Exploration drilling is a procedure in which several test holes are drilled for the purpose of evaluating the contents of the ground in a particular area. It is conducted to find out whether or not materials of value are present, and to assess the quality of those materials. There are a number of industries which use exploration drilling in their work, sometimes with their own drilling crews, and sometimes through companies which provide for-hire drilling services.
One common reason for exploration drilling to be done is in mineral exploration. Once a potential site is identified, exploration drilling can be used to determine whether or not the site has materials of interest, ranging from metal ores to diamonds, and to assess the quality and quantity of those materials. This is done by sinking a drill bit which takes a core sample into the ground; the core sample is extracted and analyzed.
In the early stages of exploration drilling, several test holes can be dug for core samples which cover a broad area. Once the value of the site is confirmed, additional holes can be drilled and people can learn more about the quality of the site. The company must determine whether exploiting the site will generate profits which outweigh the costs of drilling and the ongoing costs of maintaining the site once it is active. A site with potentially poor yields could be too costly to invest in, leading the company to pull out.
The oil industry also utilizes exploration drilling to probe suspected petroleum deposits. Samples from the drill are analyzed to determine the quality of the crude oil, while geologists work on estimates of how much oil may be available at the site. People are sometimes surprised to learn that crude oil does in fact come in ranges of quality which dictate how much it can fetch on the open market, making analysis of oil deposits at a site critical.
Geologists may use exploration drilling to learn more about geologic strata, without the specific goal of exploiting mineral resources. Core samples can provide a great deal of information about a site's geological composition and history. These samples can also be taken from deposits of ice and mud to collect layers of deposited data which provides information about the climate; shifting pollen counts can indicate changing weather, for example, while rises in deposits of certain chemicals can sometimes be linked with geologic or human activity.