Mercury Sensor Assembly for Fluid Speciation
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Solution Overview
Problem
Conventional methods struggle to detect and quantify organic and inorganic mercury compounds in natural gas and crude oil reservoirs due to high detection limits and difficulties in sampling under reservoir conditions, with existing technologies only reliably measuring total mercury concentrations at 1 μg/m3 or higher, and failing to speciate mercury compounds effectively.
Innovation Solution
A sensor assembly utilizing a combination of surface acoustic wave (SAW) and chemiresistor sensor arrays with thiol layers, integrated into a compact housing for in situ detection and measurement of mercury analytes in fluids, capable of operating at high temperatures and pressures, and providing continuous monitoring with rapid response times and quantification limits of 1 μg/m3 or lower.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional laboratory testing methods using gold sorbent and atomic fluorescence spectroscopy are used, then detection limit reaches 0.001 μg/m3, but the method cannot be applied in reservoir conditions and requires sample transfer above ground
Solution Approach 1:
The patent introduces an intermediary sensing system that operates at the interface between reservoir conditions and laboratory analysis requirements. The optical sensor array with wavelength-specific detection acts as a mediator, enabling in-situ measurements while maintaining detection capabilities comparable to laboratory methods.
Solution Approach 2:
The patent replaces the mechanical/physical sample transfer process with an optical detection system. Instead of physically transporting samples from reservoir to laboratory, the system uses optical sensors to detect mercury compounds in-situ, substituting mechanical sample handling with optical field-based measurement.
2Ease of operation
If sensor technologies using activated gold nano-particles with fluorescent or colorimetric assays are used, then detection can occur in water solutions, but practical lower detection limits are generally not better than 20 ppb which is too high for natural gas characterization
Solution Approach 1:
The patent applies local quality by using wavelength-specific optical filters targeted at characteristic absorption bands of different mercury compounds. Each sensor in the array is tuned to detect specific wavelengths, creating localized detection capabilities for different mercury species, thereby achieving both water solution detection and low detection limits simultaneously.
Solution Approach 2:
The patent creates a universal detection system that can detect multiple mercury compounds (elemental mercury, organic mercury, inorganic mercury) using a single sensor array platform. The multi-wavelength optical detection capability provides multi-functionality across different fluid types and mercury species.
3Reliability
If conventional methods measure total mercury concentration, then reliable measurements can be obtained at 1 μg/m3 or higher, but the methods cannot differentiate or speciate specific mercury compounds
Solution Approach 1:
The patent segments the total mercury measurement into compound-specific measurements by using multiple optical sensors tuned to different characteristic absorption wavelengths. This segmentation allows differentiation of elemental mercury, organic mercury compounds, and inorganic mercury compounds while maintaining reliable quantification for each species.
Solution Approach 2:
The patent exploits color changes (optical absorption changes) at specific wavelengths to differentiate mercury compounds. By monitoring characteristic absorption bands in the optical spectrum, the system can identify and quantify different mercury species based on their unique spectral signatures.
4Loss of information
If Drill Stem Tests and Wireline Formation Tests are conducted comprehensively, then field-wide fluid characterization can be achieved, but overall testing costs increase significantly
Solution Approach 1:
The patent extracts the mercury detection function from the comprehensive DST/WFT process and implements it as a dedicated, lower-cost sensor system. This extraction allows mercury-specific measurements to be performed independently at reduced cost while maintaining characterization completeness.
Solution Approach 2:
The patent changes the measurement parameter from comprehensive multi-phase fluid analysis to targeted mercury compound detection. This parameter change focuses resources on the specific parameter of interest (mercury speciation and concentration), reducing overall testing costs while maintaining mercury characterization completeness.
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 accurate detection and speciation of organic and inorganic mercury compounds in gas and liquids, offering a compact, easily deployable solution for real-time monitoring with improved sensitivity and flexibility, suitable for use in harsh reservoir conditions.
Implementation Method 1
The sensor array is based on the differential sorption properties measured using a surface acoustic wave (SAW) sensor array
Implementation Method 2
The sensor array is based on the differential sorption properties measured using a surface acoustic wave (SAW) sensor array, a chemiresistor array
Implementation Method 3
A sensor assembly utilizing a combination of surface acoustic wave (SAW) and chemiresistor sensor arrays with thiol layers
Data Source
AI summary
The invention relates to a sensor assembly to detect and quantify organic and/or inorganic mercury compounds, including elemental mercury that may be present in gases or liquids, such as natural gas, air, condensates, crude oil, refined petroleum gas or liquids, and water including connate water, condensed water and water containing hydrate inhibitor(s). The sensor assembly includes a housing having a flow channel defined by an inlet, a sensor array, and an outlet. The sensor array is based on the differential sorption properties measured using a surface acoustic wave (SAW) sensor array, a chemiresistor array, or a combination of the two.