# Feasibility Assessment of Acid Gas Injection in an Iranian Offshore Aquifer
###### Abstract  
Acid gas injection operations function as the commercial equivalent of certain aspects within the realm of geological CO\({}_{2}\) storage. Acid gas, composed of H\({}_{2}\)S and CO\({}_{2}\), alongside minor quantities of hydrocarbon gases stemming from either petroleum production or processing, constitute the composition of acid gas. The primary aim of acid gas injection operations lies in the disposal of H\({}_{2}\)S. Nevertheless, substantial volumes of CO\({}_{2}\) are concurrently injected due to the economic impracticality of segregating the two gases. This investigation delves into the comprehensive, step-by-step procedure that can be employed to determine the suitability of a field or formation for acid gas injection, utilizing all accessible data, including the literature and data from neighboring fields. This approach incorporates sensitivity analysis of various parameters to ascertain the feasibility of AGI while minimizing costs and time consumption. The focus of this study centers on evaluating the feasibility of Acid Gas Injection (AGI) in a saline aquifer offshore in Iran. The assessment encompasses the examination of reservoir properties, geomechanical aspects, caprock integrity, and gas plume dynamics. The Surmeh formation emerges as a promising candidate for AGI due to the presence of upper dolomite and lower carbonate within the rock formations. Geomechanical analysis reveals a pore pressure of 3800 psi and a fracture pressure of 6100 psi. Caprock integrity, particularly within the Hith formation, emerges as pivotal for both containment and long-term stability. Seismic mapping highlights variations in caprock thickness, influencing containment effectiveness. Capillary trapping emerges as a significant factor in short-term gas entrapment and plume distribution. Numerical simulations elucidate the impact of heterogeneous rock properties on capillary trapping and gas plume movement. The projection estimates approximately 2 TCF (Trillion Cubic Fee) of acid gas injection into the Surmeh formation. Based on the acid gas content and the gas in place at the source of injection, the recommended injection rate stands at 180 MMSCFD (million standard cubic feet per day). The formation's inherent tightness limits injectivity, allowing for a maximum achievable rate of 7 MMSCFD with a permeability of 1 mD (milliadry). However, a higher porosity (12%) and a permeability of 100 mD enable more efficient injection without fracturing the formation. To achieve this, it becomes imperative to implement two injection wells, each with a capacity of 90 MMSCFD. acid gas injection (AGI); saline aquifers; capillary pressure; reservoir characterization; caprock integrity; capillary pressure +
Footnote †: journal: Applied Physics Letters  
Article Feasibility Assessment of Acid Gas Injection in an Iranian Offshore Aquifer  
[PERSON]  
1 Department of Environmental, Land and Infrastructure Engineering (DIATI), Politecnico di Torino, 10129 Turin, Italy; [EMAIL_ADDRESS] (M.C. ); [EMAIL_ADDRESS] (S.J.) as much as possible and offset any residual emissions through effective carbon removal strategies [1]. Carbon capture and storage (CCS) represents a crucial technology with the aim of tackling greenhouse gas emissions and reducing the effects of climate change [2]. CCS technologies offer the means to achieve both carbon dioxide removal and emissions reduction. These technologies start by isolating carbon dioxide through a capture process. Subsequently, the captured carbon dioxide is conditioned, transported, and finally stored in geological formations. As a result, CCS technologies effectively reduce carbon dioxide emissions at specific sources or extract carbon dioxide directly from the atmosphere [3]. Acid gas injection operations serve as the commercial equivalent to some aspects of geological CO\({}_{2}\) storage. Acid gas, comprising H\({}_{2}\)S and CO\({}_{2}\), together with small amounts of hydrocarbon gases originating from petroleum production or processing, make up the acid gas composition [4].