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What is offshore drilling?

Offshore drilling refers to a mechanical processwhere a wellbore is drilled through the seabed.

It is typically carried out in order to explore forand subsequently extract petroleum which liesin rock formations beneath the seabed

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History

Around 1891, the first submerged oil wells were drilledfrom platforms built on piles in the fresh waters of theGrand Lake St. Marys (a.k.a. Mercer County Reservoir)in Ohio. The wells were developed by small local

companies such as Bryson, Riley Oil, German-Americanand Banker's Oil.

Around 1896, the first submerged oil wells in salt waterwere drilled in the portion of the Summerland field

extending under the Santa Barbara Channel inCalifornia. The wells were drilled from piers extendingfrom land out into the channel.

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Types

Fixed platforms

A fixed platform consists of a welded tubularsteel jacket, deck, and surface facility. The

jacket and deck make up the foundation for

the surface facilities.

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Fixed platforms

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Fixed platforms

Surface facilities (also known as topsides) are the partof the platform that contains the drilling, production,and crew quarter modules.

The size of each module is dictated by the volume offluid to be handled, the number of personnel neededto operate the facility and operations, and thepotential expansion needed to accommodate futureproduction from other fields.

Combined, the topsides dimensions could be 200 feetby 200 feet per deck level, with four decks, resulting inan overall height of 100 feet

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Fixed platforms

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Compliant towers

Compliant towers are similar to fixed platforms in that they have a

steel tubular jacket that is used to support the surface facilities.

Unlike fixed platforms, compliant towers yield to the water and

wind movements in a manner similar to floating structures.

Like fixed platforms, they are secured to the seafloor with piles.

The jacket of a compliant tower has smaller dimensions than those

of a fixed platform and may consist of two or more sections.

It can also have buoyant sections in the upper jacket with mooring

lines from jacket to seafloor (guyed-tower designs) or acombination of the two.

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Compliant towers

The water depth at the intended location dictatesplatform height.

Once the lower jacket is secured to the seafloor, it actsas a base (compliant tower) for the upper jacket andsurface facilities.

Large barge-mounted cranes position and secure thejacket and install the surface facility modules.

These differences allow the use of compliant towers inwater depths ranging up to 3,000 ft.

This range is generally considered to be beyond theeconomic limit for fixed jacket-type platforms.

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Compliant towers