TDW Offshore Services announced that it has completed a pipeline pressure isolation operation in Qatar on behalf of a major supplier of liquefied natural gas (LNG).
The operation took place at the customer’s LNG complex in Qatar. Natural gas is transported from platforms offshore Qatar through seven LNG trains to this complex. In order to facilitate replacement of a defective emergency shutdown (ESD) valve on a primary export line, pressure isolation services were required. The 38-inch diameter pipeline runs from two wellheads in the offshore natural gas condensate field to the onshore LNG processing facility.
To isolate the pipeline section located upstream of the designated ESD valve, TDW launched two 38-inch SmartPlug ® isolation modules using an existing pig-receiving trap located onshore at the receiving end of the export pipeline. Using its remotely-operated SmartTrack™ tracking and pressure-monitoring system, TDW monitored the location of each module as it travelled 600 meters along the pipeline route, as well as the pressure of the pipeline. One module was positioned upstream of the designated ESD valve, and the other downstream of the valve. The TDW team then set the modules and safely isolated the affected section so that the modifications on the ESD valve could be safely carried out.
Pipeline safely isolated for eight days
For eight days, the SmartPlug modules remained in the pipeline. Upstream pipeline pressure was maintained at 85 bar (1232 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. Once the ESD valve bypass repair work was completed, the set SmartPlug modules were used to locally hydrotest the integrity of the completed work to a pressure of 120 bar (1740 psi). Once the customer was satisfied that the ESD valve bypass repair work was successfully completed, TDW unset the isolation modules, promptly retrieved all equipment, and demobilized.
“ Our goal is to assist customers by making certain that their assets operate efficiently, safely and cost-effectively ,” said Enzo Dellesite, Director, Market Development-Offshore for TDW . “The isolation operation carried out for this valuable customer played a pivotal role in facilitating safe replacement of this critical emergency shutdown valve. The fact that the SmartPlug isolation modules performed well and the TDW team worked so effectively with the customer’s team meant that we were able to create a safe environment in which to replace the valve, ” he added.
The entire operation was achieved without flaring product or venting the line, which meant that costs were substantially reduced and that the environment was not adversely affected. It was a great success on every front,” he added.
[mappress] LNG World News Staff, April 16, 2012; Image: TDW Offshore