What You Need To Know About Offshore Oil And Gas Operations

Posted on Dec 30, 2023 at 05:12 PM

The world's oceans and seas hold the most incredible oil and natural gas reserves. But offshore oil and gas operations require innovation, ingenuity, and dedication to execution, exploration, extraction, and use of those resources in the best occupational and environmental safety ways.

You will find everything about offshore oil and gas operations in this article. So, read on for more information.

What are offshore oil and gas operations? 

The oil or gas that we use in all aspects of our lives today and that is extracted from offshore fields goes through a set of processes to reach what it is. However, it is only possible to grasp it practically by attending Oil and Gas Training. But here we will share with you the broad outlines of the oil and gas chain of operations:

• Research and exploration phase

In general, the first phase in offshore oil and gas operations, as well as onshore, is to search and explore the whereabouts of oil reserves. This must be done before starting the extraction phase from those reservoirs.

Exploration companies conduct scientific surveys for potential fields using geology and remote sensing. These sensors work by bouncing sound waves off the seafloor.

These sensors sense and record the returning sound wavelengths during the scanning process. Based on studying these waves, the existence of the well is discovered. Strict safety measures are used throughout this type of offshore oil and gas operation. The goal is to ensure the protection of the ecosystem and the health of marine animals and creatures.

• Drilling and Extraction phase

Once a prospective reserve is found, oil and gas companies will phase out the reservoir from the wells using Mobile Offshore Drilling Units (MODUs). MODUs may become offshore production platforms in the future. The oil company will usually replace the MODU with a more permanent oil production rig to capture the oil.

MODU's job is to drill down into the ocean floor to find oil and natural gas reserves. The part extending below the bottom surface is called the drill. It is drilling rocks to explore for oil. The part that penetrates the water is called the riser. The riser allows drilling fluids to move between the floor and the drilling rig.

The well is closed to prepare for a production rig when the stock is reached. To accomplish this, the operating engineers use a pair of plugs to seal the wellbore. The bottom plug sits near the oil deposit and is clamped by the drilling mud. Engineers use an overhead plug at the top of the wellhead to cap it. Then, the well is ready for a production rig to take over.

One of the occupational safety requirements that must be applied during offshore oil and gas operations is the placement of a blowout preventer (BOP) at the drilling surface to prevent the risk of explosion. This preventer closes off the pipe between the rig and the unit via hydraulic clamps.

Engineers use metal casings to add stability to the well. These casings help keep the well from collapsing in on itself. Each casing is lined with cement walls. The casings get narrower as the well gets more profound. Engineers use a liner hanger O-ring to seal the two sections (the broader and narrower casing) together.

There are 4 main types of MODUs:

1. Submersible or Barge 

It usually consists of a drilling rig resting on the seafloor at 9.1 to 10.7 meters. On the barge's deck are steel columns that extend above the waterline. A drilling platform rests on top of these shafts. These rigs are usually used in areas with calm waters.

2. Jackup 

It is a rig that sits on top of a floating barge. A ship tows the barge to the drilling site. Once positioned, the jackup can extend its legs to the sea floor. The legs are loaded in such a way that they don't penetrate the floor.

Once each leg is secured, the backup ratchets the legs so the platform rises above the water level. This keeps the rig safe from tidal motions and waves. This type of drilling rig can be used at depths of up to 160 meters.

3. Drill ships 

They are offshore ships that have a drilling rig on the top deck. The drill operates through a hole in the undercarriage. Anchors and propellers support the ships to correct for drift while working. These ships can operate in deep water conditions.

4. Semisubmersibles 

These rigs float on top of massive ships that are submerged pontoons. Some have propulsion systems that allow them to navigate to drilling sites. At the same time, the other type needs a boat to tow them to the site.

Most use several anchors that help maintain the structure's orientation. Computers control the tension on each anchor chain to correct for drift. Some can convert to production rigs, reducing the need for a second rig to take its place once oil is found. In other words, it is saving in petroleum economies.

• Production phase

Once a well is ready for production, offshore oil and gas operations turn to investment. The oil industry has developed massive engineering marvels that drill at high temperatures and pressures in ultra-deep water. There is a production platform to match every type of marine environment. 

The production rig can only be responsible for one well. It could also be accountable for multiple wells interconnected by a manifold system and pipelines from a remote field. 

Below, we will highlight the most common production rigs for offshore oil and gas operations:

1. Fixed Platform (FP) 

It consists of a long vertical section of extended steel members supported by piles driven into the seabed, with an expansive deck placed on top, providing sufficient space for the drilling rig, production equipment, and crew quarters. The fixed platform is economical and suitable for wells with a depth of 1,500 feet.

2. Compliant Tower (CT) 

It consists of a narrow, flexible tower and a piled foundation that can support the upper deck. Unlike a fixed platform, the compliant tower withstands large lateral forces by sustaining significant lateral deflections, suitable for water depths between 1,000 and 2,000 feet.

3. Tension Leg Platform (TLP)

It is a floating structure held by vertical, tensioned tendons connected to the ocean floor. Tensioned tendons provide the use of this platform with limited vertical movement. The TLP is suitable for water depths close to 4,000 feet.

4. Mini-Tension Leg Platform (Mini-TLP) 

It is similar to the previous platform. It was developed to produce small reserves for which it may not be feasible to use the last platform. It can also be used as a utility or production platform for early discoveries. The world's first Mini-TLP was installed in 1998 in the Gulf of Mexico.

5. SPAR Platform (SPAR) 

It consists of a single large-diameter vertical cylinder supporting the deck. It has a typical topside platform comprising (drilling and production equipment), and three types of risers (production, drilling, and export). The platform hull is moored using a cohesive system of 6 to 20 lines anchored into the sea floor.

SPARs are presently used in water depths up to 3,000 feet. And in some advanced species, it reaches depths of 7,500 feet.

6. Floating Production System (FPS) 

It consists of a semi-submersible platform. It is anchored in place with chains and wire ropes. Oil and gas extracted from wells are transported via production risers designed to accommodate platform motion. The FPS can be used in ultra-deep water.

7. Floating Production, Storage & Offloading System (FPSO) 

It consists of a large tanker moored to the ocean floor. The FPSO is designed to process and store production from wells periodically and offload it onto a smaller shuttle tanker. This small tanker transports it to onshore stations for processing.

An FPSO may be suited for marginal economic fields located in remote deepwater areas where a pipeline infrastructure does not exist.

What PIPELINES are used in offshore oil and gas operations?

Offshore pipelines (oil and gas pipelines) are a key part of offshore oil and gas operations. These pipelines transport oil and gas from subsea wells to a production platform and then to nearby shores for processing and distribution.

Offshore Pipelines are classified into three categories:

1. Offshore Pipelines. 

They are often called flowlines or feeder lines. These pipelines transport oil reserves consisting of oil, gas, and water from the wells to the manifold or platform directly. Some pipes may return treated water from the production platform to the injection well for disposal.

2. Export Pipelines 

These pipelines transport processed oil or gas from the platform to offshore processing facilities. These pipelines are classified into multi-phase pipelines that carry a mixture of gas and oil. The last tube has a single-phase pipeline and is the one that transports either only oil or only gas.

3. Transmission pipelines 

They are the pipelines responsible for transporting and distributing oil and gas from one coast to another for trading purposes, in the same way an oil tanker is hauled.

In Conclusion,

Offshore oil and gas operations are incredible engineering marvels that would not have been possible without human hands. Therefore, oil and gas companies must look for the most skilled engineers, technicians, workers, and divers who can adapt to all weather and operational conditions. To perform their tasks efficiently after obtaining the necessary oil and gas training.