Diagnostic system directly connected to a geothermal subterranean formation

Abstract

An apparatus, system, and method for using a tracer in a geothermal energy recovery operation including introducing the tracer into a subterranean formation, introducing a heat recovery fluid into the formation, collecting the fluid from the formation, measuring the concentration of the tracer in the fluid, and reporting results of the measuring within 24 hours. The measuring may use an instrument such as a gas chromatograph, a mass spectrometer, or a liquid chromatograph. In some embodiments, the collecting, measuring, and reporting occur within 200 yards of each other. Some embodiments may use a computer to control the collecting, measuring, and reporting and may record the time of the collecting and measuring the tracer concentration. Reporting the measurement results may include remote communication. Collecting the fluid may include flowing the fluid through a multiplexing valve that may also introduce calibration gas, blank gas, carrier gas, or a combination.

Description

[0001] DIAGNOSTIC SYSTEM DIRECTLY CONNECTED TO A GEOTHERMAL SUBTERREAN FORMATION Priority Claim

[0002]

[0001] This application benefits from and claims priority to United States Provisional Patent Application Serial Number 63 / 636,771 with the same title and inventors filed on April 20, 2024. This application is incorporated by reference herein in its entirety.

[0003] Background

[0004]

[0002] The recovery of heat from geothermal wells provides low cost, less environmentally damaging energy than some other energy sources. Geothermal energy production involves a complex process that begins deep underground, where reservoirs of hot water and steam are trapped in porous rock formations. These reservoirs are heated by the Earth's internal heat and magma. The temperatures within these reservoirs can vary depending on depth and location but generally range from around 100 °C to over 370 °C.

[0005]

[0003] Tracers are often used in geothermal applications to understand the behavior of fluids within geothermal reservoirs. These tracers are typically chemical compounds that are injected into the geothermal reservoir alongside the geothermal fluid (such as water or steam). Once injected, these tracers can help scientists and engineers track the movement of fluids, identify flow paths, and determine reservoir characteristics. Obtaining information from the use of tracers may take weeks or months as a sample is collected at a wellsite, distributed to a remote lab, and tested. This process takes up to fourteen days or longer depending on the remoteness of the field location. Someone has to physically catch samples of the produced fluids in a sample container, prepare those samples for shipping, move them to a collection hub, transport them by courier to a lab, receive them at the lab, analyze the samples and report the data to the client. Distribution of the lab test results to a wellsite operator and adjustment of an operation in response to the test results may take so long that the reliability of the conclusions about the formation based on the test results may be unfortunately diminished.

[0006]

[0004] Ongoing research and development efforts in this field aim to optimize geothermal energy production for sustainable and efficient electricity generation. Methods to confirm effective operation, to identify information about the reservoir, to confirm information about the heat transfer properties of the operation, and to characterize the system quickly and remotely are needed. Figures

[0007]

[0005] Figure 1 provides a schematic view of a a geothermal energy system.

[0008]

[0006] Figure 2 provides a schematic view of an instrument connected to a reservoir.

[0009]

[0007] Figure 3 provides a schematic view of the connections and components within an instrument.

[0010]

[0008] Figures 4A and 4B provide schematic views of the components of an embodiment of a multiplexing valve at two different times of its operation.

[0011]

[0009] Figure 5 is a plot of tracer concentration as a function of time comparing fluid collected from rock with fracture characteristics and rock with matrix characteristics.

[0012]

[0010] Figure 6 is a plot of tracer concentration as a function of time comparing fluid collected from rock with good heat transfer and rock with poor heat transfer.

[0013] Summary

[0014] [Oi l] This summary is provided to comply with 37 C.F.R. § 1.73, requiring a summary of the invention briefly indicating the nature and substance of the invention. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

[0012] Embodiments herein relate to an apparatus, system, and method for using a tracer in a geothermal energy recovery operation including introducing the tracer into a subterranean formation, introducing a heat recovery fluid into the formation, collecting the fluid from the formation, measuring the concentration of the tracer in the fluid, and reporting results of the measuring within 24 hours of collecting the fluid.

