Acoustic Sand Detection in Wells Using Signal Discrimination
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Solution Overview
Problem
Current methods for detecting sand production zones in wells suffer from low sensitivity, inability to accurately count sand particles, and lack of information on the location of sand production zones, leading to potential damage and increased costs.
Innovation Solution
A method involving the measurement and processing of acoustic signal amplitudes to discriminate peak shapes corresponding to solid particle impacts, allowing for accurate counting and identification of sand production zones by distinguishing between impacts from sand and other sources like gas or air bubbles, and differentiating between sand carried by fluid flow from the formation and that moving within the wellbore.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fiber optic acoustic sensors are used to detect sand production, then the system can identify sand presence through acoustic signals, but the sensitivity is reduced due to additional screen from the well medium
Solution Approach 1:
The patent introduces a reference sensor that measures acoustic signals without being exposed to sand particles, serving as an intermediary reference point. This reference measurement allows the system to compensate for the attenuating effect of the well medium screen, thereby maintaining sensitivity while enabling sand detection through comparison with the reference signal
Solution Approach 2:
The system changes the measurement parameters by comparing acoustic signal characteristics (amplitude, frequency spectrum) between the sand-exposed sensor and the reference sensor. By analyzing parameter differences rather than absolute values, the system overcomes the sensitivity reduction caused by the well medium
2Reliability
If broadband signal detection with frequency filtration is used, then sand production can be identified through spectral analysis, but the accuracy in counting sand particles is reduced
Solution Approach 1:
The patent segments the acoustic signal analysis into distinct frequency bands and temporal patterns. By dividing the broadband signal into specific frequency ranges and analyzing the temporal characteristics of impacts, the system can distinguish between individual sand particles and other sources, improving counting accuracy while maintaining sand production identification capability
Solution Approach 2:
The system performs preliminary characterization of sand particle impact signatures before counting. By establishing reference patterns of what sand particle impacts look like across different frequency bands, the system can more accurately identify and count individual particles during actual measurement, rather than relying solely on threshold-based detection
3Reliability
If acoustic noise thresholding is used to detect sand, then sand detection is based on noise increase, but information about sand producing zone location and amount is lost
Solution Approach 1:
The patent adds spatial and quantitative dimensions to the acoustic detection by using multiple sensors positioned at different depths in the wellbore. This multi-dimensional sensor array allows the system to not only detect sand presence through noise thresholding but also to locate the producing zone by identifying which sensors detect the signals and to estimate quantity by analyzing signal strength and duration across the sensor network
4Reliability
If a single acoustic sensor is used to detect sand impacts, then the system can identify sand presence, but the ability to distinguish sand from other impacting objects is reduced
Solution Approach 1:
The patent merges multiple sensing capabilities into a unified detection system. By combining acoustic sensors that detect impact sounds with additional sensors (such as vibration sensors or pressure sensors) and integrating their outputs, the system creates a multi-parameter detection signature that enables more reliable discrimination between sand particles and other impacting objects like gas bubbles or mechanical vibrations
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
Enhances the reliability of sand detection by accurately identifying and counting solid particles and determining their production zones, reducing the risk of well damage and operational costs.
Implementation Method 1
a method comprising the stages at which acoustic signals are registered using an acoustic sensor; the acoustic signal contains information about impacts of solid particles with the acoustic sensor
Data Source
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AI summary
This invention relates to the petroleum industry. More particularly, this invention pertains to the method of detecting zones of solids (sand or proppant) production in a well where the solids are carried up by fluid and gas flows. To implement the method, at least one well operating regime is established, which is characterised by the presence of fluid flow carrying solid particles either along the wellbore or in one or more formations. At least one instrument for objective measurements of acoustic signal amplitude is run in or pulled out of the well either at a constant speed or stopping at stations. Acoustic signal amplitude is measured either at a station or during running in or pulling out of the well using at least one instrument for objective measurements of acoustic signal amplitude. The acoustic signal amplitude measurement data obtained in the well are processed, detecting amplitude peaks in the registered acoustic signal. At each depth, the peak shapes resulting from the measurements are compared with the reference ones and only those peaks that correspond to impacts of solid particles are discriminated. The solid particles are counted and the zone of solids production in the wellbore is identified. During downhole logging on a down pass or on an up pass, the number of solid particles is estimated at one-second intervals. During downhole logging at stations the number of solid particles is estimated for each station. The duration of a measurement at a station is 10 seconds or longer. The distance between stations is equal to the length of the instrument for objective measurement of acoustic signal amplitude. Acoustic signal amplitude is measured simultaneously with three acoustic signal amplitude measuring instruments with the distance between stations being three times longer than the length of the instrument for objective measurement of acoustic signal amplitude. The instrument for objective measurement of acoustic signal amplitude is run in or pulled out at a constant speed of maximum six meters per second for the instrument one metre long, using additional rubber centralisers. For monitoring of solid particles and selection of an optimal operating regime, an additional solid particle surface detector is installed. Utilisation of this invention will enhance the accuracy of solid particles detection in a well. 7 subclaims, 13 figs.