A Study for Using CO₂ To Enhance Natural Gas Recovery from Tight Reservoirs

A comprehensive study is presented on the interfacial behavior of all participating phases in a scenario of using carbon dioxide (CO 2 ) to enhance the recovery of natural gas in tight sandstone reservoirs. Natural gas condensate is contacted with CO 2 at an increasing pressure to determine the minimum miscibility pressure (MMP) by the vanishing interfacial tension method. Close to the MMP at a higher temperature, some compounds of the mixture are extracted, leaving a heavy oil fraction that remains immiscible. As the second reservoir liquid, formation water is extracted by CO 2 from a tight sandstone sample and subsequently applied as a sessile drop for assessment of the wetting behavior inside the reservoir in the presence of injected CO 2 . The contact angle has been observed to increase with increasing CO 2 pressure. It has been further observed that the water contact angle on a gas shale increased with increasing CO 2 pressure more rapidly. The results suggest that CO 2 could clear the gas flow path blocked by water and gas condensate. As a consequence, the recovery of natural gas would increase. This could also create greater potential for CO 2 storage in gas-depleted reservoirs.