Subsurface Thermal Sensor Array for NSZD Rate Monitoring
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for monitoring subsurface temperature profiles to determine natural source zone depletion (NSZD) rates are limited by the need for background correction, which can lead to inaccurate measurements due to non-uniform surface heating and cooling effects, resulting in implausible or negative NSZD rates, especially in areas with varying albedo, infiltration, and radiation patterns.
Innovation Solution
A system comprising thermal sensors and a computing device that estimates the planar location of subsurface heating or cooling sources within a subsurface formation, calculates thermal parameters, and converts them into NSZD rates without requiring background temperature data, using a rigorous first-principle heat flow approach to monitor the rate of change of organic materials and facilitate remedial actions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If background correction is applied to temperature measurements, then surface heating and cooling effects are accounted for, but measurement accuracy deteriorates due to non-uniform surface conditions
Solution Approach 1:
The patent extracts and removes the background temperature component from the measured temperature profile using an iterative algorithm. By separating the background temperature (T_background) from the total measured temperature (T_measured), the method isolates the temperature anomaly caused solely by NSZD heat generation, eliminating the need for manual background correction and avoiding errors from non-uniform surface conditions
Solution Approach 2:
The patent employs an iterative feedback algorithm that continuously refines the estimation of background temperature and NSZD heat generation. The algorithm uses the calculated NSZD heat to update the temperature profile, then recalculates background temperature, repeating this process until convergence is achieved, thereby improving measurement accuracy through iterative self-correction
2Productivity
If gas flux methods are used to quantify NSZD rates, then short-term measurements are obtained, but reliability deteriorates due to dynamic gas fluxes from barometric pumping and transient soil moisture
Solution Approach 1:
The patent uses thermal sensors to measure temperature at multiple depths (excessive measurement points) to capture the complete thermal profile. By measuring temperature at more locations than the minimum required, the method ensures adequate sampling of the thermal field, enabling robust calculation of NSZD rates even in dynamic conditions
Solution Approach 2:
The patent implements continuous temperature monitoring at multiple subsurface depths, providing ongoing data collection without interruption. This continuous measurement approach captures temporal variations in thermal conditions and enables calculation of NSZD rates over extended periods, eliminating the brief measurement windows of gas flux methods
3Measurement precision
If thermal sensors are placed at multiple depths, then complete temperature profile is obtained, but device complexity increases
Solution Approach 1:
The patent divides the subsurface monitoring task into discrete depth segments, placing thermal sensors at specific depth intervals (e.g., 0.5m, 1.0m, 1.5m, 2.0m). This segmentation of the continuous subsurface into discrete measurement zones simplifies the overall system design while maintaining complete temperature profile coverage through strategic depth distribution
Solution Approach 2:
The patent employs a multi-functional sensor array system where the same thermal sensors serve multiple purposes: measuring temperature at their specific depths, collectively forming the complete temperature profile when combined, and enabling calculation of both background temperature and NSZD heat generation. This multi-functionality reduces the need for separate specialized measurement systems
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 method provides accurate, real-time monitoring of NSZD rates by eliminating the need for background correction, reducing errors, and enabling effective remedial actions such as clean-up schedules for subsurface contamination, while ensuring accurate characterization of thermal changes within the subsurface formation.
Implementation Method 1
continuously measuring of vertical temperature profiles in background and LNAPL-impacted areas
Implementation Method 2
conduction of an energy balance to resolve NSZD energy
Implementation Method 3
estimating NSZD rates by dividing NSZD energy by the estimated NSZD heat of reaction
Implementation Method 4
estimate a planar location of a subsurface heating or cooling source produced by an endothermic reaction or an exothermic reaction of organic material
Data Source
AI summary
A subsurface monitoring system and method is provided for measuring a rate of change in an amount of a reactive material within a subsurface formation using measurements of thermal parameters at one or more positions within the subsurface without the need for background correction which may lead erroneous calculations and require additional monitoring equipment. The measured thermal parameters may be used to determine the heat generated by the degradation of the reactive material. The method may include measuring a first temperature near the surface of a subsurface region and a second temperature further from the surface. In some instances, an estimated location of a planar subsurface heat source/sink due to exothermic degradation reactions within the subsurface may be selected. With the derived thermal parameters and the estimated location of the subsurface heat source/sink, change rates for the reactive materials in the subsurface region may be determined or estimated.