Case Study: Mature Wells Given New, Carbon-Storage Purpose With Subsurface Data
Authors: Hoskin Ed 
Published: December 2022

To ensure success in exploration and production activities, oil and gas companies rely on subsurface data to gain insights that guide operational decisions over the life of their wells. But as wells near the end of their lives and production slows or stops, wells are subsequently shut and abandoned, and the accompanying subsurface data are set aside. However, these data still hold tremendous value when it comes to evaluating mature, near-end-of-life wells and fields to determine if they are suitable candidates for carbon capture, utilization, and storage (CCUS). Reusing wells and fields for CO2 injection provides an opportunity to reduce the time and cost for developing new CCUS infrastructure required by energy mix diversification efforts while avoiding the steep expenses commonly associated with decommissioning.
In most cases, when the production cycle ends and all usable hydrocarbons have been extracted, the topside facilities are dismantled, the wellbore is permanently plugged and abandoned, and the surrounding land or seabed is returned to its natural condition. Historically, this complex, multistep process has been a cost center for oil and gas businesses, requiring monumental investment that grows even higher for offshore and deepwater fields.
However, now that the CCUS industry is aggressively expanding, operators are presented with the possibility of turning decommissioned wells into a profit center by selling CO2 storage capacity to others. CO2 storage is a crucial component of the CCUS value chain as permanently storing CO2 is the cornerstone of large-scale emissions reductions. The storage process entails capturing, compressing, and injecting CO2 into a reservoir of porous rock beneath an impermeable layer of caprock, which functions as a seal. The caprock prevents the CO2 from reaching the surface, as do other trapping mechanisms including structural, residual, solubility, and mineral trapping. As a result, CO2 is safely stored in geological formations. This is similar to the unexplored state of oil and gas reserves trapped underground for millions of years.
Carbon-storage processes are not a new concept in the oil and gas industry. As part of normal well operations, operators routinely perform the CO2 injection enhanced oil recovery (EOR) technique. If CO2 returns to the surface and is separated and then reinjected to form a closed loop when utilizing this EOR method, this results in permanent CO2 storage, which strongly supports the viability for repurposing mature decommissioned wells.
In response to growing interest in CCUS and governments worldwide committing to reach a net-zero target for CO2 emissions in the coming decades, a consortium of 20 organizations including research institutions, operators, and regulatory authorities joined together to create REX-CO2 (ReUsing Existing Wells for CO2 Capture and Storage). As part of the REX-CO2 consortium, Ikon Science collaborated with the British Geological Survey (BGS) in the phases of a study that evaluated the potential for well reuse in the UK Continental Shelf (UKCS). It’s forecast that 1,211 wells across 230 fields will be decommissioned through 2028 in the UKCS to the tune of $60 billion, according to Britain’s Oil & Gas Authority’s 2021 Decommissioning Cost Estimate report.