Novel Coiled Tubing Operations in A Hostile Thermo-Chemical Environment


Santiago ROCHA, Louis CAPUANO III, Louis CAPUANO Jr., David FAULDER, Patrick WALSH

Key Words:

Salton Sea, scale removal, workover, coiled tubing, open hole cleanout, hot mud motor, workover efficiency, high enthalpy reservoir, Hudson Ranch


Stanford Geothermal Workshop







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The production wells at Hudson Ranch 1 produce a 600°F hypersaline brine from the Salton Sea geothermal reservoir. The produced brine is 25-30 wt% dissolved solids and is highly corrosive with a strong scaling potential. Wellbore scaling has been observed in the casing, at the flash depth, and where secondary fluids enter along the open hole. In the cased interval of the wells, cleaning out the accumulated wellbore scale and debris presents many different challenges due to variations in mechanical properties and configurations of the casing. In the open hole, production interval cleaning challenges are complicated by intervals of hole instability, and long open hole intervals necessary to reach the bottom production zones. Cleanouts using a coiled tubing (CT) unit are less than 20% of the cost of a cleanout using a drilling rig. Past operators have used CT with either a hydroblasting head or a downhole mud motor in either a static or flowing well, but always in the cased hole. Cyrq Energy, working with consultants, has performed groundbreaking cleanouts in the open hole of production and injection wells using all Metal Mud Motors (MMM), a technique here described as Hot Mud Motor (HMM) method, as the tool is run while the well is flowing with hot production brine. This paper discusses historical well cleanouts, root cause failure analysis, and risk assessment performed to achieve more than 10 CT cleanouts, some with over three thousand ft. of open hole through a fracture-dominated formation. The risk assessment includes the appropriate selection of CT size, workover technique, Bottom Hole Assembly (BHA), bit size selection, and operational parameters. These successful operations prove the effectiveness of CT and HMM at the Hudson Ranch project with careful planning, significant cost reduction compared to rig cleanouts, a reduction of mechanical risk, and increased operational safety.

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