Cement Annulus Permeability Measurement Tool
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Solution Overview
Problem
Current methods for in situ cement annulus testing in oil wells lack effective measurement of fluid dynamic properties, which are crucial for ensuring the integrity and permeability of the cement barrier, particularly in carbon dioxide storage applications where leakage through permeable or degraded cement annuli is a concern.
Innovation Solution
A tool is used to measure the change in pressure over time in a probe placed against the cement annulus, allowing for the determination of fluid dynamic properties like permeability, by monitoring the pressure decay and using established theoretical models to calculate the cement permeability, ensuring that carbon dioxide does not leak through the cement annulus at undesirable rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustic measurements are used to evaluate cement integrity, then mechanical properties such as bond quality and strength can be determined, but fluid dynamic properties such as permeability cannot be measured
Solution Approach 1:
The probe assembly is designed to perform multiple functions: it can conduct acoustic measurements (using transducers) and fluid dynamic measurements (using pressure sensors and flow meters). This multi-functional design allows the same tool to evaluate both mechanical properties (bond quality, strength) and fluid dynamic properties (permeability, flow characteristics) of the cement annulus, resolving the limitation of acoustic-only tools.
Solution Approach 2:
The invention introduces a fluid medium (such as gas or liquid) as an intermediary to enable permeability measurement. By injecting fluid into the cement annulus through the probe and measuring pressure differential and flow rate, the system can determine permeability without directly measuring the cement matrix itself. This intermediary approach allows fluid dynamic property measurement while maintaining the integrity of the cement evaluation process.
2Reliability
If non-invasive ultrasonic measurements are used, then mechanical qualities of cement can be determined, but direct measurement of permeability and fluid dynamic characteristics is not possible
Solution Approach 1:
The invention employs pneumatic and hydraulic principles to measure cement permeability directly. By injecting fluid (gas or liquid) into the cement annulus through the probe and measuring the pressure differential across the cement and the resulting flow rate, the system can calculate permeability using Darcy's law. This direct measurement approach provides reliable and precise permeability data, overcoming the limitations of indirect ultrasonic estimation methods.
3Ease of operation
If acoustic tools are used to evaluate cement integrity, then mechanical properties can be assessed, but the tools cannot measure fluid dynamic characteristics
Solution Approach 1:
The invention merges acoustic measurement capabilities with fluid dynamic measurement capabilities into a single integrated tool. The probe assembly includes both ultrasonic transducers for acoustic measurements and pressure sensors/flow meters for fluid dynamic measurements. This combination allows operators to obtain both mechanical property data (from acoustic signals) and fluid dynamic property data (from pressure and flow measurements) in a single operation, simplifying the evaluation process while expanding measurement capabilities.
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
This method provides accurate assessment of cement annulus permeability, enabling the identification of suitable zones for carbon dioxide storage by ensuring the cement barrier has a permeability in the range of microDarcys, thereby preventing leakage and ensuring well integrity.
Implementation Method 1
measuring the change of pressure in the probe over time, where the change in pressure over time is a function of among other things, the initial probe pressure, the formation pressure, and the fluid dynamic property of the cement
Data Source
AI summary
The permeability of the cement annulus surrounding a casing is measured by locating a tool inside the casing, placing a probe of the tool in contact with the cement annulus, measuring the change of pressure in the probe over time, where the change in pressure over time is a function of among other things, the initial probe pressure, the formation pressure, and the permeability, and using the measured change over time to determine an estimated permeability. The estimated permeability is useful in determining whether carbon dioxide can be effectively sequestered in the formation below or at the depth of measurement without significant leakage through the cement annulus.