[0015]

[0013] In some embodiments, the measuring uses an instrument such as a gas chromatograph, a mass spectrometer, or a liquid chromatograph. In some embodiments, the collecting, measuring, and reporting occur within 200 yards of each other. Some embodiments may use a computer to control the collecting, measuring, and reporting. Some embodiments may record the time of the collecting and measuring the tracer concentration. Reporting the measurement results may include remote communication.

[0016]

[0014] In some embodiments, collecting the fluid includes flowing the fluid through a multiplexing valve. The multiplexing valve may also introduce calibration gas, blank gas, carrier gas, or a combination thereof to the fluid.

[0017]

[0015] The tracer may include fluorescent dye, ionic tracer, inorganic compounds, radioactive tracers, organic compounds, chemical mixtures, naphthalene sulfonic acid, or a combination thereof. Some embodiments may introduce a second tracer to the formation. Some embodiments may measure the concentration of the second tracer. Some embodiments may report results for measuring the tracer and the second tracer within 24 hours of collecting the fluid.

[0018] Detailed Description

[0019]

[0016] Overall, tracers play a crucial role in characterizing geothermal reservoirs, optimizing reservoir management strategies, and improving the efficiency and sustainability of geothermal energy production. Embodiments herein relate to collecting chemical composition and concentration information that inform how to better manage a geothermal reservoir. By directly connecting a diagnostic system to a geothermal reservoir, engineers have an accurate and faster system to track the movement of fluids, identify flow paths, determine reservoir characteristics, and optimize heat energy transfer.

[0020]

[0017] To harness this geothermal energy, production wells are drilled into geothermal reservoirs to access the hot water and steam to support a geothermal energy recovery operation. As the geothermal fluid is brought to the surface through these wells, it undergoes steam separation. The steam and water are separated, with the steam directed to the geothermal power plant for electricity generation, while the water is reinjected into the reservoir to maintain pressure and sustain the resource's longevity. Embodiments and methods described herein begin with the injection of a suite of tracers into the geothermal reservoir. Tracer concentrations will be continuously monitored via diagnostic instrumentation throughout the system and derived to further understand the reservoir. Additional unique tracers may be applied during the reinjection process to understand additional information about the reservoir and sweep efficiencies.

[0021]

[0018] Geothermal power plants come in various types, each with its own operational characteristics suited to different reservoir conditions:

[0022]

[0019] Dry Steam Power Plants utilize steam directly from the geothermal reservoir. The steam is piped directly from the production wells to drive turbines connected to generators, converting the steam's kinetic energy into electrical energy.

[0023]

[0020] In flash steam power plants, high-pressure hot water from the reservoir is released into lower pressure tanks or "flash tanks." The sudden pressure drop causes some of the water to instantly vaporize into steam, which is then used to drive turbines and generate electricity.

[0021] Binary cycle power plants utilize lower temperature geothermal reservoirs by pairing them with a secondary fluid with a lower boiling point, such as isobutane or isopentane. The heat from the geothermal fluid is transferred to the secondary fluid, causing it to vaporize and drive turbines, thus generating electricity.

[0024]

[0022] Once the steam has passed through the turbines and generated electricity, it undergoes condensation. The steam is cooled and condensed back into water, which is then reinjected into the geothermal reservoir through injection wells. This reinjection process completes the cycle and ensures the continuous circulation of the tracer and fluid within the reservoir. The detailed integration of geothermal energy production with tracer usage underscores the complexity and interdisciplinary nature of geothermal resource exploration and utilization.

[0025]

[0023] A diagram of a geothermal energy system can be found in Figure 1. A geothermal energy recovery operation 101 includes a heat source 102, often hot rock, that heats hot water containing region 103 to temperatures that form steam in the steam containing region 104. The heat source 102, hot water region 103, and steam region 104 are all within the subterranean formation. The power plant 105 may inject heat transfer fluid, such as water, through an injection well 106 into the hot water region 103 and may collect heat transfer fluid, such as steam, through recovery well 107.

