基于高速非达西渗流的断溶体油藏连通性预测模型

针对断溶体油藏地质特征复杂、准确快速模拟难以实现的问题,以储层静态物性参数和动态注采数据为基础,将复杂的断溶体结构离散为井—缝—洞间的一维连通单元。提出了能够表征井间连通特性及物质基础的两个特征参数：传导率和控制体积。同时,引入流体高速非达西渗流项来描述断溶体内真实渗流特征,建立了断溶体油藏井—缝—洞间的连通单元物质平衡方程,实现了断溶体油藏油水动态模拟。研究结果表明：定液制度下,非达西渗流系数β=0,传导率值不变;β>0,随β值增大,连通单元内传导率下降程度增大,水相受非达西作用影响更明显,导致油井见水时间滞后,地层压力及井底流压下降,所需生产压差增加。针对Z断裂带,在达西渗流条件下,各计算指标与实际值难以拟合;当β取值在10³~10⁴时,单井流压及区块产油拟合效果理想,更符合实际流动。高速非达西作用明显的单元内连通性更好,对井间连通性准确预测具有指导意义。

A connectivity prediction model for fault-karst reservoirs based on high-speed non-Darcy flow

To address the problems caused by the complex geological characteristics of fault-karst reservoir and difficult to be solved by accurate and fast simulation, the complex fault-karst structure was discretized into a one-dimensional connected unitamong well, fracture and vugbased on the static physical parameters of reservoirs and the dynamic injection and extraction data. Two characteristic parameters, i.e., conductivity and control volume, were proposed to characterize the inter-well connectivity properties and material basis. Meanwhile, this paper introduces the high-speed non-Darcy flow term to describe the characteristics of real flow in the fracture body, sets up the material balance equation of the well-fracture-vug interconnection unit in fault-karst reservoirs, and realizes the simulation of oil-water dynamics in fault-karst reservoirs. The results research show that under the constant fluid regime, when the non-Darcy flow coefficient β=0, the conductivity value remains unchanged; when β>0, with the increasing of β value, the conductivity decline in the connected unit increases, and the water phase is more obviously affected by the non-Darcy effect, which leads to the lag time of water occurrence in the well, the decrease of formation pressure and bottom flow pressure, and the increase of the required production pressure difference. For the Z fracture zone, it is difficult toperform the fitting between the calculation indexes and the actual values under the Darcy flow conditions; when β is set to be 10³-10⁴, the single well flow pressure is well fitted with the block oil production, and are more in line with the actual flow. The connectivity is even better in the unit with obvious high-speed non-Darcy effect, providing a guidance for accurate prediction of inter-well connectivity.