Improvement of the image analysis method for quantifying low-polarity oily stains on fabric

The stain quantification method using image analysis is excellent because it is non-destructive and applicable for non-uniformly adhered stains. The technique is difficult to adapt to colorless stains, but can be used by coloring the stains. However, low-polarity oils have poor compatibility even with oil-soluble dyes, and it is difficult to accurately quantify them from the appearance. The purpose of this paper is to examine the quantification of low-polarity oily stains by three methods: (1) search for a dye tracer suitable for non-polar oil; (2) use an ultraviolet (UV) image by mixing a fluorescent tracer; and (3) use an UV image using a model stain that absorbs UV rays. In the experiment, the soiled samples were prepared by dropping soiling liquid on a cotton fabric and washing with a tergotometer, and the cleaning efficiency was determined from the image obtained with a digital camera. Results showed that Elixa Red 348 with lower polarity than Sudan IV and Oil Red O is superior as a dye tracer for non-polar oil. In the fluorescence tracer method, the sum of G values (Σ G) in the red, green, blue signals of the image data can be used, but the decrease in fluorescence over time is a problem in the case of pyrene. It was also found that UV-absorbing stains such as alkylbenzene can be quantified from UV images by utilizing the slight fluorescence coloration of cotton fabric generated under 254 nm UV irradiation. The future potential of image analysis methods for quantifying non-polar oily stains was suggested.

Response of Non-Polar Oil Component on Low Salinity Effect in Carbonate Reservoirs: Adhesion Force Measurement Using Atomic Force Microscopy

While the effect of polar-oil component on oil-brine-carbonate system wettability has been extensively investigated, there has been little quantitative analysis of the effect of non-polar components on system wettability, in particular as a function of pH. In this context, we measured the contact angle of non-polar oil on calcite surface in the presence of 10,000 ppm NaCl at pH values of 6.5, 9.5 and 11. We also measured the adhesion of non-polar oil group (–CH3) and calcite using atomic force microscopy (AFM) under the same conditions of contact angle measurements. Furthermore, to gain a deeper understanding, we performed zeta potential measurements of the non-polar oil-brine and brine-calcite interfaces, and calculated the total disjoining pressure. Our results show that the contact angle decreases from 125° to 78° with an increase in pH from 6.5 to 11. AFM measurements show that the adhesion force decreases with increasing pH. Zeta potential results indicate that an increase in pH would change the zeta potential of the non-polar oil-brine and calcite-brine interfaces towards more negative values, resulting in an increase of electrical double layer forces. The total disjoining pressure and results of AFM adhesion tests predict the same trend, showing that adhesion forces decrease with increasing pH. Our results show that the pH increase during low-salinity waterflooding in carbonate reservoirs would lift off non-polar components, thereby lowering residual oil saturation. This physiochemical process can even occur in reservoirs with low concentration of polar components in crude oils.

Low-salinity waterflooding in non-polar oil

Enhanced oil recovery by low-salinity waterflooding is considered to have positive results only when polar components exist in oil. This study shows that low-salinity brine can result in incremental recovery for non-polar oil through fines-assisted waterflooding. Despite the traditional view of fines migration that it should be avoided because of its detrimental effect on reservoir permeability, this work shows that permeability decline is a main mechanism in the low-salinity effect on non-polar oil. Laboratory coreflood tests were performed on a clay-rich Berea outcrop core and a clean sand core to investigate the effect of clay migration when the core is saturated with non-polar oil. The results show that fines migration reduces residual saturation by 18%. In addition, a decrease in the water volume production was observed due to the decrease in water relative permeability.