[0026]

[0024] Tracers may be injected into the geothermal reservoir at different locations to determine how fluids flow within the reservoir. By analyzing the concentration of tracers at various points, reservoir engineers can map out flow paths and understand the movement of fluids underground. Tracers can also help estimate the volume of the geothermal reservoir by tracking the dispersion and dilution of the injected tracer within the reservoir. This information is often crucial for understanding the size and extent of the reservoir.

[0027]

[0025] In some embodiments, tracers with known reaction rates or decay rates may be used to estimate the temperature of the geothermal reservoir. By monitoring changes in the concentration of these tracers over time, engineers can infer the temperature of the reservoir fluid.

[0028]

[0026] Tracers may also be used to determine the connectivity between various parts of the geothermal reservoir. By injecting tracers into one part of the reservoir and monitoring their presence in nearby wells, researchers can assess the degree of connectivity and identify barriers or channels that may affect fluid flow.

[0027] In some embodiments, tracers help optimize the placement and design of production and injection wells in geothermal reservoirs. By studying tracer movement, engineers may determine the most effective locations for wells to maximize fluid production or injection efficiency.

[0029]

[0028] The temperature of the geothermal resource is a crucial factor in determining the efficiency and feasibility of geothermal energy production. Higher temperatures generally result in higher energy output and efficiency in electricity generation. However, even moderatetemperature geothermal resources can be valuable for direct heating applications and power generation using binary cycle plants, making geothermal energy a versatile renewable energy source.

[0030]

[0029] Low-temperature geothermal resources have temperatures below 100 °C (212 °F). They are often used for direct heating applications such as district heating systems, greenhouse heating, and spas.

[0031]

[0030] Medium-temperature geothermal resources have temperatures ranging from around 100 °C (212 °F) to 150 °C (302 °F). They are suitable for both direct heating and electricity generation using binary cycle power plants.

[0032]

[0031] High-temperature geothermal resources have temperatures exceeding 150 °C (302 °F). They are primarily used for electricity generation in dry steam and flash steam power plants.

[0032] Selecting suitable tracers for geothermal applications involves considering various factors, including the specific objectives of the tracer study, the characteristics of the geothermal reservoir, and the analytical techniques available for tracer detection and measurement. The key considerations for determining which tracers are suitable are listed below.

[0033]

[0033] Chemical Stability: Tracers may be selected to be chemically stable under the conditions present in the geothermal reservoir including high temperatures, pressure, and potentially corrosive environments. Chemical stability ensures that the tracer remains intact and does not undergo undesired reactions or degradation during the study period.

[0034]

[0034] Detectability: Tracers may be selected to be detectable at low concentrations using analytical techniques available for tracer detection and measurement. Common detection methods include spectrophotometry, chromatography, mass spectrometry, and fluorescence detection. The tracer concentration may be tailored to be measurable with high precision and accuracy to enable accurate tracking and quantification of tracer movement.

[0035] Non-reactivity: Tracers may be selected to be non-reactive with the geothermal fluid and reservoir rock to avoid altering fluid composition or reservoir characteristics. This ensures that the tracer behaves independently and accurately reflects fluid movement within the reservoir.

[0036] Safety and Environmental Considerations: Tracers may be selected to be safe to handle and environmentally benign to minimize risks to personnel and ecosystems. Toxic or environmentally harmful tracers should be avoided, especially in cases where tracers may be injected into the reservoir.

[0035]

[0037] Compatibility with Injection and Sampling Systems: Tracers may be selected to be compatible with injection and sampling systems used in geothermal wells. This includes considerations such as solubility, viscosity, and compatibility with injection fluids and materials.

