Offshore Oil rigs and platforms provide the equipment and infrastructure needed to drill wells and produce oil and gas beneath the seabed. However, their designs and functions vary considerably.
The main offshore drilling units are jack-up rigs, semi-submersible rigs, and drillships. Offshore production facilities include fixed platforms, compliant towers, tension-leg platforms, spars, production semi-submersibles and floating production, storage and offloading vessels (FPSOs).
Understanding these differences is useful whether you are exploring offshore careers or recruiting people for an energy project. Each asset requires a different combination of drilling, engineering, production, maintenance, and marine expertise.
What is the difference between an oil rig and an offshore platform?
An oil rig contains the equipment used to drill wells. An offshore platform is a structure that supports activities such as drilling, production, processing, and accommodation.
The terms sometimes overlap. A production platform may have drilling equipment installed, while a mobile drilling unit can move between locations to construct wells.
An FPSO, meanwhile, primarily handles production, storage and offloading. It should not be confused with a drillship simply because both have ship-shaped hulls.
What are the main types of offshore rigs and platforms?
| Type | Main purpose | Key design feature |
| Jack-up rig | Offshore drilling | Legs rest on the seabed and raise the hull above the water |
| Semi-submersible drilling rig | Offshore drilling | Floating unit supported by submerged pontoons and columns |
| Drillship | Offshore drilling, including deepwater operations | Vessel equipped with drilling and station-keeping systems |
| Fixed platform | Long-term offshore operations | Structure supported directly by the seabed |
| Compliant tower | Offshore production | Slender tower designed to flex under environmental forces |
| Tension-leg platform | Offshore production | Floating hull restrained by tensioned tendons |
| Spar platform | Offshore production | Deep-draft floating hull secured by moorings |
| Production semi-submersible | Offshore processing and production | Semi-submersible hull carrying production equipment |
| FPSO | Production, storage and offloading | Floating vessel that processes production and stores oil |
The right design depends on the field and operating environment. Water depth matters, but so do seabed conditions, weather, reservoir requirements and available export infrastructure.
1. What is a jack-up rig?
A jack-up rig is a mobile drilling unit that lowers its legs onto the seabed and raises its hull above the sea surface.
During relocation, the hull floats. At the drilling location, the legs provide support while the elevated hull carries the drilling equipment and accommodation.
Jack-ups are associated with shallower-water operations, but their operating limits vary. Suitability for a location depends on the individual unit, seabed conditions, and environmental loads.
For jobseekers, relevant positions may involve drilling operations, mechanical maintenance, electrical systems, lifting activities, and safety support.
2. What is a semi-submersible rig?
A semi-submersible rig is a floating drilling unit with submerged pontoons connected to an upper deck by columns.
Much of its buoyant structure sits below the surface, helping reduce wave-related movement. The unit remains afloat during operations and uses an appropriate station-keeping system.
“Semi-submersible” describes the design, rather than one specific function. Some units carry drilling equipment; others are configured for production.
When reviewing a vacancy, check whether the employer needs drilling, production, marine or maintenance experience. Experience aboard one semi-submersible does not automatically cover every role on another.
3. What is a drillship?
A drillship is a vessel fitted with equipment to drill offshore wells. Many drillships are designed for deepwater operations.
Its ship-shaped hull supports mobility between drilling locations. During operations, it maintains position using systems appropriate to its design, which may include thrusters, moorings or a combination.
Dynamic positioning uses controlled thrust to maintain the vessel’s position. This makes marine systems and station-keeping expertise important alongside drilling competence.
Drillship roles can span drilling crews, marine operations, engineering, electrical maintenance and subsea equipment support.
4. What is a fixed offshore platform?
A fixed platform is supported by a structure founded on the seabed. It provides a base for long-term offshore operations.
Depending on the development, it may carry production equipment, drilling facilities, utilities and accommodation.
Unlike a mobile drilling unit, a fixed platform is designed around its installed location. Its operating needs can include process operations, inspection, maintenance and engineering support throughout the facility’s life.
5. What is a compliant tower?
A compliant tower is a seabed-connected structure designed to flex in response to waves and other environmental forces.
It supports facilities above the water while allowing controlled movement. Although it moves by design, it is not a freely floating installation.
This illustrates why offshore structures cannot be classified simply as “rigs that move” and “platforms that stay still”. Their support systems and intended functions matter.
6. What is a tension-leg platform?
A tension-leg platform, or TLP, is a floating production facility held down by tensioned tendons connected to the seabed.
The tendons restrain movement, particularly vertical motion. The platform’s buoyancy and tendon system work together to support its operating arrangement.
Jobs associated with these facilities may involve production systems, mechanical and electrical maintenance, structural integrity and specialist inspection.
7. What is a spar platform?
A spar platform uses a deep-draft floating hull to support offshore production facilities. Moorings hold it at its operating location.
Much of the hull extends beneath the surface. This distinguishes a spar from a ship-shaped production vessel and from the pontoon-and-column arrangement of a semi-submersible.
