冀中坳陷隐蔽型潜山油藏类型与成藏模拟

基于近年来冀中坳陷隐蔽型潜山油藏勘探进展,分析隐蔽型潜山油藏的类型和成藏特点,并通过油气运聚模拟实验剖析隐蔽型潜山油藏的油气运聚机制。潜山油藏可分为容易发现的潜山顶(头)聚油的常规型潜山油藏和不易发现的潜山坡及潜山内幕聚油的隐蔽型潜山油藏。有效隔(盖)层的存在是潜山内幕油藏形成的重要条件,控山断层是其最主要的油气运移通道;潜山坡油藏圈闭的形成需2个遮盖条件,即顶部由不整面之上的泥质盖层遮挡,侧面由潜山内幕隔层形成封堵,不整合面是其主要油气运移通道。二维油气运聚模拟实验表明,输导通道(断层或不整合面)与潜山储集层渗透率的比值及充注动力决定潜山油气的优先充注部位,当断层或不整合面为高效输导层时,油气优先充注潜山顶部,形成潜山顶(头)油藏;当断层或不整合面的渗透性变差或其本身具非均质性,而潜山内幕或潜山坡又存在高渗透性储集层时,则油气优先向潜山内幕或潜山坡充注,形成潜山内幕或潜山坡油藏。

Types of subtle buried-hill oil reservoirs and their accumulation simulation in Jizhong Depression, Bohai Bay Basin

The types of subtle buried-hill resevoirs and their accumulation characteristics are analyzed based on the exploration progression of subtle buried-hill reservoirs in the Jizhong Depression in recent years. These reservoirs are classified into easily discovered buried-hill head reservoirs, and difficultly discovered buried-hill slope reservoirs and buried-hill internal reservoirs. Effective seal is the key factor for the formation of buried-hill internal reservoirs, and mountain controlling faults are the important hydrocarbon migration pathways. As for buried-hill slope reservoirs, two sealing conditions must be satisfied, including the argillaceous caprocks at the top of the unconformities and the buried-hill internal barriers at the flank, and the unconformities act as the primary migration pathways. Simulation experiments on petroleum migration and accumulation by a 2D experimental model show that the preferential charging location of hydrocarbon is determined by the charging force and the permeability ratio of transport pathways (faults or unconformities) to buried-hill reservoirs. When faults or unconformities are high-efficient transport pathways, hydrocarbon will charge the top of the buried hills preferably, thus forming buried-hill head reservoirs. If faults or unconformities are poor in permeability or they are characterized by heterogeneity, hydrocarbon will charge the internal layers or slopes of buried hills, forming buried-hill internal reserovirs or buried-hill slope reservoirs when there are high-permeability reservoirs at the internal layers or slopes of the buried hills.