Bubble size distribution and stability of CO₂ microbubbles for enhanced oil recovery: effect of polymer, surfactant and salt concentrations

Abstract

Fluids incorporating carbon dioxide (CO2) microbubbles have been utilized to promote enhanced oil recovery from hydrocarbon reservoirs. The performance of such fluids in porous media is greatly affected by both the bubble size and stability. On this basis, the present study evaluated the effects of varying the concentrations of a xanthan gum (XG) polymer, a surfactant (sodium dodecyl sulfate: SDS) and sodium chloride (NaCl) on both the stability and bubble size distribution (BSD) of CO2 microbubbles. CO2 microbubble dispersions were prepared using a high-speed homogenizer in conjunction with the diffusion of gaseous CO2 through aqueous solutions. The stability of each dispersion was ascertained using a drainage test, while the BSD was determined by optical microscopy and fitted to either normal, log-normal or Weibull functions. The results showed that a Weibull distribution gave the most accurate fit for all experimental data. Increases in either the SDS or XG polymer concentration were found to decrease the microbubble size.However, these same changes increased the microbubble stability as a consequence of structural enhancement. The addition of NaCl up to a concentration of 10 g/L (10g/1000g) decreased the average bubble size by approximately 2.7%. Stability was also reduced as the NaCl concentration was increased because of the gravitational effect and coalescence.

Applying Imaging Technique to Investigate Effects of Solute Concentrations and Gas Injection Rates on Gas Bubble Generation

“…Salt has been one of the most popular solutes to control bubble size in mineral flotation [74]. The effect of SDS surfactant concentration has also been investigated by Nguyen Hai Le et al [30] to promote enhanced oil recovery from hydrocarbon reservoirs. Also, both solutes were available in our laboratory.…”

“…In addition to the aforementioned applications, the bubbly flow has also drawn research attention from petroleum engineering [17][18][19][20][21][22] and geoscience [23][24][25][26][27][28]. For example, Nguyen Hai Le et al [29] and Nguyen Hai Le et al [30] most recently reviewed the enhanced oil recovery in sealing highly permeable layers or fractures by injecting carbon dioxide (CO 2 ) microbubbles as a displacement surrogate. Due to the blocking performance depending on bubble size distribution (BSD) and stability, Nguyen Hai Le et al [30] investigated the effects of salt, surfactant, and polymer on the BSD and stability of CO 2 microbubbles.…”

“…For example, Nguyen Hai Le et al [29] and Nguyen Hai Le et al [30] most recently reviewed the enhanced oil recovery in sealing highly permeable layers or fractures by injecting carbon dioxide (CO 2 ) microbubbles as a displacement surrogate. Due to the blocking performance depending on bubble size distribution (BSD) and stability, Nguyen Hai Le et al [30] investigated the effects of salt, surfactant, and polymer on the BSD and stability of CO 2 microbubbles. On the other hand, based on the soil gas bubbly flow theory proposed by Etiope and Martinelli [31], Ma et al [32] studied discrete bubbly flow in water-saturated transparent soil, later followed up by a more comprehensive study by Ma et al [26].…”

“…The intrusive methods include electroresistivity [43][44][45][46], ultrasound reflection [47][48][49][50][51], and optical techniques [52][53][54][55][56][57][58], which inevitably cause instrumented interference on bubble samples. In comparison to those approaches, the imaging technique as a nonintrusive method has been primarily adopted for both academic and industry bubble size measurement due to lower cost and ease of operation [5,9,15,16,28,30,59]. Nevertheless, the densely binding bubbles in the observing chamber bring challenges for image analysis.…”

“…According to Puleo et al [64], Moruzzi and Reali [65], Shepard et al [16], and Nguyen Hai Le et al [30], BSD is dependent on several influential factors: hydraulic pressure in the viewing chamber, the temperature of water solution, solute concentration (surface tension), pH of the aqueous environment, type of injected gas, type of gas bubble generator, gas injection rate, etc. Even though most previous works have investigated multiple factors on BSD, they separately studied and analyzed a single factor of many individually influencing BSD [5,8,9,15,16,30,64,66,67]. By far, the significance of combining factors on BSD has not often been investigated.…”