# Assessment of Changes in the Abrasiveness of Solid Particles in Hydraulic Mixtures Pumped with ESPs
## 1 Introduction  
Well-oil production in the fields of the countries of the Eurasian region is carried out with widespread use of electric submersible pump units (ESP units). These units are characterized with high energy efficiency in operation of wells with medium and high rates (more than 40 m\({}^{3}\)/day). The introduction of intermittent well-operation technology in oil fields and mastery of the production of small-sized ESP units makes it possible to expand the area of use of these pumping units to wells with low flow rates. As a result, for example, in the fields of the Urals and Western Siberia, more than 60% of oil wells are equipped with ESP units. These plants produce more than 80% of oil in Russia [1; 2].  
ESP units are often operated under difficult conditions, which can lead to high risks of premature unit failure. Elimination of ESP-unit failures entails significant financial and time costs for the oil producer, since each emergency stop requires expensive tripping operations [3; 4].  
A significant part of ESP-unit emergency failures (over 30% of the total number) is caused by hydroabrasive wear of electric submersible pump units and connected devices [5]. In the most severe situations, the impact of abrasive particles contained in pumped well fluid is accompanied by cutting of the guide vanes and pump housings (Figure 1), followed by submersible electric motors and parts of the ESP unit falling to the bottom of the well [6]. Elimination of such failures removes the need to perform technically complex and laborious fishing operations [4; 7].  
Especially unfavorable operating conditions for ESP units are characterized with wells that are put into operation after hydraulic fracturing. Removal of loose proppant during development of such wells reduces the operating time of electric submersible pumps to several days [8; 9; 10].  
Several works [11; 12; 13] are devoted to the study of the process of hydroabrasive wear of ESP components. Attention in the process of ESP design is mainly paid to selection of wear-resistant materials of the working stages, placement and improvement of bearing-support designs, development of wear-resistant designs for guiding apparatuses and protection from cutting. The peculiarities of the hydroabrasive-wear process of interstage seals, for example, remain insufficiently investigated.  
Known methods of calculation of the hydroabrasive-wear rate of interstage seals for ESP installations do not take into account changes in the sizes and shapes of the impurity particles contained in a pumped hydroabrasive mixture as they pass through the working stages of the pump. They also do not take into account the nonuniformity of seal wear depending on the location in the pumping section. In this case, the rate of seal hydroabrasive wear differs significantly, as not only do values of pressure drop on seals differ but also abrasiveness of mechanical-impurity changes relative to the initial.  
The specified has caused urgency of research of an estimation of abrasiveness change for solid particles in hydromechanical mixes pumped with ESP units, with the purpose of development of technical decisions directed toward minimization of consequences of hydroabrasive wear of ESP-unit knots and details.