Engineering Excellence: How STATS Enabled OQGN's Critical Pipeline Tie-In, Oman
Tool - Remote Tecno Plug
Location - Oman
The Sultanate of Oman boasts an extensive oil and gas pipeline infrastructure, this network forms the backbone of the nation’s energy sector, driving economic growth and prosperity to the country. Nestled on the Arabian Peninsula with strategic access to the Arabian Sea, Gulf of Oman, and the Strait of Hormuz its strategic location ensures energy flows smoothly from producers to global markets.
OQ Gas Networks (OQGN) owns and operates over 4,000 km of pipelines ensuring uninterrupted gas supply to consumers across the Sultanate.
Recently, OQGN had a requirement to permanently connect a live 48-inch gas transmission pipeline to newly constructed gas blending stations, the Saih Rawl Central Processing Plant and Saih Nihayda Gas Processing, to enable rich and lean gases to be strategically segregated.
STATS Group were contracted to provide inline isolation services, utilising two Remote Tecno Plugs deployed and pigged 25 kilometers to the isolation location in tandem, to provide a leak-tight and fail-safe midline isolation of the 48” pipeline. Conventional repairs of this type would typically require the entire pipeline to be completely hydrocarbon free and nitrogen purged to enable a safe intervention, interrupting flow of gas to customers and adding extensive operational and procedural requirements resulting in significant time, environmental and cost implications.
Engineering Assessment
To fully assess the pipeline isolation project, STATS conducted an engineering study and detailed site-survey to determine the safest method of carrying out the isolation and gather critical pipeline data and dimensions. Following the study, STATS Remote Tecno Plugs were configured in a three-module train, as design analysis proved this to be the ideal configuration to allow the tool to negotiate multiple bends, travel the 25 kilometres to the isolation location and provide fail-safe double block and monitored isolation.
To verify functionality for the onshore operations, all equipment was subject to a client-witnessed Factory Acceptance Testing (FAT) program at STATS operational facility in Abu Dhabi, UAE. Tests were performed using a custom-designed test fixture that replicated on-site conditions. Upon the successful completion of all FAT operations, the equipment was mobilised to the site in preparation for the pipeline isolation and tie-in operations.
On-Site Deployment
Upon arrival at site and completion of the isolation plug pre-deployment checks, the Remote Tecno Plugs were installed into the launcher and pigged with gas to the isolation location, during this operation the isolation plugs were constantly monitored and tracked to the exact location and accurately positioned using through-wall communication. An extremely low frequency (ELF) inductive system hydraulically sets and continuously monitors the isolation plug throughout the isolation.
To ensure exact positioning of the isolation plugs in the pipeline the process involved pigging the first Remote Tecno Plug 150 meters downstream of the 24’’ bypass line, then closing the Block Valve Station (BVS) to redirect the flow through the 24’’ bypass line. Subsequently, the second Remote Tecno Plug was loaded and pigged to the 24’’ bypass line. Finally, both isolation plugs were pigged together slowly to the set location.
With the first Remote Tecno Plug at the desired set location, gas flow was stopped halting pigging allowing the isolation plug to be hydraulically activated, energising dual seals and taper locks. To position the second isolation plug to the dedicated set location, the client used STATS patented mechanical strap clamp to provide a 2” offtake to flare a small volume of gas allowing the isolation plug to slowly reach the desired position. Venting pressure from between the Tecno Plugs allows the rear plug to be tracked from outside the pipeline to the exact isolation position.
Mechanical Strap Clamp
The strap clamp provides a localised seal on a pipe surface with a flanged offtake, this enables hot tapping (drilling) into the live pipeline to provide a vent point for flaring the gas between the isolation plugs. The strap clamp is simple to install and avoids the need for welding. In addition, due to the simple mechanical installation, the clamp can be removed later in the process, once the pipe section is vented and cut out.
Double Block Isolation Seal Testing
Once the isolation tools are accurately positioned, they are hydraulically activated, which compresses the isolation plug causing the dual elastomer seals to radially expand against the inside of the pipe and taper locks to grip the inside of the pipe. Large section elastomer seals provide excellent sealing properties even in pipelines with poor pipe surfaces and are engineered to suit corrosion or ovality issues.
During the isolation setting procedure the dual seals of the Tecno Plug are independently tested with full pipeline pressure, as the gas between the isolation plugs is flared to ambient a pressure differential is generated across the plug module. As the pressure differential is applied, the trapped pipeline content in between the seals (annulus) is compressed due to the seal compression. This process tests the secondary seal in-situ to above the pipeline pressure, in the correct direction. This proves the integrity of the secondary seal. The annulus is then vented to ambient and locked-in. This allows the primary seal to be tested to the full differential pressure. The isolation is then monitored for an extended period. Once successfully completed, the isolation certificate is issued by STATS to allow the safe breaking of containment. Throughout the isolation process communication is maintained with the Tecno Plugs to constantly monitor and confirm leak-tight isolation.
Fail-Safe by Design
The fail-safe design of the Remote Tecno Plug uses differential pressure acting on the plug to energise the locks and seals, this is referred to as self-energisation. When the isolation plug is self-energised the isolation is maintained independently of the control system. It is, however, backed up by the hydraulic control system which maintains the pipeline isolation when the differential pressure is below the self-energisation threshold. Once the isolation plug is activated the hydraulic pressure, circuits are locked in by pilot-operated check valves and fail-safe solenoid valves. If the control system is compromised, the tool actuation mechanism will unset when differential pressure is equalised. This feature ensures pipeline integrity is maintained and the isolation plug is always recoverable upon job completion.
48in Dual Remote Tecno Plug, Midline Isolation & Pipeline Reroute, Oman
Tie-In Activities
With the pipeline back flowing with gas diverted through the 24” bypass pipeline and the midline isolation in place, a 100-metre section of pipeline between the Tecno Plugs was cut out and removed. This now provided two tie-in points to connect the bending station launcher and receiver pipelines to the existing pipeline.
Upon completing the tie-in at both locations, the isolation certificate was withdrawn. The new gas segregation plant at GNH was then commissioned by introducing gas and equalising it with the pipeline pressure, allowing the Remote Tecno Plugs to be passively and hydraulically unset and subsequently pigged back to the new launcher and receiver facilities.
Launcher Tie In
We successfully completed this critical pipeline isolation using proprietary inline isolation tools, enabling a short section of pipeline to be safely isolated at 90 bar. This was achieved without interrupting gas supply to customers and without venting hundreds of kilometers of methane, delivering both operational efficiency and environmental protection. This operation enabled OQGN to complete the 48” tie-in between the Saih Rawl Central Processing Plant and the Saih Nihayda Gas Processing at Gas Network Hub, permanently connecting the supply pipelines to the newly constructed gas blending station. This ensured uninterrupted gas availability for key stakeholders and delivered a milestone project safely and efficiently.
Mark Gault
