低电阻率油气层物理参数变化机理研究

研究了淡水环境下富含粘土矿物、细颗粒砂岩低电阻率油气层. 分析了粘土的附加导电性,认为粘土质量百分数高且富含伊利石和蒙脱石的地层中,若地层水质量浓度小于15g/L等效NaCl盐溶液时,粘土的附加导电性是造成油气层电阻率低的首要原因. 同时分析了细颗粒、粘土质量百分数不高的储层,高的毛细管压力使束缚水饱和度很高,同样能形成低电阻率油气层. 储层中粘土质量百分数的多少对储层岩石电性特征(I-Sw曲线形态)有重要影响,可用于指导测井资料解释模型的选择.

MECHANISM OF PETROPHYSICAL PARAMETER VARIATIONS IN LOW RESISTIVITY OIL AND GAS RESERVOIRS

Petrophysical experiments were carried out to study low resistivity oil and gas reservoirs, which are rich with clay mineral and fine-grain in the freshwater environment reservoirs. Clay conductance was analyzed. It is found that the most important factor causing low resistivity of oil and gas reservoirs is the additional conductivity due to clay in the formation with high clay mass percent, rich illite and smectite, if the concentration of formation water is low (mass concentration is less than 15g/L equivalent NaCl solution). We also studied the fine-grain reservoirs with low clay mass percent and found that it may also form low resistivity reservoirs under higher irreducible water saturation due to higher capillary pressure. The clay mass percent has significant influence on electrical characteristics of reservoir rocks. This parameter may help us to select a proper log interpretation model.