Split Inversion for NMR Data Transmission
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Solution Overview
Problem
The transmission speed of communication channels from downhole tools to surface computing devices is limited, making it impractical to transmit raw NMR data for real-time evaluation of subsurface formations during drilling.
Innovation Solution
A split inversion process is performed on NMR data captured downhole, where a first inversion is done downhole to determine spectrum coefficients, and these coefficients are then compressed and transmitted to the surface for a second inversion, allowing for efficient data transmission and real-time analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If raw NMR data is transmitted from downhole to surface, then measurement precision is improved, but transmission time increases beyond real-time requirements
Solution Approach 1:
The patent extracts only the essential spectral coefficients from the complete NMR echo train data at downhole location. Instead of transmitting all raw echo data points, only the extracted spectral coefficients are sent to surface, reducing transmission volume while preserving the critical information needed for formation evaluation.
Solution Approach 2:
The NMR data processing is segmented into two stages: first, rapid extraction of spectral coefficients at downhole using simplified algorithms; second, comprehensive inversion and analysis at surface using full computational resources. This segmentation allows real-time coefficient transmission while maintaining option for detailed post-processing.
2Loss of information
If complete NMR echo train data is transmitted, then information completeness is improved, but data volume exceeds communication channel capacity
Solution Approach 1:
The patent extracts only the essential spectral coefficients from the complete NMR echo train data at downhole location. Instead of transmitting all raw echo data points, only the extracted spectral coefficients are sent to surface, reducing transmission volume while preserving the critical information needed for formation evaluation.
Solution Approach 2:
The spectral coefficients serve as a compressed representation or copy of the essential NMR information. Rather than transmitting the full echo train, a simplified mathematical representation is created and transmitted, which can be used to reconstruct the necessary formation parameters without needing the original complete dataset.
3Speed
If real-time processing is implemented downhole, then transmission speed is improved, but computational complexity increases
Solution Approach 1:
The NMR data processing is segmented into two stages: first, rapid extraction of spectral coefficients at downhole using simplified algorithms; second, comprehensive inversion and analysis at surface using full computational resources. This segmentation allows real-time coefficient transmission while maintaining option for detailed post-processing.
Solution Approach 2:
Different processing quality levels are applied at different locations: downhole performs only essential spectral coefficient extraction with limited computational resources, while surface performs complete inversion and detailed analysis with unlimited computational resources. Each location performs only the processing appropriate to its capabilities.
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 enables the transmission of NMR data over low-bandwidth channels while still allowing for accurate reconstruction of echoes and analysis of subsurface formations, facilitating real-time decision-making during drilling operations.
Implementation Method 1
Nuclear magnetic resonance (NMR) has two main experiments in oil field downhole usage. The first main experiment is to assess T1 buildup of magnetization. The main second experiment is to observe the decay of magnetization once it has been excited, in which the decay has a time constant of T2.
Implementation Method 2
T1 is the time constant for the bulk nuclear spin, the magnetization, to align with the magnetic field.
Data Source
AI summary
Some implementations transmit nuclear magnetic resonance (NMR) data between downhole tools and surface-based computers. A method may include generating a first vector in which each entry includes a spectrum coefficient associated with NMR echo signals. The method may include generating a cumulative sum vector in which each entry includes a sum including a spectrum coefficient of a corresponding entry in the first vector plus any spectrum coefficients of any entries that precede the first corresponding entry in the first vector. The method may include down sampling the cumulative sum vector to form a down-sampled vector including a subset of the cumulative sum vector. The method may include generating a compressed vector in which each entry includes a difference of a corresponding entry in the down sampled vector and any entry directly preceding the corresponding entry in the down sampled vector and transmitting the compressed vector over a communication channel.