Calculation and Optimization of Instantaneous Safety Factors for Casing in Thermal Recovery Wells of Liaohe Oilfield
Casing failure frequently occurs in thermal recovery wells of heavy oil in the Liaohe Oilfield due to high thermal stress in the casing during steam injection.To solve this problem,it is necessary to optimize the cas-ing depending on engineering geology parameters for thermal recovery of heavy oil.In this paper,considering the changes in yield strength and elastic modulus of casing under high temperature conditions,a numerical model for calculating and analyzing casing stress under the action of temperature-pressure coupling was built using finite ele-ment method,and was verified.The casing-cement sheath-formation temperature field changes during thermal re-covery were analyzed,and the dynamic changes in casing stress under the action of temperature-pressure coupling were calculated.The influences of casing specification parameters(steel grade,wall thickness)and engineering geology parameters(steam injection pressure,formation mechanical properties)on casing stress were identified.The variation of casing safety factor under different conditions was obtained.The research results show that as the steam injection temperature increases,the thermal stress of the casing significantly increases,leading to a decrease in safety factor.In order to meet higher temperature thermal recovery environments,higher grades and thicknesses of casing steel can be used,and different casing steel grades and wall thicknesses can be selected according to dif-ferent engineering scenarios.When the elastic modulus of the formation in thermal recovery wells decreases,the thermal stress on the inner wall of the casing decreases.In order to reduce the thermal stress on the casing,the steam injection pressure can be adjusted to reduce the pressure difference between it and the ground stress.The re-search results provide a basis for the optimal selection of casing for thermal recovery wells in Liaohe Oilfield and the safety evaluation of casing under high temperature conditions.
thermal recovery of heavy oilcasing damagesafety factortemperature fieldwellbore integri-tyLiao Oilfield
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