Most oil shales are fine-grained sedimentary rocks containing relatively large amounts of organic matter from which significant amounts of shale oil and combustible gas can be extracted by destructive distillation. One of the largest known locations is the oil shale locked in the...
Tar sands can be often strip mined. Typically two tons of tar sand will yield one barrel of oil. A typical tar sand contains sand grains with a water envelope, covered by a bitumen film that may contain 70% oil. Various fine particles...
Very Heavy crude are hydrocarbons with an API grade of about 15 or below. The most extreme heavy crude currently extracted are Venezuelan 8 API crude e.g. in eastern Venezuela (Orinoco basin). If the reservoir temperature is high enough, the crude will flow from the reservoir....
The descriptions above are valid for conventional oil and gas sources. As demand increases, prices soar and new conventional resources become harder to find, production of oil and gas from unconventional sources become more attractive. These unconventional sources include very heavy crudes, oil sands, oil shale, gas...
Production wells are free flowing or lifted. A free flowing oil well has enough downhole pressure to reach a suitable wellhead production pressure and maintain an acceptable well-flow. If the formation pressure is too low, and water or gas injection cannot maintain pressure...
Plunger lift is normally used on low pressure gas wells with some condensate, oil or water, or high gas ratio oil wells. In this case the well flow conditions can be so that liquid starts to collect downhole and eventually blocks gas so...
Gas Lift injects gas into the well flow. The downhole reservoir pressure falls off to the wellhead due to the counter pressure from weight of the oil column in the tubing. Thus a 150 MPa reservoir pressure at 1600 meters will fall to...
Downhole pump insert the whole pumping mechanism into the well. In modern installations, an Electrical Submerged Pump (ESP) is inserted into the well. Here the whole assembly consisting of a long narrow motor and a multi phase pump, such as a PCP (progressive...
Sucker Rod Pumps, also called Donkey pumps or beam pumps, are the most common artificial-lift system used in land-based operations. A motor drives a reciprocating beam, connected to a polished rod passing into the tubing via a stuffing box. The sucker rod continues...
Wells are also divided into production and injection wells. The former is for production of oil and gas, injection wells is drilled to inject gas or water into the reservoir. The purpose of injection is to maintain overall and hydrostatic reservoir pressure and...
Subsea wells are essentially the same as dry completion wells. However, mechanically they are placed in a Subsea structure (template) that allows the wells to be drilled and serviced remotely from the surface, and protects from damage e.g. from trawlers. The wellhead is...
Wellheads can be Dry or Subsea completion. Dry Completion means that the well is onshore on the topside structure on an offshore installation. Subsea wellheads are located under water on a special sea bed template. The wellhead consists of the pieces of equipment...