中国中西部前陆冲断带油气分布规律及勘探领域

摘要

环青藏高原中西部前陆冲断带相继发现了克拉玛依、克拉2、英东、中坝、白马庙等大型油气田.深入对比分析前陆冲断带构造特征及其与油气关系,总结了中西部前陆冲断带油气分布规律和勘探领域:沿走向,前陆冲断带一般划分为3个大的构造段,中段位于生烃中心,油气富集;从山前到盆内,前陆冲断带划分为山前推覆带、下盘掩伏带、盆内晚期构造带3个油气富集区带,山前推覆带稳定区继承性古构造油气富集,下盘掩伏带和盆内晚期构造带油气近源、近断裂成藏,深层油气富集;前陆冲断带以构造油气藏为主,除此之外,山前推覆带发育基岩风化壳、不整合遮挡等地层油气藏,盆内晚期构造带发育构造-岩性复合油气藏.根据前陆冲断带中段和深层油气富集规律及对三大勘探领域的认识,结合准噶尔盆地南缘前陆冲断带勘探现状,明确下一步勘探领域为南缘中段齐古断褶带及乌奎背斜带下部组合.%Large-scale oil and gas fields such as Karamay,Kela-2,Yingdong,Zhongba and Baimamiao have been discovered in the foreland thrust belts around the Qinghai-Tibet Plateau of Midwest China.The paper analyzes and compares the structural characteristics of the foreland thrust belts and its relationship with oil and gas,and summerizes the petroleum distribution in the foreland thrust belts and its exploration areas in the Midwest China.Along the strike,the foreland thrust belt is generally divided into three large structural segments—the mid-segment of the foreland thrust belt is located in the hydrocarbon generation center with enriched oil and gas;from the piedmont area into basin,the foreland thrust belt can be divided into three hydrocarbon enrichment zones such as piedmont nappe belt,footwall covered structure and late inner-basin tectonic belt.Oil and gas accumulated in the paleostructures in the piedmont nappe belt.The footwall covered structure and the late inner-basin tectonic belt are characterized by hydrocarbon accumulation in the near-source and near-fracture areas and oil and gas enrichment in the deep strata.The foreland thrust belt is dominated by structural reservoirs.Additionally,stratigraphic reservoirs such as base rock weathering crust and unconformity barrier are developed in the piedmont nappe belt,and structural-lithological reservoirs are developed in the late inner-basin tectonic belt.Based on the understanding of the petroleum enrichment regularity and the three major exploration fields in the middle and deep of the foreland thrust belt,and combined with the exploration status of the foreland thrust belt in southern margin of Junggar basin,the areas for further exploration are defined as the Qigu fault-fold zone and the lower assemblage in the Wukui anticline zone in the middle segment of the southern margin.