Restoration of Reservoir Caprock: Long-Term Wellbore Sealing and Abandonment through Zeolite Enhanced Cement.

Oil and gas wellbores that are drilled into the earth’s crust need to be plugged and abandoned, to restore the geological seals once they are no longer producing. The main aim of Plugging and abandonment (P&A) is to ensure that there is no leakage of hydrocarbons into the environment. Since offshore P&A is challenging due to subsurface temperature and pressure conditions, testing zeolite as an additive for improvement of cement properties is an intriguing research topic. This initial research aims to establish the chemical properties of zeolite when added to cement to hypothesize the mechanism of cement property enhancement. This work consists of the initial results in which the microstructural characterization of a naturally obtained zeolite ferrierite (FER) was done to compare it with the existing observations from the literature. Ferrierite was observed to have a needle like orthorhombic crystal structures and spherical crystal aggregates. The chemical composition was confirmed through EDS studies as it is made up of aluminum silicate crystals and proof was shown that the zeolites maintained chemical stability in the cement matrix even after hydration. Morphological characterization also showed features that indicated possible self-healing in commercial zeolite cement formulations used for geothermal wells, which was studied as a reference. The phase stability was indicated by XRD studies with ferrierite peaks observed at 2θ values of 25.195 and 25.5204 and it was differentiated in comparison to plain Class-H cement which did not have those peaks. A preliminary strength testing had also shown an improvement in 5% FER added Class-H cement in comparison to 15% and 30% FER added Class-H cement formulations which is promising for further studies.