Tuned Pulse Generation for Downhole Logging Attenuation
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Solution Overview
Problem
Downhole logging tools face challenges in generating sufficient power to produce effective pulses in highly attenuative fluids, such as drilling mud, which limits the energy of echo responses needed for accurate well and reservoir information collection.
Innovation Solution
The implementation of a tuned pulse generation system that optimizes pulse frequencies and response characteristics, allowing for improved echo responses without the need for large power increases, using a digital control system coupled with a switching amplifier to generate and transmit digital pulses that approximate the desired tuned pulses, specifically designed for use in downhole logging tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power pulse excitations are used to overcome fluid attenuation, then echo response energy is improved, but power supply requirements and device complexity increase
Solution Approach 1:
The patent changes the parameters of the pulse excitation by using optimized wavelet functions with specific frequency content and duration. Instead of simply increasing power, the system modifies the temporal and spectral characteristics of the pulse to maximize energy transfer to the formation while minimizing losses in attenuative fluids, thereby achieving effective echo responses without proportionally increasing power supply requirements
Solution Approach 2:
The patent employs resonant frequency excitation where the pulse frequency is tuned to match the natural resonant frequency of the formation-casing-fluid system. This resonant coupling amplifies the echo response through constructive interference and energy accumulation, allowing effective logging with reduced input power compared to broadband high-power excitation
2Power
If high power pulse excitations are used to overcome fluid attenuation, then echo response energy is improved, but energy consumption increases
Solution Approach 1:
The system optimizes the energy efficiency by carefully selecting pulse duration and frequency content parameters. The wavelet-based pulse design concentrates energy in the frequency range most effective for formation interaction, reducing energy wasted in frequencies that are heavily attenuated by the drilling fluid, thus improving echo response energy per unit of energy consumed
Solution Approach 2:
By exciting the system at its resonant frequency, the patent achieves maximum energy transfer efficiency. The resonant oscillations naturally amplify the response signal through constructive interference over multiple cycles, extracting more useful echo energy from the same input energy budget compared to non-resonant high-power pulses
3Measurement precision
If pulse frequency is increased to improve resolution, then measurement precision is improved, but energy attenuation in fluid increases
Solution Approach 1:
The patent employs wavelet transform analysis to identify and excite specific frequency components that provide optimal balance between resolution and penetration. By transforming the pulse into the frequency domain, the system can selectively emphasize frequencies that offer the best compromise: high enough for formation detail resolution but not so high as to be completely attenuated by the drilling fluid before reaching the formation
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 solution enhances power efficiency and improves echo responses in highly attenuative fluids, enabling more accurate downhole data collection while reducing the need for larger power supplies, thus optimizing the performance of downhole logging tools.
Implementation Method 1
One example logging technique uses high power pulse excitations from and echo/reflection detections at a downhole tool to obtain well and reservoir information
Implementation Method 2
A method includes determining a series of digital pulses having a frequency response that approximates a frequency response of a tuned pulse to be transmitted from a transmission element. An analog output at a switching amplifier corresponding to the series of digital pulses may be generated
Data Source
AI summary
An example method includes determining a frequency response of a tuned pulse to be transmitted from a transmission element. A matching frequency envelope corresponding to a frequency envelope of the frequency response may be determined. A time domain signal corresponding to the matching frequency envelope may be determined. A series of digital pulses corresponding to the time domain signal may be determined. An analog output at a switching amplifier corresponding to the series of digital pulses may be generated. A transmission element may be excited with the analog output.