Offshore Drilling Vessels

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Questions and Answers

What is the primary advantage of drillships compared to semisubmersibles?

Ability to operate in deeper water

Faster drilling speed

Less costly unless dynamically positioned (correct)

Increased stability in harsh weather conditions

What is the purpose of the central turret in some drillships?

To increase the drilling speed

To support the anchoring system

To provide additional storage

To rotate the ship and face incoming waves (correct)

What is the main limitation of using drillships in offshore drilling?

High operational costs

Severe weather conditions (correct)

Water depth limitations

Limited availability of drillships

What is the purpose of the Mud Circulating System in a rotary drilling rig?

To circulate drilling fluid Signup and view all the answers

What is the primary function of the Rig Power System in a rotary drilling rig?

To provide power to the hoisting and circulating systems Signup and view all the answers

What type of engines are typically used as prime movers in a rotary drilling rig?

Diesel-electric engines Signup and view all the answers

What is the primary function of the Well Control System in a rotary drilling rig?

To control the well pressure Signup and view all the answers

What is the typical location of the diesel engines in a rotary drilling rig?

On the ground in back of the rig Signup and view all the answers

What is the primary purpose of the substructure in a drilling rig?

To raise the elevation of the derrick floor to accommodate the BOP stack Signup and view all the answers

What is the typical working pressure range for blowout preventers?

3,000 to 15,000 psi Signup and view all the answers

What is the primary function of the choke manifold?

To direct flow from the well to various equipment Signup and view all the answers

Where is the control panel for the choke manifold located?

On the drill floor Signup and view all the answers

What is the purpose of the choke line?

To connect the BOP stack to the choke manifold Signup and view all the answers

In the scenario described, what is the length of the casing string occupied by the blown-out fluid?

3,000 ft Signup and view all the answers

What is the reservoir pressure of the gas-bearing zone in the scenario?

10,000 psi Signup and view all the answers

What is the density of the drilling fluid in the scenario?

80 lb/cu.ft Signup and view all the answers

What is the purpose of special marine equipment when drilling from a floating vessel?

To hold the vessel on location over the borehole and compensate for wave action Signup and view all the answers

What is the sequence of drilling a well?

Drill 26” hole, set 20” casing, cement 20” casing Signup and view all the answers

What is the purpose of cementing the casing?

To hold the casing in place Signup and view all the answers

What is the purpose of running electric logs?

To obtain detailed information about the formation Signup and view all the answers

What is the purpose of drilling a 17-1/2” hole?

To set a 20” casing Signup and view all the answers

What is the primary function of a set of clamps on a drilling rig?

To grip a stand, or column, of casing, tubing, drill pipe, or sucker rods Signup and view all the answers

What is the purpose of setting a 13-3/8” casing?

To provide additional support to the well Signup and view all the answers

What is the purpose of a catwalk on a drilling rig?

To lift pipe to the derrick floor by the catline or by an air hoist Signup and view all the answers

What is the primary function of a pipe rack on a drilling rig?

To provide a horizontal support for tubular goods Signup and view all the answers

What is the Rotating System used for on a drilling rig?

To wrap around a joint of a pipe and pull to start screwing two joints together Signup and view all the answers

What is the primary function of a drill collar?

To put weight on the bottom of the drillstring to control drilling and to prevent the drillpipe from kinking and breaking Signup and view all the answers

What is the typical length of a drill collar?

31 ft Signup and view all the answers

What is the purpose of a cathead on a drilling rig?

To serve as a spool-shaped attachment on a winch for hoisting and pulling Signup and view all the answers

What is the purpose of a pipe ramp on a drilling rig?

To serve as an angled ramp for dragging drill pipe up to the drilling platform Signup and view all the answers

What is the term for the pipe pulled three joints at a time?

Stands Signup and view all the answers

Where does the bottom of the stand rest?

On the drill floor Signup and view all the answers

What is the purpose of a bit breaker in the rotary table?

To grip the bit Signup and view all the answers

What is the formula for cost per foot of drilled section?

C = B + R*T + T∖ + t Signup and view all the answers

What is the term for the process of changing the bit and running the pipe back into the hole?

Tripping in Signup and view all the answers

What is the name of the working platform of the derrickman?

Monkey board Signup and view all the answers

What is the unit of measurement for the length of the section drilled?

Feet Signup and view all the answers

What is the purpose of the formula 𝐂 = 𝐅/(𝐁+𝐑 𝐓+𝐓∖+𝐭)?

To calculate the cost per foot of drilled section Signup and view all the answers

Study Notes

Drillship

A type of floating vessel used in offshore drilling
Less costly than semisubmersibles unless designed to be positioned dynamically
Can operate in water depths up to 13,000 ft
Some drillships have rig equipment and anchoring system mounted on a central turret, allowing the ship to rotate and face incoming waves

Rotary Drilling Rigs

All rotary rigs have the same basic drilling equipment
Main component parts of a rotary drilling rig:
- Rig Power System
- Hoisting System
- Rotary System
- Mud Circulating System
- Well Control System
- Well Monitoring System
- Special Marine Equipment

Rig Power System

Prime movers are diesel engines that supply power to the rig
Power is used primarily for hoisting and circulating systems, and to a lesser degree for rotating system, rig lights, and other motors

Elevators and Pipe Racks

Elevators: a set of clamps that grip a stand of casing, tubing, drill pipe, or sucker rods
Pipe racks: a horizontal support for tubular goods

Rotating System

Drillstring consists of drillpipe, heavyweight drillpipe, and drill collars
Drill collars are made of heat-treated alloy steel and are 31 ft long
Two to ten drill collars are often used
Drillpipe is stored horizontally on the pipe rack located on the ground next to the front of the rig

Types of Drilling Bits

Milled (steel) tooth roller cone bits
Insert tooth roller cone bits
Roller cone types
Fixed cutter (head) bits

Bit Selection

Cost per foot = (bit cost + operating cost) / (length of section drilled)
Cost per foot is affected by bit cost, operating cost, and length of section drilled

Drillstring Design

Important factors to consider when designing a drillstring: weight, strength, and durability
Drillstring must be able to withstand the forces and stresses encountered during drilling

Blowout Preventers (BOPS)

Working pressures range from 3,000 to 15,000 psi
Substructure is a steel framework that raises the elevation of the derrick floor to accommodate the BOP stack below it
Choke manifold is a series of lines, automatic valves, gauges, and chokes on the ground next to the drilling rig

Special Marine Equipment

Required for drilling from a floating vessel
Special equipment is needed to hold the vessel on location over the borehole and to compensate for vertical, lateral, and tilting movements caused by wave action against the vessel

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Description

This quiz covers the features and capabilities of drillships, a type of floating vessel used in offshore drilling. It discusses their cost and operation in deep water.

Offshore Drilling Vessels - Drillships

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