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Drilling rig preparing rock blasting
Drilling rig preparing rock blasting
Drilling Rig, Reverse circulation in Western Australia
Drilling Rig, Reverse circulation in Western Australia
Petroleum drilling rig. Capable of drilling thousands of feet
Petroleum drilling rig. Capable of drilling thousands of feet

A drilling rig is a machine which creates holes (usually called boreholes) and/or shafts in the ground. A borehole is the generalised term for any narrow shaft drilled in the ground either vertically or horizontally 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. West Texas PumpjackJPG|thumb|right|300px|This Pumpjack located south of Midland TX is a common sight in West Texas. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, They sample sub-surface mineral deposits, test rock, soil and groundwater physical properties, and 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'). An oil platform or oil rig is a large structure used to house workers and machinery needed to drill and/or extract oil and Natural gas through wells The term "rig" therefore generally refers to the complex of equipment that is used to penetrate the surface of the earth's crust.

Drilling rigs can be:

Contents

Petroleum drilling industry

Oil and Natural Gas drilling rigs can be used not only to identify geologic reservoirs but also to create holes that allow the extraction of oil or natural gas from those reservoirs. Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Petroleum ( L petroleum, from Greek πετρέλαιον, lit Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Primarily in on shore 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, ie. completions vs. drilling.

History

Antique drilling rig now on display at Western History Museum in Lingle, Wyoming. It was used to drill many water wells in that area -- many of those wells are still in use.
Antique drilling rig now on display at Western History Museum in Lingle, Wyoming. It was used to drill many water wells in that area -- many of those wells are still in use.

Until internal combustion engines came in the late 19th century, the main method for drilling rock was muscle power of man or animal. The internal combustion engine is an engine in which the Combustion of Fuel and an Oxidizer (typically air occurs in a confined space called a Rods were turned by hand, using clamps attached to the rod. The rope and drop method invented in Zigong, China used a steel rod or piston raised and dropped vertically via a rope. Zigong ( ancient name Ziliujing and Gongjing is a Prefecture-level city and the third largest city in Sichuan Province, in southwest China. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National Mechanised versions of this persisted until about 1970, using a cam to rapidly raise and drop what, by then, was a steel cable.

Ancient Drilling Rigs in Zigong, China
Ancient Drilling Rigs in Zigong, China

In the 1970s, outside of the oil and gas industry, roller bits using mud circulation were replaced by the first efficient pneumatic reciprocating piston Reverse Circulation RC drills, and became essentially obsolete for most shallow drilling, and are now only used in certain situations where rocks preclude other methods. rc is the Command line interpreter for Version 10 Unix, Plan 9, and Inferno Operating systems It resembles the Bourne shell RC drilling proved much faster and more efficient, and continues to improve with better metallurgy, deriving harder, more durable bits, and compressors delivering higher air pressures at higher volumes, enabling deeper and faster penetration. Metallurgy is a domain of Materials science that studies the physical and chemical behavior of metallic elements, their intermetallic compounds, and their Diamond drilling has remained essentially unchanged since its inception.

Mobile drilling rigs

In early oil exploration, drilling rigs were semi-permanent in nature and 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. Units of mass There are three similar units of Mass called the ton: Long ton (simply ton in countries such as the United A deep foundation is a type of foundation distinguished from Shallow foundations by the depth they are embedded into the ground These rigs use the same technology and equipment as the oil drilling rigs, just on a smaller scale.

The drilling mechanisms outlined below differ mechanically in terms of the machinery used, but also in terms of the method by which drill cuttings are removed from the cutting face of the drill and returned to surface.

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

by pipe used

by height

by method of rotation or drilling method

by position of derrick

Drill types

There are a variety of drill mechanisms which can be used to sink a borehole into the ground. A derrick is a lifting device composed of one mast or pole which is hinged freely at the bottom A borehole is the generalised term for any narrow shaft drilled in the ground either vertically or horizontally Each has its advantages and disadvantages, in terms of the depth to which it can drill, the type of sample returned, the costs involved and penetration rates achieved. There are two basic types of drills: drills which produce rock chips, and drills which produce core samples. A core sample is a cylindrical section of a naturally occurring medium consistent enough to hold a layered structure

