川中古隆起北斜坡岩溶储层岩电分析及气层识别

Rock electric analysis and gas zone identification of karst reservoirs,north slope of central Sichuan paleouplift

四川盆地川中古隆起北斜坡震旦系是受岩溶控制的巨厚白云岩油气藏,气水关系十分复杂,储层呈基质孔隙度低、次生溶蚀孔洞发育特征,而且储层类型多样,致使储层岩电关系存在非Archie现象,同时储层的非均质性和地层水矿化度的差异掩盖了气水的测井响应特征,造成测井气水识别难度大。为此,通过对不同类型全直径岩电参数、声学特性实验数据和地层水资料的综合分析,优选了饱和度模型参数,建立了含水饱和度计算电阻率—实测电阻率重叠判别法、基质电阻率—实测电阻率重叠判别法、理论计算纵横波速度比—实测纵横波速度比重叠判别法3种以声波、电阻率相结合的测井气层识别方案。应用该技术对川中古隆起北斜坡震旦系灯影组储层进行解释,符合率达到93.1%。

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%.