Steam injection oil recovery is one of the most common ways of oil extraction, that has been in use since at least the 1960s (Dong et al. 1191). The process is implemented during the tertiary stage of enhanced oil recovery, which occurs during the exploitation of an oil well after the natural pressure pushing oil onto the surface eventually runs out. EOR is implemented to extract up to 30% of the available oil in place, and steam injection is the primary method of doing so (Dong et al. 1192).
Steam injection is used primarily to reduce the viscosity of oil by heating it up. It is used in shallow oilfields where the viscosity of the oil is high, which increases both the density and weight of the oil, making it hard to extract through pressure. As oil is heated up, its mobility increases and some of it becomes vaporized (Dong et al. 1194). As a result, the permeability of oil increases, surface tension decreases, and reservoir seepage conditions improves, allowing for more of it to be extracted through the well. The collection of oil vapors followed by its condensation enables achieving a greater quality of oil at the end of the process.
The primary two methods of steam injection oil recovery are cyclic steam stimulation (CSS) and steam flooding. CSS suggests repetitive cycles of steam injection, soaking, and oil production (Nwidee et al. 26). During the first stage of the process, hot steam (300-340 Celsius) is injected into a well for several weeks, which allows the heat to gradually rise in the formation. Once the malleability and mobility of the oil are increased, the oil is pumped through the well.
The process is repeated once the production values start to decline. This method offers better excavation values but is expensive. EOR is limited to oil found at a depth of more than 800 meters (Nwidee et al. 28). The average injection pressure is at 900 psi (Nwidee et al. 29). Examples of facilities cyclic EOR include the reservoirs of San Joaquin Valley in California, and the oil wells in Alberta, Canada (Samsonov 36).
The second method, called oil flooding, involves the use of steam injection wells in some places, while others are used in oil production (Nwidee et al. 19). It is useful for large oil basins that are interconnected. Thus, the pressure and temperature coming from the steam wells push the oil towards others used in production. The two mechanisms utilized in this operation are the heating mechanism, meant to reduce oil viscosity, and the flooding mechanism, which displaces oil from its original location, pushing it towards the extraction oil wells (Nwidee et al. 20). This method requires more effort and steam when compared to CSS, but tends to result in larger volumes of extraction. Some oil wells in Alberta are known to be using this type of steam injection in their efforts.
The method is very lucrative and universal, which is why it has been in use for so long. Nevertheless, it faces three major challenges. The first challenge is the potentially destructive nature of pressurized steam, which could damage the structure of the underground oil wells (Samsonov 38). The second issue is the economic expensiveness of the method. One of the reasons why shoal oil is considered more costly when compared with others is because of the shortcomings of the steam injection method (Samsonov 39). Finally, the cooling of vapors injected creates water, which needs to be separated from the oil itself, creating additional issues and costs for the producer.
Dong, Xiaohu, et al. “Enhanced Oil Recovery Techniques for Heavy Oil and Oilsands Reservoirs After Steam Injection.” Applied Energy, vol. 239, 2019, pp. 1190-1211.
Nwidee, Lezorgia Nekabari, et al. “EOR Processes, Opportunities and Technological Advancements.” Chemical Enhanced Oil Recovery (cEOR)-a Practical Overview, 2016, pp. 2-52.
Samsonov, Sergey V. “Short-and long-term ground deformation due to cyclic steam stimulation in Alberta, Canada, measured with interferometric radar.” The Leading Edge, vol. 36, no. 1, 2017, pp. 36-42.