Super heavy oil electric heating reservoir heat transfer experimental device and experimental method

Abstract

The invention relates to the technical field of thickened oil recovery, in particular to a super-thickened oil electric heating reservoir heat transfer experiment device and method, and the super-thickened oil electric heating reservoir heat transfer experiment device comprises a stratum model, a multi-element injection system and an output system. According to the invention, the actual injection and production well spacing is adopted as the sand filling model of the model length, the temperature rise characteristic of the inter-well reservoir in the actual SAGD well electric preheating starting process can be simulated, and the change trend of the temperature field can be analyzed, so that the problems that the heat transfer of the test device has no similar proportion and the simulation error of the conventional small-size model is large in the prior art can be solved. Static electric heating at the two ends and dynamic heat transfer experiments in the steam and oil displacement solvent injection process can be carried out, and different accelerated heat transfer modes are explored. The control module can measure the temperature difference and correspondingly adjust the heating power of each heating section of the electric heater, and is matched with the heat preservation sleeve to realize an equivalent heat insulation boundary, so that heat transfer from two ends to the center position along the model body is not interfered by heat loss of the model wall and the outer side in the heat transfer process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy oil recovery, and is an electric heating reservoir heat transfer experimental device and experimental method for super heavy oil. BACKGROUND

[0002] Heavy oil is an important component of China's energy, and steam huff and puff is the most widely used heavy oil development method. Since the 1980s, heavy oil reservoirs have been mainly developed by steam huff and puff, and at the present stage, domestic heavy oil reservoir thermal recovery still mainly uses steam huff and puff. However, the carbon emission of the conventional steam injection recovery method commonly used at present exceeds 1.6tCO2 / t oil, which pollutes the environment, so it is urgent to explore low-carbon and efficient development technologies.

[0003] For oil wells developed by conventional SAGD (Steam Assisted Gravity Drainage), the steam consumption is large during the conventional steam injection cycle preheating start-up process, and according to statistics, the steam consumption required after preheating is usually greater than 15,000 tons, but the steam heat utilization rate is less than 30%. In order to improve the heat utilization rate, it is necessary to explore a direct heating method at the well bottom to realize efficient utilization of heat energy.

[0004] Therefore, it is of great significance to maintain the sustainable and efficient development of China's heavy oil resources to study an electric heating reservoir heat transfer experimental device and experimental method for super heavy oil.

[0005] A Chinese patent document with publication number CN120231562A discloses a physical simulation experimental device and experimental method for heavy oil reservoir steam huff and puff. The physical simulation experimental device for heavy oil reservoir steam huff and puff includes an injection system, an output metering system, a physical model device, and an energy storage system. The physical model device simulates a heavy oil reservoir steam huff and puff well. The injection system is connected to the physical model device to inject various fluids into the physical model device. The output metering system is connected to the physical model device to separate and meter the amount of output fluid from the physical model device. The energy storage system is connected to the physical model device to simulate the supply boundary of the formation. The physical simulation experimental device and experimental method for heavy oil reservoir steam huff and puff simulate the energy supply of the temperature field wave to the formation according to the steam sweep situation to simulate the reservoir saturation change after steam huff and puff, and are used to study the remaining oil occurrence law after steam huff and puff. However, it cannot well simulate the actual injection and production well spacing, and the formation model heat transfer has no similar proportion. The simulation error of the conventional small size model is large, which affects the research on the interwell reservoir temperature rise characteristics during the electric preheating start-up process of the actual SAGD well.

[0006] The Chinese patent document with publication number CN115704291A discloses a thick oil reservoir multi-element heat composite oil displacement experimental device, system and method. The device includes an oil displacement system component, a first driving member and a plurality of first containers connected in parallel in a delivery pipeline and respectively containing a plurality of oil displacement systems; an oil reservoir simulation component including a formation model and a second driving member, the input end of the formation model being respectively connected with a crude oil container and a formation water container; and an electric heating component having an input port communicating with the delivery pipeline and an output port communicating with the input end of the formation model, for heating the oil displacement system input thereto to a predetermined temperature. Based on the technical solution of the present application, the experimental device can perform different types of oil displacement and displacement experiments, and can also generate a multi-element composite oil displacement system based on a plurality of oil displacement systems. The oil displacement system can also be heated and its temperature can be guaranteed to meet the needs of multi-element heat composite displacement. The device is also compatible with conventional slug injection, meeting more experimental needs. However, the heating device is located outside the formation model, and the experimental results have a large deviation from the direct well bottom heating technology.

[0007] In summary, it is necessary to provide an ultra-heavy oil reservoir heat transfer experimental device that can simulate well bottom direct heating, has a model length equivalent to the actual injection-production well spacing, and can also be used for mixing experiments of different displacement systems, to study the interwell reservoir temperature rise characteristics during the actual SAGD well electric preheating startup process. SUMMARY

[0008] The present application provides an ultra-heavy oil electric heating reservoir heat transfer experimental device and experimental method, which overcomes the shortcomings of the prior art and effectively solves the problem that the existing experimental devices and methods cannot well simulate the actual injection-production well spacing, the formation model heat transfer has no similar proportion, the simulation error of conventional small size models is large, and the research on the interwell reservoir temperature rise characteristics during the actual SAGD well electric preheating startup process is affected.

[0009] One of the technical solutions of the present application is realized by the following measures: an experimental device for heat transfer of super heavy oil electric heating reservoir, comprising a formation model, a multi-element injection system and a production system, both ends of the formation model are provided with injection inlets and production outlets, electric heaters are installed in the middle of both ends of the sand filling model, the electric heaters can directly heat the formation model to provide different experimental temperatures required by the experiment; the formation model comprises at least one sand filling model, wherein the multiple sand filling models connected in series are used to simulate heat transfer experiments of different well spacings, the sand filling model at one end is used to simulate a steam injection horizontal well, the sand filling model at the other end is used to simulate a production horizontal well, and the sand filling models between the two are used to simulate interwell reservoirs; the multi-element injection system is in communication with the two injection inlets of the formation model respectively, and is used to inject experimental fluids into the formation model, wherein the experimental fluids include but are not limited to steam, oil displacement solvent, crude oil and formation water; the production system is in communication with the two production outlets of the formation model respectively, and can separate and measure the gas and liquid of the formation model; a temperature and pressure monitoring system is also connected to the formation model to monitor the temperature change on the surface of the electric heater and the temperature transfer and pressure conditions inside the model.

