Mechanical performance experiments on rock and cement, casing residual stress evaluation in the thermal recovery well based on thermal-structure coupling

Abstract

Thermal stress deformation can cause serious casing damage and failure problems in thermal recovery wells. In this paper, mechanical performance experiments on rock and cement are carried out first, and then a finite element mechanical model of thermal recovery wellbore based on thermal-structure coupling is established. The thermal stress variation of wellbore based on thermal-structure coupling and its influence on casing residual stress are studied. The change rule of wellbore stress with a steam stimulation process is also analyzed using the model. The analysis results indicated that the rate of thermal expansion of each material was different in the wellbore. The casing and cement sheath were compressed, producing a large strain on the inner wall of the cement sheath. The local deformation of the wellbore rock acted on the casing under thermal stress, which caused casing deformation and failure. The relationship between the residual stress of the casing and the steam injection cycle was obtained through numerical simulation and was used to quantitatively evaluate and analyze the residual strength of the casing. The results of this study provide an important reference for wellbore mechanical evaluation and a theoretical basis for reasonable preventative measures for casing failure in thermal recovery wells.