DUBAI, UAE – TDW Offshore Services has completed a pipeline pressure isolation operation off Qatar.
Natural gas is transported from platforms offshore Qatar to seven LNG trains at an onshore process complex. To facilitate replacement of a defective emergency shutdown (ESD) valve on a primary export line, pressure isolation services were needed. The 38-in. (96-cm) pipeline runs from two wellheads in the offshore gas-condensate field to the LNG processing facility.
To isolate the pipeline section upstream of the ESD valve, TDW launched two 38-in. SmartPlug isolation modules using an existing pig-receiving trap onshore at the receiving end of the export pipeline.
The company deployed a remotely operated SmartTrack tracking and pressure monitoring system to map the location of each module as it travelled 600 m (1,968 ft) along the pipeline route, as well as to watch pipeline pressure.
One module was positioned upstream of the ESD valve, and the other downstream of the valve. The TDW team then set the modules and isolated the affected section to allow modifications on the valve to be safely performed.
The SmartPlug modules remained in the pipeline for eight days. Upstream pipeline pressure was maintained at 85 bar (1,232 psi) while the ESD valve bypass repair work was carried out.
During this period, TDW continually monitored the pressure of the line and pressures through the isolation modules. After the ESD valve bypass repair work was finished, the SmartPlug modules were used to hydrotest the integrity of the completed work to a pressure of 120 bar (1,740 psi).
The isolation modules were then unset, and all equipment was retrieved and demobilized. The entire operation was achieved without flaring product or venting of the line.