The Potential for CO2 Disposal in Western Saudi Arabia: The Jizan Group Basalts

Abstract

This thesis evaluates the technical feasibility of carbon mineralization of industrial CO2 emissions into Oligocene volcanic rocks of the Jizan Group under the Red Sea coastal plain in southwest Saudi Arabia. This area contains several industrial sources of CO2 emissions such as power plants and refineries. The Jizan Group are a thick sequence of basaltic lavas and fragmental rocks which are intruded by coeval subvolcanic basalt dikes, layered gabbros, and granite in the southern part of the Red Sea coastal plain. It outcrops along the eastern foothills of the coastal plain, and dips under Miocene and younger sedimentary rocks towards the coast. It formed in a continental rift environment during the initial stages of separation of Arabia from Africa (Schmidt et al, 1982). The volcanics of the Jizan Group are located close to several CO2 sources and to a supply of seawater needed for co-injection with CO2. Successful carbonate precipitation from rocks reacting with CO2 dissolved in water is highly dependent on several technical and environmental factors. The most significant constraint of this process is the need for CO2 sources to be located near water sources and disposal sites (including igneous complexes with the right mineralogical setting, rich in divalent metal cations such as Ca+2, Mg+2 and Fe+2). Basaltic rocks are the most promising type of rock to dispose of CO2 by this process, due to their high abundance of divalent metal cations. This study concludes that the Jizan Group in the subsurface is technically suitable for CO2 disposal by the CarbFix process due to the favorable combination of the following factors: its predominantly basaltic composition, having sufficient thickness of basalts that are saturated with connate waters, the availability of surface and subsurface data, favorable subcrop geometry under the coastal plain, its location near major fixed sources of CO2 emissions, and availability of seawater needed for injection. However, there are risks that need to be better evaluated, particularly the fracture permeability of the Jizan Group basalts and subvolcanic dikes, and their reactivity with CO2 due to hydrothermal alteration of the basalts. This study identifies the general area east of Jizan Economic City as a potential site for the disposal of CO2. Additional sites are possible between Jizan and Jeddah but are subject to greater geological uncertainty from incomplete subsurface data.