Methodology for managing, analyzing and regulating a geothermal installation

Abstract

This presentation concerns a method for managing a geothermal installation, the geothermal installation being configured to meet the heat or cooling demands of at least one building or industrial or agricultural process, the method comprising: a measurement, at a certain sampling frequency, of hydraulic, thermal and / or chemical operating parameters of the installation, by measuring devices; a dated estimate of an indicator as a function of at least one measured operating parameter;and highlighting a possible malfunction of the installation by comparing the indicator estimate to a plurality of boundary conditions, said boundary conditions being a function of different assumptions relating to parameters extrinsic to the geothermal installation, and a selection, based on the result of this comparison, of at least one of these assumptions, in order to characterize the external cause of the anomaly. Figure for the abbreviation: Fig. 1;

Description

Title of the invention: Method for managing, analyzing and regulating a geothermal installation technical field

[0001] The present invention relates to the field of geothermal energy. More particularly, it relates to the management of geothermal installations configured to meet the heating or cooling demand of a building or industrial or agricultural process. PRIOR TECHNOLOGY

[0002] In order to meet the heat or cooling demands of at least one building on the surface, it is possible to implement a geothermal installation.

[0003] The geothermal installation may include a system of different types such as, for example, a geothermal heat pump (HP) system using groundwater, a heat pump (HP) system using vertical geothermal probes (VGP) or a geothermal heat pump (HP) system using baskets or walls...

[0004] A geothermal system circulates a heat transfer fluid through a borehole drilled in the subsoil to modify the temperature of the energy-consuming structure to which the geothermal system is connected. The geothermal system can thus heat the structure by transferring heat from the subsoil to it, or cool the structure by transferring heat from the structure to the subsoil.

[0005] However, malfunctions such as pipe blockage or variations in the subsoil's thermal capacity can occur during the operation of the geothermal system and cause deviations between the system's intended and actual operation. These deviations reduce the geothermal system's efficiency and may necessitate a temporary shutdown for maintenance, or even a permanent shutdown. GENERAL STATEMENT

[0006] One aim of the presentation is to avoid malfunctions or maintenance operations of the geothermal installation and thus enable continuous and efficient operation.

[0007] To this end, a method for managing a geothermal installation is proposed, according to one aspect of this exposition, the geothermal installation being configured to meet the heating or cooling demands of at least one building or industrial or agricultural process. The method comprises: - a measurement, at a certain sampling frequency, of hydraulic, thermal and / or chemical operating parameters of the installation, by at least one measuring device; - a dated estimate of an indicator that is a function of at least one measured operating parameter; and - highlighting a possible malfunction of the installation by comparing the indicator estimate to a plurality of boundary conditions, said boundary conditions being a function of different assumptions relating to parameters extrinsic to the geothermal installation, and a selection, based on the result of this comparison, of at least one of these assumptions, in order to characterize the external cause of the malfunction.

[0008] In particular, in the event of an anomaly, a corrective action (E6) on the installation is determined - and where appropriate ordered - based on the result of the comparison.

[0009] This process allows for efficient operation of the geothermal installation and upstream management of the causes of possible malfunctions in order to avoid them.

[0010] By continuously monitoring and independently analyzing each characteristic of the geothermal installation, the process makes it possible to identify the causes of the modification of a characteristic and thus avoid a malfunction by modifying the parameter in question.

[0011] Advantageously, but optionally, the described method includes at least one of the following features, taken alone or in any combination: - implementation of a corrective action on the installation according to the detected malfunction and the selected hypothesis;

[0012] - a real-time test of the reliability of the measurements of the operating parameters and the sampling frequency of these measurements is adapted according to the test results;

[0013] - real-time testing of the reliability of operating parameter measurements implements the following treatment: - discrete Fourier transform of the measurements of said operating parameter considered over a predetermined time interval, - calculation of a useful oscillating energy as a function of the Fourier transform of said operating parameter, - determination of the sampling frequency as a function of this oscillating energy;

[0014] - an estimated indicator is an indicator representative of a static level, the estimation of said indicator being a function of a piezometric measurement in the geothermal installation as well as a previously determined theoretical static level;

[0015] - the geothermal installation includes at least one injection well and at least one production well and in which the estimation of the indicator representing a static level implements: - a piezometric measurement of the injection well level and a piezometric measurement of the production well level; - a comparison between the two measurements,

[0016] and in which the indicator is an interval which includes the interval between the piezometric measurement of the injection well and the piezometric measurement of the production well, if the difference between the two measurements is less than a first predetermined threshold;

[0017] - the geothermal installation includes at least one injection well and at least one production well and an indicator is a representative indicator of a transmissivity between the production well and the injection well and the estimation of the indicator being a function of a flow rate of a fluid in the geothermal installation as well as a theoretical transmissivity previously recorded;

