Shell: Mitigating Methane Emissions through Decommissioning High-Risk Sources

Abandoned wells do not leak at the same rate, and the available information about them can vary widely. We started the proposal with a screening step that ranked wells by the available evidence of methane release, site access, and whether the suspected leak was near a component that could be repaired with the materials we were evaluating.

We limited the intervention to wells with suitable leak paths and accessible wellhead components. Each site would still need an inspection before repair, and wells with structural leakage deeper below ground would move into a different remediation process.

Our proposed intervention used accessible materials, including PTFE tape and pipe sealants, to improve seals around suitable leak paths. Based on the assumptions in our analysis, we estimated that the intervention could reduce emissions from targeted wells by roughly 50 percent. We presented that figure as an estimate tied to the selected conditions, because well construction and deterioration differ from site to site.

The material choice came from the need for a low-cost measure that could be deployed with common tools. We also placed it within a broader decommissioning strategy, since sealing a fitting cannot resolve structural leakage deeper in a well or replace the inspection required to identify the actual source.

We compared the cost of applying the intervention with the environmental and financial cost of allowing leakage to continue. The analysis included the labour and materials required at each site and the value of concentrating work on higher-emitting wells, where the same field effort could prevent more methane from entering the atmosphere.

In the final proposal, we set out a sequence for screening wells, checking whether the leak path was suitable, applying the seal, and measuring the result. That sequence also made it clear where the low-cost repair stopped being appropriate and a larger remediation job had to take over.