缝洞型气藏地下储气库产能测试不稳定资料评价新方法

A new method for evaluating transient productivity test of underground gas storage in fractured vuggy gas reservoirs

缝洞型气藏储气库气井产能测试过程中,相当部分气井在大产量测试下未稳定、流压呈现线性下降、关井压力恢复速度慢、终点压力明显低于初始压力,这类异常现象偏离了常规产能评价方法的理论假设。通过分析此类产能测试异常机理,提出一种近井单元与外围单元的串联结构模型,建立了串联结构的缝洞型气藏流动数学模型。通过计算模拟发现:常规方法对短时间测试的预测产量偏高并随地层压力下降而加剧;长时间测试下随单元间压差的扩大,单元之间的窜流流量接近测试产量。为表征串联缝洞系统的连通能力提出了一种3参数产能方程,并建立缝洞型气藏产能测试不稳定资料的解释方法,分别评价近井区的产能与库容、远井区的窜流能力。某缝洞型储气库X6井注采井实测资料分析应用表明,新的评价方法具有较好适应性,对合理预测储气库井的调峰能力具有指导意义。

In the process of productivity test for gas wells in gas storage reservoirs of fractured vuggy gas reservoirs,many gas wells are unstable under some problems like large production test,flow pressure shows a linear decline,shut in pressure recovers slowly,and end point pressure is significantly lower than the initial pressure.This phenomenon deviates from the theoretical assumptions of conventional productivity evaluation methods.This paper analyzes the abnormal mechanism of this kind of productivity test,builds a structure model of near well unit and peripheral unit,and establishes a flow mathematical model of fractured vuggy gas reservoir with series structure.Through calculation simulation,it is found that the predicted production of conventional methods for short-term test is higher;With the expansion of the pressure difference between units,the cross flow between units is close to the test output under the long-term test.In order to characterize the connectivity of the series fracture cavity system,a three parameters productivity equation is proposed,and an interpretation method for unstable data of productivity testing of fracture cavity gas reservoirs is established to evaluate the productivity and reservoir capacity of the near well area and the channeling capacity of the far well area respectively.The analysis and application of the measured data the Well X6 of a fracture-cavity gas storage injection-production well show that the new evaluation method has good adaptability.