| Abstract |
The master and wing valves of a geothermal well normally encounter mechanical defects due to corrosion, deposition and wear. It is necessary to replace these valves to fully control the production and reinjection wells and to sustain operation of the power plant. Prior to master and wing valves replacement, the wellhead is depressurized to zero. It has been a practice to engage a foreign contractor to handle the plugging of the production casing prior to valve replacement. Recently, PNOC-EDC, Southern Negros Geothermal Production Field (SNGPF) introduced a TIPED Well Plugging Tool as an alternative to the plugging equipment used by the foreign contractor. TIPED mechanically plugs the 9-5/8รถ production casing, henceforth, depressurizes the geothermal wellhead. The set-up is composed of a collapsible structure, mechanical hoist and dynamometer. The push rod with a plugging tool head is lowered by a mechanical hoist while maintaining a differential force against the uplifting pressure of the well. The dynamometer installed at the end of the wire rope cable indicates the applied pull requirement. A conical rubber at the head assembly sets and seals the top of the 9 5/8-inch production casing. The structural assembly is supported with a main anchor clamped at the 20-inch surface casing of the wellhead. The TIPED Plugging Tool has been successfully used in SNGPF in depressurizing geothermal wells and eventually in replacing the defective master and wing valves. |