叠复连续油气藏成因机制、发育模式及分布预测

Formation mechanisms,distribution models,and prediction of superimposed,continuous hydrocarbon reservoirs

不受浮力控制且大面积分布的油气藏自20世纪80年代被发现后受到世界各国政府和学者的高度重视,国际SPE、SPEE、WPC等权威机构将其命名为连续油气藏(continuous-type deposit),这类油气藏在美国的产量已占天然气总产量的三分之一并还在稳定增长,展现出广阔的勘探前景。广泛连续油气藏是一种非常规油气藏,它们是如何形成的?为什么内部高压油气层与低压油气层共存、早成油气藏与晚成油气藏共存、富油气区与含水区共存?这些问题长期以来困扰着国内外专家学者。研究表明:叠复连续油气藏发育于含油气盆地浮力成藏下限和油气成藏底限之间的局限流体动力场内,资源潜力大;叠复连续油气藏是局限流体动力场形成演化过程中不同阶段、不同动力机制形成的致密常规油气藏、致密深盆油气藏、致密复合油气藏等在时空上叠加复合而成,纵向上紧邻有效烃源岩层系分布;叠复连续油气藏内油气富集程度差异大,平面上受同一目的层段"近源-优相-低势"复合区控制。基于对3种致密油气藏成因机制与主控因素的揭示,建立了局限流体动力场内多要素组合控制叠复连续油气藏的形成和分布模式并研发了预测方法和评价技术。

Since their discovery in the 1980 s, hydrocarbon reservoirs that are widely distributed and uncontrolled by buoyancy have received great attention from governments and scholars in the world. These hydrocarbon reservoirs are named continuous-type deposit by international authorities, e. g. , Society of Petroleum Engineers, Society of Petroleum Evaluation Engineers, and World Petroleum Council. Their production has accounted for one third of the total output of natural gas in the United States and is still experiencing a steady growth, showing great prospects of hydrocarbon exploration. Wide continuous-type deposit is a type of unconventional reservoirs and there have been long-term issues about its formation mechanisms as well as the coexistence of high- and low-pressure reservoirs, early- and late-formed reservoirs, or hydrocarbon-rich and water-bearing zones. In this study, the results show that superimposed, continuous hydrocarbon reservoirs with great resource potentiai are developed in the limited fluid dynamic field between the lower boundary of buoyancy-controlled accumulation and bottom boundary of hydrocarbon accumulation in hydrocarbon-bearing basins. These reservoirs are superposed in time and space by three types of tight reservoirs, i. e. , tight conventional reservoirs, tight deep basin reservoirs and tight composite reservoirs which are developed in the limited fluid dynamic field of hydrocarbon-bearing basins at different stages with various driving forces. Vertically, the superposed reservoirs are distributed closely to bed series of effective source rocks. The degree of hydrocarbon enrichment in substantially varies in superposed, continuous reservoirs and is horizontally controlled by the near source-favorable facies-low potential composite zone of the same target interval. Based on the analysis of the formation mechanisms and major controlling factors of different tight hydrocarbon reservoirs, geological models of multi-key-factor combination controlling the formation and distribution of superimposed continuous hydrocarbon reservoirs in the limited fluid dynamic field were established.