Downhole Repeater Network Timing Control for Acoustic Telemetry
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Solution Overview
Problem
Acoustic telemetry systems in drilling and production wells face challenges due to high latency and signal attenuation, leading to low data rates and inaccurate timing measurements, which are exacerbated by bandwidth limitations and temperature differentials across the network.
Innovation Solution
A repeater network with controlled timing is implemented using pre-configured constants such as guard time, packet transmission time, and sensor acquisition time, allowing for accurate computation of surface time-of-measurement and synchronization without the need for additional overhead signals, enabling precise timing across all nodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If multiple acoustic transceiver nodes are used to overcome signal attenuation, then the transmission range is extended, but the latency increases due to the time required for each node to receive and relay data packets
Solution Approach 1:
The system pre-configures constant timing parameters (guard time, relay time, packet transmission time) at each node before data transmission begins. This preliminary setup allows nodes to immediately forward packets with predetermined delays, eliminating the need for real-time processing decisions and reducing overall latency while maintaining extended transmission range through multiple nodes
2Measurement precision
If time-of-measurement information is included in transmitted data packets, then accurate timing measurements can be obtained, but the data rate decreases due to increased overhead
Solution Approach 1:
The system extracts timing measurement functionality from the data packet payload by using predetermined constant timing parameters configured at each node. This separates the timing measurement function from data transmission, allowing accurate timing to be obtained without adding time-of-measurement information to packets, thereby maintaining high data rates while achieving precise timing measurements
3Measurement precision
If downhole clocks are synchronized to account for temperature differentials, then accurate timing across nodes can be achieved, but the system complexity and cost increase
Solution Approach 1:
The system changes the approach from active clock synchronization to using predetermined constant timing parameters that are configured once and remain stable. By using constants for guard time, relay time, and packet transmission time, the system achieves accurate inter-node timing without requiring complex temperature compensation or continuous synchronization mechanisms, thereby reducing system complexity while maintaining measurement precision
Data Source
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.