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Selected
List of Specialized Words and their Definitions:
bottom-supported offshore drilling rig
a type of
mobile offshore drilling unit that has a part of its structure in contact
with the seafloor when it is on site and drilling a well. The remainder of
the rig is supported above the water. The rig can float, however, allowing
it to be moved from one drill site to another. Bottom-supported units
include submersible rigs and jackup rigs.
caisson
1. one of
several columns made of steel or concrete, which serves as the foundation
for a rigid offshore platform rig. 2. a steel or concrete chamber that
surrounds equipment below the waterline of an arctic submersible rig,
thereby protecting the equipment from damage by moving ice.
caisson-type
platform rig
a rigid
offshore drilling platform that stands on steel caissons and is used to
drill development wells. The caissons are firmly affixed to the seafloor,
and the drilling and production decks are laid on top of them. The
platform is used in certain arctic waters, where the caissons are needed
to protect equipment from moving ice.
derrick
a large
load-bearing structure, usually of bolted construction. In drilling, the
standard derrick has four legs standing at the corners of the substructure
and reaching to the crown block. The substructure is an assembly of heavy
beams used to elevate the derrick and provide space to install blowout
preventers, casingheads, and so forth. Because the standard derrick must
be assembled piece by piece, it has largely been replaced by the mast,
which can be lowered and raised without disassembly.
drill ship
a
self-propelled floating offshore drilling unit that is a ship constructed
to permit a well to be drilled from it. While not as stable as
Semisubmersible, drill ships are capable of drilling exploratory wells in
deep, remote waters.
drilling
block
a lease or a
number of leases of adjoining tracts of land that constitute a unit of
acreage sufficient to justify the expense of drilling a wildcat.
floating
offshore drilling rig
a type of
mobile offshore drilling unit that floats and is not secured to the
seafloor (except for anchors). Floating units include inland barge rigs,
drill ships and ship-shaped barges, and semisubmersibles.
jackup
drilling rig
a mobile
bottom-supported offshore drilling structure with columnar or open-truss
legs that support the deck and hull. When positioned over the drilling
site, the bottoms of the legs rest on the seafloor. A jackup rig is towed
or propelled to a location with its legs up. Once the legs are firmly
positioned on the bottom, the deck and hull height are adjusted and
leveled. Also called self-elevating drilling unit.
mast
a portable
derrick that is capable of being erected as a unit, as distinguished from
a standard derrick that cannot be raised to a working position as a unit.
For transporting by land, the mast can be divided into two or more
sections to avoid excessive length extending from truck beds on the
highway.
mobile offshore drilling unit
a drilling
rig that is used exclusively to drill offshore exploration and development
wells and that floats upon the surface of the water when being moved from
one drill site to another. It may or may not float once drilling begins. Two basic types of mobile offshore drilling units are used to drill most
offshore wildcat wells: bottom-supported drilling rigs and floating
drilling rigs.
notices to lessees and operators (NTL’s)
formal
routine documents that provide clarification, description, or
interpretation of a regulation or OCS standard; provide guidelines on the
implementation of a special lease stipulation or regional requirement;
provide a better understanding of the scope and meaning of a regulation by
explaining MMS interpretation of a requirement; or transmit administrative
information such as current telephone listings and a change in MMS
personnel or office address.
platform rig
an immobile
offshore structure from which development wells are drilled and produced. Platform rigs may be built of steel or concrete and may be either rigid or
compliant. Rigid platform rig, which rest on the seafloor, are the
caisson-type platform, the concrete gravity platform, and the steel-jacket
platform. Compliant platform rigs, which are used in deeper waters and
yield to water and wind movement are the guyed tower platform and the
tension-leg platform.
production
rig
a portable
servicing or workover outfit, usually mounted on wheels and
self-propelled. A well servicing unit consists of a hoist and engine
mounted on a wheeled chassis with a self-erecting mast. A workover rig is
basically the same, with the addition of a substructure with rotary, pump,
pits, and auxiliaries to permit handling and working a drill string.
rig
the derrick
or mast, drawworks, and attendant surface equipment of a drilling or
workover unit.
semisubmersible drilling rig
a floating
offshore drilling unit that has pontoons and columns that when flooded
cause the unit to submerge in the water to a predetermined depth. Living
quarters, storage space, and so forth, are reassembled on the deck. Semisubmersible rigs are either self-propelled or towed to a drilling site
and either anchored or dynamically positioned over the site, or both. In
shallow water, some semisubmersibles can be ballasted to rest on the
seabed. Semisubmersibles are more stable than drill ships and ship-shaped
barges and are used extensively to drill wildcat wells in rough waters
such as the North Sea. Two types of semisubmersible rigs are the
bottle-type semisubmersible and the column-stabilized semisubmersible.
wildcat
1. a well
drilled in an area where no oil or gas production exists. 2. (nautical)
the geared sheave of a windlass used to pull anchor chain.
An extensive
List of Specialized Words and Their Definitions can be found at
www.mms.gov/glossary/index.htm.
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Last Updated:
08/17/2007,
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