Bottom Hole Assembly Tool Bus With Single Electrical Contact
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Solution Overview
Problem
Conventional tool bus systems in bottom hole assemblies (BHAs) face limitations in communication speed, noise interference, and reliability due to inconstant impedance and excessive complexity, which restrict the number of nodes and length of the drillstring, and fail to provide a clean electromagnetic environment for advanced downhole tools.
Innovation Solution
A high-performance tool bus system with a transmission line having constant characteristic impedance, utilizing a single electrical contact and common mode choke to stabilize bus return currents, and implementing a multi-layer bus architecture with separate primary and secondary buses operating at different speeds to support higher communication speeds and increased node count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional tool bus systems are used with multiple electrical contacts and complex wiring, then the system can support basic communication functions, but the communication speed is limited and noise interference increases
Solution Approach 1:
The BHA is divided into multiple segments connected end-to-end, with each segment containing isolated tools. The tool bus is segmented into multiple isolated sections, with each segment having its own local bus. This segmentation allows for higher communication speeds within each isolated segment while reducing noise interference between segments.
Solution Approach 2:
A single electrical contact (SEC) acts as an intermediary component at each segment joint to convey bus signals between adjacent segments. The SEC simplifies the electrical connection interface while maintaining signal integrity, reducing complexity compared to multiple contact points.
2Reliability
If conventional tool bus systems are used with inconstant impedance, then the system structure is simpler, but communication reliability deteriorates and noise interference increases
Solution Approach 1:
The transmission line impedance is controlled to be constant along its length, unlike conventional systems with inconstant impedance. This parameter control improves signal integrity and communication reliability by preventing signal reflections and distortion, while the complexity is managed through standardized transmission line design.
Solution Approach 2:
Instead of accepting inconstant impedance as a natural consequence of simple wiring, the invention inverts the approach by deliberately designing the transmission line to maintain constant impedance. This requires careful engineering of the transmission line geometry and materials, but results in superior communication reliability.
3Object-affected harmful factors
If conventional tool bus systems allow bus return currents to flow through multiple paths including the drillstring, then the system is more flexible, but electromagnetic interference increases and noise levels rise
Solution Approach 1:
The bus return current path is extracted and isolated from the drillstring body. Instead of allowing return currents to flow through multiple paths including the drillstring, the invention confines return currents to a dedicated return conductor within the transmission line. This extraction of the return path eliminates electromagnetic interference with the drillstring and other tools.
Solution Approach 2:
The invention converts the potential harm of uncontrolled return currents flowing through the drillstring into a benefit by providing a dedicated return path. This dedicated path prevents electromagnetic interference while maintaining electrical continuity, turning what could be a source of noise into a controlled, beneficial feature.
4Device complexity
If conventional tool bus systems are used with single electrical contacts, then the device complexity is reduced, but the number of supported nodes and drillstring length are limited
Solution Approach 1:
The invention extends the tool bus across multiple segments in a distributed architecture, adding the dimension of segmental expansion. Each segment can contain multiple nodes, and segments can be connected in series to achieve arbitrary drillstring lengths. The single electrical contact at each joint enables this dimensional extension without increasing contact complexity.
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
The solution achieves communication speeds an order of magnitude greater than conventional systems, reduces noise interference, and allows for a larger number of nodes and longer drillstring lengths without compromising performance, creating a cleaner electromagnetic environment for advanced downhole tools.
Implementation Method 1
A common mode choke on the transmission line is configured to constrain bus return currents to the transmission line
Implementation Method 2
a single electrical contact (SEC) is provided at the joint and is configured to convey a bus signal across the joint to an adjacent segment of the bottom hole assembly
Data Source
AI summary
A tool bus spans multiple segments of a bottom hole assembly (BHA) is implemented as a transmission line with only a single electrical contact (SEC) across joints of adjacent segments. A common mode (CM) choke on the transmission line promotes return currents to pass through the transmission line as opposed to through parallel return paths and stabilizes the characteristic impedance on the transmission line. The tool bus uses a two-layer bus with a first layer that is used to communicate across segments and a second layer that is used to communicated among nodes within one segment. A primary node is used to link the primary bus and the secondary bus. A CM choke may be used at the connection between the primary node and the primary bus, at the connection between the primary node and the secondary bus, and/or at the connection between the secondary bus and a secondary node.