Field testing CO2 foams, conformance control gels for EOR - Part 3

摘要

The previous segment in this series indicated that a multitude of promising lab-scale studies of CO2 foams for conformance and/or mobility control have been published. Thirteen field tests of CO2 foams occurred between the mid-1980s and mid-1990s. This decade-long experiment provided valuable insights into the technical strengths and weaknesses of CO2 foams for mobility and conformance control in sandstone and carbonate formations to recover additional oil. The majority of field tests involved the use of alternating slugs of aqueous surfactant solution and CO2 (surfactant-alternating-gas, or SAG). Although much of the lab-scale work on CO2 foams was related to mobility control, 11 of the 13 field trials were designed primarily to achieve near-wellbore conformance control due to many factors: shorter duration of the conformance control treatment, higher likelihood that the CO2 would mix thoroughly with the previously injected surfactant slug in high-permeability zones near the wellbore, possible deleterious effects of high oil saturation on foam stability during mobility control tests, and ability to generate strong near-wellbore foams by increasing the surfactant concentration.