Research on Casing Load under Complex Fracturing Conditions in Shale Oil and Gas Wells
During the multi-stage fracturing process of shale oil and gas wells,the temperature of the wellbore changes dramatically and the internal pressure alternates frequently,resulting in the horizontal section of the casing being in a complex mechanical environment,and the casing in this area is prone to deformation.A finite element model of casing stress distribution considering temperature effect was estab-lished,and the trend of wellbore temperature variation and its impact on wellbore stress during multi-stage fracturing of oil and gas wells were calculated and analyzed.The stress variation law of the casing during multi-stage fracturing was determined.The trend of wellbore tem-perature changes and the stress borne by the casing during the multi-stage fracturing process of SY1 well were calculated and analyzed.The results show that the temperature inside the wellbore decreases from 147℃to 77℃during a single fracturing process.During the 120 min fracturing process,the temperature rapidly increases from 77℃to 140℃within 500 s,and then slowly increases to 145℃.For the tem-perature effect model,the casing Mises stress shows a cumulative increasing trend with the increase of multi-stage fracturing stages(fractu-ring pressure and thermal effect),which reaches its maximum value after 43.18 h.The Mises stress borne by the inner and outer walls of the casing is 457.7MPa and 417.79MPa,respectively,which is 24.72%higher than the internal wall stress without considering tempera-ture effects.Therefore,when designing the strength of casing under complex fracturing conditions,the effect of temperature needs to be con-sidered.
shale oil and gasfracturingcasingtemperaturepressureload
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