Extracting oil from underground deposits is a much more complicated process than drilling a well. The underground environment is a difficult place to work. Challenging textures in both the rocks and the deposits limit how the oil flows into the well. Difficult circumstances and a lack of technology meant that in the past, workers were only able to extract about 10% of the available oil when working with underground deposits. Even today, they can only extract 60%.
The extraction process is broken down into three main steps: primary recovery, secondary recovery, and enhanced recovery.
During primary recovery, underground pressure pushes fluids to surface level. Once the pressure drops, pumps and other artificial lift technologies are utilized in an attempt to bring even more of the fluids up to the surface. Sometimes workers also pump oil back down into the well so that it is underneath the remaining oil. When the gas expands, it pushes the oil up to the surface. The gas lift method is primarily used in offshore extraction facilities. This technique alone, however, normally only removes 10% of a deposit’s oil.
Secondary recovery is the method used to extract an additional 20% of resources. During the initial phase of drilling, water is separated from the oil. During secondary recovery, this water is injected back into the formation. This method doesn’t just help extract more oil, but it also helps dispose of wastewater by returning it to its original place.
To get the rest of the oil, the enhanced recovery method is used. There are three techniques used in enhanced recovery. These are thermal recovery, gas injection, and chemical flooding.
Thermal recovery uses steam to improve oil flow. Steam is injected into the formation, and then the heat from the steam helps the oil flow more easily. The increase in pressure also pushes the oil to the surface.
Gas injection is another method. This technique dissolves gasses in the oil such as propane, methane, and CO2. Once the gasses are dissolved, they change the texture of the oil and increase its flow.
The last technique, chemical flooding, involves mixing water with water-soluble polymers. Once combined, the mixture is injected into the formation. The water then pushes the oil from the formation to the well.