Enhanced Mechanical-Integrity Characterization of Oilwell Annular Sealants Under In-Situ Downhole Conditions

Abstract

Summary In this study, we describe an innovative and novel methodology comprising a high–pressure/high–temperature (HP/HT) in–situ–triaxial–testing apparatus for the measurement of sealant mechanical properties (i.e., compressive strength, Young's modulus, and tensile strength) under simulated downhole conditions. The equipment can be used to perform both curing and testing using the same apparatus, thus eliminating depressurization and cooling of test specimens. Additionally, at minimum, three samples can be tested sequentially for statistical analysis and uncertainty mitigation, along with performing real–time monitoring of total HP/HT shrinkage/expansion. The testing apparatus is rated to 30,000 psi for axial loading, 20,000 psi for confining loading, and 400°F. Preliminary validation of Young's modulus was performed with five different plastic samples, yielding error percentages of less than 5% compared to measurements performed using a standardized loading frame. Compressive– and tensile–strength validations were performed using a 16–lbm/gal cement design, and error percentages of less than 2.5 and 7%, respectively, were obtained compared to standardized testing procedures or other studies of the subject. Moreover, a 16–lbm/gal cement system was also used to help assess the functionality of the testing apparatus under simulated wellbore conditions with temperature and pressure ranging from 80 to 350°F and 3,000 to 8,000 psi, respectively.