四川盆地下寒武统九老洞组页岩气勘探

Shale Gas Exploration in Jiulaodong Formation of Lower Cambrian, Sichuan Basin

四川盆地下寒武统九老洞组岩性主要为暗色页岩夹粉、细砂岩等,特别是盆地西部厚度大、有机质丰富、生气强度大,以往一直都只认为是一很好的生油层。近年来由于页岩气理念的引入,开始认识到页岩既是生油层,也是储层,有粉、细砂岩、甚至砂岩夹层的参与,可使已生成的天然气在气源层就近聚集成藏。经过对全盆地九老洞组泥页岩在以往研究的基础上,进一步研究其天然气的形成与演化、运移和成藏后,认为勘探的有利区块主要是威远区块,其生气强度达230×108m3/km2,紧邻其下的震旦系灯影组也是一生油层并不断地供应其天然气,且其上覆间接盖层奥陶系—志留系的泥页岩封盖良好。其次是盆地北部川陕边境的南江区块,生气强度达(30～60)×108m3/km2,该区块地面已出露九老洞组岩层,其最大特点是埋藏浅,投资小,既省人力、物力和时间,而且验证也快。

Lithology of Jiulaodong Formation in Lower Cambrian, Sichuan Basin is mainly dark shale mixed with siltsone and fine sandstone. In particular, the western part of the Basin which features in big thickness, abundant organic matter and high gas generating intensity has always been regarded as a good source bed. In recent years, due to the introduction of the concept of shale gas, people began to realize that shale was not only oil source bed, but also reservoir, involving the participation of siltstone, fine sandstone and even interbedded sand, which could make the generated gas accumulate and form reservoir at source bed. Based on previous research on clay shale of Jiulaodong Formation, the author further studied the formation and evolution, migration and reservoir formation of natural gas here, and believed that the block favorable for exploration was mainly Block Weiyuan of which the gas generating intensity reached 23 billion cubic meters per square kilometer, the Deying Formation of Sinian system was also a source bed and supplied natural gas continuously, and the mud shale of Ordovician -Silurian was sealed well. Second is Block Nanjiang located at the border of Sichuan and Shaanxi, with the intensity of gas generation between 3 and 6 billion cubic meters per square kilometer. Rock of Jiulaodong Formation has shown in the block, which features in shallow burial depth and low cost. It does not only save labor power, material resources and time, but also fast to be verified.