## 5 Drilling Nozzles Using a Continuous High-Pressure Liquid Stream  
Currently, the jet nozzle drilling technology is widely employed for cutting, hydraulic jet drilling, or pipeline cleaning due to its capability to concentrate energy effectively in the jet [29]. The general equipment and tool scheme for creating radial holes using a high-energy liquid jet flowing through a nozzle at high pressure is depicted in Figure 5. This solution is commonly encountered in various forms and is extensively documented in \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Test Conditions,** & **Jetting Velocity,** & **Width of the Crack,** & **Length of the Crack,** & **Stream Power,** & **Specific Energy per Unit of Crack Volume,** \\  & **MPa** & **cm/s** & **cm** & **cm** & **kW** & **Crack Volume,** \\  & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & \multicolumn{1}{c}{} & **J/cm\({}^{2}\)** \\ \hline \multirow{4}{*}{\
\begin{tabular}{c} Berea \\ Sandstone \\ \end{tabular} } & ATM \({}^{*}\) & 9.5 & 0.87 & 5.48 & 71.8 & 1390 \\ \cline{2-6}  & 3.45 & 9.45 & 2.30 & 3.18 & 71.8 & 2390 \\ \cline{2-6}  & 6.90 & 9.45 & 1.67 & 2.95 & 71.8 & 2580 \\ \cline{2-6}  & 13.80 & 9.45 & 1.27 & 3.02 & 71.8 & 2520 \\ \cline{2-6}  & 20.70 & 9.45 & 1.43 & 1.91 & 71.8 & 3980 \\ \hline \multirow{4}{*}{
\begin{tabular}{c} Indiana \\ Limestone \\ \end{tabular} } & ATM \({}^{*}\) & 9.45 & 1.43 & 0.40 & 71.8 & 19,000 \\ \cline{2-6}  & 3.45 & 9.45 & 1.59 & 0.33 & 71.8 & 23,000 \\ \cline{1-1} \cline{2-6}  & 6.90 & 9.45 & 1.19 & 0.33 & 71.8 & 23,000 \\ \cline{1-1} \cline{2-6}  & 20.70 & 9.45 & 1.19 & 0.41 & 71.8 & 16,200 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Data for cavitation hydraulic jet drilling [27]. Figure 4: (**a**) The effect of the distance of the nozzle from the surface to be worked on the eroding process by a cavitation jet, (**b**) the rate of cavitation erosion. numerous publications and some patents [4; 8; 9; 11; 21; 30; 31; 32]. While individual solutions may vary in technical details, the fundamental approach to drilling radial boreholes remains rooted in hydraulic jet drilling techniques. In the process of drilling such radial boreholes, the sections are typically horizontal, ranging in length from 100 to 300 m, with diameters falling between 40 and 60 mm. The considerable variation in the horizontal section lengths is attributed to specific requirements for the drainage zone length. The varying diameter of the radial boreholes is due to the nature of hydraulic radial drilling using a rotary nozzle, the structure of the wellbore medium, and various technological factors and parameters related to the reservoir rock. Figure 6 shows an enlarged diagram illustrating the nozzle going through the deflector. [PERSON] conducted fracture-cutting tests in six different types of rocks [33], employing 0.58 mm diameter jets operating at pressures as high as 172 MPa. The results showed that the depth of the fracture in these rocks experienced a decrease ranging from 60% to 80% when the penetration rate was increased within the range from 4.6 to 152 m/min, as illustrated in Figure 7.  
[PERSON] [34] conducted a series of fracture-cutting tests involving a 0.5 mm diameter water jet moved across Indiana limestone at ROP ranging from 10.1 to 40.64 cm/s, as presented in Tables 2 and 3. These tests were executed at pressures as high as 1100 MPa. The data obtained from these experiments revealed that both the cracks-cutting specific energy and the specific energy decreased as the jet pressure decreased. This observation suggests that jets exhibit greater efficiency at lower pressures [34; 35; 36]. Figure 5: Scheme of drilling radial boreholes with an ultrashort angle of curvature [33]. Figure 6: Equipment of borehole hydraulic jet drilling techniques [33]. Additionally, when the ROP was increased from 10 to 40 cm/s, the cracks became narrower (0.2 cm versus 0.31 cm) and slightly shallower.