Submarine pipelines play a crucial role in extracting and transporting oil and gas resources located far beneath the ocean floor. By connecting offshore oil and gas production platforms to onshore terminals, these pipelines enable the economical development of vast subsea reserves. With careful engineering and construction, submarine pipelines can operate reliably in some of the harshest marine environments on Earth.
Types of Submarine pipelines
There are two main types of submarine pipelines depending on the product they transport:
Oil Pipelines
Vast networks of submarine pipelines transport crude oil from offshore oil production platforms to onshore refineries. These pipelines typically range from 6 to 48 inches in diameter. Pipeline materials must withstand exposure to corrosive crude oil while maintaining strength and flexibility to withstand ocean currents and pressures at deep-water depths.
Gas Pipelines
Natural gas pipelines also crisscross sections of the continental shelf, though gas is sometimes processed and exported as liquefied natural gas (LNG) via offshore LNG terminals and tankers. Offshore Pipeline require special coatings and cathodic protection to prevent corrosion from humid natural gas over long periods of offshore operation.
Engineering Challenges of Offshore Pipeline
Submarine pipelines present unique engineering challenges compared to onshore pipelines due to harsh ocean environments:
Deepwater Installation
Pipelines installed in deep waters over 1,000 feet deep require specialized pipe-laying vessels and techniques. Remote operated vehicles (ROVs) assist with tasks like welding pipe joints in difficult conditions.
Harsh Conditions
Ocean currents, storm surge, earthquakes, freezing temperatures, and corrosion from seawater and cargo pose continual threats. Pipelines must flex but not fracture under pressure.
Weight Coatings
To prevent pipe buoyancy in deep waters, concrete or rock weight coatings are often applied. Pipe-lay barges precisely place the heavy coated pipe on the seafloor.
Seabed Stability
The seafloor geology impacts design and requires anchoring or burial of pipelines below areas prone to slides, slumps, or mudflows. Trenching machines bury the pipe for stability and protection.
Third Party Impacts
Heavy ship anchoring or fishing nets can damage exposed pipelines, requiring monitoring tools like pressure sensors or pipeline trackers to locate breaks.
Construction of Offshore Pipeline
Submarine pipelines are carefully constructed using complex vessels and remotely operated tools:
Pipeline Fabrication
Pipe joints are welded onshore then loaded onto pipelay or reel vessels for offshore installation. Welds must maintain strength in tough conditions.
Lowering to Seafloor
The pipe, often coated with concrete, rock, or corrosion-resistant coating is unwound or lowered through a vertical or horizontal pipe-lay process. Pipe-lay barges precisely place each joint.
Trenching and Backfilling
For stability, some pipelines are buried below the seabed using water jets or mechanical plows to cut the trench, then the trench is backfilled once the pipe is in place.
Testing and Commissioning
After installation, pipelines undergo hydrotesting to check for leaks. Remotely operated vehicles (ROVs) inspect welds. When testing is complete, pipelines are fueled with product and commence operation.
Integrity Management of Offshore Pipeline
Due to the challenges of accessing submarine pipelines, ongoing monitoring systems help ensure integrity:
Cathodic Protection
An electric current helps prevent external corrosion of pipelines through protective coatings and sacrificial anodes installed along the pipe.
Pipeline Pigging
Inspection “pigs” periodically travel inside pipelines using differential pressure to capture debris or inspect for corrosion, deformation, or cracks using sensors, cameras and magnetic field testing.
Leak Detection Systems
Computerized systems monitor flow rates and pressures, using algorithms to detect small leaks before they become catastrophic failures and surface spills. Acoustic listening devices and aerial surveys supplement monitoring programs.
Repair and Replacement
Major damage requires robots to cut out pipe sections for repair or replacement offshore. Remotely operated vehicles weld new joints or install mechanical clamps, sleeves or other repair technologies before repipelining.
As offshore oil and gas reserves located far beneath the sea continue fueling global energy needs, engineers will develop new submarine pipeline technologies to enable exploration of even deeper reservoirs. With careful planning, construction, monitoring and repair, submarine pipelines can reliably extract subsea energy resources for decades, powering economic growth while meeting environmental and safety standards. When decommissioned, pipelines will be cleaned and portions recovered or abandoned in place according to regulations.
*Note:
1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it
