蜀南地区须家河组天然气赋存地质条件

GEOLOGIC CONDITIONS OF GAS RESERVOIRING IN XUJIAHE FM IN SOUTH SICHUAN

上三叠统须家河组是四川盆地的主要烃源岩层和勘探目的层之一,对四川盆地须家河组天然气储集特征和成藏规律的认识也取得了很大进展,但针对蜀南地区须家河组天然气赋存地质条件的研究不多。该地区上三叠统须家河组可供勘探面积大,以此作为目的层的探井少,研究程度低。文章分析了蜀南地区须家河组烃源岩母质类型与生成时期、储层主要发育层位与控制因素、圈闭、保存条件及它们之间的匹配关系,搞清了影响蜀南地区须家河组天然气赋存的各项地质因素。认为蜀南地区油气来源较为充足、有利储层广泛存在、裂缝发育程度较高、盖层条件良好;圈闭的生储盖组合良好,烃源区油气大量生成时间、运移时间与圈闭形成时间和构造改造配套,具有良好的成藏地质条件,有望获得较好的勘探效果,这为蜀南地区须家河组下一步勘探工作提供了依据。

The Upper Triassic Xujiahe Formation is one of the major source rocks and exploration targets in Sichuan basin. Much knowledge has been achieved in respect of the characteristics of gas accumulation and reservoiring patterns of Xujiahe Formation in Sichuan basin, while few study have been performed on the geologic conditions of gas reservoiring in Xujiahe Formation in South Sichuan. Though much of the Upper Triassic Xujiahe Formation in this area has considerable exploration potentials, it has seldom been targeted by exploration wells, thus our understanding of this interval is very limited. This paper analyzes the kerogen types and hydrocarbon generating periods of source rocks, the main development horizons and controlling factors of reservoirs, trapping and preservation conditions, as well as their assemblage in Xujiahe Formation in South Sichuan. The various geologic factors that have controlled gas accumulation in the Xujiahe Formation in South Sichuan are recognized. It is believed that South Sichuan has relatively rich source rocks, extensive favorable reservoirs, well-developed fractures, good sealing conditions and favorable source-reservoir-cap rock combination. The timing of peak hydrocarbon generation, migration, trap formation and tectonic reworking is favorable and the geologic conditions of gas reservoiring are good. Therefore, exploration in this area is expected to be fruitful. This study provides a reliable basis for future exploration of the Xujiahe Formation in South Sichuan.