中国中西部前陆盆地成藏特征的初步分析

通过讨论川西(四川盆地西部)、柴北缘(柴达木盆地北缘)和准南缘(准噶尔盆地南缘)前陆盆地的成藏过程,指出我国中西部前陆盆地具有多期聚集、晚期聚气的成藏特征,认为我国中西部前陆盆地具有最重要的两大成藏期,一是燕山期及其之前的油气成藏期,主要是中部周缘前陆盆地和西部再生前陆盆地二叠系烃源岩和三叠系烃源岩的油气聚集期;二是喜山晚期,主要是受新构造运动影响,西部再生前陆盆地中、新生界烃源岩的油气成藏和中部周缘前陆盆地的油气调整期,其中中生界煤系烃源岩是中西部前陆盆地主要的烃源岩,而喜山晚期冲断作用形成的断层相关褶皱圈闭与前陆发育时巨厚沉积造成的中生界煤系烃源岩排烃过程相匹配。此外还讨论了前陆盆地中的古构造(背景)在油气聚集中的重要作用和早期前陆盆地成藏体系、再生前陆盆地成藏体系在油气相态及成因类型的平面分布特征上的控制作用。

THE PRIMARY STUDY ON THE FORMATION OF OIL AND GAS FIELDS IN THE FORELAND BASINS IN CENTRAL AND WESTERN CHINA

The paper analyzes the hydrocarbon accumulation of gas pools in the western Sichuan foreland basin, northern Qaidam thrust and southern Junggar foreland basin. It indicates that the oil-gas fields were formed by multi-stage filling and that the gas pools accumulated in the late stages of the foreland basins. There were two most important stages for oil-gas accumulation in the foreland basins of central and western China, one was the Late Yanshanian movement when oil and gas accumulated mainly from Permian and Triassic source rocks of peripheral foreland basins in central China and rejuvenated foreland basins in western China, another during the Late Himalayan movement when oil and gas mainly from Meso-Cenozoic source rocks of rejuvenated foreland basins in western China and accumulated secondarily in gas fields of peripheral foreland basins in central China, affecting by neotectonic movement. The main source rock of foreland basins in central and western China is Mesozoic coal measure. They were matched for fault related fold cloures formed by thrusting and expulsion process from Mesozoic coal measure by much very thick sedimentation due to foreland development in Late Himalayan movement. In addition, it is concluded that the palaeostructure or palaeohigh was very important in hydrocarbon accumulation in forland basins and that the hydrocarbon distribution in phase state and genesis type was controlled by oilgas filling systems of early forland basins and late rejuvenated forelad basins.