Types of Drilling Rigs Explained!

What types of rigs will I see in the field?

Oil reserves are found in many different regions covering a huge variety of terrains and climates. Consequently, drilling companies have designed many kinds of rigs which you may encounter in the field. In this post, we will be explaining some of the more common onshore and offshore rig types. To keep things interesting, we’ve also added a couple of interesting kinds that you might not hear about elsewhere. 

Offshore Rigs 

(Jack-Ups, Submersibles, Semi-Submersibles, Posted Barges, Drill Ships, Inland Barges, Arctic Submersibles)

Jack-Ups

The Jack-up Rig is the most commonly used platform in the modern offshore industry due to its impressive versatility. The majority of Jack ups have three legs with a triangle shaped hull (you might also see four-legged models). The legs are commonly open truss like structures, however some rigs will have cylindrical columns, pillars or some other design.

The Jack up rig has no means of propulsion, so it must be towed into position by tugboats or a heavy lift vessel. Once the rig is positioned over the drilling location, the crew lowers the jacks until they make contact with the ocean floor. They will then raise the hull out of the water, past the highest predicted wave height, so that the operation can move ahead safely and efficiently. 

As we mentioned, Jack-Ups are exceptionally versatile drilling platforms. Larger units can operate in up to 400ft (120m) of water and drill holes to a depth of 30,000ft (9100m)- 5.5 miles!

Submersibles

The submersible drilling rig floats on the water’s surface. Similar to the Jack-Ups, it is either towed to the drill location or transported via a heavy lift vessel. When it is situated, the crew floods the pontoon-like floats, sinking them to the sea floor. With the base of the rig resting on the sea floor, the platform is resilients against wind, waves and ocean currents.

It is important to remember that a Submersible and Semi-Submersible are two different things. While a submersible sits on the sea floor, a semi-submersible is simply flooded enough that its pontoons are below the water’s surface.

Semi Submersible

A semi-sub is very similar in design to the submersible drilling rig. It is not self propelled and generally floats on two large pontoons. Once the platform is in place, the air in the pontoons is displaced with water until the rig is level and the floats are a few feet below the surface. It is then anchored to the sea floor and is ready to operate. Some of the newer semi-subs may also have a Dynamic Positioning System which uses several thrusters to stay in place over the well.

Semi-subs are very popular because they can operate in deeper water than a jack-up, while being far more stable than a drill-ship. They frequently operate in depths ranging from 1,000ft (300m) to 12,000ft (3,660m), drilling wells as far down as a 35,000ft (10,670m). 

Drill Ships

Drill ships generally operate in remote locations. The drill ship can operate in depths ranging from 10,000ft (3,000m) whilst still being able to perform drilling operations of up to 30,000ft (9,100m). A drill ship is a highly mobile, self propelled ship with a stream lined hull, much like any other ocean liner. The drill ship is a preferred choice for operations in remote locations due to its ability to move independently. Furthermore, it can hold a substantial amount of equipment and supplies, thereby requiring less frequent resupplying from an onshore base.

Inland Barge

Often called swamp barges, an Inland barge has a flat-bottomed, rectangular box for a hull. It is constructed as a unit, with drilling rig, components, and equipment on right top of the deck. As the name suggests, the inland barge is not designed for application at sea. They would generally drill in marshes, swamps, bays and other shallow waters. Like the submersibles, it is towed to its drill location where the ballast tanks are flooded until it sits on the floor of the body of water.

Posted Barge

Offshore drilling rigs are referred to in the industry as Mobile Offshore Drilling Units (MODU). One of the first MODU to successfully drill a well was a Posted Barge in 1949, operating in 18ft of water in the Louisiana Gulf. A posted barge is the same concept as an inland, or swamp, barge, but with an added space between the deck and drilling apparatus so it can work in greater depths. This design proved that mobile rigs could work offshore, but it has since been phased out by more advanced, efficient designs.

Arctic Submersibles

As the name suggests, Arctic submersibles are specialized for use in the Arctic where there may be large ice floes. If there is potential for a profitable well, these specially reinforced submersibles are towed into position during the short summer season. They operate identically to a regular submersible, but are protected by a heavy reinforced caisson. What makes them distinct from a regular submersible is that they are protected by a reinforced caisson which can deflect massive chunks of ice, protecting the rig and the drilling operation.

Onshore Rigs

(Rotary Tool Drilling Rig, Cable Tool Drilling Rig)

Cable Tool Drilling

Cable tool drilling works by the same principle as a see-saw or teeter-totter in a children’s play area. A walking beam is centred over a pivot point with a weighted chisel or bit on one end. Weighted sinker bars raise and lower the bit, slamming it into the earth. A derrick is used to provide space for the length of cable, with drawing power from a bull wheel. Cable tool drilling is outdated and hasn’t been heavily used since the 1920s for many reasons: drilling must be stopped periodically to remove cuttings, it is difficult to maintain pressure in the wellbore, there is a much greater chance of a blow out, it cannot drill very deep, and it is extremely slow compared to a rotary tool system.

