Rig

A Blow Out Preventer commonly known as BOP is a large valve placed on top of a well. As the name suggests, BOP is used to prevent a blowout in a well.

The conventional process of drilling a well maintains the pressure (force per unit area) inside the wellbore higher than the formation pressure. The difference between the hydrostatic pressure in the well and the fluid pressure in the formation being drilled is called overbalance. Overbalance is considered the 'Primary Barrier' in a well.

If for any reason, this primary barrier fails and the hydrostatic pressure in the well falls below the formation pressure, the formation fluid will start entering the well. If this situation is allowed to continue, the heavier drilling fluid will be completely displaced by the formation fluid, which will be gushing out of the well with high force due to pressure from the formation. This situation is called a blowout.

Blow-Out Preventers are designed to close the well and contain the pressure in such scenarios. BOP makes it possible not only to avoid a blow-out but also to circulate the kick out of the well by displacing the well with kill weight fluid. Different types of BOPs are placed on top of the well in the form of a stack. BOPs have different pressure ratings depending on the type of well being drilled.

Burner Booms or Flare Booms are arrangement of gas, oil & diesel lines with water spraying nozzles that is used on rigs / platforms for flaring oil and gas flowing from the the well.

Caisson is a reinforced hull that is used in Arctic Submersible rig. In winter, ice blocks tend to flow with the ocean current and apply enough force to damage the jack up legs or barge hulls. Hence reinforced hulls called "Caisson" are used with arctic submersible rigs. The rig is towed to location when the sea is ice free and Caissons are submerged into sea bottom to allow uninterrupted operations even with ice flow.

Catwalk is a raised platform above the ground or main deck. The pipes or tools required to be picked up to the rig floor are kept ready on the catwalk. They are pulled to the rig floor through the V-door as and when required.

Centrifuge is a solid control equipment used on drilling rigs for removing fine and ultrafine particles from drilling fluid. Many solid removal equipment are used on the rigs, but centrifuge removes the finer particles that the other equipment like shale shaker or hydro-cyclones are not able to remove. Removing fine solids from mud system is important to be able to maintain mud properties within required specifications for drilling a well.

Not able to remove fine solids increases percentage of low-gravity solids (LGS) in the mud system, which adversely affects rate of penetration (ROP) and bit performance resulting in more trips for drilling the same footage. The mud becomes thicker and harder to pump, causing higher equivalent circulating density (ECD). Higher percentage of LGS also requires dilution, needing additional chemicals to maintain required mud properties.

Centrifuges use conical drums which rotate at high Revolutions Per Minute (RPM) to produce high G-force. Drilling fluid enters from one end and solids are separated from liquid phase due to high G-force to exit the bowl from the other end. Advanced centrifuges use variable frequency drive to be able to operate at varying speed to match required RPM of the bowl.

Choke valve is a mechanical device that is used for creating restriction in a flow line to vary the pressure or flow rate. Two types of chokes used on the rigs are fixed choke or variable choke.

A fixed choke has a fixed orifice size to allow the flow through the valve. The term ‘bean’ is used to refer to the piece of hardware installed inside the valve that has an orifice or opening drilled into it. If there is a need to change the bean for changing size of the opening or for replacement due to erosion, the valve needs to be disassembled.

An adjustable or variable choke provides the mechanism to be able to vary orifice sizes either manually or hydraulically through a remote panel. Adjustable choke makes it possible to accommodate a range of pressure and flow rate changes without the need to disassemble the valve.

Choke manifold is an arrangement of special valves called choke valves. The manifold is used for diverting the flow from the well when BOPs are closed in well control, well killing or well testing operations. The manifold consists of high pressure pipes, valves and pressure gauges to be able to safely handle pressure from the well. It has adjustable choke valves, which can be manually or hydraulically controlled from a remote panel.

In well testing and production operations, choke manifold facilitates managing speed and pressure of flow of formation fluid that enter the processing equipment through an arrangement of fixed and adjustable choke valves. This helps in controlling production and reduces the risk of equipment damage downstream of the choke manifold.

CIDS is an acronym for "Concrete Inland Drilling System". It's a bottom supported MODU that is used for drilling wells in arctic conditions and is also known as "Arctic Submersible". CIDS or Arctic submersible rig is used for drilling arctic wells in shallow waters. In winter, ice blocks tend to flow with the ocean current and apply enough force to damage the jack up legs or barge hulls. Hence reinforced hulls called "Caisson" are used with arctic submersible rigs. CIDS is towed to location when the sea is ice free and Caissons are submerged into sea bottom to allow uninterrupted operations even with ice flow.