[0010] The following is a further optimization or / and improvement of the above-mentioned technical solutions of the application: Each of the above-mentioned sand filling models can comprise a heat preservation sleeve and a hollow sand filling pipe, the heat preservation sleeve is installed outside the sand filling pipe, and the heat preservation sleeve is provided with mounting holes along the length direction outside the heat preservation sleeve, which are matched with the temperature and pressure monitoring system; the free ends of the sand filling pipes corresponding to the positions of both ends of the formation model are detachably and sealingly installed with blocking end covers, and each blocking end cover is provided with mounting holes matched with the electric heater, the multi-element injection system and the production system.

[0011] The above-mentioned temperature and pressure monitoring system can comprise a first temperature sensor, a second temperature sensor, a pressure measurement unit, a data acquisition module and a control module, a plurality of first temperature sensors can be uniformly and interval arranged along the length direction outside the electric heater to detect the temperature on the surface of the electric heater; a plurality of second temperature sensors can be uniformly and interval arranged along the length direction outside the formation model to detect the temperature transfer inside the formation model; a plurality of pressure measurement units can be interval arranged along the length direction of the side surface of the formation model, and the both ends of the formation model can also be respectively provided with pressure measurement units, the number of pressure measurement units is much less than the number of temperature measurement units, and the plurality of pressure measurement units are cooperated to detect the pressure conditions inside the formation model; the data acquisition module can automatically acquire the measurement data of the first temperature sensor, the second temperature sensor and the pressure measurement unit, and upload the measurement data to the control module, and the control module can dynamically adjust the heating power of the electric heater according to the difference between the measurement data of the first temperature sensor and the measurement data of the second temperature sensor.

[0012] The electric heater can be an electric heater with a segmented heating function, and the control module can dynamically adjust the number of heating segments of the electric heater according to the difference between the measurement data of the first temperature sensor and the measurement data of the second temperature sensor, so as to adjust the heating power of the electric heater.

[0013] One end of the formation model can also be connected with a back pressure controller for controlling the pressure in the formation model during the experiment.

[0014] The multi-component injection system can include a plurality of intermediate containers, an injection pipeline, a first driving member, a steam generator and a second driving member, the plurality of intermediate containers are connected in parallel in the injection pipeline and respectively contain a plurality of experimental fluids, an output end of the injection pipeline is communicated with two injection ports of the formation model, the first driving member is connected to the injection pipeline and can output the experimental fluids in the intermediate containers from the two injection ports into the formation model, the steam generator is connected with the two injection ports of the formation model, and the second driving member is connected with the steam generator and can deliver steam from the two injection ports into the formation model.

[0015] The production system can include a gas-liquid separator, a production pipeline, a gas flow meter and an electronic balance measurement system, the gas-liquid separator is communicated with two production outlets of the formation model through the production pipeline, a gas outlet end of the gas-liquid separator is connected with the gas flow meter, and a liquid outlet end of the gas-liquid separator is connected with the electronic balance measurement system for measuring the amount of produced liquid.

[0016] The second technical solution of the present application is realized by the following measures: an electric heating reservoir heat transfer experiment method for super heavy oil, which adopts a super heavy oil reservoir thermal recovery physical simulation experiment device, including: Step 1, preparation stage: open the sand filling model, complete the sand filling and compaction of the model, and reseal the sand filling model, wherein after the sand filling and compaction, the electric heater, the first temperature sensor, the second temperature sensor and the pressure measurement unit are buried in the predetermined position according to the requirement, then the multi-component injection system and the production system are connected to the sand filling model respectively, and the connection of the temperature and pressure monitoring system with the data acquisition module and the control module is completed.

[0017] Step 2, saturate the sand filling model with water: inject formation water into the sand filling model through the multi-component injection system, if the water injection amount reaches the first set pore volume multiple, stop water injection, and age for the first set period at the original temperature.

[0018] Step 3, saturate the sand filling model with oil: inject crude oil into the sand filling model through the multi-component injection system, if the oil injection amount reaches the second set pore volume multiple, and the water content of the produced matter is less than the set threshold, then stop oil injection, and age for the second set period at the original temperature.

[0019] Step 4, model preheating: turn on the electric heater at both ends of the formation model, and start the thermal tracking compensation of the formation model, the temperature inside the formation model is the same as the temperature inside the heat preservation sleeve, and the temperature transmission inside the model is monitored through the measurement data of the second temperature sensor.

[0020] Step 5, heat transfer experiment: after the model is preheated, a static heat transfer experiment is carried out to simulate the static heat transfer reservoir temperature rise between SAGD injection and production wells, or a dynamic heat transfer experiment is carried out to simulate the preheating of the injection displacement agent slug assisted by electric heating stimulation, wherein the displacement agent is steam or oil displacement solvent.

[0021] The following is a further optimization or / and improvement of the above technical solutions: The above static heat transfer experiment is carried out to simulate the static heat transfer reservoir temperature rise between SAGD injection and production wells, which comprises: Step a1, continuously heat the two ends of the formation model by the electric heater, determine that the surface temperature of the electric heater is kept in the first set temperature interval by the first temperature sensor, and monitor the temperature transmission inside the model through the measurement data of the second temperature sensor.

[0022] Step a2, monitor the temperature change of the center point of the formation model through the measurement data of the second temperature sensor located at the central position, stop heating when the temperature of the center point of the formation model rises to the second set temperature interval, record the heating time, and the temperature change inside the formation model.

[0023] The above dynamic heat transfer experiment is carried out to simulate the preheating of the injection displacement agent slug assisted by electric heating stimulation, which comprises: Step b1, continuously heat the two ends of the formation model by the electric heater for a first set time, ensure that the surface temperature of the electric heater is kept in the first set temperature interval by monitoring the measurement data of the first temperature sensor, and monitor the temperature transmission inside the model through the measurement data of the second temperature sensor.

[0024] Step b2, inject displacement agent slug into the formation model from two injection ports through the multi-element injection system, and monitor the injection pressure inside the formation model through the pressure measurement unit, stop injecting displacement agent when the injection pressure reaches the upper limit of the reservoir pressure, record the injection amount of displacement agent, continue heating by the electric heater, and continuously monitor the temperature transmission inside the model through the measurement data of the second temperature sensor.

