东濮凹陷天然气成藏及富集规律

Patterns of natural gas accumulation and enrichment in Dongpu depression

东濮凹陷是中国少有的几个既富含油又富含气的盆地(凹陷)之一。由于发育古生界和新生界两套烃源岩,今埋深大、热演化程度高;经历了复杂的埋藏史、热史和生烃史;发育以盐岩为代表的好的盖层;有多种类型砂体,具备良好的储集条件;圈闭类型多、圈闭形成与生烃时间配置好;部分地区发育异常高压;以及“两洼一隆一斜坡”的构造格局有利于天然气的运移聚集。发育煤成气、凝析气和混合气3种气藏类型。区内天然气资源丰富。煤成气藏主要聚集于中央隆起带顶部,凝析气藏主要富集在环洼地区,混合气藏分布于煤成气藏和凝析气藏之间。

Dongpu depression is one of the few basins in China that are abundant with both oil and gas. Two sets of Paleozoic and Cenozoic source rocks, with deep burial depth and high thermal maturity, have gone through complicate history of bury, thermal evolution, and hydrocarbon generation. Good cap rocks represented by halite are well developed. Various types of sandbodies provide the depression with favorable accumulation conditions. Traps in the depression are of various types and the timing of their formation and hydrocarbon generation is ideal. Furthermore, the structural framework （ two sags, one uplift, and one slope） of the depression and the abnormal high pressure in some part of the depression make it a favorable place for the migration and accumulation of hydrocarbon. Three types of gas reservoirs, including coal-derived gas, condensate gas and mixed gas, are recognized in the depression. The coal-derived gas reservoirs mainly occur in the top of central uplifts, condensate gas reservoirs mainly occur around the sags, and the mixed gas reservoirs are distributed in between.