Exploration diamond drilling is used in the mining industry to probe the contents of known ore deposits and potential sites. By withdrawing a small diameter core of rock from the orebody, geologists can analyze the core by chemical assay and conduct petrologic, structural, and mineralogical studies of the rock. It is also often used in the geotechnical engineering industry for foundation testing in conjunction with soil sampling methods. The technique is named for the diamond encrusted drill bit used.
Rodolphe Leschot is often cited as being the inventor of the first core bit in 1863. [1] Early diamond drilling opened up many new areas for mineral mining, and was related to a boom in mineral exploration in remote locations. Before the invention of the portable diamond drill, most mineral prospecting was limited to finding outcrops at the surface and hand digging. In the late 1970s, General Electric pioneered the technology of polycrystalline diamond compacts (PDCs) as a replacement for natural diamonds in drill bits. [2]
Exploration diamond drilling differs from other geological drilling (such as Reverse Circulation (RC) Drilling [3] ) in that a solid core is extracted from depth, for examination on the surface. The key technology of the diamond drill is the actual diamond bit itself. [4] It is composed of industrial diamonds set into a soft metallic matrix. As shown in the figure, the diamonds are scattered throughout the matrix, and the action relies on the matrix to slowly wear during the drilling process, so as to expose more diamonds. The bit is mounted onto a core barrel, that is attached to the drill string, which is connected to a rotary drill rig. Drilling mud is injected into the drill pipe, so as to wash out the rock cuttings produced by the bit and also to reduce the heat produced due to friction which causes less wear and tear of the bits. [5] An actual diamond bit is a complex affair, usually designed for a specific rock type, with many channels for washing. [6]
The drill uses a diamond encrusted drill bit (pictured on the right) to drill through the rock. The drill produces a "core" which is photographed and split longitudinally. Half of the split core is assayed, while the other half is permanently stored for future use and re-assaying if necessary. Although a larger diameter core is the most preferred it is the most expensive. The most common wire line tube diameters and purposes are NQ (47.6mm) and HQ (63.5mm). [7]
Merely advancing the drill by rotary action (and washing) causes a core to be extracted inside the barrel as shown. However, at a depth of perhaps 300 m, there must be a way to retrieve the core and take it to the surface. Constantly withdrawing the entire heavy drill pipe is impractical, so wireline drilling methods were developed to pull up the core inside the barrel. [8] If the rock would always be solid granite, and the core would always break at the drill bit, then it would be a simple matter to stop the drilling, and lower a simple grabbing device by a wire and pull up the core. Unfortunately, many applications require an undisturbed core in fractured rock, which calls for elaborate wire-line devices.
The photo shows the extraction of a core, using a triple-tube wire-line system, capable of extracting core under the worst conditions. [9] This is very important when exploring fault zones such as the San Andreas Fault.
There are five major "wire line" tube sizes typically used. Larger tubes produce larger diameter rock cores and require more drill power to drive them. The choice of tube size is a trade-off between the rock core diameter desired and the depth that can be drilled with a particular drilling rig motor.
Standard "Q" wire line bit sizes: [10]
Size | Hole (outside) diameter, mm | Core (inside) diameter, mm |
---|---|---|
AQ | 48 | 27 |
BQ | 60 | 36.5 |
NQ | 75.7 | 47.6 |
HQ | 96 | 63.5 |
HQ3 | 96 | 61.1 |
PQ | 122.6 | 85 |
PQ3 | 122.6 | 83 |
CHD 76 | 75.7 | 43.5 |
CHD 101 | 101.3 | 63.5 |
CHD 134 | 134.0 | 85.0 |
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.
In the oil and gas industry, the term wireline usually refers to the use of multi-conductor, single conductor or slickline cable, or "wireline", as a conveyance for the acquisition of subsurface petrophysical and geophysical data and the delivery of well construction services such as pipe recovery, perforating, plug setting and well cleaning and fishing. The subsurface geophysical and petrophysical information results in the description and analysis of subsurface geology, reservoir properties and production characteristics.
Drill bits are cutting tools 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.
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.
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.
A drilling rig is used to create a borehole or well in the earth's sub-surface, for example in order to extract natural resources such as gas or oil. During such drilling, data is acquired from the drilling rig sensors for a range of purposes such as: decision-support to monitor and manage the smooth operation of drilling; to make detailed records of the geologic formations penetrated by a borehole; to generate operations statistics and performance benchmarks such that improvements can be identified, and to provide well planners with accurate historical operations-performance data with which to perform statistical risk analysis for future well operations. The terms measurement while drilling (MWD), and logging while drilling (LWD) are not used consistently throughout the industry. Although these terms are related, within the context of this section, the term measurement while drilling refers to directional-drilling measurements, e.g. for decision support for the wellbore path, while LWD refers to measurements concerning the geological formations penetrated while drilling.
A diamond tool is a cutting tool with diamond grains fixed on the functional parts of the tool via a bonding material or another method. As diamond is a superhard material, diamond tools have many advantages as compared with tools made with common abrasives such as corundum and silicon carbide.
Frank Langton Christensen was an American athlete. After receiving all-state honors at Granite High School in baseball, football, and basketball, Christensen played fullback at the University of Utah. "Crashing Chris" was the university's first three-time All-American. In 1930–31, he was named Third-team All-American, and in 1932 he earned First-team honors. During those years, the Utes owned a 21-3-1 record.
Slickline refers to a single strand wire which is used to run a variety of tools down into the wellbore for several purposes. It is used during well drilling operations in the oil and gas industry. In general, it can also describe a niche of the industry that involves using a slickline truck or doing a slickline job. Slickline looks like a long, smooth, unbraided wire, often shiny, silver/chrome in appearance. It comes in varying lengths, according to the depth of wells in the area it is used up to 35,000 feet in length. It is used to lower and raise downhole tools used in oil and gas well maintenance to the appropriate depth of the drilled well.
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.
Boring is drilling a hole, tunnel, or well in the Earth. It is used for various applications in geology, agriculture, hydrology, civil engineering, and mineral exploration. Today, most Earth drilling serves one of the following purposes:
Boart Longyear is an international mineral exploration company founded in 1890 in the United States. It is headquartered in Salt Lake City, Utah, with regional offices and operations in the Asia-Pacific region, North and South America, Europe, and Africa. The company provides mineral exploration services and drilling products for the mining industry and also has a presence in drilling water exploration, environmental sampling, energy, and oil sands exploration. As of 2018, it employed more than 5,000 people.
Orex Exploration is a former Canadian gold mining company that conducted exploration work on mining properties it owned in the Goldboro and Guysborough County areas of Nova Scotia. The properties owned by Orex were the sites of the former Boston Richardson Mine, Dolliver Mountain Mine, West Goldbrook Mine, and East Goldbrook Mine which operated between 1892 and 1912. Headquartered in Rouyn-Noranda, Quebec, the company was founded in 1987 and raised funds for exploration work, in part, by issuing stocks traded on the Montreal Stock Exchange and then the TSX Venture Exchange. It became a subsidiary of Anaconda Mining Inc. after Anaconda acquired the company in a stock swap deal in 2017.
Layne Christensen Company is a U.S.-based global water management, construction and drilling company. The company has two divisions, which are Water Resources-Mineral Services and Inline.
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.