Underwater Oil and Gas Pipelines
What are Underwater Oil and Gas Pipelines?
Underwater oil and gas pipelines are critical infrastructure mostly used to transport crude oil and natural gas. There are 20,000 miles of pipelines worldwide today. Constructed from steel or flexible materials, these pipelines are designed to withstand high pressure, corrosive environments, and extreme ocean conditions.
How Do Underwater Pipelines Compare to Other Methods of Transporting Oil and Gas?
| Underwater Pipelines | Tankers | Overland Pipes | |
| Cost | High initial construction cost | Moderate operational costs | High initial construction cost |
| Safety | Generally safe, but risks from leaks and corrosion | High risk of accidents, spills | Generally safe, but risks from ground leaks, vandalism |
| Environmental Impact | Moderate – potential for underwater spills, disruption to marine ecosystems | High risk of spills, carbon emissions from ships | Moderate, potential land disruption, habitat fragmentation |
| Capacity | High, continuous flow | Large, but not continuous | High, continuous flow |
| Speed | Fast, constant transport once constructed | Slower due to shipping times | Fast, similar to underwater pipelines |
How Do Underwater Pipelines Transport Oil and Gas from Offshore Platforms to Land-Based Facilities?
After oil or gas is extracted from beneath the ocean floor, it is processed on the offshore platform to remove impurities that could damage the pipeline. Once ready, the oil or gas is pumped into the pipeline using high-pressure pumps or compressors that maintain a steady flow across long distances and challenging underwater terrain.
The continuous flow of oil or gas is maintained along the length of the pipeline, which can span hundreds of miles from deep-sea drilling sites to coastal refineries, or storage facilities. The pipeline’s design takes pressure changes, temperature variations, and the potentially corrosive nature of seawater into account to ensure the integrity of the pipeline over time.
Sensors and monitoring systems track flow rates, pressure levels, and detect potential issues, such as leaks or blockages. Upon reaching land, the hydrocarbons are processed further or sent to distribution networks, ensuring a smooth transfer of resources from offshore extraction sites to global markets. Pipelines are considered highly efficient for large-scale energy production, although they pose environmental and technical challenges that require ongoing maintenance and oversight.
Can Oil and Gas Pipelines Be Used Interchangeably?
Both oil and gas pipelines are designed to transport products from sea to shore. But there are some significant differences between an oil pipeline and a gas pipeline.
| Aspect | Oil Pipelines | Gas Pipelines |
| Pipeline Material | Thicker walls to handle higher density and viscosity | Thinner walls due to lower density |
| Operating Pressure | Operates at lower pressure | Operates at much higher pressure |
| Flow Characteristics | Transport liquids –use pumps to maintain flow | Transport gasses – use compressors to maintain flow |
| Corrosion Risks | Prone to internal corrosion from impurities | Face external corrosion risks – less internal corrosion |
| Monitoring & Maintenance | Requires frequent cleaning and pigging (see the definition below) | Requires monitoring of pressure and temperature |
| Leak Detection | Leaks are more visible and easier to detect | Leaks can be harder to detect, pose explosion risks |
What are Some Key Terms in Underwater Pipelines?
- Subsea pipeline: installed on or beneath the seabed, used to transport oil, gas, or other substances from offshore facilities to onshore locations or between offshore platforms
- Flowline: type of subsea pipeline that carries oil or gas directly from the production well to a processing facility, or manifold on the seabed
- Riser: vertical pipeline that connects subsea pipelines to surface facilities, such as platforms or floating production units, allowing oil or gas to flow from the seabed to surface equipment
- Umbilical: bundle of cables and tubes that supply power, data, and chemicals to subsea equipment
- Pigging: process of cleaning, inspecting, or maintaining a pipeline by sending devices popularly referred to as “pigs” through the pipe to remove debris, or check for corrosion
- Manifold: structure on the seabed that connects multiple flowlines or risers, allowing for the distribution of oil or gas between various wells and pipelines
- Corrosion protection: techniques and materials used to prevent pipeline corrosion caused by exposure to seawater
- Hydrate formation: a process in which natural gas and water combine under high pressure and low temperature to form ice-like solids, which can block or damage subsea pipelines
- Pipeline integrity: overall health and safety of a pipeline system, ensuring it operates efficiently and without leaks or failures
- Trenching: process of digging a trench in the seabed to lay the pipeline, which helps protect it from physical damage, anchors, or fishing equipment
- Direct pipeline: a type of underwater pipeline that follows a straight route from an offshore platform to a single land-based facility or terminal
- Branched pipeline: pipeline system with multiple branches or segments, allowing oil or gas to be transported to different locations, platforms, or onshore facilities, offering flexibility in distribution
