Downhole Acoustic Tool Parameter Optimization
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Solution Overview
Problem
In downhole environments, multiple formation parameters are often not measured simultaneously, making it difficult to identify optimized values for these parameters, especially when they similarly affect theoretical slownesses, leading to ambiguity in determining accurate parameter values.
Innovation Solution
The method involves using distinct acoustic modes with different sensitivities to variations in formation shear slowness and drilling fluid slowness, performing joint inversions of measured slownesses to identify optimized parameter values through non-linear squares fitting analysis, comparing theoretical and measured slownesses to find the best-fit agreement, and using a processor to determine optimized values for parameters like formation shear slowness and drilling fluid slowness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple formation parameters are measured using conventional single acoustic mode methods, then measurement coverage is improved, but measurement precision deteriorates due to parameter coupling and ambiguity
Solution Approach 1:
The invention segments the measurement process by using multiple distinct acoustic modes (e.g., compressional, shear, Stoneley) that are differentially sensitive to different formation parameters. Each acoustic mode provides a separate measurement pathway that isolates specific parameter effects, thereby resolving the ambiguity that occurs when trying to measure multiple parameters simultaneously with a single method.
Solution Approach 2:
The invention adds the dimension of acoustic mode diversity to the measurement system. Instead of relying on a single acoustic mode, the system utilizes multiple acoustic modes with different sensitivity characteristics to the same formation parameters. This dimensional expansion allows for better parameter discrimination and reduced measurement ambiguity.
2Measurement precision
If distinct acoustic modes with different sensitivities are used, then parameter identification accuracy is improved, but device complexity increases
Solution Approach 1:
The downhole tool is designed with multi-functionality, where a single tool assembly can generate and detect multiple acoustic modes (compressional, shear, Stoneley, etc.). The same physical apparatus serves multiple measurement functions by exciting and sensing different acoustic wave types, thereby reducing the need for separate dedicated tools for each acoustic mode while maintaining high measurement precision.
3Measurement precision
If joint inversion of multiple acoustic modes is performed, then optimized parameter values are identified more accurately, but processing time increases
Solution Approach 1:
The system performs preliminary actions by pre-calculating sensitivity kernels and response functions for different acoustic modes and formation parameters. This pre-computation allows the joint inversion process to converge faster by starting with optimized initial guesses and reduced computational complexity, thereby maintaining high accuracy while reducing the actual field processing time.
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 more accurate analysis of acoustic measurements by distinguishing between the effects of formation shear slowness and drilling fluid slowness, providing a clear identification of optimized parameter values that minimize the difference between measured and theoretical slownesses, even when multiple unmeasured parameters exist.
Implementation Method 1
transmitting a signal from a transmitter into a formation and receiving the signal at a receiver spaced from the transmitter
Data Source
AI summary
Methods and apparatus to optimize parameters in a downhole environment are described. An example downhole tool includes a transmitter to transmit a signal into a subterranean formation and one or more receivers to receive at least a portion of the acoustic signal. The downhole tool also includes a processor configured to determine slownesses of different acoustic modes at a frequency of the signal received. Each of the slownesses is associated with a first parameter and a second parameter. The different acoustic modes have substantially different sensitivities to at least one of the first parameter or the second parameter. The processor to invert the determined slownesses of the different acoustic modes to determine an optimized value of the first parameter and an optimized value of the second parameter.