NETWORK TELEMETRY SYSTEM AND METHOD
A telemetry system produces, transmits and receives signal sets from network nodes, which correspond to transceiver stations. Repeater scheduling and other interference mitigating techniques are utilized to simultaneously transmit from multiple nodes with minimized network degradation. Update interval/rate and network throughput are thereby fixed regardless of the number of network nodes and a network telemetry method is provided using the system.
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This application claims priority in U.S. Provisional Application No. 61/800,063 for Increased Throughput Downhole Network Telemetry System and Method, filed Mar. 15, 2013. This application is related to U.S. Patent Applications Ser. No. 61/731,898 for Downhole Low Rate Linear Repeater Network Timing Control System and Method, filed Nov. 30, 2012; and Ser. No. 61/799,588, for Robust Network Downhole Telemetry Repeater System and Method, filed Mar. 15, 2013. All of the above applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates generally to telemetry apparatuses and methods, and more particularly to acoustic telemetry increased throughput network systems and methods for the well construction (drilling, completion) and production (e.g., oil and gas) industries.
2. Description of the Related Art
Acoustic telemetry is a method of communication used in the well drilling, completion and production industries. In a typical drilling environment, acoustic extensional carrier waves from an acoustic telemetry device are modulated in order to carry information via the drillpipe as the transmission medium to the surface. Upon arrival at the surface, the waves are detected, decoded and displayed in order that drillers, geologists and others helping steer or control the well are provided with drilling and formation data. In production wells, downhole information can similarly be transmitted via the well casings.
The theory of acoustic telemetry as applied to communication along drillstrings has generally been confirmed by empirical data in the form of accurate measurements. It is now generally recognized that the nearly regular periodic structure of drillpipe imposes a passband/stopband structure on the frequency response, similar to that of a comb filter. Dispersion, phase non-linearity and frequency-dependent attenuation make drillpipe a challenging medium for telemetry, the situation being made even more challenging by the significant surface and downhole noise generally experienced.
Drillstring acoustic telemetry systems are commonly designed with multiple transceiver nodes located at spaced intervals along the drillstring or wellbore. The nodes can be configured as signal repeaters as necessary. Acoustic telemetry networks can function in a synchronized fashion with the operation of the nodes and repeater nodes and other system components. Data packets consisting of downhole sensor data were relayed node to node, in a daisy chain or linear fashion, typically beginning from a node located in the borehole apparatus (BHA), through the network to a destination, usually the surface receiver system. For purposes of minimizing interference between nodes, the data packets were transmitted (typically up-string) using time division multiplexing (TDM) techniques. Maximizing data packet transmission speed and throughput are objectives of drillstring telemetry systems and methods. For a discussion of a repeater network for these applications, see co-pending U.S. Patent Application Ser. No. 61/731,898.
When exploring for oil or gas, and in other drilling applications, an acoustic transmitter can be placed near the BHA, typically near the drill bit where the transmitter can gather certain drilling, wellbore, and geological formation data, process this data, and then convert the data into a signal to be transmitted uphole to an appropriate receiving and decoding station. In some systems, the transmitter is designed to produce elastic extensional stress waves that propagate through the drillstring to the surface, where the waves are detected by sensors, such as accelerometers, attached to the drillstring or associated drilling rig equipment. These waves carry information of value to the drillers and others who are responsible for steering the well. Examples of such systems and their components are shown in: Drumheller U.S. Pat. No. 5,128,901 for Acoustic Data Transmission through a Drillstring; Drumheller U.S. Pat. No. 6,791,470 for Reducing Injection Loss in Drillstrings; Camwell et al. U.S. Pat. No. 7,928,861 for Telemetry Wave Detection Apparatus and Method; and Camwell et al. U.S. Pat. No. 8,115,651 for Drill String Telemetry Methods and Apparatus. These patents are incorporated herein by reference.
SUMMARY OF THE INVENTIONIn the practice of the present invention, a network is configured with multiple nodes using the acoustic transmission channel simultaneously, i.e., “multiplexing” the channel. Network throughput is thus decoupled from the number of nodes and performance increases accordingly. Internode interference can be controlled by one or more methods, including the following:
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- Node transmission timing: nodes transmitting at separate times. Current (prior art) method which tends to be relatively inefficient. E.g., time division multiplexing (TDM).
- Attenuation where nodes transmit at the same time and interference is suppressed by differences in propagation distance and associated path loss (signal attenuation).
- Frequency differentiation where nodes transmit simultaneously on different frequencies whereby interference is suppressed by the frequency separations and associated filtering.
- Signal orthogonality with nodes transmitting at the same time but interference being suppressed by the orthogonal relationship of the signal sets.
- Directional transmitter and receiver configurations, with nodes tuned to transmit in the direction of the desired destination node or receive in the direction of the originating node, thereby minimizing interference within the network.
Other objects and advantages of the present invention will be apparent from the following description. Detailed descriptions of exemplary embodiments are provided in the following sections. However, the invention is not limited to such embodiments.
In the following description, reference is made to “up” and “down” waves, but this is merely for convenience and clarity. It is to be understood that the present invention is not to be limited in this manner to conceptually simple applications in acoustic communication from the downhole end of the drillstring to the surface.
