From Science Daily:
A proposed recovery technique for oil extraction developed by a Penn State-led research team not only outperforms existing drilling and recovery techniques, but also has the potential to sequester more carbon dioxide in the process.
The team estimated that companies using this new technique would greatly improve oil recovery rates. They developed a model that indicates that the process could extract between 78 and 90 percent of the oil in a reservoir over several decades. Existing drilling techniques in use today extract a maximum of 50 to 60 percent of the estimated total volume of oil before production, and on average, that number is closer to 35 percent. The model uses horizontal drilling, in which wells are drilled up to about 4,000 meters (13,000 feet) underground, parallel to the Earth’s surface, through known oil reservoirs. This differs from vertical drilling techniques, in which wells run perpendicular to the Earth’s surface.
Two wells, organized in a staggered line drive, form the basis of the model — one well in the top of the reservoir to inject supercritical carbon dioxide into the system, and another well at the bottom of the reservoir to extract oil. Carbon dioxide normally behaves like a gas at room temperature and pressure, but when it is pressurized and heated past a certain point — the critical point — it becomes a supercritical fluid, which exhibits liquid density and gas viscosity. When injected at a continuous rate, supercritical carbon dioxide is an excellent solvent that is able to…