- Oil wells could be a suitable location for CO2 storage
- Reuse can benefit projects in terms of cost reduction but poses some risks such as leakage and CO2 corrosion
- A number of projects are aiming to determine the suitability of wells as industrial-scale CO2 storage
The carbon capture and oil and gas industries, even regulators have been looking at whether wells can be repurposed as carbon capture and storage (CCS) sites. Potentially, deploying carbon dioxide storage through the reuse of appropriate existing oil and gas infrastructure could reduce the costs of developing a CCS network.
In theory, redundant oil and gas wells could be repurposed for CO2 injection. However, there are technical, commercial and regulatory factors, which need to be considered in assessing the potential for re-use.
Oil Wells Reuse Factors
An assessment of the storage sites would be needed, as well as a development plan. The project would also have to apply for a storage permit to the respective licensing authorities. A critical part of the work includes examining the integrity of existing wells to determine any leak potential.
According to the Project Acorn Well Reuse Factsheet, costs and risk are the key commercial considerations for a well reuse. If reusing an existing well costs less than drilling a new one, then the utilization is viable.
The costs associated with the reuse of wells kept into consideration are an assessment of wellbore, casing, and completion integrity. Other costs are remedial and conversion work. In terms of efficiency, repurposing an existing well may take 7 to 21 days. Drilling a new one could last between 30 and 90 days.
Another concern regarding reusing old wells could be around CO2’s corrosivity and its impact on Portland cement normally used in well construction. Some old highly deviated cement hasn’t been designed for CCS and has a sidetrack and micro annuli. There is no guarantee of how easily CO2 would move through the well.
Projects for Oil Wells Reuse
REX-CO2 is a €3.3 million project evaluating the use of existing wells for CO2 storage. It is creating models to predict any potential leakage. The project also examines some of those issues concerning well suitability. Another well – a milestone in utilizing the possibility of CO2 storage is the Northern Light project’s 31/5-7 Eos south well. It has the potential to lock away vast volumes of liquefied CO2 underneath the North Sea.
Considerable savings could be realized by reusing wells as CO2 injectors. However, the existing well infrastructure could also pose a risk of leakages. A dedicated screening process should be led to exploit the full benefits of this potential CO2 storage solution.