四川盆地川中地区须家河组天然气大面积成藏的主控因素

Controlling factors for massive accumulation of natural gas in the Xujiahe Formation in central Sichuan Basin

卞从胜 王红军 汪泽成 李永新 朱如凯 刘柳红

Bian Congsheng Wang Hongjun Wang Zecheng Li Yongxin Zhu Rukai Liu Liuhong

川中三叠系须家河组地层具有砂泥岩交互、大面积分布的特征,已发现的广安、合川、八角场等大型气田以及充西等含气构造。这套含气组合平面上分布于川中地区各个不同的构造区域,纵向上各储层段交互发育。它们成藏背景相似,但又相互独立,互不连通,表现为大面积成藏的地质特征。通过对须家河组成藏地质特征的深入分析认为,大面积成藏的主控因素包括:①平缓构造背景下,大型开放式浅水湖盆广泛发育煤系与砂岩的交互组合,是大面积成藏的基础;②优质储层的广泛分布,是大面积成藏的重要条件,主要受早印支期古构造、沉积微相以及裂缝的联合控制;③白垩纪末盆地的整体抬升,天然气发生膨胀排烃以及储层的分隔化对气藏的保存作用是大面积成藏的重要机制。

The Triassic Xujiahe Formation(Tχ) in central Sichuan Basin features in interbeded sandstone and mudstone and extensive distribution.Many gas fields(e.g.,Guang'an,Hechuan and Bajiaochang) and gas-bearing structures(e.g.,Chongxi) have been found in this formation.Horizontally,this gas-bearing combination is distributed in different structural zones;vertically,it has many alternating intervals of reservoirs.These reservoirs have similar pooling settings,but they are separated from each other with no communication.According to the analyses of geological features for gas accumulation in Tχ,the main factors controlling massive gas accumulation are considered as the followings:1)development of alternating coal bed and sandstone combinations in a large open shallow-water lacustrine basin under gentle structural settings;2)the wide distribution of quality re-servoirs under the joint control of paleotectonics,sedimentary micro-facies and fractures in the Indo-Chinese epoch;3)overall uplifting of the Sichuan Basin at the end of the Cretaceous,gas expulsion through expansion,and reservoir compartmentalization.

10.11743/ogg20090504