| Wen 23 gas storage is reconstructed on the basis of Wen 23 exhausted sandstone gas field in Zhongyuan Oilfield.66 new drilling wells are deployed.According to the geological characteristics of Wen23 gas field and the analysis of gas storage operation conditions,the following technical problems exist in ensuring the integrity of Wen23 Gas storage casing string.Firstly,the gas source of Wen 23 gas storage contains H2,CO2 and other gases,and the formation water in Wen 23 gas field is highly mineralized.These factors are easy to cause casing corrosion.Therefore,it is necessary to optimize the casing material suitable for the service conditions of Wen 23 gas storage.Secondly,the alternating stress produced by the cyclic strong injection and production in Wen 23 gas storage is easy to cause the casing thread sealing failure.Therefore,it is necessary to optimize the casing sealing thread which meets the working conditions of Wen 23 gas storage.In order to ensure the integrity of casing string and provide guarantee for the safe and stable operation of Wen 23 gas storage,it is necessary to carry out experiments from the above two aspects to study and optimize the anti-corrosion casing material and casing thread with excellent air tightness.In this study,casing materials of different domestic casing manufacturers were extensively investigated,including common carbon steel,low alloy steel,alloy steel,stainless steel and other commonly used casing steels.The casing corrosion resistance test and hydrogen embrittlement resistance test were carried out by simulating the actual corrosion environment of Wen 23 gas storage.Through the casing corrosion test,it is found that the carbon steel and 3cr materials have a large degree of corrosion,while 13Cr and super 13Cr materials have little corrosion;through SSRT test,it is found that the hydrogen embrittlement resistance of carbon steel,3cr and 13Cr materials is weak,and that of super 13Cr is strong.Through the anti-corrosion test and hydrogen embrittlement test of casing,the super 13Cr casing material suitable for Wen 23 gas storage environment is optimized.In this study,BGT2 and TP-G2,the second generation casing gas seal thread commonly used in China,were investigated to simulate the actual operation conditions of gas storage from the aspects of load,bending stress,internal pressure,temperature,etc.,and 40 cycle gas seal cyclic loading tests were carried out to simulate the requirements of gas storage wells serving for more than 30 years.The experimental results show that there is no leakage in BGT2 and TP-G2 casing threads.By comparing with the thread parameters before the experiment,the thread parameters meet the requirements of technical standards after the experiment,and the sealing effect is good.BGT2 and TP-G2 casing threads are optimized by cyclic loading test of gas seal.The research results have been applied in 66 new drilling wells of Wen 23 gas storage.The recommended super 13Cr material is selected for production casing below hanger,and BGT2/TP-G2 air tight sealing thread is used for casing in whole well section.Through production links,it is found that no casing corrosion or string gas channeling occurs in the new drilling wells.It shows that the optimized casing material and sealing thread type are suitable for the actual working conditions of Wen 23 gas storage,and have good corrosion resistance and gas channeling resistance,which meet the drilling requirements of Wen 23 gas storage. |
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