北部湾盆地涠西南凹陷低阻油层成因分析

Analysis on cause of low-resistivity oil layer formation in Weixinan Sag of Beibuwan Basin

随着涠西南凹陷油田的滚动勘探,发现了很多井不同层段储层中具有低阻现象。如何有效地识别低阻油层,已成为困扰勘探和亟需解决的问题。为有效解决低阻油层的识别问题,从黏土矿物质量分数、导电矿物、钻井液浸泡时间及围岩厚度的影响等方面综合分析低阻油层的成因,认为高伊利石质量分数、导电矿物和储层较薄受围岩影响为涠西南凹陷低阻油层三大成因,为有效识别低阻油层、避免油层错判提供了重要依据。根据该认识对WZ10-8-1井进行了再分析,认为过去解释为水层的储层实质上为低阻油层,对该构造勘探的深入研究具有一定的指导意义,同时扩大了整个凹陷的勘探领域。

Several low-resistivity oil layers are found during the progressive exploration in Weixinan Sag of Beibuwan Basin,South China Sea.How to distinguish the low-resistivity oil layer from the water layer is a challenge of petroleum exploration in this area,which should be solved effectively.Through comprehensively analyzing the cause of formation for low-resistivity oil layer from the clay mineral,conductive mineral,mud invasion time and the influence of surrounding rock,the author considers that there are three factors causing the low-resistivity oil layer,which are high illite,high condunctive mineral and thin reservoir.This study can provide an important basis for identifying the low-resistivity oil layer.Based on this,Well WZ10-8-1 is reinterpreted.The reservoir interpreted as water layer in the past is considered as to be low-resistivity oil layer at present,which not only has a meaning for further research of this structure,but also extends the exploration area of Weixinan Sag.