Exploration diamond drilling

Technique of geological core drilling

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Drilling rig capable of both diamond and reverse circulation drilling.

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.

History

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Diamond core drill bits

Rodolphe Leschot is often cited as being the inventor of the first core bit in .[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 s, General Electric pioneered the technology of polycrystalline diamond compacts (PDCs) as a replacement for natural diamonds in drill bits.[2]

Diamond drilling

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Illustration showing drill core

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]

Core extraction

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Extraction of core using triple-tube

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.

Tube sizes

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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]

Drill cores 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

References

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- First American Spring-Pole well

The first properly documented spring-pole well was drilled by David and Joseph Ruffner in on the Kanawha River, West Virginia. A depth of 58 feet - 17.5 meters was achieved, and this was a precursor to spring-pole drilling in the oil industry.

 

- First Gas well in America

In , the first well specifically intended to obtain natural gas was dug in Fredonia, New York, by William Hart. Hart dug a 27 foot - 9 meter well to obtain a larger flow of gas to the surface. Hart is regarded by many as the 'father of natural gas' in America.

 

- First 4-legged derrick

A patent for the first four-legged derrick was given to L. Disbrow, originally in and then elaborated on in . The structure consisted of legs made of square timber wood. The girts were mortised and inserted into the wooden legs with keys so the structure could be dismantled.

 

- America's first Oil Well

Kentucky drillers were drilling an exploratory well for salt brine. They hit an oil well instead. The pressure of the gas and oil underneath the surface forced an enormous geyser into the air. This was noted to be America&#;s first oil well.

 

- - Grenelle Well

The Grenelle well in France was reached by a dry rotary auger method. It was drilled to 1,771 feet and took eight years.

 

- Drilling Jars Patented

William Morris, a spring pole driller in West Virginia, patented drilling jars.

 

- Water Circulation used in Drilling

The French engineer Pierre-Pascal Fauvelle was the first to utilize water circulation in drilling. Using the new method, he drilled 560 feet in 23 days.

 

-  Invention of the Rotary Drill

The first rotary drill was invented by Englishman Robert Beart.

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- Mechanical Percussion Drill Invented

J.J. Couch invented the first mechanical percussion drill, which he later perfected with the help of fellow inventor J.W. Fowle. Steam was admitted alternately to each end of a cylinder. The drill was thrown like a lance at the rock on the forward stroke, caught and then drawn back on the reverse stroke, and then thrown again. It was the first drill that did not depend on gravity. It went to work on the Hoosac Tunnel project, which bored a passage for trains through hills near North Adams, Massachusetts.

 

- Reverse Circulation Drilling Patented

Bowles patented reverse circulation drilling.

 

- Drake Well

Edwin Drake and George Bissell successfully use a drilling rig on a commercial well drilled specifically to produce oil in Pennsylvania. The reached a depth of 69 feet - 23 meters.

 

- Steam-powered Oil Derrick

J.C. Rathbone drilled a discovery well to 140 feet using a steam engine on the banks of the Great Kanawha River in the Charleston, W.Va., area. The well produced about 100 barrels of oil a day.

 

- Diamond Core Drill Invented

The diamond core drill was invented by Rodolphe Leschot, a French engineer. Leschot patented the device in the United States.

 

- Sweeny's Rotary Rig

On January 2, , Peter Sweeney of New York City was granted a U.S. patent for a drilling system with many innovative technologies. Sweeny&#;s rotary rig design, which improved upon an British patent by Robert Beart, applied rotary drilling&#;s &#;peculiar construction particularly adapted for boring deep wells.&#;

 

- Compressed air Burleigh Drill

Charles Burleigh, John W. Brooks, and Stephen F. Gates patented a mechanical drill meant to be used on the Hoosac tunnel: the compressed air Burleigh drill. The tunnel spurred several innovations in drilling technology, including the earlier Couch/Fowle drill.

 

- Roberts Torpedo Invented

Edward A. L. Roberts developed the first torpedo and submitted a patent application in November . Roberts, an American Civil War veteran, came up with the concept of using water to "tamp" the resulting explosion, after watching Confederate artillery rounds explode in a canal at the Battle of Fredericksburg. Roberts developed his first torpedoes in and .

 

- Ingersoll Rock Drill

Simon Ingersoll received a patent for a rock drill on a tripod mount. The drill was designed for mining and tunneling. It enabled the operator to drill at virtually any angle. He formed Ingersoll Rock Drill to capitalize on this invention, a company that is a precursor to Ingersoll-Rand.

 

- Diamond Drill Patented

John Vivian was given the first U.S. patent for a diamond drill. While other drills before its time bored holes through a succession of blows, this invention allowed the core to remain intact. This made it very valuable for prospectors.

 

- Bucyrus-Erie Company Founded

Founded in Bucyrus, Ohio. The company later became famous in the drilling industry as Bucyrus-Erie, a maker of cable-tool rigs.

 

- First well drilled with rotary equipment

Brothers M.C. and C.E. Baker drilled the first well with rotary equipment. They pumped water with a windmill.

 

- Sargeant Drill Company Founded

Henry C. Sergeant started the Sergeant Drill Company to manufacture a rock drill he had invented, which included using compressed air to move the drill&#;s piston onto the steel in a hammering motion. Sergeant Drill Company later merged with Ingersoll Rock Drill to form Ingersoll-Sergeant Drill Company.

 

- First Electric Drill Patented

Arthur James Arnot patented the world's first electric drill on Aug. 20. The new device was designed for rock drilling, primarily in coal mines.

 

- First Diamond Core Hole

Edmund J. Longyear drilled the first diamond core hole in the Mesabi Iron Range in northern Minnesota. He formed a contract diamond drilling company to serve the rapidly growing U.S. iron ore mining and steel industry.

 

- Flexible Shafts for Drilling Bits

John Smalley Campbell issued the first U.S. patent for the use of flexible shafts to rotate drilling bits. The patent was for dental applications, but was broad enough to cover larger scales, such as those used now in horizontal oil wells.

 

- Invention of the Calyx Drill

The Calyx Drill was developed by Australian, Francis Davis, around . This tool, used for drilling large holes in rock, was adopted in many countries around the world as it reduced waste and was highly economical.

 

- Rotary method used in Oil Well Drilling

By the Baker brothers were using their rotary method for oilwell drilling, in the Corsicana field of Navarro County, Texas.

 

- Invention of water-cooled Drill

John G. Leyner invented a water-cooled drill that helped dampen dust raised in drilling.

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