Logging-based evaluation for geological-engineering sweet spots in deep coal reservoirs of the DJ block,Ordos Basin
The deep coal seams rich in coalbed methane(CBM)resources feature strong heterogeneity,high stress,high pressure,and challenging stimulation,rendering the accurate sweet spot evaluation crucial to the large-scale production of deep CBM.This study focuses on the logging-based evaluation of integrated geological-engineering sweet spots in deep coal seams,establishing an evaluation model with 12 evaluation indices using the analytic hierarchy process(AHP)method.Employing this model,we carry out sweet spot assessment of deep coal seams in over 20 wells in the DJ block.The results indicate that the major determinants of the geological-engineering sweet spots are strongly correlated with the ratio of a CBM well's daily gas production to its construction pressure in the proppant transport stage(Ip).The upper part of deep coal seams in the DJ block generally exhibits superior sweet spots compared to its middle and lower counterparts.Specifically,the upper,middle-lower,and lower parts predominantly exhibit Class Ⅰ,Ⅲ,and Ⅱ sweet spots,respectively.Gas content and brittleness index are identified as the primary factors controlling high-quality reservoirs and engineering sweet spots.The coal seams'roofs and floors consist of thick limestones and mudstones,which exhibit significantly different mechanical properties from the coal seams and thus effectively block the propagation of induced fractures across the coal seams.The fracturing conditions and production test results indicate promising outcomes of the logging-based evaluation model.Therefore,this model can be applied to the logging-based selection and evaluation of the optimal perforation sections for the hydraulic fracturing of deep coal seams.
ratio of daily gas production to construction pressure(Ip)gascontentbrittleness indexgeological-engineering integrationsweet spot evaluationdeep coalbed methane(CBM)Ordos Basin
万方数据
维普
