Experimental Study on Sealing Failure of Cement Sheath in Gas Storage Wells
Cyclic injection and production of gas would cause cyclic loads on the cement sheath of gas storage wells,which can easily lead to the sealing failure of cement sheath.In the paper,against the background of seal-ing failure of cement sheath in H gas storage well,the tests on cyclic loading and unloading,mechanics,porosity and permeability of hardened cement were conducted,the microstructure CT morphology of hardened cement after cyclic loading was obtained,and full-scale cement sheath sealing failure tests were conducted.The experimental results show that after 30 turns of cyclic loading,the mechanical properties of hardened cement decrease and the gas penetrating power increases,but the gas can still be effectively prevented from leaking from the cement matrix;cyclic loading and unloading would cause damage to the microstructure of hardened cement,resulting in cumulative plastic strain,and the more cycles there are,the greater the cumulative plastic strain is;after cyclic loading and unloading,the CT scan morphology of hardened cement shows that there is microstructural damage in the hardened cement,and the degree of microstructural damage gradually weakens from both ends to the center;the full-scale test confirms that the abhesion of hardened cement-inner casing interface forms micro annulus,the bottom gas flows up along the micro annulus,causing pressure in the upper B annulus,but the cement sheath body and the second interface do not show any damage under each group of test pressure,so it is not recommended to continue to in-crease the gas storage pressure on the existing basis.The study results guide the optimization design of injection and production parameters of H gas storage,and provide reference for the reasonable formulation of operation system of similar gas storages at home and abroad.
gas storage wellcement sheathcyclic loadingsealing failurefull scale test
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