【摘要】 准噶尔盆地玛湖富烃凹陷下三叠统百口泉组新近发现了我国首个源上大面积连续型砂砾岩油藏群,是对全球"连续型"油气藏研究的新补充,但其成藏机理和模式并不很清楚。为加强对其的理论认识,并为下步勘探提供参考,基于油气生、储、盖、圈、运、保等基础石油地质条件,并结合油气藏特征,进行了成藏条件与成藏模式的综合研究。结果表明,优质充足的下二叠统风城组碱湖油气来源、规模有效的扇三角洲前缘砂砾岩储层、多重组合的扇三角洲平原致密砾岩、泥岩和断裂封盖保存、沟通良好的高角度断裂输导体系、平缓连续的构造背景奠定了大面积连续成藏的地质基础。在此背景下,高成熟的风城组所生成油气,在切穿烃源灶和储层的高角度压扭性断裂沟通下,优先充注物性相对好的扇三角洲前缘水下河道砂岩和砂质细砾岩,并且在地层异常高压促进下,控制着油气富集程度,使得油气成藏表现为大型缓坡浅水扇三角洲沉积控制下的源上扇-断-压三控大面积"连续型"。百口泉组油气藏具有的油质轻且含气、微裂缝广泛发育,以及异常高压等,决定了砾岩储层虽总体低孔低渗,但依旧能够高产。在油源断裂沟通的斜坡区上倾方向,叠合地层异常高压以及扇三角洲前缘水下河道砂砾岩的区域是下步有利勘探方向。更多还原

【Abstract】 The first large-area continuous petroleum(oil) reservoirs, which was recently discovered in the Lower Triassic Baikouquan Formation of the petroliferous Mahu sag, Junggar Basin, northwestern China, is an important supplement to the study of continuous hydrocarbon reservoirs globally. However, the reservoir forming mechanism and relevant accumulation model have not been well constrained. To improve the understanding of these issues and provide some references for theoretical study and exploration, this study investigated hydrocarbon accumulation conditions and related models based on the basic petroleum geological conditions, i.e., source rock, reservoir rock, cap rock, trap, migration and preservation, along with the reservoir characteristics. Results show that multiple factors provide favorable geological conditions for these large-area continuous oil accumulations, including sufficient oil and high-quality gas sources generated from the lower Permian Fengcheng Formation, effective and large-scale fan delta-front sandy conglomerate reservoirs, multiple blocks for sealing and preservation composed of tight conglomerates and mudstones in the delta plain and the closed faults, good migration systems of high-angle faults, as well as relatively smooth and continuous structural background. In these favorable conditions, high maturity oil and gas generated from the Fengcheng Formation entered the underwater channel sandstones and sandy conglomerates of relatively good physical property along the high-angle shear faults between hydrocarbon sources and reservoirs. These factors control the oil enrichment level, and the hydrocarbon accumulation in the study area is dominated by triple controls, including fan delta, faults, as well as high reservoir pressure, forming fan-fault-pressure-controlling continuous hydrocarbon accumulation in the large-scale gentle slope fan delta system deposited in shallow water. The Baikouquan Formation reservoirs have the characteristics of light oil containing gas, wide occurrence of micro cracks and abnormal high pressure. These determine the high oil production from the generally low porosity and low permeability conglomerate reservoirs. Therefore, the updip slope area with faults connecting the source and reservoirs, abnormal high pressure and subaqueous channel sand conglomerates of the fan delta-front facies are favorable for exploration.更多还原