Well drilling is the process of drilling a hole in the ground for the extraction of a natural resource such as ground water, brine, natural gas, or petroleum, for the injection of a fluid from surface to a subsurface reservoir or for subsurface formations evaluation or monitoring. Drilling for the exploration of the nature of the material underground is best described as borehole drilling.
Underground hard-rock mining refers to various underground mining techniques used to excavate "hard" minerals, usually those containing metals, such as ore containing gold, silver, iron, copper, zinc, nickel, tin, and lead. It also involves the same techniques used to excavate ores of gems, such as diamonds and rubies. Soft-rock mining refers to the excavation of softer minerals, such as salt, coal, and oil sands.
In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one".
A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water, other liquids, or gases. It may also be part of a geotechnical investigation, environmental site assessment, mineral exploration, temperature measurement, as a pilot hole for installing piers or underground utilities, for geothermal installations, or for underground storage of unwanted substances, e.g. in carbon capture and storage.
The Mohorovičić discontinuity – usually called the Moho discontinuity, Moho boundary, or just Moho – is the boundary between the crust and the mantle of Earth. It is defined by the distinct change in velocity of seismic waves as they pass through changing densities of rock.
A drill bit is a cutting tool used in a drill to remove material to create holes, almost always of circular cross-section. Drill bits come in many sizes and shapes and can create different kinds of holes in many different materials. In order to create holes drill bits are usually attached to a drill, which powers them to cut through the workpiece, typically by rotation. The drill will grasp the upper end of a bit called the shank in the chuck.
Well logging, also known as borehole logging is the practice of making a detailed record of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface or on physical measurements made by instruments lowered into the hole. Some types of geophysical well logs can be done during any phase of a well's history: drilling, completing, producing, or abandoning. Well logging is performed in boreholes drilled for the oil and gas, groundwater, mineral and geothermal exploration, as well as part of environmental and geotechnical studies.
A drilling rig is an integrated system that drills wells, such as oil or water wells, or holes for piling and other construction purposes, into 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. The term "rig" therefore generally refers to the complex equipment that is used to penetrate the surface of the Earth's crust.
Scientific drilling into the Earth is a way for scientists to probe the Earth's sediments, crust, and upper mantle. In addition to rock samples, drilling technology can unearth samples of connate fluids and of the subsurface biosphere, mostly microbial life, preserved in drilled samples. Scientific drilling is carried out on land by the International Continental Scientific Drilling Program (ICDP) and at sea by the Integrated Ocean Drilling Program (IODP). Scientific drilling on the continents includes drilling down into solid ground as well as drilling from small boats on lakes. Sampling thick glaciers and ice sheets to obtain ice cores is related but will not be described further here.
Rock mechanics is a theoretical and applied science of the mechanical behavior of rocks and rock masses.
A core sample is a cylindrical section of (usually) a naturally-occurring substance. Most core samples are obtained by drilling with special drills into the substance, such as sediment or rock, with a hollow steel tube, called a core drill. The hole made for the core sample is called the "core hole". A variety of core samplers exist to sample different media under different conditions; there is continuing development in the technology. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired.
In geotechnical engineering, drilling fluid, also known as drilling mud, is used to aid the drilling of boreholes into the earth. Used while drilling oil and natural gas wells and on exploration drilling rigs, drilling fluids are also used for much simpler boreholes, such as water wells.
A modern core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit is referred to as the core.
Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information on the physical properties of soil earthworks and foundations for proposed structures and for repair of distress to earthworks and structures caused by subsurface conditions; this type of investigation is called a site investigation. Geotechnical investigations are also used to measure the thermal resistance of soils or backfill materials required for underground transmission lines, oil and gas pipelines, radioactive waste disposal, and solar thermal storage facilities. A geotechnical investigation will include surface exploration and subsurface exploration of a site. Sometimes, geophysical methods are used to obtain data about sites. Subsurface exploration usually involves soil sampling and laboratory tests of the soil samples retrieved.
BS 5930:2015, "the code of practice for site investigations", is a UK code of practice which came into effect on 31 July 2015 British Standards Institution.
Baptist well drilling is a very simple, manual method to drill water wells. The Baptist drilling rig can be built in any ordinary arc welding workshop and materials for a basic version costs about 150 US dollars. In suitable conditions, boreholes over 100 m deep have been drilled with this method.
A well is an excavation or structure created on the earth by digging, driving, or drilling to access liquid resources, usually water. The oldest and most common kind of well is a water well, to access groundwater in underground aquifers. The well water is drawn up by a pump, or using containers, such as buckets or large water bags that are raised mechanically or by hand. Water can also be injected back into the aquifer through the well. Wells were first constructed at least eight thousand years ago and historically vary in construction from a simple scoop in the sediment of a dry watercourse to the qanats of Iran, and the stepwells and sakiehs of India. Placing a lining in the well shaft helps create stability, and linings of wood or wickerwork date back at least as far as the Iron Age.
A down-the-hole drill, usually called DTH by most professionals, is basically a jackhammer screwed on the bottom of a drill string. The fast hammer action breaks hard rock into small cuttings and dust that are evacuated by a fluid. The DTH hammer is one of the fastest ways to drill hard rock. The system is thought to have been invented independently by Stenuick Frères in Belgium and Ingersoll Rand in the USA in the mid-1950s.
Ice drilling allows scientists studying glaciers and ice sheets to gain access to what is beneath the ice, to take measurements along the interior of the ice, and to retrieve samples. Instruments can be placed in the drilled holes to record temperature, pressure, speed, direction of movement, and for other scientific research, such as neutrino detection.
The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust and ends at the top of the lower mantle at 670 km (420 mi). Temperatures range from approximately 500 K at the upper boundary with the crust to approximately 1,200 K at the boundary with the lower mantle. Upper mantle material that has come up onto the surface comprises about 55% olivine, 35% pyroxene, and 5 to 10% of calcium oxide and aluminum oxide minerals such as plagioclase, spinel, or garnet, depending upon depth.
