With the global push toward net-zero carbon emissions, oil and gas production will begin to decline, leaving behind thousands of abandoned wells that need to be addressed. In that respect, Pawnee Nation has taken the initiative to handle this vast inventory by converting old oil and gas wells into geothermal wells. Repurposing these wells offers significant cost savings, as they do not require drilling and typically demand minimal completions to be made suitable for geothermal use. However, before repurposing, a comprehensive risk assessment is essential to preserve well integrity and prevent aquifer and surface contamination. An effective method for identifying these risks is through the integration of the Feature, Event, and Processes (FEP) framework with the Interaction Matrix (IM), Incident Potential Matrix (IPM), and Cause-Effect plot diagram. Critical elements within the well system are first identified using the FEP, then placed in the IM to assess the effect of one element on another. The IPM assigns a risk value based on severity and probability, as determined by experts in the field. After the risk values are established in the IM, a cause-effect calculation generates a plot that indicates which elements are critical and have the potential to compromise well integrity and cause catastrophic events. This risk assessment exercise enables the implementation of remedial measures in advance, ensuring the well is suitable for retrofitting into geothermal applications.

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