Crown Block is a mechanical arrangement of one or more pulleys on a common axel. It is mounted on the top of the derrick or mast. Drilling line passes over these pulleys and over the pulleys of the travelling block. This arrangement helps in hoisting or lowering the travelling block by winding or unwinding the drilling line of the Drawworks drum.

Desander is a solid removal equipment that uses Hydrocyclone principle for removing larger solids from drilling fluid. It is placed after degasser in sequence of fluid flow system on the rig. Degassed mud is injected into desander as a tangential flow. The centrifugal forces generated due to the movement of fluid through the hydrocyclone moves the solid particles outwards. The dispersed particles move downward in a spiral path as underflow while the cleaner and lighter density liquid mud travels up through a vortex in the center of the hydrocyclone, exiting through piping at the top of the hydrocyclone. Desander cones are usually available 8 – 12 inch diameter to remove drilling solid particles in 50 - 80 micron range. Hydrocyclones are made of polyurethane because of its wear resistance and less weight than steel.

Desilter is a solid removal equipment that uses Hydrocyclone principle for removing smaller solids from drilling fluid. It is placed after desander in sequence of fluid flow system on the rig. Drilling fluid is injected into desilter as a tangential flow. The centrifugal forces generated due to the movement of fluid through the hydrocyclone moves the solid particles outwards. The dispersed particles move downward in a spiral path into as underflow while the cleaner and lighter density liquid mud travels up through a vortex in the center of the hydrocyclone, exiting through piping at the top of the hydrocyclone. Desilter cones are 4-6 inche diameter to remove fine sands and silt particles down to 20 micron. Hydrocyclones are made of polyurethane because of its wear resistance and less weight than steel.

Derrick and Mast are tall steel structures built to support the loads of the drilling tools which can weigh many tones. The tallest Derricks or Masts are about 200 ft where as the shortest is about 65 ft. The Mast structure is assembled in horizontal position and then raised to vertical as a single unit on a pivot point using the power of drawworks or hydraulic pistons. Whereas Derrick is assembled vertically by bolting one piece at a time.

Drilling line is made up of steel wires and looks like wire rope. One end of the drilling line is clamped on the dead line anchor in the substructure of the rig. The drilling line passes over pulleys of travelling block and crown block and is wrapped around the drawworks drum. Its fast end is attached to the drawworks. Drilling line ranges from 7/8 to 2 inches in diameter depending on the load capacity of the rig.

Drilling Rig is a structure and a package of various equipment used for drilling a well. Broad classification of a drilling rig is 'Land Rig' and 'Offshore Rig'. Offshore rigs are further classified based on their capacity to operate in certain water depths as 'Inland rig', 'Jack Up Rig', 'Drill Ship' and 'Semi-submersible rig'. Different parts of a drilling rig are derrick, substructure, engines, generator, drilling tubulars, hoisting equipment, pumps, steel tanks, solid control equipment etc.

A Drill Ship, also known as a Floater, is like a ship. It has a drilling rig and all associated equipment for drilling a well. It has a self-propulsion mechanism and can venture into ultra-deepwater to drill remote offshore locations. Drill ships are used for drilling wells in 1,000 feet to 10,000 feet water depths. Drillships use advanced dynamic positioning systems to maintain their position over the drilling location without anchors. These rigs are highly mobile and can be quickly deployed to different locations.

Drawworks is a hoisting equipment on the drilling rig. Drilling line is wrapped around the drum of the drawworks. Rotating the drum makes it possible to move the travelling block up or down. Drawworks consists of a drum, cathead and brake bands.

Drawworks are rated in horse power depending on their capacity to lift the heaviest weight.

Heavy lift vessel is a special purpose cargo ship that is used for moving offshore rigs long distance. The process is called 'dry tow'. Offshore Jack Up rigs are not self propelled units and need to be towed using tug bats from one location to another. If the two locations are too far from each other, this towing may take a very long time. To reduce the rig mobilization time, the rig is loaded on to a Heavy Lift Vessel. HLV can sail at a much faster speed thus reducing the rig mobilization time considerably.