[0018] - the estimation of the representative transmissivity indicator includes: - a prediction of the piezometric level of the production well and / or injection well based on the measured fluid flow rate and transmissivity, - a comparison between the piezometry resulting from the forecast and a piezometric measurement of the injection well or a piezometric measurement of the production well, - a minimization of a difference resulting from the comparison;

[0019] - an indicator is a representative indicator of a blockage in the installation geothermal and is estimated based on a volume of fluid flowing through the geothermal installation as well as a theoretical fluid flow rate previously recorded;

[0020] - the estimation of the indicator representing clogging includes: - an estimate of a future specific flow rate based on the volume of fluid flowing and the theoretical fluid flow rate, as well as the characteristics specific to the fluid circulating in the geothermal installation, and - a calculation of a fluid volume before shutdown as a function of the estimated specific flow rate;

[0021] - the operating parameter is included in the following parameters: a flow rate of heat transfer fluid in the geothermal installation, a pressure of the fluid in a pipe of the geothermal installation, a volume of fluid that has circulated in the system;

[0022] - the indicator is included in the following list: a static fluid level in the subsoil, a transmissivity between a production well and an injection well, an effective or apparent thermal conductivity of the soil or a thermal capacity of the soil;

[0023] - the extrinsic parameters of the geothermal installation analyzed are included in the following parameters: soil permeability, presence of biochemical elements, operating parameters of nearby geothermal installations, environment of the geothermal installation, clogging of a pipe, meteorological evolution, energy consumption or energy losses of the structure;

[0024] - the geothermal installation is a geothermal installation on an aquifer, or of open type, or a geothermal installation on probe, or closed type, or a geothermal installation on compact exchangers.

[0025] According to another aspect, a set is proposed comprising a geothermal installation configured to meet the heat or cooling demands of at least one building or industrial or agricultural process and a geothermal installation management system, the system including means for measuring the operating parameters of the geothermal installation and being suitable for implementing the process described above. DESCRIPTION OF THE FIGURES

[0026] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0027] Fig. 1 illustrates an organizational chart of the steps of a possible implementation of the present presentation. DETAILED DESCRIPTION

[0028] Geothermal energy is used to enable heat exchange between the subsoil and a structure such as a building, a cold storage room in food warehouses, an industrial process (air conditioning and humidity control for production centers), an agricultural production greenhouse, any industrial process but at low temperature, a swimming pool heater... Hereafter, the structure requiring a geothermal installation will be called a building.

[0029] Geothermal energy can be implemented through various geothermal installations. A geothermal installation allows for the transport of heat between the subsoil and the building. A geothermal installation is therefore simply a device connecting a building and the subsoil. The geothermal installation is thus connected to the building's heating network on one side and to the subsoil via a borehole, or well, on the other. The connections of the geothermal installation to the building and the subsoil are configured to allow heat exchange between them.

[0030] Geothermal installation

[0031] The geothermal installation may include a circuit for a heat transfer fluid and a heat exchanger connected to the circuit. The circuit may include a pipe and a circulation pump for controlling the flow rate of the fluid in the pipe. The heat exchanger is connected to the circuit to exchange heat with the heat transfer fluid in the circuit and also communicates thermally with the building.

[0032] The geothermal installation piping may include a network of injection / reinjection pipes to exchange heat with the subsoil; this is referred to as a geothermal installation on a water table or aquifer.

[0033] The geothermal installation piping may include a closed network of pipes to exchange heat with the subsoil, this is referred to as a geothermal installation on a probe or probe field.

[0034] The piping of the geothermal installation may include a network of spiral pipes to exchange heat with the subsoil, this is referred to as a geothermal installation on compact exchangers.

[0035] Regardless of the geothermal installation, heat is exchanged between the subsoil and the building, or vice versa, by means of a heat transfer fluid circulating in the pipe of the geothermal installation circuit. The fluid can: - to be part of the installation and circulate in a closed loop in the pipeline in so-called closed geothermal installations, such as in the case of geothermal installations on probes or on compact exchangers; or, - to be pumped to pass into the circuit from a water table or an aquifer in so-called open geothermal installations, such as in the case of geothermal installations on a water table.

[0036] The geothermal installation includes intrinsic parameters. Intrinsic parameters are those that can be selected by a geothermal installation installer to configure the geothermal installation as such. Examples of intrinsic parameters include a maximum flow rate of the circulation pump, a maximum heat exchanger capacity, and a pipe length.

