四川盆地西部中二叠统茅口组油气地质条件及勘探潜力

四川盆地西部中二叠统茅口组为碳酸盐岩浅水缓坡相沉积,高能浅滩亚相颗粒岩发育。茅口组沉积末期,研究区古表生岩溶作用强烈,有利于岩溶储层发育。中二叠统发育栖霞组和茅口组碳酸盐岩、梁山组泥质岩等多套烃源岩,烃源岩厚度大,品质较好;各套烃源岩从中三叠世末起相继达到生烃高峰,资源潜力大。茅口组中上部发育两类储层:裂缝-孔洞型(或裂缝型)储层和白云岩孔隙型储层。钻井及露头剖面揭示茅口组含气性好。高能滩相沉积区与岩溶斜坡带叠合区是茅口组储层发育的有利地区。茅口组之上的区域盖层发育,保存条件好。认为川西地区茅口组具有良好的天然气勘探前景。

Petroleum Geology Conditions and Exploration Potential of Middle Permian Maokou Carbonate Rock in Western Part of Sichuan Basin

High- energy shoal subfacies grainstone widely develops in Middle Permian Maokou carbonate shallow gentle slope in the western part of Sichuan Basin. Effected by Dongwu uplifted movement, karstic reservoirs developed in this region due to intensive hypergenic karstification at the end of Maokou age. Several sets of thick and good source rocks, such as Middle Permian Qixia and Maokou carbonate rocks, and thick Liangshan mudstone rock, developed during Middle Permian epoch. Every set of source rocks reached to the fastigium of hydrocarbon generation in succession and supplied great hydrocarbon potential. Two types of reservoirs develop in the middle to upper parts of Maokou Formation, one is fractures-void (or fractured) and another is dolostone pore. Drilling and outcrop data reveal both of them are of good gas-bearing potential. The favorable exploration area is in the superimposed zone of high-energy shoal with palaeokarst slope. The preservation condition is good due to the widely developing regional cap rock. It is deemed that there is good gas prospecting in Maokou Formation.