Self-Calibrated Acoustic Assembly for Accurate Borehole Fluid Properties
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Solution Overview
Problem
Conventional methods for determining acoustic properties of downhole fluids are highly sensitive to drilling fluid properties and suffer from inaccuracies due to variations in transducer sensitivity, fluid attenuation, and acoustic impedance mismatch, leading to errors in sound velocity and attenuation coefficient measurements.
Innovation Solution
A method using an acoustic assembly with multiple reflectors and transducers to transmit pulses and measure reflections, solving simultaneous equations to determine acoustic properties independently of transducer intensity, employing a self-calibration technique to mitigate transducer sensitivity and fluid attenuation effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional time of flight method is used to determine sound speed, then the measurement process is simple, but the measurement precision is poor due to sensitivity to transducer variations and fluid attenuation
Solution Approach 1:
The acoustic assembly is segmented into multiple transducers (at least two) positioned at different known locations, with each transducer independently measuring acoustic properties. This segmentation allows the system to overcome the limitations of single-transducer methods by providing multiple independent measurements that can be combined to eliminate sensitivity variations and attenuation effects.
Solution Approach 2:
Acoustic reflectors are introduced as intermediary elements to create known reflection paths between transducers. These reflectors serve as mediators that enable the measurement of acoustic properties through reflected signals, providing additional measurement pathways that help eliminate the effects of transducer sensitivity variations and fluid attenuation.
2Reliability
If single transducer method is used, then the device complexity is low, but the reliability is poor due to transducer sensitivity variations
Solution Approach 1:
The system uses at least two transducers positioned at different known locations, with each transducer independently measuring acoustic properties. This segmentation into multiple measurement points eliminates the reliability issues of single-transducer methods by providing redundant measurements that can be combined to cancel out sensitivity variations.
Solution Approach 2:
The system employs a feedback mechanism where the measured acoustic properties from multiple transducers are used to calculate and apply correction factors. The processing system analyzes the signals from multiple transducers and reflectors, computes the acoustic properties while accounting for transducer sensitivity variations, and provides self-calibration to ensure measurement consistency.
3Measurement precision
If conventional processing is used, then the processing method is simple, but the measurement precision is poor due to fluid attenuation effects
Solution Approach 1:
Acoustic reflectors are used as intermediary elements to create known reflection paths through the fluid. By measuring the acoustic properties of these known paths and comparing them to the actual measurements, the system can calculate and compensate for fluid attenuation effects, thereby improving measurement precision.
Solution Approach 2:
The system replaces simple time-of-flight mechanical measurement with a more sophisticated signal processing approach that uses multiple transducers and reflectors. The processing system substitutes direct measurement with a calculation-based method that solves for acoustic properties while accounting for attenuation, effectively replacing simple mechanics with a more robust computational approach.
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
Accurately measures sound velocity, acoustic impedance, and attenuation coefficient of downhole fluids in situ, reducing errors to less than 3% and enabling more precise borehole fluid characterization and formation evaluation.
Implementation Method 1
transmitting a plurality of acoustic pulses through the fluid
Implementation Method 2
measuring values for at least one wave property measured for reflections of the plurality of pulses
Data Source
AI summary
Methods, systems, and devices for determining an acoustic parameter of a downhole fluid using an acoustic assembly. Methods include transmitting a plurality of pulses; measuring values for at least one wave property measured for reflections of the plurality of pulses received at at least one acoustic receiver, including: a first value for a first reflection traveling a first known distance from a first acoustically reflective surface having a first known acoustic impedance, a second value for a second reflection traveling a second known distance substantially the same as the first known distance from a second acoustically reflective surface having a second known acoustic impedance, and a third value for a third reflection traveling a third known distance from a third acoustically reflective surface having a third known acoustic impedance substantially the same as the second acoustic impedance; and estimating the acoustic parameter using the values.