[0037] The heat that the geothermal system can exchange with the building to heat / cool it depends directly on several parameters, known as operating parameters. These operating parameters are not intrinsic to the geothermal system itself but depend on how the geothermal system operates. For example, the operating parameters may be: - the real-time flow rate of the fluid in the circuit or a piezometry reading in a well, the well being constructed to connect a pipe of the circuit to a groundwater, in the case of an open-type geothermal installation, or - the flow rate, inlet and outlet temperatures and pressure variation of the fluid that has circulated in the geothermal installation, in the case of a closed-type geothermal installation.

[0038] In so-called open geothermal installations, the fluid temperature is that of the groundwater because the fluid is that of the aquifer. In so-called closed geothermal installations, the fluid temperature is close to that of the subsoil because the circuit communicates with the subsoil via a borehole and exchanges heat by conduction.

[0039] The operating parameters of a geothermal installation can change or be modified over time due to factors external to the geothermal installation, called extrinsic parameters. Examples of extrinsic parameters include: - characteristics of the subsoil: in practice the thickness of the water table, its horizontal and vertical permeability, the storage coefficient, the spatial heterogeneity of these values, the presence of a water table (recharge via upper or lower water tables in hydraulic contact), a recharge zone (river, canal, lake...) or a sealing zone (construction of foundations, tunnels...); - characteristics of the well: quadratic pressure loss at the level of the screens, filter packs, and the immediate environment of the well, the skin effect of the well, the volume effect of the well, important for large diameters ..., clogging; - characteristics of the water table: piezometry, flow gradient, chemical composition, contained solid fraction and biological; - thermal characteristics of the water table: temperature, heat capacity, thermal conductivity; - characteristics of the energy demand profile of the use: heating demand and cooling demand, and especially the annual difference...

[0040] The geothermal installation preferably includes detection means, such as sensors, for acquiring measurements and means for recording the measurements acquired.

[0041] The geothermal installation is preferably controlled by the building to which it is connected. The building advantageously includes a temperature control system which, upon detection of a need for heating or cooling, will request a geothermal installation control unit to manage the flow rate of the circulation pump and thus allow energy transfer via the heat exchanger with a difference temperature AT = T2-T1, where T1 is the temperature of the fluid at the inlet of the exchanger and T2 is the temperature of the fluid at the outlet of the exchanger:

[0042] Eq. 1: P[kW] = 1.16 x AT[°Cou °Æ] xg[^]

[0043] P being the power transmitted by the geothermal installation to the building and Q the flow rate of the fluid in the circuit.

[0044] Open-type geothermal installation

[0045] The geothermal installation may be an open-loop or groundwater geothermal installation. An open-loop geothermal installation generally consists of several boreholes, each with at least one production well and one injection well to draw the heat transfer fluid, i.e., water, at ground temperature, extract or transfer heat, i.e., thermal energy, from it, and reintroduce it into the subsoil or the environment. The production well supplies the geothermal installation with fluid, and the injection well removes the fluid from the geothermal installation.

[0046] Groundwater is pumped by the circulation pump into the production well and circulates through the circuit. This water is then conveyed to the heat exchanger. Advantageously, the geothermal installation includes filters to remove any solid particles present in the fluid, and other equipment such as a bladder, a flow meter, and various temperature and pressure sensors, the latter being installed to monitor pressure drops across the filters, among other things. As it passes through one or more heat exchangers, the water exchanges heat with the building, either directly via low-temperature emitters such as underfloor heating or cooling systems or radiant panels, or via a heat pump to adapt the temperature to the end use. The water is then reinjected into the groundwater via at least one injection well.

[0047] The geothermal installation may include sensors, such as energy meters and water volume meters. Each well is equipped with a piezometer that measures the water level in the well. Piezometric measurements may also be taken in other wells, at a reasonable distance from the boreholes, allowing for an indirect measurement of the groundwater level. The geothermal installation circuit advantageously includes one or more temperature sensors to measure the fluid temperature and the groundwater temperature, in other words, the subsoil temperature.

[0048] Advantageously, the flow rate in the circuit can vary from 5 to 500 m³ / h. The subsoil temperature is close to the average atmospheric temperature of the location, i.e., between 12 and 16°C (urban area) in France. The boreholes advantageously have a depth of between 10 and 200 m, and preferably 50 m. The temperature difference between the production wells and the injection wells is typically 5°C (positive or negative) but can advantageously vary from 0 to 10°C.

[0049] Each well generally consists of a watertight upper casing made of solid stainless steel, steel, or plastic tubing and a lower casing consisting of a screen (a perforated tube allowing water to pass through) placed at the level of the aquifer of interest. Around the screen, a filter bed is placed, which is a cylinder of gravel, marbles, or other small-diameter materials.

[0050] In a geothermal installation, sensors can be used to monitor changes in the static level. This monitoring, explained below, is an important indicator for the management of a geothermal installation.

