Cement sheath integrity at simulated reservoir conditions of pressure, temperature, and wellbore configuration in a laboratory setup

Abstract

Cement is fundamental to maintaining integrity throughout the life of a well by preventing leakage of fluids. Cement is thus crucial in oil and natural gas producing wells as well as in wells used for storage and utilization of carbon dioxide and hydrogen. Even if the cement slurry has been properly placed, changes in downhole reservoir conditions can induce thermal and mechanical stresses to harm the integrity of the cement sheath.This work presents a novel apparatus to analyze the cement sheath performance at simulated reservoir conditions of pressure, temperature, and wellbore configuration. One of the major features demonstrated is three-dimensional (3D) monitoring of in-situ dynamic changes in cement using acoustic data. 3D density profiles allow visual observance of the evolution of possible settling over the cement curing process. A first arrival pick time decrease of 26.6% is observed over a 15-h curing time. Confinement improves the strength of cement as seen by decrease in travel time (10.8%) and increase of amplitude (32%) with 15 MPa confining pressure increase. Temperature increase of 66.4 °C has damaging effects on the strength of cement as seen by increase (11.9%) in travel time and decrease (20.5%) in amplitude. An increase in cement shear bond strength from 13% to 89.7% with longer curing time is measured using this device.