四川盆地西北部前陆盆地构造演化对古生界海相油气成藏的影响

针对四川盆地西北部古生界海相油气成藏的复杂性和平面分带性，研究梳理了古生界油气成藏特征，探讨了不同构造背景下油气聚集的差异化特征，揭示了前陆盆地构造演化对古生界海相油气成藏的影响。研究认为四川盆地西北部地区前陆盆地构造运动在纵向上促进了古生界烃源岩的热演化进入高成熟—过成熟阶段，在横向上对逆冲推覆带—坳陷带烃源岩热演化具有一定的延迟效应。前陆盆地构造深埋作用造成储层具有低孔低渗特征，挤压运动使储层孔隙度呈现逐渐降低的趋势。逆冲断裂破坏了前陆冲断带地区盖层的封盖能力，降低了圈闭的有效性，前缘隐伏带和坳陷带发育断块圈闭和构造—岩性圈闭，保存条件较好。综合分析认为逆冲推覆带受不整合面—断层疏导体系影响，古生界油气藏具有“早油晚气、后期调整、保存控藏”的特征，前缘隐伏带受渗透层—断层组合的阶梯状疏导体系控制，具有“多源充注、多期运聚、通源断裂控藏”成藏特征，而坳陷带主要受层间断裂垂向疏导体系控制，气藏具有“近源充注、持续供烃、层间断裂控藏”成藏特征。综合分析认为，前缘隐伏带是川西海相深层油气突破的有利地区。

Influence of tectonic evolution of foreland basin in northwestern Sichuan Basin on Paleozoic marine hydrocarbon accumulation

Aim to the complexity and zonality of Paleozoic marine hydrocarbon accumulation caused by foreland basin tectonic in northwestern Sichuan Basin, the influence and differential characteristics of foreland basin tectonic evolution on Paleozoic marine hydrocarbon accumulation are analyzed from the perspective of reservoir forming conditions. It is supposed that the foreland basin structure in western Sichuan Basin longitudinally promoted the thermal evolution of the Paleozoic source rocks into the high-mature and over-mature stage. Laterally, there was a delay effect on the source rocks in the thrust belt and depression zone. The reservoir with characteristics of low porosity and permeability was caused by foreland basin squeezing action, and the porosity of the reservoir conforms to the compaction law. And the uplift destroyed the capping ability of the cover in the foreland thrust belt, reduced the effectiveness of traps, and fault block traps and tectonic-lithologic traps are developed in an area covering the front of thrust belt, and the preserve condition are well. The Paleozoic oil and gas accumulation in the study area has obvious zonation, in which the foreland thrust nappe belt affected by lateral migration system has the characteristics of late adjustment of early oil to gas, and reservoir controlled by preservation. The area in front of thrust belt is affected by stage migration system of permeable bed-fault, with characteristics of multi-source injection, multi-period migration and accumulation, and reservoir controlled by source faults. The depression zone is characterized by near source injection, continuous hydrocarbon supply, and reservoir controlled by vertical migration system of intraformational faults. The comprehensive analysis shows that the area in front of thrust belt is a favorable hydrocarbon accumulation area of Paleozoic marine formation.