[0025] Step b3, after the electric heater continues to heat for a second set time, open the production system and start liquid discharge at a set speed, stop liquid discharge when the liquid discharge speed is less than a set threshold, and record the liquid discharge amount.

[0026] Step b4, repeat step b2 to step b3 until a predetermined injection round is reached, wherein step b2 to step b3 is one injection round.

[0027] Step b5, monitor the temperature change of the center point of the formation model through the measurement data of the second temperature sensor in the central position, and when the temperature of the center point of the formation model rises to the second set temperature interval, the electric heater stops heating, and records the heating time, the temperature change in the formation model and the injection round and other dynamic data.

[0028] The present application can simulate the interwell reservoir temperature rise characteristics in the electric preheating start-up process of the actual SAGD well, analyze the temperature field change trend, and solve the heat transfer without similar proportion and large simulation error of the conventional small size model of the prior art. During the experiment, dynamic heat transfer experiments during the injection of steam and oil displacement solvent can be carried out, and different accelerated heat transfer modes can be explored. According to the measurement difference between the first temperature sensor and the second temperature sensor, that is, the temperature difference between the heating temperature of the heater and the internal temperature of the formation model, the control module can automatically adjust the heating power of each heating section of the electric heater in sections, and cooperate with the heat preservation sleeve to realize the equivalent adiabatic boundary, so that the heat transfer along the model body from both ends to the central position is not disturbed by the model wall and external heat loss. The back pressure controller can control the pressure in the formation model in real time to realize the electric heating simulation experiment under different pressure conditions. BRIEF DESCRIPTION OF DRAWINGS

[0029] FIG. 1 is a schematic structural diagram of the embodiment 1 of the present application. Figure 1 FIG. 2 is a schematic structural diagram of the embodiment 2 of the present application.

[0030] FIG. 3 is a schematic structural diagram of the embodiment 3 of the present application. Figure 2 FIG. 4 is a schematic structural diagram of the embodiment 4 of the present application. Figure 1 FIG. 5 is a schematic structural diagram of the embodiment 5 of the present application.

[0031] FIG. 6 is a schematic structural diagram of the embodiment 6 of the present application. Figure 3 FIG. 7 is a schematic structural diagram of the embodiment 7 of the present application.

[0032] The codes in the drawings are as follows: 1 is an electric heater, 2 is a heat preservation sleeve, 3 is a sand filling pipe, 4 is a flange, 5 is a blocking end cover, 6 is a first temperature sensor, 7 is a second temperature sensor, 8 is a pressure measurement unit, 9 is a data acquisition module, 10 is a control module, 11 is a back pressure controller, 12 is an intermediate container, 13 is an injection pipeline, 14 is a first driving member, 15 is a steam generator, 16 is a second driving member, 17 is a gas-liquid separator, 18 is a production pipeline, 19 is a gas flow meter, 20 is an electronic balance measurement system, 21 is a steam injection horizontal well, 22 is a production horizontal well, and 23 is an interwell reservoir. DETAILED DESCRIPTION

[0033] The present application is not limited by the following examples, and the specific implementation can be determined according to the technical solutions of the present application and the actual situation.

[0034] In the present application, the relative position relationship of each component is described according to the layout of the accompanying drawings, such as the position relationship of front, back, up, down, left, right, etc. is determined according to the layout direction of the accompanying drawings. Figure 1

[0035] The present application will be further described below in conjunction with examples and accompanying drawings: Example 1: As shown in Figs. 1, 2 and 3, the super heavy oil electric heating reservoir heat transfer experimental device includes a formation model, a multi-element injection system and a production system. The formation model has injection inlets and production outlets at both ends. The middle part of the two ends of the sandpack model is equipped with an electric heater 1. The electric heater 1 can directly heat the formation model to provide different experimental temperatures required by the experiment. The formation model includes at least one sandpack model. The multiple sandpack models connected in series are used to simulate heat transfer experiments of different well spacings. The sandpack model at one end is used to simulate the steam injection horizontal well 21, and the sandpack model at the other end is used to simulate the production horizontal well 22. The sandpack model between them is used to simulate the interwell reservoir 23. Figure 1 2 In the above technical solution, the use of single sandpack model is the existing conventional technical solution in the field, which can be used to simulate static heat transfer, injection fluid forced convection heat transfer, etc., so as to analyze the temperature rising characteristics of interwell reservoir 23 under different heat transfer states, and provide experimental basis for super heavy oil electric heating thermal recovery technology research.

[0036] As shown in Figs. 1, 2 and 3, the formation model can be provided with three sandpack models connected and sealed together. The left sandpack model is used to simulate the steam injection horizontal well 21 (referred to as I well, the same below), the right sandpack model is used to simulate the production horizontal well 22 (i.e. production well, referred to as P well, the same below), and the middle sandpack model is used to simulate the interwell reservoir 23, so as to realize static and dynamic heat transfer experiments of different well spacings. During the experiment, the sandpack model can use the actual injection-production well (i.e. IP well) spacing as the model length to simulate the interwell reservoir temperature rising characteristics during the SAGD well electric preheating startup process.

[0037] Figure 2 As shown in Figs. 1, 2 and 3, the formation model can be provided with three sandpack models connected and sealed together. The left sandpack model is used to simulate the steam injection horizontal well 21 (referred to as I well, the same below), the right sandpack model is used to simulate the production horizontal well 22 (i.e. production well, referred to as P well, the same below), and the middle sandpack model is used to simulate the interwell reservoir 23, so as to realize static and dynamic heat transfer experiments of different well spacings. During the experiment, the sandpack model can use the actual injection-production well (i.e. IP well) spacing as the model length to simulate the interwell reservoir temperature rising characteristics during the SAGD well electric preheating startup process.

[0038] ​​​According to requirements, the pressure resistance of the formation model can be 8 MPa, and the temperature resistance can be 500 DEG C. The formation model can be a three-section sand filling model, each section being 1 m to 2 m long, and the experiment can be completed independently or assembled. The experiment is used to simulate dynamic heat transfer at different well spacings. The diameter of each sand filling model can be 20 cm, and the total length can be the sum of the lengths of the three sand filling models. The two ends of each sand filling model can be sealed by flanges 4, and the synchronous electric heating preheating condition under the actual IP well spacing can be simulated.

