基于Fluent与Hernandez模型的缝洞型油藏水驱油机理及影响因素分析

Analysis of mechanism and influential factors of water-driven-oil in fractured-vuggy reservoirs based on Fluent and Hernandez

针对碳酸盐岩缝洞型油藏剩余油分布问题,利用Fluent软件进行油水分布特征研究。在不同参数取值下,对Hernandez模型进行计算。将复杂的缝洞结构简化为4种几何模型。分析缝洞结构、驱替水的注入速度和油的运动粘度和油水粘度比4种因素对剩余油分布的影响,归纳缝洞内流体流动规律。数据分析结果表明:驱替水进入缝洞占据原油空间位置是水驱油的主要采收机理;水注入的速度会影响缝洞的初期出油率,但不会影响缝洞内极限原油剩余率;油水粘度比越高,原油采出率越高,缝洞内剩余油量越少;在水驱前缘位置所受到的粘性力越大,越有利于油水互相扩散;扩散系数对于不同的缝洞类型有不同数量级的取值。

Aiming at the problem of distribution of remaining oil in fractured-vuggy carbonate reservoirs ,the distribution characteristics of oil and water are studied using the software Fluent. Hernandez model is calculated for different parameters. The complex fracture-cavity structure is simplified into four geometric models. The influences of the fracture-cavity structure,displacement water injection velocity,oil kinematic viscosity and oil-water viscosity ratio on the fluid flow in a fracture-cavity are analyzed. The rule of fluid flow in the fracture-cavity is induced. Analysis results show that the main recovery mechanism of water flooding is that the displacement water enters the fractures and holes to occupy the space position of crude oil;the rate of water injection affects the oil yield initially in the fracture hole,but does not affect the ultimate oil residual rate in the fracture hole;the higher the oil-water viscosity ratio is,the higher the crude oil recovery rate is,and the less the residual oil in the fracture hole is;the viscous force at the leading edge of the water drive is in favor of the oil-water diffusion. The order of magnitudes for the diffusion coefficient is different for different types of joints and holes.