缝洞型碳酸盐岩油藏数值模拟技术与应用

缝洞型碳酸盐岩油藏储集空间类型多样,溶孔、裂缝、溶洞共存,尺度差异大,流动复杂,既有渗流、裂缝流,又有洞穴流,常用的数值模拟方法已不适用此类复杂介质中的流动问题,为了研究此类油藏的开发机理和剩余油分布规律,建立了缝洞型油藏洞穴流与裂缝流和渗流耦合的数学模型,并用有限体积法对数学模型进行了离散,用自适应方法对方程组进行了求解,形成了缝洞型油藏的数值模拟软件.对塔河油田一个井组剖面和一个缝洞单元进行了数值模拟历史拟合,揭示了此类油藏剩余油类型主要有洞顶剩余油、边角剩余油、阁楼油、底层剩余油、绕流油和充填溶洞剩余油,结果与生产实际相符,证明缝洞型碳酸盐岩油藏数值模拟模型是正确的,对缝洞型碳酸盐岩油藏剩余油挖潜和提高采收率有较大的应用价值.

Numerical simulation technology and its application to fractured-vuggy carbonate reservoirs

Fractured-vuggy carbonate reservoirs have various types of reservoir space with significantly different sizes including vugs, fractures, and caverns. Fluid flow in this type of reservoirs is complicated by the coexistence of flow through the dissolved pores, flow in the fractures and flow in the caverns. The common numerical simulators are no longer suitable for fluid flow in this complex medium. In order to study the development mechanics and the remaining oil distribution in the reservoir, a mathematical model that couples cavern flow and fracture flow with seepage flow is established and discretized with the finite volume method. The equations are solved by using the self-adaptation method. A numerical simulation software for the fractured-vuggy reservoir is developed. The flows within a well group and a fractured-vuggy unit in Tahe oilfield were simulated respectively. The results show that the remaining oil in this kind of reservoirs mainly include the remaining oil at the top of caverns, marginal remaining oil, attic oil, the remaining oil at the bottom of caverns, the remaining oil around high permeable channel and the remaining oil in filled caverns. The results are consistent with the actual production data, verifying effectiveness of the fractured-vuggy carbonate reservoir numerical simulation model. This model is useful for extracting remaining oil and enhanced oil recovery for fractured-vuggy carbonate reservoirs.