Evaluation of CO₂ attack in wellbore class G cement: influence of epoxy resins, composites and minerals as additives

Abstract

Carbon dioxide (CO 2 ) injection into geological formations is pointed out as one of the most effective alternatives to reduce anthropogenic CO 2 emissions to the atmosphere. To promote long-term CO 2 storage, wellbore integrity is a critical issue to be considered. Portland cement is commonly used for cementing wells, and considered chemically unstable in CO 2 -rich media. In this context, this study investigated the CO 2 chemical resistance of class G Portland cement modified with novel additives (epoxy resins, epoxy-clay composites, and clay minerals) at 1 and 2.5 wt% contents. Reaction times of 7 and 30 days of exposure to CO 2 in supercritical conditions were evaluated. Samples were characterized by mechanical compression tests and phenolphthalein indicator as well as field emission scanning electron microscopy in order to determine the depth of carbonation in cement. Our results indicate that although there is slight reduction in the initial compressive strength, the addition of tested additives to cement paste offers improvements in terms of chemical resistance. The optimum content of different additives was 1 wt% in order to maintain compressive strength properties and improve chemical resistance to CO 2 . The best result was achieved with an epoxy resin blend as an additive, decreasing carbonation by up to 60% (7 days of exposure to CO 2 ) and 52% (30 days of exposure to CO 2 ).

Basalt powder as a supplementary cementitious material in cement paste for CCS wells: chemical and mechanical resistance of cement formulations for CO2 geological storage sites

“…Thus, Oil & Gas companies are constantly searching for an adequate solution to increase well integrity in CO 2 -rich environments (Tiong et al, 2019). The use of supplementary cementitious materials (SCM) (Abid et al, 2020;Ledesma et al, 2020;Schütz et al, 2019;Sedić et al, 2020), nanomaterials (Abid et al, 2020;Mahmoud and Elkatatny, 2019;Tiong et al, 2019), polymers (Baldissera et al, 2017b(Baldissera et al, , 2017aSchütz et al, 2019) and composites (SCM reinforced polymers) (Schütz et al, 2019(Schütz et al, , 2018 has been highlighted as possible alternative to improve cement chemical resistance. However, it is required further studies to evaluate the performance of these materials in representative conditions of CCS storage sites.…”