Downhole time domain reflectometry with optical components

Patent metadata

Field	Value
Publication number	US-9512717-B2
Application number	US-201213655607-A
Country	US
Kind code	B2
Filing date	Oct 19, 2012
Priority date	Oct 19, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A disclosed system for downhole time domain reflectometry (TDR) includes a surface electro-optical interface, a downhole electro-optical interface, a fiber-optic cable that couples the surface electro-optical interface and the downhole electro-optical interface, and an electrical transmission line that extends from the downhole electro-optical interface into a wellbore environment to enable TDR operations. A described method for downhole TDR includes transmitting an optical signal to a downhole environment, converting the optical signal to an electrical signal in the downhole environment, reflecting the electrical signal using an electrical transmission line in the downhole environment, analyzing data corresponding to the reflected electrical signal, and displaying a result of the analysis.

First claim

What is claimed is:

1. A downhole time domain reflectometry (TDR) system, the system comprising:
a surface electro-optical interface;
a downhole electro-optical interface;
a fiber-optic cable that is deployed in a borehole and that couples the surface electro-optical interface and the downhole electro-optical interface;
an electrical transmission line that extends from the downhole electro-optical interface into a region of interest with one or more formation fluids that contact the electrical transmission line; and
a data analysis unit coupled to the surface electro-optical interface, wherein the data analysis unit is configured to analyze TDR interrogation response signals to recover electromagnetic profile information regarding the one or more formation fluids, wherein the TDR interrogation response signals are obtained by using the downhole electro-optical interface to convert a TDR interrogation signal from an optical signal conveyed by the fiber-optic cable to an electrical signal conveyed by the electrical transmission line, and to convert a TDR interrogation response signal from a reflected electrical signal conveyed by the electrical transmission to a corresponding optical signal conveyed by the fiber-optic cable.

2. The downhole TDR system of claim 1 , wherein the surface electro-optical interface comprises a light source, a light detector separate from the light source, and an optical amplifier.

3. The downhole TDR system of claim 1 , wherein the surface electro-optical interface comprises a component that operates as a light source and as a light detector.

4. The downhole TDR system of claim 1 , wherein the downhole electro-optical interface comprises a light detector and a light source separate from the light detector.

5. The downhole TDR system of claim 1 , wherein the downhole electro-optical interface comprises a component that operates as a light source and as a light detector.

6. The downhole TDR system of claim 1 , wherein the downhole electro-optical interface comprises an energy storage unit with a trigger to release accumulated energy.

7. The downhole TDR system of claim 6 , wherein the trigger is activated based on at least one of an electrical control signal, an optical control signal, and a voltage across the energy storage unit reaching a predetermined threshold.

8. The downhole TDR system of claim 1 , wherein the electrical transmission line comprises two parallel conductors in a twinaxial arrangement and with a predetermined termination.

9. The downhole TDR system of claim 8 , wherein a light source of the downhole electro-optical interface is arranged for when the predetermined termination is an open-circuit.

10. The downhole TDR system of claim 8 , wherein a light source of the downhole electro-optical interface is arranged for when the predetermined termination is a closed-circuit.

11. The downhole TDR system of claim 1 , wherein the transmission line comprises a plurality of transmission lines to account for at least one of a predetermined wellbore depth, a predetermined power limitation, and a predetermined signal-to-noise ratio (SNR) limitation.

12. The downhole TDR system of claim 1 , further comprising a plurality of downhole electro-optical interfaces assigned to different downhole zones, and an optical fiber arrangement to convey power to the plurality of downhole electro-optical interfaces.

13. The downhole TDR system of claim 12 , wherein the optical fiber arrangement is configured to employ multiplexing components to convey power to the plurality of downhole electro-optical interfaces.

14. A method for downhole time domain reflectometry (TDR), comprising:
deploying a fiber-optic cable in a borehole;
converting a TDR interrogation signal from an optical signal conveyed by the fiber-optic cable to an electrical signal conveyed by an electrical transmission line in a downhole region of interest with one or more formation fluids that contact the electrical transmission line;
converting a TDR interrogation response signal from a reflected electrical signal conveyed by the electrical transmission line to a corresponding optical signal conveyed by the fiber-optic cable;
transmitting the corresponding optical signal to a surface environment;
converting the corresponding optical signal to a resulting electrical signal;
analyzing the resulting electrical signal to recover electromagnetic profile information regarding the one or more formation fluids; and
displaying a result of the analysis.

15. The method of claim 14 , wherein said analyzing includes identifying at least one of a water zone, a sand zone, a gas zone, and an oil zone.

16. The method of claim 14 , wherein said analyzing includes detecting a characteristic impedance variation in the downhole environment based on the reflected electrical signal, and correlating the detected characteristic impedance variation with at least one of an oil-gas boundary, a water-gas boundary, and a water-oil boundary.

17. The method of claim 14 , further comprising conveying power for TDR operations to a plurality of downhole electro-optical interfaces assigned to different downhole zones via an optical fiber arrangement.

18. The method of claim 17 , further comprising performing multiplexing operations along the optical fiber arrangement to convey power to the plurality of downhole electro-optical interfaces.

19. A downhole time domain reflectometry (TDR) circuit, comprising:
a fiber-optic cable deployed in a borehole;
a light detector between the fiber-optic cable and an electrical transmission line that extends into a downhole region of interest with one or more formation fluids that contact the electrical transmission line; and
a light source between the fiber-optic cable and the electrical transmission line,
wherein the light detector is configured to convert a TDR interrogation signal from an optical signal conveyed by the fiber-optic cable to an electrical signal conveyed by the electrical transmission line, and wherein the light source is configured to convert a TDR interrogation response signal that conveys electromagnetic profile information regarding the one or more formation fluids from a reflected electrical signal conveyed by the electrical transmission line to a corresponding optical signal conveyed by the fiber-optic cable.

20. The downhole TDR circuit of claim 19 , wherein the electrical transmission line comprises at least two parallel conductor arranged as an open circuit.

21. The downhole TDR circuit of claim 20 , wherein a quantity and length of the at least two conductors is predetermined based on a power or signal-to-noise (SNR) criteria.

22. The downhole TDR circuit of claim 19 , wherein the TDR interrogation response signal conveys information regarding characteristic impedance variations in the downhole region of interest due to at least one of an oil-gas boundary, a water-gas boundary, and a water-oil boundary.

Assignees

• Halliburton Energy Services Inc

Inventors

• Skinner Neal G
• Samson Etienne M
• Sharp David Paul
• Maida John L

Classifications

• H04B10/071 Primary

  using a reflected signal, e.g. using optical time domain reflectometers [OTDR] · CPC title

• E21B47/135 Primary

  using light waves, e.g. infrared or ultraviolet waves · CPC title

• H04B13/02

  Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy · CPC title

• G01D5/35358

  using backscattering to detect the measured quantity · CPC title

• E21B47/123 Primary

  Fixed Constructions · mapped topic