Variable-Volume Reservoirs for Downhole Fluid Analysis
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Solution Overview
Problem
Current methods for chemical analysis of fluid samples in wellbore environments are limited by the need for transporting samples to the surface, which can alter compositions due to changes like CO2 outgassing or precipitation, and often require environmentally unfriendly chemicals, especially in sensitive areas like Alaska.
Innovation Solution
A downhole fluid processing device and process using variable-volume reservoirs with a fluid mixer and optical property detector, allowing for in-situ analysis by varying the mixing ratio of reactants and samples, enabling continuous mixing, titration, and flow injection analysis without surface transport.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If samples are transported to the surface for analysis, then analysis can be performed with laboratory equipment, but sample composition changes due to CO2 outgassing, H2S precipitation, and other environmental factors
Solution Approach 1:
The system performs preliminary chemical reactions and analysis downhole before the sample reaches the surface. Reactants are injected into the formation fluid in-situ, and measurements are taken while the fluid is still in its original state, preventing composition changes that would occur during transport
Solution Approach 2:
Chemical reactants serve as intermediaries to enable downhole analysis. The reactants are injected into the formation fluid to create measurable products or color changes that can be detected by optical sensors, allowing analysis to occur in the harsh downhole environment rather than requiring surface transport
2Measurement precision
If traditional chemical analysis methods are used, then comprehensive component analysis can be achieved, but environmentally harmful chemicals must be used
Solution Approach 1:
The system changes the parameters of the chemical reactions by using reactants and conditions that are environmentally friendly yet still provide sufficient optical contrast for detection. The patent specifically mentions using biodegradable surfactants and environmentally safe reactants that maintain analytical capability while reducing environmental harm
Solution Approach 2:
The downhole environment itself serves as a controlled, isolated chamber where chemical reactions occur. The high pressure and temperature conditions downhole create an environment where reactions can proceed with environmentally friendly chemicals, and the formed products are contained and returned to the formation without contaminating the surface environment
3Loss of time
If downhole chemical reactions are performed, then in-situ analysis is enabled, but precise control of mixing ratios is required
Solution Approach 1:
The system uses hydraulic principles to control the injection of reactants downhole. By controlling the pressure and flow rates of the reactant injection, the system achieves precise mixing ratios without complex mechanical mixing devices. The high-pressure downhole environment naturally facilitates the mixing process through pressure-driven flow
Solution Approach 2:
The system dynamically adjusts the injection rates and timing of multiple reactants to achieve the desired mixing ratios. The control system monitors the downhole conditions and adjusts reactant injection in real-time, allowing flexible control of the chemical reactions despite the harsh and variable downhole environment
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 environmentally friendly chemical analysis of fluid samples in real-time, maintaining sample integrity and reducing the need for harmful chemicals, while allowing for accurate determination of analyte concentrations and properties.
Implementation Method 1
A fluid mixer is serially disposed along the fluid conduit at a location between open ends of the first and second variable-volume reservoirs
Implementation Method 2
A selectable mixture of the reactant and the sampled fluids is obtainable by varying volumes of the first and second variable-volume reservoirs
Data Source
AI summary
Described herein are variable-volume reservoir (e.g., syringe pump) based processes and systems usable to characterize samples of reservoir fluids, without having to first transport the fluids to the surface. Variable-volume reservoirs are used, for example, for one or more of storing reactants, controlling mixing ratios and storing used chemicals. The processes and systems can be used in various modes, such as continuous mixing mode, flow injection analysis, and titrations. A fluid interrogator, such as a spectrometer, can be used to detect a change in a physical property of the mixture, which is indicative of an analyte within the mixture. In at least some embodiments, a concentration of the analyte solution can be determined from the detected physical property.