[0051] It is also possible to estimate the transmissivity between boreholes. Transmissivity is the ease with which the soil allows fluid to pass through. If the transmissivity decreases, the fluid will become increasingly difficult to pump. This is the inverse of the soil's hydraulic resistance. Monitoring transmissivity is therefore important in order to anticipate potential future malfunctions.

[0052] The circulation of groundwater fluid within the circuit can lead to well clogging. This clogging is linked to fouling of the injection well. If the clogging becomes too severe, the geothermal installation will have to be shut down. It is therefore necessary to estimate and predict the remaining time before clogging occurs.

[0053] Management method

[0054] The geothermal installation management process makes it possible to identify in real time one or more causes of an unusual change, in other words, a drift, in an indicator. Once the cause of a drift is identified, the process is configured to manage the geothermal installation and, if necessary, its environment, thereby preventing a malfunction of the geothermal installation. The management process comprises several steps, which are detailed below.

[0055] Measurement of an operating parameter

[0056] The management process, as illustrated for example by [Fig. 1], includes a real-time measurement (step 11), or acquisition, of the evolution of the operating parameters. The measurement is performed independently for each operating parameter. The measurement is carried out at a sampling frequency. Sensors adapted for such acquisitions are implemented in the geothermal installation for this purpose.

[0057] Advantageously, the management process also implements an analysis of the sampling frequency of each operating parameter, in other words, of the sampling quality of each measured operating parameter. Indeed, the analysis makes it possible to modify the sampling frequency of each parameter of operation based on a reliability criterion. The analysis of the sampling frequency is explained below.

[0058] Depending on the needs of the use, the variations of the setpoints in the geothermal installation can be more or less rapid, with characteristic times sometimes very short (less than a minute) in the case of TOR (on or off) regulation or slower (variation in a few hours) if the regulation is proportional or adaptive.

[0059] Thus, the sampling frequency may or may not be suitable for qualitative management and may lead to difficult or even erroneous interpretations of the measured operating parameters. It is therefore important to determine whether the sampling frequency allows for a correct interpretation of the data within a given time interval.

[0060] The method is done by using Discrete Fourier Transforms (DFT) and by setting up a useful oscillating energy indicator.

[0061] After selecting a time interval to analyze, the signal x(t) to be analyzed is retrieved over a duration NTe. The DFT X(n) of the signal is then performed:

[0062] Eq.

[0063] Only the first part of the coefficients (k=0 to N / 2) is useful because of frequency aliasing. Each coefficient e(k) = IX(k)l2 is interpreted as the energy of the signal x at the frequency f(k) = k / (NTe). Thus, e(0) corresponds to the average of the signal, e(l) corresponds to the fundamental frequency related to the duration of the interval, which is not useful here, and e(2) to e(N / 2) correspond to the total oscillatory energy after removing the artifact of the fundamental frequency. The truly useful and interpretable frequencies are generally those less than 10 times the sampling frequency, typically f(k) < fe / 10 (equivalent to k < N / 10), but the coefficient 10 can also be adapted, typically from 2 to 20, as needed.

[0064] Thus the useful oscillatory energy (OUE) is equal to:

[0065] Eq.3:£Or=I^ix(^

[0066] The EOU value corresponds to a reliable criterion measuring the proportion of the useful signal that is correctly sampled: the higher this parameter, the better the sampled signal and the easier it is to interpret. In other words, if the EOU value is greater than a predetermined threshold, the sampling frequency of the values ​​of the operating parameter in question is considered acceptable.

[0067] The determination of the threshold for the EOU can be carried out as follows: - for a given time interval or time window size, the value of EOU is determined for all windows, - Using a distribution function of EOU values, we can identify windows where the EOU is among the top 50% of values. Typically, we will use values ​​between 20% and 80% as a threshold. (The distribution function is a function that, given an EOU value, gives the percentage of values ​​below the EOU).

[0068] Other methods can be used depending on the probability density of the EOU values: - if the probability density of the EOU is close to a Gaussian (1 peak), then the method described previously is certainly the most suitable; - If the probability density of the EOU is binomial (2 peaks), then Bayesian thresholding is appropriate

[0069] Furthermore, the EOU values ​​below a predetermined significance threshold, linked to the measuring equipment used, will be removed beforehand. If the measuring device has a measurement accuracy characterized by a measurement standard deviation, the threshold will be (me)2 with m between 1 and 10, typically 5.

[0070] Other methods can also be used such as the windowed Fourier transform or a thresholding on the amplitude (difference between the max and min value) determined over a time window.

[0071] Estimating the quality of sampling thus makes it possible to improve the analysis of drifts through correct acquisition of the evolution of operating parameters.

