New paper out : "Potential for CO2 plume geothermal and CO2 storage in an onshore Red Sea Rift basin, Al-Wajj, Saudi Arabia: 3D reservoir modeling and simulations".

01 March, 2024


Using supercritical COinstead of water for geothermal energy extraction offers advantages while enabling

COsequestration. The integration of COcapture, utilization, and storage (CCUS) in geothermal reservoirs

aligns with circular carbon economy models and supports the goals of sustainable energy development. The

geothermal potential of deep saline aquifers, like in the young and high-heat-flux Red Sea rift basins of western

Saudi Arabia, holds promise for geothermal heat extraction and COstorage. However, quantitatively assessing

the geothermal and carbon storage potential requires a comprehensive characterization of physical parameters

specific to the target aquifer units.

This study presents a detailed 3D reservoir modeling of a sedimentary basin example (Al-Wajj basin) in

Western Saudi Arabia developed using advanced geostatistical techniques and a state-of-the-art COfluid

flow simulator. We constrain physical parameters and provide estimates of the target aquifers’ recoverable

geothermal energy and COstorage capacity. We develop a 3D trend model that arranges the spatial changes in

the high permeable sandstone volume distribution and we obtain the weighted average of sandstone percentage

in the model area. We build the geostatistical model using multiple-point statistics simulations with a training

image that represents spatial dependence of facies changes of submarine channels in a syn-rift clastic system

along the target basin with respect to slope distance. For a 10% heat recovery threshold, our simulation results

indicate above 41% permeable sandstone volume is necessary.

Our reservoir simulation results further indicate the potential to produce 790 TWh of geothermal energy

in a 40-year injection–production scenario and to store 76.5 Giga-tonnes of COin the Burqan and Umluj

units of the Al-Wajj basin. Our simulation includes a modified fluid model of COsolubility in brine, that

is capable of explicitly representing the heat exchange and flow characteristics of both dissolved COand

supercritical COwithin the reservoir, unveiling a close connection between the heat recovery process and the

movement of the cold, dissolved COwithin the formation brine. Our study thus contributes to understanding

geostatistical reservoir modeling, for geothermal reservoirs, particularly for syn-rift submarine clastic systems.

It also provides valuable insights into the heat recovery mechanisms in COplume geothermal (CPG) systems.

Overall, this study offers a stepping stone toward the sustainable harnessing of geothermal energy recovery

and COstorage to reduce carbon emissions in the energy sector.