Evaluation of Epoxy Resin Thermal Degradation and its Effect on Preventing Sustained Casing Pressure in Oil and Gas Wells

Abstract

Epoxy resin applications in oil and gas wells have significantly increased for remediation and sustained casing pressure mitigation because of its solids-free nature and excellent thermomechanical/bonding properties when used either as a single component or as a resin/cement-enhanced composite. Therefore, it is imperative to assess the formation and degradation of structures in cured epoxy resin at downhole temperatures, particularly because hydrocarbon production requires long-term wellbore integrity. Differential scanning calorimetry was used to determine the glass transition temperature ($$T_{\\mathrm{g}}$$Tg) of the proposed resin system, and thermogravimetric analysis (TGA) was used to characterize the thermal degradation response by monitoring the resin specimens’ mass loss over time under controlled temperature ranging from 300 to $$680\\,{^{\\circ }}\\hbox {F}$$680∘F at atmospheric pressure. The thermal kinetic response based on TGA was then modeled using the Arrhenius equation to predict the resin lifetime under expected wellbore conditions. This work also presents a case study in which an epoxy resin–cement composite is used as an annular barricade to help prevent and reduce sustained casing pressure. The resin–cement composite was placed in the annular section between the 18 5/8- and 13 3/8-in. casing sections as a chemical packer tailored to improve bonding to steel pipe, along with optimizing its mechanical response to cyclic downhole loads, which resulted in no up-to-date sustained casing pressure. For a resin system subjected to downhole temperatures of $$263\\,{^{\\circ }}\\hbox {F}$$263∘F, the model predicts that reaching 10% mass loss by thermal degradation can take more than 160\xa0years, which is beyond the operational life of the wells where the system is evaluated. This indicates that the investigated resin system provides long-term dependability that ultimately results in reduction of intervention/remediation costs, along with production maximization. Additionally, the resin mechanical properties were evaluated at different temperatures to assess their response to expected thermal loading, which resulted in competent barriers that can withstand the cyclic loads generated by continuous wellbore operations. Furthermore, cement bond log results further support the optimum annular integrity attained when utilizing a cement–resin composite as chemical packer for enhanced isolation and annular pressure buildup mitigation.