Dual-Channel Downhole Probe for Contamination-Free Fluid Sampling
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Solution Overview
Problem
Existing formation testing tools face challenges in reducing borehole fluid leakage and contamination during fluid sampling, particularly in Drilling Early Evaluation Systems, where inflatable packers are easily damaged and contamination occurs due to poor seals and mudcake invasion.
Innovation Solution
The use of a probe with inner and outer channels, where the outer channel captures contaminated borehole fluid and diverts it away from the inner channel, employing a retractable wiper and separate hydraulic flow lines with pressure transducers and pumps to establish an equilibrium condition, ensuring uncontaminated fluid sampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-channel probe is used for fluid sampling, then the device structure is simple, but borehole fluid contaminates the formation fluid samples
Solution Approach 1:
The probe is divided into separate inner and outer channels that function independently. The outer channel captures contaminated borehole fluid while the inner channel collects clean formation fluid, separating the sampling functions to prevent contamination.
Solution Approach 2:
The outer channel acts as an intermediary element that intercepts contaminated borehole fluid before it can enter the inner sampling channel. This intermediate structure protects the primary sampling function from contamination.
2Reliability
If inflatable packers are used to seal the borehole, then the seal effectiveness is improved, but the packers are easily damaged in the drilling environment
Solution Approach 1:
A flexible rubber packer element is used to create the seal against the borehole wall. The flexible material conforms to the borehole surface while maintaining sealing effectiveness, and is more resistant to damage than rigid packing structures.
Solution Approach 2:
The packer is designed as a consumable component that can be easily replaced if damaged. Using simpler, more robust materials for the packer accepts potential replacement as normal operation rather than designing for indefinite service life.
3Productivity
If the probe pressure is lowered to draw formation fluids, then the fluid sampling efficiency is improved, but borehole fluid invades the formation and contaminates the sample
Solution Approach 1:
The outer channel is positioned to intercept contaminated borehole fluid before the pressure differential draws formation fluids into the probe. This preliminary capture of contaminants prevents them from mixing with the formation fluid sample.
Solution Approach 2:
Separate channels are used for capturing contaminated fluid (outer channel) versus collecting clean formation fluid (inner channel), allowing simultaneous operation at different pressure conditions without cross-contamination.
4Reliability
If extensive flushing is performed to remove contamination, then the sample purity is improved, but the sampling time increases
Solution Approach 1:
The outer channel performs preliminary capture of contaminated fluid before the actual sampling begins. This pre-capture action eliminates the need for extensive post-sampling flushing operations, reducing total sampling time while maintaining purity.
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 approach reduces contamination and sampling time, allowing for efficient collection of uncontaminated formation fluids, enhancing the accuracy of fluid analysis and reducing the need for extensive flushing and equipment maintenance.
Implementation Method 1
a pump that operates to tower the pressure at the attached probe. When the pressure in the probe is lowered below the pressure of the formation fluids, the formation fluids are drawn through the probe into the well bore
Data Source
AI summary
Apparatus and methods for downhole formation testing including use of a probe having inner and outer channels adapted to collect or inject injecting fluids from or to a formation accessed by a borehole. The probe straddles one or more layers in laminated or fractured formations and uses the inner channels to collect fluid.