An intelligent scale removal system for geothermal wellbore

Abstract

The present application relates to a kind of geothermal wellbore scale intelligent scale removal system, including wellhead monitoring module, downhole monitoring module, main control system, injection module;Main control system includes the analysis module, dosing scheme generation module, control module connected in sequence;Injection module includes the lifting unit connected, injection unit;Analysis module, for according to the wellhead geothermal fluid data, downhole geothermal fluid data and multiple-field multiphase multi-component non-isothermal phase transition flow model obtained by real-time monitoring, inversion obtains the real-time flashing face depth of geothermal fluid in wellbore, and the real-time scale rate of different depth positions;Dosing scheme generation module, according to the real-time flashing face depth, the real-time scale rate of different depth positions, real-time generates corresponding scale inhibitor dosing scheme, scale inhibitor dosing scheme includes scale inhibitor injection rate, scale inhibitor injection depth;Control module, for according to real-time scale inhibitor dosing scheme to lifting unit, injection unit is controlled.The present application can realize intelligent scale removal.

Description

A smart descaling system for geothermal wells Technical Field

[0001] This invention belongs to the field of geothermal fluid scale inhibition and removal technology, specifically relating to an intelligent scale removal system for geothermal wells. Background Technology

[0002] Scale formation is currently one of the major problems faced in the development and utilization of geothermal resources, especially in the extraction of medium- and deep geothermal energy. Deep geothermal fluids are transported to the surface through wellbores. Due to the decrease in temperature and pressure, some substances become supersaturated and precipitate, depositing on the inner wall of the wellbore, forming scale. Scale formation in the wellbore increases fluid flow resistance, affecting the efficiency of geothermal energy utilization, and in severe cases, may lead to the shutdown of the geothermal well. To ensure stable efficiency in geothermal extraction, it is necessary to assess the scale formation situation in the wellbore and take timely countermeasures.

[0003] Currently, commonly used geothermal wellbore scaling monitoring technologies include the plate method, probe method, electrochemical method, potential monitoring method, ultrasonic method, infrared imaging method, and eddy current method. These technologies assess the scaling status of the wellbore by monitoring changes in the physicochemical properties of the plate, probe, wellbore, and geothermal fluid caused by scale, such as plate mass, probe resistance and thermal resistance, wellbore wall thickness and morphology, and geothermal fluid flow rate, potential, and temperature difference. However, a certain amount of scale accumulation is required for noticeable changes to be detected, which can lead to delayed warnings. By the time scaling is detected, the scaling condition is already quite significant, greatly increasing the difficulty and cost of descaling. On the other hand, chemical scale inhibition technology, which involves adding scale inhibitors to the geothermal fluid (called chemical dosing), has the advantages of controllable cost, obvious effect, and no need to shut down wellbore production. It is a commonly used method for scale prevention and inhibition in geothermal development. However, current chemical dosing scale inhibition systems used in engineering applications lack sufficient intelligence. They require manual control based on pre-designed dosing plans and lack feedback and adjustment during the dosing process, which may result in unsatisfactory scale inhibition effects. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides an intelligent descaling system and method for geothermal wells, which can predict the scaling trend of the wellbore in real time based on real-time monitored geothermal fluid data, automatically generate a dosing plan, and intelligently control the operation of the dosing scale inhibition system.

[0005] The present invention adopts the following technical solution:

[0006] A smart descaling system for geothermal wells includes a wellhead monitoring module, a downhole monitoring module, a main control system, and an injection module; the main control system includes an analysis module, a dosing scheme generation module, and a control module connected in sequence; the injection module includes a connected lifting unit and an injection unit.

[0007] The wellhead monitoring module and the downhole monitoring module are connected to the analysis module, and the control module is also connected to the lifting unit and the injection unit.

[0008] Wellhead monitoring module, used for real-time monitoring of geothermal fluid data at the wellhead;

[0009] The downhole monitoring module is used to monitor downhole geothermal fluid data in real time.

[0010] The analysis module is used to invert the real-time flash surface depth of the geothermal fluid in the wellbore and the real-time scaling rate at different depths based on the real-time monitoring data of the geothermal fluid at the wellhead, the downhole geothermal fluid, and the multi-field multiphase multicomponent non-isothermal phase change flow model.

