ON SHORE DRILLING RIGS :
A onshore drilling rig is a machine that creates holes in the earth's subsurface. Drilling rigs can be massive structures housing equipment used to drill water wells, oil wells, or natural gas extraction wells, or they can be small enough to be moved manually by one person and such are called augers. Drilling rigs can sample subsurface mineral deposits, test rock, soil and groundwater physical properties, and also can be used to install sub-surface fabrications, such as underground utilities, instrumentation, tunnels or wells. Drilling rigs can be mobile equipment mounted on trucks, tracks or trailers, or more permanent land or marine-based structures (such as oil platforms, commonly called 'offshore oil rigs' even if they don't contain a drilling rig).
The term "rig" therefore generally refers to the complex equipment that is used to penetrate the surface of the Earth's crust.
Small to medium-sized drilling rigs are mobile, such as those used in mineral exploration drilling, blast-hole, water wells and environmental investigations. Larger rigs are capable of drilling through thousands of metres of the Earth's crust, using large "mud pumps" to circulate drilling mud (slurry) through the drill bit and up the casing annulus, for cooling and removing the "cuttings" while a well is drilled. Hoists in the rig can lift hundreds of tons of pipe. Other equipment can force acid or sand into reservoirs to facilitate extraction of the oil or natural gas; and in remote locations there can be permanent living accommodation and catering for crews (which may be more than a hundred). Marine rigs may operate thousands of miles distant from the supply base with infrequent crew rotation or cycle.
PETROLEUM DRILLING INDUSTRY
Oil and natural gas drilling rigs are used not only to identify geologic reservoirs but also to create holes that allow the extraction of oil or natural gas from those reservoirs. Primarily in onshore oil and gas fields once a well has been drilled, the drilling rig will be moved off of the well and a service rig (a smaller rig) that is purpose-built for completions will be moved on to the well to get the well on line.This frees up the drilling rig to drill another hole and streamlines the operation as well as allowing for specialization of certain services, i.e. completions vs. drilling.
MINING DRILLING INDUSTRY
Mining drilling rigs are used for two main purposes, exploration drilling which aims to identify the location and quality of a mineral, and production drilling, used in the production-cycle for mining. Drilling rigs used for rock blasting for surface mines vary in size dependent on the size of the hole desired, and is typically classified into smaller pre-split and larger production holes. Underground mining (hard rock) uses a variety of drill rigs dependent on the desired purpose, such as production, bolting, cabling, and tunnelling.
Simple diagram of a drilling rig and its basic operation is below attached for ONGC PROJECT in India .
Drilling rigs typically include at least some of the following items: See Drilling rig (petroleum) for a more detailed description.
BLOWOUT PREVENTERS: (BOPS)
The equipment associated with a rig is to some extent dependent on the type of rig but are devices installed at the wellhead to prevent fluids and gases from unintentionally escaping from the borehole. is the annular is the pipe rams and blind rams. In the place of Variable bore rams or VBRs can be used. These offer the same pressure and sealing capacity found in standard pipe rams, while offering the versatility of sealing on various sizes of drill pipe, production tubing and casing without changing standard pipe rams. Normally VBRs are used when utilizing a tapered drill string (when different size drill pipe is used in the complete drill string).
Centrifuge : Is an industrial version of the device that separates fine silt and sand from the drilling fluid.
Solids control: Solids control equipment is for preparing drilling mud for the drilling rig.
Chain tongs: Wrench with a section of chain, that wraps around whatever is being tightened or loosened. Similar to a pipe wrench.
Degasser: a device that separates air and/or gas from the drilling fluid.
Desander / desilter: contains a set of hydrocyclones that separate sand and silt from the drilling fluid.
Draw works: It is the mechanical section that contains the spool, whose main function is to reel in/out the drill line to raise/lower the traveling block .
Drill bit: It is a device attached to the end of the drill string that breaks apart the rock being drilled. It contains jets through which the drilling fluid exits.
