Locating Oil and Recovering It
Geologists are responsible for oil discovery. They use various techniques to discover oil; they study the area for conditions that would indicate the presence of trapped oil. Finding the right source rock, reservoir rock, etc will lead to the presence of oil. Satellite images too are used in figuring out areas where oil could be present, in addition to study of surface rocks and terrain. They use many techniques including use of sensitive gravity meters, which indicates very tiny changes in the gravitational fields of earth, which could indicate presence of flowing oil. Seismology techniques too are used where shock waves are made to pass through rock layers, and the reflected waves are studied to check for presence of oil. Thus once geologists make a discovery, preparations are made to extract oil through drilling.
Before drilling for oil can commence, the site where drilling is to be carried out needs to be prepared. The kinds of preparation that is done is building access roads to the location of drilling, finding a source of water by drilling - if no natural sources are available in the vicinity, pits are created to dispose off the rock cuttings that get extricated during the drilling. The pits are covered in plastic for preventing any environmental problems. If the site is an ecologically sensitive one then the extractions will need to be ferried away from the site.
Before the actual hole is drilled, a cellar is dug; this acts as a space for the workers to move around and also to put away the equipment, etc. Before the actual rig is put in place, a smaller hole is dug with a smaller drill truck and this part of the hole dug is wider and shallower. After these preparations are complete the rig is brought in.
The oil rig has many components like the power system, the mechanical system, rotating equipment, casing, circulation system, Derrick, and blowout preventer.
The power system of the rig is made of a diesel engine, or electrical generator, and acts as the main source of power supply.
The mechanical system of the rig is driven by electrical motors, and it has the hoisting system - for lifting heavy loads, and the turntable – which is part of the drilling apparatus.
The rotating equipment is used for rotary drilling.
The casing is made of large diameter casing pipes that line the drilled hole, and prevents the hole from collapsing, and also helps in circulation of mud.
The circulation system pumps in mud to lift rock cuttings from the drill bit to the surface.
The Derrick supports the drilling apparatus, and its length helps add new sections of drill pipe to the drilling apparatus as the drilling progresses.
The blowout preventer is a high pressure valve that prevents a blowout.
The drilling progresses, and once the presence of oil is detected, the well needs to be prepared for oil extraction. Acid is pumped in, which clears the channels and leads the oil to the well. Proppants too are pumped in and hydrofracking is done. Once the oil has started flowing into the well, the rig is removed and equipment for oil extraction is put in place.