Downhole Bubble Sensor for Gas Reservoir Pressure Measurement
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Solution Overview
Problem
Conventional methods for determining formation pressures in low permeability shale gas reservoirs are difficult, costly, time-consuming, and often inaccurate, with risks of tool stuckage and loss, and require prolonged testing periods.
Innovation Solution
Incorporating sensors, such as optical and resistivity sensors, within downhole tools to detect gas bubbles in liquids by monitoring pressure reduction, allowing for accurate determination of formation pressure through systematic pressure adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional wireline formation test methods are used to measure formation pressures in low permeability shale gas reservoirs, then measurement capability is provided, but the testing period requires several hours and risks of tool stuckage or loss are substantial
Solution Approach 1:
The patent replaces conventional mechanical pressure testing systems with an optical sensing system. The optical sensor detects gas bubbles in the drilling fluid by measuring changes in light transmission or reflection, eliminating the need for prolonged mechanical pressure maintenance and measurement. This substitution reduces testing time from several hours to a much shorter duration while maintaining measurement accuracy.
Solution Approach 2:
The patent utilizes the phase transition phenomenon where gas from the formation dissolves in the drilling fluid under pressure and then bubbles out when pressure is reduced. By monitoring the pressure at which gas bubbles first appear in the fluid using optical sensors, the formation pressure can be determined quickly without prolonged testing. This phase transition method provides rapid measurement while avoiding tool stuckage risks.
2Measurement precision
If conventional wireline formation test methods are used, then formation pressure data can be obtained, but the risks of tool stuckage or loss are substantial
Solution Approach 1:
The patent replaces conventional mechanical pressure testing systems with an optical sensing system. The optical sensor detects gas bubbles in the drilling fluid by measuring changes in light transmission or reflection, eliminating the need for prolonged mechanical pressure maintenance and measurement. This substitution reduces testing time from several hours to a much shorter duration while maintaining measurement accuracy.
Solution Approach 2:
The patent utilizes the natural phase transition of gas from dissolved state to bubble formation as the measurement mechanism. The system allows the formation itself to provide the measurement signal through gas bubble exsolution, eliminating the need for active tool intervention or prolonged mechanical pressure application. This self-service approach reduces tool exposure time and associated risks.
3Measurement precision
If injection fall off test is performed to measure reservoir pressures, then pressure data can be obtained, but the gauges must be left in place for several weeks
Solution Approach 1:
The patent replaces conventional mechanical pressure testing systems with an optical sensing system. The optical sensor detects gas bubbles in the drilling fluid by measuring changes in light transmission or reflection, eliminating the need for prolonged mechanical pressure maintenance and measurement. This substitution reduces testing time from several hours to a much shorter duration while maintaining measurement accuracy.
Solution Approach 2:
The patent utilizes the phase transition phenomenon where gas from the formation dissolves in the drilling fluid under pressure and then bubbles out when pressure is reduced. By monitoring the pressure at which gas bubbles first appear in the fluid using optical sensors, the formation pressure can be determined quickly without prolonged testing. This phase transition method provides rapid measurement while avoiding tool stuckage risks.
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 precise and efficient measurement of formation pressures, reducing risks and time required, while ensuring accurate results without prolonged tool deployment.
Implementation Method 1
An example sensor is an optical sensor that may be used to detect gas in liquids by measuring an amount of reflected light at the sensor point. Because bubbles reflect light differently than liquid, a change in the amount of reflected light may be representative of the presence of bubbles in the liquid.
Implementation Method 2
Another example sensor that may be used to detect gas in liquids detects bubbles by detecting a change in resistivity of the trapped fluid at the sensor point that may be caused by the presence of the bubbles.
Data Source
AI summary
Example methods, apparatus and articles of manufacture to measure gas reservoir formation pressures are disclosed. A disclosed example method includes positioning a downhole bubble sensor in a wellbore formed in a geological gas reservoir formation, trapping a fluid in a portion of the wellbore including the bubble sensor, pressurizing the trapped fluid, reducing pressurization of the fluid until the bubble sensor detects one or more bubbles in the fluid, recording a pressure of the fluid when the bubble sensor detects the one or more bubbles, and determining a formation pressure of the gas reservoir from the recorded pressure.