四川盆地西部侏罗系天然气成藏特征

CHARACTERISTICS OF FORMING JURASSIC GAS RESERVOIRS IN THE WEST PART OF SICHUAN BASIN

四川盆地西部侏罗系为一套以河流相沉积为主的砂泥岩系 ,厚 2 0 0 0～ 30 0 0m ,天然气资源十分丰富。现已发现 6个气田 (藏 )、15个含气构造 ,天然气地质储量近 15 0 0× 10 8m3 ,已成为川西地区目前最重要的勘探层系。通过对侏罗系典型气藏的剖析以及对侏罗系天然气成藏条件的分析 ,认为侏罗系气藏的形成应具备以下几方面地质条件的有利配置 ,即充足的气源条件、储集条件良好的砂体分布、发育的气源断裂和裂缝系统以及一定规模的圈闭条件和良好的保存条件。进而指出 ,侏罗系诸成藏条件配置有利的什邡—蒲江中央凹陷带、孝泉—丰谷镇隆起构造带及鸭子河—平落坝隐伏断褶带 ,具有寻找大。

The Jurassic in the west part of Sichuan Basin is composed of a series of sandstones and mudstones of fluvial fades with thickness of 2 000-3 000m, being rich in natural gas resources. Currently, in the Jurassic in the region, 6 gas fields(reservoirs) and 15 gas-bearing structures have been found and gas in place is near 1 500 × 108m3. It has become the most important exploration strata in West Sichuan at present. Through analyzing the typical Jurassic gas reservoir and the conditions of forming Jurassic gas reservoirs, it is thought that the Jurassic gas reservoir formation should be of a favourable disposition of the following geological conditions, as adequate gas source, sandbodies with good reservoir quality, developed gas-source faults and fracture systems, traps with a certain scale and fair preservation circumstances. Finally, it is also pointed out that some regions, where the disposition of the geological conditions of forming Jurassic gas reservoirs is good, as Shifang-Pujiang Central Depression Zone, Xiaoquan-Fengguzhen Uplift Structural Zone and Yazihe-Pingluoba Buried Fault-fold Zone, are of wide prospects for surveying large- and medium-sized gas fields.