1)four types of vertical HF shapes emerged:Ishape,restricted I-shape,T-shape,and H-shape;(2)HF was induced by weakly cemented interface(s)with height limitations,while a layer under larger stress(e.g.,6 MPa)restricted fracture propagation in the middle layers,and heterogeneous elasticity was resistant;(3)regarding the geomechanical status of Changning middle-deep gas shale,interface strength may be more significant than fracture height.This study demonstrates the role of vertical heterogeneity in limiting fracture height and provides theoretical support for hydraulic fracturing optimization in this region.展开更多
Oil and gas shows are rich in drilling wells in Kaiping sag,however,large oilfield was still not found in this area.For a long time,it is thought that source rocks were developed in the middle-deep lacustrine facies i...Oil and gas shows are rich in drilling wells in Kaiping sag,however,large oilfield was still not found in this area.For a long time,it is thought that source rocks were developed in the middle-deep lacustrine facies in the Eocene Wenchang Formation,while there is no source rocks that in middle-deep lacustrine facies have been found in well.Thickness of Wenchang Formation is big and reservoirs with good properties could be found in this formation.Distribution and scale of source rock are significant for further direction of petroleum exploration.Distribution characterization of middle-deep lacustrine facies is the base for source rock research.Based on the sedimentary background,fault activity rate,seismic response features,and seismic attributes were analyzed.No limited classification method and multi-attributes neural network deep learning method were used for predicting of source rock distribution in Wenchang Formation.It is found that during the deposition of lower Wenchang Formation,activity rate of main fault controlling the sub sag sedimentation was bigger than 100 m/Ma,which formed development background for middle-deep lacustrine facies.Compared with the seismic response of middle-deep lacustrine source rocks developed in Zhu I depression,those in Kaiping sag are characterized in low frequency and good continuity.Through RGB frequency decomposition,areas with low frequency are main distribution parts for middle-deep lacustrine facies.Dominant frequency,instantaneous frequency,and coherency attributes of seismic could be used in no limited classification method for further identification of middle-deep lacustrine facies.Based on the limitation of geology knowledge,multi-attributes of seismic were analyzed through neural network deep learning method.Distribution of middle-deep lacustrine facies in the fourth member of Wenchang Formation is oriented from west to east and is the largest.Square of the middle-deep lacustrine facies in that member is 154 km^(2)and the volume is 50 km^(3).Achievements could be bases for hydrocarbon accumulation study and for exploration target optimization in Kaiping sag.展开更多
Since the approval to establishment,the Changning-Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin(hereinafter referred to as Demonstration Area)has been built up into a shale gas industry demonstrat...Since the approval to establishment,the Changning-Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin(hereinafter referred to as Demonstration Area)has been built up into a shale gas industry demonstration base characterized with scale,technology,management and green after more than 10 years of exploration and practice.Its successful experience is of great guiding significance to the efficient development of unconventional oil and gas resources in China.In this paper,the technologies which were developed for the beneficial development of the Demonstration Area during the 13th Five-Year Plan are systematically reviewed and summarized.Then,some countermeasures are proposed to solve the difficulties and challenges to the long-term benefit and stable production of middle-deep shale gas in this area.And the following research results are obtained.First,during the construction of the Demonstration Area,the“three-control”shale gas enrichment and high-production theory is innovatively proposed,and the shale gas enrichment model in the southern Sichuan Basin is clarified.Second,a high-production well cultivation method based on geology-engineering integration is established by developing six main technologies for shale gas exploration and development,which effectively supports the large-scale beneficial development of shale gas in the Demonstration Area.Third,the beneficial development model of middle-deep shale gas in the southern Sichuan Basin is preliminarily formed,and the benefit and efficiency of productivity construction are improved comprehensively.Fourth,the three measures of“controlling the decline rate,enhancing the reserve production and expanding the periphery”are used to support the replacement and stable production of middle-deep shale gas.In conclusion,to sustainably ensure the long-term benefit and stable production of shale gas in the southern Sichuan Basin,it is still necessary to deepen fine reservoir description and complex mechanism understanding and explore EOR technologies.What’s more,the important mean to improve the single-well shale gas production rate in this area is to strengthen the fine fracturing design and implementation under the deep integration of geology and engineering and improve the construction quality of fracturing network continuously.Furthermore,the only way to the low-cost development of the demonstration area is to promote the management reform and innovation continuously and improve the beneficial development model further.展开更多
基金supported by the National Key R&D Program of China(Grant No:2023YFF0614100)the National Natural Science Foundation of China(Grant Nos:52204005,52192622,52374004)the Science and Technology Project of CNPC,China(Grant No:2023ZZ21).
