How Steam Injection works in Enhanced Oil Recovery

 

Our world today relies heavily on oil as its primary fuel source. With global oil consumption nearing 100 million barrels of oil per day, how can such a demand be met?  There are three phases of oil production: primary, secondary, and tertiary. Primary recovery phase involves the removal of hydrocarbons that float to the top. In the second phase, gas and water are injected to push the oil to the surface with as much as 60% to 80% of the oil remaining in the well. Enhanced oil recovery (EOR) comes in at the tertiary phase and can help extricate as much as 30% of the OOIP (original oil in place).  

Steam Injection and Thermal EOR

EOR involves the use of materials not commonly found in a given reservoir to maximize oil production.  Thermal recovery using injected steam, a method used commercially since the 1960s, is one of the most commonly used methods used by production teams, accounting for over 50% of the market. Thermal recovery is accomplished when the reservoir is heated, reducing oil viscosity.  Used mostly in shallow reservoirs that contain heavy crude oil, the injection of steam heats the formation's oil to reduce its viscosity and evaporating some of it to make it more mobile. With the viscosity lessened, surface tension is reduced while the permeability of the oil is increased which improves the seepage conditions of the reservoir. The vaporization of the oil allows it freely flow through the reservoir. It also results in better oil formation once it's condensed.   

Two Steam Injection Methods

There are two categories of steam injection: steam flooding and cyclic steam stimulation.  When using steam flooding, both injection and production wells are used and they are different from each other. Injection wells are used for the introduction of the steam, which is directed toward the oil to dislodge it while it's being heated to decrease its viscosity.  Continuity is necessary when using steam flooding in a formation so the steam can drive the oil in the direction of the production well. While it costs more to steam flood than it does to use cyclic steaming because more steam is needed, a larger amount of oil is recovered. Both methods can be used in fields where connectivity is good with cyclic stimulation used first followed by steam flooding.  When cyclic steam stimulation is used the same well is used for both oil production and the injection of steam. Steam is injected first over a period of time ranging from a couple of weeks to a couple of months. The oil immediately surrounding the injection well is heated using convective heating which lowers its viscosity.  Once the oil's viscosity is at the desired level, the injection of steam is halted to allow the heat to be redistributed evenly within the formation. More oil is recovered at this stage and the well can be used for production until the well's temperature drops and the oil viscosity rises again. Once that's complete, a new round of steam is injected to begin heating the reservoir.  

Environmentally Friendly

Of all of the enhanced oil recovery methods used in oil production, injecting steam is one of the most environmentally friendly. Fewer complications are encountered when this method is used. The steam itself doesn't pose any threat to the environment because it condenses back to water and leaves no pollution.  

An Effective Way to Meet the Demand for Oil

Thermal recovery through the injection of steam is one of the more popular methods of enhanced oil recovery in use today. Not only does it produce as much as 30% of original oil in place, it doesn't threaten the environment the way other methods can. The method can be used in a variety of countries as a result, even where strict restrictions are in place.