Auger drilling

Auger drilling is done with a helical screw which is driven into the ground with rotation; the earth is lifted up the borehole by the blade of the screw. A helix (pl helixes or helices) from the Greek word έλιξ, is a special kind of Space curve, i Hollow stem Auger drilling is used for environmental drilling,geotechnical drilling, soil engineering and geochemistry reconnaissance work in exploration for mineral deposits. Soil, often typeset as SOiL, is a four piece rock band from Chicago Illinois United States founded by Shaun Glass Tom Schofield Tim King and Adam Zadel Engineering is the Discipline and Profession of applying technical and scientific Knowledge and The field of geochemistry involves study of the chemical composition of the Earth and other Planets chemical processes and reactions that govern the composition A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Solid flight augers/bucket augers are used in construction drilling. In some cases, mine shafts are dug with auger drills. Mining is the extraction of valuable Minerals or other geological materials from the earth usually (but not always from an Ore body Small augers can be mounted on the back of a utility truck, with large augers used for sinking piles for bridge foundations.

Auger drilling is restricted to generally soft unconsolidated material or weak weathered rock. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere It is cheap and fast.

Cable tool water well drilling rig in Kimball, West Virginia. These slow rigs have mostly been replaced by rotary drilling rigs in the U.S.
Cable tool water well drilling rig in Kimball, West Virginia. Kimball is a town in McDowell County, West Virginia, United States. These slow rigs have mostly been replaced by rotary drilling rigs in the U. S.

Percussion rotary air blast drilling (RAB)

RAB drilling is used most frequently in the mineral exploration industry. The drill uses a pneumatic reciprocating piston-driven 'hammer' to energetically drive a heavy drill bit into the rock. The drill bit is hollow, solid steel and has ~20 mm thick tungsten rods protruding from the steel matrix as 'buttons'. The tungsten buttons are the cutting face of the bit.

The cuttings are blown up the outside of the rods and collected at surface. Air or a combination of air and foam lift the cuttings. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The most general definition of foam is a substance that is formed by trapping many gas Bubbles in a Liquid or Solid.

RAB drilling is used primarily for mineral exploration, water bore drilling and blast-hole drilling in mines, as well as for other applications such as engineering, etc. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Prospecting is the physical search for Minerals Fossils precious metals or mineral specimens and is also known as Fossicking. RAB produces lower quality samples because the cuttings are blown up the outside of the rods and can be contaminated from contact with other rocks. RAB drilling rarely achieves more than 150 metres depth as encountering water rapidly clogs the outside of the hole with debris, precluding removal of drill cuttings from the hole.

This can be counteracted, however, with the use of 'stabilisers' also known as 'reamers', which are large cylindrical pieces of steel attached to the drill string, and made to perfectly fit the size of the hole being drilled. These have sets of rollers on the side, usually with tungsten buttons, that constantly break down cuttings being pushed upwards.

The use of multiple high-powered air compressors, which push 900-1150cfm of air at 300-350psi down the hole also ensures drilling of a deeper hole up to ~1250m due to higher air pressure which pushes all rock cuttings and any water to the surface. This, of course, is all dependant on the density and weight of the rock being drilled, and on how worn the drill bit is.

Air core drilling

Air core drilling and related methods use hardened steel or tungsten blades to bore a hole into unconsolidated ground. Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74 The drill bit has three blades arranged around the bit head, which cut the unconsolidated ground. The rods are hollow and contain an inner tube which sits inside the hollow outer rod barrel. The drill cuttings are removed by injection of compressed air into the hole via the annular area between the innertube and the drill rod. The cuttings are then blown back to surface up the inner tube where they pass through the sample separating system and are collected if needed. Drilling continues with the addition of rods to the top of the drill string. Air core drilling can occasionally produce small chunks of cored rock.

This method of drilling is used to drill the weathered regolith, as the drill rig and steel or tungsten blades cannot penetrate fresh rock. Regolith ( Greek: "blanket rock" is a layer of loose Heterogeneous material covering solid rock. Where possible, air core drilling is preferred over RAB drilling as it provides a more representative sample. Air core drilling can achieve depths approaching 300 meters in good conditions. As the cuttings are removed inside the rods and are less prone to contamination compared to conventional drilling where the cuttings pass to the surface via outside return between the outside of the drill rob and the walls of the hole. This method is more costly and slower than RAB.

Cable tool drilling

SpeedStar Cable Tool Drilling Rig, Ballston Spa, NY
SpeedStar Cable Tool Drilling Rig, Ballston Spa, NY

Cable tool rigs are a traditional way of drilling water wells internationally and in the United States. The majority of large diameter water supply wells, especially deep wells completed in bedrock aquifers, were completed using this drilling method. Although this drilling method has largely been supplanted in recent years by other, faster drilling techniques, it is still the most practicable drilling method for large diameter, deep bedrock wells, and in widespread use for small rural water supply wells.

