There is no indication on the surface of a soil that reveals the presence of a natural gas or oil deposit underground. However, the deep knowledge of soil structure that geologists and geophysicists have accumulated over years of experience allows them to quickly dismiss certain places and focus their studies on those with certain topographic characteristics.
However, when the presence of a natural gas pocket is detected, data collection must continue to decide whether or not to exploit the deposit: the depth at which it is located, its approximate volume, the characteristics of the strata located above etc The pocket is accessed by means of a probe installed in a metallic tower-shaped structure, its chemical composition and gas pressure are also determined and, if it is definitely considered that the deposit will be profitable, the well is put into operation.
When the gas is not mixed with oil, the exploitation works are simplified since the product sprouts naturally and it is not necessary to raise it mechanically to the surface. Sometimes, water may have accumulated in the wells, so it must be pumped out to maintain optimal production.
Exploration and extraction works include activities that may be disturbing to fauna and flora. The environmental impact of these works, however, is limited in time since prevention and correction measures are adopted that restore the environment to its natural state. When a natural gas field is considered exhausted, the platforms are dismantled, removed and the well sealed, or they are used as natural gas storage.
Well drilling rigs are installed both on land and in the sea. The towers located in the sea are installed on a platform anchored to the bottom. The surface equipment consists of a structure that supports the drilling rig, which is about 40 m high, and an apparatus that moves the drilling column as it is deepened. The method used to carry out the perforation is the rotation method, which has replaced the percussion method used in the past.