Scientists from Egyptian Petroleum Research Institute have tested a new technology for enhancing oil recovery at mature fields, which uses carbon dioxide with a biopolymer based on xanthan gum, a well-known food-grade thickening agent. The results have shown that this combination yields significantly higher oil recovery than conventional water injection or even the sole use of CO₂.
It is well known that modern water flooding methods cannot fully extract oil from the reservoir. This is largely due to the properties of water: it moves through the most permeable channels without covering a significant portion of the formation. As a result, up to a third of the initial oil reserves can remain in the rock. The injection of carbon dioxide can partially solve this problem. CO₂ dissolves in oil, reducing its viscosity and facilitating its movement through the pores of the rock. Furthermore, when coming in contact with gas, the oil expands in volume, which also improves its displacement. However, this method has a major drawback: carbon dioxide is too mobile. It quickly breaks through the formation through isolated channels and fails to evenly distribute across the oil field.
Seeking to solve this problem, the researchers have proposed using xanthan gum, a well-known food thickener commonly used in the production of sauces, desserts and dairy products. In an oil reservoir, it serves a different function: making the injected fluid more viscous and slowing down the movement of gas. This allows the flow to be distributed more evenly as CO₂ begins to penetrate previously inaccessible areas of the rock.
In order to test this idea, the scientists conducted a series of experiments on model sandstone formations saturated with oil. They compared several scenarios: conventional flooding, injection solely with CO₂, injection solely with the polymer, and combinations in which the gas and the polymer were injected in succession. Xanthan gum concentration in the solution ranged from 1 gram per liter to 2.5 grams per liter.
Laboratory tests showed that conventional water injection made it possible to recover about 70% of oil. The sole use of carbon dioxide increased the recovery to 83.3%, while the sole use of the polymer raised it to 81.3%. However, the best result was achieved by combining the two methods. When CO₂ was injected into the reservoir first, followed by a xanthan gum solution at a concentration of 1.5 grams per liter, the oil recovery rate reached 94.3%. In other words, the technology made it possible to additionally recover almost a quarter of oil compared to conventional water flooding.
The scientists also performed a computer simulation of the technology at a real field. Calculations confirmed that combined injection of CO₂ and the polymer makes it possible to maintain longer-term production stability, reduce premature water and gas breakthrough, and ensure a more uniform oil displacement from the reservoir.
