Stress Field Evaluation with Application to Geomechanical Modeling of the Cement Sheath Integrity: A Case Study of the Los Humeros Geothermal Field, Mexico

Abstract

This study presents a solid approach for computing the base data needed for the geomechanical modeling, using non-direct stress measurements such as circulation fluid losses, mechanical caliper log, and continuously measured drilling parameters. The in-situ stresses computed were fed to the analytical model for predicting the cement sheath integrity with the incorporation of wire-line acoustic measurements of the annular cement. The developed method, accounting for mechanical properties of a coupled casing-cement-rock system with the influence of temperature, internal wellbore pressures, and in-situ stresses, can be easily and without additional costs used to evaluate cement sheath integrity during various stages of a geothermal well lifecycle, and help to design drilling, production, and maintenance operations. The investigation carried out in this paper was based on the results from deep drilling operations in the Los Humeros Geothermal Field located at the border of Veracruz and Puebla states in Mexico, where downhole temperatures above the critical point of pure water were recorded, and hostile reservoir fluids were produced. Throughout almost 40 years of drilling operations in the field, issues related to wellbore stability and cement sheath integrity have been observed.