Borehole Sonic Reflection Imaging for Far-Field Dip Determination
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Solution Overview
Problem
Current logging tools are unable to accurately determine true dip angles both in the near-field and far-field from a wellbore, limiting the ability to provide suitable images for dip analysis at distances away from the wellbore.
Innovation Solution
The use of borehole sonic logging tools with transmitters and receivers to gather full-waveform data, process it to generate a structure-guided velocity model, and create reflection images that accurately determine dip angles up to 100 feet or more from the wellbore, using iterative processes to refine the model based on relative dip angles and geological structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current logging tools are used to measure dip angle at the wellbore wall, then dip angle measurement is possible, but dip angles at distances away from the wellbore cannot be provided
Solution Approach 1:
The patent segments the measurement problem into near-field and far-field components by using multiple receiver positions at different distances from the wellbore. Each receiver captures acoustic waves that interact with formation features at its specific distance, enabling dip angle measurement across multiple distance zones simultaneously through the full-waveform inversion process.
Solution Approach 2:
The patent transitions from traditional 2D wellbore-wall measurement to a 3D far-field measurement capability by introducing receivers at multiple radial distances from the wellbore axis. This dimensional expansion allows the system to resolve dip angles at various distances from the wellbore, creating a volumetric understanding of formation geometry rather than局限于 surface-level measurements.
2Adaptability or versatility
If other logging tools are used to provide measurements at larger distances from the wellbore, then far-field measurement is possible, but images suitable for dip analysis are not provided
Solution Approach 1:
The patent makes the acoustic logging tool multi-functional by using the same full-waveform acoustic data for both far-field measurement and high-quality dip analysis imaging. The full-waveform inversion process simultaneously extracts both the acoustic wave propagation characteristics needed for distance measurement and the reflection characteristics needed for precise dip angle imaging, eliminating the need for separate specialized tools.
Solution Approach 2:
The patent employs an iterative full-waveform inversion process where the initial model is continuously refined using feedback from the acoustic waveforms. The inversion algorithm adjusts the velocity model and dip angle parameters iteratively until the simulated waveforms match the recorded waveforms, ensuring that the final image quality and measurement precision are optimized based on the actual acoustic data.
3Measurement precision
If full-waveform inversion is used to create velocity models and reflection images, then dip angle determination is improved, but processing complexity increases
Solution Approach 1:
The patent performs preliminary actions by pre-processing the acoustic waveforms to separate direct waves from reflected waves, and by initial velocity model construction before the main inversion process. These preliminary steps organize the complex data into manageable components and establish an initial model state, reducing the computational burden during the iterative inversion process and making the overall system more manageable.
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
Enables accurate determination of dip angles in both near-field and far-field, allowing for more precise formation imaging and velocity modeling, enhancing reservoir characterization and monitoring.
Implementation Method 1
emitting sound waves from the one or more transmitters; receiving sound waves at the one or more receivers to obtain borehole sonic data
Implementation Method 2
separating up-going arrivals in the borehole sonic data from down-going arrivals in the borehole sonic data; generating a first reflection image based at least on the borehole sonic data
Data Source
AI summary
The present disclosure relates to borehole sonic logging and, more particularly to, improved reflection imaging of formation structures away from the wellbore. A method for borehole sonic reflection imaging may comprise: disposing a borehole sonic logging tool in a wellbore, wherein the borehole sonic logging tool comprises one or more transmitters and one or more receivers; emitting sound waves from the one or more transmitters; receiving sound waves at the one or more receivers to obtain borehole sonic data; separating up-going arrivals in the borehole sonic data from down-going arrivals in the borehole sonic data; generating a first reflection image based at least on the borehole sonic data; estimating a relative dip angle of a formation bed from the first reflection image; generating an updated velocity model based at least on the relative dip angle; and generating an updated reflection image based at least on the updated velocity model.