[0072] Estimation of an indicator

[0073] The management process then includes an estimation step (E2) of one or more indicators. Each indicator is representative of a real-time evolution of one of the extrinsic parameters of the geothermal installation.

[0074] The estimation is performed in real time. The estimation can be a function of one or more operating parameters as well as extrinsic parameters of the geothermal installation.

[0075] For example, it is possible to estimate a static level of a groundwater aquifer to which the geothermal installation is connected by taking into account the piezometric level in the installation's wells and a theoretical static level, as explained below. Another possibility is, for example, to estimate the transmissivity between the wells of the geothermal installation by taking into account the flow rate in the installation circuit and a theoretical transmissivity, as also explained below. Another possibility is, for example, to estimate a representative indicator of clogging of the geothermal installation by taking into account the volume of fluid that has flowed out in the geothermal installation as well as a previously recorded theoretical fluid flow rate etc...

[0076] Estimation of the static level

[0077] In the case of an open geothermal installation (or on aquifers) the indicator corresponding to the static level of the water table is estimated in order to allow management of the geothermal installation, to detect an anomaly and to identify one or more external causes of the anomaly detected.

[0078] The static level is therefore an extrinsic parameter of the geothermal installation, the indicator of which can be estimated based on one or more of the geothermal installation's operating parameters. To estimate the static level indicator in real time, it is possible to consider, as operating parameters, the piezometry in the circuit of the open-type geothermal installation, as well as the previously recorded theoretical static level, as an extrinsic parameter.

[0079] The water level, or piezometric level, in a well varies according to numerous phenomena with time constants that vary depending on the case, typically: • Pumping or injecting water causes the water level to fall and rise respectively: the time constant is linked to the flow demands of the geothermal system • Natural variations in the water table: these are essentially cyclical, with an annual period. • Anthropogenic variations of the water table linked to external pumping of the geothermal installation: the time constants are very variable here but are understood a priori between the variations of the pumping and the natural variations.

[0080] Changes in the piezometric level influence the static groundwater level. To implement the prediction of water level changes, one possible solution is to: - Determine a time window, typically between 1 and 30 days. - Record, in the time window, piezometry values ​​when the pumping or injection flow rate is zero or less than the measurement noise (< 5 standard deviations of the measuring equipment typically); - Determine a minimum piezometric level (for the injection well) and / or a maximum piezometric level (for the pumping well): these values ​​will be candidate values ​​of the static level NS; and NSp which will be selected in the next step; - Calculation of the indicator value. The indicator is a value, but may optionally be a range of values.

[0081] This value is the estimate of the static groundwater level for the NS injection well; or NSP production well; and - Real-time comparison between these NS and NSP values ​​of static levels:

[0082] If \NSfiJ) -NSp(t) | is less than a first SI threshold, the estimate is considered reliable,

[0083] If \NSfit) -NSp(t ) | is greater than the first SI threshold, three cases may arise: a. Both estimates are false: \NSp(t) -NSp(t+z) | >S2xzet | NSi (t) - NS; ( t + z ) | >S2x z with z > 0 the smallest time such that NSP (t + z) and NS fit+z) exist, b. The estimate at the injection well is incorrect, while the estimate at the production well is correct: this will be detected if pVSp(f) -NSp(t + z) | < pVSj(0 -NSfit + z) | with z > 0 the smallest time such that jVSp(f + z) and NSfit + z) exist, c. The estimate at the production well is incorrect, while the estimate at the injection well is correct: this will be detected if lïVSjdÇ -NSfit + z) | < \NSp(t) -NSp(t + z) | with z > 0 the smallest time such that NSp(t + z) and NSfit + z) exist.

[0084] The SI and S2 thresholds are interpreted as follows: • SI is the permissible static measurement error between the two wells, which may be associated with an error in determining the altitude zero, underground flow...; it can be determined as follows: • Method 1: SI - m+ fi <7 with m the absolute value of the time mean of NS fit) -NSp(t) and the time standard deviation of NS fit) -NSp(t). P is chosen between 0 and 10, typically 2. • S2 is the maximum variation in meters per unit of time of the static level beyond which it cannot be a real cause but a measurement error: a threshold of Im / d could be chosen for example, but the values ​​of 0.1 and 10 m / d may be relevant.

[0085] Taking into account the impact of an external parameter on piezometry makes it possible to obtain a prediction of the evolution of the static level for the external parameter considered...

[0086] Estimation of the transmissivities of the producing and injecting wells and

[0087] Transmissivity is the ease with which the soil allows water to pass through it: if transmissivity decreases, pumping is less efficient and the efficiency of the geothermal system is reduced. Transmissivity is therefore the inverse of the soil's hydraulic resistance.

