The subject of the research is a down-hole drill string assembly with a steered downhole motor-deflector used in drilling of oil and gas wells. This assembly operates in two modes: steered and non-steered with the drill string rotation.
To improve the borehole quality and drilling cost performance it is necessary to reduce to a minimum the directional drilling which can be achieved through increasing the reliable ensuring the required intensity of the borehole deviation and enhancing the assembly steerability. To achieve this aim a technique is proposed for prediction of the assembly geometry parameters using the pattern allowing for contacting of its four supporting elements with the borehole bottom wall the path of which is a circle arc. The geometry parameters of the designed assemblies with drilling bits of diameters 215.9 and 220.7 mm and the downhole motor angularity of 1-1.5° can provide the borehole path with mean and major radii of curvature (200-600 m and more).
The results obtained enable to select the assembly design using permanent and movable centralizers as well as with a minimum negative effect on assembly’s manoeuvrability in a borehole and on the conditions of the borehole cleaning due to a reduced diameter of supporting-centralizing elements and their being manufactured as decentralizes (pads) on the downhole motor case.
References
1. Povalikhin A.S., Kalinin A.G., Bastrikov S.N., Solodkiy K.M., Burenie naklonnykh, gorizontal’nykh i mnogozaboynykh skvazhin (Directional, horizontal and multihole drilling), Moscow: Publ. of TsentLitNefteGaz, 2011, 645 p.
2. Prokhorenko V.V., Technology of horizontal wells and sidetracks drilling using a motor-deflector (In Russ.), Stroitel'stvo neftyanykh i gazovykh skvazhin na sushe i na more, 2007, no. 11, pp. 2–4.
3. Grechin E.G., Pashkov E.V., Regulation of deformation and strain of the bottom-hole assembly, starting the motor diverter, by means of centralizers (In Russ.), Stroitel'stvo neftyanykh i gazovykh skvazhin na sushe i na more, 2015, no. 5, pp. 18–21.
