西昌盆地上三叠统白果湾组富有机质泥页岩沉积岩相古地理与孔隙特征

Sedimentary lithofacies paleogeography and pore characteristics of the organic-rich mud shale of the upper Triassic Baiguwan Formation in Xichang basin

海陆过渡相富有机质泥页岩是页岩气勘查开发的重要领域。本文以西昌盆地上三叠统白果湾组富有机质泥页岩为研究对象,对研究区内富有机质泥页岩的沉积岩相古地理特征、微观孔隙类型、孔隙结构特征进行研究。白果湾组富有机质泥页岩段沉积相主要为湖泊相、三角洲相、河流相。发育不同类型的微孔隙,孔隙主要以小孔为主,微孔次之,平均孔径分布在5.56-56.89nm之间,比表面积平均为9.44m^2/g,总孔体积平均为0.0187cm^3/g。页岩气主要形成于滨浅湖亚相及半深湖亚相中,并主要吸附于富有机质泥页岩的小孔、微孔内;西昌盆地白果湾组富有机质泥页岩储集空间较好,具有良好的勘探潜力。

Organic-rich mud shale in transitional facies is an important target for shale gas exploration.In this paper, the paleogeographic features, micro-pore types and pore structures of the organic-rich mud shale of the Upper Triassic Baiguowan Formation in Xichang Basin were studied.Lake facies and delta facies are the main sedimentary facies of organic-rich mud shale in the Baiguowan Formation. Small pores, which are dominant, followed by micropores, occurred in the organic-rich mud shale in the Baiguowan Formation. The average pore size was between 5.56 nm and 56.89 nm, the average specific surface area was 9.44 m^2/g, and the average total pore volume was 0.0187 cm^3/g. Shale gas was mainly formed in shore-shallow lake subfacies and semi-deep lake subfacies, and mainly adsorbed in the small pores and micropores of the organic-rich mud shale. In general, the organic-rich mud shale of the Baiguowan Formation in Xichang basin is potential for exploration of shale gas.