Research explores CO2 storage in North Oman

Observer

23-03-2025

MUSCAT, March 23
The work of Principal investigator Dr Mingjie Chen, Researcher at Sultan Qaboos University (SQU), is among the winning innovative research projects at the 11th National Research Award, organised by the Ministry of Higher Education, Research and Innovation (MoHERI).
The researcher won for his work in the energy and industry field in the PhD category, titled 'Use closed reservoirs for CO2 storage and heat recovery: A two-stage brine-extraction and CO2-circulation strategy.'
Dr Mingjie mentioned that integrated CO2 (carbon dioxide) geologic storage (CGS), and CO2 plume geothermal (CPG) production provide an attractive approach not only to reduce atmospheric CO2 concentration but also to generate carbon-free geothermal energy to supplement electricity power. Small to moderate scale closed-boundary reservoirs have rarely been evaluated for CGS-CPG. One of the major reasons is that the closed system has limited storage volume, and native brine has nowhere to escape to free storage space for injected CO2.
For this study, Dr Mingjie and his research team aimed to provide a solution to the issue by implementing an innovative two-stage operational strategy to realise CGS-CPG in closed fault-blocks in oil/gas fields in North Oman.
Dr Mingjie Chen, SQU Researcher, and Principal investigator
The proposed strategy extracts pure hot brine and CO2 in two sequential stages by two separate horizontal wells and can effectively avoid brine-CO2 separation on ground surface. A suite of numerical models is developed to evaluate the approach with a variety of reservoir conditions and operations.
The main findings revealed that CO2 sequestration is achieved mainly during the CGS stage, and supplementary during the CPG stage, in which negative net storage could happen in situations of extremely low porosity and high extraction rate. During CGS, the higher the porosity, the more the store CO2. The higher the regulated overpressure, the more the compressed CO2 in the pore space freed by produced brine. The largest CO2 storage achieved is 6.1 Mt in 16 years of lifespan for the simulation with highest porosity and overpressure.
Moreover, the total recovered heat energy from produced hot brine and circulated CO2 is determined merely by porosity and increases almost linearly from 2.2 to 3.6 (×1015 Joules) with it, whereas the heat flux averaged in the lifespan (thermal power capacity) is controlled by both permeability and overpressure, varying from 0.5 to 7.5 MW with the increase of both parameters.
Dr Mingjie also added that the IW-PW2 (injection well-CO2 production well) well space (L) should not be larger than 500 m in order to meet the required 0.94 of minimal CO2 cut in produced fluids from PW2.
Under this constraint, the total heat energy from CO2 circulation is controlled by L only and can reach up to 6×1015 Joules. The CO2 thermal power capacity, however, is controlled by extraction rate (Q), and almost linearly increases from 2 to 7 MW with Q from 6 to 18 kg/s.
The results demonstrated the feasibility of our solution for implementing CGS-CPG in closed underground reservoirs, and indicate the tremendous potentials to use depleted oil/gas reservoirs as the candidate fields, which widely exist in North Oman and the world.
Comprehensive economic evaluation using Levelised Cost Of Energy (LCOE) and Net Present Value (NPV) are undergoing for the proposed approach: paving the way for pilot-scale field experiments and possible commercialisation.
This research project was published in Sustainable Energy Technologies and Assessments. The research team consisted of Dr Mingjie along with Dr Ali al Maktoumi, Dr Azizallah Izady from Sultan Qaboos University, Prof Jianchao Cai from China University of Petroleum, and Dr Yanhui Dong from Chinese Academy of Sciences.