| Title | Reducing casing heatup rates in geothermal production wells by using coiled tubing gas lift |
|---|---|
| Authors | M.J. Sophy, P.F. Bixley, K. Newman, D. Wilson, T. Ryan |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Vertical Discharge, Casing, Coiled Tubing |
| Abstract | After drilling completion, geothermal production wells are allowed to heat up for some time, then discharge tested to remove drilling debris and determine well output characteristics. Vertical discharge is a practical and inexpensive method of conducting the initial flow test. However, in some cases this method can result in rapid, uncontrolled heating of the casing with increased potential for casing damage or failure. While it is preferable to heat the casing slowly, this is not always possible and wells may be opened from zero to 100% flow in a few minutes with associated casing temperature changes in the order of 200°C. Some wells have static temperature conditions with up to 800 meters of <150°C above hot 300°C reservoir. The cold column of water can be difficult to heat to saturation temperature required for boiling and initiation of self discharge. To reduce the heating rate and have better control of the flow it is now common practice to initiate well discharge using coiled tubing with air or nitrogen gas lift. Recently Contact Energy have used Western Energy’s coiled tubing unit to initiate flow in several otherwise difficult-tostart wells. During two of these jobs a temperature-pressure gauge was attached to the bottom of the coiled tubing stringto record actual downhole conditions while initiating flow. This paper compares heatup rate between “traditional” uncontrolled well discharge and that measured during a coiled tubing airlift. |