[0011] The dosing scheme generation module generates corresponding scale inhibitor dosing schemes in real time based on the real-time flash surface depth and the real-time scaling rate at different depth locations. The scale inhibitor dosing scheme includes the scale inhibitor injection rate and the scale inhibitor injection depth.

[0012] The control module is used to control the lifting unit to move up and down according to the scale inhibitor injection depth in the real-time generated scale inhibitor dosing plan, so that the injection unit reaches the corresponding depth position in the geothermal well.

[0013] The control module is also used to control the injection unit to inject scale inhibitor according to the scale inhibitor injection rate in the real-time generated scale inhibitor dosing plan.

[0014] As a preferred embodiment, the system also includes an early warning module, which is connected to the downhole monitoring module and the analysis module respectively;

[0015] The early warning module calculates the scale precipitation saturation index based on the preset scale precipitation threshold and the real-time calculated well fluid thermodynamic balance constant, and determines whether to issue an early warning based on the scale precipitation saturation index.

[0016] The analysis module performs data inversion only after the early warning module issues an early warning.

[0017] As a preferred option, the formula for calculating the thermodynamic equilibrium constant of the well fluid is:

[0018]

[0019] Where a, b, c, d, and e are fitting parameters, each obtained based on the relationship curve between mineral solubility and temperature; T represents the downhole geothermal fluid temperature obtained from real-time monitoring.

[0020] As a preferred option, the scale precipitation threshold is specifically defined as the fluid state threshold at which mineral-containing water reaches saturation and scale precipitates.

[0021] As a preferred option, the scale precipitation saturation index is the ratio of the wellbore fluid thermodynamic equilibrium constant to the scale precipitation threshold.

[0022] The early warning module is used to issue an early warning when the scale precipitation saturation index exceeds a preset threshold.

[0023] As a preferred option, the wellhead monitoring module is used to monitor the wellhead geothermal fluid flow rate, wellhead geothermal fluid pH value, wellhead geothermal fluid concentration of various metal cations, and wellhead geothermal fluid carbon dioxide concentration data in real time.

[0024] The downhole monitoring module is used to monitor the temperature and pressure of the downhole geothermal fluid in real time.

[0025] As a preferred option, the dosing scheme generation module generates a corresponding scale inhibitor dosing scheme in real time based on the real-time flash surface depth, the real-time scaling rate at different depths, and the scale inhibition rate data of the scale inhibitor.

[0026] As a preferred option, the scale inhibition rate data of the scale inhibitor includes scale inhibition rate data for different scale inhibitor ratios;

[0027] The scale inhibitor dosing plan generated in real time by the dosing plan generation module also includes the scale inhibitor ratio;

[0028] The injection module also includes a scale inhibitor preparation unit connected to the injection unit;

[0029] The control module is also used to control the scale inhibitor preparation unit to prepare the scale inhibitor according to the scale inhibitor ratio in the real-time generated scale inhibitor dosing plan.

[0030] As a preferred embodiment, the scale inhibitor preparation unit includes a scale inhibitor stock solution storage tank, a deionized water storage tank, and a scale inhibitor preparation tank. The scale inhibitor stock solution storage tank and the deionized water storage tank are respectively connected to the scale inhibitor preparation tank via pipelines. The scale inhibitor preparation tank has a built-in stirrer. Solenoid valves are installed at the pipeline connections between the scale inhibitor stock solution storage tank, the deionized water storage tank, and the scale inhibitor preparation tank.

[0031] The control module controls the opening and closing of the solenoid valve according to the scale inhibitor ratio in the real-time generated scale inhibitor dosing plan, so that deionized water and scale inhibitor stock solution enter the scale inhibitor preparation tank, and controls the agitator to stir to complete the preparation of the scale inhibitor with the corresponding ratio.

[0032] As a preferred embodiment, the injection unit includes an injection tube and a heat tracing device surrounding the outer surface of the injection tube.