A set of equipment is used for raising or lowering the drill string. The hoisting arrangement on a rig consists of Drawworks, Derrick or Mast, Crown Block, Travelling Block and Drilling Line.

Hydrocyclones are used on drilling rigs as solid control equipment for separation of solid particles from drilling fluid. They are commonly known as desander and desilter. Both use the same principle for separating solid particles from drilling fluid, but have size and ability to remove different size of particles.

Hydrocyclones do not have any moving part. They depend on the feed pressure, or velocity, into the cyclone to generate a centripetal force. This centripetal force allows the cyclone to separate coarse or dense particles from fine particles and liquid phase.

The equipment is formed by a cone in the lower part and in the upper part by a cylinder. Liquid slurry enters at the top of the conical wall of the hydrocyclone through a vortex finder which creates tangential flow creating a strong vortex in the hydrocyclone.

They depend on the feed pressure, or velocity to generate a centripetal force. This centripetal force allows the cyclone to separate coarse or dense particles from fine particles and liquid phase. Coarse particles move closer to the wall due to higher centrifugal force and exit from the lower end whereas fines suspended in the liquid move up through the middle part of the vortex to exit from the top.

A jack-up rig stands on legs that penetrate the seabed to provide stability. The rig’s deck is elevated above the water, providing safety from tidal motions and waves. Depending on the Rig capacities, they are primarily deployed for developmental or exploratory drilling in water depths up to 500 feet deep. Jack-up rigs usually have the mast on a cantilever with longitudinal and transverse motion.

Kelly is a steel tubular with hexagonal or square profile. It is connected between swivel and drill string. Kelly acts as a conduit for drilling fluid to be circulated from mud pump through drill string. Kelly passes through the kelly drive bushing with matching profile. Kelly drive bushing sits in the master bushing of the rotary table. The square or hexagonal profile of the kelly locks it in with the drive bushing and helps in transmitting rotary motion of rotary table to the drill string through kelly.

A drilling rig that is located in the dry land is called land rig. Land rigs are of various kinds and vary in size depending on their load capacity and power to drill wells of certain depth. They can broadly be classified as light duty, medium duty, heavy duty and very heavy duty depending on their depth capacity to drill wells.

Lift nubbins or lift caps are used for lifting drill pipe or drill collars with catline, winch or crane as the case may be. Lift nubbin has threads matching to the box end of the pipe and a lift handle or bails to be able to fasten a clamp. Once the threaded part of the nubbin is screwed into the box end of the pipe, a clamp is connected to the lift handle of the lift nubbin or cap for lifting the pipe. The clamp could be connected to a sling from catline, winch or a crane to provide required pull.

Lift nubbins or caps are manufactured from a single piece of high quality steel to ensure integrity of the lifting accessory and eliminate risk of failure. Lift caps or nubbins are made as light as possible for handling while still offering the required factor of safety for lifting the load.

Derrick and Mast are tall steel structures built to support the loads of the drilling tools which can weigh many tones. The tallest Derricks or Masts are about 200 ft where as the shortest is about 65 ft. The Mast structure is assembled in horizontal position and then raised to vertical as a single unit on a pivot point using the power of drawworks or hydraulic pistons. Whereas Derrick is assembled vertically by bolting one piece at a time.

MODU is an acronym for "Mobile Offshore Drilling Unit". It is a broad term used for all types of offshore rigs. MODUs are broadly classified as Bottom Supported or Floating units. Bottom supported units are either Submersibles or Jack Ups. Floating Units are either Semisubmersibles of Drill ships.

Mooring system is a mechanism used for station keeping of a floating vessel or a platform in sea. The system consists of Mooring lines, anchors and connectors. Different type of mooring systems that are commonly used are catenary, taut leg, semi-taut, spread, single point and dynamic positioning. Type and configuration of mooring system to be deployed depends on water depth and environmental factors like wind, wave and current. Dynamic positioning (DP) uses computer controlled thrusters and propellers to maintain vessel's position. DP vessels can combine with other mooring systems for redundancy.

Poor boy degasser is an equipment to separate harmful gas in drilling mud and discharge harmful gas away from rig floor to a flaring area complete with an ignition source as per environmental regulations. It's a vertical vessel that is rigged up downstream of choke manifold during well control situation.

Height and diameter of an atmospheric separator are critical dimensions which affect the volume of gas and fluid the separator can efficiently handle. Baffles are installed inside the vessel which assist the fluid and gas separation process. Gas and fluid inlet should be located approximately at the midpoint of the vertical height of the vessel. This provides the top half for a gas chamber and the bottom half for gas separation and fluid retention.

