淡水钻井液侵入油层形成低电阻率环带的综合研究与应用分析

通过对钻井液侵入油层的理论研究和数值模拟分析，可定量计算钻井液侵入后油层含水饱和度、地层水矿化度（电阻率）的径向分布以及地层电阻率的径向变化。应用相对渗透率的概念，对淡水钻井液滤液侵入油层形成低电阻率环带的过程进行了解释。分析了储集层的孔隙度、含水饱和度和钻井液矿化度等因素变化对地层径向电阻率分布和低电阻率环带的影响。在一维含油岩心钻井液滤液驱替实验和实际测井资料中，均测量到了低电阻率环带的存在。低电阻率环带的存在对高频感应电阻率测井影响较大，而低频侧向电阻率测井几乎不受影响。可以用阵列感应或阵列电磁波测井测量出的低电阻率环带来识别低电阻率油层。图7参11

Forming mechanism and application of low resistivity annulus in oil reservoirs invaded by fresh drilling mud

The invasion profiles of mud filtrate invading into a permeable layer was theoretically studied and numerically analyzed. By means of simulation, the radial distribution of formation water saturation, salinity and formation resistivity after invasion were computed. The forming process of the low resistivity annulus was explained on the concept of relative permeability. The effects of formation parameters, such as formation porosity, water saturation and mud filtrate salinity, on the invasion profiles were also analyzed. The existence of low resistivity annulus was proved by one dimensional oil-bearing core displacement experiment with fresh mud filtrate and by field logging data. It is found that the effect of low resistivity annulus on induction logs, such as array induction logs, is greater than that on lateral logs, and that the identification of low resistivity annulus from array induction logs can be used to classify oil payzone.