Also sometimes called "spudders", these rigs raise and drop a drill string to finely pulverize the subsurface materials. The drill string is comprised of the upper drill rods, a set of "jars" (inter-locking "sliders" that help transmit additional energy to the drill bit and assist in removing the bit if it is stuck) and a drill bit. During the drilling process, the drill string is periodically removed from the borehole and a bailer is lowered to collect the drill cuttings (rock fragments, soil, etc. ). The bailer is a bucket-like tool with a trapdoor in the base. If the borehole is dry, water is added so that the drill cuttings will flow into the bailer. When lifted, the bailer closes and the cuttings are then raised and removed. Since the drill string must be raised and lowered to advance the boring, casing (larger diameter outer piping) is typically used to hold back upper soil materials and stabilize the borehole.

Cable tool rigs are simpler and cheaper than similarly sized rotary rigs, although loud and very slow to operate. The world record Cable Tool Well was drilled in New York to a depth of almost 12,000 feet. The common Bucyrus Erie 22 can drill down to about 1,100 feet. Since cable tool drilling does not use air to eject the drilling chips like a rotary, instead using a cable strung bailer, technically there is no limitation on depth.

Reverse circulation (RC) drilling

Reverse Circulation (RC) rig, outside Newman, Western Australia
Reverse Circulation (RC) rig, outside Newman, Western Australia
Track mounted Reverse Circulation rig (side view).
Track mounted Reverse Circulation rig (side view). Newman, located about 1186 km north of Perth and 9 km north of the Tropic of Capricorn, is a town in the Pilbara region

RC drilling is similar to air core drilling, in that the drill cuttings are returned to surface inside the rods. The drilling mechanism is a pneumatic reciprocating piston known as a hammer driving a tungsten-steel drill bit. Pneumatics, Pressurized gas to affect mechanical motion Pneumatic power is used in Industry, where it is common to have factory units plumbed for Compressed RC drilling utilises much larger rigs and machinery and depths of up to 500 metres are routinely achieved. RC drilling ideally produces dry rock chips, as large air compressors dry the rock out ahead of the advancing drill bit. A gas compressor is a mechanical device that increases the Pressure of a Gas by reducing its Volume. RC drilling is slower and costlier but achieves better penetration than RAB or air core drilling; it is cheaper than diamond coring and is thus preferred for most mineral exploration work. Mineral exploration is the process undertaken by companies partnerships or corporations in the endeavour of finding Ore (commercially viable concentrations of minerals to

Reverse circulation is achieved by blowing air down the rods, the differential pressure creating air lift of the water and cuttings up the inner tube which is inside each rod. An airlift pump is a simple Pump which is powered by compressed Air. It reaches the bell at the top of the hole, then moves through a sample hose which is attached to the top of the cyclone. The drill cuttings travel around the inside of the cyclone until they fall through an opening at the bottom and are collected in a sample bag.

The most commonly used RC drill bits are 5-8 inches (12. 7–20. 32 cm) in diameter and have round metal 'buttons' that protrude from the bit, which are required to drill through rock and shale. Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by As the buttons wear down, drilling becomes slower and the rod string can potentially become bogged in the hole. This is a problem as trying to recover the rods may take hours and in some cases weeks. The rods and drill bits themselves are very expensive, often resulting in great cost to drilling companies when equipment is lost down the bore hole. Most companies will regularly 'sharpen' the buttons on their drill bits in order to prevent this, and to speed up progress. Usually, when something is lost (breaks off) in the hole, it is not the drill string, but rather from the bit, hammer, or stabiliser to the bottom of the drill string (bit). This is usually caused by a blunt bit getting stuck in fresh rock, over-stressed metal, or a fresh drill bit getting stuck in a part of the hole that is too small, due to having used a bit that has worn to smaller than the desired hole diameter.

Although RC drilling is air-powered, water is also used, to reduce dust, keep the drill bit cool, and assist in pushing cutting back upwards, but also when collaring a new hole. A mud called liqui-pol is mixed with water and pumped into the rod string, down the hole. In Geotechnical engineering, drilling mud, also known as spud mud (when beginning the drilling process is a Drilling fluid used to drill Boreholes This helps to bring up the sample to the surface by making the sand stick together. Occasionally, 'super-foam' (AKA 'quik-foam') is also used, to bring all the very fine cuttings to the surface, and to clean the hole. When the drill reaches hard rock, a collar is put down the hole around the rods which is normally PVC piping. Occasionally the collar may be made from metal casing. Collaring a hole is needed to stop the walls from caving in and bogging the rod string at the top of the hole. Collars may be up to 60 metres deep, depending on the ground, although if drilling through hard rock a collar may not be necessary.

