Australia (UNSW): A Microfluidics Approach to Enzyme EOR
- Lucas Evangelista
- Mar 22, 2019
- 2 min read
Updated: 8 hours ago
Enzyme Enhanced Oil Recovery (EEOR) has recently been categorized as one of the most effective EOR mechanisms. Laboratory and field studies have reported up to 16% of incremental oil recovery rates. EEOR recovers oil mainly by two main mechanisms: lowering the interfacial tension between brine and oil and altering the wettability on rock grains to a more water-wet condition. Therefore, EEOR would promote mobilization of capillary-trapped oil after regular waterflooding. Since capillary-trapped oil resides at the micro-scale, it is essential to assess EEOR fluid-fluid interaction at the microfluidics scale. To further investigate the ways
in which these enzymes contribute to EOR, an experimental micro-scale approach was developed in which EEOR was analyzed using polydimethylsiloxane (PDMS) microfluidic devices.
The PDMS microfluidics device was based on X-ray micro-CT images of a Bentheimer sandstone with resolution of 4.95 μm. We first compared the IFT reduction capabilities of one class of enzyme (GreenZyme®) and a commercial surfactant (J13131). For GreenZyme concentrations of 0.5, 1.5 and 2 wt%, the IFT values between GreenZyme solution and oil are 4.2, 0.7 and 0.6 mN/m, respectively. Whereas the IFT values for 0.5 wt% surfactant solutions and deionized water are 1.1 and 32 mN/m, respectively.
We then compared the oil recovery of the two systems using the aforementioned sandstone PDMS microfluidics device. Recovery values up to 92% of oil were obtained using GreenZyme. Surfactant and waterflooding on the same PDMS chips had recovery values of 86 and 80%, respectively. This study provides insights and direct visualization of the micro-scale oil recovery mechanisms of EEOR that can be used for design of effective EEOR flooding.
Speed Matters: GreenZyme vs. Surfactant Early in the Flood
Both GreenZyme and the surfactant reached the same 86% recovery at matching 0.5 wt% concentration by the end of the flood — but they didn't get there the same way. At just 1 pore volume injected, 0.5% GreenZyme had already recovered about 82% of oil, while the surfactant had only reached about 72%. That's despite the surfactant having a lower IFT (1.1 mN/m) than 0.5% GreenZyme at that concentration — surfactants are known to react more slowly, which the study points to as the likely explanation for their weaker early performance.
The authors draw a direct conclusion from this: IFT reduction alone is likely not the only reason to select an EOR agent. Since GreenZyme outperformed a lower-IFT surfactant early in the flood, other properties of the enzyme — such as reducing viscosity and/or altering wettability — are probably contributing to its recovery advantage, not just its effect on interfacial tension.
Sources & Credits
Read Full Paper https://www.onepetro.org/conference-paper/SPE-195116-MS
Authors: Maher Rahayyem, Peyman Mostaghimi, Yara A. Alzahid, Amalia Halim, and Ryan T. Armstrong (University of New South Wales UNSW); Lucas Evangelista (BTP GreenZyme).