[0088] Transmissivity is therefore an extrinsic parameter of the geothermal installation, the indicator of which can be estimated based on one or more of the geothermal installation's operating parameters. Estimating the transmissivity indicator allows for improved management of the geothermal installation.

[0089] In order to estimate in real time the indicator of the actual transmissivity it is possible to take into account, as operating parameters, the fluid flow rate in the circuit of the open type geothermal installation as well as the theoretical transmissivity previously recorded. Variables description Pir Pizometer n°i, actual value P^ Pizometer n°i, value measured by the sensor P^ Pizometer n°i, value recorded in memory T if Temperature n°i, actual value Temperature n°i, value recorded in memory Q Flow rate n°i, actual value Q ^un Flow rate n°i, value measured by the sensor

[0090] For the pumping well: [00911 ^4:QRtiW=_sS_ca2_^_w^ ^:^(,)^¾]

[0093] For the injection well:

[0094] Eq. 6:

[0095]

[0096] With: - Sj > 0 skin effect and linear clogging, - Ci > 0, the quadratic pressure loss coefficient also related to clogging, - Tj the transmissivity of the aquifer near well no. i, - S is the storage coefficient, - t the time, - rîJ the distance such that if i = j, it is the radius of well no. i, if i * j, the distance between wells i and j, and - W, a typical function of the sheet structure.

[0097] The function W(u) is classically calculated according to the assumptions of Theis, Jacobs, or Hantush, for example, depending on whether the medium is homogeneous and isotropic, homogeneous and isotropic over long periods, or homogeneous and isotropic with a wall. Other models exist that simulate the presence of a recharge or a sealed wall, whether the aquifer is confined or free, etc.

[0098] The method may optionally include a digital filtering step using a first-order low-pass filter F, or several to improve the robustness of the method.

[0099] In summary, the estimation of the indicator representing the transmissivity of producing and injecting wells includes: - the prediction of the piezometric head of a well in the geothermal installation based on the measured fluid flow rate and transmissivity,

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107] - a comparison between the estimated piezometric head and a piezometric measurement of an injection well or a piezometric measurement of a production well, - a minimization of a difference resulting from the comparison, the difference implementing a modification of the parameters of a model for the prediction. This allows for real-time estimation of the transmissivity indicator of the geothermal installation. Estimated time remaining before the circuit becomes clogged The clogging of the circuit is due to the presence of particles in the reinjected water. As a result, a layer of material (a "cake") forms on the strainer, thus increasing the hydraulic resistance of the structure. This clogging (or "fouling" or "clogging" in English) can be classified as reversible (the "cake," once removed, restores the initial resistance) or irreversible (even after washing and treatment, additional resistance remains). In order to estimate the circuit clogging indicator in real time, it is possible to take into account ... (operating parameter) of the geothermal installation as well as ... (extrinsic parameter such as the purity of the aquifer...). Let Kg be the permeability of the cake, S the surface area of ​​the strainer, Cg the mass concentration of comatose particles in the water, dg their mass density in cake form, and Qsp(0) the initial specific flow rate. Furthermore: ^S'V(t)=(p[u)ilu is the total volume that has flowed into the well. Finally, we have: Eq. 9: iiz, , 7 \ a» ' '

[0108]

[0109]

[0110] With KgdgS By definition, We can easily set a maximum threshold at Q (or a minimum at Qsp), beyond which from which the installation must be stopped. Indeed, we know, from the dimensions of the well, the maximum possible drop in piezometric level to avoid depleting the water table or flooding the upper parts of the facilities (parking, garden, basement...). Let Q?™ be this value equal to the required flow rate divided by the maximum piezometric variation in the well.

[0111] We therefore have a linear relationship between the volume injected into the well and the inverse of the specific flow rate, which has the dimensions of a resistance. Thus, by regularly measuring μQ using the methods described above, we can predict, by linear interpolation, the volume that will cause a failure in the installation; knowing the water consumption of the installation, we can deduce a predicted date of sudden shutdown of the installation.

[0112] This method will also allow us to estimate the effectiveness of unclogging because unclogging will lower the value of ijQ by removing the filtration cake.

[0113] In summary, the estimation of the indicator representing clogging includes: - an estimate of a future specific flow rate based on the volume of fluid flowing and the theoretical fluid flow rate, as well as the characteristics specific to the fluid circulating in the geothermal installation, and - a calculation of a fluid volume before shutdown based on the estimated specific flow rate.