Reverse circulation rig setups usually consist of a support vehicle, an auxiliary vehicle, as well as the rig itself. The support vehicle, normally a truck, holds diesel and water tanks for resupplying the rig. It also holds other supplies needed for maintenance on the rig. The auxiliary is a vehicle, carrying an auxiliary engine and a booster engine. These engines are connected to the rig by high pressure air hoses. Although RC rigs have their own booster and compressor to generate air pressure, extra power is needed which usually isn't supplied by the rig due to lack of space for these large engines. A gas compressor is a mechanical device that increases the Pressure of a Gas by reducing its Volume. Instead, the engines are mounted on the auxiliary vehicle. Compressors on an RC rig have an output of around 1000 cfm at 500 psi (500 L·s-1 at 3. The pound per square inch or more accurately pound-force per square inch (symbol psi or lbf/in² or lbf/in²) is a unit of 4 MPa). Alternatively, stand-alone air compressors which have an output of 900-1150cfm at 300-350 psi each are used in sets of 2, 3, or 4, which are all routed to the rig through a multi-valve manifold.

Diamond core drilling

Multi-combination drilling rig (capable of both diamond and reverse circulation drilling). Rig is currently set up for diamond drilling.
Multi-combination drilling rig (capable of both diamond and reverse circulation drilling). Rig is currently set up for diamond drilling.

Diamond core drilling (Exploration diamond drilling) utilises an annular diamond-impregnated drill bit attached to the end of hollow drill rods to cut a cylindrical core of solid rock. Exploration diamond drilling is used in the mining industry to probe the contents of Ore deposits The diamonds used are fine to microfine industrial grade diamonds. In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in They are set within a matrix of varying hardness, from brass to high-grade steel. Brass is any Alloy of Copper and Zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties Matrix hardness, diamond size and dosing can be varied according to the rock which must be cut. Holes within the bit allow water to be delivered to the cutting face. This provides three essential functions; lubrication, cooling, and removal of drill cuttings from the hole.

Diamond drilling is much slower than reverse circulation (RC) drilling due to the hardness of the ground being drilled. Drilling of 1200 to 1800 metres is common and at these depths, ground is mainly hard rock. Diamond rigs need to drill slowly to lengthen the life of drill bits and rods, which are very expensive.

Core samples are retrieved via the use of a lifter tube, a hollow tube lowered inside the rod string by a winch cable until it stops inside the core barrel. A core sample is a cylindrical section of a naturally occurring medium consistent enough to hold a layered structure As the core is drilled, the core lifter slides over the core as it is cut. An overshot attached to the end of the winch cable is lowered inside the rod string and locks on to the backend, located on the top end of the lifter tube. The winch is retracted, pulling the lifter tube to the surface. The core does not drop out the inside of the lifter tube when lifted because a "core lifter spring," located at the bottom of the tube allows the core to move inside the tube but not fall out.

Diamond core drill bits
Diamond core drill bits

Once a rod is removed from the hole, the core sample is then removed from the rod and catalogued. The Driller's offsider screws the rod apart using tube clamps, then each part of the rod is taken and the core is shaken out into core trays. The core is washed, measured and broken into smaller pieces using a hammer to make it fit into the sample trays. Once catalogued, the core trays are retrieved by geologists who then analyse the core and determine if the drill site is a good location to expand future mining operations.

Diamond rigs can also be part of a multi-combination rig. Multi-combination rigs are a dual setup rig capable of operating in either a reverse circulation (RC) and diamond drilling role (though not at the same time). This is a common scenario where exploration drilling is being performed in a very isolated location. The rig is first set up to drill as an RC rig and once the desired metres are drilled, the rig is set up for diamond drilling. This way the deeper metres of the hole can be drilled without moving the rig and waiting for a diamond rig to set up on the pad

Direct Push Rigs

Direct push technology includes several types of drilling rigs and drilling equipment which advances a drill string by pushing or hammering without rotating the drill string. The Drill Floor is the heart of any Drilling rig and is also known as the pad. This should perhaps not properly be called drilling, however the same basic results (i. e. a borehole) are achieved. A borehole is the generalised term for any narrow shaft drilled in the ground either vertically or horizontally Direct push rigs include both cone penetration testing (CPT) rigs and direct push sampling rigs such as a Geoprobe. The cone penetration test (CPT is an In situ testing method used to determine the Geotechnical engineering properties of Soils and delineating soil Direct push rigs typically are limited to drilling in unconsolidated soil materials and very soft rock.

