Downhole Chemiresistive Sensor for Liquid Phase Hydrogen Sulfide Detection

Solution Overview

Problem

Conventional chemiresistive sensors are ineffective for detecting hydrogen sulfide in the liquid phase of downhole fluids due to their design, which is suited for vapor phases, leading to inaccurate measurements and potential loss of hydrogen sulfide during sampling.

Innovation Solution

A downhole chemiresistive sensor system with a pair of electrodes and a sensing material comprising metallic nanoparticles that reversibly adsorb hydrogen sulfide, operating at frequencies greater than 10 kHz and voltages less than 1 volt to measure electrical parameters directly in the liquid phase, allowing for accurate hydrogen sulfide concentration determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional chemiresistive sensors are used for detecting hydrogen sulfide, then the sensor can operate in vapor phase, but the sensor cannot accurately measure hydrogen sulfide in liquid phase

Engineering Contradiction:

Improvehydrogen sulfide concentration measurement accuracyVSAvoidsensor applicability to liquid phase

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the electrical measurement parameters by applying AC voltage at frequencies greater than 10 kHz instead of DC or low-frequency AC voltage. This parameter change enables the sensor to operate in liquid phase by preventing electrolysis and polarization effects while maintaining chemiresistive sensing functionality for hydrogen sulfide detection

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a three-electrode configuration where a reference electrode and counter electrode serve as intermediaries. The reference electrode provides a stable potential baseline, while the counter electrode completes the electrical circuit, allowing the working electrode to selectively sense hydrogen sulfide in liquid phase without direct current passing through the sensing element

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If titration measurement method (UOP 163) is used, then liquid phase hydrogen sulfide can be measured, but significant loss of entrained hydrogen sulfide occurs leading to inaccurate concentration representation

Engineering Contradiction:

Improveliquid phase hydrogen sulfide concentration measurementVSAvoidentrained hydrogen sulfide loss

Core Design Contradiction:

Measurement precisionVSLoss of substance

Solution Approach 1:

The patent replaces mechanical agitation and phase separation methods with electrical field-based detection. By using AC voltage at frequencies greater than 10 kHz, the sensor directly measures hydrogen sulfide concentration in the liquid phase without requiring sample agitation, atmospheric pressure exposure, or phase separation that cause hydrogen sulfide loss in conventional titration methods

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If conventional chemiresistive sensors operate in vapor phase, then electrical resistance measurement is reliable, but the sensor design is not suitable for liquid phase sensing

Engineering Contradiction:

Improveelectrical resistance measurement reliabilityVSAvoidsensor suitability for liquid phase

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the electrical measurement parameters by applying AC voltage at frequencies greater than 10 kHz instead of DC or low-frequency AC voltage. This parameter change enables the sensor to operate in liquid phase by preventing electrolysis and polarization effects while maintaining chemiresistive sensing functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a three-electrode configuration where a reference electrode and counter electrode serve as intermediaries. The reference electrode provides a stable potential baseline, while the counter electrode completes the electrical circuit, allowing the working electrode to selectively sense hydrogen sulfide in liquid phase without direct current passing through the sensing element

Inventive Principle:

Principle #24Intermediary (Mediator)

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 direct detection of hydrogen sulfide in the liquid phase, compatible with high-pressure and high-temperature downhole environments, and resistant to fluid salinity interference, providing reliable and accurate measurements.

Implementation Method 1

a sensing material bridging the gap between the electrodes, the sensing material comprising metallic nanoparticles effective to reversibly adsorb hydrogen sulfide in a fluid

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS10882741B2Apparatus and downhole tools for measuring hydrogen sulfide in downhole fluids

Publication Date: 2021.01.05 BAKER HUGHES CO

AI summary

A method of determining a concentration of hydrogen sulfide in a fluid comprises exposing a sensor to the fluid, the sensor comprising a pair of electrodes defining a gap therebetween and a sensing material bridging the gap between the electrodes, measuring a value of an electrical parameter of the sensor at an applied frequency of greater than about 10 kHz and a voltage of less than about 1.0 volt when the sensor is exposed to the fluid, and determining the concentration of hydrogen sulfide in the fluid based at least in part on the measured value of the electrical parameter. Related apparatuses and methods are also disclosed.