Wellbore Droppable Object Positioning Using Pressure Pulse Reflections
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Solution Overview
Problem
Conventional cementing operations face challenges in accurately monitoring the position of droppable objects like wiper plugs and drillpipe darts within a casing string due to uncertainties such as borehole rugosity, pump rate fluctuations, and deviations from ideal geometry, leading to potential inaccuracies in displacement volume calculations.
Innovation Solution
A method and system that utilize pressure pulses generated when cementing plugs pass through regions of varying inner cross-sectional dimensions in the casing, combined with cepstral analysis of high-frequency pressure data to determine the position of droppable objects in real-time by processing pressure pulse reflections and using a casing tally for correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional displacement volume calculation methods are used, then the calculation process is simple, but the positioning accuracy of droppable objects deteriorates due to uncertainties in borehole geometry and pump rate fluctuations
Solution Approach 1:
The patent replaces mechanical displacement volume calculation methods with acoustic pressure pulse detection. Pressure transducers detect acoustic waves generated when droppable objects pass through casing collars, and cepstral analysis processes these signals to determine object positions. This substitution of mechanical measurement with acoustic sensing resolves the contradiction by providing high positioning accuracy without requiring complex geometric modeling or pump rate monitoring.
Solution Approach 2:
The patent introduces pressure pulses as an intermediary medium to transmit information about droppable object positions. When objects pass through casing collars, they generate pressure pulses that propagate through the cement slurry and are detected by transducers. This intermediary acoustic signal carries positioning information independently of borehole geometry uncertainties or pump rate variations, achieving accurate measurement without the drawbacks of conventional methods.
2Ease of operation
If real-time monitoring of droppable objects is implemented, then operational decision-making is improved, but the complexity of the monitoring system increases
Solution Approach 1:
The patent implements a feedback system where pressure transducers continuously monitor acoustic signals from droppable objects, and cepstral analysis processes these signals in real-time to provide position information. This feedback loop enables operators to make informed decisions about cementing operation progress, such as when to stop pumping or when plugs have reached target depths, thereby improving ease of operation through real-time information.
Solution Approach 2:
The patent replaces complex mechanical monitoring systems with acoustic sensing and signal processing. By using pressure transducers to detect acoustic waves and applying cepstral analysis to extract position information, the system achieves real-time monitoring capabilities with relatively simple hardware, resolving the contradiction between operational ease and system complexity.
3Measurement precision
If displacement volume calculations are performed based on ideal geometry assumptions, then the calculation process is simplified, but the accuracy deteriorates due to borehole rugosity and casing geometry deviations
Solution Approach 1:
The patent replaces mechanical displacement volume calculations based on ideal geometry with acoustic pressure pulse detection. This substitution eliminates the need to account for borehole rugosity and casing geometry deviations in calculations, as the acoustic method directly measures object positions independent of geometric assumptions. The result is accurate positioning information obtained rapidly during the cementing operation.
Solution Approach 2:
The patent uses pressure pulses as an intermediary to directly sense droppable object positions without relying on geometric models. The acoustic waves provide direct measurement information that bypasses the need for complex geometric calculations, thereby improving accuracy while minimizing time loss during the cementing operation.
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 real-time monitoring and accurate positioning of droppable objects, allowing operators to make informed decisions during cementing operations, ensuring uniform cement sheath placement and preventing fluid contamination.
Implementation Method 1
A droppable object is placed inside the casing string. A fluid is then pumped behind the droppable object, causing the droppable object to travel through the interior of the casing string and pass through the at least one region with a negative or positive change of inner cross-sectional dimension, thereby generating a pressure pulse.
Implementation Method 2
The pressure data are then processed mathematically by obtaining the pressure pulses, pulse reflections or both, and the position of the droppable object is determined.
Data Source
AI summary
The position of a droppable object (e.g., a cementing plug or drillpipe dart) in a cased wellbore may be determined in real time during a cementing operation. A pressure data acquisition system is installed at a wellsite and a pressure transducer is installed at the wellhead. As the droppable object travels through casing it encounters regions with a positive or a negative change of inner cross-sectional dimension. The droppable object generates a pressure pulse as it passes through the regions. The pressure pulse and associated reflections are detected by the pressure transducer, and the signals are processed mathematically to determine the current position of the droppable object.