CPT rigs advance specialized testing equipment (such as electronic cones), and soil samplers using large hydraulic rams. Most CPT rigs are heavily ballasted (20 metric tons is typical) as a counter force against the pushing force of the hydraulic rams which are often rated up to 20kn. Alternatively, small, light CPT rigs and offshore CPT rigs will use anchors such as screwed-in ground anchors to create the reactive force. An anchor is an object often made out of metal that is used to attach a ship to the bottom of a body of water at a specific point In ideal conditions, CPT rigs can achieve production rates of up to 250-300 meters per day.

Geoprobe rigs use hydraulic cylinders and a hydraulic hammer in advancing a hollow core sampler to gather soil and groundwater samples. The speed and depth of penetration is largely dependent on the soil type, the size of the sampler, and the weight and power the rig. Direct push techniques are generally limited to shallow soil sample recovery in unconsolidated soil materials. The advantage of direct push technology is that in the right soil type it can produce a large number of high quality samples quickly and cheaply, generally from 50 to 75 meters per day. Rather than hammering, direct push can also be combined with sonic (vibratory) methods to increase drill efficiency.

Hydraulic-rotary drilling

Oil well drilling utilises three-cone roller, fixed-cutter diamond, or diamond-impregnated drill bits to wear away at the cutting face. West Texas PumpjackJPG|thumb|right|300px|This Pumpjack located south of Midland TX is a common sight in West Texas. This is preferred because there is no need to return intact samples to surface for assay as the objective is to strike a formation containing oil or natural gas. Sizable machinery is used, enabling depths of several kilometres to be penetrated. Rotating hollow drill pipes carry down bentonite and barite impregnated drilling muds to lubricate, cool, and clean the drilling bit. Bentonite is an absorbent Aluminium phyllosilicate generally impure Clay consisting mostly of Montmorillonite. Baryte ( Ba[[Sulfur S]] O 4 is a Mineral consisting of Barium sulfate. In Geotechnical engineering, drilling mud, also known as spud mud (when beginning the drilling process is a Drilling fluid used to drill Boreholes The mud travels to the surface around the outside of the drilling rods. Examining rock chips extracted from the mud is known as mud logging. Mud logging, also known as hydrocarbon well logging is a type of borehole logging performed by the Mud logger, that provides well owners with information about the Lithology Another form of well logging is electronic and is frequently employed to evaluate the existence of possible oil and gas deposits in the well hole. This can take place while the well is being drilled, using Measurement While Drilling tools, or after drilling, by lowering measurement tools into the newly-drilled hole. Measurement while drilling is a tool that transmits information in real time from the tool located near the drill bit to the surface Well logging, also known as borehole logging is the practice of making a detailed record (a well log) of the Geologic formations penetrated by a borehole

The rotary system of drilling was in general use in Texas in the early 1900s. It is a modification of one invented by Fauvelle in 1845, and used in the early years of the oil industry in some of the oil-producing countries in Europe. Originally pressurized water was used instead of mud, and was almost useless in hard rock before the diamond cutting bit. [1]

The drilling and production of oil and gas pose a safety risk and a hazard to the environment from the ignition of the entrained gas causing dangerous fires and also from the risk of oil leakage polluting water, land and groundwater. Safety is the state of being "safe" (from French sauf) the condition of being protected against physical social spiritual financial political See also Nature The natural environment, commonly referred to simply as the environment, is a terminology that is comprised of all living and For these reasons, redundant safety systems and highly trained personnel are required by law in all countries with significant production.

Sonic (Vibratory) Drilling

A sonic drill head works by sending high frequency resonant vibrations down the drill string to the drill bit, while the operator controls these frequencies to suit the specific conditions of the soil/rock geology.

Resonance magnifies the amplitude of the drill bit, which fluidizes the soil particles at the bit face, allowing for fast and easy penetration through most geological formations. An internal spring system isolates these vibrational forces from the rest of the drill rig.

Limits of the technology

Drill technology has advanced steadily since the 19th century. However, there are several basic limiting factors which will determine the depth to which a bore hole can be sunk.

