## 2 Factors Impacting the Intensity of Hydroabrasive Wear of the Pumping Stages of the ESP
Usually, filter plugging determines the necessity to lift the ESP out of the well in oil production practice [12,33]. Exceptions are the filters equipped with check valves, which are opened when the filter element is clogged. In this case, the fluid flow enters the ESP without purification, together with particles of mechanical impurities, thus bypassing the clogged filter element [15,16]. Analysis of the known methods of protection of working stages of downhole ESPs against hydroabrasion shows the search for cost-effective, efficient, and versatile technical solutions, to provide an increase in the ESP operating time in wells, is complicated by the high content of mechanical impurities in the produced oil. One of the promising directions in solving this problem is the creation of ESP inlet and downhole filters with the ability to clean and restore the permeability of clogged filter elements in the conditions of the well, without lifting the submersible pump unit to the surface. Analysis of the Protection Methods for ESPs Producing Well Fluid with High Content of Mechanical Impurities  
Self-cleaning slotted filters were developed and patented by the authors together with the specialists of \"Novomet-Perm\" JSC (Perm, Russia). These filters provide an increase in ESP operating time when producing well fluid with a high content of mechanical impurities. Figure 4 shows the scheme of a downhole ESP slotted filter with deformable filter element [34]. The slotted filter contains a tube (_1_) with a filtering section (_2_), which is perforated with through holes (_3_) and has stiffening ribs (_4_) on the external surface. Upper (_5_) and lower (_6_) stationary stops are mounted in the form of glasses at the ends of the tube \(1\) with annular gaps between the inner surface of the walls and the outer surface of the tube \(1\). A deformable filter element (_7_) is concentrically placed around the tube (_1_). This filter element (_7_) is made as a coiled wire (_8_), with the slots (_9_) formed between the coils. The filter element (_7_) is placed between the upper fixed stop (_5_) and movable double-sided stop (_10_). The end coils of the spiral wire (_8_) of the filter element (_7_), placed inside the annular gaps, are rigidly connected to the stops (_5_) and (_10_). The double-sided movable stop (_10_) moves axially along the pipe (_1_) via the limiting grooves (_11_), into which the ends of the screws (_12_) are sunk. A resilient element made in the form of a cuff (_13_) with through holes (_14_) is fixed on the lateral surface of the double-sided movable stop (_10_), with the help of screws (_12_). The cuff (_13_) is in contact with the walls of the production tubing (_15_) in the borehole. There is a spring (_16_) between the lower stationary stop (_6_) and the double-sided movable stop (_10_) with the support on their ring pads. The force of the spring _16_ exceeds the elastic deformation of the filter element wire (_7_). The slotted filter together with the submersible pump unit is lowered into the borehole. The borehole fluid containing mechanical impurities flows freely to the surface of the filter element (_7_) through the through holes (_14_) of the cuff (_13_). Passing between the slots (_9_) of the coils of the coiled wire (_8_) of filter element (_7_), the borehole fluid is cleaned and flows inside the tube (_1_) through the holes (_3_) of filtering section (_2_), where it further rises into the borehole pump (not shown on Figure 4). Particles of mechanical impurities, separated from borehole fluid, are deposited on the outer surface of the filter element (_7_), creating \"bridges\" of deposits and reducing its permeability (flow capacity) with time. Periodic cleaning of the filter element 7 is carried out by deformation of the tubing on which the ESP is suspended in the well by changing the pressure at the wellhead. It is known that when the oil-well tubing is filled with well fluid and excessive pressure \(P_{w}\) is created at the wellhead, the oil-well tubing deforms by the value \(\Delta\).