Types of Drilling Rigs Overview

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Questions and Answers

What features contribute to the stability of a semi-submersible rig?

Its low position in the water and large mooring anchors contribute to its stability.

What is the maximum water depth at which some semi-submersibles can drill?

Some semi-submersibles can drill in depths over 5000 ft (1524 m).

How does a drill ship differ from semi-submersibles regarding mobility?

A drill ship does not require tugboats for towing to its location.

In what kind of environments are drilling barges typically used?

Drilling barges are used in inland, shallow, or smooth offshore areas. Signup and view all the answers

What is the main function of a Floating Production, Storage and Offloading System (FPSO)?

An FPSO produces and stores oil until it is offloaded to a tanker. Signup and view all the answers

What materials are commonly used to construct a bottom-supported platform?

Platforms are typically built from steel or concrete. Signup and view all the answers

What is the composition of a steel jacket platform?

It consists of a jacket made from tubular steel members and is supported by piles driven into the seabed. Signup and view all the answers

What additional facilities are typically found on top of a steel jacket platform?

Additional sections provide space for drilling rigs, crew quarters, and other equipment. Signup and view all the answers

What are the main design features of land drilling rigs?

The main design features of land drilling rigs are portability and maximum operating depth. Signup and view all the answers

Name two types of marine drilling rigs.

Two types of marine drilling rigs are semi-submersible floating rigs and bottom-supported offshore rigs. Signup and view all the answers

List three operations that take place before drilling starts at a land rig location.

Preparing the location, digging the cellar, and installing the conductor pipe are three operations. Signup and view all the answers

What distinguishes floating drilling units from bottom-supported units?

Floating drilling units float on water, while bottom-supported units are anchored to the seabed. Signup and view all the answers

What is a typical sequence of operations for drilling a land well?

The sequence includes preparing the location, installing the conductor pipe, and moving the rig on site. Signup and view all the answers

What is the purpose of the columns in a semi-submersible floating rig?

The columns are flooded with seawater to submerge the structure to a predetermined depth. Signup and view all the answers

What are the two main types of offshore drilling rigs?

The two main types of offshore drilling rigs are floating rigs and bottom-supported rigs. Signup and view all the answers

What is a jackup rig, and how does it function?

A jackup rig is a type of bottom-supported rig that uses legs to elevate the platform above water. Signup and view all the answers

What is the primary feature of a Concrete Gravity Platform?

It utilizes tall caissons that are heavy enough to maintain stability through gravity. Signup and view all the answers

Why are Steel-Caisson Platforms specifically designed for cold areas?

They are constructed with two layers of thick steel to withstand damage from icy conditions. Signup and view all the answers

What distinguishes a compliant platform from a rigid steel-jacket platform?

Compliant platforms have fewer steel parts and are designed to be lighter for use in deep water. Signup and view all the answers

How does a Jack-up rig operate?

It uses long leg structures to lower into the seabed, lifting the rig out of the water. Signup and view all the answers

What is the process for moving a submersible rig?

Workers remove water from its compartment to make it float, then it is towed by a tugboat. Signup and view all the answers

List the three types of submersible rigs mentioned.

Inland Swamp Barge, Bottle-Type, and Arctic submersible. Signup and view all the answers

What preliminary step is taken before drilling begins?

A surface pipe is set and a shallow hole is drilled several hundred feet deep. Signup and view all the answers

What role do guy wires play in a guyed-tower platform?

They support the lightweight jacket of the platform, helping it stay stable. Signup and view all the answers

Study Notes

Drilling Rigs Types

All drilling rigs have the same basic components
Land rigs are categorized as jackknife or cantilever rigs, and portable-masts
Marine (or offshore) rigs are categorized as bottom-supported offshore rigs, semi-submersible floating rig, and drill- ship floating rig.

Drilling Rigs: Land Rigs

The first step is to prepare the location for drilling
Land rigs are used to drill wells on land.
Operations include:
- Preparing the landing area, digging a cellar, installing the conductor pipe, installing the rig, preparing the support pad for the rig, building roads, fences and digging pits
- Drilling a water well is sometimes required.
Once the rig is moved into place, the drillers rig it up and start drilling.

Drilling Rigs: Offshore Rigs

There are two main types of offshore rigs: floating and bottom-supported
Floating rigs include:
- Semi submersibles (bottle-type, column stabilized), barge rigs, and drill ships.
Bottom-supported rigs include:
- Submersibles (posted barges, bottle-type submersibles, arctic submersibles), jackups, and platforms.

Semi Submersibles

Semi submersibles are floating drilling units that have columns that flood with seawater, which causes the structure to submerge to a predetermined depth.
This type of rig is held in place by eight large mooring anchors and sits low in the water with a large portion of its structure submerged.
Semi submersibles can drill in water depths over 5000 ft (1524 m).
The semi submersible drills a hole in the seabed and then moves to the next location.

Drill Ships

Drill ships are ship-shaped drilling vessels.
They are not towed to location like semi-submersibles and jackups.
They are not as stable as semi submersibles but are still able to drill in very deep waters.

Drilling Barges

Drilling barges are barges equipped with special equipment for oil and gas drilling.
Unlike drill ships they do not have their own propulsion system and have to be towed to location.
Drilling barges are used in inland, shallow or smooth offshore areas where the water depth is typically less than 150 meters (< 492 ft).

FPSO

FPSO stands for Floating Production, Storage and Offloading Systems.
FPSOs are attached to a seabed wellhead and they produce and store oil until another tanker takes it from them.
They are used to produce from small wells where it would be too expensive to build a platform.

Platforms

Platforms are immobile structures that can be built from steel or concrete and rest on the seabed.
These structures are used to drill further wells at the same oil or gas location and produce the hydrocarbons.
Steel Jacket Platform
- The most common type of platform.
- Consists of a jacket made of tubular steel members.
- Supported by piles driven into the seabed.
- Additional sections on top of the jacket provide space for drilling rig, crew quarters, and other equipment.
Concrete Gravity Platform
- Platforms made from steel-reinforced concrete.
- Tall caissons or columns make up the platform's dominant feature.
- Sometimes special concrete cylinders are fixed at the base of the caissons on the sea floor to store crude oil.
Steel-Caisson Platform
- Used in cold areas with fast-moving tidal currents that can carry ice flows that can damage steel jackets.
- Caissons are made of two layers of thick steel to prevent ice damage.
Compliant Platform
- Using rigid platforms in water depths over 1000 ft is impractical and expensive.
- In deep water, most companies prefer compliant platforms, which contain fewer steel parts and are lighter than rigid steel-jacket platforms.

Jack-Ups

Jackups are mobile drilling rigs that operate differently from semi submersibles.
Instead of floating over the drilling location, jackups have long legs that lower down onto the seabed, elevating the rig out of the water.
The depth in which a jackup can operate is limited by the length of its legs.
The maximum depth is approximately 500 feet.

Submersibles

Submersible rigs rest on the seafloor while drilling.
When moving to a new location, water is removed from the compartments, which makes the rig float.
The rig is then towed to a new site.
Submersibles are designed to drill in shallow water, about 175 ft deep (53 m).
There are three types of submersibles: Inland Swamp Barge, Bottle-Type, and Arctic submersible.

Drilling Procedure (First Step)

The first step in drilling is to set a surface pipe.
This involves drilling a shallow hole that is several hundred feet deep.

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Description

Explore the various types of drilling rigs, including land and offshore rigs. This quiz covers their basic components, preparations for drilling, and specific categories like jackknife, cantilever, semi-submersible, and drill ships. Test your knowledge on the operational aspects of drilling rigs.