Effects of Hydrogen on Class H Well Cement's Properties Under Geological Storage Conditions
Diego Fernández, Hossein Emadi, S. Thiyagarajan, Athar Hussain, Ion Ispas
Abstract
ABSTRACT Depleted oil and gas reservoirs are one of the most promising alternatives for underground hydrogen storage due to their sealant capacity and presence of residual hydrocarbon, which reduces the requirements for cushion gas and operational costs. Its existent infrastructure is also attractive owing to its lower investment costs. However, wells and facilities have been designed and constructed for operating with hydrocarbons and might be affected by the presence of hydrogen. Failure in well integrity could lead to hydrogen leakage, compromising the storage security for hydrogen projects. Hence, understanding hydrogen's effects on wellbore components such as casing and cement sheath becomes important. Although the effects of hydrogen on steel have been widely studied, effects of hydrogen on cement sheath and its properties are currently unknown. This study aims to evaluate the change in properties of neat Class H cement after being exposed to hydrogen under geological storage conditions (1500 psi and 120°F) for different time periods. Properties such as permeability, porosity and dynamic elastic properties like Young's Modulus and Poisson's ratio, were measured and analyzed before and after hydrogen exposure to investigate its effects on cement sheath. The experimental results revealed an increase in the permeability and porosity of the cement samples after hydrogen exposure. Also, hydrogen affects the dynamic elastic properties of the samples. The results of this study could be used to assess the wellbore integrity risks in depleted oil and gas reservoirs. INTRODUCTION Hydrogen is expected to play a fundamental role in the future global energy system. Its outstanding energy capacity (120 MJ/kg) (Abe et al., 2019) combined with its clean combustion, makes it one of the most promising alternatives as an energy carrier (Hosseini & Wahid, 2016). Although, hydrogenis the most abundant element on earth, it is not found freely in a sufficient amount, but it can be produced from non-renewable sources in multiple ways such as hydrocarbon reforming, hydrocarbon pyrolysis and subsurface production (in-situ combustion), or from renewable sources through water electrolysis. Once produced, hydrogen is burned and energy is conveyed as heat (Najjar, 2013; Salahshoor & Afzal, 2022; Veras et al., 2017).