[0114] It is possible to simplify the knowledge model to a single parameter. To do this, we assume that the transmissivities are identical on each well (Tl = T2 = T) and by setting ~rn = r22 the radius of the wells and d = rn = r2i the distance between wells, we arrive at the following simplifications:

[0115] For the pumping well we have:

[0116] Eq. 10 : Pu - ECpP^ +

[0117] With: _ _s _). In the case of long times, the Jacobs approximation is valid (yy(u) ~ -0.577 - ln(u)) for confined, homogeneous, and isotropic aquifers with a perfect well. Furthermore, S is the storage coefficient, r the well radius, and T the transmissivity. Quadratic head losses (c=0) are also neglected.

[0118] And for the injection well:

[0119] Eq. 11 : = ECpP, + «2

[0120] With: _ +j

[0121] Thus, the knowledge model is reduced to a parameter a for each well; 1 / is interpreted as the specific flow rate of the installation. If the initial transmissivity of the aquifer is known, which can also be estimated using the minimum absolute value of a\ 011 a2 with the following relation:

[0122] Eq. 12 : ~ ln«) init ~ 2?r

[0123] We are able to estimate the linear clogging of each well:

[0124] Eq. 13: = = K|- min^

[0125] Eq. 14: _ a _ .^..A.....|n (^) - I _ min\a2\ ~ imt 1 - ' i XJ

[0126] st has the unit [s / m2] and is homogeneous to a hydraulic resistance. This characterizes the resistivity related to clogging. A clogging indicator can be constructed which is equal to 0 when clogging is negligible and 1 when the total apparent hydraulic resistance is associated with clogging:

[0127] Eq. 15: . , . . H»1'*,] Clogging index 1 = ---—

[0128] A clogging index can also be defined which represents the logarithmic ratio between the apparent resistance of the well and the initial resistance:

[0129] Eq. 16: Clogging index 2 = = log-j-^

[0130] It is equal to 0 when there is no clogging, 1 when the apparent resistance is 10 times greater than the initial resistance, 2 for 100 times greater.

[0131] Determination of boundary conditions

[0132] The management process further includes a determination (E3) of boundary conditions. Indeed, for each estimated indicator, it is necessary to be able to determine whether the indicator's values ​​and their evolution are the result of normal and usual use of the geothermal installation, or whether the geothermal installation is malfunctioning, or whether external causes, extrinsic to the installation, are present.

[0133] To determine limit conditions, in other words thresholds or alert values, it is necessary to take into account the extrinsic parameter linked to the indicator considered as well as forecasts made previously and linked to assumptions of usual operation.

[0134] For example, to determine the boundary conditions of the indicator linked to the static level, it is possible to search in the piezometric records of the water table, or in the Explore2070 simulation work, for the typical natural variation of the

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] The water table typically ranges between 1 and 10 meters, depending on the circumstances. It is possible to calculate the piezometric variation for each period, typically from one week to the next, or from one month to the next, and compare it to this threshold. For example, let b be the natural fluctuation of the water table over one year. We construct the following indicator: Eq. 17: .. , .. , Groundwater variation index 1 = — 365 With Ans representing the variation of the static level over the time interval At in days. If this indicator is less than 1, the water table variation is natural; if it is greater than 1, and especially in cases where it is much greater than 1, an anthropogenic influence on the piezometric variation of the water table can be assumed. Installation control As mentioned previously, the management process then includes a step to identify any potential malfunction of the installation. This identification is achieved by comparing the estimated value of the indicator in question to a number of boundary conditions. These boundary conditions are based on different assumptions. The assumptions relate to one or more parameters extrinsic to the geothermal installation. As mentioned previously, the management process then includes a selection step, based on the comparison results, to identify one or more hypotheses in order to characterize the external cause of the anomaly. This selection is made using measurements of one or more indicators and the boundary conditions defined for each indicator. The selected hypothesis is the identified cause of the anomaly. Identifying the anomaly therefore allows us to select (step E5) the cause(s) of the anomaly. The determined cause is associated with one of the extrinsic parameters or with a malfunction of the installation: • cause associated with an extrinsic parameter: anthropogenic or natural modification of the water table, modification of the hydrogeological characteristics of the subsoil linked to new human constructions, increase in the temperature of the water table by anthropogenic or natural effect... • System malfunction: clogging, imbalance in heating and cooling demands... Advantageously, the process also includes a step for implementing a corrective action (E6) for the geothermal installation. This management step prevents any malfunctions in the installation. The management influences the parameters of operation and / or on the external causes identified in order to resolve the anomaly detected in the evolution of one of the indicators linked to an extrinsic parameter.

[0144] Thus the process makes it possible to remedy the malfunctions which are related to the operating parameters of the installation as well as to external causes modifying the extrinsic parameters.

