超深断控缝洞型碳酸盐岩油藏注水重力驱油理论探索

Theoretical exploration of water injection gravity flooding oil in ultra-deep fault-controlled fractured-cavity carbonate reservoirs

在超深层断控碳酸盐岩缝洞组合地质特征与储集单元划分分析基础上,制作了2种物理模型,开展了注水驱油物理模拟试验;探索了断控缝洞型碳酸盐岩油藏复杂流动条件下的注水驱油机理,建立了断控碳酸盐岩油藏渗流和自由流共存状态下的数学模型,并据此开展了矿场注水先导试验,评价注水提高采收率实施效果。研究表明:断控缝洞型碳酸盐岩油藏单元可划分为强天然能量连通型、弱天然能量连通型和弱天然能量孤立型3种主要类型;断控缝洞体断裂(裂缝)活动性指数可有效表征储集层连通性,预测注水连通受效方向;断控碳酸盐岩油藏渗流和自由流共存状态下的数学模型,可定量描述缝洞体中流体的流动规律;断控缝洞体注入水受岩性体毛细管力作用弱,油水运动主要受重力主导;依据缝洞空间连通结构和井储空间配置关系提出的单井注水吞吐替油、单元注水驱油、单井高压注水开发方式经矿场先导试验证实,注水重力驱油效果明显。

Based on the analysis of geological characteristics of ultra-deep fault-controlled fracture-cavity carbonate reservoirs and division of reservoir units,two physical models were made,and physical simulations of oil displacement by water injection were carried out to find out water flooding mechanism in the fault-controlled fracture-cavity carbonate reservoir under complex flow state.On this basis,a mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flow has been established.Pilot water injection tests have been carried out to evaluate the effects of enhancing oil recovery by water injection.The results show that:fault-controlled fracture-cavity carbonate reservoir units can be divided into three types:the type connected and strong in natural energy,the type connected and weak in natural energy,and the type isolated and weak in natural energy;the fault-fracture activity index of the fault-controlled fractured-cavity body can effectively characterize the connectivity of the reservoir and predict the effective direction of water injection;the mathematical model of fault-controlled carbonate reservoir with coexisting seepage and free flows can quantitatively describe the fluid flow law in the fracture-cavity body;the water injected into the fault-controlled fracture-cavity body is weakly affected by the capillary force of the lithologic body,and the oil-water movement is mainly dominated by gravity.The development modes of single well water injection,unit water injection,and single well high pressure water injection proposed based on the connection structure of fracture-cavity space and well storage space configuration are confirmed effective by pilot tests,with obvious water injection gravity flooding effect.