[0039] In this embodiment, each sand filling model can be 1.5 m long, and the three sand filling models can be disassembled and sealed together after installation, with a total length of 4.5 m. The sand used for filling and compacting the sand layer can be actual core sand, or it can be sandstone with equal particle size and proportion according to the particle size analysis results of the core. Two injection ports and two production outlets are provided on the formation model, which are located at opposite ends of the formation model. The multi-component injection system can inject the required experimental fluid into the formation model through the two injection ports, and the production can be discharged from the two production outlets at the same time. The production is a gas-liquid mixture.

[0040] According to requirements, the electric heater 1 can use existing heating devices in the heavy oil thermal recovery technology field, which usually include resistance wires or heating rods or heating tapes and outer sleeves. The outer sleeve is used to cover the resistance wire to avoid direct contact with oil and water. Insulating filler such as magnesium oxide can be filled between the outer sleeve and the resistance wire. In order to control the heating temperature, the electric heater 1 usually has a temperature sensor to measure the temperature of the surface of the electric heater 1. According to the detection data of the temperature sensor, the heating temperature of the resistance wire can be controlled under the control of an external computer to perform heating at different temperatures.

[0041] The multi-component injection system is in communication with the two injection ports of the formation model, and is used to inject experimental fluid into the formation model. The experimental fluid includes but is not limited to steam, oil displacement solvent, crude oil and formation water. The production system is in communication with the two production outlets of the formation model, and can separate the production of the formation model into gas and liquid and measure the gas and liquid separately.

[0042] In the technical solution, the multi-element injection system can include a steam injection system, a saturated oil injection system, a saturated water injection system, and an oil displacement solvent injection system. The above-mentioned subsystems can be connected with the injection ports at both ends of the formation model through injection pipelines, and the control valves are used to control the injection of the required experimental fluids to both ends of the formation model. The steam injection system is used to inject high-temperature steam into the formation model from both ends of the formation model to simulate the heat transfer experiment of steam injection slug displacement. The saturated oil injection system can inject oil into the formation model to complete the required saturated oil operation process of the experiment. The saturated water injection system can inject water into the formation model to complete the required saturated water operation process of the experiment. The oil displacement solvent injection system can inject oil displacement solvent into the formation model from both ends of the formation model to simulate the heat transfer experiment of oil displacement solvent injection slug displacement.

[0043] According to the requirements, the steam injection system can be realized by an injection pump, a steam generator, and a control valve or other steam sources in the prior art. The saturated oil injection system can be realized by an injection pump, an oil tank, and a control valve. The saturated water injection system can be realized by a pipeline-connected injection pump, a water tank, and a control valve. The oil displacement solvent injection system can be realized by an injection pump, a solvent tank, and a control valve.

[0044] The multi-element injection system is installed together with the sand-filled model in a three-section series connection and sealed, which can simulate static heat transfer, forced convection heat transfer of injected fluids, and dynamic heat transfer of different displacement media such as injected solvents and steam.

[0045] The production system can use the existing technology in the field, or the following technical solution: a gas-liquid collection and separation device connected with the production outlets at both ends of the formation model through pipelines to collect the production and separate the gas and liquid; a balance and a gas automatic metering device connected with the gas-liquid collection and separation device. The balance can automatically meter the mass of the produced gas and liquid, and the gas automatic metering device can collect and meter the produced gas. The gas-liquid collection and separation device can be placed in a thermostat to ensure that the produced gas is in a gaseous state.

[0046] According to the requirements, the balance can be replaced by a liquid flow meter that can detect oil and water production. The gas automatic metering device can be a mass flow meter.

[0047] A temperature and pressure monitoring system is also connected to the formation model to monitor the temperature change on the surface of the electric heater 1 and the temperature transfer and pressure conditions inside the model.

[0048] In the above technical solution, the temperature and pressure monitoring system can adopt existing technology in this field, or it can adopt the following technical solution: a temperature sensor installed on the electric heater 1 to detect the heating temperature; a formation temperature measurement sensor uniformly installed on the outer wall of the formation model to monitor the transmission of formation temperature. To ensure the accuracy of the measurement data, the formation model can be placed in a constant temperature chamber or an insulation layer can be installed outside the formation model, and the formation temperature measurement sensor can be installed inside the insulation layer to isolate it from the outside; a temperature sensor installed at the center of the outer wall of the formation model to detect the temperature at the center of the formation model; and multiple high-precision pressure sensors or pressure transmitters uniformly installed on the formation model to monitor the pressure changes inside the formation model and ensure that the pressure inside the formation model is maintained within a preset range.

[0049] Depending on the requirements, this device can also be equipped with a data acquisition system to collect in real time the temperature and pressure of the model system, the liquid and gas metering of the production system, and the injection volume of each experimental fluid injected into the injection system. After the above data is input into the computer, a database can be formed to serve as the basis for experimental data analysis and to analyze the temperature field changes of heat transfer in the formation model.

[0050] This invention features a reasonable and compact structure, making it easy to use. The sand-filled model can use the actual injection-production well spacing as the model length, thereby simulating the inter-well reservoir temperature rise characteristics during the electric preheating start-up process of an actual SAGD well and analyzing the temperature field change trend. This addresses the problems of lack of similarity scale in heat transfer and large simulation errors in conventional small-sized models in existing technologies. During the experiment, dynamic heat transfer experiments can also be conducted during simultaneous static electric heating at both ends and the injection of steam and oil displacement solvent into the sluice, exploring different accelerated heat transfer methods.

[0051] The above-mentioned experimental device for heat transfer in electrically heated reservoirs of extra-heavy oil can be further optimized and / or improved according to actual needs: Example 2: As an optimization of the above examples, as shown in the appendix Figure 1 , 2 As shown, each sand-filled model includes an insulation sleeve 2 and a hollow sand-filling pipe 3. The insulation sleeve 2 is installed on the outside of the sand-filling pipe 3. The insulation sleeve 2 has installation holes along its length that are compatible with the temperature and pressure monitoring system. Adjacent sand-filling pipes 3 are sealed together by flanges 4. The free ends of the sand-filling pipes 3 at both ends of the formation model can be detachably and sealed with end caps 5. Each end cap 5 has installation holes that are compatible with the electric heater 1, the multi-element injection system and the production system.

