川南地区下古生界海相页岩微观储集空间类型

Microscopic space types of Lower Paleozoic marine shale in southern Sichuan Basin

关键词:  下古生界页岩  微观储集空间  成因类型  页岩气  川南地区

Key words:  Lower Paleozoic shale  microscopic space types  genetic type  shale gas  southern Sichuan Basin

摘要:

为探明不同成因的孔隙对页岩气储集的贡献,基于多种分析测试手段,对川南地区下古生界海相页岩微孔类型与分布、孔隙定量表征进行研究,并探讨页岩中微观储集空间的成因及影响因素。结果表明:下古生界页岩微观储集空间分为矿物基质孔、有机孔和微裂缝3大类,并可进一步细分为9种类型;龙马溪组页岩主要发育有机质孔和黏土矿物层间孔,五峰组页岩主要发育有机质孔和溶蚀孔、缝,九老洞组页岩有机质孔极少,多见溶蚀孔、缝;下古生界3套页岩孔隙类型与分布特征的差异与矿物组成、有机质丰度和成岩演化作用有关;龙马溪组底部页岩微孔发育,比表面积大,为页岩气的吸附提供大量储集空间,是有利的页岩储层发育段。

Abstract:

To ascertain the contribution of different pores to shale gas reservoir, pore types, size and distribution of Lower Paleozoic marine shale in southern Sichuan Basin were studied using a variety of analytical testing methods. Pore space characteristics and influencing factors were discussed. The results show that Lower Paleozoic shale reservoir space can be divided into three main types, including mineral matrix pores, organic pores and micro-fractures, and can be further subdivided into nine types. Organic pores and interlayer pores between clay minerals are mainly developed in Longmaxi shale. Organic pores, dissolution pores and fractures are mainly developed in Wufeng shale. Organic pores are rarely in Jiulaodong shale, where dissolution pores and fractures are well distributed. Pore types and distributions show differences in Lower Paleozoic shales, which are mainly affected by mineral composition, the abundance of organic matter and diagenetic evolution. Micro-pores are developed in Lower Longmaxi shale, with high specific surface area, providing a bulk of reservoir spaces for shale gas adsorption, which makes it a beneficial shale reservoir.