A prediction method of wellhead movement with consideration of interface debonding

Abstract

The cementing cement all returns to the wellhead in offshore heavy oil thermal recovery wells, and the wellhead movement (WHM) still occurs frequently, indicating serious interface debonding between the casing and cement sheath during steam stimulation. Hence, a method for evaluating the bonding performance at the casing-cement sheath interface (CS interface) is proposed, by which the axial bonding strength, radial bonding strength, and friction coefficient at the CS interface are obtained. An elastic-plastic mechanical model of the casing-cement sheath-formation (CSF) system under temperature-pressure coupling is established to clarify the axial and radial bonding failure mechanisms at the CS interface. Based on the experimental results and mechanical model of the CSF system, the calculation method for the free casing and WHM model are established with consideration of cement return height (non-cementing section), cementing quality (poorly cemented section), axial bonding failure and radial bonding failure at the CS interface, by which the accuracy and reliability of this model have been verified by on-site data. The research results could provide a theoretical basis for real-time, intelligent, and scientific prediction of WHM.