基于开发资料预测气藏改建储气库后井底流入动态

Downhole inflow-performance forecast for underground gas storage based on gas reservoir development data

针对应用当前方法预测储气库井底流入动态误差大的问题,开展储气库渗流模拟实验,建立了考虑气藏改建储气库后渗透率变化的井底流入动态方程,并通过实例进行了验证。模拟实验结果表明,水侵储集层改建储气库后,气相渗透率与气藏开发阶段不同,受储气库运行中气水渗流关系的影响,过渡带渗透率逐步恶化,纯气区渗透率逐步改善、甚至超过气藏开发初期储集层水侵前的水平。依据实验结果,引入描述气藏改建储气库后渗透率变化的参数,改进了传统井底流入动态方程,利用气藏开发资料预测改建储气库后井底流入动态。实例分析结果表明,改进后的井底流入动态方程考虑了渗透率的影响,预测结果与实测结果基本一致,而传统方法预测结果与实测结果有较大差别。

In view of the gap between the inflow-performance forecasted by the traditional equation and the actual inflow-performance, experiments of gas-gas alternating seepage flow and gas-water alternating seepage flow were carried out, and a modified equation of inflow-performance relationship considering gas permeability change due to water invasion was established. This equation was verified by example analysis. The experimental results show that： gas permeability of net pay, when water-invaded reservoirs are converted into underground gas storage, is different from that during actual gas field development, in that the value of permeability decreases gradually in gas-water zone while the value increases gradually and even higher than that of original gas field in gas zone as a result of gas water alternative flooding in gas storage. Then one parameter describing the extent of permeability change when gas reservoirs are converted into gas storage was defined based on the result of the experiments, and eventually the traditional equation of inflow-performance relationship was modified to forecast inflow-performance in gas storage based on data from field development. Example analysis result shows that： the modified equation considers the effect of changing permeability, its results agree with the actual infiow-performance, while the result of traditional equation differs greatly from the actual inflow-performance.