Drill pipe: Joints of hollow tubing used to connect the surface equipment to the bottom hole assembly (BHA) and acts as a conduit for the drilling fluid. In the diagram, these are "stands" of drill pipe which are 2 or 3 joints of drill pipe connected together and "stood" in the derrick vertically, usually to save time while tripping pipe.
Elevators: A gripping device that is used to latch to the drill pipe or casing to facilitate the lowering or lifting (of pipe or casing) into or out of the borehole.
Mud motor: A hydraulically powered device positioned just above the drill bit used to spin the bit independently from the rest of the drill string.
Mud pump: Reciprocal type of pump used to circulate drilling fluid through the system.
Mud tanks: Often called mud pits, provides a reserve store of drilling fluid until it is required down the wellbore.
Rotary table: Rotates the drill string along with the attached tools and bit.
Shale shaker: Separates drill cuttings from the drilling fluid before it is pumped back down the borehole
DRILLING RIG CLASSIFICATION
There are many types and designs of drilling rigs, with many drilling rigs capable of switching or combining different drilling technologies as needed.
DRILLING RIGS CAN BE DESCRIBED USING ANY OF THE FOLLOWING ATTRIBUTES:
BY POWER USED :
- Mechanical — the rig uses torque converters, clutches, and transmissions powered by its own engines, often diesel
- Electric — the major items of machinery are driven by electric motors, usually with power generated on-site using internal combustion engines
- Hydraulic — the rig primarily uses hydraulic power
- Pneumatic — the rig is primarily powered by pressurized air
BY PIPE USED
- Cable — a cable is used to raise and drop the drill bit
- Conventional — uses metal or plastic drill pipe of varying types
- Coil tubing — uses a giant coil of tube and a downhole drilling motor
BY HEIGHT :
(Rigs are differentiated by height based on how many connected pipe they are able to "stand" in the derrick when needing to temporarily remove the drill pipe from the hole. Typically this is done when changing a drill bit or when "logging" the well.)
- Single — can pull only single drill pipes. The presence or absence of vertical pipe racking "fingers" varies from rig to rig.
- Double — can hold a stand of pipe in the derrick consisting of two connected drill pipes, called a "double stand".
- Triple — can hold a stand of pipe in the derrick consisting of three connected drill pipes, called a "triple stand".
- Quadri — can store stand of pipe in the derrick composed of four connected drill pipes, called a "quadri stand".
BY METHOD OF ROTATION OR DRILLING METHOD :
- No-rotation includes direct push rigs and most service rigs
- Rotary table — rotation is achieved by turning a square or hexagonal pipe (the "Kelly") at drill floor level.
- Top drive — rotation and circulation is done at the top of the drill string, on a motor that moves in a track along the derrick.
- Sonic — uses primarily vibratory energy to advance the drill string
- Hammer — uses rotation and percussive force (see Down-the-hole drill)
BY POSITION OF DERRICK :
- Conventional — derrick is vertical
- Slant — derrick is slanted at a 45 degree angle to facilitate horizontal drilling.
MOBILE DRILLING RIG MOUNTED ON A TRUCK
In early oil exploration, drilling rigs were semi-permanent in nature and the derricks were often built on site and left in place after the completion of the well. In more recent times drilling rigs are expensive custom-built machines that can be moved from well to well. Some light duty drilling rigs are like a mobile crane and are more usually used to drill water wells. Larger land rigs must be broken apart into sections and loads to move to a new place, a process which can often take weeks.
Small mobile drilling rigs are also used to drill or bore piles. Rigs can range from 100 ton continuous flight auger (CFA) rigs to small air powered rigs used to drill holes in quarries, etc. These rigs use the same technology and equipment as the oil drilling rigs, just on a smaller scale.
Lloyds Inspection Agency company who is an expertise in Oil Rig Industry , inspects mobile drilling rigs for all Government Projects in India and in international levels ( Globally ) .
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