Ratio-based mode switching for optimizing weight-on-bit
Drilling system and methods may employ a weight-on-bit optimization for an existing drilling mode and, upon transitioning to a different drilling mode, determine an initial weight-on-bit within a range derived from: a sinusoidal buckling ratio, a helical buckling ratio, and the weight-on-bit value for the prior drilling mode. The sinusoidal buckling ratio is the ratio of a minimum weight-on-bit to induce sinusoidal buckling in a sliding mode to a minimum weight-on-bit to induce sinusoidal buckling in a rotating mode, and the helical buckling ratio is the ratio of a minimum weight-on-bit to induce helical buckling in the sliding mode to a minimum weight-on-bit to induce helical buckling in the rotating mode. The ratios are a function of the length of the drill string and hence vary with the position of the drill bit along the borehole.
1. A drilling method that comprises:
operating a drill string drilling operation in a first drilling mode that applies a first weight-on-bit;
detecting a prospective drilling mode transition from the first drilling mode to a second drilling mode;
upon said detecting the prospective drilling mode transition,
determining a sinusoidal buckling ratio between a minimum weight-on-bit to induce sinusoidal buckling in sliding mode and a minimum weight-on-bit to induce sinusoidal buckling in rotating mode; and
determining a helical buckling ratio between a minimum weight-on-bit to induce helical buckling in sliding mode and a minimum weight-on-bit to induce helical buckling in rotating mode;
determining a weight-on-bit operating range that comprises a range of buckling ratios between the determined sinusoidal buckling ratio and helical buckling ratio; and
transitioning from the first drilling mode to the second drilling mode, wherein said transitioning includes transitioning from the first weight-on-bit to a second weight-on-bit that is determined in accordance with the ratio between the second weight-on-bit and the first weight-on-bit being within the weight-on-bit operating range.
2. The method of claim 1 , wherein one of the first and second drilling modes is a sliding mode and the other of the first and second drilling modes is a rotating mode.
3. The method of claim 1 , further comprising:
dynamically adapting the second weight-on-bit to maximize a rate of penetration.
4. The method of claim 1 , wherein the sinusoidal buckling ratio and helical buckling ratio each vary with position along a borehole.
5. The method of claim 1 , wherein determining a sinusoidal buckling ration and a helical buckling ratio comprises determining a sinusoidal ratio and a helical buckling ratio for a current position of a drill bit on the drill string.
6. The method of claim 1 , wherein said determining a weight-on-bit operating range further includes determining the weight-on-bit operating range based, at least in part, on the first weight-on-bit.
7. The method of claim 6 , further comprising determining the first weight-on-bit dynamically for ongoing drilling operations.
8. The method of claim 1 , wherein said determining a sinusoidal buckling ratio comprises determining a ratio of a minimum weight-on-bit to induce sinusoidal buckling in sliding mode to a minimum weight-on-bit to induce sinusoidal buckling in rotating mode, and wherein determining a helical buckling ratio comprises determining a ratio of a minimum weight-on-bit to induce helical buckling in sliding mode to a minimum weight-on-bit to induce helical buckling in rotating mode.
9. A drilling system that comprises:
a processor; and
a machine-readable medium having program code executable by the processor to cause the drilling system to:
operate a drill string drilling operation in a first drilling mode that applies a first weight-on-bit;
detect a prospective drilling mode transition from the first drilling mode to a second drilling mode;
upon said detecting the prospective drilling mode transition,
determine a sinusoidal buckling ratio between a minimum weight-on-bit to induce sinusoidal buckling in sliding mode and a minimum weight-on-bit to induce sinusoidal buckling in rotating mode; and
determine a helical buckling ratio between a minimum weight-on-bit to induce helical buckling in sliding mode and a minimum weight-on-bit to induce helical buckling in rotating mode;
determine a weight-on-bit operating range that comprises a range of buckling ratios between the determined sinusoidal buckling ratio and helical buckling ratio; and
transition from the first drilling mode to the second drilling mode, wherein said transitioning includes transitioning from the first weight-on-bit to a second weight-on-bit that is determined in accordance with the ratio between the second weight-on-bit and the first weight-on-bit being within the weight-on-bit operating range.
10. The drilling system of claim 9 , wherein one of the first and second drilling modes is a sliding mode and the other of the first and second drilling modes is a rotating mode.
11. The drilling system of claim 9 , wherein the first weight- on-bit maximizes a rate of penetration for the first drilling mode.
12. The drilling system of claim 9 , wherein said determining the sinusoidal buckling ratio and the helical buckling ratio comprises determining the sinusoidal buckling ration and the helical buckling ratio for multiple points along a borehole trajectory.
13. The system of claim 9 , wherein determining a sinusoidal buckling ration and a helical buckling ratio comprises determining a sinusoidal ratio and a helical buckling ratio for a current position of a drill bit on the drill string.
14. The system of claim 9 , wherein said determining a weight-on-bit operating range further includes determining the weight-on-bit operating range based, at least in part, on the first weight-on-bit.
15. The system of claim 9 , wherein said determining a sinusoidal buckling ratio comprises determining a ratio of a minimum weight-on-bit to induce sinusoidal buckling in sliding mode to a minimum weight-on-bit to induce sinusoidal buckling in rotating mode, and wherein determining a helical buckling ratio comprises determining a ratio of a minimum weight-on-bit to induce helical buckling in sliding mode to a minimum weight-on-bit to induce helical buckling in rotating mode.
16. A non-transitory computer readable medium comprising computer executable instructions for optimizing weight-on-bit for a drilling operation, wherein execution of the computer executable instructions causes one or more machines to perform operations comprising:
operating a drill string drilling operation in a first drilling mode that applies a first weight-on-bit;
detecting a prospective drilling mode transition from the first drilling mode to a second drilling mode;
upon said detecting the prospective drilling mode transition,
determining a sinusoidal buckling ratio between a minimum weight-on-bit to induce sinusoidal buckling in sliding mode and a minimum weight-on-bit to induce sinusoidal buckling in rotating mode; and
determining a helical buckling ratio between a minimum weight-on-bit to induce helical buckling in sliding mode and a minimum weight-on-bit to induce helical buckling in rotating mode;
determining a weight-on-bit operating range based, at least in part, on the determined sinusoidal buckling ratio and helical buckling ratio; and
transitioning from the first drilling mode to the second drilling mode, wherein said transitioning includes transitioning from the first weight-on-bit to a second weight-on-bit that is determined in accordance with the ratio between the second weight-on-bit and the first weight-on-bit being within the weight-on-bit operating range.
17. The medium of claim 16 , wherein the first weight-on-bit maximizes a rate of penetration for the first drilling mode.
18. The medium of claim 16 , further comprising:
dynamically adapting the second weight-on-bit to maximize a rate of penetration.
19. The medium of claim 16 , wherein said determining a weight-on-bit operating range further includes determining the weight-on-bit operating range based, at least in part, on the first weight-on-bit.
20. The medium of claim 19 , further comprising determining the first weight-on-bit dynamically for ongoing drilling operations.