[0038] The tracer should have an appropriate lifetime within the reservoir to allow for sufficient tracking of fluid movement and accurate analysis of tracer data. Tracers with long half-lives may provide extended tracking capabilities, while tracers with short half-lives may offer rapid feedback on fluid dynamics. In some embodiments, the instrument may measure the concentration of degradation products of a tracer in addition to the tracer concentration. The concentration of tracer degradation chemicals may also inform how the tracer is flowing through rock and what temperatures the tracer chemical has experienced.

[0036]

[0039] By evaluating these factors and considering the specific requirements of the tracer study, engineers may select tracers that are most suitable for their geothermal application and objectives. It is often beneficial to conduct laboratory tests and feasibility studies to assess the performance of potential tracers under simulated reservoir conditions before conducting fieldscale tracer experiments.

[0037]

[0040] There are several chemicals commonly used as tracers in geothermal applications due to their suitability for tracking fluid movement in geothermal reservoirs. Some of these chemicals include the following.

[0038]

[0041] Fluorescent Dyes: Fluorescent dyes may be selected because of their high detectability at low concentrations and compatibility with analytical techniques such as fluorescence spectroscopy. Fluorescent dyes may be injected into the geothermal reservoir and detected using fluorescence detection methods to track fluid movement.

[0042] Ionic Tracers: Ionic tracers, such as bromide (BrA-) and iodide (IA-) ions, are commonly used in geothermal tracer studies. These ions are chemically stable, non-reactive with geothermal fluids, and easily detectable using ion chromatography or spectrophotometry.

[0039]

[0043] Inorganic Compounds: Inorganic compounds like lithium chloride (LiCl) and lithium bromide (LiBr) are frequently used as tracers in geothermal reservoirs. These compounds are thermally stable, compatible with geothermal fluids, and have distinct chemical signatures that allow for accurate detection and quantification.

[0040]

[0044] Radioactive Tracers: Radioactive tracers, such as tritiated water (H3A3O) or isotopes of noble gases like helium-3 (He-3), can provide valuable information about fluid movement and residence times in geothermal reservoirs. These tracers emit characteristic radiation that can be detected using specialized equipment such as gamma spectrometers or scintillation detectors.

[0045] Organic Compounds: Some organic compounds, such as ethyl acetate or acetone, have been used as tracers in geothermal studies. These compounds are selected based on their stability, detectability, and compatibility with geothermal fluids.

[0041]

[0046] Chemical Mixtures: Tracer mixtures consisting of multiple chemicals or isotopes are sometimes used to enhance tracer detection and tracking capabilities. These mixtures may include combinations of fluorescent dyes, ionic tracers, and other chemical compounds tailored to specific study objectives.

[0042]

[0047] Naphthalene sulfonic acids, known as NSAs, such as Naphthalene- 1 -sulfonic acid and Naphthal ene-2,6-disulfonic acid, are among the chemicals that have been used as tracers in geothermal applications. These compounds offer stability, solubility, and detectability, making them suitable candidates for tracking fluid movement within geothermal reservoirs. NSAs are highly soluble in water which facilitates their injection into the geothermal reservoir and dispersion within the reservoir fluid. Their solubility allows for accurate tracking of fluid movement and detection of tracer concentrations using analytical techniques.

[0043]

[0048] In some embodiments, fluorinated benzoic acids, such as 1 -fluorobenzoic acid or 2- fluorobenzoic acid can be used as tracers in geothermal applications. These compounds offer solubility and detectability. The stability of these compounds is typically lower than NSAs at geothermal reservoir temperatures. Engineers selecting these chemicals for geothermal applications may evaluate the stability for the conditions at hand before deploying to the field.

[0049] The selection of tracers depends on factors such as the objectives of the tracer study, the characteristics of the geothermal reservoir, and the available analytical techniques. Engineers may conduct feasibility studies and laboratory tests to evaluate the performance of potential tracers under simulated reservoir conditions before conducting field-scale tracer experiments. Additionally, safety and environmental considerations may be carefully assessed when selecting tracers for geothermal applications.

