Drying Process in Underground Gas Storage Reservoir

During the injection/production cycling in underground gas storage,reservoir rock in area around the wellbore will be dried,which might affect its normal operation.Therefor after analyzing the drying mechanism,a two phase two component model for a single well controlled area was established for simulating the gas cycling process with parameters(reservoir properties and underground temperature and pressure)referenced from Dazhangtuo Gas Storage Reservoir.Simulation results show that the drying area around the wellbore would be enlarged year by year,the radius of the dried area may even exceed 100 meters;water evaporation that leads to reservoir rock drying mainly occurs in the period of dry gas injection,the drying effect during the production time could be negligible;the rate of reservoir drying and the size of affected area depends on the annual cycling gas volume for the injection-production well,as well as the water vapor content difference between the injected gas and the produced gas.The water vapor content in the produced gas during various withdrawn periods changes regularly.At the initial stage,it is near to value of the injected dry gas;then it gradually increases to the saturated water vapor content under the downhole temperature and pressure conditions;and this process tends to be postponed year by year.The research result would provide a foundation for studying the effects of reservoir drying on the normal operation of gas storage.