###### Abstract
There is the possibility of casing the drilled channels with filters (for a terrigenous reservoir). The areas of application of this technology include the following:  
* An alternative to hydraulic fracturing. It is applicable for wells with a close location of an oil-water contact/gas-oil contact, where hydraulic fracturing is unsafe. Directional radial drilling of channels minimizes the risks of breakthrough to a water bearing bed or a gas cap. Figure 1: Network of branched channels of drilled using TS Perfobore. * Involvement in the production of overlying formations: drilling a network of radial channels in multi-layer reservoirs with a high sectional structure in order to involve several isolated interlayers in the development. * Combination with remedial cementing, which is applicable for wells with a cross flow behind the casing. After conducting an aggressive remedial cementing to isolate the cross flow behind the casing, that is, drilling channels along a predetermined trajectory to restore a link with the formation and minimize the risk of further breakthrough of the cross flow behind the casing. * Combination with hydraulic fracturing. Drilling channels provides mining stress and sets the direction of a hydraulic fracture. * Injection of oxidants or other reagents into the drilled channels to intensify high-viscosity oil extraction. * Drilling channels to increase the injection capacity of wells. * Technology applicability criterion:
* Casing diameter is from 139.7 mm to 178 mm. * The intensity of the increase in curvature is not more than 3 degree per 10 m.
* In the operating interval, it is necessary to have a cement ring of satisfactory quality behind the production string. * There should be no casing centralizers in the channel drilling interval. * The frequency of holes in the previously made perforation is not more than 60 holes per a linear meter. * The temperature at the bottom of the well is not more than 150 \({}^{\circ}\)C.
* The productive formation thickness is more than 3 m.  
The primary functions of the Perfobore system is productive interval penetration at the completion of well construction or major repairs to the well to establish high-quality hydraulics for a perfect link between the formation and the well. The Perfobore technical system is intended for the construction of a network of branched channels with small diameters and curvature radii along a predicted trajectory The implementation of this technology has become possible through the use of specially designed small-sized equipment; for example, bore bit diameters that are from 58 to 75 mm and housing elements (body diameter, D\({}_{\text{b}}\)) of positive displacement motors (PDM) that have diameters of 43 to 55 mm. Moreover, the equipment is designed in such a way as to provide the drilling of channels with a constant set of inclinations. As a result of numerous bench (Figure 2) and field tests, it was found that the rate of an inclination should be from 8 to 10 degrees per meter. This is especially important in the case of the gravity method of reservoir development, in which formation fluid moves to the bottom of producing wells under the influence of its own gravity [15]. Figure 2: Bench tests of TS while drilling a channel with curvature radius of 7.7 m.  
During the construction of multihole channels, significant bending moments act on the bottom-hole assembly (BHA), the magnitudes of which are comparable to the rotation moment of a small-sized PDM [16; 17]. As a result of numerous analytical studies, and bench and field tests, the authors selected the required bending stiffness of the BHA and BHA design. It was also found that, for effective channel construction, a PDM must have a high rotation moment along with the bending stiffness of the assembly [18]. Since the technology uses a small-sized PDM operating at a low flow rate (up to 2 L/sec), cutting transport to the surface is impossible when using salt or fresh water.