Modeling thermal-induced wellhead growth through the lifecycle of a well

Abstract

During production from high-yield wells, hot reservoir fluids may significantly heat the casing string which may lead to the wellhead growing out of the surface once the induced thermal stress exceeds the wellhead load. This issue involves some challenges that lie in the initial gravity-driven elongation of casing strings before cementing and then their combined expansion with annular cement as one assembly due to later temperature changes. Here, we proposed an integrated modeling method for wellhead growth by incorporating heat transfer and thermodynamics. Element-death technique is used to simulate free elongation of the casings in the absence of cement before cementing and their subsequent coupling thermomechanical behavior with cement after cementing job. Arbitrary Lagrange-Eulerian (ALE) adaptive meshing is employed to avoid mesh distortion due to uncoordinated deformation between casings and cements. Numerical results indicate that the combined effect of gravitational-induced tensile strain and thermal-induced compressive strain may potentially result in a strain-neutral point within the casing. Beyond this point, the casing experiences a tensile state, whereas, below it, the casing is subjected to a compressive state. Furthermore, casing running friction can mitigate tensile strain, while higher production can enhance the thermal strain in the casing. Both factors contribute to shifting the strain neutral point upwards and exacerbating the risk of wellhead growth. However, the application of pre-tensioned casing while cementing can effectively mitigate wellhead growth by offsetting the thermal-induced compressive strain through the increasing tensile strain.