[0033] The beneficial effects of this invention are:

[0034] This invention generates a corresponding scale inhibitor dosing plan in real time based on the real-time flash evaporation surface depth of the geothermal fluid in the wellbore obtained through real-time inversion and the real-time scaling rate at different depth locations. The scale inhibitor dosing plan includes the scale inhibitor injection rate and injection depth. A control module controls a lifting unit to ensure the injection unit reaches the corresponding depth within the geothermal wellbore. The control module further controls the injection unit to inject the scale inhibitor according to the injection rate in the real-time generated dosing plan, requiring no human intervention and providing fully intelligent control. Furthermore, this invention sets the scale inhibitor injection rate and depth based on the real-time flash evaporation surface depth and the real-time scaling rate at different depth locations, resulting in better scale inhibition and saving on scale inhibitor usage.

[0035] The present invention also introduces a scale precipitation saturation index for early warning, and data inversion is only performed after the early warning, that is, after the scale precipitation saturation index exceeds a preset threshold, to avoid the system from performing complex calculations continuously.

[0036] Because different scale inhibitors have different scale inhibition effects, this invention can also generate corresponding scale inhibitor dosing schemes in real time based on real-time flash surface depth, real-time scaling rate at different depths, and scale inhibition rate data of the scale inhibitor. This allows the system to be compatible with a variety of scale inhibitors.

[0037] Because different scale inhibitor ratios have different scale inhibition effects, the scale inhibition rate data of this invention may also include scale inhibition rate data for different scale inhibitor ratios. Furthermore, the scale inhibitor dosing scheme generated in real time by the dosing scheme generation module also includes the scale inhibitor ratio. The injection module also includes a scale inhibitor configuration unit connected to the injection unit. The scale inhibitor configuration unit is used to configure a scale inhibitor with a corresponding ratio based on the scale inhibitor ratio in the real-time generated scale inhibitor dosing scheme. This allows for the configuration of a scale inhibitor with a corresponding ratio according to real-time conditions, thereby meeting real-time scale inhibition requirements.

[0038] The invention also includes a heat tracing device surrounding the outer surface of the injection pipe to ensure the flowability of the scale inhibitor in low-temperature weather. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 is a schematic diagram of the structure of an intelligent descaling system for geothermal wells according to the present invention. Detailed Implementation

[0041] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0042] Example 1:

[0043] Referring to Figure 1, this embodiment provides an intelligent descaling system for geothermal wells, including a wellhead monitoring module, a downhole monitoring module, a main control system, and an injection module; the main control system includes an analysis module, a dosing scheme generation module, and a control module connected in sequence; the injection module includes a lifting unit and an injection unit connected in sequence.

[0044] The wellhead monitoring module and the downhole monitoring module are connected to the analysis module, and the control module is also connected to the lifting unit and the injection unit.

[0045] Wellhead monitoring module, used for real-time monitoring of geothermal fluid data at the wellhead;

[0046] The downhole monitoring module is used to monitor downhole geothermal fluid data in real time.

[0047] The analysis module is used to invert the real-time flash surface depth of the geothermal fluid in the wellbore and the real-time scaling rate at different depths based on the real-time monitoring data of the geothermal fluid at the wellhead, the downhole geothermal fluid, and the multi-field multiphase multicomponent non-isothermal phase change flow model.

[0048] The dosing scheme generation module generates corresponding scale inhibitor dosing schemes in real time based on the real-time flash surface depth and the real-time scaling rate at different depth locations. The scale inhibitor dosing scheme includes the scale inhibitor injection rate and the scale inhibitor injection depth.

[0049] The control module is used to control the lifting unit to move up and down according to the scale inhibitor injection depth in the real-time generated scale inhibitor dosing plan, so that the injection unit reaches the corresponding depth position in the geothermal well.

[0050] The control module is also used to control the injection unit to inject scale inhibitor according to the scale inhibitor injection rate in the real-time generated scale inhibitor dosing plan.

[0051] This embodiment designs an intelligent descaling system for geothermal wells. Based on monitoring data, the main control system can predict the scaling trend of the wellbore in real time, thus providing early warning of scaling. It also automatically generates a scale inhibitor dosing plan, intelligently controls the operation of the injection module, and adjusts the dosing plan based on monitoring data. This system significantly reduces manual intervention in design and on-site operation, essentially achieving unattended operation and improving the overall intelligence and automation level of the geothermal system.

[0052] The main control system can also transmit the data it monitors and the solutions it generates to the cloud monitoring platform in real time via wireless transmission equipment for remote monitoring.

