银根-额济纳旗盆地烃源岩特征及油气富集规律

基于对银根-额济纳旗盆地上古生界、侏罗系和白垩系烃源岩地球化学特征的系统评价，分析了盆地内各凹陷的油气来源和富集规律。盆地上古生界石炭系—二叠系暗色泥岩整体已达到过成熟阶段，中生界凹陷内已发生浅变质—变质作用，油气保存条件较差，油气资源和勘探潜力小；中—下侏罗统发育一套煤系烃源岩，在盆地腹部及南部凹陷中已达成熟阶段，具有一定生烃潜力；白垩系巴音戈壁组烃源岩的有机质丰度高、类型较好，是盆地的主力烃源岩层系，且油源对比结果证实，盆地已发现的油气均来源于该套烃源岩。银根-额济纳旗盆地的油气成藏过程可划分为早白垩世晚期油气成藏和早白垩世末期调整改造2个阶段，油气的富集主要受巴音戈壁组烃源岩的热演化程度和晚期构造活动强度共同控制。银根-额济纳旗盆地腹部是其油气富集的最有利区，中西部是油气勘探的有利区，中东部的油气成藏条件较差。

Characteristics of source rocks and enrichment laws of hydrocarbons in Yin'gen-Ejinaqi Basin

Based on systematically evaluating the geochemical characteristics of the Upper Paleozoic, Jurassic and Cretaceous source rocks in Yin'gen-Ejinaqi Basin, this paper analyzes the oil and gas sources and enrichment laws of sags in the basin. The Upper Paleozoic Carboniferous-Permian dark mudstone in the basin has reached the over-mature stage as a whole, and epimetamorphism and metamorphism had occurred in the Mesozoic inside the sag, leading to poor oil and gas preservation conditions, and less hydrocarbon resources and low exploration potential. A set of Middle-Lower Jurassic coal-measure source rocks are developed in the basin and has reached the mature stage in the central basin and the southern sag, with certain hydrocarbon potential. The source rocks of the Cretaceous Bayingebi Formation have good types of organic matter with high abundance, and they are the main source rock strata in the basin. The oil-source correlation results confirm that all the oil and gas discovered in the basin originate from this set of source rocks. The hydrocarbon accumulation process in Yin'gen-Ejinaqi Basin can be divided into two stages:hydrocarbon accumulation in the Late Early Cretaceous, adjustment and reconstruction in the Late Early Cretaceous. The hydrocarbon enrichment is mainly controlled by the thermal evolution of the Bayingebi Formation source rocks and the intensity of late tectonic activities. The hinterland of Yin'gen-Ejinaqi Basin is the most favorable area for hydrocarbon enrichment, the central-western area is favorable for oil-gas exploration, and oil and gas accumulation conditions are poor in the central-eastern area.