Downhole Sampling of Compressible Fluids via Bypass and Segmentation
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Solution Overview
Problem
Current downhole sampling tools are inefficient for highly compressible fluids like gases, as positive displacement pumps cause irreversible changes and pressure cycling, leading to low-pressure, low-mass samples.
Innovation Solution
A downhole fluid sampling tool with a primary fluid flow line, a fluid analysis module, a pumping module with a bypass flow line and valve, and a compressible fluid sampling vessel with a piston defining sample and pressure equalization chambers, allowing for efficient sampling without pressure cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If positive displacement pumps are used to pump compressible fluids, then fluid can be moved through the system, but the pump efficiency decreases and irreversible changes occur in the fluid
Solution Approach 1:
The system is divided into separate functional modules: a pumping module for moving fluid through analysis instrumentation, and a separate sampling vessel for collecting samples. This segmentation allows the pump to operate without directly compressing the sample, preventing irreversible changes while maintaining pumping efficiency.
Solution Approach 2:
A bypass flow line acts as an intermediary pathway, allowing fluid to be diverted from the pump outlet directly to the sampling vessel without passing through the pump compression cycle. This intermediary route preserves sample integrity while the pump continues to move fluid efficiently through the system.
2Ease of operation
If formation pressure is used to drive fluid into the sample chamber, then sampling can be achieved, but the sample pressure is significantly reduced resulting in low pressure, low mass samples
Solution Approach 1:
The pump is activated before sampling to pre-pressurize the fluid and establish proper flow conditions. This preliminary action ensures that when the sample is transferred to the vessel, it maintains appropriate pressure and mass, avoiding the low pressure, low mass problem associated with direct formation pressure driving.
Solution Approach 2:
The natural formation pressure driving mechanism is replaced with an active pumping system that can control fluid transfer. The pump provides mechanical energy to maintain sample pressure and mass, substituting the passive formation pressure mechanism that resulted in inadequate sample conditions.
3Measurement precision
If compressible fluid is pumped through analysis instrumentation, then fluid composition can be analyzed, but pressure cycling occurs which compromises sample integrity
Solution Approach 1:
The sampling function is extracted from the pumping and analysis flow path. A dedicated sampling vessel with a bypass connection allows sample collection to occur separately from the pump-driven analysis cycle. This extraction eliminates pressure cycling from the sample while maintaining the ability to analyze fluid composition through the pump system.
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 efficient sampling of compressible fluids while maintaining fluid integrity by eliminating pressure cycling, resulting in higher mass and more accurate samples.
Implementation Method 1
The fluid sampling vessel includes a piston that defines a first sample chamber and a second pressure equalization chamber within the vessel
Data Source
AI summary
A downhole compressible fluid sampling tool includes a primary fluid flow line deployed between a fluid inlet probe and a fluid outlet line. A fluid analysis module and a fluid pumping module are deployed in the primary fluid flow line. The fluid pumping module includes a pump in parallel with a bypass flow line having a bypass valve. A compressible fluid sampling vessel is deployed in parallel with and in fluid communication with the primary flow line. A method for obtaining a sample of a compressible downhole fluid includes turning off the pump and opening the bypass valve to enable the downhole fluid to flow into the fluid sampling vessel. The pump may then be optionally turned back on to pressurize the sample.