## 2 Factors Impacting the Intensity of Hydroabrasive Wear of the Pumping Stages of the ESP
Most of the methods used for protection of ESPs against hydroabrasive wear are aimed at reduction in the concentration and size of particles of mechanical impurities passing through the pumping stages in the fluid flow, and increasing resistance of the pumping stage's materials to abrasive wear. In addition, changing the shape of particles of mechanical impurities (increasing their spherical shape factor and roundness) entering an ESP, for example, by means of preliminary mechanical action, reduces their abrasiveness and wear capacity. Analysis of the Protection Methods for ESPs Producing Well Fluid with High Content of Mechanical Impurities  
Methods for protecting ESPs operating under conditions of high content of mechanical impurities in the well fluid are traditionally divided into technological and technical approaches [28; 29; 30; 31]. The first group of methods includes measures associated with the limitation of formation fluid withdrawal from production wells, transition to the continuous operation mode of the ESP unit, and reduction in the rate of work of reservoir pressure maintenance systems. Thus, the probability of abrasive particles being lifted by the well fluid flow and the probability of mechanical impurities passing through the ESP is decreased. Necessary attention is paid to the selection of well-killing fluids' compositions, corrosion control of borehole equipment, and analysis of chemical compatibility of formation products with fluids injected into the well and formation [1]. The implementation of technological methods to protect ESPs against mechanical impurities is expensive, complicated, and generally leads to the reduction in production well productivity. Technical methods to protect ESPs against the harmful effects of mechanical impurities include the use of submersible pumps in abrasion-resistant designs [32] and the use of pre-wired devices. Wear-resistant pumping stages are made from high-strength materials. The designs of guide apparatus, impellers, thrust washers, and interstage seals are adapted to abrasive particles. These designs are often based on the implicit abrasion resistance of the parts of an ESP, and have wide prospects for use and improvement. However, the cost of abrasion-resistant ESP units is 1.5-2 times higher than units of a conventional design [15; 16]. The pre-wired devices used to protect ESPs from mechanical impurities are divided into separators and filters. These are installed in the well in order to clean the sand, propping agent, and other mechanical impurities from the reservoir and have two main functions: to protect the pump from solid particles and to create a minimum hydraulic resistance at the pump inlet. Separators of mechanical impurities are installed in wells under ESP submersible motors and provide separation of solid particles from fluid flow by gravitational or centrifugal forces. A common disadvantage of these devices is the change in efficiency (value of mechanical impurities' separation coefficient) depending on the well flow rate, formation fluid properties, and mechanical impurities. ESP filters are divided according to their operating principle into surface and volumetric filters, i.e., slotted or wire-line and disk filters, respectively. The efficiency of the filters is virtually independent of changes in borehole conditions. Currently, the slotted filters are the most widely used, and are characterized by a simple design, high maintainability, and low cost [4; 25; 27]. Figure 3: The graph for visual determination of values of roundness coefficients \(K_{r}\) and spherical shape factors \(K_{s}\) of solid particles of mechanical impurities. The disadvantage of filters is their low dirt capacity, which causes ESP failures due to supply failures in case of clogging of filter elements. The existing methods of filter cleaning and permeability recovery directly in well conditions are inefficient, complicated, and have significant financial expenses, thus limiting their application.