Downhole Probe Seal Pad Conforming to Borehole Wall
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Solution Overview
Problem
Current formation testing methods, such as wireline formation testers (WFTs) and drill stem testing (DST), face challenges including tool sticking, formation damage, difficulties in highly deviated and extended reach wells, and inaccurate pressure measurements due to filtrate invasion and mudcake buildup, which affect the representativeness of formation fluid samples and reservoir pressure measurements.
Innovation Solution
The development of a formation tester tool with a probe assembly that includes a seal pad made of elastomeric or electro-rheological materials, which conforms to the borehole wall and mudcake to isolate formation fluids from drilling fluids, allowing for accurate sampling and pressure measurement while withstanding drilling conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional wireline formation testers or drill stem testing methods are used, then formation testing can be performed, but tool sticking and formation damage occur
Solution Approach 1:
The probe assembly is designed to be movable rather than fixed, allowing it to extend to engage the formation and retract to clear the borehole. This dynamic configuration enables the probe to engage and disengage from the formation dynamically, reducing the risk of tool sticking and formation damage while maintaining reliable formation testing capabilities
Solution Approach 2:
The testing tool is divided into separate functional components: a main body that remains in the borehole and a movable probe assembly that can be extended and retracted. This segmentation allows the probe to be isolated from the main tool body, reducing the risk of tool sticking and formation damage to only the probe portion while maintaining overall system reliability
2Adaptability or versatility
If WFTs are used in highly deviated and extended reach wells, then formation testing can be conducted, but difficulties arise in accessing the formation
Solution Approach 1:
The seal pad is made of elastomeric material that can deform and conform to irregular borehole wall surfaces, including those in highly deviated and extended reach wells. This flexibility allows the probe to successfully engage the formation in challenging well geometries where rigid sealing mechanisms would fail
Solution Approach 2:
The probe assembly can be extended and retracted dynamically to reach the formation in deviated wells, allowing the tool to adapt to varying wellbore geometries and maintain ease of operation across different well types including highly deviated and extended reach wells
3Measurement precision
If significant time passes before DST or WFT engages the formation, then drilling operations can be completed, but filtrate invasion and mudcake buildup affect pressure measurement accuracy
Solution Approach 1:
The elastomeric seal pad can conform to and seal against the mudcake layer that forms on the borehole wall, creating an effective seal even when significant time has passed since drilling operations began. This allows accurate pressure measurements to be obtained despite the presence of mudcake and filtrate invasion
Solution Approach 2:
The seal pad acts as an intermediary between the probe and the formation, sealing against the mudcake layer rather than requiring direct contact with clean formation. This allows the system to overcome the time delay issue by effectively sealing through the mudcake barrier to access formation fluids for accurate pressure measurements
4Ease of operation
If the isolation pad seal integrity is compromised, then probe operation is simplified, but borehole fluid leaks into collected formation fluids
Solution Approach 1:
The elastomeric seal pad provides reliable sealing through its flexible, conforming properties, maintaining sample integrity without requiring complex sealing mechanisms. The material's ability to deform and seal effectively against irregular surfaces ensures borehole fluid isolation while keeping the probe design relatively simple
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 tool ensures the integrity of formation fluid samples by preventing contamination from drilling fluids, enhances the accuracy of reservoir pressure measurements, and maintains reliability under harsh drilling conditions, reducing the need for repeated tests and minimizing formation damage.
Implementation Method 1
a seal pad made of elastomeric or electro-rheological materials, which conforms to the borehole wall and mudcake
Implementation Method 2
a seal pad made of elastomeric or electro-rheological materials
Data Source
AI summary
A downhole, extendable apparatus and methods of use are described and claimed herein. In one embodiment, the extendable apparatus includes a piston that extends toward a borehole wall, the piston having an inner sampling member that is also extendable. The sampling member may be further extended to engage the borehole wall and penetrate the formation. The sampling member may also include a screen and an inner scraper or wiper that frictionally engages the screen and reciprocates to remove debris from the screen. The piston may comprise a seal pad having an internal cavity for receiving a volume of fluid. In another embodiment, the extendable apparatus comprises multiple, concentric pistons for extending the sampling member further toward the borehole wall than is possible with a single piston. The extendable apparatus may also include a retraction contact switch and position indicator.