Rotary Tool Drilling Rig

The rotary drilling rig effectively replaced cable tool drilling. It is a far more efficient and cost effective means of extracting oil and gas from the Earth. The rotary tool system mechanically rotates a drill bit deep into the Earth. Workers on the rig floor attach the bit to the end of a long sequence of hollow pipes called the drill string. As the hole becomes deeper, the crew will add more lengths of pipe (much like an extension on a hand drill). The rig can use one of three systems to rotate the drill string: a turn table, a top drive or a down hole motor.

Bonus!

Heavy Lift Ship

As we mentioned above, many offshore rigs must be transported to the drill site. Tug boats are not efficient over a great distance so this task usually falls to a heavy lift ship. These massive ocean liners use a ballast system to sink enough to slide under the body of a rig, as the tanks are refilled with air, the ship rises up under the rig and lifts it for transport.

While a heavy lift ship obviously isn’t a drilling rig, it is a very cool innovation which seems worth noting.

 

If you like this article, we have lots more!

https://dtetechnology.wordpress.com/2014/05/04/components-of-a-land-based-rotary-drilling-platform/

https://dtetechnology.wordpress.com/2014/05/05/whos-who-on-a-land-rig/

As always, let’s keep it down to earth!

Who’s who on a land rig?

While each rig will be a little different, there are six positions which you will consistently see on any land drilling site.

1) Leasehand: This is an entry level position on a land rig. Leasehands are responsible for general labour and maintenance tasks.

2) Roughneck: The roughneck, or floorhand, handles drill pipe on the rig floor. In some cases, rigs won’t have leasehands and roughnecks must also cover their duties. They generally work in teams of two or three.

3) Motorhand/Lead Roughneck: Aside from working on the rig floor, the motorhand helps with the training of new employees and maintaining the diesel motors. 

4) Derrickman: The derrickman controls the top end of the pipe from the monkey board. They also monitor fluid rates and mix drilling mud. 

5) Driller: The driller is primarily in charge of operating the draw works and rotary equipment. They also supervise all work crews on the rig floor. They are responsible for training new hands and report directly to the rig manager.

6) Rig Manager/ Tool Pusher: The tool push is the big boss on a drilling rig. They manage rig operations, coordinate daily operations, provide leadership and are generally responsible for keeping the entire operation running smoothly. 

Components of a Land-Based Rotary Drilling Platform

Labelled Diagram of a Land-Based Drilling Rig

Glossary of Terms to Accompany “Components of a Rotary Rig Explained”

Components Of A Rotary Rig Explained!

1. Mud Pit – A man made pit dug into the earth next to the drilling rig. It is used to house the drilling fluid (mud) or waste materials discarded after the treatment of drilling fluid. Steel tanks are now more commonly in use but are still referred to as ” mud pits”. Mud tank is the preferred terminology used on off shore rigs.

2. Shale Shaker – Or commonly called a shaker. A vibrating mesh-like screen used to separate cuttings made by the drill bit. The diameter of openings in the screen shall be as small as possible to allow 100% of the circulating fluid to pass through, therefore depositing the cuttings directly into the reserve pit.

3. Suction Line – A pipe tube or hose that delivers the fluid form the mud pits to the inlet side of mud pump.

4. Mud Pumps – Or slush pumps. A large, high-pressure, positive displacement pump used to circulate drilling fluid through the circulating system and back to the mud pit. Typically you will see three or more on one site depending on the size and depth of the rig and well bore.

5. Engine Generator sets – are the main source of power on a rig. A combustion engine used to convert heat content of fuel into rotary motion, as well as powering other equipment during the drilling process.

6. Vibration Dampening Hose – The hose which extends from the mud pumps; it is designed to prevent the movement of the pumps from vibrating farther down the line. Left unchecked, these vibrations can damage equipment and will produce a lot of unnecessary noise.

7. Draw Works – This is the hoisting system that every rig uses to raise or lower the travelling blocks and the drill string. It spools off or takes in the drilling line which is attached to the crown blocks and, in turn, the travelling blocks and drill string.

8. Stand Pipe – Drill pipe stood vertically alongside the mast or derrick ready to be added to the drill string.

9. Rotary Kelly Hose – Delivers high pressure drilling fluid to the drill string.

10. Goose neck – A curved join that allows the connection of the rotary kelly hose to the kelly and the swivel.

11. Travelling blocks – Are hung in the centre of the the derrick or mast by the crown blocks and the drilling line via a series of pulleys. It can be raised or lowed using the draw works.

12. Cat Line – The cat line is a separate hoist line powered by the cat head which is located on separate spools on either side of the draw works. The purpose of these lines is to aid with tripping in and tripping out as well as hoisting heavy equipment around the rig floor.

13. Crown Blocks – The crown blocks sit at the very top of the derrick or mast, it is an assembly of sheaves on axles. The drilling line is spooled off the draw works through the crown blocks and eventually to the travelling blocks.