[0044]

[0050] Tracers may be detected and quantified using various analytical techniques, such as chromatography (e.g., high-performance liquid chromatography, HPLC) and spectrophotometry. These methods allow for precise measurement of tracer concentrations in geothermal fluids and reservoir samples.

[0045]

[0051] Figure 2 shows an instrument 201 connected directly to a geothermal system on the surface of the earth 202. In some embodiments, the instrument 201 is the size of a carry-on suitcase with approximate dimensions of 22 inches x 14 inches x 9 inches. Internal components (not shown individually) include a gas-chromatograph, or a liquid chromatograph, with a packed or capillary column, an oven, a high-pressure pump, insulation, a detector, either electron-capture, flameionization, mass spectrometer, uv-vis, or ion-mobility spectrometer, a multiplexing valve, a computer, over-the-air communications electronics, and connection ports. Some embodiments may include a combination of internal components such as a gas or liquid chromatograph and mass spectrometer. All these components (not shown individually) are configured within the case of the instrument 201. In some embodiments, the instrument 201 with its internal components may be configured in a cargo trailer. The instrument 201 will include carrier gas or carrier fluid, either nitrogen or helium, acetonitrile, calibration gases, and blank gases.

[0046]

[0052] In some embodiments, the instrument is manufactured by and is commercially available from Agilent of Santa Clara, California, Thermo Fisher Scientific of Waltham, Massachusetts, the multiplexing valve manufactured by and is commercially available from VICI of Houston, Texas, and the connection ports manufactured by and are commercially available from Grainger of Lake Forest, Illinois.

[0047]

[0053] Figure 2 shows a fracture, most likely a hydraulic fracture 207 with a region infused with a tracer 208 permeated by a well 209 that may be horizontal or vertical or both. The well 209 exits the earth 202 and its collected fluid is controlled by the wellhead 210. The fluid then flows through separator 211 as it flows on toward the needle valve 204. The instrument 201 is connected to the system 203 via the needle valve 204. Fluid that does not flow to the instrument 201 may pass through a line meter 205 on to a line 206 to the main sales line, stock tank, or power plant. In some embodiments, the instrument 201 and wellhead 210 are positioned within 200 yards of each other.

[0048]

[0054] A case diagram is shown in Figure 3. As the fluid and tracer flow through the geothermal system some fluid will pass through the needle valve 204 (not shown in Figure 3) via line and connection 301 and enter the instrument 302. Fluid will pass through the multiplexing valve 303 into the instrument 302 where the tracer molecules will be separated then into the chromatograph or other measurement device 304 and the detector 305 where the tracer molecules will be quantified. The multiplexing valve 303 may also deliver calibration gas 307, blank gas 308 , and carrier gas 309. A computer 310 collects information and controls the valve 303, measurement device 304, and detector 305 and sends information to the communications electronics 311. After passing through the detector 305, the fluids will be collected via a vent line 306. In some embodiments, a pump (not shown) is necessary to draw a small amount of geothermal sample fluid from the system and pass it through the multiplexing valve 303. A reservoir of rinsing fluid (not shown) can be used to clean the injection system and get the system ready for the next geothermal fluid sample. In some embodiments, the computer 310, communication electronics 311, measurement device 304, and wellhead (not shown in Figure 3) that provides fluid to the line and connection 301 are positioned within 200 yards of each other. Thus, collecting of fluid, measuring a concentration of tracer, and reporting the measurement results may all occur within 200 yards of each other.

[0049]

[0055] In preparation for sampling NSA tracers or other tracers from a geothermal production line, it is important to ensure that the fluid is appropriately conditioned for accurate HPLC analysis. Samples may be collected at a surface-accessible point, such as downstream of the separator or directly from the production line after pressure drop but upstream of any flash point that could alter the tracer profile. Prior to collection, the sample flow through a temperature control device such as a stainless steel cooling coil or a compact heat exchanger to bring down the temperature to protect sample integrity and ensure compatibility with materials and the analytical system.