Rig Building is the process of erecting a drilling or workover rig on a new land location. Once the operations on a location are completed, the mast is lowered and dismantled from specific joints. All the rig equipment are disconnected and transported by road to new location. At the new location, all the pieces of mast are joined. Once all accessory equipment are connected, the mast is raised as part of the process to get the rig ready for operations.

Land drilling rigs are portable. When they finish drilling a well in one location, the mast is rigged down and can be transported to another location. The process of rigging down, transport and rigging up on another location is termed as rig move.

Self Contained Breathing Apparatus (SCBA) is a portable breathing apparatus used by the rig crew for protection in H2S environment. SCBA provides effective face seal and oxygen supply for 30 minutes to avoid inhaling poisonous gas. It provides unrestricted movement for carrying out emergency search and rescue operations. More physical work consumes more air and hence SCBAs are equipped with an alarm when a quarter air supply remains in the equipment to have enough escape time.

A semi-submersible rig is a floating offshore drilling unit. As the name suggests, a semisubmersible rig is partially submerged in water. The rig floats on hollow steel cross-sections called "Pontoons." Some semi-submersible rigs have propulsion systems that allow them to navigate drilling sites under their own power, while others require a second vessel to tow them to the location. Most rigs use several anchors that help maintain the structure's orientation. Computers control the tension on each anchor chain to correct for drift. Since the rig doesn't float on the water surface, it provides a more stable drilling platform than a drillship. Semisubmersible rigs are used for drilling wells in 1,000 feet to 3,500 feet of water depth.

Manual slips secure the drill string within the rotary table during drilling operations. Slips are constructed with three or more hinged steel wedges, which form a nearly circular shape when placed around the drill pipe. Replaceable inserts are embedded into the inner side of the steel wedges. The outer surface of the slips is tapered to match the inner taper of the insert bowl of the rotary table. As the drill pipe is lowered into the slips, the inserts grip the pipe, causing the slips to descend and securely lock everything together. Resting the drill string securely in slips allows disconnecting of the upper part of the drill string while the lower portion remains suspended. After attaching another component to the lower portion, lifting the string releases the slip for lowering the drill string for further operations.

Slip Crushing

Spider elevator and slips are used for casing running operation. They are used instead of regular slips when the rotary table bushing size is not compatible with the tubular being run. Spider elevators are also used for running flush joint casing pipes because flush joint casings don’t have the collar. The spider elevator grips the body of pipe while running in or pulling out of a hole.

Spider slips & elevators are powered by a heavy duty high-strength coil spring or by air. Driller or another crew member can operate the power slips remotely through a remote panel.

A stabbing board is a temporary platform rigged up in the derrick or mast to facilitate casing running operation. It is installed some 20 to 40 ft above the rig floor where derrickman or another crew member guides the casing joint while running casing in a well. The board may be wooden or fabricated of steel girders floored with anti-skid material.

Sophisticated stabbing board designs are powered electrically to be raised or lowered to the desired level and can be folded back to avoid possibility of damage to the board when not in use. Stabbing board serves the same purpose for casing running as a monkey board to running drill pipe stands but is temporary instead of permanent.

On some large land rigs with 38 foot substructures, most offshore jack-ups and even semi-submersibles used in shallow water have a deck below the rotary table and rig floor where workers can access the BOP stack. This deck is called 'Texas Deck' or 'Texas Floor'. This deck is suspended from the cantilever by adjustable cables and is accessed from the main deck by semipermanent stairwell. Texas deck is used primarily for installing the wellhead and nippling the BOP stack up and down. Height of Texas Deck can be adjusted in most designs as they are often hung from overlying substructure with cables.

Top Drive or Power Swivel is swivel that hangs on to the hook of the travelling block. It has the passage way for the mud to flow from mud system through the drill string. Top drive also has powerful motors to rotate the drill string and bit. Top drive replaces, kelly, kelly bushing and rotating master bushing.

Travelling Block is a mechanical arrangement of pulleys. Drilling line passes over these pulleys and also over the pulleys of crown block mounted on top of the derrick or mast. The travelling block moves up and down as the drilling line winds or unwinds on Drawworks drum making it possible to hoist or lower loads as part of drilling operations.