南方海相页岩脆性指数与电性关系分析

Relationship analysis between brittle index and electrical properties of marine shale in South China

页岩脆性是评价页岩气储层的重要参素,因此,研究页岩矿物成分及其脆性评价方法意义重大。基于南方海相筇竹寺组和龙马溪组页岩露头标本,通过矿物成分鉴定和复电阻率测试分析,发现脆性矿物和黄铁矿(FeS2)含量高的页岩具有低阻高极化率的电性响应特征,表明利用激发极化参数(IP)进行储层脆性评价具有良好的物性基础。基于矿物成分定义了脆性指数(BI),分析研究了页岩的激电参数与黄铁矿和脆性指数的相关性,初步建立了电阻率以及极化率与脆性指数和黄铁矿含量的关系模型,提出了利用电性异常特征识别和评价页岩气储层的新思路。

The brittleness of shale is an important parameter in the evaluation of shale gas reservoir. Therefore, studying shale mineral composition and evaluation method of brittleness are significant. Through the mineral composition analysis and com- plex resistivity measurement based on the outcrop samples from the Qiongzhusi formation and Longmaxi formation of marine shale in South China, the characteristics of low resistivity and high polarization were revealed in the shale with high brittle- ness minerals and high pyrite content. These characteristics provide a geophysical prerequisite for evaluating the brittleness of shale reservoir by induced polarization （IP） parameters. The brittleness index （BI） is defined based on mineral composition. The correlation between the IP parameters of shale, pyrite content and the brittleness index are analyzed. These research pre- liminary established the relation models between the resistivity, the brittleness index and the pyrite content, as well as the re- lation models between the polarization, the brittleness index and the pyrite content. The new idea of using electrical anomaly characteristics to predict the shale gas reservoir is proposed.