[0053] The aforementioned wireless transmission device is a 5G-based wireless IoT gateway that connects to the main control system via LAN, transmits data based on the TCP / IP protocol, and then converts it into a 5G wireless signal to communicate with the cloud monitoring platform.

[0054] The aforementioned control module is a programmable logic controller (PLC). It converts the dosing plan generated by the dosing plan generation module into executable instructions through a preset program and transmits them to the corresponding equipment in the injection module to realize the automated implementation of the dosing plan.

[0055] It should be noted that the analysis module described in this embodiment is based on an analysis and inversion principle described in two published papers, namely:

[0056] [1] Lei Hongwu, Bai Bing, Cui Yinxiang, et al. Quantitative evaluation of calcium carbonate scaling in high-temperature geothermal production wells: two-phase flow—a case study of Yangbajing in Tibet [J / OL]. Earth Science.

[0057] [2] Lei Hongwu, Bai Bing, Cui Yinxiang, et al. Quantitative evaluation of calcium carbonate scaling in high-temperature geothermal production wells: hydrogeochemistry—a case study of Yangbajing in Tibet [J / OL]. Earth Science.

[0058] Based on the calculation model described in the paper, the real-time flash depth of geothermal fluid in the wellbore and the real-time scaling rate at different depths can be obtained by inverting the corresponding real-time detected data.

[0059] Regarding the multi-field, multiphase, multi-component, non-isothermal phase change flow model used in data inversion:

[0060] This model is quite complex, involving numerous formulas, including the overall mass conservation formula for multiphase fluids, the mass conservation formula for CO2, the momentum conservation formula, the energy conservation formula, the enthalpy formulas for liquid and gas phase mixtures respectively, the drift flow formula for gas phase volume fraction, the chemical composition equilibrium formula for multiphase fluids (including chemical reaction equations involving calcium ions, carbonate ions, hydroxide ions, bicarbonate ions, water molecules, CO2 molecules, etc.), the wellbore adhesion flux formula for calcium scale, and the fluid chemical component transport formula, etc. The model requires input data including formation logging data (mainly geothermal field and heat transfer coefficient of surrounding rock, electrical conductivity of geothermal fluids), and scale inhibition rate data of scale inhibitors at different temperatures and pressures (obtained through laboratory tests in a high-temperature, high-pressure reactor). Then, using real-time geothermal fluid data collected at the wellhead (including temperature, pressure, flow rate, pH, hardness, and CO2 concentration) and real-time downhole temperature and pressure, the model calculates the flash surface depth of the geothermal fluid in the wellbore and the scaling rate at different depths.

[0061] Specifically: the wellhead monitoring module is used to monitor in real time data such as the flow rate of the geothermal fluid at the wellhead, the pH value of the geothermal fluid at the wellhead, the concentration of various metal cations in the geothermal fluid at the wellhead, and the carbon dioxide concentration of the geothermal fluid at the wellhead; the downhole monitoring module is used to monitor the temperature and pressure of the downhole geothermal fluid in real time.

[0062] The inversion process is described in detail in the two papers mentioned above. However, this inversion process is not the focus of this embodiment. The focus of this embodiment is on how to intelligently inject scale inhibitors into the geothermal wellbore based on the flash surface depth of the geothermal fluid in the wellbore and the scaling rate at different depths obtained from the inversion.

[0063] As can be seen from the above, the multi-field, multi-phase, and multi-component non-isothermal phase change flow model is quite complex and is not the focus of this embodiment. Therefore, the following is a simple description of the multi-field, multi-phase, and multi-component non-isothermal phase change flow model:

[0064] A multi-field, multi-phase, multi-component non-isothermal phase change flow model is proposed. The conservation equations for the one-dimensional phase change flow model in a wellbore are as follows:

[0065]

[0066]

[0067]

[0068]

