We briefly discuss some of the borehole drill methods and applications used in mining operations.
What is Borehole Mining?
A borehole is drilled for extraction of minerals through a process that uses high-pressure water. The water jets make it possible to drill into hard rock, whether in an open-pit floor, underground mine space, conventional land surface, or from a vessel in the sea or on a lake. The first step is to drill to the desired depth from the land surface. The actual borehole mining then takes place at the selected point. The next step is to lower a casing column into the well with the shoe of the casing situated above the top boundary of the ore body production. The third step involves the lowering of the borehole mining tool into the drill well.
The method of mining requires less capital outlay than many other mining methods and it makes it possible to work in otherwise inaccessible areas that are too dangerous for conventional mining methods to be used. It also has a low environmental footprint and allows for better mobility when it comes to changing mine drill locations. More selectivity can be applied, meaning less wastage and higher profits. The method is frequently used for mining minerals like gold, uranium, diamonds, coal, and quartz sand. It is also used for oil and gas drilling.
When holes or wells are drilled for the purpose of evaluating the content of the hole as retrieved, it is called exploration drilling. The mine houses utilise this type of drilling to retrieve mineral samples of a specific location for the purpose of evaluating the samples to determine whether the quality and quantity of a specific mineral are sufficient to make mining at the location viable. Reverse circulation is one method used and it entails retrieval of the drill cuttings, using drill rods that are used for the transport path of the cuttings to the surface. A hammer drives the tungsten steel drill point into the rock or soil. With this method, depths of up to 500 m can be drilled. The retrieved material is dry. Odex and Tricone systems are used in reverse-circulation drilling.
With Odex, the hammer drill bit fits at the end of the steel casing and the hammer is used for crushing the material, which is blown up into the casing where the retrieved cuttings are transported to the surface. The system is used when there is a risk of rock collapsing in the drill area. This is a time-consuming and sometimes very expensive method, but it is often the only type of method that can be used to prevent rockfalls. The Tricone system is used for water, oil, and petroleum retrieval. It entails roller cone bits grouped into a drill bit that rotates into the rock formation.
When is Core Drilling Used?
It is a suitable method when the drill bits must be protected and when only a small sample of content has to be retrieved. Core drilling is normally used when faster exploration drilling is needed. It can also be used in the construction sector for drilling pipe holes.
It is a method used for the drilling of non-vertical boreholes for applications such as:
- Horizontal directional drilling used for installation of utilities.
- Directional boring.
- Oil-directional drilling
- Coalbed methane drilling
When are Boreholes or Wells Drilled Directionally?
The method is applied when there is a need to increase the length of the exposed part through a reservoir; when drilling takes place at the bottom part of a reservoir-limiting fault, to make it possible for completion of various productive sands at the highest stratigraphic ends; and to make it possible to group more well-heads to minimise surface area disturbance. It can also be used when it is not possible, or extremely complicated, to drill into a reservoir vertically. The borehole drilling method is furthermore used for opening a hole or well that can be used to reduce the pressure of a well, in order to minimise the risk of a blowout.
Speak to our consultants to help you determine the best method for your particular application requirements. We offer a wide range of borehole drilling services to industries in all sectors of the economy.