All holes must maintain outer diameter; the diameter of the hole must remain wider than the diameter of the rods or the rods cannot turn in the hole and progress cannot continue. Friction caused by rotation will tend to reduce the outside diameter of the drill bit. This applies to all drilling methods, except that in diamond core drilling and oil well drilling the use of thinner rods and casing may permit the hole to continue. Casing is simply a hollow sheath which protects the hole against collapse during drilling, and is often made of metal or PVC. Often diamond holes will start off at a large diameter and when outside diameter is lost, thinner rods put down inside casing to continue, until finally the hole becomes too thin. Alternatively, the hole can be reamed.

For percussion techniques, the main limitation is air pressure. Air must be delivered to the piston at sufficient pressure to activate the reciprocating action, and in turn drive the head into the rock with sufficient strength to fracture and pulverise it. With depth, volume is added to the in-rod string, requiring larger compressors to achieve operational pressures. Secondly, groundwater is ubiquitous, and increases in pressure with depth in the ground. Groundwater is Water located beneath the Ground surface in Soil pore spaces and in the Fractures of lithologic formations Pressure (symbol 'p' is the force per unit Area applied to an object in a direction perpendicular to the surface The air inside the rod string must be pressurised enough to overcome this water pressure at the bit face. Then, the air must be able to carry the rock fragments to surface. This is why depths in excess of 500 m for reverse circulation drilling are rarely achieved, because the cost is prohibitive and approaches the threshold at which diamond core drilling is more economic.

Diamond drilling can routinely achieve depths in excess of 1200 m. In cases where money is no issue, extreme depths have been achieved because there is no requirement to overcome water pressure. However, circulation must be maintained to return the drill cuttings to surface, and more importantly to maintain cooling and lubrication of the cutting surface.

Without sufficient lubrication and cooling, the matrix of the drill bit will soften. While diamond is one of the hardest substances known to man at 10 on the Mohs hardness scale, it must remain firmly in the matrix to achieve cutting. The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material Weight on bit, the force exerted on the cutting face of the bit by the drill rods in the hole above the bit, must also be monitored.

One final phenomenon limiting drilling only became apparent during deep drilling of an attempted Mohole.

Causes of deviation

All drill holes deviate from their plan. This is because of the torque of the turning bit working against the cutting face because of the flexibility of the steel rods and especially the screw joints, because of reaction to foliation and structure within the rock, and because of refraction as the bit moves from different rock units of varying rheology. Foliation is any penetrative planar fabric present in rocks. Foliation is common to rocks affected by regional metamorphic compression typical of orogenic Refraction is the change in direction of a Wave due to a change in its Speed. Rheology is the study of the flow of matter mainly liquids but also soft solids or solids under conditions in which they flow rather than deform elastically Additionally, inclined holes will deviate upwards usually because the drill rods will lie against the bottom of the bore, causing the drill bit to be slightly inclined from true. It is because of deviation that drill holes must be surveyed if deviation will impact on the usefulness of the information returned. Often oil companies will use a process of controlled deviation called directional drilling. Directional drilling (or slant drilling) is the practice of drilling non-vertical wells It can be broken down into three main groups Oilfield Directional

Rig personnel

Personnel on a drilling rig vary greatly depending on the size of the rig, type of rig, and the type of well being drilled (directional vs straight, extended reach, etc). A list of the most common rig personnel is as follows:

Rig equipment

The equipment associated with a rig is to some extent dependent on the type of rig but typically includes at least some of the following items

See also

References

  1. ^ This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petroleum", a publication now in the public domain. An oil platform or oil rig is a large structure used to house workers and machinery needed to drill and/or extract oil and Natural gas through wells West Texas PumpjackJPG|thumb|right|300px|This Pumpjack located south of Midland TX is a common sight in West Texas. In Machining, boring is the process of enlarging a hole that has already been drilled (or cast by means of a single-point cutting tool (or of a boring “Nodding donkey” redirects here For the train see British Rail "Pacer". Mineral exploration is the process undertaken by companies partnerships or corporations in the endeavour of finding Ore (commercially viable concentrations of minerals to Subsea is a general term frequently used to refer to equipment technology and methods employed to explore drill and develop oil and gas fields that exist below the ocean floors The Encyclopædia Britannica Eleventh Edition (1910–1911 is a 29-volume reference work that marked the beginning of the Encyclopædia Britannica The public domain is a range of abstract materials &ndash commonly referred to as Intellectual property &ndash which are not owned or controlled by anyone

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