Patent Application
20250154864
The disclosed technology relates generally to water testing systems and methods configured for testing contaminants in the water, and more particularly, some embodiments relate to initiating a testing process by adding a tracer solution to a water system absent releasing the tracer into the surrounding environment during the testing process, then removing the tracer solution to a container after the testing process is complete such that the tracer solution helps to measure contaminants in the water.
One of the challenges of conducting tracer studies is developing a sampling and monitoring plan that allows the tracer to be detected downgradient of the injection area. It is therefore imperative to develop an understanding of groundwater flow direction and velocity, as well as subsurface conditions, in order to determine where the tracer may travel and at what time it may be expected at downgradient monitoring locations. A groundwater flow model represents an effective tool to help acquire this initial understanding and guide monitoring design.
According to various embodiments of the disclosed technology, the present application discloses a system configured to perform contaminant testing of groundwater wells using a testing process using a tracer solution. The system may initiate the testing process to measure contaminants in the water, for example, by adding the tracer solution (e.g., as a gas) to a water system absent releasing the tracer solution into the surrounding environment during the testing process, then removing the tracer solution to a container after the testing process is complete. The amount of tracer solution that remains in the water system as its collected can be compared with a predicted concentration value determined by a model.
In some examples, an action may be initiated based on the difference between the measured value and the predicted value. For example, one of the actions may be to update or retrain the model, which can improve the accuracy of the predicted contaminant in the water using the measured tracer data. This action may help improve the accuracy of the model overall. In some examples, the update or retrain of the model may be based on the difference between the actual tracer measurements/profile and the model-predicted tracer profile.
In some examples, the prediction of the concentration amount (or dilution amount) may be determined by a model that predicts the tracer solution that remains in the water system after a certain time or distance from the injection site. For example, the testing process may correctly calculate the potential dilution of the tracer given the volume of recharge water, groundwater and seepage paths, and distance to the monitoring wells or other data points. The dilution calculation may help determine the initial volume of tracer to use during the testing process, in order to anticipate concentrations and travel times to the downgradient point(s) of detection.
In some examples, sulfur hexafluoride (SF6) gas may be used as an extrinsic tracer solution for implementing the testing process, although other gases are available without diverting from the essence of the disclosure, including Rhodamine Dye and fluorescein dye. In some examples, SF6 may correspond with lower detection levels than other solutions. SF6 may correspond with a computationally simpler analytical method for detection as compared to other added tracer solutions that have been used in traditional systems and tests (e.g., Xenon gas).
In some examples, the testing process may not bubble the tracer solution into the percolation water. For example, in traditional systems, the tracer solution may be released to the environment through bubbling gas into a well or a surface recharge basin used for percolating water into the ground. Rather, embodiments of the system may add the tracer solution to a slug of water, which may be injected and pressurized to maintain the tracer solution in the existing injection wells and measured using various methods described herein. By injecting the tracer solution at depth directly into the groundwater, the tracer solution may not be subject to volatilization into the environment/atmosphere.
Other features and aspects of the disclosed technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with embodiments of the disclosed technology. The summary is not intended to limit the scope of any inventions described herein.
The present disclosure, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The drawings are provided for purposes of illustration only and merely depict typical or example embodiments. These drawings are provided to facilitate the reader's understanding of various embodiments and shall not be considered limiting of the breadth, scope, or applicability of the present disclosure. It should be noted that, for clarity and ease of illustration, these drawings are not necessarily made to scale.
The figures are not intended to be exhaustive or to limit various embodiments to the precise form disclosed. It should be understood that various embodiments can be practiced with modification and alteration.
Embodiments of the technology disclosed herein are directed toward systems and methods that relate to adding a solution at a wellfield site and measuring the solution to test contaminants in water using a testing process for detecting a tracer solution in a water system comprising groundwater wells. The testing process may comprise various implementations, including (1) a local analysis of the solution at the wellfield site, (2) a subsurface infiltration gallery, or (3) a SCADA system.
At block 102, a testing process may be initiated. For example, the testing process that is initiated may add a first amount of tracer solution at a first well coupled to a membrane. The first well may correspond with an injection well. In some examples, the membrane may inject the tracer solution absent bubbling the tracer solution to the environment.
In some examples, the first well is part of a plurality of wells that are locally accessed by computer systems at each well location. A well may comprise, for example, a bored, drilled, or driven shaft whose depth is greater than the largest surface dimension; or, a dug hole whose depth is greater than the largest surface dimension; or, an improved sinkhole; or, a subsurface fluid distribution system.