[0069] Where: ρ l and ρ g The densities of the liquid and gas phases, u, are respectively. l and u g Here, represents the flow rates of the liquid phase and the gas phase, respectively, and α is the volume fraction of the gas phase. and These are the mass fractions of the liquid phase and the gas phase, respectively. The total mass velocity is a known quantity; γ is the mass fraction of CO2, also a known quantity; P = P H2O +P CO2 For the total pressure, P H2O and P CO2 ρ represents the partial pressure of H2O and CO2, respectively; z is the wellbore elevation, d is the wellbore diameter; g is the acceleration due to gravity, f is the coefficient of friction of the well wall; ρ m For the mixed density, ρ m =(1-α)ρ l +αρ g ;u m The average velocity of the mixture, h l and h g The enthalpy of liquid phase and gas phase, respectively, h m =(1-x)h l +xh g Let y be the enthalpy of the mixture, x be the mass fraction of the gas phase, and q be the heat exchange per unit length between the wellbore and the surrounding rock, q = U(T). f -T wb U represents the centralized heat exchange parameter, which generally needs to be corrected using actual data. T f and T wb These are the temperatures of the fluid in the wellbore and the temperature of the well wall, respectively.

[0070] enthalpy h of liquid mixture l for:

[0071]

[0072] in: and Let h be the internal energy and density of liquid H2O at pressure P and temperature T, respectively; CO2 For voltage divider P CO2 The enthalpy of CO2 at temperature T; h SOL The heat released when CO2 dissolves in water. The enthalpy h of the gas-phase mixture. g for:

[0073]

[0074] in: and The pressures P are respectively H2O The internal energy and density of gaseous H2O at temperature T.

[0075] The gas phase volume fraction α is expressed as:

[0076]

[0077] Where C0 is the distribution parameter; u d denoted as ρ, where ρ is the gas phase drift velocity; A is the cross-sectional area inside the wellbore (excluding scale buildup).

[0078] According to the drift flow model, C0 and u d The value can be:

[0079]

[0080]

[0081] in: σ represents the interfacial tension between the gas and liquid. The parameter K is a function of the gas phase volume fraction α, that is:

[0082]

[0083] A, a1, and a2 are all empirical parameters. It is recommended to take A = 1.2, a1 = 0.06, and a2 = 0.12.

[0084] The chemical reactions that occur during the calcium carbonate scaling process in wellbore include:

[0085]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092]

[0093]

[0094] The thermodynamic equilibrium constant K of the wellbore fluid can be expressed as:

[0095]

[0096] Where T is the absolute temperature, and a, b, c, d, and e are fitting parameters obtained from indoor scale inhibition tests.

[0097] The general kinetic reaction rate r of mineral dissolution and precipitation reaction n n It can be expressed by the following formula:

[0098]

[0099] In the formula, r n Positive values ​​represent dissolution, negative values ​​represent precipitation, k is the reaction rate constant, and A n Ω represents the specific surface area of ​​the reaction, θ and η are experimental fitting parameters, and Ω is the specific surface area of ​​the reaction. n This represents the kinetic mineral saturation. The reaction rate constant k can be expressed as:

[0100]

[0101] In the formula: E a As the activation energy, k 25 is the reaction rate constant of the mineral at 25℃.

[0102] By combining the above equations, discretizing the wellbore fluid in one dimension, using the formation temperature field as the boundary condition, and solving the problem using the Newton-Raphson iterative method, the real-time flash surface depth of the geothermal fluid in the wellbore and the real-time scaling rate at different depths can be obtained.

[0103] Based on the above, this embodiment sets the scale inhibitor injection rate and injection depth according to the real-time flash surface depth and the real-time scaling rate at different depths, so as to achieve better scale inhibition effect and save on scale inhibitor usage. Furthermore, the lifting unit and injection unit are automatically controlled by the control module to inject the scale inhibitor, achieving intelligent control.

[0104] Specifically: the injection depth of the scale inhibitor depends on the real-time flash surface depth, and is generally slightly lower than the real-time flash surface depth; the injection rate of the scale inhibitor depends on the real-time scaling rate at different depths, and the injection rate should be avoided to be too high or too low.

[0105] Furthermore, the system also includes an early warning module, which is connected to the downhole monitoring module and the analysis module respectively;

[0106] The early warning module calculates the scale precipitation saturation index based on the preset scale precipitation threshold and the real-time calculated well fluid thermodynamic balance constant, and determines whether to issue an early warning based on the scale precipitation saturation index.

[0107] The analysis module performs data inversion only after the early warning module issues an early warning.

[0108] The present invention also introduces a scale precipitation saturation index for early warning, and only after the early warning, that is, after the scale precipitation saturation index exceeds the preset threshold, will the scale inhibitor dosing scheme be generated, thus avoiding the system from constantly performing complex calculations.

