川东南五峰-龙马溪组页岩储层六性特征及主控因素分析

Six characteristics and main controlling factors of shale reservoirs in the Wufeng-Longmaxi formations, southeastern Sichuan Basin

张汉荣 王强 倪楷 李春燕

Zhang Hanrong Wang Qiang Ni Kai Li Chunyan

中国石化 勘探分公司, 成都 610041

SINOPEC Exploration Company, Chengdu, Sichuan 610041, China

川东南五峰-龙马溪组页岩气探井效果差异大,有的富集高产、有的低产,也有干井。通过对比分析10余口页岩气钻井岩心描述、地化分析、氩离子抛光扫描电镜、全岩X衍射、现场含气量测试、测井资料等,研究了页岩储层六性特征,即:岩性、地化特性、可压裂性、物性、含气性和电性特征。研究认为岩性、地化特性、脆性三者之间相关性好,如含放射虫碳质笔石页岩的TOC高、脆性指数也高,受先天条件即沉积环境与相带控制,三者在川东南各井都可以对比;物性和含气性呈正相关,受后天构造改造影响,探井之间差异非常大,但物性与TOC仍呈正相关;页岩垂向自封闭性及水平渗透率大的特性决定了页岩产状与断层发育是影响页岩含气性的主要因素,而页岩是否含气又影响了物性的大小。构造宽缓、断层不发育的含放射虫碳质笔石页岩,才能保持孔隙压力和孔隙大小,成为高TOC、高脆性、高孔隙度、高含气性的优质页岩储层,表现出四高三低的电性特征,才能形成商业产能。

Shale gas exploration in the Wufeng-Longmaxi formations in the southeastern Sichuan Basin showed different results. Some wells were high yielding, some were low yielding, and some were dry. Well core description, geochemical analysis, SEM, X-ray diffraction, field gas content tests, and well logging analysis were applied to compare samples from over 10 shale gas wells. Six properties were studied, including lithology, geochemical features, brittleness, physical properties, gas-bearing capacity, and electrical resistivity. Lithology, geochemical features, and brittleness show good correlation. For example, radiolarian carbonaceous graptolite shale has high TOC content and brittleness index. These three properties were controlled by sedimentary environment and facies, and can be compared among wells in the study area. Physical properties are positively correlated with gas-bearing capacity. They were affected by tectonic deformations, and vary obviously among wells. Physical properties are positively correlated with TOC content. Shale attitude and fault development are the main factors which affect gas content because the horizontal permeability of shale is several times larger than vertical permeability. Gas content also affected shale porosity and permeability. Radiolarian carbonaceous graptolite shales with few faults are favorable for the preservation of pressure and pores, and can form industrial reservoirs featured by high GR, high resistivity, relatively high AC, high U content, low KTH, low NGR, and low density.

中国石油化工集团公司科技项目(P13129)资助。

https://doi.org/10.11781/sysydz201603320