文摘During the hydraulic fracturing of shale gas in the southern Sichuan Basin,China,field monitoring data have shown that hydraulic fracture(HF)propagation is restricted by height and cannot sufficiently cover vertical pay layers.The geomechanical behavior of gas shale in this region creates heterogeneity between the layers,which is responsible for the height restriction of HF propagation and limits the safe and efficient development of shale gas reservoirs in this region.To study vertical HF propagation,we conducted a series of laboratory hydraulic fracturing experiments under true triaxial loading.Three kinds of heterogeneity factors were tested:stress,elasticity,and interface strength.Analysis of fracture morphology and injection pressure curves resulted in several findings:(1)four types of vertical HF shapes emerged:Ishape,restricted I-shape,T-shape,and H-shape;(2)HF was induced by weakly cemented interface(s)with height limitations,while a layer under larger stress(e.g.,6 MPa)restricted fracture propagation in the middle layers,and heterogeneous elasticity was resistant;(3)regarding the geomechanical status of Changning middle-deep gas shale,interface strength may be more significant than fracture height.This study demonstrates the role of vertical heterogeneity in limiting fracture height and provides theoretical support for hydraulic fracturing optimization in this region.
文摘Oil and gas shows are rich in drilling wells in Kaiping sag,however,large oilfield was still not found in this area.For a long time,it is thought that source rocks were developed in the middle-deep lacustrine facies in the Eocene Wenchang Formation,while there is no source rocks that in middle-deep lacustrine facies have been found in well.Thickness of Wenchang Formation is big and reservoirs with good properties could be found in this formation.Distribution and scale of source rock are significant for further direction of petroleum exploration.Distribution characterization of middle-deep lacustrine facies is the base for source rock research.Based on the sedimentary background,fault activity rate,seismic response features,and seismic attributes were analyzed.No limited classification method and multi-attributes neural network deep learning method were used for predicting of source rock distribution in Wenchang Formation.It is found that during the deposition of lower Wenchang Formation,activity rate of main fault controlling the sub sag sedimentation was bigger than 100 m/Ma,which formed development background for middle-deep lacustrine facies.Compared with the seismic response of middle-deep lacustrine source rocks developed in Zhu I depression,those in Kaiping sag are characterized in low frequency and good continuity.Through RGB frequency decomposition,areas with low frequency are main distribution parts for middle-deep lacustrine facies.Dominant frequency,instantaneous frequency,and coherency attributes of seismic could be used in no limited classification method for further identification of middle-deep lacustrine facies.Based on the limitation of geology knowledge,multi-attributes of seismic were analyzed through neural network deep learning method.Distribution of middle-deep lacustrine facies in the fourth member of Wenchang Formation is oriented from west to east and is the largest.Square of the middle-deep lacustrine facies in that member is 154 km^(2)and the volume is 50 km^(3).Achievements could be bases for hydrocarbon accumulation study and for exploration target optimization in Kaiping sag.
基金supported by the National Major Science and Technology Project“Changning-Weiyuan shale gas development demonstration project”(No.2016ZX05062)the Major Science and Technology Project of PetroChina Company Limited“Research and application of key technologies for producing 30 billion cubic meters of natural gas in Southwest Oil and Gas Field”(No.2016E-0611).
文摘Since the approval to establishment,the Changning-Weiyuan National Shale Gas Demonstration Area in the Sichuan Basin(hereinafter referred to as Demonstration Area)has been built up into a shale gas industry demonstration base characterized with scale,technology,management and green after more than 10 years of exploration and practice.Its successful experience is of great guiding significance to the efficient development of unconventional oil and gas resources in China.In this paper,the technologies which were developed for the beneficial development of the Demonstration Area during the 13th Five-Year Plan are systematically reviewed and summarized.Then,some countermeasures are proposed to solve the difficulties and challenges to the long-term benefit and stable production of middle-deep shale gas in this area.And the following research results are obtained.First,during the construction of the Demonstration Area,the“three-control”shale gas enrichment and high-production theory is innovatively proposed,and the shale gas enrichment model in the southern Sichuan Basin is clarified.Second,a high-production well cultivation method based on geology-engineering integration is established by developing six main technologies for shale gas exploration and development,which effectively supports the large-scale beneficial development of shale gas in the Demonstration Area.Third,the beneficial development model of middle-deep shale gas in the southern Sichuan Basin is preliminarily formed,and the benefit and efficiency of productivity construction are improved comprehensively.Fourth,the three measures of“controlling the decline rate,enhancing the reserve production and expanding the periphery”are used to support the replacement and stable production of middle-deep shale gas.In conclusion,to sustainably ensure the long-term benefit and stable production of shale gas in the southern Sichuan Basin,it is still necessary to deepen fine reservoir description and complex mechanism understanding and explore EOR technologies.What’s more,the important mean to improve the single-well shale gas production rate in this area is to strengthen the fine fracturing design and implementation under the deep integration of geology and engineering and improve the construction quality of fracturing network continuously.Furthermore,the only way to the low-cost development of the demonstration area is to promote the management reform and innovation continuously and improve the beneficial development model further.