[0052] With this configuration, the insulation sleeve 2 can effectively prevent heat leakage from the formation model, enabling the outer side of the formation model to achieve an equivalent thermal insulation boundary. This ensures that during heat transfer, heat is transferred along the formation model from one end to the other (or from both ends to the center), without being affected by heat loss from the sand-filled pipe 3 wall and the outer side.

[0053] Each sealing end cap 5 has mounting holes adapted to the multi-element injection system and the production system, which can respectively form an injection port and a production port; a connector adapted to the multi-element injection system and the production system can be installed in both the injection port and the production port, which is a known technology in the art; the multi-element injection system and the two injection connectors can be connected through a pipeline, and the production system and the two production connectors can also be connected through a pipeline.

[0054] According to requirements, the temperature sensor used to measure the internal temperature of the formation model in the temperature and pressure monitoring system can be installed in the mounting holes that are compatible with the temperature and pressure monitoring system, which are set along the length of the outer side of the insulation sleeve 2. The installation of the temperature sensor is evenly distributed along the length of the formation model to improve the measurement accuracy of the internal temperature of the model.

[0055] During use, both electric heaters 1 are installed in mounting holes on the sealing end cap 5 that are compatible with the electric heaters 1; the hollow sand-filling pipe 3 can be used for sand filling. The sand used for filling can be actual core samples from the oil layer, or sandstone of equal particle size and proportion can be used based on the core particle size analysis results. After completing the sand filling and sealing the model, it is necessary to test the airtightness of the formation model. The airtightness test method can adopt existing technology in this field.

[0056] To prevent fluid leakage from the sand-filling pipe 3, sealing structures or sealing elements must be installed between sand-filling pipes 3 and between sand-filling pipe 3 and the sealing cap. These can be detachably installed via flange 4 or threads. Flange 4 has a simple and reliable connection structure and is more commonly used.

[0057] Example 3: As an optimization of the above examples, as shown in the appendix Figure 1 , 2 As shown in Figure 3, the temperature and pressure monitoring system includes a first temperature sensor 6, a second temperature sensor 7, a pressure measurement unit 8, a data acquisition module 9, and a control module 10. Several first temperature sensors 6 are evenly spaced along the length of the outer side of the electric heater 1 to detect the surface temperature of the electric heater 1; multiple second temperature sensors 7 are evenly spaced along the length of the outer side of the formation model to detect the temperature transfer within the formation model.

[0058] According to the requirement, the first temperature sensor 6 and the second temperature sensor 7 can be thermocouple temperature sensors commonly used in the art, but other types of temperature sensors can also be used; in order to reduce the influence of the external environment on the second temperature sensor 7, the formation model can be placed in a thermostat or a heat preservation layer is provided outside the formation model, and the second temperature sensor 7 is protected by the heat preservation layer.

[0059] The formation model is provided with a plurality of pressure measuring units 8 along the length direction of the side surface, and the two ends of the formation model are also provided with pressure measuring units 8. The number of pressure measuring units 8 is much less than the number of temperature measuring units, and the plurality of pressure measuring units 8 are used to detect the pressure condition in the formation model.

[0060] According to the requirement, the pressure measuring unit 8 can be a pressure digital display meter with a high-precision pressure sensor or a high-precision pressure transmitter. In the embodiment, a total of 6 pressure measuring units 8 are provided, of which one pressure measuring unit 8 is provided at each end of the formation model, and four pressure measuring units 8 are uniformly and evenly spaced along the length direction of the side surface of the formation model. In order to facilitate the installation of the pressure measuring unit 8, the middle part of the two plugging end covers 5 can be provided with mounting holes matched with the pressure measuring unit 8, and the outer side of the sand filling pipe 3 is uniformly and evenly spaced along the length direction and provided with mounting holes matched with the pressure measuring unit 8. The heat preservation sleeve 2 corresponding to the position of the mounting hole is provided with a through hole corresponding to the position of the mounting hole.

[0061] The data acquisition module 9 automatically acquires the measurement data of the first temperature sensor 6, the second temperature sensor 7 and the pressure measuring unit 8, and uploads the measurement data to the control module 10. The control module 10 can dynamically adjust the heating power of the electric heater 1 according to the difference between the measurement data of the first temperature sensor 6 and the measurement data of the second temperature sensor 7.

[0062] According to the requirement, the control module 10 can be divided into a field control box and a computer, and the data acquisition module 9 can be divided into a field data acquisition module and a remote data acquisition module. The control box includes a box body, a field data acquisition module and a field control module, and the field data acquisition module and the field control module are installed in the box body. The field data acquisition module can upload the measurement data of the first temperature sensor 6, the second temperature sensor 7 and the pressure measuring unit 8 to the field control module. The field control module can adjust the heating power of the electric heater 1 according to the measurement data of the first temperature sensor 6, or dynamically adjust the heating power of the electric heater 1 according to the difference between the measurement data of the first temperature sensor 6 and the measurement data of the second temperature sensor 7. The field control module can be realized based on the single-chip microcomputer or PLC in the prior art.

[0063] In this embodiment, the remote data acquisition module can also be connected with the multi-component injection system and the production system. The remote data acquisition module can upload the measured data of the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8, the injection amount of each experimental fluid in the multi-component injection system, and the measurement results of the production in the production system to the computer. The computer is installed with experimental monitoring and analysis software. The software can simultaneously monitor the temperature and pressure and has the temperature interface inversion function. The software can automatically record the measured data of the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8, the injection amount of each experimental fluid in the multi-component injection system, the measurement results of the production in the production system, the heating time, and the like. The software can automatically form the temperature field of the formation model and generate the relationship curve between the production fluid volume (production fluid speed) and the temperature and pressure, thereby assisting the researchers to find the temperature rising characteristics of the interwell reservoir and study the heat transfer effect of different heat transfer experiments. The computer and the experimental monitoring and analysis software can also remotely control and adjust the heating power of the electric heater 1.

