REAL-690 Lecture Notes - Lecture 2: United States Offshore Drilling Debate, Offshore Drilling, Drill String
16 Dec 2016
School
Department
Course
Professor
Offshore Drilling Basics
Diamond Offshore provides offshore contract drilling services to the energy industry around the
globe and is a leader in deepwater drilling.
Our customers are the world's oil companies ("operators"), and our sole job is to drill and complete* wells
at the direction of our customers (*completion in industry terms means preparing the well for production.
This entails running production casing, stimulation work, and zonal isolation to allow the well to flow
hydrocarbons). Because we work offshore, often in remote locations, each of our drilling rigs is largely
self-sufficient. When contracted, they come with a full crew and the equipment and supplies needed to
carry out the assigned task, be it one short well or multiple years of work. For assignments in the US Gulf of
Mexico, crews typically work a rotational schedule consisting of 21 consecutive days aboard the rig followed by 21
days off. In international locations, our crews typically work a rotational schedule of 28 days on and 28 days off.
In a broad sense, operators drill two basic types of wells-exploratory (to find new oil or gas deposits) and
development (to prepare the discovery for production). Water depths range from 20 to 400 feet for jack-up
rigs to up to 12,000 feet for semisubmersibles and drillships.
Before drilling an exploratory well, an operator will conduct geologic surveys of an area to determine the
potential for oil or gas deposits and to identify specific targets. The operator then hires a drilling contractor
like Diamond Offshore to drill exploratory ("wildcat") wells offshore. The oil company chooses the location
and supervises the operation, which may take as little as 15 days or as long as 12 months, of round-the-
clock, seven-days-per-week operation to drill a single well depending on the complexity of the project.
Offshore rigs are designed for efficiency in living and working, with emphasis on keeping the rig steady in
gulf or ocean waters. See rig basics.
Offshore wells are drilled in much the same way as their onshore counterparts-with several allowances for
the offshore environment. A conduit made from lengths of steel pipe permits drilling fluids to move
between the rig-at the water's surface-and the sea floor. This conduit is called a "riser." The riser is fitted
with ball-and-slip joints that permit the long string of riser pipe to move up and down and bend slightly
with the wave-induced movement of the rig.
The well is drilled using a length of slender steel pipes and other tools that, connected, comprise a "drill
string." At the bottom of the string of pipes is a hole-boring device called a "drill bit." Heavy sections of
pipe, called "drill collars," add weight and stability to the drill bit. Each ordinary pipe in the string is about
30 feet long and weighs about 600 pounds; drill collars can weigh 4,000 Pounds or moreper 30-foot
length.
As drilling proceeds, and the well gets deeper, the drilling crew adds new sections of drill pipe to the ever-
lengthening drill string. Hydraulic devices keep constant tension on the drill string to prevent the motion of
the rig and riser from being transmitted to the drill bit.
The drill string is lowered through the riser to the sea floor, passing through a system of safety valves
called a "blowout preventer" (BOP, pronounced "B.O.P."). This stack of multiple safety valves is designed
find more resources at oneclass.com
find more resources at oneclass.com
to contain any natural pressures that the drillers might encounter beneath the Earth's surface. Its purpose
is to prevent a possible "blowout"-an uncontrolled eruption of oil, gas or wellbore fluids due to excessive
natural pressure.
find more resources at oneclass.com
find more resources at oneclass.com
Offshore drilling refers to a mechanical process where a wellbore is drilled through the seabed. It is
typically carried out in order to explore for and subsequently extract petroleum which lies in rock
formations beneath the seabed. Most commonly, the term is used to describe drilling activities on
the continental shelf, though the term can also be applied to drilling in lakes, inshore waters and
inland seas.
Offshore drilling presents environmental challenges, both from the produced hydrocarbons and the
materials used during the drilling operation. Controversies include the ongoing US offshore drilling
debate.
There are many different types of facilities from which offshore drilling operations take place. These
include bottom founded drilling rigs (jackup barges and swamp barges), combined drilling and
production facilities either bottom founded or floating platforms, and deepwater mobile offshore
drilling units (MODU) including semi-submersibles and drillships. These are capable of operating in
water depths up to 3,000 metres (9,800 ft). In shallower waters the mobile units are anchored to the
seabed, however in deeper water (more than 1,500 metres (4,900 ft)
the semisubmersibles or drillships are maintained at the required drilling location using dynamic
positioning.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Diamond offshore provides offshore contract drilling services to the energy industry around the globe and is a leader in deepwater drilling. Our customers are the world"s oil companies (operators), and our sole job is to drill and complete* wells at the direction of our customers (*completion in industry terms means preparing the well for production. This entails running production casing, stimulation work, and zonal isolation to allow the well to flow hydrocarbons). Because we work offshore, often in remote locations, each of our drilling rigs is largely self-sufficient. When contracted, they come with a full crew and the equipment and supplies needed to carry out the assigned task, be it one short well or multiple years of work. Mexico, crews typically work a rotational schedule consisting of 21 consecutive days aboard the rig followed by 21 days off. In international locations, our crews typically work a rotational schedule of 28 days on and 28 days off.
