Offshore drilling is a mechanical process where a wellbore is drilled below the seabed. It is typically carried out in order to explore for and subsequently extract petroleum that lies in rock formations beneath the seabed. Most commonly, the term is used to describe drilling activities on the continental shelf,. .
Around 1891, the first submerged oil wells were drilled from platforms built on piles in the fresh waters of the in . The wells were developed by small local. .
Notable offshore fields include:• the • the (offshore , , , and )• (in the and , part of the Ventura Basin) .
Offshore oil production involves environmental risks, most notably from oil tankers or pipelines transporting oil from the platform to onshore facilities, and from leaks and accidents on the platform (e.g. and .
• 17Apr2009 DC Appellate Decision stopping offshore Alaska Oil Leases.• .
Offshore drilling is usually done from platforms generically known as mobile offshore drilling units (MODU), which can be of one of several. .
Offshore oil and gas production is more challenging than land-based installations due to the remote and harsher environment. Much of the innovation in the offshore petroleum. .
• • • • • •
[pdf] 
Mobile offshore Drilling Units (MODU) This type of rig is commonly used in connection with oil and/or natural gas drilling. There are more jackup rigs in the worldwide offshore rig fleet than other type of mobile offshore drilling rig. Other types of offshore rigs include semi-submersibles (which float on pontoon-like. .
A jackup rig or a self-elevating unit is a type of mobile platform that consists of a buoyant fitted with a number of movable legs, capable of raising its hull over the surface of the sea. The buoyant hull enables. .
Jackup rigs are so named because they are self-elevating with three, four, six and even eight movable legs that can be extended (“jacked”) above or below the hull. Jackups are. .
A jackup rig is a barge fitted with long support legs that can be raised or lowered. The jackup is maneuvered (self-propelled or by towing) into. .
An early design was the DeLong platform, designed by Leon B. DeLong. In 1949 he started his own company, DeLong Engineering & Construction Company. In 1950 he constructed.
[pdf] 
Development and production operations in the Arctic offshore as a result of exploration have been limited, with the exception of the Barents and Norwegian seas. In Alaska, exploration subsequent to the discovery of the Prudhoe Bay oilfield has focussed on the onshore and shallow coastal waters.SummaryExploration for petroleum in the Arctic is expensive and challenging both technically and logistically. In the. .
There are 19 geological making up the region. Some of these basins have experienced and , most notably the where oil was first produced in 1968 from .. .
Drilling in the peaked during the 1970s and 1980s, led by such companies as in the Sverdrup Basin of the Arctic Islands, and by and in the Beaufort S. .
In June 2007, a group of returned from a six-week voyage on a , the expedition called . They had travelled to the , an underwate. .
In the years post 2000, sedimentary basins offshore were believed by some geologists to have high potential for large oil discoveries. In a comprehensive study of the potential of Arctic basins published in 2008, the.
[pdf]