Fluid Level Measurement Using Pulse Width Decay
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Solution Overview
Problem
Existing techniques for determining fluid level in the tubing-casing annulus of oil, gas, or water wells require knowledge of the speed of sound in the casing gas, which limits their accuracy and applicability.
Innovation Solution
A system that generates a pressure pulse of known width and shape, measuring the decay rate of the returning pulse to calculate the fluid depth without relying on the speed of sound in the casing gas, utilizing pulse dispersion effects across different frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the speed of sound in casing gas is assumed to calculate fluid level, then the measurement can be performed with simple equipment, but the accuracy is limited by uncertainty in the speed of sound value
Solution Approach 1:
The patent changes the measurement parameter from round-trip time (which requires speed of sound knowledge) to pulse width decay rate (which is independent of speed of sound). By measuring how the pulse width decreases as it travels through the gas column, the system determines fluid level without needing to know the speed of sound in the casing gas.
2Ease of operation
If round-trip time measurement is used to determine fluid depth, then the calculation is straightforward, but the method requires knowledge of the speed of sound in casing gas
Solution Approach 1:
The patent replaces the time-based measurement method with a pulse width decay-based method. Instead of measuring when the pulse returns (time of flight), the system measures how the pulse width changes as it propagates through the gas column. This substitution eliminates the need to know the speed of sound while maintaining measurement capability.
3Reliability
If pressure pulse dispersion is measured to determine distance, then speed of sound knowledge is not required, but the measurement requires accurate pulse width decay detection
Solution Approach 1:
The system uses the returning pressure pulse itself as feedback to determine the fluid level. By analyzing the pulse width decay of the reflected pulse, the system obtains information about the distance to the fluid interface without requiring external calibration or speed of sound data. The pulse carries its own measurement information through its width characteristics.
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 accurate surface determination of fluid level in the tubing-casing annulus without measuring the time for the pulse to return, providing a robust and independent method for fluid depth calculation.
Implementation Method 1
Because the pressure pulse consists of many different acoustic frequencies, and because different acoustic frequencies experience different speeds of sound in a gas, a process call dispersion, the shape of the pressure pulse will widen the farther the pulse travels.
Data Source
AI summary
A system and method for determining the depth to the top surface of a fluid contained in a hydrocarbon well generates a pressure pulse which travels down the casing to the fluid and receives a returning pressure pulse. The system and method may measure the decay rate or pulse width of the returning pressure pulse and not necessarily require the measurement of the time between the emission of the pressure pulse and the detection of the return pulse to ascertain the depth to the fluid.