Minimizing stick-slip while drilling

摘要

According to the invention, a method for designing a rotary drill bit for drilling a cavity in a medium is disclosed. The method may include determining a characteristic of a drillstring with which the rotary drill bit is coupled. The method may also include determining an initial number of groups of cutters for the rotary drill bit, where each group of cutters includes a plurality of cutters substantially aligned along a different radius of the drilling face. The method may moreover include determining a characteristic of the medium relative to a characteristic of the cutters. The method may additionally include determining a characteristic of a rotational motion source used to rotate the rotary drill bit. The method may further include determining the angles of pitch between each of the groups of cutters to minimize an amount of sticking or slipping of the bit in the medium during a drilling operation.

主权项

1. A rotary drill bit for drilling a cavity in a medium, wherein the rotary drill bit comprises:
a bit body, wherein the bit body comprises: a distal end having a drilling face; and a proximal end, having a rotational power source coupling mechanism; and a plurality of cutters coupled with the drilling face of the bit body, wherein the plurality of cutters comprises at least six groups of cutters, wherein each group of cutters is substantially aligned along a different radius of the drilling face; and wherein the azimuthal distribution of said groups of cutters is non-symmetric around the axis of the drilling face and wherein: the radius along which the second group of cutters is substantially aligned is substantially a first angle (A) in pitch from the radius along which the first group of cutters is substantially aligned; the radius along which the third group of cutters is substantially aligned is substantially the first angle (A) minus a second angle (θ), (A−θ), in pitch from the radius along which the second group of cutters is substantially aligned; the radius along which the fourth group of cutters is substantially aligned is substantially the first angle (A) plus the second angle (θ), (A+θ), in pitch from the radius along which the second group of cutters is substantially aligned; the radius along which the fifth group of cutters is substantially aligned is substantially the first angle (A) in pitch from the radius along which the fourth group of cutters is substantially aligned; and the radius along which the sixth group of cutters is substantially aligned is substantially the first angle (A) minus two times the second angle (θ), (A−2×θ), in pitch from the radius along which the fifth group of cutters is substantially aligned, wherein the second angle θ is substantially greater than zero degree.