Experimental Study On Increasing Space Utilization Rate Of Sediment In Butt Well Salt Cavern Gas Storage

At current stage,the technology of butt well salt cavern gas storage has become a hot research issue in the area of salt cavern gas storage.However,most of China’s reservoirs are layered salt layers,which are characterized by many interlayers,single interlayer thickness,and high insoluble content.During the process of cavity creation,insolubles in the salt layer and the interlayer are released,settled and accumulated to the bottom of the cavity,forming sediment.The brine in the sediment gap occupy a large amount of gas storage space,and the existing process cannot discharge the brine in the sediment,resulting in a decrease in the effective storage capacity of the gas storage.Therefore,it is important to increase the the availability of sediment.In response to the above problems,the method of combining theoretical analysis and laboratory experiments is mainly used.The main research contents and results are as follows:(1)Combining salt rock geological characteristics and salt rock dissolution experiments,the formation causes and distribution characteristics of the sediments in the salt cavern gas storage were developed.It was found that the insoluble matter in the soluble salt layer and the collapsed interlayer accumulate at the bottom of the cavity to form a sediment;Under the experimental conditions in this paper,the particle size of insoluble is mainly distributed in six ranges of less than 2.5mm,2.5mm～5mm,5mm～10mm,10mm～20mm,20mm～30mm,and more than 30 mm.Among them,the particle size of insolubles is mostly distributed between 10～20mm,and the mass percentage is45.80%.(2)The insoluble materials obtained in the salt rock dissolution experiment were used to prepare sediment samples,and the sediment space utilization experiment was carried out.Through the sediment void ratio test and the gas displacing water experiment of the sediments,it was found that the insoluble sediment voidage volume was 51.8% on average;The average utilization rate of sediment space is 8.2%,that is,8.2% of sediment space can be vacated by gas injection and brine discharge to increase the volume of gas storage,and then use the gap as a gas storage space.(3)The geological conditions for the construction of gas storage are optimized,and in view of the shortcomings of the space utilization technology of the butt well salt cavern gas storage at this stage,a new technology for the space utilization of it is proposed.That is,a cavity is newly cavern next to the butting well cavern as a brine drainage channel,which can effectively discharge the brine in the sediment.The research results are expected to increase the availability of the sediment in butt well salt cavern gas storage,and provide reference and basis for the expansion of the gas storage.