The type of well may comprise an injection well, a monitoring or measuring well, or a production well. Water may also be stored in a recharge basin. An injection well is used to place fluid underground into porous geologic formations, such as sand or gravel. In some examples, the injection wells may comprise wells that are screened in an aquifer between a depth of 80-210 ft bgs, 105-195 ft bgs, and 80-150 ft bgs, and are used to add the tracer solution directly into the aquifer under pressure. The downgradient production wells may comprise wells that are pumped to produce water at an average production or an estimated yield. The monitoring wells may be downgradient from the injection wells, where the monitoring wells are no less than two weeks but no more than six months of travel through a saturated zone in a surrounding area and at least 30 days upgradient of the nearest drinking water well. The samples obtained from the monitoring wells may be obtained independently from each aquifer, initially receiving the water used as a source of drinking water supply, and validated as receiving recharge water.
In some examples, the first well is in communication with a remote computer system that provides the tracer solution to each well remotely and measures the concentration of the solution remotely. However, the communication between the well and the remote system, such as a SCADA system, is not required in every embodiment described herein.
At block 104, the tracer solution may be collected at a second well in a second amount. In some examples, the second well, wherein the second well is a monitoring well. In some examples, the second well is part of the plurality of wells that are locally accessed by computer systems at each well location or remotely accessed (e.g., by the SCADA system).
At block 106, the difference between the tracer solution added at the first well and the tracer solution collected at the second well may be compared to a predicted concentration value determined by a model.
In some examples, treated water may be used as the injection water for the testing process using tracer solution. Treated water may be injected via injection wells within a total anticipated recharge rate (e.g., 3 MGD). The injection may be evenly split amongst multiple wells. A side stream of the injection water may be saturated with the tracer solution that is metered into the water. The tracer solution may be injected at a pre-defined pressure and the tracer-saturated water may then be pumped directly into the injection well. The tracer-saturated water may be pumped at a depth that may ensure that the tracer solution will remain dissolved and not off-gas.
The tracer solution may be supplied as a compressed gas and at a pre-defined purity level (e.g., a minimum 99% purity). The tracer solution may be added to the injection well operating at an injection rate (e.g., 1,000-gpm injection rate). In some examples, the tracer solution may be added to a slug and injected to the well as a side stream of the injection water (using membrane illustrated in
The amount of tracer solution that is added to the injection water may be measured gravimetrically using a scale. The tracer solution may be measured and added based on weight. By using the weight of the tracer solution, the tracer solution may not be subject to error from flow rate measurements in the injection water or side stream. The tracer solution may be added to the injection well over a particular period of time (e.g., approximately 12 hours).
In an illustrative example, when an injection well is used, the pipeline that is carrying the reclaimed water to the injection well may provide hundreds or thousands of gallons a minute flow. A side stream of the water may be separated from the larger water flow to add the tracer solution. For example, the side stream may use a portion of the water flow (e.g., as 100 gallons per minute). To add the tracer solution, the water may be run through a membrane apparatus to dissolve the tracer and then sent back into the pipe that has the water. The water with the tracer solution may be added back to the injection well as the side stream.
The components of the water sample may include a concentration amount of the tracer sample after it is diluted in the water system, absent releasing the tracer solution into the surrounding environment. In this example, the loss of the tracer solution is minimized and can remain in the water system for a more accurate testing process.
As an illustrative example, the water basin may comprise thousands of gallons per minute of recycled water 510 flowing into it, and the testing process may add 100 gallons per minute in a side stream with the tracer solution.
An action may be performed after measuring the tracer solution from the water that is extracted (e.g., from the from a surface spreading basin or an injection well). For example, the action may include using the water for a beneficial use, such as drinking water.
Infiltration gallery 610 comprises a set of pipes 620 having a portion of each pipe perforated and buried underground. The perforation may be placed, for example, in a trench in the bottom of a water basin. Using the membrane system, the tracer solution may be added to water 630 and then introduced into the infiltration system. Infiltration gallery 610 may maintain the necessary hydraulic pressure to prevent off-gassing of the tracer from the solution. The water level of the water 630 above infiltration gallery 610 may help maintain the pressure to prevent off-gassing of the tracer from the solution. The tracer solution can percolate down into the ground below the basin.