14. Derrick – Don’t get confused between a derrick and a mast they are two different components. The derrick is a tall load bearing structure in the centre of the substructure. The derrick is assembled piece by piece at the rig site. By contrast, the mast is a portable unit which can be raised or lowered as a complete structure when necessary.

15. Monkey Board – Is where the Derrick Man will work during the tripping in and tripping out operations. The monkey board is placed high in the derrick or mast.

16. Drill pipe – Is the pipe used to extend the drill string, they have a male and female threaded connection on each end. Drill pipe is commonly 30ft per length and is hollow to allow the drilling fluid to pass through.

17. Substructure – Often referred to as the drill floor, this is the main structure where all drilling operations take place.

18. Swivel – The swivel is an essential tool hung from the hook on the travelling blocks, it is used to permit rotary motion from the motionless hook to the spinning drill string. The swivel also provides a connection for the rotary hose and a passageway for the drilling fluid into the drill string.

19. Kelly – Normally four or six sided heavy duty steel tubular device suspended from the swivel and connected to the last unit of drill pipe to turn the drill string as the rotary table turns. The Kelly also has a bored passage through it which allows flow of drilling fluid to the drill string and up the annulus. Kellys are normally 54ft or 17m long.

20. Rotary Table – Also known as the turn table. This is the primary component used to rotate the drill string and support the drilling assembly.

21. Rat Hole – The Rat Hole is a hole made into the substructure and lined with pipe, placed just off to the side of the main bore hole. This is where the Kelly is stored during hoisting operations.

22. B.O.P Stack – ”Blow Out Preventer”. In my opinion, this is the most important part off any oil rig. The B.O.P Stack is the assembly of various types of blow out preventer’s installed underneath the substructure. During a kick, these BOPs seal off the well bore to keep pressure down hole rather than allowing it to explode through the substructure.

23. Annular Blow Out Preventer – Part of the B.O.P Stack and the first set of blow out preventers. It is essentially a valve that when manipulated will seal off the annular space between the pipe and the well bore, or if there is no pipe is present the Annular B.O.P will close off the entire bore hole. The Annular B.O.P has a flexible seal that is forced to take on whatever shape is in the bore of the preventer.

24. Ram Blow Out Preventer – The Ram preventer is usually placed below the Annular Preventer. It operates by closing two flat rams completely together, crushing anything between them, and sealing off the wellbore and the drill pipe.

25. Drill String – Is the column of drill pipe, collars and tools connected together to form the drill string. The drill string is what transmits drilling fluid and rotational power from the Kelly and rotary table to the drill bit itself.

26. Drill Bit – The drill bit is the cutting element attached to the very bottom of the drill string. Click here for more on drill bits.

27. Conductor Casing – Also known as Conductor Pipe and Drive Pipe. This is the first string of casing cemented into the bore to prevent softer formations from caving into the well bore. This type of casing also helps conduct the drilling fluid from the bottom of the hole to the surface when drilling starts. 

28. Diverter line – A pipe directed at diverting the fluids from a well to a safe location during an unexpected release of fluid.

Thunderhorse Lit Up at Night

This picture of the Thunderhorse rig was originally posted on OilRig-Photos.com. Thunderhorse is a joint venture of BP and Exxon-Mobile, it is currently operating in the Gulf of Mexico.

The Drilling Industry: A Simplified Overview

You might be considering a career in drilling, you could already be working in the industry, or you could just be interested in learning a little more about the process of extracting oil. In any case, this is the blog for you!

The oil and gas industry is unbelievably expansive, but this blog will focus on breaking down the drilling side of the operation. Drilling refers to the process of cutting deep into the earth’s surface to identify geological deposits and create a hole for extracting crude when a viable reservoir is found.

Almost every rig in operation today is a Rotary Rig, meaning that they use a spinning point to drive through geological formations. Think of an 18V drill you’d use in your garage, the principle is the same. The rig drives a bit into the ground, using drill pipe (hollow lengths of metal) to extend the drill string and enable the creation of deeper wells.

If you’ve ever been on an airplane, you’re familiar with the concept of pressure. The same pressure that pops your ears would collapse the walls if you tried to drill straight down without any controls. To balance the pressure in the well bore with the balance of the pressure in the earth’s formation, weighted mud, or drilling fluid, is pumped into the well and circulated. The mud is very important, not only does it maintain pressure, but it also keeps the bit cool and cycles out the cuttings from the bottom of the well.

The drill string and the mudworks are the two main ingredients of an oil rig, but there’s obviously much more you need to know. This is a very, very simplified overview of the drilling process. Bear with us as we explain each step and component in much greater detail.

Let’s keep it down to earth!

Welcome to our new drilling blog!

The purpose of this blog is to present a blue-collar, practical explanation of the complicated industry that is oil and gas drilling. We will be including interactive content explaining the roles of each rig worker, the equipment you might encounter, and useful contact information for companies actively involved in drilling.

Let’s keep it down to earth!