## 3 Results and Discussion  
Samples of WOE were prepared by mixing in the required ratios the samples of oil and associated water for 5 min (700 rpm). The resulting oil-water emulsions were characterized by high aggregate stability, which was explained by the high content of natural surfactants therein. No stratification of the emulsion was observed during the studies. In this work, two types of emulsions were investigated--water in oil and oil in water. The first type of emulsion takes place when its water cut is 60-80% and is characterized by significant viscosity, which increases with an increase in the proportion of water. When a certain water cut called the inversion point is exceeded, the phases are reversed, forming an oil-in-water emulsion. This emulsion is characterized by the dispersion medium being of low viscosity, which explains its lower aggregate stability. The resulting samples heated in the water bath cup at 45 \({}^{\circ}\)C were examined with respect to sludging with constant agitation by the magnetic device at a rate of 500 rpm and a temperature of 5 \({}^{\circ}\)C for the cooling agent in the unit CF-4, for 2 h. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Oil Field, Object** & **\(\bullet\)X\({}_{\text{p}}\), V3 – V4 + Bsh** & **\(\bullet\)Y\({}_{\text{p}}\), T** \\ \hline Volume factor, unit fraction & & 1.092 & 1.016 \\ \hline \multirow{2}{*}{Content\%} & paraffin & 1.92 & 3.72 \\  & Resin and asphaltene & 11.4 & 26.9 \\ \multirow{2}{*}{Density \(\rho_{\text{H}}\), kg/m\({}^{3}\)} & sheeted & 818 & 917 \\  & gas-free & 871 & 918 \\ \multirow{2}{*}{Viscosity, mPa-c} & sheeted & 9.0 & - \\  & gas-free & & 81.9 \\ \hline \hline \end{tabular}  
Associated water taken at the field pumping stations was used for preparing water–oil mixtures in the form of emulsions. The water samples had different densities and mineralization levels (Table 2).  
\end{table} 
Table 1: Physical and chemical characteristics of the oils. Figure 2: Rheological characteristics of crude oil. Each oil or water-oil emulsion's ability to sludge ARPD on the fingers during the investigation was estimated by the coefficient of specific sludging for the oil (SSO) or for the fluid (SSF) according to expressions (1) and (2), respectively:  
\[SSF=\frac{\text{M}_{2}-\text{M}_{1}}{\text{M}_{n}}\cdot 100\% \tag{1}\]  
\[SSO=\frac{\text{M}_{2}-\text{M}_{1}}{\text{M}_{\text{zh}}}\cdot 100\% \tag{2}\]  
where M\({}_{1}\) and M\({}_{2}\) masses of the rod before sedimentation and after the experiment, respectively, g; M\({}_{\text{n}}\) --mass of oil in the test sample, g; M\({}_{\text{zh}}\) --mass of liquid, g.  
For the samples of the dry crude oil, the following values of SSO were derived: <<X>> oil--0.36%; <<Y>> oil--0.33%. As can be seen from the graphs obtained, the change in the LOL index with an increase in the water cut of the emulsion was small. For fluid \"Y\" we can say that there was a minimal decrease in this indicator. In the figures, trend lines are point-by-point averages using theoretical values of the coefficient. For the SSF coefficient, these values were determined via expression 3. When forcing them, all the results of laboratory studies were taken into account. Considering these graphs, it can be noted that the nature of the change in the SSF value for some water samples deviates from this trend line, which is explained by the presence of errors in the operation of this laboratory setup. In the figures, trend lines are point-by-point averages using theoretical values of the coefficient, which is calculated as such:  
\[SSF=\frac{m_{\text{ARPD}}\cdot[\rho_{v}\cdot(1-n_{v})+\rho_{n}\cdot n_{v}]}{ \rho_{n}\cdot\rho_{v}\cdot V_{zh}}\cdot 100\% \tag{3}\]  
where \(m_{\text{ARPD}}=\text{M}_{2}-\text{M}_{1}\). The results of the experimental determination of sludging coefficients are given in Table 3.