In some examples, the hydraulic pressure of the water above the infiltration gallery 610 may be maintained when the water level in the basin is at least a threshold amount. The depth 640 of the inflation gallery 610 may be deep enough to maintain the pressure from water 630 at a particular amount 650. As an illustrative example, when the surface spreading basin is operating, there may approximately 3-5 ft of water above the infiltration gallery, which exerts “X” amount of pressure on the tracer solution to prevent it from bubbling to the surface.
In various embodiments, the wellfield management system 800 comprises a plurality of groundwater wells 810; a plurality of field instruments, each associated with one or more of the plurality of groundwater wells; a plurality of remote terminal units (RTU) 814 (illustrated as 814A, 814B, and 814C), each in communication with one or more of the plurality of field instruments; a plurality of RTU communications systems 806 (illustrated as 806A, 806B, and 806C), each in communication with one or more of the RTUs 814; a SCADA communications system 804 in communication with the plurality of RTU communications systems 806; a SCADA system 802 in communication with the SCADA communications system 804; and wellfield analysis system 803 in communication with the SCADA system 802.
A membrane 830 may be associated with a subset of wellfield sites 810 and also in communication with SCADA system 802. An illustrative example of a membrane is provided in
The SCADA system 802 is configured to receive a first measurement of the tracer solution that is added a first wellfield site and a second measurement of the tracer solution that is detected at a second wellfield site, measured by the plurality of field instruments.
In some examples, the wellfield management system 800 establishes a feedback loop between the SCADA system 802 and one or more of the plurality of groundwater wells 810. The SCADA system 802 monitors wellfield parameters measured by the plurality of field instruments at each groundwater well 810, such as well discharge rate, water level elevation, water pressure, and other well and pump operational factors.
The SCADA system 802 is configured to send signals back, in real time, to the plurality of RTUs 814 to start, stop, or otherwise adjust the production rate of the water pumps in the individual groundwater wells 810. In one embodiment, each of the plurality of groundwater wells comprises a variable frequency drive (VFD) that can be started, stopped, or varied by the associated RTU 814. In another embodiment, each of the plurality of groundwater wells comprises a SCADA-controlled valve on the well discharge that can be modulated to achieve a specified flow rate from the well.
Wells 810 may comprise injection wells, down gradient production wells, and monitoring wells. In some examples, a subset of these wells may be communicatively coupled with the SCADA system for monitoring or adjusting operation of the wells (e.g., increasing or decreasing production, etc.). The subset of wells may be grouped by type or location (e.g., injection well and monitoring well in a particular environment).
In addition to the extrinsic tracer solution, an intrinsic tracer solution may also be monitored and analyzed. The intrinsic tracer solution may include one or more of, for example, electrical conductivity (EC), Total Dissolved Solids (TDS), iron, manganese, chloride, and sulfate. Other intrinsic tracer solutions may be implemented and these intrinsic tracer solutions are provided for illustrative purposes.
To analyze the intrinsic tracer solution, ambient water quality data may be used/collected and analyzed for distribution and temporal changes near the downstream monitoring well. For example, an ambient TDS concentration range can be defined by the average TDS concentration of the well prior to injection, plus or minus a standard deviation. Using this ambient TDS range, a TDS threshold can be defined. A TDS reading below the defined threshold should indicate tracer arrival.
Other features of the water system may also be monitored. For example, water flow rates to the lower aquifer via injection may be monitored using flow meters that are incorporated with groundwater wells. A transducer may be installed in the injection wells to measure water depth in the well over the course of testing. The level meter may be connected to a remote terminal unit (RTU) and report water level data to a SCADA system. Individual monitoring well casing may be equipped with a pressure transducer. Transducers may measure levels in the local aquifers for the testing process. Level transducers may also be installed in downgradient pumping wells, where feasible. Transducers may either be equipped with onboard data collection capability or may be connected to a local data logger. Transducers may either log data on onboard data loggers, which may be downloaded to a computer system (e.g., on a monthly or recurring basis) or may be connected to the web-based SCADA system and upload data to a cloud database associated with the system (e.g., automatically). Transducer settings may be periodically checked and calibrated using an electric sounder to verify depth to water. In some examples, a temporary weather station may be established to record climatic data before, during, and after the testing process to normalize the basin percolation rates. The weather station shall be equipped with a wind speed and direction sensor, ambient air temperature thermometer, a barometer, a relative humidity gauge, and a rain gauge for recording precipitation events. Data shall be continuously recorded, output to a data logger every hour, which may be connected to a web-based SCADA station where data may be automatically uploaded and can be viewed real-time and remotely.
