Types of oil rigs

The Phases of Offshore Drilling

PHASE 1: EXPLORATION
A mobile drilling platform is sent to the site to obtain a core sample, which geologists analyse for signs of petroleum. The exploratory drilling rig will typically drill several temporary wells, each taking a few months to complete. A positive find (called "a show") is followed by more exploratory wells to verify the quality before taking next step: Drilling the much more elaborate production well.

PHASE 2: DRILLING BEGINS
A drill bit is attached to a "drill string" made of segments of drill pipe, each about nine meters long. The drill bit is lowered into the sea – sometimes to a depth of several kilometres – until it meets the seabed. The drill is rotated by a turntable at the platform floor, and as the drill grinds its way downwards (sometimes horizontally as well) extra lengths of drill pipe are attached.
For cooling, cleaning and stabilising pressure, a "drilling fluid" is pumped through the drill pipe and out through nozzles in the drill bit at high velocity. The fluid is usually a mixture of water, clay, barite and chemicals. Back at the platform, the fluid is recycled through a circulation system that disperses the crushed rock and reuses the fluid.

PHASE 3: FINALISING THE WELL
When the drill reaches target depth, production casing is lowered into the well and cemented into place. At the bottom, small explosive charges make small holes that allow the oil or gas to flow into the well while controlling pressure.
Once a well is "live", the drilling rig is typically replaced by a production platform, assembled at the site using a barge equipped with heavy lift cranes. An average well can last decades, so offshore production platforms are built with a long stay in mind.

Drilling Rig Types

The type of oil rig used in offshore drilling depends on the depth at the location, the type of oil, and prevailing conditions. The general categories include.

Drilling Barges
Jack Up Rigs
Submersible Rigs
Semi Submersible Rigs
Drill Ships

1. Drilling Barges

"Drilling barges are versatile and efficient platforms used for offshore drilling operations. These floating structures provide stability and mobility, making them suitable for various water depths and environments."

"Equipped with drilling equipment and facilities, drilling barges enable exploration and extraction of oil and gas reserves beneath the seabed. They play a crucial role in offshore production, particularly in areas where fixed platforms are not feasible."

"Drilling barges are often self-propelled, allowing them to move to different drilling locations quickly. This flexibility makes them ideal for exploratory drilling or projects that require frequent relocation."
"With their onboard accommodations, drilling barges can support a large crew and provide the necessary infrastructure for drilling operations, including living quarters, helipads, and storage facilities."

"Due to their mobility and adaptability, drilling barges have significantly contributed to the development of offshore oil and gas fields, expanding exploration possibilities and helping meet global energy demands."

2. Jack Up Rigs

"Jack-up rigs are specialized offshore drilling platforms designed to operate in shallow to medium water depths. These rigs feature extendable legs or 'jacks' that can be raised or lowered to secure the rig above the water surface."

"One of the key advantages of jack-up rigs is their ability to provide a stable drilling platform by elevating above the water using their retractable legs. This allows for safer and more efficient drilling operations."

"Jack-up rigs are commonly used for exploratory drilling, development drilling, and well intervention activities. They offer versatility in various environments, including coastal areas and offshore wind farms."

"These rigs typically have onboard accommodation facilities for the crew, helipads for transportation, and advanced drilling equipment to carry out drilling and completion operations."

"Due to their mobility, cost-effectiveness, and adaptability, jack-up rigs are widely utilized in the oil and gas industry for shallow water drilling projects, contributing significantly to offshore exploration and production."

3. Submersible Rig

"Submersible rigs are innovative offshore drilling platforms designed to be partially or fully submerged during drilling operations. These rigs are capable of submerging beneath the water surface, providing stability and protection against harsh weather conditions."

"Submersible rigs are particularly suited for deepwater drilling projects where traditional floating or fixed platforms may not be practical. They offer enhanced safety and operational efficiency in challenging offshore environments."

"These rigs are equipped with advanced technologies and systems that allow them to submerge to the desired depth and maintain stability during drilling. They often employ dynamic positioning systems to precisely control their position."

"Submersible rigs are capable of drilling in extreme water depths and are used for various operations, such as exploration, development drilling, and well intervention in deep-sea oil and gas fields."

"The use of submersible rigs has significantly expanded the frontiers of offshore drilling, enabling access to previously untapped reserves and pushing the boundaries of offshore exploration and production."

4. Semi-Submersible Rig

"Semi-submersible rigs are advanced offshore drilling platforms known for their exceptional stability and versatility. These rigs consist of floating structures with submerged pontoons or columns that provide buoyancy and stability during drilling operations."

"Semi-submersible rigs are particularly well-suited for deepwater drilling, as they can maintain position even in rough seas. Their ability to partially submerge allows them to withstand challenging weather conditions."

"Equipped with dynamic positioning systems, semi-submersible rigs can precisely control their position and maintain stability without the need for mooring. This enhances safety and efficiency in offshore drilling operations."

"These rigs are widely used for exploratory drilling, development drilling, and production activities in offshore oil and gas fields. Their spacious deck area can accommodate various drilling equipment and support facilities."

"The flexibility and adaptability of semi-submersible rigs make them essential assets in the offshore industry, enabling access to deepwater reserves and contributing to the global energy supply."

5. Drill Ship

"Drill ships are specialized vessels equipped with drilling equipment and facilities, designed for offshore exploration and production activities. These ships are capable of drilling in deepwater and ultra-deepwater areas, reaching oil and gas reserves beneath the seabed."

"Unlike other types of drilling platforms, drill ships are mobile and self-propelled, allowing them to move between drilling locations efficiently. This mobility makes them versatile and well-suited for exploratory drilling projects."

"Drill ships are equipped with dynamic positioning systems that enable precise control of their position, ensuring stable drilling operations even in challenging offshore environments."

"These vessels typically have a large deck area for housing drilling equipment, storage, and accommodation facilities for the crew. They may also have helipads for crew transportation and supply replenishment."

"Drill ships play a crucial role in offshore oil and gas exploration, allowing access to deepwater reserves and contributing to the development of new energy resources."

7. Spar Platform

"Spar platforms are unique offshore structures designed for deepwater drilling and production operations. These platforms consist of a cylindrical hull that extends below the water surface, providing stability and buoyancy."

"Spar platforms are moored to the seabed using a combination of vertical tethers and mooring lines, allowing them to remain in position despite ocean currents and waves."

"Due to their streamlined shape and deep draft, spar platforms are highly resistant to the effects of extreme weather conditions, making them suitable for offshore locations prone to hurricanes or storms."

"These platforms typically house drilling equipment, production facilities, and accommodations for the crew. They are particularly well-suited for deepwater oil and gas fields, where traditional fixed platforms may not be feasible."

"Spar platforms have played a significant role in advancing offshore drilling technology, enabling exploration and production in deeper waters and contributing to the development of offshore energy resources."