四川盆地筇竹寺组页岩气地质工程特征及开发先导试验成效OA

The Lower Cambrian Qiongzhusi Formation is the most strategically valuable shale gas replacement formation in the Sichuan Basin.However,its particular geological and engineering conditions differ markedly from those of the Longmaxi Formation which is currently in the stage of mature development,meaning that existing technical systems cannot be directly replicated.Focusing on the exploration appraisal wells and pilot horizontal wells in the Z201 wellblock and its adjacent areas in the Ziyang Region of the Sichuan Basin,this paper systematically compares the Qiongzhusi Formation with the Longmaxi Formation reservoirs,and then reveals the geological and engineering characteristics governing the development of Qiongzhusi Formation shale gas by making comprehensive use of seismic interpretation,image logging,fiber-optic monitoring,microseismic monitoring,fracturing and production performance data.The following results are obtained.First,influenced by high-angle natural fractures,a low Q value of 0.6-1.2,and a high Young's modulus of 35-50 GPa,the hydraulic fracture network in the Qiongzhusi Formation exhibits a fishbone-shaped propagation pattern,which differs from the H-shaped pattern commonly observed in the Longmaxi Formation.The Qiongzhusi Formation reservoirs are more heterogeneous.Second,casing program optimization and managed-pressure drilling technology significantly reduce drilling complexities,and supported by specific tools,improve the drilling efficiency,with the target drilling rate up to 96%-100%.Third,a quantitative classification scheme is established for three reservoir types,i.e.,matrix-dominated,vertically fractured,and laterally fractured reservoirs,and the corresponding differentiated fracturing technologies are then proposed.The Qiongzhusi Formation is superior to the Longmaxi Formation in terms of fracturing stimulation effectiveness,with the gas production per unit pressure drop approximately three times that of deep Longmaxi Formation.Fourth,the analysis on productivity controlling factors indicates that the thickness of high-quality reservoirs is the decisive basis for high yield.Under comparable geological conditions,an 11%increase in stimulation intensity can drive a 13%increase in EUR.In conclusion,the Qiongzhusi Formation holds great potential for the large-scale development of deep shale gas,and targeted drilling,optimized fracturing technologies and differentiated development strategies can effectively resolve the difficulties in deep reservoir development.The research findings provide a core technical reference for the large-scale,cost-effective development of the Qiongzhusi Formation.