Theory And Method For Compatibility Evaluation Of Joint Deep Coalbed Methane And Tight Sandstone Gas Production

Joint gas production from multi-type of reservoirs in coal measure can not only solve the difficulties in the development of deep coalbed methane（CBM）,but also reduce enormously the production cost and improve the recovery and profit.Thus,the author in this thesis focus on the Linxing block on the northeastern Ordos basin and discusses the coexistence and joint production feasibility of CBM and tight sandstone gas（TSG）.Firstly,combining with the data of the regional geological research achievements,the geophysical exploration,drilling and experimental outcomes,the exploration potential of CBM on the upper of C_2b formation and TGS on P_1t2 formation is demonstrated.It was found that the coal reservoirs on the upper of C_2b formation is valuable to develop because they has higher CBM content,medium permeability,medium coal quality,high free gas proportion,low water production and slowly rising gas production.The overlaying the 2nd member in Taiyuan Formation possesses five poor and good TGS reservoirs which indicates the potential for joint or independent exploitation.Secondly,based on the reservoir distribution,hydrocarbon-generating intensity and CBM/TSG occurrence on the upper of C_2b formation and on P_1t2,the CBM/TSG accumulation mechanism and pattern are summarized.It was suggested that there is the joint gas production foundation of gas production layer combination on the upper of C_2b formation and on P_1t2,the accumulation mechanism show the gas layer height controlled by hydrocarbon-generating intensity,the gas layer distribution controlled by lithological assemblage and the migration channels from the microfracture network.Thirdly,the key geological factors of the joint production was revealed by the coupling in-situ stress and fracture analysis,joint well-seismic modeling and numerical stress field simulation.The comprehensive description method for the lithofacies,stress and full-scale fractures was improved.The thesis demonstrates that gas production rate is directly proportional to the high density of fracture in Linxing block.The lithofacies and thickness of the interlayers between pay layers decide the approaches applied to joint production and effects of reservoir fracturing.Fourthly,combining with the grey correlation analysis theory and fracturing practice,the method for optimizing the joint CBM and TSG production spots in the Linxing block was set up and then the spots in the block were predicted.It is conclused that the favorable spots of joint production might be located at the northern part（which near to the zone of the wells LX19,LX26,LX4 and LX101）and the southern part（including wells LX1 and LX13）.Fifthly,based on the objective understandings on the key geological factors,the geological compatibility of joint CBM and TSG production is discussed with the numerical simulation.The results show the joint production will enhance the cumulative gas production of 14.3%～17.03%in next two decades and achieve a more significant development of comprehensive benefits.