NAPL Flow Measurement via Immiscible Tracer Dilution

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Solution Overview

Problem

Current methods for measuring the flow of non-aqueous phase liquids (NAPLs) through porous media are time-consuming, costly, and potentially inaccurate, as they rely on estimating groundwater flow rates using tracer dilution techniques that are affected by hydraulic influences and non-flow processes, and are not suitable for NAPLs due to their immiscibility with water.

Innovation Solution

A method and apparatus that involves placing a well or boring in the path of NAPL flow, introducing a tracer that is soluble in NAPL but not in water, mixing it uniformly, and measuring tracer concentration over time to calculate the NAPL flow rate, correcting for convergence and other processes using a mixing cell model and diffusive mixer to maintain tracer uniformity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional tracer dilution techniques using salt solutions are used to measure flow rates, then groundwater flow can be estimated, but the method is not suitable for NAPLs due to their immiscibility with water and introduces errors from hydraulic influences and non-flow processes

Engineering Contradiction:

Improvemeasurement accuracy for NAPL flowVSAvoidapplicability to different fluid types

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent uses an immiscible tracer fluid (such as a fluorinated carbon liquid) as an intermediary substance that can dissolve in NAPL but not in water. This intermediary tracer allows measurement of NAPL flow without direct contact between the tracer and groundwater, eliminating errors from hydraulic influences and enabling reliable measurement specifically for NAPL while maintaining adaptability to different NAPL types.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If tracer dilution methods are used, then flow rate measurement can be obtained, but the process is time-consuming and costly requiring complex laboratory studies and empirical models

Engineering Contradiction:

Improveflow rate measurement accuracyVSAvoidtime for laboratory studies and model fitting

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent replaces complex mechanical and laboratory-based measurement systems with a simplified field method. Instead of collecting soil cores, conducting laboratory studies, and fitting empirical models, the invention uses direct in-situ tracer dilution measurements with immiscible tracers, eliminating time-consuming laboratory procedures while maintaining measurement precision through direct observation of tracer concentration changes in the NAPL phase.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent extracts and isolates the essential measurement function from the complex conventional process. By removing the need for laboratory studies, soil core collection, and empirical model fitting, the invention retains only the critical tracer dilution measurement step, significantly reducing time and cost while preserving measurement accuracy through direct field measurements.

Inventive Principle:

Principle #2Taking out (Extraction)

3Quantity of substance

If salt solutions are used as tracers, then tracer dilution can be measured, but the higher density causes the tracer solution to exit the well due to negative buoyancy even under static conditions

Engineering Contradiction:

Improvetracer detectabilityVSAvoidtracer position stability in well

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The patent changes the physical parameters of the tracer substance by using immiscible liquids with densities matching or close to the NAPL phase. This parameter change eliminates the density difference that causes negative buoyancy in salt solutions, allowing the tracer to remain stable in the well without exiting, while maintaining sufficient detectability through alternative detection methods such as fluorescence or conductivity sensors.

Inventive Principle:

Principle #35Parameter changes

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

This approach allows for direct and accurate measurement of NAPL flow rates by minimizing mixing-related errors and accounting for hydraulic influences, providing a more precise and cost-effective method compared to conventional techniques.

Implementation Method 1

mixing the tracer with the NAPL in the well or boring such that the resulting mixture is uniform

Methodology Applied

Scientific EffectDiffusion: Diffusion

Implementation Method 2

measuring the dilution of a tracer, placed into a well or boring to determine the flow rate of water through the well

Methodology Applied

Scientific EffectDilution:

Data Source

PatentUS7281435B2Measurement of non-aqueous phase liquid flow in porous media by tracer dilution

Publication Date: 2007.10.16 CHEVRON USA INC

AI summary

A method and apparatus for measuring in situ flow of non-aqueous phase liquids (NAPLs) through a porous medium is described. A tracer is introduced into a well or boring located in the medium and the tracer concentration in the well kept uniform by mixing. The rate at which the tracer is depleted from the well has been determined to be proportional to the flow rate of the NAPL through the well or boring and surrounding formation.