Electromagnetic Wave Resistivity Tool Having A Tilted Antenna For Determining The Horizontal And Vertical Resistivities And Relative Dip Angle In Anisotropic Earth Formations

• US 20110199088A1
• Filed: 04/27/2011
• Published: 08/18/2011
• Est. Priority Date: 01/28/1999
• Status: Abandoned Application

• Current Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Original Assignee: Halliburton Energy Services Incorporated (Halliburton Company)
• Inventors: Bittar, Michael S.
• Application Number:
  US13/095,420
• Publication Number:
  US 20110199088A1
• Time in Patent Office: Days
• US Class Current: 324/339
• CPC Class Codes: G01V 3/28 using induction coils

Abstract

This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. Although this invention is primarily intended for MWD or LWD applications, this invention is also applicable to wireline and possibly other applications.

Claims

1. A logging while drilling tool, comprising:

a tool body configured to couple into a drill string, the tool body having a longitudinal tool axis;

a first transmitter antenna extending circumferentially in a first cutout around the tool body, the first transmitter antenna configured to transmit an electromagnetic wave into an earth formation surrounding a borehole when the tool is used in a logging while drilling operation;

a first receiver antenna extending circumferentially in a second cutout around the tool body, the first receiver antenna configured to receive an electromagnetic signal from the formation that is a result of the electromagnetic wave from the transmitter antenna, and wherein at least one of the first transmitter antenna and the first receiver antenna extends in a plane that is not orthogonal to said tool axis; and

processing circuitry operably coupled to receive a first input signal resulting from receipt of said electromagnetic signal at the first receiver antenna, the processing circuitry configured to determine at least one formation property in response to said input signal.

2. The logging while drilling tool of claim 1, further comprising:

a second transmitter antenna extending circumferentially around the tool body; and

a second receiver antenna extending circumferentially around the tool body.

3. The logging while drilling tool of claim 1, wherein the processing circuitry comprises a microprocessor.

4. The logging while drilling tool of claim 1, wherein the at least one formation property comprises a relative orientation of a subsurface formation boundary to the borehole.

5. The logging while drilling tool of claim 4, wherein the relative orientation of a subsurface formation boundary to the borehole comprises a relative dip angle.

6. The logging while drilling tool of claim 1, further comprising:

a protective covering over the first transmitter antenna; and

a protective covering over the first receiver antenna.

7. A formation resistivity logging tool configured to evaluate the resistivity of an earth formation during a drilling operation, comprising:

a tool body having a longitudinal tool axis and an outer surface, the tool body configured for coupling in a drill string;

transmitter circuitry supported by the tool body;

a first transmitter antenna surrounding the tool body and oriented at a first angle relative to the tool axis, the first transmitter antenna operably coupled to the transmitter circuitry and configured to transmit an electromagnetic wave into an earth formation;

a first receiver antenna surrounding the outer surface of the tool body and oriented at a second angle relative to the tool axis, the first receiver antenna configured to receive an electromagnetic wave from the earth formation that is a result of the electromagnetic wave from the first transmitter antenna and to provide a first antenna output signal in response thereto, and wherein said first angle is different from said second angle; and

processing circuitry operably coupled to the first receiver antenna to receive the first antenna output signal, the processing circuitry configured to determine at least one formation property at least partially in reference to the first antenna output signal.

10. The formation resistivity logging tool of claim 7, wherein the processing circuitry comprises a microprocessor.

8. (canceled)

9. (canceled)

11. A method of evaluating the resistivity of an earth formation during a drilling operation through use of a drill string, comprising the acts of:

providing a resistivity logging tool for incorporation into the drill string, the resistivity logging tool comprising,

a tool body having a longitudinal axis,

first and second transmitter antennas extending around the tool body,

first and second receiver antennas extending around the tool body, and

processing circuitry including a microprocessor, and

wherein each of said first and second receiver antennas has a respective magnetic moment that is tilted relative to the longitudinal axis of the resistivity logging tool;

during the drilling operation, transmitting a first electromagnetic wave into the earth formation through use of at least the first transmitter antenna, and receiving electromagnetic energy from the earth formation that is a result of said electromagnetic wave being transmitted into the earth formation through use of at least the first receiver antenna;

also during the drilling operation, transmitting a second electromagnetic wave into the formation through use of the second transmitter antenna, and receiving electromagnetic energy from the earth formation that is a result of the second electromagnetic wave being transmitted into the earth formation through use of at least the second receiver antenna;

using said processing circuitry to evaluate a parameter of the earth formation in reference to the received electromagnetic energy at the first and second receiver antennas.

12. The method of claim 11, wherein said magnetic moments of each of said first and second receiver antennas are tilted at different angles relative to the longitudinal axis of the logging tool.

13. The method of claim 11, wherein the evaluated parameter of the earth formation comprises a relative orientation of a subsurface formation boundary to the borehole.

14. A method of determining a parameter of earth formations during a drilling operation, comprising the acts of:

providing a resistivity logging tool configured for incorporation into a drill string,

the logging tool comprising,

a tool body having a longitudinal axis,

at least first, second, third and fourth transmitter antennas extending around the tool body,

at least first and second receiver antennas extending around the tool body, and

processing circuitry including a microprocessor, and

wherein each of said first and second receiver antennas has a magnetic moment that is tilted relative to the longitudinal axis of the tool body;

during the drilling operation, transmitting an electromagnetic wave into an earth formation through use of the first transmitter antenna, and receiving electromagnetic energy from the earth formation through use of at least the first receiver antenna;

also during the drilling operation, transmitting a second electromagnetic wave into the earth formation through use of the second transmitter antenna, and receiving electromagnetic energy from the earth formation through use of at least the second receiver antenna;

using said processing circuitry to evaluate at least one parameter of the earth formation in reference to the received electromagnetic energy at the first and second receiver antennas.

15. The method of claim 14, wherein the at least one parameter of the earth formation comprises a relative orientation of a subsurface formation boundary to a borehole.

16. The method of claim 15, wherein the relative orientation of a subsurface formation boundary to the borehole comprises a relative dip angle.