Case study – Fishing a geothermal pump stuck at 2067 meters depth

When something goes wrong in geothermal operations, the corrective measures must be done in a way that causes no further damage to operational assets. In the case of well interventions, one of the top priorities is ensuring that the integrity of the well is not compromised. This is showcased in this case study by French drilling company Enedril where a downhole pump had to be fished out of a well.

Geothermal energy is emerging as one of the most promising solutions for the energy transition. Yet, harnessing underground heat requires complex infrastructure and delicate maintenance operations.

Among these, fishing—the retrieval of equipment stuck at the bottom of a well—is one of the most challenging maneuvers. A recent case illustrates the technical hurdles involved, as well as the sometimes unexpected solutions that ensure production continuity.

During the retrieval of a submersible pump installed in a geothermal well, almost the entire piece of equipment became stuck at great depth. Initial hypotheses suggested that the pump was either lodged at the junction between the 13-3/8’’ and 9-5/8’’ casings, or blocked inside the 9-5/8’’ casing due to the presence of power and treatment cables. The challenge was twofold: precisely locating the pump and defining a fishing strategy that would not compromise the integrity of the well, which was essential for ongoing exploitation of the resource.

Several scenarios were considered: the pump might have fallen to the bottom and come to rest in open hole, become stuck on a casing cut at 254 m, or been jammed by residual cables. These uncertainties made planning complex and required the anticipation of multiple technical strategies.

Options ranged from recovering the pump body with a large-diameter overshot, to retrieving the central shaft with smaller tools, or fishing for the cables with a harpoon. As a last resort, milling of the casing or pump was considered—a heavy and risky solution.

The first attempts proved unsuccessful. Neither the 8-3/8’’ overshots used externally nor the smaller tools targeting the pump shaft managed to free the equipment. The main difficulty lay in the depth of the intervention—over 2,000 meters—and the limited capacity of the rig, which prevented efficient maneuvering at that depth. Faced with these setbacks, the teams began considering milling, viewed as the last resort.

In the end, the solution came from a much simpler approach. By using an overshot of only 3-7/8’’ fitted with a small 1-3/8’’ grapple, operators managed to hook onto the pump’s shaft, held in place by two circlips. Against all odds, the pump was successfully extracted the very next day.

Beyond the technical anecdote, this operation highlights the strategic importance of maintenance in geothermal energy. Each successful intervention helps extend the life of installations, secure energy availability, and guarantee project profitability. In a context where renewable heat is expected to play a central role in decarbonization, mastering such operations is crucial.

This case study also serves as a reminder that successful fishing relies as much on the ingenuity of the teams as on the tools at their disposal. Geothermal energy, often perceived as a silent and invisible resource, conceals behind each megawatt produced a wealth of specialized expertise. It is precisely this combination of technical robustness and operational pragmatism that makes geothermal energy an energy source for the future.