Apparatus and Method for Formation Resistivity Measurements

• US 20140136114A1
• Filed: 11/09/2012
• Published: 05/15/2014
• Est. Priority Date: 11/09/2012
• Status: Abandoned Application

• Current Assignee: Greatwall Drilling Company
• Original Assignee: Greatwall Drilling Company
• Inventors: Li, Jing, Liu, Ce, Liu, Naizheng, Zhao, Qihui, Lu, Yuzhou, Bai, Rui, Li, Yonghe
• Application Number:
  US13/672,951
• Publication Number:
  US 20140136114A1
• Time in Patent Office: Days
• US Class Current: 702/7
• CPC Class Codes: G01V 3/28 using induction coils
• CPC Class Codes: G06F 15/00 Digital computers in general details G06F1/00 – G06F13/00; Data processing equipment in general

Abstract

An apparatus for measuring formation resistivity in logging while drilling application includes a tool body, a pair of receivers deployed on the tool body including a first receiver and a second receiver, a measuring transmitter deployed on the tool body and at an axial distance from the pair of receivers, and a compensating transmitter deployed on the tool body and positioned substantially at the midpoint of the pair of receivers. The compensating transmitter transmits compensating signals to the pair of receivers and the measuring transmitter transmits measuring signals to the pair of receivers. The pair of receivers measures the amplitudes and phases of the compensating signals and the measuring signals in a sequential order and computes a compensated amplitude ratio and a compensated differential phase accordingly. A corresponding method for measuring formation resistivity is also provided.

Claims

1. An apparatus for measuring formation resistivity in logging while drilling application comprising:

a tool body;

a pair of receivers deployed on the tool body including a first receiver and a second receiver;

a measuring transmitter deployed on the tool body and at an axial distance from the pair of receivers;

a compensating transmitter deployed on the tool body and positioned substantially at the midpoint of the pair of receivers;

wherein the compensating transmitter transmits compensating signals to the pair of receivers and the measuring transmitter transmits measuring signals to the pair of receivers; and

wherein the pair of receivers measures the amplitudes and phases of the compensating signals and the measuring signals in a sequential order and computes a compensated amplitude ratio and a compensated differential phase accordingly.

2. The apparatus according to claim 1 further comprises a compensation controller coupled to the compensating transmitter and the pair of receivers to determine receiver-induced error factors in amplitude and phase reflected in the pair of receivers when the compensating transmitter transmits compensating signals to the pair of receivers for calibrating receiver-induced error in amplitude and phase reflected in the pair of receivers when the measuring transmitter transmits measuring signals to the pair of receivers.

3. The apparatus according to claim 2 further comprises a processor coupled to the compensation controller and the pair of receivers and configured to control the operation of the apparatus and help the compensation controller to determine receiver-induced error factors in amplitude and phase reflected in the pair of receivers when the compensating transmitter fires and to help the compensation controller compute the compensated amplitude ratio and the compensated differential phase after the measuring transmitter firing.

4. The apparatus according to claim 3 further comprises a storage device coupled to the processor and stored with a two-dimensional conversion chart, which is for converting the compensated amplitude ratio and the compensated differential phase into corresponding formation resistivity.

5. The apparatus according to claim 1 wherein the measuring transmitter comprises a measuring transmitter circuit configured to generate the measuring signals to be transmitted by the measuring transmitter.

6. The apparatus according to claim 1 wherein the first receiver comprises a first receiver circuit configured to receive and process the compensating and measuring signals transmitted by the compensating transmitter and measuring transmitter respectively.

7. The apparatus according to claim 1 wherein the second receiver comprises a second receiver circuit configured to receive and process the compensating and measuring signals transmitted by the compensating transmitter and measuring transmitter respectively.

8. The apparatus according to claim 1 wherein the compensating transmitter comprises a compensating transmitter circuit configured to generate compensating signals to be transmitted by the compensating transmitter.

9. The apparatus according to claim 1 wherein the measuring transmitter is positioned near the first receiver and the corresponding compensated amplitude ratio is expressed by an equation

10. The apparatus according to claim 1 wherein the measuring transmitter is positioned near the second receiver and the corresponding compensated amplitude ratio is expressed by an equation

11. The apparatus according to claim 1 wherein the measuring transmitter is positioned near the first receiver and the corresponding compensated differential phase is expressed by an equation

12. The apparatus according to claim 1 wherein the measuring transmitter is positioned near the second receiver and the corresponding compensated differential phase is expressed by an equation

13. The apparatus according to claim 1 wherein each of the measuring transmitter, the compensating transmitter, and the pair of receivers further comprise at least one antenna for transmitting or receiving signals.

14. The apparatus according to claim 1 wherein the tool body is a drilling collar.

15. A method for measuring formation resistivity in a subterranean borehole comprising:

deploying a tool body in the borehole;

the tool body including a pair of receivers, a measuring transmitter at an axial distance from the pair of receivers, and a compensating transmitter substantially at the midpoint of the pair of receivers;

firing the compensating transmitter to transmit compensating signals;

utilizing the pair of receivers to receive the compensating signals from the compensating transmitter and measure the amplitudes and phases of the compensating signals;

firing the measuring transmitter to transmit measuring signals;

utilizing the pair of receivers to receive the measuring signals from the measuring transmitter and measure the amplitudes and phases of the measuring signals; and

computing a compensated amplitude ratio and a compensated differential phase based on the amplitudes and phases of the compensating signals and the measuring signals.

16. The method according to claim 15 further comprises providing a compensation controller coupled to the compensating transmitter and the pair of receivers to determine receiver-induced error factors in amplitude and phase reflected in the pair of receivers when the compensating transmitter is fired to reduce receiver-induced errors in amplitude and phase reflected in the pair of receivers when the measuring transmitter is fired.

17. The method according to claim 15 further comprises providing a conversion chart to help convert the computed compensated amplitude ratio and the compensated differential phase into corresponding formation resistivity.

18. A logging while drilling tool comprising:

a drilling collar;

a pair of receivers mounted on the drilling collar including a first receiver and a second receiver;

multiple measuring transmitters mounted on the drilling collar, at an axial distance from the pair of receivers, and separated from each other;

a compensating transmitter mounted on the drilling collar and positioned substantially at the midpoint of the pair of receivers;

wherein the compensating transmitter transmits compensating signals to the pair of receivers and the measuring transmitters transmit measuring signals to the pair of receivers; and

wherein the pair of receivers measures the amplitudes and phases of the compensating signals and the measuring signals in a sequential order and computes a compensated amplitude ratio and a compensated differential phase accordingly.

19. The apparatus according to claim 18 further comprises a compensation controller coupled to the compensating transmitter and the pair of receivers to help calibrate receiver-induced error in amplitude and phase reflected in the pair of receivers when the measuring transmitter transmits measuring signals to the pair of receivers by determining receiver-induced error factors in amplitude and phase reflected in the pair of receivers when the compensating transmitter transmits compensating signals to the pair of receivers.

20. The apparatus according to claim 19 further comprises a processor coupled to the compensation controller and the pair of receivers and configured to help the compensation controller to determine receiver-induced error factors in amplitude and phase reflected in the pair of receivers when the compensating transmitter fires and to help the pair of receivers compute the compensated amplitude ratio and the compensated differential phase after the measuring transmitter firing.

21. The apparatus according to claim 18 wherein each of the measuring transmitters, the compensating transmitter, and the pair of receivers further comprise at least one antenna for transmitting or receiving signals.