银额盆地形成演化及油气勘探展望

银额盆地位于内蒙古自治区中西部，面积约12.3×10⁴ km²，是中国北方勘探程度较低的陆相断陷盆地。由于受地表、地下双复杂条件影响，早期仅在盆地周边的查干、天草、哈日等凹陷开展了地质特征研究，证实各凹陷具备油气成藏条件，但整体勘探潜力较低。近年来，在前人研究基础上，结合多期野外地质调查、地震、钻井等资料，对盆地的形成演化和资源潜力进行了重新评价，提出银额盆地基底形成于二叠纪末期—三叠纪早期，岩性主要为增生—碰撞混杂岩，普遍发生了中—浅变质；中生代以来，受燕山运动、喜马拉雅运动影响，历经6期构造演化，具有残留、改造盆地特征。残留的下白垩统巴音戈壁组主要分布于盆地中北部，是主要生烃、成藏层系，评价盆地石油地质资源量约为13.64×10⁸ t。受晚期强烈改造因素影响，保存条件是油气成藏的关键因素，盆地北部的构造活动相对较弱，洼陷区内存留巴音戈壁组有效烃源岩，是超压油气藏的发育区，成为下步勘探的重点领域。

Formation and evolution of Yin'gen-E'ji'naqi Basin and prospects for oil and gas exploration

The Yin'gen-E'ji'naqi Basin is located in the central and western part of the Inner Mongolia autonomous region, with an area of about 123×103 km2. It is a continental rift basin with a low exploration degree in North China. Due to the influence of complex surface and underground conditions, only the geological characteristics of the Chagan, Tiancao, Hari and other sags around the basin were studied during the early stage, which proved that each sag had the conditions for oil and gas accumulation, but the overall exploration potential was low. In recent years, on the basis of previous studies and combined with more field geology surveys, seismic and drilling data, the formation and evolution of the basin and the resource potential were re-evaluated. The Yin'gen-E'ji'naqi Basin basement was formed from the end of Permian to the Early Triassic, mainly composed of accretion-collision mélange, with moderate-shallow metamorphism generally occurring. Since the Mesozoic, affected by the Yanshanian and Himalayan movements, the basin has undergone six stages of structural evolution, with the characteristics of residual and reformed basins. The remaining Lower Cretaceous Bayin Gobi Formation is mainly distributed in the central and northern part of the basin, and is the main hydrocarbon generation and reservoir system. The total resources of the basin are estimated to be about 1.364 billion tons. Under the influence of strong late transformations, preservation conditions are the key factors for hydrocarbon accumulation. The tectonic activities in the northern part of the basin are relatively weak, and the effective source rocks in Bayin Gobi Formation remain in the depression area, which is the development area of overpressure oil and gas reservoirs and has become the key area for further exploration.