[0064] In this embodiment, the electric heater 1 is a segmented electric heater 1 with a segmented heating function. The control module 10 can dynamically adjust the number of heating segments of the electric heater 1 according to the difference between the measured data of the first temperature sensor 6 and the second temperature sensor 7, so as to adjust the heating power of the electric heater 1. Figure 1 2 In the above technical solution, the electric heater 1 with the segmented heating function is matched with the heat preservation sleeve 2, the first temperature sensor 6, the second temperature sensor 7, the data acquisition module 9, and the control module 10. The control module 10 can dynamically adjust the number of heating segments of the electric heater 1 according to the difference between the measured data of the first temperature sensor 6 and the second temperature sensor 7, so as to adjust the heating power of the electric heater 1 according to the control program. The segmented heat tracking compensation and heat preservation are realized, the temperature rising situation is accurately simulated and tracked, and the equivalent adiabatic boundary is realized. The heat transfer from both ends to the middle position (or from one end to the other end) of the formation model is not disturbed by the heat loss of the pipe wall and the outside of the sand filling pipe 3.

[0065] According to the requirements, both of the electric heaters 1 are segmented electric heaters 1 with 13 temperature control functions. Each heating segment is provided with a first temperature sensor 6 outside. The heating segments of the left electric heater 1 are sequentially L1 heating segment, L2 heating segment, L3 heating segment, …, and L13 heating segment from left to right. The heating segments of the right electric heater 1 are sequentially R1 heating segment, R2 heating segment, R3 heating segment, …, and R13 heating segment from right to left. The time interval of the monitoring and instruction adjustment of the control module 10 can be 1 minute, which can be adjusted according to the actual experimental requirements.

[0066] According to the requirements, both of the electric heaters 1 are segmented electric heaters 1 with 13 temperature control functions. Each heating segment is provided with a first temperature sensor 6 outside. The heating segments of the left electric heater 1 are sequentially L1 heating segment, L2 heating segment, L3 heating segment, …, and L13 heating segment from left to right. The heating segments of the right electric heater 1 are sequentially R1 heating segment, R2 heating segment, R3 heating segment, …, and R13 heating segment from right to left. The time interval of the monitoring and instruction adjustment of the control module 10 can be 1 minute, which can be adjusted according to the actual experimental requirements. ​

[0067] The first temperature sensors 6 on the left side of the electric heater 1 are arranged from left to right, and the measured data set is T1=(T11, T12, T13, …, T113). The first temperature sensors 6 on the right side of the electric heater 1 are arranged from right to left, and the measured data set is T2=(T21, T22, T23, …, T213). The second temperature sensors 7 are arranged from left to right on the outside of the formation model, and the measured data set is T3=(T31, T32, T33, …, T327). T314 is the measured value of the temperature at the center of the formation model (i.e., the center point of the model).

[0068] The measured difference set of the first temperature sensors 6 and the second temperature sensors 7 on the left side is Δt1=T1-T3=(T11-T31, T12-T32, T13-T33, …, T113-T313)=(Δt131, Δt132, Δt133, …, Δt1313). The control module 10 compares each element in Δt1 with the set limit value, and adjusts the heating power of the L1 heating section to the L13 heating section according to the comparison result. The measured difference set of the first temperature sensors 6 and the second temperature sensors 7 on the right side is Δt2=(T21-T327, T22-T326, T23-T325, …, T213-T315)=(Δt231, Δt232, Δt233, …, Δt2313). The control module 10 compares each element in Δt2 with the set limit value, and adjusts the heating power of the R1 heating section to the R13 heating section according to the comparison result, as follows: In each monitoring and instruction adjustment time interval, the data acquisition module 9 automatically acquires the measured data of the first temperature sensors 6 and the measured data of the second temperature sensors 7, respectively forming the measured data set T1, T2 of the first temperature sensors 6 and the measured data set T3 of the second temperature sensors 7. The control module 10 determines whether each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is greater than or equal to the first set value. If yes, the corresponding heating section is heated at full power. If no, the heating power of the corresponding heating section is adjusted linearly according to the measured difference. The control module 10 determines whether each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is less than the second set value. If yes, the corresponding heating section is stopped. If no, the heating power of the corresponding heating section is adjusted linearly according to the measured difference. The first set value can be set to 100℃, and the second set value can be set to 1℃.

[0069] For example, if the 13th element in the measured difference set Δt1 between T1 and T3 is not less than 100℃, the L13 heating section is full-power heating; if the 7th element is less than 100℃ and greater than or equal to 1℃, the heating power of the L7 heating section is linearly adjusted according to the measured difference; if the 1st element is less than 1℃, the L1 heating section stops heating; if the 11th element in the measured difference set Δt2 between T2 and T3 is not less than 100℃, the R11 heating section is full-power heating; if the 5th element is less than 100℃ and greater than or equal to 1℃, the heating power of the R5 heating section is linearly adjusted according to the measured difference; if the 2nd element is less than 1℃, the R2 heating section stops heating.

[0070] The linear adjustment of the heating power of the electric heater 1 according to the measured difference can be realized by the following method: for example, if the full-power heating of each heating section is 1200W, in each monitoring and instruction adjustment time interval, the control module 10 judges whether each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is in the interval of 1℃ to 10℃, if yes, the control module 10 automatically adjusts the heating power of the corresponding heating section to 100W; the control module 10 judges whether each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is in the interval of 11℃ to 20℃, if yes, the control module 10 automatically adjusts the heating power of the corresponding heating section to 200W; the control module 10 judges whether each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is in the interval of 21℃ to 30℃, if yes, the control module 10 automatically adjusts the heating power of the corresponding heating section to 300W; and so on, with the increase of the endpoint temperature in each temperature interval, for each corresponding increase of 10℃ in the endpoint value of the temperature interval, the heating power of the heating section increases by 100W compared with the heating power of the previous temperature interval, with the increase of the temperature difference between the surface temperature of the heating section and the corresponding measured point outside the formation model, the heating power of the heating section increases linearly; if the control module 10 judges that each element in the measured difference set Δt1 (or Δt2) between T1 (or T2) and T3 is in the interval of 91℃ to 100℃, the control module 10 automatically adjusts the heating power of the corresponding heating section to 1000W.

[0071] Embodiment 5: As an optimization of the above embodiments, as shown in FIG. 5, one end of the formation model is also connected with a back pressure controller 11 for controlling the pressure in the formation model during the experiment. Figure 1 The back pressure controller 11 is connected with the control module 10, and the control module 10 can control the pressure in the formation model by adjusting the opening of the back pressure controller 11.