Wellfield management system 900 may comprise processor 902, memory 904, pump communication kernel 908, unit measurement logical circuit 912, SCADA unit command logical circuit 914, prediction model circuit 916, action circuit 918, and production database 930.
Processor 902 executes computer-implemented instructions that are retrieved from memory 904 to perform functions described throughout the disclosure. For example, processor 902 may be configured to receive and process input data from one or more of wellfield sites 940. Processor 902 may execute instructions that determine an amount of tracer solution that is added at a first well (e.g., injection well) coupled to a membrane and determine the tracer solution collected at a second well (e.g., monitoring well). The operations of one or more of wellfield sites 940 may be adjusted to determine and process well data.
Memory 904 is used for storing data and computer-implemented instructions for processor 902. Memory 904 may include volatile memory such as random access memory (RAM), non-volatile read-only memory (ROM), and/or non-volatile memory such as complementary metal oxide semiconductor (CMOS) memory or electronically erasable programmable read-only memory (EEPROM).
Pump communication kernel 908 may communicate with the wellfield site 940 via network 950 to receive data from wellfield site 940. Unit measurement logical circuit 912 may receive data from field instruments 944 via pump communication kernel 908. Unit measurement logical circuit 912 may associate sensor data with measurements of well 946 at wellfield site 940 to help determine the data produced by field instruments 944 at wellfield site 940.
The data may comprise, for example, a measurement of a tracer solution and other data identified by sensors incorporated into field instruments 944. In some examples, pump communication kernel 908 may act as a central functional unit either integrated locally into well 946 at wellfield site 940 or implemented remotely on processor 902.
In some examples, local climatology may be determined. Wind speed, wind direction, ambient air temperature, barometric pressure, relative humidity, and precipitation at the site may be continuously measured and recorded to a data logger at hourly intervals using a temporary weather station. Readings may be stored within a data logger in corresponding units for each parameter, and may be either connected to the cloud-based SCADA system or downloaded (e.g., on a monthly basis or automatically).
In some examples, the inflow rate to the injection wells may be determined. Inflow volumes, as well as starting and stopping dates and times, may be recorded using the existing flow metering and SCADA system and provided in electronic format on a weekly basis during the testing program.
In some examples, the injection well surface water depth may be determined. The depth of surface water in the injection wells utilized during the testing process may be measured using a pressure transducer, which may either be connected to a cloud-based SCADA system or downloaded on a weekly basis. Injection well water levels may be recorded and used to verify the injection well level meter readings.
In some examples, the groundwater level measurements may be recorded by electronic pressure transducers installed in each monitoring well. The transducers may measure water levels in each primary aquifer before, during, and after the testing process that adds the tracer solution to the water system absent releasing the tracer into the surrounding environment during the testing process.
In some examples, water levels may also be verified. The water levels may be verified on a weekly basis using an electric water level sounder. The electric water level sounder may be calibrated to the nearest 0.01 ft relative to an established reference point (RP) at the top of each well casing or sounding tube. Groundwater level measurements may be compared in the field to previous measurements. The process may re-measure these water levels if any of the measurements are significantly different from previous measurements or different from each other to confirm that the measurements were properly determined and stored.
In some examples, measurements may be recorded by a user. For example, the user may record the measurements within a proximate distance of the well with an ink pen on the appropriate form and may be converted to groundwater elevations by subtracting the depth to water from the reference point elevation. Data collected by the transducers may be downloaded either weekly (e.g., beginning 30 days prior to the start of the testing process using the tracer solution) for a period of five months, or may be connected to a SCADA system and downloaded to the web-based database.
SCADA unit command logical circuit 914 may generate a command signal to alter pumping at the wellsite. For example, the command signal may initiate an adjustment of a variable pump (e.g., a variable frequency drive (VFD)) that can be started, stopped, or varied by the associated RTU 814) at the wellsite to increase or decrease the pump flow. In some examples, the command signal may adjust the VFD or modulating valve in the well discharge in accordance with a step drawdown test such that the pump flow can be automatically reduced or stopped based on the system pressure sensed by field instruments 944.
Prediction model circuit 916 may determine a groundwater model that electronically simulates the concentration amount of tracer solution based on time and/or distance. For example, the groundwater modeling may simulate the addition of a tracer slug at an injection well and then predicted the tracer concentration over time in monitoring wells. Tracer dilution in groundwater may be determined to ensure that tracer concentrations at the downstream monitoring point(s) are adequately above analytical detection limits so that a travel time can be reliably calculated. Furthermore, groundwater modeling informs the potential range of travel times at downstream monitoring points, which may help control costs in tracer sampling. In some examples, modeling dilution factors in downstream monitoring points may help determine the safety factors in the amount of tracer solution added to the injection wells to ensure that the tracer is “found” in the monitoring points and the test does not need to be repeated.
