Boundary tracking control module for rotary steerable systems

1. A rotary steerable bottom hole assembly comprising:

a drill bit disposed at a distal end thereof;

azimuthal resistivity antennas and electronics configured to measure a distance to a formation boundary, the azimuthal resistivity antennas comprising:

an axial antenna including a wire winding for generating an axial magnetic moment parallel with the longitudinal axis;

a transverse antenna including an antenna body having a longer axis disposed longitudinally in the housing, and a wire coil having a central axis disposed around the antenna body, wherein the wire coil central axis is substantially perpendicular to the longer axis of the antenna body, and wherein the wire coil is configured to generate a transverse magnetic moment orthogonal to the housing longitudinal axis.

2. The rotary steerable bottom hole assembly of claim 1 , further comprising a stabilizer disposed in the bottom hole assembly uphole from the drill bit.

3. The rotary steerable bottom hole assembly of claim 2 , further comprising a non-rotating steerable housing having a longitudinal axis and disposed between the stabilizer and the drill bit, wherein the azimuthal resistivity antennas and electronics are in the housing.

4. The rotary steerable bottom hole assembly of claim 3 , further comprising a control module in the housing configured to steer the drill bit along a well path and, based on measurements from the azimuthal resistivity antennas, to steer the housing away from an approaching formation boundary and thereby maintain a distance between the steerable housing and upper or lower boundaries of a formation.

5. The rotary steerable bottom hole assembly of claim 4 , wherein the non-rotating housing further encloses a hydraulic pump and pump drive for operating one or more rams to steer the drill bit.

6. The rotary steerable bottom hole assembly of claim 4 , wherein the control module is configured to execute a pre-programmed well trajectory.

7. The rotary steerable bottom hole assembly of claim 4 , wherein the control module is configured to control a vertical component of the well path.

8. A rotary steerable system comprising:

azimuthal resistivity antennas and electronics configured to measure a distance to an upper or lower formation boundary, the azimuthal resistivity antennas comprising:

an axial antenna including a wire winding for generating an axial magnetic moment parallel with the longitudinal axis;

a transverse antenna including an antenna body having a longer axis disposed longitudinally in the housing, and a wire coil having a central axis disposed around the antenna body, wherein the wire coil central axis is substantially perpendicular to the longer axis of the antenna body, and wherein the wire coil is configured to generate a transverse magnetic moment orthogonal to the housing longitudinal axis.

9. The rotary steerable system of claim 8 , further comprising a non-rotating housing in which the azimuthal resistivity antennas are enclosed.

10. The rotary steerable system of claim 9 , further comprising a control module in the housing configured to steer a drill bit along a well path and, based on measurements from the azimuthal resistivity antennas, to steer the housing away from an approaching upper or lower formation boundary and thereby maintain a distance between the steerable housing and upper or lower formation boundary.

11. The rotary steerable system of claim 10 , further comprising a hydraulic pump and pump drive in the housing for operating one or more rams to steer the rotary steerable system.

12. The rotary steerable system of claim 10 , wherein the control module is configured to execute a pre-programmed well trajectory.

13. The rotary steerable system of claim 10 , wherein the non-rotating housing is disposed between the drill bit and a stabilizer.

14. The rotary steerable system of claim 10 , wherein the control module is configured to control a vertical component of the well path.

15. A method of directional drilling comprising:

measuring a distance between a housing and a distance to an upper or lower formation boundary with azimuthal resistivity antennas comprising:

an axial antenna including a wire winding for generating an axial magnetic moment parallel with the longitudinal axis; and

a transverse antenna including an antenna body having a longer axis disposed longitudinally in the housing, and a wire coil having a central axis disposed around the antenna body, wherein the wire coil central axis is substantially perpendicular to the longer axis of the antenna body, and wherein the wire coil is configured to generate a transverse magnetic moment orthogonal to the housing longitudinal axis.

16. The method of claim 15 , further comprising steering a drill bit along a well path by operating a rotary steerable system having the azimuthal resistivity antennas and a control module enclosed within a non-rotating steerable housing.

17. The method of claim 16 , further comprising steering the drill bit away from an approaching upper or lower formation boundary, based on the azimuthal resistivity measurements, to maintain a distance between the steerable housing and the approaching upper or lower boundary of the formation.

18. The method of claim 17 , further comprising steering the drill bit by radially extending one or more rams disposed within the non-rotating housing outward to press against the wellbore thereby causing the drill bit to press on an opposite side of the wellbore and cause a direction change.

19. The method of claim 17 , wherein the control module is configured to execute a pre-programmed well trajectory.

20. The method of claim 17 , wherein the control module is configured to control a vertical component of the well path.