Sealing Wellbores at the End of Their Lifecycle to Restore Subsurface Seal Integrity and Enable Safe Ccus

As we approach 2020, there are more wellbores that require abandonment than wellbores waiting to be drilled. The USA alone has ~1.7 Million wellbores with an API number indicating that they are not permanently plugged, therefore will be in need of Plugging and Abandonment (P&A) at some point in the future. Some of these wellbores are located in fragile ecosystems, such as the Gulf of Mexico, where it is estimated that 9,000 idle wellbores are waiting permanent plugging and abandonment. The numbers of future P&As suggest requirement for an urgent improvement of current technology as many governments are preparing standards that require assurance for zero leakage over thousands of years.

This paper/talk will present knowledge gaps we identified during literature review and the data obtained during first two of the ongoing project , under NASEM-GRP funding.

Extensive literature review points to the following issues:

• Portland-cement based materials, with their pH ~13, are geochemically incompatible with the reservoir conditions in the GoM.
• Weak interfaces between and contaminations with drilling fluids in wellbore structures present high risk for HC leakage, which currently cannot be mitigated successfully.
• Placement and accessibility of wellbore in offshore environment adds to technological complexity and increases the risk of leakage.
• Monitoring and verification is currently not available for long-term assessment offshore.

Some of our preliminary data suggests the following:

• Plugging materials are impacted by contaminations form drilling fluids and other wellbore materials, such as fragment of dehydrated clays, oily rock fragments.
• Casing corrosion might lead to deterioration of primary wellbore cement, which can be difficult to locate and remediate prior to plugging.
• Geomimicry is a potential path forward in designing and developing barrier materials capable of serving over thousands of year.