[0050]

[0056] To remove particulates that may interfere with chromatography or adsorb tracer compounds, the sample may be filtered in-line, for example, through an PTFE membrane immediately before collection. When working with geothermal fluids, this step may be high priority because geothermal fluids often carry dissolved solids, silica scaling, or corrosion byproducts.

[0051]

[0057] The multiplexing valve allows for multiple inputs and one output. By closing off all the inputs but one then cycling to the next input, multiple flow streams can be sampled with one instrument. Figures 4A and 4B show the flow paths of an eight-input multiplexing valve 403. In Figure 4A, the fluids are coming into input 1 via flow line 404, through connection 405, and exiting through the output 401 at the center 402 of the valve. Inputs 2-8 remain closed to flow. In Figure 4B, the valve 403 has switched to connect input 2 via flow line 406, through connection 405, and exiting through the output 401 at the center 402 of the valve while closing inputs 3-8 and 1.

[0052]

[0058] The entire system is controlled by the computer. It executes three major processes: operation of the instrument, quantification of the tracers, and transmission of the data. The computer tells the multiplexing valve when to open and rotate, and when to activate the instrument. It quantifies the raw data from the instrument into time, date, and concentration of the tracer. It then prepares the data to be sent over-the-air via the communications electronics of the communication system. The communications system takes the data in packets, encrypts them, and transmits them via cell signal to a receiving computer or computer network.

[0053]

[0059] The diagnostic system further includes a data delivery platform which consists of time, date, and concentration outputs of the tracers from the instrument as well as well diagrams, field diagrams, formation diagrams, flowback schedules, production data, pressure data, and flowback data. The system together enables engineers to make decisions and changes to their operations in real time and validates whether their changes are effective.

[0054]

[0060] The instrument will be connected to the well or wells where the tracers are expected to be produced. In some embodiments the instrument will be placed within the power plant upstream of the electricity making equipment.

[0055]

[0061] If there are multiple geothermal wells constructed in the same location, the instrument will be placed between the flow lines of the group of wells.

[0056]

[0062] Power for the instrument will come from existing electricity sources at the field location, a battery pack, or a battery pack with solar charging capability. The power options will be determined by the field location and what is most accessible.

[0057]

[0063] The operator will set the instrument to begin running on a schedule; this can be done by directly connecting to the instrument or remotely connecting to the instrument. The instrument and its communication electronics are accessed from anywhere in the world via satellite signal. Once sampling is initiated the multiplexing valve will open and allow 1 microliter of fluid into the system. This will be joined by 10 microliters of carrier fluid. The sample will then travel with the carrier gas into the gas or liquid chromatograph, then into the detector and finally deposited into a collection chamber or vented to the atmosphere. In some embodiments, the geothermal sampling fluids may be piped back into the system via a lower pressure vessel such as a dump chamber. In some embodiments, it is necessary to pressure the geothermal sampling fluids with a centrifugal pump or peristaltic pump so that the fluids have sufficient pressure to flow back into the system.

[0064] The system computer will record the data from a run and convert the raw data into time, date, and concentrations present of each tracer, if there are tracers present in the sample. This sample analysis takes less than thirty minutes. In some embodiments, the duration of less than about 30 minutes is needed to analyze the fluid coming from the geothermal well. In some embodiments, the more of the tracer passing through the detector the higher the concentration.

