下扬子地区海相盆地演化及油气勘探选区评价

从晚震旦世开始至中三叠世,下扬子地区沉积了三套巨厚的海相烃源岩系(Z2-O3、C-P、T1).三套烃源岩热演化特点不同,下古生界烃源岩经历了加里东、印支-燕山期构造阶段的热演化(已达过成熟干气阶段);上古生界烃源岩基本处于生油阶段晚期;三叠系大部烃源岩处于成熟生油阶段,少数处于未成熟阶段.区内下古生界烃源岩经历了两次成油过程,即加里东运动前的盆地沉降阶段和加里东运动后晚古生代陆表海沉积阶段.海相油气储盖条件发育,配置有利,经多年油气勘探证实,下古生界油气勘探应立足于苏北地区;上古生界油气勘探除苏北地区外,尚有皖南与浙西地区.中生界海相油气勘探应集中在几个发育较好的中生代盆地,如常州、句容、无为、望江等盆地.

Evolution of Marine Basins and Exploration Direction Estimation of Oil and Gas in Lower Yangtze Areas

Starting from Late Sinian Epoch to Middle Trassic Epoch, three sets of hydrocarbon source rock series of huge depth (Z 2-O 3,C-P,T 1) were deposited in Lower Yangtze Areas. It is different for the thermal evolution characteristics of the three sets of hydrogen source rocks:the rocks of Lower Palaeozoic erathem underwent a thermal evolution of Caledonian, Indosinian and Yanshanian orogenic stages (beyond maturate dry gas stage); the rocks of Upper Palaeozoic erathem were in a late period of oil-producing stage; most of the rocks in Triassic System were in a maturate oil-producing stage, with a small amounts in an immaturate stage. In the studied area, the rocks in Lower Palaeozoic erathem experienced two courses of oil-genesis:that is basin subsidence stage of pre-Caledonian orogenesis and epicontinental sea sedimentation of Late Palaeozoic era of post-Caledonian orogenesis. The capping layers of marine oil and gas are well developed and favorably distributed. Through years of practice, Subei area has been proved to be the very place for oil and gas exploration of Lower Palaeozoic erathem and Upper Palaeozoic erathem as well as some of the areas in south Anhui and west Zhejiang. The oil and gas exploration in Mesozoic erathem should be focused in Mesozoic basins of fine development, for example, the basins of Changzhou, Jurong, Wuwei and Wangjiang, etc.