Variable Frequency Tube Wave Generation in Boreholes
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Solution Overview
Problem
In noisy well pumping situations, such as during hydraulic fracturing, it is challenging to identify uniformly generated tube waves due to noise interference, and the detection of features in a wellbore is limited by the frequency of the generated tube waves, with existing impulsive pulse generators operating at low pulse amplitudes and energies.
Innovation Solution
A system and method for generating variable frequency tube waves using a high pressure multiplex pump with modified suction and discharge valves, coupled with a controller that interprets tube wave modulation schedules to adjust pump rates and frequencies, allowing for configurable and adaptive tube wave generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniformly generated tube waves are used, then the wave generation is simple, but the detection is difficult in noisy environments
Solution Approach 1:
The patent applies frequency sweeping to dynamically vary the tube wave frequency over time, transforming the static uniform wave generation into a dynamic system. This allows the wave characteristics to adapt during propagation, improving detectability in noisy environments while maintaining relatively simple generation hardware.
Solution Approach 2:
The system changes the frequency parameter of the tube waves dynamically during propagation. By sweeping through different frequencies, the system can optimize wave penetration and detection at different depths, resolving the contradiction between simple generation and difficult detection in noisy conditions.
2Measurement precision
If high frequency tube waves are used, then the resolution is improved, but the penetration depth is reduced
Solution Approach 1:
The system dynamically adjusts frequency over time, using lower frequencies initially for deep penetration and then transitioning to higher frequencies for improved resolution. This temporal variation in frequency allows both deep penetration and high resolution to be achieved without compromising either.
Solution Approach 2:
The frequency sweeping creates a periodic variation in wave characteristics during propagation. This periodic action allows the system to cycle through different frequency optima, enabling both deep penetration (low frequency) and high resolution (high frequency) at different stages of wave propagation.
3Power
If low energy tube waves are used, then the generation is easier, but the detection capability is reduced
Solution Approach 1:
The system dynamically increases the energy content of the tube waves by sweeping through higher frequencies, which naturally carry more energy. This dynamic energy increase improves detection capability while the overall system remains relatively easy to generate compared to traditional high-energy sources.
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
The system effectively generates tube waves with adjustable frequencies, enhancing detection capabilities in noisy environments and improving the resolution of wellbore feature identification by increasing pulse amplitudes and energies, thereby overcoming the limitations of existing technologies.
Implementation Method 1
These waves reflect from changes in the characteristic impedance of the medium
Implementation Method 2
Combined with some knowledge of the wellbore geometry and/or the speed of the tube wave
Implementation Method 3
A system and method for generating variable frequency tube waves using a high pressure multiplex pump with modified suction and discharge valves
Implementation Method 4
These waves reflect from changes in the characteristic impedance of the medium
Data Source
AI summary
A system for generating variable frequency tube waves includes a high pressure multiplex pump having a number of plungers, with each plunger operatively coupled to a suction valve on a suction side and a discharge valve on a discharge side. The suction valve or the discharge valve of a first one of the plungers includes an opening, such that the modified plunger on a discharge stroke pushes fluid through the opening in the suction or discharge valve. The system includes a tubular fluidly coupling the high pressure multiplex pump to a wellbore, and a pressure sensor that receives tube waves generated by the high pressure multiplex pump and reflected from the wellbore.