Method of sidetracking by opening two windows in the columns of different diameters

While drilling from a vertical shaft the orientation of the diverter is carried out with the help of a magnetometer, leaving an interval of 18 m from the casing. The length of the milled interval could be reduced if a gyroscopic compass is used to orient the BHA. The open borehole section is covered with a strong cement sheath. To avoid magnetic interference, the bridge is drilled down to a depth of 6 m above the bottom of the open interval. A disadvantage of the full casing section milling method is an increased requirement on the strength of the cement bridge for drilling, and the difficulty in finding the head of the lower casing section if it needs to be drilled through after the sidetrack. In many cases, the mechanical drilling rate is limited by the conditions for removing cuttings, and for a horizontal section, the problem of removing cuttings becomes even more complicated. The design of modern milling tools is meant to produce small swarf that does not form clusters and is easily removed from the hole. During milling, it is preferable to flush the well with polymer drilling muds rather than clay muds. Hydrocarbon-based muds are not recommended for milling at all. An alternative to milling the entire casing cross-section is to make windows in the casing. This requires the installation of an oriented whipstock and the milling of the window in several stages. After a whipstock is positioned in the required direction, the stud connecting it with a milling machine of the first stage is cut off. On this basis, the paper proposes a method of sidetracking.