1. List the types and main features and differences.
Ans: Rigs are of two types, Land Rigs and MODU(Mobile Offshore Drilling Unit).
Land Rigs are classified according to the maximum drilling feets.
Light duty 1000-1500mtrs
Medium 1200-3000mtrs
Heavy 3500-5000mtrs
Very Heavy 5500-7500mtrs
Mobile Offshore Drilling Unit:
Bottom Supported Units:
Submersibles
Barge types
Bottle types
Arctic Types
Inland Barges
Jackups.
Floating units:
Semi Submersibles
Drill Ships.
2. Describe the functions of all major components on a typical Rig,
1. Power Systems:
This basically consists of Diesel Engines and electric generators which provide for the requirements of energy for the rig. 2 or 4 generators provide the need for the power in a Rig.
2. Hoisting System:
The Hoisting system is made up of drawworks, a mast or derrick, the crown block, the traveling block, and the wire rope drilling line.
It is used for lifting the drill string in and out of the well.
Draw works: The Drawworks consist of a revolving drum around which the drill string is
Spooled. It actually lifts the drill string with the support of mast or derrick, Crown block & traveling block.
3. Rotating System:
This system is used for providing torque to the drill string for drilling or say to turn the bits.. Rotating System are of two types, one which uses Rotary Table and kelly to turn the bit. Assembly is made of turn table, Master bushings, tapered bowls, Kelly bushing, Kelly saver subs and Kelly. Turntable houses mechanism that generates turning motion to the string and providing torque.
Top Drive System: The other way is to use top drive system, to generate rotary motion to the drill string. A top drive or power swivel hangs from the traveling block and hook. The advantage of a top drive system over a Kelly system is that it is safe for crew members to handle the pipe and other benefit is that you can save time since 3 joints can be added at a time which makes it different from the conventional way of handling drill pipes one at a time.
Mud motors:
They provide rotation to the bit by converting hydraulic energy in to mechanical energy.
4. Circulating Systems:
Circulating System includes the mud pump, the discharge line, the standpipe, the rotary hose, the swivel and the Kelly, the drill pipe, the drill collars the bit the annulus, the return line, the shale shakers, the desilter, the desander, the mud tanks, and the suction line.
Shale Shakers: They are used to remove the cuttings that, the mud brings back to the surface from the bottom of the well.
Desilter: It is used remove the solid particles in the mud.
Desander: It is used to remove the fine particles of the cutting in the mud.
Degasser: It is used to remove the gasses that mix along with the mud from the formation to make it light in weight.
5. Well Control System.
This is a system used to prevent any kick or blow out that occur. This happens when the hydrostatic pressure in the well is underbalanced compared to formation pressure, resulting in to a kick. Blow out preventers prevent the blowout by shutting the well.
6. Drill String.
It includes the Bottom Hole Assembly and drill pipes. Bottom Hole Assembly consists of Drill bit, Mud Motor or Rotary Steerable System. MWD tools, LWD tools, Jars, Stabilizers. Other components are Drill Collars, Heavy weight drill pipes, drill pipes etc.
7. Mooring of Jacking System.
Semi submersibles use anchor systems and orientating motors to maintain position, whilst Jack up rigs jack themselves up onto large steel legs, which sit on the seabed. Mooring or Jacking System is inapplicable on land rigs.
8. Storage (bulk & Liquid)
Around the wellsite, there are a variety of storage systems for particular fluids and solids. Excess mud volumes are stored in either a reserve pit, or reserve tanks. Diesel fuel is stored in a large fuel container. Cement fluids are stored in large silos. Chemicals/cements are stored in manufacture containers, and kept on palettes. The BOP gas pressure system is located inside a covered housing (container), which contains many high pressure gas cylinders for powering the BOP system, if it is needed.
9. Cementing Hardware.
The cement hardware used after the casing is placed is as follows:
Cementing Head: An accessory attached to the top of the casing to facilitate cementing of the casing. It has passages of slurry and retainer chambers for cementing wiper plugs
Cementing Pump: a high pressure pump used to force cement down the casing and into the annular space between the casing and the wall of the borehole.
Cement Plug: A portion of the cement placed at some point in the well bore to seal it. There are two cementing plugs.
Well heads:
Once the well has been drilled, production casing been set and the well perforated, a Christmas tree is installed on top of the well. The tubing hangs from the well, allowing flow from the well to pass into the tree. The Christmas tree is a set of valves that allow the Operator to direct flow through different pipelines, or to close the well in entirely. The Christmas tree can also accommodate gauges to monitor wellhead pressure.
3. Describe the following functional jobs of each member of drilling crew as it relates to the major rig components.
Toolpusher - The Toolpusher is an employee of the drilling contractor who is in charge of the entire drilling crew and rig.
Driller - The driller’s responsibility is the operation of the drilling and hoisting equipment. He is also responsible for the downhole condition of the well.
Derrickman - The derrickman handles the top end of the drillpipe up on the monkey board. He is responsible for the racking of this pipe as it is being taken out of hole and unracking the pipe as it is being run in hole. He is also responsible for the circulating machinery and assists the mud engineer in conditioning the drilling fluid.
Motorman - The motorman is usually the most experienced rotary helper on the rig and is responsible for the care and operation of drilling engines.
Roughneck - Sometimes called a rotary helper. Roughnecks work on the drill floor breaking/making connections, etc.
4. Describe briefly the function of some of the most commonly found service companies in a rig.
Mud Logging companies:
Mud Logging Companies monitors and records or logs, the content of the drilling mud as it returns from the well. The returning mud carries cuttings and any formation fluids, such as oil or gas, to the surface. The operator can gain knowledge about the formations being drilled by analyzing the returning fluid.
Cementing Companies:
Cementing companies run casings in the open well and seals the formation with cement, ie they cement the space between the well wall and casing wall.
Bit Companies:
Bit companies provide the required bits for drilling, according to the formation expected to be drilled.
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