[0072] In this way, the pressure in the formation model can be effectively controlled, and when the pressure in the formation model exceeds the set pressure (set threshold) of the back pressure controller 11, the back pressure controller 11 will automatically release pressure.

[0073] According to the requirements, the back pressure controller 11 is an intelligent back pressure regulating controller, which can control the pressure inside the formation model in real time and realize the electric heating simulation experiment under different pressure conditions; it can also be connected to an external computer to control and record the pressure changes inside the formation model through computer control.

[0074] Example 6: As an optimization of the above embodiments, as shown in the appendix Figure 1 As shown, the multi-element injection system includes several intermediate containers 12, injection pipelines 13, a first drive unit 14, a steam generator 15, and a second drive unit 16. The intermediate containers 12 are connected in parallel in the injection pipelines 13 and each contains a variety of experimental fluids. The output end of the injection pipelines 13 is connected to two injection ports of the formation model. The first drive unit 14 is connected to the injection pipelines 13 and can output the experimental fluids in the intermediate containers 12 from the two injection ports into the formation model. The steam generator 15 is connected to the two injection ports of the formation model, and the second drive unit 16 is connected to the steam generator 15 and can deliver steam from the two injection ports into the formation model.

[0075] In this embodiment, the experimental fluid contained in the intermediate container 12 includes, but is not limited to, oil displacement solvents, crude oil, and formation water. To reduce the procurement cost of the first driving component and minimize the footprint of the invention, the intermediate container 12 can be a piston container commonly used in the art. The piston container has a structure similar to a syringe or a double-acting hydraulic cylinder, with a piston inside. The piston can divide the container's inner cavity into upper and lower chambers. The upper chamber of the piston contains the experimental fluid, and the lower chamber is connected to a plunger pump and a liquid tank through pipes. When the plunger pump is activated, it pushes the piston upward, pressurizing the experimental fluid and injecting it into the formation model. Each piston container is connected to the first driving component 14 via a control valve, so that the piston in different piston containers can be controlled by the same first driving component 14 to inject the required experimental fluid into the formation model. The first driving component 14 can be a plunger pump, which can also measure the injection volume of the experimental fluid. The control valve can be a solenoid valve.

[0076] The second drive unit 16 can provide power to ensure that the steam injection pressure meets the experimental requirements, such as reaching 5 MPa, so that the high-temperature steam generated by the steam generator 15 can be smoothly injected into the formation model. The second drive unit 16 can also be a plunger pump, which can also measure the amount of steam injected, or it can be measured by a separately set gas flow meter.

[0077] Example 7: As an optimization of the above embodiments, as shown in the appendix Figure 1As shown, the production system includes a gas-liquid separator 17, a production pipeline 18, a gas flow meter 19, and an electronic balance measurement system 20. The gas-liquid separator 17 is connected to the two production outlets of the formation model through the production pipeline 18. The gas outlet of the gas-liquid separator 17 is connected to the gas flow meter 19, and the liquid outlet of the gas-liquid separator 17 is connected to the electronic balance measurement system 20 for measuring the amount of produced liquid.

[0078] With this configuration, the gas-liquid separator 17 can separate the liquid and gas of the product, and obtain the flow rate of the corresponding product through the gas flow meter 19 and the electronic balance measurement system 20, thereby reflecting the effect of the oil displacement experiment.

[0079] Depending on the requirements, to facilitate the measurement of the output, the gas flow meter 19 and the electronic balance measurement system 20 can be connected to the data acquisition module 9. The data acquisition module 9 collects relevant data and uploads it to a computer. The electronic balance measurement system 20 can be a digital balance, and the gas flow meter 19 can be a digital display wet gas flow meter. Drainage control valves are installed on the output pipelines 18 corresponding to the two outlet locations to control the discharge of the output.

[0080] Example 8: This experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil uses a physical simulation experimental device for thermal recovery of extra-heavy oil reservoirs, including: Step 1, Preparation stage: Open the sand-filling model, complete the sand filling and compaction, and reseal the sand-filling model. After compacting the sand, the electric heater 1, the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8 need to be buried in the predetermined positions as required. Then, the multi-element injection system and the output system are connected to the sand-filling model respectively, and the temperature and pressure monitoring system is connected to the data acquisition module 9 and the control module 10.

[0081] Step 2, Saturation of the sand-filled model with water: Formation water is injected into the sand-filled model through a multi-element injection system. If the injection volume reaches a first set multiple of the pore volume, the injection is stopped, and the model is aged for a first set period at the original temperature.

[0082] Step 3, Saturating the sand-filled model with oil: Crude oil is injected into the sand-filled model through a multi-element injection system. If the oil injection volume reaches the second set multiple of the pore volume and the water content of the product is less than the set threshold, the oil injection is stopped and the product is aged for the second set cycle at the original temperature.

[0083] In the above technical solution, the first set pore volume multiple can be 4PV, and the second set pore volume multiple can be 2PV, where PV is the pore volume multiple, which is the value obtained by dividing the injection volume or production volume by the pore volume, indicating the amount injected or produced; the set threshold can be 1%, which can be adjusted according to experimental requirements.

[0084] Depending on the requirements, both the first and second set periods can be set within 36 to 52 hours, and can be selected according to the experimental requirements.

[0085] Step 4, Model Preheating: Turn on the electric heaters 1 at both ends of the formation model and start thermal tracking compensation of the formation model to keep the temperature inside the formation model the same as the temperature inside the insulation sleeve 2. Monitor the temperature transfer inside the model through the measurement data of the second temperature sensor 7.

[0086] Step 5, conduct heat transfer experiments: After the model is preheated, conduct static heat transfer experiments to simulate the static heat transfer and reservoir temperature rise between SAGD injection and production wells, or conduct dynamic heat transfer experiments to simulate preheating by slug-assisted electric heating during displacing agent injection, wherein the displacing agent is steam or oil displacement solvent.

[0087] The above-mentioned experimental method for heat transfer in electrically heated reservoirs of extra-heavy oil can be further optimized and / or improved according to actual needs: Example 9: As an optimization of Example 8, the static heat transfer experiment to simulate the static heat transfer and reservoir temperature rise between SAGD injection and production wells includes: Step 5a1: The electric heater 1 continuously heats both ends of the formation model. The first temperature sensor 6 determines that the surface temperature of the electric heater 1 is maintained within the first set temperature range. The measurement data of the second temperature sensor 7 is used to monitor the temperature transfer inside the model.