[0109] The formula for calculating the thermodynamic equilibrium constant of wellbore fluid is:

[0110]

[0111] Where a, b, c, d, and e are fitting parameters, each obtained based on the relationship curve between mineral solubility and temperature; T represents the downhole geothermal fluid temperature obtained from real-time monitoring.

[0112] The scale precipitation threshold is specifically defined as the fluid state threshold at which mineral-containing water reaches saturation and scale precipitates.

[0113] The scale precipitation saturation index is the ratio of the wellbore fluid thermodynamic equilibrium constant to the scale precipitation threshold.

[0114] The early warning module is used to issue an alert when the scale precipitation saturation index exceeds a preset threshold. The preset threshold can be set according to actual conditions, and can be set to 0.3 or 0.4.

[0115] Because different scale inhibitors have different scale inhibition effects, this invention can also generate corresponding scale inhibitor dosing schemes in real time based on real-time flash surface depth, real-time scaling rate at different depths, and scale inhibition rate data of the scale inhibitor. This allows the system to be compatible with a variety of scale inhibitors.

[0116] The scale inhibition rate data of the scale inhibitor are as described above: scale inhibition rate at different temperatures and pressures (obtained through indoor tests in a high-temperature and high-pressure reactor).

[0117] Furthermore, even after the scale inhibitor is determined, the scale inhibition effect of different scale inhibitor ratios will still vary. Therefore, the scale inhibition rate data in this embodiment may also include scale inhibition rate data for different scale inhibitor ratios, and the scale inhibitor dosing plan generated in real time by the dosing plan generation module also includes the scale inhibitor ratio; the injection module also includes a scale inhibitor configuration unit connected to the injection unit; the scale inhibitor configuration unit is used to configure the scale inhibitor with the corresponding ratio according to the scale inhibitor ratio in the real-time generated scale inhibitor dosing plan. In this way, the scale inhibitor with the corresponding ratio can be configured according to the real-time situation to meet the real-time scale inhibition requirements.

[0118] The aforementioned scale inhibitor preparation unit includes a scale inhibitor stock solution storage tank, a deionized water storage tank, a scale inhibitor preparation tank, connecting pipelines, and valves at various levels. The opening of the scale inhibitor preparation unit and the outflow rate of the scale inhibitor stock solution and deionized water are controlled by receiving instructions from the control module via solenoid valves. The deionized water storage tank can be connected to the cooling water of a geothermal power plant as a water source. The scale inhibitor preparation tank contains a stirrer to ensure uniform preparation and a level gauge to monitor the volume of the prepared scale inhibitor.

[0119] The surface portion of the injection module specifically includes: an injection pump, valves at various levels, capillary injection tubing, a winch, a heat tracing device, and a tower; the injection pump and solenoid valves receive instructions from the control module to adjust the injection rate of the scale inhibitor; the capillary injection tubing connects the injection pump and valves to inject the scale inhibitor downhole; the winch, via an electric motor, receives instructions from the control module to pull and lower the capillary injection tubing to adjust the injection depth; and the heat tracing device ensures the flowability of the scale inhibitor in low-temperature weather through heating.

[0120] The downhole portion of the injection module specifically includes: a counterweight rod, a check valve, and a well depth sensor. The weight of the counterweight rod needs to be designed in advance based on the wellbore parameters to meet the downhole requirements. The check valve receives instructions from the control module to open and prevents geothermal fluid from entering the capillary injection pipe. The well depth sensor determines the injection depth to coordinate with the winch adjustment.

[0121] The installation and debugging of this system shall be carried out in accordance with the following steps:

[0122] Step zero involves preliminary preparations, including well logging to obtain basic parameters of the wellbore and geothermal fluids, followed by indoor experiments on the scale inhibition rate of the scale inhibitor using a high-temperature and high-pressure reactor to obtain scale inhibition rate data.

[0123] Step 1: Fix the location of the main control system (high-performance computer), and install the wellbore scaling prediction and evaluation software, as well as the data acquisition instrument and the main control system driver on the main control system. Run the software according to the case study attached to the software for verification. The various physicochemical parameters at the wellhead and the temperature-pressure downhole are virtually input according to the preset values ​​in the case study. Then, input the previous logging data and scale inhibition rate data into the software's database.