I. Drilling Rig, Drillstring and Well EnvironmentReferring to the drawings in more detail, the reference numeral 2 generally designates a high throughput network system embodying an aspect of the present invention. Without limitation on the generality of useful applications of the system 2, an exemplary application is in a drilling rig 4 (
The drillstring 12 can terminate at or near a bottom-hole (borehole) apparatus (BHA) 20, which can be at or near an acoustic transceiver node (Primary) Station 0 (ST0). Other rig configurations can likewise employ the present invention, including top-drive, coiled tubing, etc.
Data packets contain sensor or node status data and are transmitted from the primary node (e.g., ST0, typically the deepest node) and relayed from node-to-node in a daisy-chain (herein interchangeably referred to also as linear or serial) fashion to the surface receiver (Surface Rx) 21, which is generally located at or near the wellhead. The data packets include sensor measurements from the BHA 20 and other sensors along the drillstring 12. Such data packet sensor measurements can include, without limitation, wellbore conditions (e.g., annular/bore/differential pressure, fluid flow, vibration, rotation, etc.). Local sensor data can be added to the data packet being relayed at each sensor node, thus providing along-string-measurements (ASMs).
A single node functions as the master node (e.g., ST0) and is typically an edge node at the top or bottom of the drillstring 12. The master node monitors well conditions and sends data packets of varying type and intervals accordingly.
II. Prior Art Acoustic Repeater SchedulingPreferably multiple nodes are configured for using the acoustic transmission channels at the same time, i.e., “multiplexing” the drillstring channel. Multiplexing, with multiple nodes transmitting simultaneously, decouples network throughput dependency on the number of nodes, and increases performance. However, if not mitigated, multiple nodes transmitting simultaneously will lead to inter-node interference and an associated degradation in link performance. One or more of the following methods can be implemented to control internode interference during multi-node transmission:
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- Signal attenuation, with nodes transmitting simultaneously and interference being suppressed by differences in propagation distance and associated path loss, and perhaps further optimized through adjustment of node transmission power level.
- Frequency separation with nodes transmitting simultaneously but on different frequencies whereby interference is suppressed.
- Signal orthogonality, with nodes transmitting at the same time and interference being suppressed by low correlation between signals within allowable signal set.
- Directional transmitter and receiver configurations, with nodes tuned to transmit in the direction of the desired destination node or receive in the direction of the originating node, thereby minimizing interference within the network.
The interference between nodes can be further managed by coordinating network timing in such a manner that, while multiple node transmissions overlap in time, the desired signal precedes the anticipated interferer signal such that a sufficient portion of the desired signal experiences no interference allowing the receiving node to achieve more reliable signal detection, timing and phase recovery, and decoding once the interfering node begins transmission and signals overlap. This method allows the receiver to favour the desired signal over the interferer. See, e.g.,
Examples of low-interference signal sets include: signals of non-overlapping frequencies (Frequency Division Multiplexing (FDM)), which can be contiguous frequency blocks (e.g., different passbands) or interleaved blocks (e.g., OFDM); signals of low cross-correlations, such as up/down, linear/exponential chirps, pseudorandom noise (PRN) sequences (Code Division Multiplexing (CDM)), e.g., Walsh codes, Hadamard, etc.; and signals transmitted on separate, isolated mediums (channels): acoustic, electromagnetic pulse, and mud pulse (MP); and propagation modes (e.g., axial, longitudinal and spiral).
The configurations described above have advantages of preserving multi-hop repeater network throughput, which is fundamentally related to channel multiplexing (reuse) efficiency. Multiple nodes must share the channel, reducing system throughput proportionally to the number of nodes in a system. For example, a five-node system capable of 40 bits-per-second (bps) has a maximum throughput of only 40 bps/5 nodes=8 bps, neglecting guard and signal propagation times, while a two-node system has a maximum throughput of 40 bps/2 nodes=20 bps. All multi-hop linear telemetry systems will encounter the same limitation, including electromagnetic (EM) systems.
It is to be understood that the invention can be embodied and combined in various forms, and is not to be limited to the examples discussed above. The range of components and configurations which can be utilized in the practice of the present invention is virtually unlimited.
Claims
1. A wireless telemetry network system, which includes:
- multiple network nodes;
- a sensor associated with one or more of said nodes and adapted for providing output comprising signal data corresponding to an operating or status condition;
- a transmitter associated with one of said nodes for propagating said signal data between nodes;
- a receiver associated with one of said nodes for receiving signals from other nodes;
- multiple network nodes adapted for receiving said signal data; and
- said system being adapted for transmitting telemetry signals across multiple network links simultaneously.
2. A linear wireless telemetry network system for a well including a wellbore structure extending subsurface downwardly from the surface, which telemetry network system includes:
- multiple network nodes distributed along the wellbore;
- at least one said node including a sensor adapted for providing a signal data set output corresponding to a downhole condition;
- a transmitter for propagating said signal between nodes;
- a receiver for receiving said signal from other nodes; and
- said system being adapted for transmitting telemetry signals across multiple network links simultaneously.
