Minggu, 30 November 2008

Onshore

On-shore is drilling into the Earth in the hopes of uncovering valuable resources is nothing new. In fact, the digging of water and irrigation wells dates back to the beginning of recorded history.
At first, these wells were primarily dug by hand, then by crude stone or wood tools. Metallurgy brought about the use of iron and bronze tools to delve beneath the Earth's surface, and innovations led to more efficient ways of removing debris from the newly dug hole. The first recorded instance of the practice of 'drilling' holes in the ground came about around 600 B.C., when the Chinese developed a technique of repeatedly pounding bamboo shoots capped with metal bits into the ground. This crude technology was the first appearance of what is now known as 'percussion drilling'; a method of drilling that is still in use today. Much advancement has been made since these first bamboo drilling implements, with the realization of the value and increased demand for subsurface hydrocarbons. This section will cover the basics of modern onshore natural gas drilling practices.
There are two main types of onshore drilling. Percussion, or 'cable tool' drilling, consists of raising and dropping a heavy metal bit into the ground, effectively punching a hole down through the Earth. Cable tool drilling is usually used for shallow, low pressure formations. The second drilling method is known as rotary drilling, and consists of a sharp, rotating metal bit used to drill through the Earth's crust. This type of drilling is used primarily for deeper wells that may be under high downhole pressure.

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