How do offshore oil rigs work

Tension Leg Platform TLP consists of a floating structure held in place by vertical, tensioned tendons connected to the sea floor by pile-secured templates. Tensioned tendons provide for the use of a TLP in a broad water depth range with limited vertical motion. The larger TLP's have been successfully deployed in water depths approaching 4, feet. Mini-Tension Leg Platform Mini-TLP is a floating mini-tension leg platform of relatively low cost developed for production of smaller deepwater reserves which would be uneconomic to produce using more conventional deepwater production systems.

It can also be used as a utility, satellite, or early production platform for larger deepwater discoveries. It has a typical fixed platform topside surface deck with drilling and production equipment , three types of risers production, drilling, and export , and a hull which is moored using a taut caternary system of six to twenty lines anchored into the seafloor. SPAR's are presently used in water depths up to 3, feet, although existing technology can extend its use to water depths as great as 7, feet.

Floating Production System FPS consists of a semi-submersible unit which is equipped with drilling and production equipment. It is anchored in place with wire rope and chain, or can be dynamically positioned using rotating thrusters. Production from subsea wells is transported to the surface deck through production risers designed to accommodate platform motion. The FPS can be used in ultra deep water. Subsea System SS ranges from single subsea wells producing to a nearby platform, FPS, or TLP to multiple wells producing through a manifold and pipeline system to a distant production facility.

These systems are presently used in water depths greater than 5, feet. An FPSO is designed to process and stow production from nearby subsea wells and to periodically offload the stored oil to a smaller shuttle tanker. The shuttle tanker then transports the oil to an onshore facility for further processing.

An FPSO may be suited for marginally economic fields located in remote deepwater areas where a pipeline infrastructure does not exist. Pipelines are classified in three categories: Infield Pipelines transport fluids within the field.

They are often called flowlines or feeder lines. Infield Pipelines carry a mixture of oil, gas and water from the subsea wells to a manifold or directly from the well to the process platform. A smaller number of infield lines carry processed water from the platform to injection wells for disposal.

Export Pipelines transport processed oil or gas from the platform to the coast. If the pipeline carries a mixture of oil and gas then it is a multi-phase pipeline. Some offshore rigs are anchored to the bottom of the ocean while others use dynamic positioning to stay in place. Dynamic positioning uses very high tech computer algorithms to control thrusters that keep the vessel on location.

The vessel's navigation, power and control systems are all integrated, helping the vessel stay stationary in changing weather conditions. Workers generally work 12 hours on and 12 hours off for weeks while on board, then take weeks off shore-side. The journey is usually via helicopter. These trips back and forth have created an entire industry of helicopter companies with hundreds of choppers travelling to and from offshore rigs.

At least helicopters take off each day on trips to the platforms in the North Sea. Although people are transported via helicopter, supplies are transported via supply vessels that run to the platforms and back to shore. The oil from the rigs is usually transported to shore via an undersea pipeline.

With hundreds of rigs offshore and all the air, water, and undersea travel, you can imagine that Aberdeen is a busy place! On the rigs, there are four main categories of jobs: production, maintenance, and service. Production workers are involved with the production of oil directly, while maintenance workers upkeep the platforms. Service handles the care of the workers such as cooking, cleaning, or medical service for the rest of the crew.

Anyone working on the rig in an offshore capacity typically makes more than an onshore worker. Therefore, as many people as possible work onshore communicating with the workers on the rig who are mostly operational. How big are these rigs? In photos, oil rigs appear to be a small platform, or maybe even a large building. If you are able to see a rig in person from the shore, it probably looks like a tiny speck on the horizon.

Extraction, transportation, and environmental protection are all comparatively more difficult with offshore drilling than with traditional wells. In an attempt to make this process more simple, petroleum companies have developed offshore oil platforms to aid in this extraction. Once the offshore drilling platform is built, some method of extracting the oil and gas from beneath the ocean and moving it to the surface without losing it must be developed.

To drill without water flowing into the hole or having all the oil surge up into the ocean, a subsea drilling template is used. This template is simply a large metal box with holes in it that is used to guide the drilling process and marks the site of each production well. Once the locations of the drilling sites are marked with this template, the drilling process can begin. To drill these wells, a number of 9 meter drill pipes are connected to form a large drill string used to reach deep into the Earth's crust.

This drilling process can take a long period of time, lasting anywhere from weeks to months. As the borehole moves deeper into the ground, a stream of drilling mud is sent to the drill bit, and then moves back up to the platform. This mud is vitally important to the drilling process as it provides lubrication for the drill bit, seals the wall of the well, and controls pressure inside of the well.

Any rock particulates broken off during the drilling process are brought up to the surface, suspended in the drilling mud. Subsea systems are typically in use at depths of 7, feet meters or more, and do not have the ability to drill, only to extract and transport. A Spar Platform SP is the largest offshore platforms in use. These huge platforms consist of a large cylinder supporting a typical fixed rig platform.

The cylinder does not extend all the way to the seafloor, but instead is tethered to the bottom by a series of cables and lines. The large cylinder serves to stabilize the platform in the water, and allows for movement to absorb the force of potential hurricanes.

The first Spar platform in the Gulf of Mexico was installed in September of Its cylinder measured feet meters long and was 70 feet 20 meters in diameter. Subscribe to Email Updates.