STATS provides hot tapping, isolation for Middle East and Thailand subsea pipelines

Feb. 15, 2023
STATS Group provided pipeline isolation, hot tapping and plugging services to what it called "the world’s largest diameter subsea pipeline intervention" project in the Middle East.

Offshore staff

ABERDEEN, UK — STATS Group was commissioned by EPC contractor National Petroleum Construction Co., a subsidiary of National Marine Dredging Co., on behalf of a National Operating Co., in December 2022 to provide pipeline isolation, hot tapping and plugging services to what STATS called "the world’s largest diameter subsea pipeline intervention project."

The scope of work will include the hot tapping and double block and bleed isolation of multiple pipelines with diameters ranging from 42 inches up to 56 inches in the Middle East region, using STATS SureTap hot tapping machines and its BISEP technology.

Mark Gault, STATS Group’s General Manager Middle East, said, “We believe this project to be a first in the world. As far as we are aware, there have been no other subsea intervention projects of this complexity or scale that involve subsea isolations on pipelines of 56” diameter. We have made a significant product development investment with three new large-diameter hot tapping machines and the associated isolation assets capable of handling this unique work scope. Relatedly, we are delighted to have increased our BISEP DNV Type Approval status up to 56”.

Gulf of Thailand

A couple days ago STATS Group carried out a double block isolation of a 24-inch gas pipeline operating at a pressure of 121 bar in the Gulf of Thailand.

STATS used a DNV-GL type approved Remote Tecno Plug to provide a fully monitored leak-tight isolation allowing two 4-inch cold taps to be conducted, providing future tie-in points as part of a larger modification project.

In advance of the workscope, STATS conducted a site survey on the platform to gather critical information and complete a noise survey to confirm there would be no interference with the plug communication system. The site survey information allowed STATS to produce a detailed engineering and piggability assessment. This confirmed the specification of the Remote Tecno Plug and identified a suitable isolation location.

STATS also conducted a full Factory Acceptance Test (FAT) at its headquarters in Aberdeenshire, in a purpose-built test-fixture with all testing witnessed by client representatives. Once the Remote Tecno Plug arrived on the platform, it was loaded into the pipeline launcher. The isolation plug was then pigged with nitrogen through the pressurized pipeline and tracked a distance of 70 m, through six 3D bends to the desired set location. Communication with the Tecno Plug is achieved using an extremely low frequency inductive system for reliable tracking and accurate positioning.

At location, the Tecno Plug was hydraulically set to activate the locks and dual seals. The dual seals of the Tecno Plug were then independently tested with full pipeline pressure in the correct direction to confirm leak-tight isolation and allow the pipeline to be bled down to ambient from the platform launcher to the rear of the Tecno Plug. The annulus between the Tecno Plug seals is then vented to ambient to create a zero-energy zone. This was then subject to a 12-hour isolation stability hold period before the "Isolation Certificate" was issued.

With the isolation in place and the double block and bleed isolation verified, the STATS technicians then safely conducted two 4-inch cold taps on the 24-inch pipeline. Due to the thickness of the pipe wall, a significant volume of swarf would be produced during the tapping operation. To minimize the volume entering the pipeline, the cold tapping was conducted in stages to allow the cutter to be retracted to allow the swarf to be cleared prior to completing the cut and removing the pipe coupon, STATS said.

Throughout the workscope, the Tecno Plug was constantly monitored and remained stable for the full nine-day isolation period. With the workscope successfully completed, the pipeline pressure was equalized, and the company said the Remote Tecno Plug was unset and pigged back to the launcher for demobilization.