淡水泥浆侵入引起的低阻油气层实例分析

针对淡水泥浆侵入对地层电阻率的影响，分析了造成油气层高侵的成因。认为在淡水泥浆打井时，泥浆矿化度与地层水矿化度差异较大的情况下，由于泥浆大量侵入地层，造成冲洗带混合液淡化对地层电阻率的影响大于含油饱和度降低对地层电阻率的影响，越靠近井壁现象越明显，从而在油气层段表现出高侵特征。指出用淡水泥浆打井，在井况差、泥浆比重大的情况下，由于泥浆大量侵入地层，而在油气层段形成高侵。

Case Study on Low Resistivity Oil & Gas Zone Caused by Fresh Water Mud Invasion

〗Through expatiated on the effect of mud invasion on formation resistivity in a case, in this paper the cause of resistive invasion in oil & gas zone is analyzed. While drilling with fresh water mud, especially the ratio of Rmf and Rw is high, massive mud invasion can make the effect on formation resistivity by desalinization of mixed fluid bigger than that by oil saturation decrease, this phenomenon is more obvious while being closer to the borehole, and so, oil and gas zone is characterized by resistive invasion. It is pointed out when drilling with fresh water mud, due to massive mud invasion into formation, oil and gas zone is likely to be characterized by resistive invasion in the case of bad borehole conditions and high mud density.