# Experimental Study and Numerical Simulation of W/O Emulsion in Developing Heavy Oil Reservoirs
###### Abstract  
In the process of waterflooding development of heavy oil, W/O emulsion has a strong ability to improve the mobility ratio and block the high-permeability layer, which can effectively improve the sweep coefficient and enhance oil recovery. In this paper, the stability and droplet size distribution of emulsions under different conditions were studied by taking heavy oil and formation water from Jimusar Oilfield in Xinjiang as samples. On this basis, double-pipe core flooding experiments were carried out to study the shut-off ability and oil displacement efficiency of W/O emulsion, and then a numerical simulation was carried out. The results show that oil and water can be completely emulsified when the stirring speed is higher than 4000 r/min. A stable emulsion can be formed when the experimental temperature is lower than 60 \({}^{\circ}\)C. A lower water cut results in a more stable emulsion. The emulsion is difficult to stabilize after the salinity exceeds 10,000 mg/L. When the pH value is about 7, the stability of the emulsion is the worst. With the increase in stirring speed, the increase in temperature, and the decrease in water content and salinity, the emulsion droplet size range is relatively concentrated, and the average particle size is smaller. In heterogeneous reservoirs, the permeability of different percolation channels is quite different, such that the displacement fluid only percolates along the high-permeability channel and cannot drive oil effectively. The results of displacement experiments show that the emulsion with a water cut of 60% has high viscosity and obvious sweep ability, but its stability is very poor; the effect is opposite when the water cut is less than 40%. The shut-off ability of W/O emulsion disappears gradually when the permeability contrast is more than 5.92. The research results are of great significance for improving oil recovery in heterogeneous heavy oil reservoirs. heavy oil reservoir; W/O emulsion; numerical simulation; emulsion stability; shut-off capacity 202  
an O/W emulsion with oil as the dispersion phase and water as the dispersion medium, and the other is a W/O emulsion with water as the dispersion phase and oil as the dispersion medium [3]. In oilfield development, 95% of crude oil is produced in the form of an emulsion [4]. Because oil and water phases are subjected to various shearing actions in the process of production and transportation, these shearing actions can make the active components in crude oil (asphaltene, colloid, etc.) gradually adsorb on the oil-water interface and emulsify oil and water to form emulsions [5]. In the reservoir, moderate emulsification of oil and water can increase the viscosity of the displacement phase and produce the Jamin effect in the narrow pore throat, thus improving the mobility ratio and expanding the sweep volume [6; 7]. Therefore, the formation of a crude oil emulsion with proper stability in the process of waterflooding is of great significance to improve the mobility ratio and expand the sweep efficiency. An important criterion to measure the emulsion is the stability of the emulsion [8]. It is generally believed that, if the emulsion is more stable, the premise is that the interfacial tension between oil and water must be lower, which can be achieved by adding surfactant, whereby the stability of the emulsion is affected by the interfacial tension [9]. However, [PERSON] and others also drew another important conclusion. By studying the surfactants (such as colloid and asphaltene) in Beihai crude oil, according to the corresponding relationship between the interfacial pressure of the emulsion formed by this substance and the stability of the emulsion [10], it was concluded that not only do the properties and structure of the emulsifier itself have a significant effect on the stability of the emulsion, but the interfacial pressure is also the most important factor influencing the strength of the interfacial film [11].