Downhole Acoustic Telemetry Timing via Pre-configured Constants
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Solution Overview
Problem
Acoustic telemetry in drillstrings faces challenges due to high latency and bandwidth limitations, leading to delayed data delivery and inaccurate inter-node differential measurements, exacerbated by temperature differentials and continuous network operation, which complicates clock synchronization and time-of-measurement alignment.
Innovation Solution
A downhole linear repeater relay network timing system that controls time constraints using pre-configured constants, allowing surface receivers to calculate relative timing offsets and synchronize sensor data acquisition across nodes, eliminating the need for time-of-measurement overhead and network synchronization signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple acoustic transceiver nodes are used to boost telemetry signals, then signal attenuation and range limitations are overcome, but latency increases due to the time required for each node to receive and relay data packets
Solution Approach 1:
The system performs preliminary actions by pre-configuring timing constants and synchronization parameters at each node before data transmission begins. Each node is pre-synchronized to specific time slots and frequencies, allowing them to relay data packets without requiring real-time clock synchronization or additional synchronization signals during operation. This eliminates the latency that would otherwise be caused by clock alignment procedures.
2Measurement precision
If time-of-measurement information is included in transmitted packets, then accurate timing alignment is achieved, but bandwidth is consumed by overhead information
Solution Approach 1:
The invention extracts the timing synchronization function from the data transmission protocol itself. Instead of embedding time-of-measurement information within each data packet (which would consume bandwidth), the system separates synchronization into a preliminary configuration phase where timing constants are established, and then uses these pre-configured constants for all subsequent transmissions. This removes the overhead of time-stamping every packet while maintaining precise timing alignment.
3Measurement precision
If downhole clocks are highly accurate, then time-of-measurement alignment is maintained, but temperature differentials and continuous operation make synchronization problematic
Solution Approach 1:
The system performs clock synchronization as a preliminary action during system initialization or configuration, before the harsh downhole environment causes significant drift. Timing constants and synchronization parameters are established when temperature differentials are minimal or stable. Once configured, each node operates independently using these pre-configured constants, eliminating the need for continuous synchronization that would be vulnerable to temperature-induced drift.
4Loss of time
If pre-configured timing constants are used, then latency is reduced and timing is maintained without overhead, but the system requires careful initial configuration
Solution Approach 1:
The system implements self-service by having each node automatically apply the pre-configured timing constants and synchronization parameters to its operations. Once the master controller configures the network with timing constants, each node independently uses these constants without requiring further intervention or complex coordination. This self-service approach minimizes operational complexity while maintaining the low-latency benefits of pre-configured timing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces latency, enhances data throughput, and maintains accurate timing without costly overhead, allowing for agile timing adjustments and synchronized sensor data acquisition, improving the correlation of downhole and uphole events.
Implementation Method 1
an acoustic transmitter is preferentially placed near the BHA, typically near the drill bit where the transmitter can gather certain drilling and geological formation data, process this data, and then convert the data into a signal to be transmitted up-hole
Implementation Method 2
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
Data Source
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AI summary
A downhole repeater network timing system for a drilling rig including a drillstring extending subsurface downwardly from a surface wellhead. The system includes a node located at the drillstring lower end and including a sensor adapted for providing a signal data set output corresponding to downhole drilling conditions. Multiple nodes are located downhole between the Bottom Hole Assembly (BHA) and the wellhead and are associated with the drillstring. The nodes are adapted for receiving and transmitting the signals. The timing control system is adapted for controlling all times within a timeframe according to pre-configured constants known to all nodes. A downhole low rate linear repeater network timing method uses the system.