A research team from the Chemistry Department at Lomonosov Moscow State University jointly with NefteKhimSintez has presented a new technology for enhancing the extraction of hard-to-recover oil reserves. The newly-developed solution is called ChemField-Oil. The researchers estimate that its application will allow oil companies to increase the extraction of crude oil by an average of 10–17% without the need to drastically modify the existing field infrastructure.
The relevance of this technology has to do with a fundamental problem inherent to conventional waterflooding. With standard reservoir pressure maintenance, a significant portion of the oil remains untapped, reaching 50% of the original reserves in some cases. Moreover, oil distribution across the reservoir can be extremely uneven. About 30% of the oil is made up of capillary-trapped and film-like oil, which is stuck in small pores due to strong capillary forces. Another 21% is concentrated in stagnant zones with low hydrodynamic activity, where fluid movement is virtually nonexistent. The rest of the reserves remain in low-permeability layers which are not covered by the displacement front, or get localized in isolated lenses and impermeable barriers, which plainly cannot be reached via standard production methods.
Instead of mechanical actions, the Russian researchers have proposed solving this problem via physical and chemical processes in the reservoir. A special composition is added to water during injection; the composition gets adsorbed at the oil-water interface, significantly reducing the interfacial tension. As a result, the capillary forces holding oil in the pores weaken, and water starts to displace oil more effectively, even from finely porous zones of the reservoir.
At the same time, the composition changes the wettability of the rock. Most oil reservoirs are oil-wet or mixed-wet, which causes the oil to stick to the mineral surface. The new reagent makes the rock more water-saturated, facilitating the detachment of oil droplets and their entrainment in the flow. An additional effect is achieved by the formation of microemulsions, mobile systems that can move through the pore space, increasing oil mobility.
After being injected via an injection well, reagent-containing water gets distributed in the bottom-hole area under pressure. First, the composition passes through the most permeable channels, such as fractures and highly permeable layers, ensuring the rapid distribution of the active components, after which it starts working in zones with residual oil. There, the oil is mobilized and sent to production wells along with water.
The optimal reagent concentration for continuous injection into water with pressure maintenance is just 0.05–0.1%, which makes the technology economically attractive. As a result, incremental oil production reaches 8–17% of the baseline level, and reserve recovery rates can rise by 1.3–1.5 times. Operating costs can be further reduced by cutting the water injection volumes and increasing the oil recovery factor.
The researchers suggest that the most promising application for the new reagent could be in terrigenous reservoirs with a permeability of 50–500 mD, porosity of 15–30%, reservoir temperature of 50–80°C, residual oil saturation of over 40% and water cut of 70–90%.
Next, the research team is going to test the technology at real oil fields.
ChemField-Oil is the second major solution developed by Lomonosov Moscow State University and NPP NefteKhimSintez. Earlier, this team developed the THIONOL reagent for the safe and cost-effective removal of hydrogen sulfide and mercaptans from oil.