[0124] Step 2: Connect the wireless transmission device to the main control system, and then use a portable computer with the cloud monitoring platform installed to ping the main control system to verify the connectivity of data transmission.

[0125] Step 3: Close the wellbore valves and stop the production system;

[0126] Step 4: Install downhole monitoring instruments and wellhead monitoring instruments, and connect them to the main control system via a data acquisition unit. In the driver software of the data acquisition unit, calibrate various types of sensors according to their categories.

[0127] Step 5: Construct the chemical dosing system, including a lifting unit, an injection unit, and a scale inhibitor preparation unit. The maximum length of the capillary injection tube and the weight of the counterweight rod are designed according to the wellbore parameters.

[0128] Step 6: Connect the electrical control equipment of the dosing system, including solenoid valves, motors, injection pumps, check valves, etc., to the main control system through the control module, and complete the signal connectivity test in the driver software of the control module;

[0129] Step 7: The lifting unit with counterweight is lowered into the well;

[0130] Step 8: Open the wellbore valves, restart the production system, and maintain the operation of the geothermal wellbore scaling trend early warning and intelligent chemical dosing cloud control system.

[0131] The system's operation flow is as follows:

[0132] (1) The downhole monitoring instrument measures the real-time temperature-pressure distribution of the geothermal fluid in the wellbore, and the wellhead monitoring instrument measures the real-time data of the temperature, pressure, flow rate, pH value, hardness and carbon dioxide concentration of the geothermal fluid at the wellhead.

[0133] (2) The monitoring data is transmitted to the wellbore scaling prediction and evaluation software built into the high-performance computer. The software stores the monitoring data through a database.

[0134] (3) Wellbore scaling prediction and evaluation software obtains the flash surface depth of geothermal fluid in the wellbore and the scaling rate at different depths based on monitoring data and pre-input inversion, and calculates the saturation index of geothermal fluid in the wellbore.

[0135] (4) A traffic light system is used to provide early warning of wellbore scaling: when the saturation index is less than 0.3, no scaling will occur and a green light will be lit; when the saturation index is between 0.3 and 0.5, scaling may occur and a yellow light will be lit; when the saturation index is greater than 0.5, scaling will definitely occur and a red light will be lit.

[0136] (5) Transmit the early warning signal to the cloud monitoring platform via wireless transmission equipment;

[0137] (6) When the saturation index exceeds the set threshold for starting the dosing system (the system is preset to 0.4, which can be adjusted according to needs), the dosing system is automatically started, including the solenoid valve, motor, injection pump, check valve and other equipment.

[0138] (7) The software automatically calculates and generates a dosing plan, determines the dosing position (depth) based on the flash surface depth, and determines the scale inhibitor ratio and scale inhibitor injection rate (dosage) by combining the scaling rate with the previously pre-input scale inhibition rate data.

[0139] (8) The control module converts the dosing plan generated by the software into executable instructions to control each device in the dosing system to implement the dosing plan;

[0140] (9) Continue to monitor the real-time data of geothermal fluids downhole and wellhead. The wellbore scaling prediction and evaluation software automatically evaluates the scale prevention and inhibition effect based on this data and adjusts the dosing scheme. The dosing system is executed by the control module.

[0141] It should also be noted that:

[0142] (1) In the long term, it is necessary to re-log the well and update the logging data in the software database every once in a while; it is also necessary to re-enter the scale inhibition rate data when changing the type of scale inhibitor.

[0143] (2) The cloud monitoring platform can be installed on desktop computers, portable computers, mobile phones, electronic tablets, industrial systems and other devices. Managers can also manually control the dosing system on the cloud monitoring platform through wireless transmission equipment.