[0058]

[0065] These data will then be encrypted and sent to the data collection platform via satellite signal and the communication electronics. This means that tracers coming out of the reservoir minutes earlier are run through the instrument, analyzed, quantified, and delivered to the client in near real time. In addition, this can be done with multiple wells producing tracers by simply rotating the multiplexing valve. The multiplexing valve will rotate to allow fluids from the next well in the collection and the cycle will repeat. In some embodiments, this is all done automatically according to a schedule set by the instrument operator and may be controlled from anywhere in the world. The instrument operator may connect to the instrument like any networked computer, log into operating system, open the instrument control software and set the run schedule. In some embodiments, his instructions may include the positions the multiplexing valve will take and when, when a run will start and when the instrument is finished for the day. In some embodiments, the system analyzes reservoir fluids in real time, essentially connected to the reservoir, and the system schedule is modified by remotely connecting into the instrument.

[0059]

[0066] Since the system is operating in real time and not delayed waiting for samples being shipped and analyzed in a lab, several actions can be taken that were not possible before this technology. When optimizing the initial flow of a geothermal system, its load recovery and flow profiles may be analyzed in real time.

[0067] That is, tracer concentration measurements are integral to diagnosing heat transfer efficiency and reservoir characteristics in geothermal systems. The primary goal of tracer application is to understand the fluid flow pathways, determine fluid residence times, identify reservoir connectivity, and indirectly evaluate heat transfer effectiveness between injection and production wells.

[0060] M= C TargetxQxt

[0061] M = Mass of tracer needed (grams)

[0062] CTarget= Expected tracer concentration at production well (ppb) detectable by HPLC

[0063] Q = Geothermal fluid flow rate (L / hr) t = Anticipated tracer duration or expected breakthrough time (hours)

[0064]

[0068] Initially, careful consideration is given to determining the quantity of tracer applied, typically using a mass-balance approach. The tracer mass required is calculated by multiplying the expected target concentration (detectable by analytical methods, typically in the range of 5- 10 parts per billion, ppb) by the geothermal fluid flow rate and the anticipated fluid residence or breakthrough time. A safety factor (usually 1.5 to 2 times the calculated value) is added to ensure tracer detectability after dilution in the reservoir.

[0065]

[0069] For example, naphthalene sulfonic acid tracers in geothermal applications are may be introduced using a slug (pulse) injection method. This short-duration injection — lasting from minutes to several hours — clearly defines the tracer's breakthrough at the production well and simplifies subsequent data analysis. The tracer solution is carefully prepared at concentrations below saturation limits, injected precisely via surface metering pumps, and either directly introduced downhole through dedicated tubing or upstream of the injection pump. Precise recording of tracer mass, concentration, injection depth, and injection timing is essential.

[0066]

[0070] Samples are autonomously collected at defined intervals set by the computer. Tracer concentrations are analyzed using High-Performance Liquid Chromatography (HPLC) with ultraviolet detection. This technique provides precise quantification of tracer concentration (in ppb) through comparison against calibration standards, enabling detailed reservoir characterization of tracer breakthrough behavior.

[0067]

[0071] Interpretation involves plotting tracer concentration against time, resulting in breakthrough curves. These curves are analyzed for their peak arrival time, curve shape and tail, and overall tracer recovery. Good heat transfer and reservoir performance are indicated by moderate-to-long residence times, broad and symmetrical breakthrough peaks, and high tracer recovery (generally between 80-95%). This suggests uniform fluid flow and effective heat transfer through the reservoir. Conversely, sharp, narrow peaks with short arrival times and poor tracer recovery (less than 60%) indicate undesirable conditions, such as channeling or short-circuiting, leading to inefficient heat exchange. Through careful preparation, application, and interpretation, naphthalene sulfonic acid tracer concentrations measured via HPLC serve as an effective diagnostic tool to evaluate and optimize heat transfer performance in geothermal reservoirs.

[0068]

[0072] Figure 5 plots tracer concentration over 30 days for tracer A which was introduced to a reservoir with fractures and tracer B which was introduced to a reservoir with a matrix profile. The tracer concentration profile over the time period implies that tracer B’s rock is most likely in matrix profile while tracer A’s rock is most likely subject to a fracture.

