Optimizing electromagnetic telemetry transmissions

Patent metadata

Field	Value
Publication number	US-2016201455-A1
Application number	US-201414914050-A
Country	US
Kind code	A1
Filing date	Aug 28, 2014
Priority date	Aug 28, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

An electromagnetic telemetry system adjusts telemetry parameters which may include carrier frequency, signal amplitude and/or data encoding protocol to achieve reliable data transmission and to conserve power. In some embodiments, sweep signals transmit a range of carrier frequencies and the parameters are determined in part by analyzing the received sweep signals. In some embodiments, different parameters are selected automatically based on a mode of drilling.

First claim

What is claimed is:

1 . A method for downhole electromagnetic (EM) telemetry in a downhole drilling operation, the method comprising the steps of:
determining a mode of the drilling operation; sending a set of EM sweep signals from a downhole EM telemetry system located at a downhole location to an uphole system located at a surface location, each of the EM sweep signals having a different frequency; determining whether each of the EM sweep signals is received at the uphole system and, for the EM sweep signals received, measuring parameters of the received EM sweep signals, the parameters comprising at least one of signal strength and signal-to-noise-ratio; based at least in part on: the mode of drilling operation, the EM sweep signals received, and the parameters measured, determining a protocol for downhole data transmission, the protocol specifying protocol parameters including one or more of signal frequency, signal amplitude, and data encoding scheme; and configuring the downhole EM telemetry system to transmit data to the uphole system using the protocol.

2 . A method according to claim 1 wherein: the data encoding scheme comprises a number of cycles of EM signals to use for encoding symbols for transmission; and
determining the protocol comprises setting the number of cycles to be used for encoding signals for transmission.

3 . A method according to claim 1 wherein each mode of the drilling operation is assigned a pre-set protocol.

4 . A method according to claim 1 wherein the protocol is determined based at least in part on one or more of a desired data rate and a desired power consumption.

5 . A method according to claim 1 wherein the protocol is determined at the uphole system by a processor and the protocol is communicated to the downhole EM telemetry system using a downlink transmission system.

6 . A method according to claim 5 wherein the protocol is determined at the uphole system by user input in combination with the processor.

7 . A method according to claim 1 wherein a set of pre-set protocols are stored in the downhole EM telemetry system and determining the protocol for downhole data transmission comprises:
based at least in part on one or more of a mode of drilling operation, the EM signals received, and the parameters measured, generating at the uphole system an index identifying one of the pre-set protocols stored in the downhole EM telemetry system;
communicating the index to the downhole EM telemetry system using a downlink transmission system; and
selecting one of the pre-set protocols stored in the downhole EM telemetry system based at least in part on the index communicated.

8 . A method according to claim 1 wherein the mode of drilling operation is determined using measurements obtained from downhole sensors.

9 . A method according to claim 1 , the method further comprising:
periodically, sending sets of EM sweep signals from the downhole EM telemetry system to the uphole system; and detecting the EM sweep signals at the uphole system; and based on the detected EM sweep signals, determining whether to adjust one or more of the protocol parameters.

10 . A method according to claim 1 wherein determining the protocol comprises:
a) selecting a frequency and an amplitude for the protocol for EM data transmission signals based at least in part on the received EM sweep signals; and
b) if EM signals of the frequency and amplitude are not properly received at the uphole system, modifying the protocol by reducing the frequency until the frequency is at a minimum acceptable frequency and, if EM signals of the minimum acceptable frequency and selected amplitude are not properly received at the uphole system, increasing the amplitude of the protocol.

11 . A method according to claim 10 comprising, if EM signals of the minimum acceptable frequency and a maximum acceptable amplitude are not properly received at the uphole system, switching to an alternative telemetry system.

12 . A method according to claim 10 comprising, if the EM signal of the minimum acceptable frequency and a maximum acceptable amplitude does not have at least a threshold acceptable data rate, reducing a number of cycles per symbol for the protocol.

13 . A method according to claim 12 comprising determining the threshold acceptable data rate based at least in part on the nature of data available for transmission.

14 . A method according to claim 10 further comprising: checking if the EM signal has a strength that exceeds a threshold and, if so, increasing the frequency and/or decreasing the amplitude for the protocol.

15 . A method according to claim 14 wherein the strength of the EM signal is determined based at least in part on a bit energy.

16 . A method according to claim 15 comprising reducing the number of cycles per symbol for the protocol without reducing the bit energy below a threshold value.

17 . A method according to claim 1 wherein the set of EM sweep signals comprises a subset of a set of predetermined EM sweep signals and the method comprises sending only the subset of EM sweep signals from the downhole EM telemetry system to the uphole system.

18 . A method according to claim 1 wherein the data encoding scheme is one of quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), phase-shift keying (PSK), frequency-shift keying (FSK), quadrature amplitude modulation (QAM), 8 amplitude shift keying (BASK), and amplitude phase shift keying (APSK).

19 . A method according to claim 1 comprising, at the downhole EM telemetry system, waiting for a downlink transmission from the uphole system after sending the set of EM sweep signals and if the downhole EM telemetry system does not receive the downlink transmission within a pre-determined period, applying a default pre-determined protocol.

20 . A method according to claim 1 wherein the set of EM sweep signals comprises a first EM sweep signal having a lower frequency and a second EM sweep signal having a higher frequency and if the second EM signal is received by the uphole system, the protocol is determined based only on the second EM signal.

21 . A method according to claim 5 wherein the downlink transmission system comprises an EM telemetry system or a mud pulse telemetry system.

22 . A method according to claim 1 wherein the protocol is determined at least in part based on a current state of charge of downhole batteries powering the downhole EM telemetry system.

23 . A method according to claim 1 comprising encoding information in the EM sweep signals and decoding the information from the received EM sweep signals.

24 . A method according to claim 23 wherein encoding the information in the EM sweep signals comprises one or more of varying an order of the frequencies transmitted, varying a number of cycles of different frequencies transmitted, and modulating the frequencies transmitted in the EM sweep signals.

25 . A method according to claim 23 wherein the encoded information comprises one or more of an encoding scheme for encoding data transmitted using the protocol, data relating to downhole conditions, and data relating to downhole systems.

26 . A method according to claim 1 wherein sending the set of EM sweep signals comprises sending two or more of the EM signals concurrently.

27 . A method according to claim 1 comprising autom

Assignees

• Evolution Engineering Inc

Inventors

• Liu Jili
• Xu Mingdong
• Logan Aaron W
• Switzer David A
• Varga Monica E
• Kazemi Miraki Mojtaba

Classifications

• H04W52/245

  taking into account received signal strength · CPC title

• H04W52/028

  switching on or off only a part of the equipment circuit blocks · CPC title

• E21B47/125 Primary

  using earth as an electrical conductor (by electromagnetic energy E21B47/13) · CPC title

• H04Q9/00

  Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom · CPC title

• H04W52/241

  taking into account channel quality metrics, e.g. SIR, SNR, CIR or Eb/lo · CPC title