Rock electric analysis and gas zone identification of karst reservoirs,north slope of central Sichuan paleouplift
With low matrix porosity as well as developed secondary dissolution pores and vugs,the very thick,kart-controlled Sinian dolomite reservoirs in the north slope of central Sichuan paleouplift,Sichuan Basin,exhibit complex gas-water relationship.Moreover,they are diverse in types.These performances lead to a non-Archie phenomenon existing in reservoir's rock electric relationship.In addition,a difference between heterogeneity and formation-water salinity in the reservoirs may conceal well-logging response charac-teristics of gas and water,making it pretty difficult to identify gas and water through well logging.Thus,parameters on the saturation model were optimized after the analysis of rock electric parameters,acoustic characteristics experimental data and formation-water data about various types of full-diameter cores.And dependent on acoustic and resistivity data,three logging methods to identify a gas zone have been established,such as the calculated resistivity from different saturation and real resistivity overlapping identification,matrix resistivity and actual resistivity overlapping identification,and the ratio of VP/VS computed by the theory and real ratio over-lapping identification.These methods were applied to the Sinian Dengying reservoirs in the north slope of central Sichuan paleouplift,achieving the coincidence rate of 93.1%.
Full-diameter core classificationRock-electric experimental analysisFormation-water analysisExperimental analysis on acoustic characteristicsGas zone identification method
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