## 1 Introduction  
Radial drilling of high-permeability waterjet channels is an unconventional technology for drilling multiple small-diameter radial channels in oil-producing wells by using high-pressure jets of working agent [1]. This technology is characterized as cost efficient [2] but has a number of disadvantages: lack of the possibility to determine and control the trajectory of waterjet channel drilling, lack of knowledge of the best operational and technical parameters to be considered in selecting and operating special equipment. Nevertheless, the technology of radial drilling of waterjet channels can be highly effective in the oil production industry, as it offers a number of undeniable advantages cited in [3]. Consolidation of the results of modern research and technical achievements will soon make it possible to draw an unambiguous conclusion about the high efficiency of practical application of radial drilling technology. Figure 1 shows a schematic diagram of the working principle of the jet drilling. The drilling fluid is fed into the nozzle, which in turn forms the front and rear jets. The main function of the front jets is to destroy the rock and form a hole with a diameter of several feet. The function of the back jets is to increase the pulling force of the nozzle, and they can also enlarge the hole by cleaning the wall of the hole while removing sludge. The process of nozzle movement and rock destruction depends on the balance of the acting forces, or rather on the distribution of volumes and velocity of the front and rear jets. In more detail, the fundamental principles of radial jet drilling and the mechanisms of self-promotion of nozzles through the created channel are discussed in the article [4]. In [5], the authors describe the experience of modeling the process of drilling radial channels in a fractured type of reservoir, which is evaluated as successful further in the study; in particular, the waterjet channel in the fractured type of reservoir connects the existing fractures, thereby improving filtration in the reservoir zone under effect. In addition to the proven efficiency in laboratory conditions, the technology of radial drilling of waterjet channels also shows good results in industrial conditions. For example, [6] presents the results of oil production increase in five target wells by 135% on average. In [3], the technology under consideration was applied at the Tarim gas condensate field (China), where a 200% increase in oil production was obtained. Similar positive effects resulting from the application of radial drilling technology were obtained at such oil fields as Donelson West (USA) [7], Belayim (Egypt) [8], Vakhitovskoye (Russia) [9], etc. Study [10] presents the results of experimental application of waterjet radial drilling technology at three oil producing wells and one gas well in India. As a result of pilot application of the technology, a significant increase in the yield of oil-producing wells was obtained, but there was no effect on the gas well. Study [9] analyzes Russian experience in the application of waterjet radial drilling technology at Vakhitovskoye oil field, where oil yield increased between 1.5-5.0 times in different producing wells. Study [11] aimed at investigating the effect of using an acid compound as a disintegrating agent for carbonate rock. The authors conducted a comparative study using fresh water and an acid compound containing 15% HCl. Based on the obtained photos of the test results, the waterjet channel drilled with fresh water has clearly defined \"rays\" (rock excavations in the form of rays), while when using an acid compound, the space between the rays is partially exposed to destruction which further expands the channel. Studies [12; 13; 14] show that the application of waterjet radial drilling technology is most effective in environments with increased oil viscosity, which typically have stagnant zones in low-permeability areas of the reservoir.