Responsible for providing Thailand with 20% of its annual natural gas supply, PTTEP needed to replace the valves with a minimum of downtime to ensure that natural gas production from its Bongkot and Erawan production platforms in the Gulf of Thailand would continue to flow with little disruption.
The three topside valves in need of replacement were located on the gas export riser attached to the Bongkot platform, which is connected to a major export line that extends to the Erawan production platform, a primary hub of gas production in Thailand.
TDW’s job was to isolate pressure in the pipeline from the work zone and to depressurize the affected section. By doing so, a safe working environment would be created in which the pipeline repair contractor could replace the defective valves and interruption to gas production could be kept to a minimum of no more than 10 days.
The TDW team deployed a triple module 32-in. SmartPlug pressure isolation tool. The triple-module configuration features two modules for isolating the pipeline inventory during the valve replacement works, and a third plug module to act as barrier for post-repair hydrostatic testing.
Working from the Bongkot platform, TDW launched the SmartPlug tool into the line, pigging it in potable water for 40 m (131 ft) past the hanger flange and into the vertical set location in the riser. As it traveled through the line, TDW tracked the tool’s progress with its remotely operated SmartTrack tracking and monitoring system. Upon setting the isolation tool at the pre-determined destination, it was sealed against a safe operating pressure of 100 bar (1,450 psi) for 10 days.
With the line safely isolated, the two valves were replaced during the isolation period and then the company carried out a hydrotest to a pressure of 132 bar (1,930 psi) against the tool’s third plug module to verify the integrity of the repair work. With the hydrotest completed and integrity of the repair work verified, the operation was completed.
The pressure over the SmartPlug tool was then equalized, the plug modules unset, and the tool pigged back to the launcher using the gas pressure from the pipeline. Finally, the pressure was bled at the launcher side.