塔里木盆地低电阻率油层成因与评价

Genesis and Evaluation of Low Resistivity Oil Formation in Tarim Basin

随着塔里木盆地油气勘探工作的深入 ,相继发现了一批低电阻油层 ,油层电阻率最低达 0 .4 5Ω·m ,与水层的电阻率几乎相当 .通过对轮南侏罗系JⅣ 、吉拉克三叠系TⅡ 和哈得逊石炭系CⅢ 3套低电阻油层的地质与实验分析认为 ,引起低电阻的主要原因是黄铁矿的局部富集、粘土矿物以及高矿化度束缚水等的附加导电 ,提出利用毛管压力资料 ,建立油藏物性、油层高度与含油饱和度的关系以及采用高温高压岩电参数等不同的评价方法 ,从而使计算的饱和度提高 8%～ 2 5 % ,测井解释符合率上升 5 %～ 8% .

As petroleum exploration continues, a series of low-resistivity oil reservoirs have been found in the Tarim basin. The lowest resistivity of the oil reservoir is only 0.45 Ω·m, almost identical to the resistivity of water layer. Geological observations and experimental analyses on the Jurassic (J_Ⅳ) low-resistivity oil reservoir in Lunnan, Triassic (T_Ⅱ) low-resistivity oil reservoir in Jilake and Carboniferous (C_Ⅲ) low-resistivity oil reservoir in Hadexun indicate that the main causes of the low resistivity of the oil reservoirs are the local enrichment of pyrite and the additional electricity conducting effect of clay minerals and the low salinity bound water. Several evaluation methods using different data such as capillary pressure, oil saturation and rock electrical parameters under high temperature and high pressure conditions are presented. Using these methods, the calculated oil saturation increases by 8% to 25%, and the accuracy of well logging explanation increases by 5% to 8%.