Natural gas is extracted, on and offshore, through drilling. Geologists study sites and select those most likely to produce natural gas. Though technology has increased the likelihood of a successful well, drilling is still a gamble. A drilling strategy is formed based on the characteristics of the site. Productive wells are drilled and others abandoned.
Water, sand and chemicals injected into the subsurface increases its permeability. Chemicals increase friction and protect the well from bacteria and rust. Mixed with water, these chemicals form the fracturing fluid, for which sand is the conduit. The well itself is lined with concrete and steel to keep this mixture from seeping into groundwater. Hydraulic wells can be drilled either horizontally or vertically. Vertical wells are cheaper but do more damage to the environment. Horizontal wells compensate for their higher cost with higher extraction rates from single wells.
Percussion drilling is an old method still used for shallow wells. A heavy metal bit is hoisted above the location of a well and dropped until it strikes oil. Advancements, such as steam power, doubled the depths that bits could penetrate. Old percussion sites did not have lined well walls. Mud gathered at the bottom and required clearing. Despite its simple approach, it laid the foundation for more advanced drilling. However, it can not compete with rotary drilling in terms of productivity.
Rotary drilling allows further exploration of oil deposits that are wider than deep. These deposits must be tapped by pipelines that can move horizontally as far as one mile. Seismic imaging developed alongside rotary drilling and provided proper preparation of drilling strategies. Pipelines can be aimed with directional drilling toward the most concentrated portions of deposits. Horizontal drilling is also more environmentally safe. Vertical drilling causes more damage to the surface, including buildings and roads.
Rigs and Platforms
Offshore drilling employs a variety of rigs and platforms required to provide a solid surface above a body of water from which to properly drill. Shallow water drilling solutions include barges and jack-up rigs, which remain above the surface, and submersible rigs, which touch the ocean floor. Deep-water solutions include platforms attached to the sea floor forming fixed rigs using different pilings for different depths. Fixed platform wells are also costly and rely on the recovery of a large amount of natural gas.