Offshore Pipelines: Enabling Deepwater Energy Production

Offshore pipelines play a vital role in transporting oil and gas from deepwater production facilities to onshore terminals and refineries. As energy companies move into deeper offshore reserves, these subsea pipelines are becoming increasingly complex yet essential infrastructure.

Deepwater Production on the Rise
Fuelled by advances in drilling and production technologies, oil and gas companies have been pushing the boundaries of deepwater exploration over the past decades. According to industry estimates, deepwater oil production is expected to grow from 5 million barrels per day currently to over 8 million barrels per day by 2030.

Subsea pipelines are critical to transport hydrocarbons from these remote deepwater production hubs cost-effectively to onshore facilities. As fields are located further away from shore in deeper waters, longer and more advanced pipelines are needed.

Pipeline Route Planning and Construction
Extensive planning goes into deciding the route of an Offshore Pipeline. Factors like water depths, seabed conditions, presence of obstructions, proximity to existing infrastructure and environmental concerns are evaluated.

Detailed surveys mapping the seafloor terrain and subsoil conditions are conducted to identify the most optimal route. High-resolution 3D seismic surveys help detect geohazards.

Specialist pipelay and construction vessels are used to install these pipelines. Modern dynamic positioned pipelay barges can operate in water depths over 3,000 meters. Remote operated vehicles guide the pipelines through the seafloor while trenching tools bury sections for protection and stability.

Materials and Coatings
The choice of pipeline material depends on factors such as water depth, distance to shore, fluid transported, pressures involved and loading conditions. Carbon steel remains widely used but high-strength alloys are preferred for deeper waters and sour service lines.

Coatings protect the pipelines and extend their operational life by preventing corrosion in the harsh offshore environment. Three-layer polypropylene and concrete weight coatings are commonly used. Active corrosion protection through impressed current or galvanic anode systems provides long-term cathodic protection.

Flow Assurance and Pigging
Ensuring efficient flow of hydrocarbons over the pipelines' lifetime requires addressing issues around wax, hydrates, erosion and build-up of solids inside. Chemical injections and heating systems maintain the flowing stream in a single phase.

Pipeline cleaning or "pigging" removes any accumulated solids, liquids or gases through launcher and receiver facilities. Smart pigs equipped with sensors also perform in-line inspections to detect corrosion, cracks or damage.

Subsea Connections and Manifold Systems
Multiphase flows from multiple subsea template manifolds have to be commingled, processed and transported through flowlines to the host platform or export pipelines.

Specialized subsea connection systems relying on automated welding, bolt-together or clamp-type connectors join the flowlines and risers. Manifold clusters consolidate production from separate satellite wells into co-mingled pipelines laid on the seafloor.

Tie-ins of new pipelines to existing network infrastructure require sophisticated intervention and installation methods using divers, ROVs and flex-lay barges to minimize disruption. Subsea isolation valves enable sections to be closed off for maintenance.

Perforated Pipe Technology Enabling Deeper Reserves
As energy firms aim to produce from reservoirs over 3,000 meters water depth with ultra-high pressures, conventional rigid pipelines may not always be suitable.

Perforated or pre-laid pipe-in-pipe technologies are attracting interest for such environments. These use centralizers to install a production pipe within a carrier pipe across the seafloor. Gaps between the two allow reservoir fluids to directly enter the inner pipe under gravity and pressure.

Benefits include reduced wall thickness, simpler installation and freedom from dependency on boosting systems. However, long-term integrity requires monitoring fluid migration between the pipes. Ongoing engineering research is advancing these perforated pipe designs.

Offshore pipelines underscore the offshore energy industry's remarkable capabilities and innovations that have made previously inaccessible resources economically producible. As deepwater frontiers are pushed farther, pipeline technologies will continue expanding to keep hydrocarbons reliably flowing.