Tracer concentrations in downgradient monitoring points may be determined using a focused ground water model. The ground water model built for each site and is calibrated using a number of different approaches. For example, various characteristics of the water (e.g., the speed or temperature of the water) may be measured with respect to time series data. The characteristics of the water may affect the concentration of a tracer solution that is available in the water, by increasing or decreasing the amount of concentration over time. The correlation of the characteristics of the water over time may be used to train the machine learning model. When new data is received for the well that identifies new characteristics of the water, the output of the model may predict the concentration of the tracer solution with respect to those characteristics.
In some examples, the model may determine one or more tracer breakthrough profiles. To bracket the range of dilution factors and travel times (e.g., in accordance with the time series data), two different scenarios may be run based on assumptions of a high and low effective aquifer porosity. The range of effective porosities may be based on pumping test data from wells in the area (e.g., with similar elevation and water system components), and represent a reasonable boundary of the actual conditions. This process may help calibrate the machine learning model for predicting a tracer solution.
The initial mass of tracer solution may be injected in the upgradient injection well. The initial concentration of tracer solution in groundwater after injection may be used to generate a chart, as shown and described with
Action circuit 918 may initiate an action based on the concentration amount of tracer solution found during the testing process. For example, the water can be used as drinking water. In some examples, the output of the tracer test may help satisfy a regulatory requirement and/or the data may be used to complete a report that is provided to a regulatory agency. In some examples, the output of the tracer test can measure how long it takes water that is either injected or percolated to travel from a source point to a downgradient monitoring point. The action associated with the use of the measured tracer curve at the downstream monitoring point can identify the travel time between the two points and, in some examples, can be used to determine how much disinfection of recycled water (injected or percolated) is required for create safe water for various uses.
Production database 930 may store data received from the wellfield site 940. One or more circuits may access production database 930 to retrieve and analyze data that is stored within production database 930.
Wellfield site 940 may correspond with programmable control unit 942, one or more field instruments 944, well 946, and interface 948, and wellfield site 940 may be coupled with membrane 960. A plurality of wellfield sites 940 may be in communication with wellfield management system 900 to transmit sensor data from the field instruments and receive instructions for automated operation or testing of each corresponding well 946.
Programmable control unit 942 may correspond with the remote terminal units (RTU) 814 and/or variable frequency drives (VFD) that can be started, stopped, or varied by an associated RTU 814, as illustrated in
Field instruments 944 may comprise one or more well sensors for determining measurements associated with well 946. Sensor input may comprise either discrete or continuous form, or an accommodation of both. Discrete input may be generated from photocells, pushing buttons, micro switches, limit switches, proximity switches, shaft encoders, optional scales, pressure switches, power meters, and the like. Continuous input may be generated from thermocouples, wellfield site transducers, voltmeters, and the like.
In some examples, field instruments 944 may comprise loop power. For example, pressure, level, and flow devices may be loop-powered. The sensor data may comprise flow rate of abstracted water, surface pressure of the well discharge, and groundwater level, which may be transmitted via network 950 to wellfield management system 900.
Well 946 at wellfield site 940 may correspond with a well type. The well types may correspond with one of injection wells, down gradient production wells, or monitoring wells. In some examples, well 946 may be an injection well that receives an addition of a tracer solution. The tracer solution may be added during the testing process, absent releasing the tracer into the surrounding environment during the testing process, then removing the tracer solution to a container after the testing process is complete such that the tracer solution helps to measure contaminants in the water.
Field instruments 944 may monitor well 946 (e.g., injection and monitoring) for changes in water level and tracer concentration. Samples may be collected using a submersible pump (e.g., 5 gpm). Samples of the tracer sample may be collected for analysis. The collection may comprise stripping the tracer solution gas from the water sample. The gas may be stripped into an ultra-pure nitrogen gas. The process may collect the gas directly into a container (e.g., pre-cleaned, Summa-type vacuum container). A sample volume may be collected using this method, which will provide lower analytical detection limits than would otherwise be possible by collecting a single sample at a single time period.
