Steam injection (oil industry)
Steam injection is an increasingly common method of extracting heavy crude oil. Used commercially since the 1960s,[1] it is considered an enhanced oil recovery (EOR) method and is the main type of thermal stimulation of oil reservoirs. There are several different forms of the technology, with the two main ones being Cyclic Steam Stimulation and Steam Flooding. Both are most commonly applied to oil reservoirs, which are relatively shallow and which contain crude oils which are very viscous at the temperature of the native underground formation. Steam injection is widely used in the San Joaquin Valley of California (US), the Lake Maracaibo area of Venezuela, and the oil sands of northern Alberta, Canada.[1]
Another contributing factor that enhances oil production during steam injection is related to near-wellbore cleanup. In this case, steam reduces the viscosity that ties paraffins and asphaltenes to the rock surfaces while steam distillation of crude oil light ends creates a small solvent bank that can miscibly remove trapped oil.[2]
Steam flooding[edit]
In a steam flood, sometimes known as a steam drive, some wells are used as steam injection wells and other wells are used for oil production. Two mechanisms are at work to improve the amount of oil recovered. The first is to heat the oil to higher temperatures and to thereby decrease its viscosity so that it more easily flows through the formation toward the producing wells. A second mechanism is the physical displacement employing in a manner similar to water flooding, in which oil is meant to be pushed to the production wells. While more steam is needed for this method than for the cyclic method, it is typically more effective at recovering a larger portion of the oil.
A form of steam flooding that has become popular in the Alberta oil sands is steam assisted gravity drainage (SAGD), in which two horizontal wells are drilled, one a few meters above the other, and steam is injected into the upper one. The intent is to reduce the viscosity of the bitumen to the point where gravity will pull it down into the producing well.
In 2011 Laricina Energy combined solvent injection with steam injection in a process called solvent cyclic steam-assisted gravity drainage (SC-SAGD) (Canadian Association of Petroleum Producers CAPP 2009).[5] Laricina claims that combining solvents with steam reduces the overall steam oil ratio for recovery by 30%.
The alternative to surface generated steam is downhole steam generation that reduces heat loss and generates high-quality steam in the reservoir that allows for more heavy oil and oil sands production at a faster rate. Downhole steam generators were first proposed by the major oil companies in the early 1960s. Over the last 50 years multiple downhole steam technologies have been developed such as the DOE and SANDIA downhole combustion system known as Project Deep Steam that was field tested in Long Beach, CA in 1982, but was a failure. The only downhole steam generator that has proved successful is branded as eSteam.