[0069]

[0073] Figure 6 plots tracer concentration over 30 days for a tracer from rock surfaces that have good heat transfer and a tracer from rock surfaces that have poor heat transfer. Chart 1 compares good and bad heat transfer as shown in Figure 6.

[0070] Chart 1. Comparison of Good and Bad Scenarios

[0071]

[0074] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Nothing in this disclosure is to be construed as an admission that the embodiments described in this disclosure are not entitled to antedate such disclosure by virtue of prior invention. As used in this document, the term “comprising” means “including, but not limited to.”

[0072]

[0075] The present disclosure is not to be limited in terms of the particular embodiments described in this application, which are intended as illustrations of various aspects. This disclosure is not limited to the particular systems, devices and methods described, as these may vary. The terminology used in the description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions or biological systems, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0073]

[0076] With respect to the use of substantially any plural and / or singular terms herein, those having skill in the art can translate from the plural to the singular and / or from the singular to the plural as is appropriate to the context and / or application. The various singular / plural permutations may be expressly set forth herein for sake of clarity.

[0074]

[0077] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (for example, bodies of the appended claims) are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” et cetera). While various compositions, methods, and devices are described in terms of “comprising” various components or steps (interpreted as meaning “including, but not limited to”), the compositions, methods, and devices can also “consist essentially of’ or “consist of’ the various components and steps, and such terminology should be interpreted as defining essentially closed-member groups. It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present.

[0075]

[0078] For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to embodiments containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (for example, “a” and / or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations.

[0076]

[0079] As used in this document, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (for example, the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, et cetera). In those instances where a convention analogous to “at least one of A, B, or C, et cetera” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (for example, “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and / or A, B, and C together, et cetera). It will be further understood by those within the art that virtually any disjunctive word and / or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0077]

[0080] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0078]

[0081] As will be understood by one skilled in the art, for any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, et cetera. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, et cetera. As will also be understood by one skilled in the art all language such as “up to,” “at least,” and the like include the number recited and refer to ranges that can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member. Thus, for example, a group having 1-3 devices refers to groups having 1, 2, or 3 devices. Similarly, a group having 1-5 devices refers to groups having 1, 2, 3, 4, or 5 devices, and so forth.

[0079]

[0082] Various of the above-disclosed and other features and functions, or alternatives thereof, may be combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, each of which is also intended to be encompassed by the disclosed embodiments.

Claims

ClaimsWe claim:

1. A method for using a tracer in a geothermal energy recovery operation, comprising: introducing the tracer into a subterranean formation; introducing a heat recovery fluid into the formation; collecting the fluid from the formation; measuring the concentration of the tracer in the fluid; and reporting results of the measuring within 24 hours of collecting the fluid. The method of claim 1, wherein the measuring comprises using an instrument.3 The method of claim 2 wherein the instrument comprises a gas chromatograph. The method of claim 2, wherein the instrument comprises a mass spectrometer.5 The method of claim 2, wherein the instrument comprises a liquid chromatograph.6 The method of claim 1, wherein the collecting, measuring, and reporting occur within 200 yards of each other.7 The method of claim 1, further comprising recording the time of the collecting and measuring the tracer concentration.8 The method of claim 1, wherein the reporting comprises remote communication.9 The method of claim 1, further comprising using a computer to control the collecting, measuring, and reporting.10 The method of claim 1, wherein the collecting includes flowing the fluid through a multiplexing valve.11 The method of claim 1, wherein the multiplexing valve also introduces calibration gas, blank gas, carrier gas, or a combination thereof to the fluid.12 The method of claim 1, wherein the tracer comprises fluorescent dye, ionic tracer, inorganic compounds, radioactive tracers, organic compounds, chemical mixtures, naphthalene sulfonic acid, or a combination thereof.13 The method of claim 1, further comprising introducing a second tracer to the formation.14 The method of claim 13, further comprising measuring the concentration of the second tracer.15 The method of claim 14, further comprising reporting results for measuring the tracer and the second tracer within 24 hours of collecting the fluid.

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