Claims

Demands

1. Method for managing a geothermal installation, the geothermal installation being configured to meet the heat or cooling demands of at least one building or industrial or agricultural process, the method comprising: - a measurement (E1), at a certain sampling frequency, of hydraulic, thermal and / or chemical operating parameters of the installation, by at least one measuring device; - a dated estimate (E2) of an indicator as a function of at least one of the measured operating parameters, the indicator being representative of an evolution of an extrinsic parameter of the geothermal installation;and - a comparison (E4) of the indicator estimate to a plurality of boundary conditions, said boundary conditions being a function of different assumptions relating to parameters extrinsic to the geothermal installation, and - a selection (E5), based on the result of the comparison, of at least one of these assumptions, in order to characterize the external cause of a possible malfunction of the installation.

2. Method according to claim 1, comprising an implementation of a corrective action (E6) on the installation according to the detected malfunction and the selected hypothesis.

3. A method according to any one of claims 1 and 2, wherein the reliability of the measurements of the operating parameters is tested in real time (El 1) and the sampling frequency of these measurements is adapted according to the test results.

4. A method according to claim 3, wherein the real-time reliability test of the operating parameter measurements implements the following processing: - discrete Fourier transform of the measurements of said operating parameter considered over a predetermined time interval, - calculation of a useful oscillating energy as a function of the Fourier transform of said operating parameter, - determination of the sampling frequency as a function of this oscillating energy.

5. A method according to any one of claims 1 to 4, wherein an estimated indicator is a representative indicator of a static fluid level in the subsoil, the estimation of said indicator being a function of a piezometric measurement in the geothermal installation as well as a previously determined theoretical static level.

6. A method according to claim 5, wherein the geothermal installation comprises at least one injection well and at least one production well and wherein the estimation (E2) of the indicator representing a static level implements: - a piezometric measurement of the level of the injection well and a piezometric measurement of the level of the production well; - a comparison between the two measurements, and wherein the indicator is an interval which includes the interval between the piezometric measurement of the injection well and the piezometric measurement of the production well, if the difference between the two measurements is less than a first predetermined threshold.

7. A method according to any one of claims 1 to 4, wherein the geothermal installation comprises at least one injection well and at least one production well and an estimated indicator is a representative indicator of a transmissivity between the production well and the injection well and the estimate of the indicator being a function of a flow rate of a fluid in the geothermal installation as well as a previously recorded theoretical transmissivity.

8. A method according to claim 7, wherein the estimation (E2) of the representative transmissivity indicator comprises: - a prediction of the piezometry of the production well level and / or the injection well as a function of the measured fluid flow rate and transmissivity, - a comparison between the piezometry resulting from the forecast and a piezometric measurement of the injection well or a piezometric measurement of the production well, - a minimization of a difference resulting from the comparison.

9. A method according to any one of claims 1 to 4, wherein an estimated indicator is a representative indicator of clogging of the geothermal installation and is estimated as a function of a volume of fluid flowing into the geothermal installation as well as a theoretical fluid flow rate previously recorded.

10. A method according to claim 9, wherein the estimation (E2) of the indicator representing the clogging comprises: - an estimation of a future specific flow rate as a function of the volume of fluid flowed and the theoretical fluid flow rate as well as the characteristics specific to the fluid circulating in the geothermal installation, and - a calculation of a volume of fluid before shutdown as a function of the estimated specific flow rate.

11. A method according to any one of claims 1 to 10, wherein the operating parameter is included in the following parameters: a heat transfer fluid flow rate in the geothermal installation, a fluid pressure in a pipe of the geothermal installation, a volume of fluid that has circulated in the geothermal installation.

12. A method according to any one of claims 1 to 4, wherein the estimated indicator is included in the following list: a static fluid level in the subsoil, a transmissivity between a production well and an injection well, an effective or apparent thermal conductivity of the soil, or a soil heat capacity.

13. A method according to any one of claims 1 to 12, wherein the extrinsic parameters of the geothermal installation represented by an indicator are included in the following parameters: soil permeability, the presence of biochemical elements, operating parameters of neighboring geothermal installations, the environment of the geothermal installation, pipe clogging, and an evolution meteorological factors, energy consumption or energy losses of the structure.

14. A method according to any one of claims 1 to 13, wherein the geothermal installation is a groundwater geothermal installation.

15. A method according to any one of claims 1 to 5 and 9 to 11, wherein the geothermal installation is an open-type installation, or a probe-type geothermal installation, or a closed-type installation, or a compact exchanger-type geothermal installation.

16. Assembly comprising a geothermal installation configured to meet the heat or cooling demands of at least one building or industrial or agricultural process and a geothermal installation management system, the system comprising means for measuring the operating parameters of the geothermal installation and being suitable for implementing the process according to any one of claims 1 to 15.

Images