A Laboratory Study of CO2 Interactions
Research has shown that fracturing with CO2 can increase well productivity and recovery factors. But how is CO2 interacting with reservoir formations to produce those results? Are there any adverse reactions between CO2 and organic material? A recent laboratory study investigated CO2 interactions within various cores from the Duvernay, Montney and Wolfcamp formations to dig deeper into changes in permeability. The results would determine if the use of CO2 as a fracturing or Enhanced Oil Recovery (EOR) fluid would be favorable in these formations.
During the SPE Canada Unconventional Resources Conference on March 13, 2018, SPE paper 189800 was released with the findings. To determine the mineralogy of the cores, X-ray diffraction was used on each sample and the Total Organic Carbon (TOC) was determined with a Source Rock Analyzer (SRA). Using a pressure pulse-decay technique, the permeability was measured for helium baseline permeability, subcritical CO2 permeability after a 48 hour soak and again for helium regain permeability.
Results indicate that the permeability to helium is generally recovered after CO2 soaking stages for tight-sand samples (e.g., Montney) and may be elevated for some samples enriched in organic matter and clay minerals (e.g., Wolfcamp). Overall, the study shows favorable interaction between rock and organic material and CO2, which supports the use of CO2 as a fracturing or EOR fluid in these three reservoirs.
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