Abstract
With the increasing energy demands of current modern society, underground gas storage (UGS) in gas fields is the most popular type of UGS used to meet the seasonal variation of gas consumption. However, compared with gas fields, UGS in gas fields has the characteristics of periodic high-speed injection and production of exploitation modes and operation rules, which causes the rules of gas-water seepage and utilization of reserves to be more particular and complicated. In this paper, based on Wen 23 gas storage, the rules of multicycle injection and production flow and the utilization of UGS pore volume were investigated. The experimental results showed that variation in porosity and permeability caused by injection and production pressure changes in Wen 23 gas storage can be neglected. The pore volume of gas storage and the degree of gas recovery increased gradually in the pre-UGS gas zone, which was higher than that of reservoirs. In the initial stage of UGS operation, the pore volume of gas storage and the degree of gas recovery were low in the gas-drive-water gas zone as a result of water invasion during the process of reservoir exploitation. During operation of multicycle high-speed injection and production, the seepage conditions in the gas-drive-water gas zone gradually improved. The higher the reservoir permeability, the greater increases in pore volume and degree of gas recovery. In the gas-water transition zone, gas and water were reciprocated and displaced with the multicycle injection-production of UGS, resulting in the gradual deterioration of pore volume and gas recovery, which remained stable at a low value. The negative effects of reservoir heterogeneity on the effective utilization of UGS occurred in the gas-water transition zone. These findings may contribute to a better understanding of the rules of multicycle injection and production flow and utilization of UGS to optimize the injection-production efficiency of Wen 23 gas storage.
Highlights
Natural gas, the cleanest fossil fuel and a potential substitute energy, plays an important and increasingly recognized role in meeting the world’s energy demands [1,2,3]
Wen 23 underground gas storage rebuilt from Wen 23 gas fields is the first super-large gas storage facility in China, with a storage capacity of 10 billion; it is expected to solve the problem of peak shaving of many pipelines in North China
The during mining gas feature the gas-water transition zonethe demonstrated that water intrusion regarding the variation of gas saturation with multicycle injection and production in the gas-water during gas field exploitation, and during the gas storage cycle operation stage
Summary
The cleanest fossil fuel and a potential substitute energy, plays an important and increasingly recognized role in meeting the world’s energy demands [1,2,3]. The injection and production wells alternately inject and produce for long periods of time to meet the peak shaving requirements, with the fluid seepage velocity being much higher than during gas reservoir development It is necessary to conduct a systematic study on the changes in physical properties of UGS due to repeated intrusion of water and the multiphase seepage rules during the high-speed injection-production operation. The effects of the permeability and reservoir heterogeneity properties on the variation of pore volume and gas recovery in UGS were studied These findings may contribute to a comprehensive and systematic understanding of the rules of multicycle injection and production flow and utilization of UGS in gas fields
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