SINGAPORE – T.D. Williamson Inc. (TDW) reports that as a result of a complex subsea pipeline pressure intervention carried out in record time offshore Indonesia it helped prevent a major gas supply interruption in Jakarta.
The operation was the largest subseapipeline pressure intervention that TDW has ever executed. The hot tap and STOPPLE plugging operation was carried out for main contractor Timas Suplindo in cooperation with Offshore Construction Specialists on behalf of Pertamina EP, on sections of the pipeline network attached to the Lima Flow Station in the northwest Java Sea.
Work was carried out as part of the Lima Subsidence Remediation Project. The initiative aims to raise the Lima Flow Station that has been slowly subsiding into the seabed since 1997. The flow station consists of compression, service and process platforms, along with a platform bridge, flare bridge, and tower.
Stabilizing the L-PRO platform on the seabed by lifting and consolidating it made it necessary to shut down several lines connected to it. A complete shutdown would have severely disrupted the flow of natural gas from the Lima field.
To ensure that production and supply would continue uninterrupted during remediation works, several lines were to be installed to bypass the 14-in. and 20-in. MGL pipelines that extend from the TLA and TLD platforms to the L-PRO platform and the 24-in. MGL pipeline that extends between the L-PRO and Cilamaya, where the pipelines make landfall. Pertamina EP engaged TDW to isolate the affected lines so that temporary bypass lines could be installed through which gas would flow, ensuring uninterrupted supply to Jakarta.
Following the installation and commissioning of the temporary bypass lines upon the successful completion of nine hot taps, the TDW team could begin with setting the STOPPLE plugs in six different locations. Working from the dive support vessels (DSVs) at depths up to 131 ft (40 m), the five-member team used a full complement of specialist machines to hot tap the pipelines, and STOPPLE plugging systems with Lock-O-Ring Plus fittings to plug them for final completion.
Once the line has been safely isolated, cold-cutting of the isolated pipeline for the installation of subsea in-line ball valve began. In just 25 days, all of the lines were hot tapped, and the STOPPLE plugs were set and successfully isolated, making it the fastest such operation in TDW history.
For 22 days, the lines remained safely isolated at a pipeline pressure of 13.78 bar (200 psig).The entire operation was completed in just 63 days, from late July 2013 through September 2013. Natural gas flowed continuously through the temporary bypass lines to Jakarta, allowing the city to function.