海陆过渡相高黏土含量微孔致密岩屑砂岩储层特征

Reservoir characteristics of high clay content and microporous tight litharenites in marine-continental transitional environments

刘曾勤 郭少斌

LIU Zengqin GUO Shaobin

中国地质大学(北京) 能源学院, 北京 100083

School of Energy Resources, China University of Geosciences, Beijing 100083, China

海陆过渡相地层中致密砂岩气、页岩气和煤层气的勘探开发前景十分广阔。过去的研究工作主要集中在海陆过渡相的页岩和煤层的地质和地球化学特征上，对其中的致密砂岩关注较少。以黔西地区海陆过渡相上二叠统龙潭组砂岩为例，利用薄片观察、压汞法、核磁共振实验等技术手段，综合分析龙潭组致密砂岩储层特征。龙潭组砂岩属于岩屑砂岩，典型储层特征包括砂体单层厚度薄，岩屑和黏土含量高，基本以微孔为主，孔喉结构复杂，孔隙度和渗透率非常低。与国内其他大规模开发的致密砂岩相比，龙潭组砂岩岩屑成分含量更高，孔喉结构更致密，致密砂岩气潜力比较有限。龙潭组砂岩与泥岩和煤层呈互层分布，致密砂岩气与页岩气和煤层气的合采方式是可行的，从而为海陆过渡相非常规气开发找到突破口。

The resource potentials for the exploration and development of tight sandstone gas, shale gas, and coalbed gas in marine-continental transitional environments are very attractive. However, previous studies have mostly focused on the geological and geochemical characteristics of marine-continental transitional shales and coals, and less attention has been paid to the associated tight sandstones. This paper takes the sandstones in the west Guizhou as an example. The Longtan marine-continental transitional tight sandstones have been investigated using various techniques (e.g., thin section, mercury injection capillary pressure, and nuclear magnetic resonance) to illustrate the reservoir characteristics. The Longtan sandstones, according to our study, are classified as litharenites, and are characterized by thin layers, high rock fragment and clay contents, abundant micropores, complex pore-throat structures, and low porosities and permeabilities. Compared with other typical tight sandstones in China, the Longtan sandstones have more lithic content and tighter pore throat structures. Therefore, tight-gas potential is interpreted to be limited in the Longtan sandstones. However, a model for the commingled production of tight-sand gas, shale gas and coalbed methane could be viable since the Longtan sandstones are interbedded with coals and shales, which provides an opportunity for unconventional gas development in marine-continental transitional environments.

国家科技重大专项“上古生界海陆过渡相页岩气赋存机理与富集规律研究” 2016ZX05034

https://doi.org/10.11781/sysydz202002223