塔里木盆地巴-麦地区古生界油气盖层动态演化评价

为实现动态评价经历过多旋回构造变动的海相油气盖层,基于塔里木盆地古生界大量盖层样品的实验测试结果和盖层空间分布特征分析,以地质演化为主线,综合考虑其宏观变化、物性演化、应力应变特征,探讨和重建自形成至今其封盖性能的演化过程.结果显示,巴-麦地区多期差异隆-拗演变对盖层封盖性能演化具有明显控制作用.在海西晚期,大部分地区石炭系泥岩盖层具有封油能力.但因差异抬升,埋深浅于2 100 m的西北区域为差盖层区.之后,石炭系泥岩盖层封盖性能在西北部不断变差,东南部变好.中-下寒武统膏盐岩盖层在早奥陶世开始具备封油能力.玉北地区西南部,在海西早期因埋深浅于其封闭能力形成的初始埋深1 230 m而评价为差盖层区.结合其他油气成藏条件,提出了石炭系巴楚组泥岩是重要的区域性盖层,多套盖层对油气聚集起控制作用.麦盖提斜坡、巴楚南缘构造带及隆起大型断裂带间的区域是油气好保存区.

Dynamic evolution assessment of the Paleozoic hydrocarbon cap rocks in Bachu-Magati area,Tarim Basin

With the aim of assessing the dynamic evolution of marine hydrocarbon cap rocks experienced multi-cycle tectonic movements, the Paleozoic in the Tarim Basin was taken for case study. Based on the experimental test results of large amount of cap rock samples, this paper reconstructed the evolutionary process of its sealing capability by taking geological evolution as a clue and in combination with its macroscopic change, physical property evolution and stress variation. The results show that the polyphase burial changes due to uplift-depression conversion obviously controlled the sea-ling property of cap rock. Most of the Carboniferous mudstone caps had good sealing capacity in the late Hercynian in most areas except for the northwestern part where the burial depth of cap rocks was less than 2100m due to differential uplifting. Later, the sealing capacity of the Carboniferous mudstone deteriorated in the northwestern part, but enhanced in the eastern and southern parts. Salt-gypsum rocks in the Middle and Lower Cambrian established their sealing capacity in the Early Ordovician, but it became ineffective in the southwest of Yubei area where its burial depth was less than 1230m in the early Hercynian. The Carboniferous mudstone caps were regarded as the most important regional seal. Magiati slop, structural belt at the southern margin of Bachu uplift and stable area between large fault zones are the favorable areas for oil and gas preservation.