A rotary drill is a type of drill commonly used for boring holes and wells, particularly useful to the oil-drilling industry. Its use is not limited to the oil industry, however; it is also used for boring holes in construction and mining projects. It is distinct in that it employs a sharp, rotational drill bit to bite its way through the earth’s crust and because it is able to tackle the hardest and most challenging of formations. [1]
The basic system of a rotary drill comprises prime movers, hoisting equipment, rotating equipment, and circulation equipment, all components that are crucial to its operation.
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[edit] History
Rotary drills can be traced back to a rotary type of bamboo drill that was used in China as early as 3,000 B.C., and also in Egypt. The first concept of a rotary drill was Leonardo da Vinci’s, in the 1500s. The design type was similar to the rotary drills of today. Though the conception of the rotary drill came early, it was not put into common practice until the late 1800s and early 1900s.
In fact, an Englishman by the name of Robert Beart invented the first rotary drill in 1845. Beart’s rotary drill was designed such that the drill was dug into the ground and made rotational by a mule or other animal walking in circles. [2]
The 1900s brought the beginning of the oil boom. Rotary drilling was well suited for this, as evidenced by its use in the Spindletop well in Texas in 1901. Captain Anthony Lucas and Patillo Higgins operated the rotary drill on this well and it proved successful in drilling. By 1925, the rotary drill was becoming more and more common, and manufacturers began making improvements to the original design. In this year, the rotary drill was fitted with a diesel engine.
[edit] Advantages Over Other Drills
Rotary drilling for oil and petroleum became increasingly popular as new technology was adopted. It became well liked within the industry because of its ability to drill deep holes through the hardest rock formations. Another advantage of using the rotary drill as opposed to other types of drills, such as the cable drill, was that rotary drills could produce holes of a smaller diameter, which extended equally all the way down to the bottom of the hole.
When it came to removing cuttings and debris, cable drills were turned off and removed from the hole to do so, but the rotary drill, comprising a circulation system, was able to remove cuttings without ceasing operation. Rotary drills also worked well with cement foundations and could handle the continuous unloading of cement as it drilled. [3]
[edit] Features
The rotary drill comprises a basic system of prime movers, hoisting equipment, rotating equipment, and circulating equipment.
[edit] Hoisting Equipment
The hoisting equipment on a rotary drill is used to raise and lower the tool in and out of the hole. It comprises a derrick, a tower-like structure that sits on a mast above the hole. In addition to acting as a support for the derrick, it also supports the cables and pulleys that are responsible for raising and lowering the tool. Attached to the hoisting equipment is a swivel that provides support for the weight of the drill string. Hoisting equipment is a crucial component because it stabilizes a drill that can weigh well over 1,000 pounds (454 kg).
[edit] Rotating Equipment
This is a piece of equipment that receives power from the prime mover and uses this power to rotate the drill bit. The power is consistent and enables the rotating equipment to continue uninterrupted.
[edit] Circulation System
The circulation system cools and lubricates the drill while it is continuously rotating. This prevents the drill from over-heating. It also removes rock and debris created by the drill bit. In addition, the circulation system coats the walls of the well with a mud-type cake to help facilitate circulation.
[edit] Prime Mover
The prime mover is responsible for transmitting power to the rotating and hoisting equipment, and the circulation system.
[edit] Drill Bit
The rotary system is not complete without a special rotary drill bit. Located at the bottom of the drill string, the bit is a hard, sharp tip that penetrates rock and drills through it by breaking and dislodging rock. There are many different types of drill bits suited for different types of formations. Below are the three main types of drill bits:
- A blade or drag bit comprises steel and tungsten carbide. The combination produces a shearing action suitable for unconsolidated formations.
- A steel tooth rotary bit was invented in the 1900s and was one of the most common drill bit types for all drilling projects. The long-tooth roller cone bit was used for softer formations while the short-toothed bit was considered best for hard ones. The result is a cutting action produced through crushing and chipping. Lately, tungsten carbide has been used for a more abrasive result, instead of the usual granite or quartzite.
- A polycrystalline diamond compact bit consists of polycrystalline diamond inserts attached to carbide inserts. They are suitable for the hardest formations, more effective and 40 to 50 times harder than traditional steel bits.
[edit] Types
[edit] How it Works
The rotary drill exerts downward pressure into the hole as the drill bit is spinning, dislodging, and breaking away rock. While this operation is proceeding, the hoisting equipment is managing and supporting the drill by raising and lowering it as needed. The circulation system is removing debris and cuttings, while also lubricating the hole and making it easier for the drill bit to effectively penetrate a hole. [4]
[edit] Common Manufacturers/Brands
- Atlas Copco
- Creighton Rock Drill
- Furkura Rock Drill
- Gardner-Denver
- Ingersoll Rand
- Lunzen
- Reed
- Tamrock
- Terex
[edit]
References
- ↑ Harris, Frank. Ground Engineering Equipment Methods. McGraw-Hill: New York: 1983.
- ↑ Drilling Methods. Well Drilling School. 2008-10-14.
- ↑ Drilling Methods. Well Drilling School. 2008-10-14.
- ↑ Drilling Methods. Well Drilling School. 2008-10-14.