3. The telemetry system according to claim 2, which includes:
- said telemetry signals being chosen from among the group comprising acoustic, electromagnetic (EM), mud pulse (MP) and optical.
4. The telemetry system according to claim 2 wherein said signal sets comprise orthogonal (low interference/cross-correlation) signal sets assigned to network nodes so as to reduce interference at adjacent nodes.
5. The telemetry system according to claim 4 wherein said telemetry signals are located in multiple, minimally-interfering frequency channels within a medium and/or separate mediums chosen from among the group comprising acoustic, EM and MP.
6. The telemetry system according to claim 2 wherein:
- said nodes have predefined separations (and therefore a signal propagation associated attenuation level) and/or transmission power levels adapted so as to maintain interference at receiver locations within a tolerable range.
7. The telemetry system according to claim 6, which includes:
- an update interval rate and network throughput being fixed regardless of the number of network nodes.
8. The telemetry system according to claim 2, which includes:
- a respective node including a transmitter and a receiver; and
- the respective node simultaneously transmitting and receiving.
9. The telemetry system according to claim 8, which includes a filter adapted to an approximation of the channel between the respective node's transmitter and receiver.
10. The telemetry system according to claim 8, which includes said receiver being adapted for receiving with mitigated self-interference during transmission.
11. The telemetry system according to claim 9, which includes an estimation function including:
- a transmitter-to-receiver intranode channel providing an output;
- said adaptive filter having the signal destined for transmission as a reference input;
- a summer receiving outputs from said receiver channel and said adaptive filter;
- said summer providing an error signal as a feedback output to said adaptive filter; and
- said adaptive filter being adjusted so as to minimize error signal.
12. The telemetry system according to claim 9, which includes a receiver signal isolation function including:
- an estimated intranode transmitter-to-receiver channel filter having the signal destined for transmission as an input from the transmitter and providing an output that is the estimated transmitter signal as perceived by the receiver;
- a summer receiving inputs from said adaptive filter and the receiver signal output that are synchronized in time; and
- said summer providing an output comprising the received signal with reduced transmitter signal content.
13. The telemetry system according to claim 2, which includes:
- said transmitter and said receiver operating in the same channel;
- said received signals being isolated from each other;
- said receiver being configured to receive with minimized self-interference during transmission; and
- said control system including a function for favoring a desired signal over an interferer signal.
14. The telemetry system according to claim 2 which includes:
- said control system function coordinating network timing whereby a desired signal precedes in time an anticipated, overlapping interferer signal creating an interference-free time period at a node for reception of a portion of the desired signal, thereby allowing the node receiver to lock onto the desired signal.
15. The telemetry system according to claim 2, which includes:
- multiple receivers within a node with signal outputs which are phased and combined in such a manner to form a phased array that gives rise to directional discrimination of incoming signals to minimize interference from an undesired node transmissions arriving from another direction.
16. The telemetry system according to claim 2, which includes:
- multiple transmitters within a node with output signals phased in such a manner so as to propagate outgoing signals in one direction only and minimizing interference at another node.
17. The telemetry system according to claim 2, which includes:
- said directional receivers being adapted to suppress undesired interfering signals arriving at the receiver from one direction, while receiving desired signals from another direction.
18. A method of transmitting acoustic telemetry signals in a well including a wellbore structure extending subsurface downwardly from the surface, which method includes the steps of:
- defining with said structure a linear/daisy-chain network;
- providing multiple network nodes positioned along said structure;
- transmitting said signals in signal sets comprising orthogonal (low interference) signal sets assigned to network nodes to reduce inter-node interference;
- pre-defining node separations and/or transmission power levels;
- predefining tolerable interference ranges for said receivers;
- maintaining interference at receiver locations within tolerable, predefined ranges through signal propagation attenuation;
- providing a sensor associated with one or more of said nodes and adapted for providing output comprising signal data corresponding to an operating, status, or wellbore condition;
- providing a transmitter associated with one of said nodes for propagating said signal data between nodes;
- providing a receiver associated with one of said nodes;
- receiving with said receiver signals from other nodes;
- receiving said signal data with said multiple network nodes; and
- transmitting telemetry signals across multiple network links simultaneously.
19. The method according to claim 18, which includes the additional step of:
- providing said well with a node located at said surface and a bottom hole assembly (BHA) located at the bottom of said well;
- providing sensors configured to monitor operating conditions near or at the BHA;
- generating said signals with data corresponding to said BHA operating stations;
- transmitting said BHA operating condition data signals to said surface node; and
- exporting said BHA operating condition data signals to a remote data processing system configured to monitor operating conditions at said well.
20. The method according to claim 18, which includes the additional step of generating said telemetry signals using a signal type chosen from among the group comprising: acoustic; electromagnetic (EM); mud pulse (MP); and optical.
Type: Application
Filed: Mar 17, 2014
Publication Date: Sep 18, 2014
Applicant: Xact Downhole Telemetry, Inc. (Calgary)
Inventor: John-Peter van Zelm (Calgary)
Application Number: 14/215,617
International Classification: E21B 47/12 (20060101); E21B 47/14 (20060101);