## 2 Development of the Radial Drilling Technology  
Radial drilling represents an unconventional technique employing a small-diameter steel conduit, such as a capillary or a coiled tubing, to bore a hole with a diameter ranging from 50 to 60 mm and a length of up to 200 m. This process utilizes a high-energy fluid stream propelled through a nozzle at elevated pressures [6; 8; 9]. Economically, the radial drilling technology proves effective for drilling horizontal channels extending up to 900 m from an existing vertical borehole. It becomes particularly valuable when other tertiary methods prove ineffective or to enhance the efficiency of existing Enhanced Oil Recovery (EOR) methods [6; 10; 11; 12]. The concept of processing materials with a high-pressure water jet dates back to the 1960s, with applications ranging from cutting metals, rocks in mining, and ceramics, to cutting plastics in shipbuilding and the automotive industry. These techniques vary in water pressure, incorporating abrasive agents to aid the process. As high-pressure technology advanced, covering more industries, attempts were made in the late 1960s to introduce this technique into the oil industry. However, technological limitations and capabilities at that time temporarily hindered its development. In subsequent years, scientific studies by [PERSON] and others contributed to the refinement of this drilling technique. [PERSON] [3] introduced a borehole drilling system with a 0.1 m diameter and lengths ranging from 30.48 to 60.96 m, utilizing a hydroturbine and achieving drilling speeds of 30.5-60.9 mm/s. [PERSON] [13] employed a 0.032 m diameter coiled tubing, resulting in boreholes ranging from 0.87 to 52.2 m in length after passing through a casing window, resulting in a tenfold increase in oil production. Presently, the successful drilling of multiple radial wells from the main well using a drum-wound conductor [14] demonstrates their contribution to increased reservoir production and improved reservoir ratios, while minimizing damage to the near-wellbore zone. The expense associated with drilling and reaching a depth of 2500 m using conventional methods, such as rotary methods with bottom and top drives, surpasses EUR 7-8 million. Notably, standard-diameter directional drilling accounts for at least 40% of this cost. For planned new wells, a pivotal challenge in the decision-making process lies in selecting the spatial trajectory for the horizontal part. The efficacy of applying the directional drilling technology hinges on the accuracy of the design and execution of the assumed well trajectory [15; 16]. Considering the anisotropy of reservoirs' physical properties, opting for an optimal trajectory is crucial to ensuring an efficient inflow of hydrocarbons. The radial wells proposed in this article, drilled with a rotary hydraulic nozzle, offer a solution that enables the intensification of production and enhances the connection between the well and the reservoir. Conversely, when dealing with wells exhibiting low or zero productivity, a decision must be made regarding either decommissioning them or undertaking costly intensification procedures. Hydraulic radial boreholes will help develop the production from reservoirs without drilling new horizontal wells in the reservoir zone. The solution to the challenges outlined and the growing demand lies in a technology that enables the drilling of multiple small-diameter radial lateral wells from an existing drilled and cased well [17]. With the cost of radial drillings (four boreholes) from a single production zone, covering a range of up to 200 m from the main vertical hole, being less than EUR 600,000, this technology facilitates the acquisition of valuable reservoir data. This, in turn, mitigates the risk of erroneous decisions and unnecessary financial losses amounting to millions of euros. The proposed technology not only provides a cost-effective approach but also allows for the redevelopment of old and decommissioned deposits with a depletion rate of 30-40%.