川西和川东北地区差异构造演化及其对陆相层系天然气成藏的影响

川西和川东北地区处于扬子地台西北缘，均具有褶皱冲断带-前陆盆地的二元结构，其构造特征具一定相似性。根据地震资料解释和典型气藏解剖，再结合前人研究成果，分析了川西和川东北地区构造演化差异性及其对各自成藏特征的影响，结果表明：川西地区主要受龙门山造山带影响，从印支期中晚期开始发育前陆盆地，之后主要受燕山中晚期和喜马拉雅期构造运动的影响；而川东北地区从燕山早期开始发育前陆盆地，之后在燕山中期和晚期受大巴山、米仓山和雪峰山联合作用影响，最后大巴山造山带在喜马拉雅期的强烈活动使其最终定型。上述差异构造演化对川西和川东北地区陆相层系的成藏特征的影响主要表现在4个方面：烃源岩的发育、输导体系的形成、气藏的保存和天然气成藏过程。川西地区主要发育须家河组烃源岩，形成了以NE向和SN向断裂及其伴生裂缝为主的输导体系，多期构造运动形成的大型通天断裂影响了山前断褶带气藏的保存，成藏经历了印支晚期、燕山中期、晚期和喜马拉雅期4个关键时刻。川东北地区发育须家河组和下侏罗统两套烃源岩，输导体系以NW向断裂为主，隆升剥蚀和大型断裂造成了山前断褶带较差的保存条件，成藏经历了燕山中期、燕山晚期和喜马拉雅期三个关键时刻。

Differential Structural Evolution and Its Influence on the Natural Gas Accumulation of Continental Strata in the Western and Northeastern Sichuan Basin

The west and northeast of Sichuan Basin, located at the northwestern margin of the Yangtze Platform,both developed typical fold thrust belts and foreland basins, and shared certain similarities in relate to structural characteristics. Based on the interpretation of seismic data and anatomy of typical gas fields and in combination with previous study results, this study analyzed differential structural evolution and its influence on natural gas accumulation characteristics in the west and northeast of Sichuan Basin. Consequently, the western Sichuan Basin was mainly affected by the Longmenshan orogenic belt and the corresponding foreland basin formed from the Middle and Late Indosinian,then mainly influenced by Late Yanshanian and Himalayan tectonic movement; but the northeastern Sichuan Basin from the Early Yanshanian began to develop foreland basin, then was influenced by the combination of Dabashan, Micangshan and Xuefengshan in the Middle and Late Yanshanian, finally formed in the intensive movement of Dabashan orogenic belt in the Himalayan. Above differential structural evolution affected the hydrocarbon accumulation characteristics in the continental strata of the west and northeast of Sichuan Basin respectively, which are reflected mainly in source rocks, pathway system, preservation condition and natural gas accumulation process. The western Sichuan Basin mainly developed Xujiahe Formation source rocks, and its pathway system consisted of NE and SN trending faults and relational fractures and its large faults formed by multi period tectonic movements affected the preservation of gas fields in piedmont fault fold zone, experiencing four key accumulation periods, ie Late Indosinian, Middle and Late Yanshanian and Himalayan. The northeastern Sichuan Basin developed two sets of source rocks,ieXujiahe Formation and Lower Jurassic, and its NW trending faults were the main pathway system, and its erosion and large faults caused poor preservation condition of piedmont fault fold belt, experiencing three key accumulation periods, ieMiddle Yanshanian,Late Yanshanian and Himalayan.