Subsea Engineering

Subsea Design Architecture

Subsea engineering layout from FNG Energy

Subsea engineering is a complex engineering feat of extracting oil and gas from the depths of the seabed onto processing plants in order to produce the energy and chemicals that we need to our daily usage. This is nicely depicted in the image above, showing all the components required to make this work.

This site attempts to explain, to the best of my ability, how this engineering is accomplished.

Subsea Architecture/ Layout

When you begin a new project, you would typically only know the rough positions of a few components. This is normal. Every project starts with a few key locations, typically the well locations, the topside and maybe the location at land where the pipeline has to land to get to the onshore processing plant. Throughout the design process, the layout becomes more firm.

A subsea architecture or subsea layout refers to the design and arrangement of various components and systems that make up a subsea infrastructure. This is a comprehensive plan that outlines the organization of subsea structures, equipment, pipelines, and control systems that are required to transport oil and gas from subsea reservoirs to onshore or offshore processing facilities.

The main idea behind creating a subsea architecture is to optimise the flow of hydrocarbons (oil and/or gas) and ensure the efficient and safe operation of the subsea infrastructure.

Here are some key components in most subsea architectures:


A subsea wellhead is placed at the point in the seabed where oil/gas is to be extracted out. The wellhead is enclosed in a pressure sealed well casing.

Subsea trees

Subsea trees, also called as Christmas trees because of its resemblance, are the primary flow control devices installed on top of the wellhead to control the flow of oil or gas. The trees may be vertical or horizontal, depending on the project requirements.


Manifolds are typically rectangular structures (imagine a coffin box) which have many valves (depending on the number of trees connecting to it) and internal piping. The purpose of a manifold is to collect and distribute hydrocarbons from multiple wells to the main pipeline. Manifolds are also used to distribute injection fluids (water or gas) to maintain reservoir pressure.

Subsea pipelines and flowlines

The pipelines and flowlines are the work horse of the subsea field as they carry the hydrocarbons from the subsea manifolds to processing facilities. Flowlines connect individual wells to manifolds or directly to the main pipeline, while larger pipelines transport the fluids over long distances. 

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Risers connect the subsea pipelines to surface facilities (such as platforms or floating production systems (FPSO)) and carry the hydrocarbons upward. Risers are like pipelines except they are in the vertical direction.


All those subsea equipment way down on the seabed requires power and data cables. This is where umbilicals come in. Umbilicals are long, flexible cables that supply power, control signals, and chemicals to subsea equipment. They can also carry hydraulic fluids for the operation of various devices, like subsea trees and valves.

Control systems

Control systems are responsible for monitoring, controlling, and managing the subsea infrastructure. They include subsea control modules, distribution units, and communication systems that enable operators to remotely monitor and control the subsea facilities.

Designing a subsea architecture requires one to take into account a lot of factors, such as project requirements, reservoir characteristics, environmental conditions (both subsea and onshore), geography, political situations, and available technology.

The ultimate goal is to create an efficient, safe, and cost-effective infrastructure that ensures the optimal production and transportation of hydrocarbons from subsea reservoirs.


Subsea Pipelines

Basic Subsea Pipeline Design

What does subsea pipeline design entail?

Fractured Component

Fracture Mechanics

What is fracture mechanics for subsea pipelines?