Once collected, the samples may be sent to a laboratory suited for low-level gas-phase analysis. The collected samples may not need to be analyzed once samples collected around the tracer peak are analyzed. The tracer solution may be analyzed using a Gas Chromatograph/Mass Spectrometer (GC/MS) method. If lower detection limits are needed, the tracer solution may be analyzed using a method that first cryogenically isolates and concentrates the tracer gas and then quantifies it using the GC/MS method. This method has the ability to detect the tracer solution at concentrations on the order of 1-100 nanograms per liter (parts per trillion).
Interface 948 may comprise a computer terminal with a keyboard and a monitor associated with wellfield site 940. In some examples, interface 948 may be implemented using a mobile device for accessing the data determined by the field instruments. In some examples, data are displayed locally at wellfield site 940 without transmission via network 950.
Network 950 may comprise the Internet, a Wide-Area Network (WAN), or a local-area network (LAN). Information is transferred via network 950 using communication protocols known in the art. One illustrative example of network 950 may include SCADA communications system 804 illustrated in
Membrane 960 may be associated with wellfield site 940 and also in communication with wellfield management system 900 (e.g., SCADA system 802) via network 950. An illustrative example of membrane 960 is provided with
The model may simulate or predict the dilution of the tracer solution incorporated as a tracer slug upon adding the tracer slug into the water supply at an injection well. The predicted tracer concentration over time may correspond with the tracer solution at the monitoring wells when the concentration amount of tracer solution is determined at some later time and distance.
In some examples, the model may determine the tracer solution in groundwater at the downstream monitoring point(s). The determination of the concentration of tracer solution at the downstream well may be determined to ensure that tracer concentrations are adequately above analytical detection limits so that a travel time can be reliably calculated.
In some examples, the model may inform the potential range of travel times at downstream monitoring points. This can be used to determine a correct amount of tracer solution to add to the slug to minimize waste and control costs in tracer sampling. In some examples, the modeling dilution factors in downstream monitoring points allows determination of the needed safety factors in the amount of tracer solution that is added to the injection wells to ensure that the tracer solution is determined at a detectable concentration amount in the monitoring points and the test does not need to be repeated.
Different tracer solution profiles may be determined by the model, including model-predicted breakthrough curves in downgradient wells assuming a low range (0.15) of effective aquifer porosity. Some tracer profiles indicate a dilution factor (C/CO) and a tracer concentration. A horizontal scale represents the time since the tracer was injected into the upgradient monitoring wells.
The dilution factor expressed as normalized concentration (C/CO), shown for each downstream monitoring locations represents how much dilution will occur at each of the downstream measuring locations. For an initial 50-lbs tracer solution/slug combination that is added to an injection well, the dilution factor (C/CO) may be on the order of 2-3 orders of magnitude and 3-4 orders of magnitude.
In some examples, the initial amount of tracer solution may be added during the testing process based on a tracer profile. This determined initial amount may help ensure detection downstream can be back-calculated based on the analytical detection limit of the method used to measure the tracer solution in the monitoring wells, which is on the order of 0.1 ug/L. In some examples, tracer profiles suggest adding a particular amount of tracer solution (e.g., 50 lbs of tracer solution) to result in detectable levels when the tracer solution is collected. The amount of tracer solution may be adjusted (e.g., to ensure adequate resolution of the tracer in downstream monitoring points).
In some examples, the model-predicted profile is shown along with vertical lines indicating time where 10% of tracer mass has been measured and the time where tracer peak is measured.
DDW establishes underground retention time based on the first 10% of the tracer peak concentration rather than using the highest peak value, or mean tracer concentration. When a mass of tracer is added in a single spiking event and then monitored at a downstream well, the tracer profile occurs as a peak where the mean travel time is taken at the tracer peak. Depending on the residence time, dispersion, and mixing, the measured tracer peak in the down-gradient well may occur over a relatively short duration with little “tailing” or it may occur as a flatter profile with substantial tailing before and/or after the tracer peak.
Tracer data may be analyzed by first determining the total mass of tracer measured in the sampling point by summing the measured concentration multiplied by the respective flow volumes. Once the total tracer mass has been determined, a tracer profile curve may be determined. For example, the tracer profile curve may comprise a non-ideal plug flow and mixing model. The residence time may be established corresponding to 10% of the tracer peak.
Although the disclosed technology is described above in terms of various exemplary embodiments and implementations, it should be understood that the various features, aspects, and functionality described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed technology, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the technology disclosed herein should not be limited by any of the above-described exemplary embodiments.
