Method and Apparatus for Determining Formation Boundary Near the Bit for Conductive Mud

• US 20080297161A1
• Filed: 07/24/2008
• Published: 12/04/2008
• Est. Priority Date: 03/16/2007
• Status: Active Grant

• Current Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Original Assignee: Baker Hughes Incorporated (Baker Hughes Company)
• Inventors: Gorek, Matthias
• Granted Patent: US 8,049,508 B2
• Time in Patent Office: Days
• US Class Current: 324/342
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

A method and apparatus for determining a parameter of interest of an earth formation during drilling of a borehole. A first toroidal coil antenna induces a current along a path that includes a bottomhole assembly and the formation. A second toroidal coil antenna disposed at the drillbit and oriented at a non-zero angle to the longitudinal axis of the bottomhole assembly measures an electrical signal resulting from the current, the electrical signal being a parameter of interest of the formations.

Claims

1. An apparatus for determining a resistivity parameter of an earth formation during drilling of a borehole therein, the apparatus comprising:

a drillbit configured to be conveyed on a bottomhole assembly (BHA) configured to drill the borehole;

a first toroidal antenna disposed on the BHA and oriented along a longitudinal axis of the BHA;

a current source configured to energize the first toroidal antenna to induce a current which travels in a path that includes the BHA and the formation;

a second toroidal antenna disposed near the drillbit and oriented at a non-zero angle to the longitudinal axis of the BHA;

a device configured to measure at the second toroidal antenna an electrical signal resulting from the current, the electrical signal being indicative of the resistivity parameter; and

at least one processor configured to estimate a value of the resistivity parameter using the electrical signal.

2. The apparatus of claim 1 wherein the resistivity parameter is at least one of (i) a resistivity of the earth formation, (ii) a conductivity of the earth formation, (iii) a distance to an interface in the earth formation, and (iv) a resistivity image of the formation.

3. The apparatus of claim 1 further comprising an orientation sensor configured to determine a toolface angle of the BHA.

4. The apparatus of claim 3, wherein the at least one processor is further configured to select a toolface angle corresponding to a High-Side response and a Low-Side response at the second toroidal coil antenna.

5. The apparatus of claim 3 wherein the orientation sensor is selected from the group consisting of (i) an accelerometer, (ii) a magnetometer, and (iii) a gyroscope.

6. The apparatus of claim 1, wherein the at least one processor is further configured to determine a dip angle of a formation.

7. The apparatus of claim 1 wherein the at least one processor is further configured to control a direction of drilling of the BHA based on at least one of:

(i) a determined distance to an interface in the earth formation, and (ii) a resistivity image of the formation.

8. A method of determining a resistivity parameter of an earth formation during drilling of a borehole, the method comprising:

conveying a drillbit configured to drill the borehole on a bottomhole assembly (BHA);

energizing a first toroidal antenna disposed on the BHA and oriented along a longitudinal axis of the BHA to induce a current which travels in a path that includes the BHA and the formation;

measuring at a second toroidal antenna disposed near the drillbit and oriented at a non-zero angle to the longitudinal axis of the BHA an electrical signal resulting from the current, the electrical signal being indicative of the resistivity parameter; and

estimating a value of the resistivity parameter using the electrical signal.

9. The method of claim 8 wherein the resistivity parameter is at least one of (i) a resistivity of the earth formation, (ii) a conductivity of the earth formation, (iii) a distance to an interface in the earth formation, and (iv) a resistivity image of the formation.

10. The method of claim 8 further comprising determining a toolface angle of the BHA and using the determined toolface angle in determining a resistivity image.

11. The method of claim 10 further comprising selecting a toolface angle corresponding to a High-Side response and a Low-Side response at the second toroidal coil antenna.

12. The method of claim 10 wherein determining a toolface angle of the BHA further comprising using an orientation sensor selected from the group consisting of:

(i) an accelerometer, (ii) a magnetometer, and (iii) a gyroscope.

13. The method of claim 8 further comprising determining a dip angle of a formation.

14. The method of claim 8 further comprising controlling a direction of drilling of the BHA based on at least one of:

(i) a determined distance to an interface in the earth formation, and (ii) a resistivity image of the formation.

15. A computer-readable medium accessible to a processor, the computer-readable medium including instructions which enable the processor to estimate a value of a resistivity parameter of an earth formation surrounding a borehole using a signal provided by a first antenna in the borehole in response to a current induced in the earth formation by a second antenna, wherein an axis of the first antenna is inclined relative to a longitudinal axis of the borehole.

16. The computer-readable medium of claim 15 further comprising at least one of (i) a ROM, (ii) and EPROM, (iii) an EEPROM, (iv) a flash memory, and (v) an optical disk.

17. The computer-readable medium of claim 15 wherein the instructions further enable the processor to further control a direction of drilling of the BHA based on at least one of:

(i) a determined distance to an interface in the earth formation, and (ii) a resistivity image of the formation.