Carbon Quantum Dots for Stable Subterranean pH Measurement
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Solution Overview
Problem
Conventional methods for determining properties of subterranean formations, such as pH and fluid flow, are inaccurate due to sample degradation and the use of toxic or unstable tracers, which can contaminate the formation and provide incomplete or misleading data.
Innovation Solution
The use of carbon quantum dots, formed through an electrochemical process, which are stable at high temperatures and pH ranges, and exhibit unique fluorescence properties that can be measured using fiber optic cables and radiation sources to determine properties like pH and fluid flow within subterranean formations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional dyes are used to determine pH in subterranean formations, then pH measurement is possible, but the dyes are chemically unstable under formation conditions and may not provide accurate readings
Solution Approach 1:
The patent changes the chemical parameters of the tracer material from conventional organic dyes to carbon quantum dots, which have different chemical properties including enhanced stability under formation conditions. This parameter change allows the tracer to maintain its fluorescent properties and chemical stability simultaneously, resolving the contradiction between measurement capability and chemical reliability.
Solution Approach 2:
The patent uses carbon quantum dots as a composite material that combines the fluorescent properties needed for measurement with the chemical stability required for reliable operation in subterranean formations. This composite approach integrates multiple desirable properties into a single tracer material, achieving both accurate pH determination and chemical stability.
2Loss of information
If fluorophore-based tracers are used to determine fluid flow properties, then flow path information can be obtained, but the fluorophores are toxic and radioactive, contaminating the subterranean formation
Solution Approach 1:
The patent employs carbon quantum dots as a safe, non-toxic alternative to persistent toxic fluorophores. While carbon quantum dots provide the necessary fluorescent signaling for flow path detection, they are environmentally benign and do not cause long-term contamination, effectively replacing harmful tracers with safe ones that fulfill the information gathering function without the harmful side effects.
Solution Approach 2:
The patent converts the potential harm of tracer contamination into a benefit by using carbon quantum dots that are inherently safe for subterranean formations. The tracer material provides the necessary flow information while simultaneously avoiding the contamination problems associated with traditional fluorophores, turning a previously harmful practice into a safe one.
3Loss of time
If dyes are continuously injected to obtain continuous pH measurement, then real-time monitoring is achieved, but the complexity and cost of continuous injection systems increase
Solution Approach 1:
The patent enables the tracer system to serve itself by using carbon quantum dots that remain stable and fluorescent throughout the entire formation evaluation process. The dots are injected once and continue to provide pH information through their fluorescent properties without requiring continuous replenishment or complex injection systems, allowing the tracer to maintain its function autonomously over time.
Solution Approach 2:
The patent uses a single injection of carbon quantum dots that provides prolonged measurement capability, rather than continuous injection. This partial action (single injection) achieves the effect of continuous monitoring by utilizing the long-lasting stability and fluorescent properties of the carbon quantum dots, reducing the need for complex continuous injection infrastructure.
4Measurement precision
If formation fluid samples are brought to surface conditions for pH analysis, then laboratory measurement is possible, but acid gases and salts come out of solution, irreversibly changing the pH of the sample
Solution Approach 1:
The patent replaces the mechanical sampling and transport system with an in-situ optical measurement system. Instead of physically bringing samples to the surface where pressure changes cause composition changes, the system uses carbon quantum dots to measure pH directly in the formation through fluorescent properties, substituting mechanical sample transport with optical field-based measurement that does not disturb the fluid composition.
Solution Approach 2:
The patent introduces carbon quantum dots as an intermediary that enables pH measurement without direct contact between the measurement system and the formation fluid. The quantum dots serve as a mediator that translates pH information into fluorescent signals that can be detected optically, allowing indirect measurement that preserves the original fluid composition and conditions.
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, real-time measurement of properties like pH and fluid flow without continuous dye injection, reducing contamination risks and providing reliable data through stable and chemically inert carbon quantum dots.
Implementation Method 1
carbon quantum dots disposed in the fluid, and a detector within the wellbore, the detector configured to measure at least one fluorescence property of the carbon quantum dots
Implementation Method 2
providing an electrolyte comprising a carbon source and a source of ions to an electrochemical cell, introducing the electrolyte between platinum electrodes of the electrochemical cell, and applying electrical current between the platinum electrodes to form carbon quantum dots
Data Source
AI summary
A system for determining at least one property of at least one fluid in at least one subterranean formation comprises a fluid delivery system configured and positioned to deliver a fluid into at least one of at least one subterranean formation and a wellbore extending through the at least one subterranean formation. The system comprises a radiation source within the wellbore, the radiation source configured to generate excitation radiation, carbon quantum dots disposed in the fluid, and a detector within the wellbore, the detector configured to measure at least one fluorescence property of the carbon quantum dots. Related methods of determining a property of a wellbore and methods of forming the carbon quantum dots are also disclosed.