Fixed platforms, compliant towers, TLPs and spars represent different engineering approaches to offshore development.
8. What is a production semi-submersible?
A production semi-submersible uses a floating pontoon-and-column structure to carry equipment that handles fluids from producing wells.
Its hull concept resembles that of a semi-submersible drilling unit, but its equipment and operating purpose differ.
For recruitment, this distinction is essential. Production operations experience and drilling operations experience involve different responsibilities, even when the underlying asset design appears similar.
9. What is an FPSO?
FPSO stands for Floating Production, Storage and Offloading. It receives fluids from producing wells, processes them, stores oil and transfers it to export tankers.
An FPSO combines process equipment with marine systems. Gas handling arrangements depend on the project; the acronym does not mean that every FPSO stores both oil and gas.
Potential roles include production operations, instrumentation, mechanical maintenance, marine operations and cargo-related responsibilities.
How do subsea wells connect to offshore platforms?
Subsea wells can connect to a production facility through flowlines on the seabed and risers that carry fluids towards the surface.
This means a platform does not need to sit directly above every well it serves. A development may connect several subsea wells to one production host.
Drilling and production are also separate stages. A drilling unit may finish its work and move away, while the production facility remains to operate the field.
How do offshore opportunities differ by location?
The location of an assignment affects travel arrangements, employment requirements and the operating environment. However, the asset type and job responsibilities remain essential when assessing suitability.
United States: Houston and the Gulf Coast
A Houston-based vacancy may involve office support, offshore deployment or a combination. Candidates should confirm the offshore installation, mobilisation point and expected travel.
BOEM’s records show a variety of permanent deepwater structures in the US Gulf region, highlighting why “offshore experience” alone can be too broad a description.
United Kingdom and the North Sea
For a North Sea assignment, establish whether the position supports a drilling campaign, an operating production facility or another project stage.
Describe your equipment experience and responsibilities clearly. Employers need to understand what you worked on and what you were qualified to do.
Guyana
Guyana offers an example of FPSO-based development. ExxonMobil’s August 2025 Yellowtail announcement identifies the ONE GUYANA FPSO as the project’s production vessel.
Candidates should distinguish between roles aboard production vessels, assignments on drilling units and shore-based support positions.
What jobs are available on offshore rigs and platforms?
Offshore jobs cover drilling, production, engineering, maintenance, marine operations and support services. Availability depends on the asset and project stage.
Examples include:
- Drilling crew roles, such as floorhand, derrickhand and driller.
- Mechanical, electrical and instrumentation technicians.
- Production and process operators.
- Marine and deck personnel.
- Crane operators and materials coordinators.
- Subsea specialists.
- Health and safety professionals.
- Medical, catering and accommodation support.
Some junior roles still require relevant qualifications or experience. Offshore safety training supports readiness for an assignment but does not replace technical competence.
What should you check before accepting an offshore job?
Before accepting an assignment, confirm:
- Asset and duties: Which facility will you work on, and what will you do?
- Required competence: What qualifications and equipment experience are needed?
- Safety and medical requirements: Which certificates and assessments are accepted?
- Rotation: How are working periods, leave and travel scheduled?
- Pay: Which days are paid, and what allowances or benefits apply?
- Travel arrangements: Who organises mobilisation and covers expenses?
Training requirements vary by role and location. Check the accepted course version before booking offshore safety training such as BOSIET.
Explore offshore opportunities with WRS
Worldwide Recruitment Solutions (WRS) connects candidates and employers across oil and gas, offshore and maritime disciplines. Whether you are exploring your next assignment or recruiting for a project, our team can help you discuss your requirements.
Explore oil and gas opportunities with WRS or contact our team about your hiring needs.
Frequently asked questions
Do all offshore platforms float?
No. Fixed platforms and compliant towers are supported by structures connected to the seabed. Spars, TLPs and production semi-submersibles are floating systems.
Is an FPSO the same as a drillship?
No. An FPSO primarily processes, stores and offloads production. A drillship is equipped with drill wells.
Can a semi-submersible produce oil and gas?
Yes. A semi-submersible can operate as a production facility when designed and equipped for that purpose. Other units are configured for drilling.
Which offshore platform type is best?
There is no universal design. Selection depends on the field, water depth, seabed, weather, production requirements, and project economics.
How much do offshore workers earn?
Pay depends on occupation, experience, location and contract terms. Compare the rate, paid days, allowances and benefits of individual offers.
Do all offshore jobs follow the same rotation?
No. Rotations vary by employer, asset, and assignment. Confirm the schedule and treatment of travel days before accepting a role.
About the Author
Apurva Agrawal is an SEO Specialist at Worldwide Recruitment Solutions (WRS), with three years of experience driving digital growth and visibility within the global recruitment sector.
This guide was developed in collaboration with and verified by Melissa Walsh, Marketing and Brand Manager at WRS, ensuring all workforce data and service methodologies reflect WRS’s global standards and positioning.
