KNOWLEDGE HUB
Carbon Capture and Storage (CCS) Considerations for Well Decommissioning
Future-Proofing Reservoirs
As the global energy transition accelerates and CCS becomes more established, well P&A has more guidelines to follow. It is increasingly seen not only as the permanent isolation of reservoirs, but also a critical step in preparing geological formations for Carbon Capture and Storage (CCS). The objective of CCS is to capture carbon dioxide from industrial sources, transport it offshore, and inject it into underground reservoirs—specifically at depths between 800 and 3,000 metres due to the supercritical phase of CO₂—for permanent storage. The Lean Decom curriculum provides the essential decision context for this shift, framing decommissioning as a transition where current activities must account for future injection requirements.
The Technical Requirement: Minimum Safe Abandonment Depth (MSAD)
One of the most critical factors in future-proofing a well for CCS is the Minimum Safe Abandonment Depth (MSAD). This is the specific depth below which abandonment plugs must be placed to ensure the formation can withstand the pressure of injected CO₂. If a plug is set too shallow, the injection pressure could fracture the formation, creating a leak path to the seabed.
In Emma Dawson’s class, you will develop a detailed understanding of how to calculate MSAD graphically. This involves taking the maximum reservoir pressure and extrapolating a CO₂ fluid gradient up to the point where it reaches the formation breakdown pressure. Only by ensuring plugs are placed below this line can an operator guarantee that a well is suitable for future CO₂ injection.
The Risk of Legacy Wells
A significant challenge in developing CCS clusters is the presence of legacy wells drilled between the 1960s and 1990s. These wells were often not abandoned to modern standards; frequently, only the primary reservoir was isolated, leaving secondary flowing formations above it unsealed.
If these legacy wells are located near a future CO₂ injection site, they must be meticulously evaluated and potentially remediated. Without proper isolation of all potential flow zones, these older wells could serve as high-risk leak paths for the stored carbon. Developing the ability to identify these “at-risk” wells is a core component of the subsurface readiness.
The Role of Data Archaeology
Future CCS projects rely heavily on data archaeology. Finding accurate records for wells that are 40 or 50 years old is often difficult, with many files existing only as faded paper records. To reduce future costs and increase efficiency, it is now a global expectation that current decommissioning activities include meticulous documentation of:
- Exact plug depths and thicknesses
- Verified casing and cementing requirements
- Clear schematics of all zones with flow potential
Properly documenting these abandonment schematics today ensures that future CCS developers have the information required to utilise a reservoir without having to undertake expensive, exploratory re-entry operations.
Interdisciplinary Communication and Strategy
The transition to CCS-ready decommissioning requires breaking down the traditional silos between wells teams and subsurface teams. Insights from real-world projects show that critical details can be lost in translation if these departments do not maintain constant communication.
Decommissioning Training
By taking the Lean Decom decommissioning training course, you will acquire insight into how to manage these complex interfaces and align your decommissioning strategy with global requirements, such as the EU mandate for carbon storage by 2050. Gaining this real-life understanding of the “final chapter” of an asset’s life allows professionals to make fit-for-purpose decisions that protect the environment and preserve the commercial viability of future energy projects.