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Enhancing the Geo-mechanical Stability of Class G Cement in Subsurface Hydrogen Storage System. A Case Study in Ghana Gas National Company
Rexford DONKOR, Franklin Duodu AHWIRENG; Ernest ACKAH, Robert QUANSAH-OPIRIM; John Ebenezer OSEI SAFAH, Rockson ALUAH
[Ghana National Gas Company, Ghana]
The rise in greenhouse gas emissions is compelling nations worldwide to implement measures to mitigate climate change. The utilization of large geological formations, such as depleted oil and gas reservoirs, salt caverns and saline aquifers, for hydrogen storage offers an opportunity for long-term sustainable energy solutions, thereby aiding the advancement of a low-carbon economy. In the process of geological storage, hydrogen is injected and withdrawn via wells that are cemented and cased. Effective cementing is crucial in this context to ensure the integrity of wells and the sealing ability of underground hydrogen storage (UHS), thus preventing gas leakage and ensuring long-term. This research investigates the effect of fly ash and eggshell power (FAESP) additives on the mechanical and sealing properties of Dyckerhoff class G cement intended for underground hydrogen storage (UHS). Particle size distribution, SEM, and XRF analyses were used to characterize the cement powder, fly ash, and eggshell power. Various proportions of powder, fly ash, and eggshell powder were added to cement slurries, ranging from 0% to 4% by weight of cement (BWOC). The molds samples were cast and cured at High Temperature, High Pressure (HTHP) Autoclave Rector (Parr Rector) of 294F and 3000psi. Concurrently, hydrogen gas was injected into the reactor vessel environment to simulate the conditions anticipated in subsurface hydrogen storage applications. A comprehensive set of tests were conducted under the hydrogen storage reservoir condition to evaluate the effects of varying concentrations of fly ash and eggshell powder (FAESP) ranging from 0.25% to 4.0% by weight of cement (BWOC) on class G cement and ed against plain class G cement (Base cement). The results indicate that the 2% by weight of cement (BWOC) of the optimum blend of fly ash (FA) and eggshell powder (ESP) concentration sufficiently improve performance of the class G cement under the hydrogen storage reservoir condition. This concentration significantly improved yield stress and gel strength while reducing porosity and permeability, addressing gas migration concerns and bolsters its resilience against the corrosive effects of hydrogen. It also enhanced compressive strength and imparted resilience, as evidenced by a reduction in Young’s Modulus. This study validates the potential for sustainable and cost-effective advancement of class G cement properties by harnessing the synergistic effects of combining fly ash and eggshell powder under the hydrogen storage reservoir condition.
Topic: General