[0144] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A smart descaling system for geothermal wells, characterized in that, The system includes a wellhead monitoring module, a downhole monitoring module, a main control system, and an injection module. The main control system comprises an analysis module, a chemical dosing scheme generation module, and a control module connected in sequence. The injection module includes a connected lifting unit and an injection unit. The wellhead monitoring module and the downhole monitoring module are connected to the analysis module, and the control module is also connected to the lifting unit and the injection unit. The wellhead monitoring module is used to monitor geothermal fluid data at the wellhead in real time. The downhole monitoring module is used to monitor geothermal fluid data at the downhole in real time. The analysis module is used to invert the real-time flash surface depth of the geothermal fluid in the wellbore and the real-time scaling rate at different depths based on the real-time monitored geothermal fluid data at the wellhead and downhole, as well as the multi-field, multi-phase, and multi-component non-isothermal phase change flow model. The dosing scheme generation module generates a corresponding scale inhibitor dosing scheme in real time based on the real-time flash surface depth and the real-time scaling rate at different depths. The scale inhibitor dosing scheme includes the scale inhibitor injection rate and the scale inhibitor injection depth. The control module controls the lifting unit to move up and down according to the scale inhibitor injection depth in the real-time generated dosing scheme, ensuring the injection unit reaches the corresponding depth within the geothermal wellbore. The control module also controls the injection unit to inject scale inhibitor according to the scale inhibitor injection rate in the real-time generated dosing scheme. The system also includes an early warning module, which is connected to the downhole monitoring module and the analysis module. The early warning module calculates the scale precipitation saturation index based on a preset scale precipitation threshold and the real-time calculated wellbore fluid thermodynamic equilibrium constant, and determines whether to issue an early warning based on the scale precipitation saturation index. The analysis module performs data inversion only after the early warning module issues an early warning. The formula for calculating the wellbore fluid thermodynamic equilibrium constant is: ;in, 、 、 、 、 All of these are fitting parameters, and each fitting parameter is obtained based on the relationship curve between mineral solubility and temperature. This indicates the downhole geothermal fluid temperature obtained through real-time monitoring; the scale precipitation threshold is specifically defined as the fluid state threshold when mineral-containing water reaches saturation and scale precipitates; the scale precipitation saturation index is the ratio of the wellbore fluid thermodynamic equilibrium constant to the scale precipitation threshold; the early warning module is used to issue an early warning when the scale precipitation saturation index exceeds the preset threshold.

2. The intelligent descaling system for geothermal wells according to claim 1, characterized in that, The wellhead monitoring module is used to monitor the wellhead geothermal fluid flow rate, pH value, concentration of various metal cations, and carbon dioxide concentration in the wellhead geothermal fluid in real time; the downhole monitoring module is used to monitor the downhole geothermal fluid temperature and pressure in real time.

3. The intelligent descaling system for geothermal wells according to claim 1, characterized in that, The dosing scheme generation module generates corresponding scale inhibitor dosing schemes in real time based on the real-time flash surface depth, the real-time scaling rate at different depths, and the scale inhibition rate of the scale inhibitor.

4. The intelligent descaling system for geothermal wells according to claim 3, characterized in that, The scale inhibition rate data of the scale inhibitor includes scale inhibition rate data of different scale inhibitor ratios; the scale inhibitor dosing plan generated in real time by the dosing plan generation module also includes the scale inhibitor ratio; the injection module also includes a scale inhibitor configuration unit connected to the injection unit; the control module is also used to control the scale inhibitor configuration unit to configure the scale inhibitor with the corresponding ratio according to the scale inhibitor ratio in the scale inhibitor dosing plan generated in real time.

5. The intelligent descaling system for geothermal wells according to claim 4, characterized in that, The scale inhibitor preparation unit includes a scale inhibitor stock solution storage tank, a deionized water storage tank, and a scale inhibitor preparation tank. The scale inhibitor stock solution storage tank and the deionized water storage tank are respectively connected to the scale inhibitor preparation tank via pipelines. The scale inhibitor preparation tank has a built-in agitator. Solenoid valves are installed at the pipeline connections between the scale inhibitor stock solution storage tank, the deionized water storage tank, and the scale inhibitor preparation tank. The control module controls the opening and closing of the solenoid valves according to the scale inhibitor ratio in the real-time generated scale inhibitor dosing plan, so that the deionized water and the scale inhibitor stock solution enter the scale inhibitor preparation tank, and controls the agitator to stir, thereby completing the preparation of the scale inhibitor with the corresponding ratio.

6. The intelligent descaling system for geothermal wells according to claim 1, characterized in that, The injection unit includes an injection tube and a heat tracing device surrounding the outer surface of the injection tube.

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