A new method for evaluating transient productivity test of underground gas storage in fractured vuggy gas reservoirs
Keywords:
fracture-cavity gas reservoir, gas storageAbstract
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. © 2023 Well Testing. All rights reserved.
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