Researchers from China University of Petroleum prepared a modified silicone polymer as a carbon dioxide thickener
Increasing greenhouse effect has led to much focus on carbon use to reduce CO2 emissions. According to the U.S. Energy Information Industry (EIA), the U.S. produced 5.14 billion metric tons of carbon-dioxide equivalent greenhouse gas (GHG) emissions in 2017. CO2 fracturing technology has high potential in protecting the environment in comparison to hydraulic fracturing fluid as it causes minimal damage to the reservoir. The low permeability reservoir are damaged in hydraulic fracturing stimulation due to the blockage of chemical additives and water. Therefore, several studies are focused on improving the viscosity of CO2.
Now, a team of researchers from China University of Petroleum synthesized Epoxy Ether-based Polydimethylsiloxane (EEPDMS). The team also assessed the impact of temperature, pressure, shear rate and EEPDMS content on the viscosity of CO2. To describe the varying thickening performance of EEPDMS at different conditions, the team also suggested a mesh structure model. The shale reservoir model was constructed with a low permeability to compare the fracturing difference between pure CO2 and thickened CO2. The team found that EEPDMS demonstrated a significant effect on the viscosity of CO2. More microscopic mesh structure were generated when EEPDMS was added with CO2 compared with the pure CO2. However, the team found inconsistent effect of temperature, pressure, shear rate and EEPDMS content on the viscosity of CO2. The CO2 viscosity decreased with increase in temperature or shear rate.
However, CO2 viscosity maintained a significant surge with increase in pressure or EEPDMS content. Moreover, the behavior was appropriate to pure CO2 and thicken CO2. The team used mesh structure theory to explain the reasons of viscosity changes by several aspects. The shale model was used to define fracturing impact of the thickened liquid CO2. In further study, the team plans to recapitulate the design principle of CO2 thickener, which can aid in developing a thickener with an efficient thickening performance. The research was published in the journal MDPI Polymers on March 21, 2019.
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