[0088] Step 5a2: The temperature change at the center point of the formation model is monitored by the measurement data (i.e., T314) of the second temperature sensor 7 located in the center. When the temperature at the center point of the formation model rises to the second set temperature range (i.e., T314 falls into the second set temperature range), the electric heater 1 stops heating and records the heating time and the temperature change inside the formation model (i.e., the measurement data of the second temperature sensor 7).

[0089] In the above technical solution, the temperature range of the first set temperature range can be 330℃ to 350℃, and the temperature range of the second set temperature range can be 130℃ to 150℃, which can be selected according to the experimental requirements.

[0090] Static heat transfer experiments can simulate the temperature rise of the reservoir during static heat transfer between SAGD injection and production wells, and study the temperature field, heat transfer rate and heat diffusion efficiency along the path between injection and production wells.

[0091] Example 10: As an optimization of Example 8, the dynamic heat transfer experiment, used to simulate preheating via slug-assisted electric heating during displacer injection, includes: Step 5b1: The electric heater 1 continuously heats both ends of the formation model for a first set time. The surface temperature of the electric heater 1 is kept within the first set temperature range by monitoring the measurement data of the first temperature sensor 6. The temperature transfer inside the model is monitored by the measurement data of the second temperature sensor 7.

[0092] Step 5b2: Displacer slugs are injected into the formation model simultaneously from two injection ports using a multi-element injection system. The injection pressure inside the formation model is monitored by the pressure measurement unit 8. When the injection pressure reaches the upper limit of the reservoir pressure, the injection of displacement agent is stopped, and the amount of displacement agent injected is recorded. The electric heater 1 continues to heat the model, and the temperature transfer inside the model is continuously monitored by the measurement data of the second temperature sensor 7.

[0093] Step 5b3: After the electric heater 1 continues to heat for the second set time, the production system is turned on and the liquid is discharged at the set speed. When the discharge speed is less than the set threshold, the discharge is stopped and the discharge volume is recorded.

[0094] As needed, the liquid can be drained from both ends of the formation model through the production system. The start / stop of the liquid draining operation can be controlled by the liquid draining control valve installed on the production pipeline 18.

[0095] Step 5b4, repeat steps 5b2 to 5b3 until the predetermined injection round is reached, wherein steps 5b2 to 5b3 constitute one injection round.

[0096] Step 5b5: The temperature change at the center point of the formation model is monitored by measuring the data (i.e., T314) of the second temperature sensor 7 located in the center. When the temperature at the center point of the formation model rises to the second set temperature range, the electric heater 1 stops heating and records dynamic data such as heating time, temperature change inside the formation model and injection cycle.

[0097] In the above technical solution, the first set duration can range from several hours to several months, such as 10 days to 5 months; the second set duration can range from several days to several months, such as 1 day to 10 days; the temperature range of the first set temperature range can be 330℃ to 350℃; the temperature range of the second set temperature range can be 130℃ to 150℃; the upper limit of reservoir pressure can be 5MPa; the set speed can be 200 ml / min; the set threshold can be 5 ml / min; and the set injection rounds can be 15 to 20 rounds. Researchers can choose according to experimental needs or reference experience.

[0098] By conducting dynamic heat transfer experiments with different displacing agents, the preheating effect of slug-assisted electric heating huff and puff with different displacing agents can be studied.

[0099] Example 11: This experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil uses a physical simulation experimental device for thermal recovery of extra-heavy oil reservoirs, including: Step 1, Preparation Stage: Open the sand-filling model, complete the sand filling and compaction, and reseal the sand-filling model. After compacting the sand, the electric heater 1, the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8 need to be buried in the predetermined positions as required. Then, connect the multi-element injection system to the injection port on the sand-filling model, connect the production system to the extraction port on the sand-filling model, and complete the connection of the temperature and pressure monitoring system to the data acquisition module 9 and the control module 10.

[0100] Step 2, Saturation of the sand-filled model with water: Inject formation water into the sand-filled model through a multi-element injection system. If the injection volume reaches 4PV, stop the injection and age the model at the original temperature for 48 hours.

[0101] Step 3, Saturating the sand-filled model with oil: Inject crude oil into the sand-filled model through a multi-element injection system. If the oil injection volume reaches 2PV and the water content of the product is less than 1%, stop the oil injection and age the product at the original temperature for 48 hours.

[0102] Step 4, Model Preheating: Turn on the electric heaters 1 at both ends of the formation model and start thermal tracking compensation of the formation model to keep the temperature inside the formation model the same as the temperature inside the insulation sleeve 2. Monitor the temperature transfer inside the model through the measurement data of the second temperature sensor 7.

[0103] Step 5, conduct heat transfer experiments: After model preheating, conduct static heat transfer experiments to simulate static heat transfer and reservoir temperature rise between SAGD injection and production wells, including: Step 5a1: The electric heater 1 continuously heats both ends of the formation model. The first temperature sensor 6 determines that the surface temperature of the electric heater 1 is maintained within 330°C to 350°C. The measurement data of the second temperature sensor 7 is used to monitor the temperature transfer inside the model.

[0104] Step 5a2: The temperature change at the center point of the formation model is monitored by the measurement data (i.e., T314) of the second temperature sensor 7 located in the center. When the temperature at the center point of the formation model rises to between 130°C and 150°C (i.e., T314 falls within the second set temperature range), the electric heater 1 stops heating and records the heating time and the temperature change inside the formation model (i.e., the measurement data of the second temperature sensor 7).

[0105] This embodiment can simulate the temperature rise of the reservoir in static heat transfer between SAGD injection and production wells. As can be seen from the temperature field along the route between the injection and production wells, the temperature rise rate between the static heat transfer wells is relatively slow. The main reason is that it is just heat conduction, which mainly relies on heat diffusion, which is inefficient. The heat diffusion conforms to FICK's first law. It takes 2 days for the temperature at the center point of the model to rise to 130°C to 150°C (i.e., the heating time is 2 days).

[0106] Example 12: This experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil uses a physical simulation experimental device for thermal recovery of extra-heavy oil reservoirs, including: Step 1, Preparation Stage: Open the sand-filling model, complete the sand filling and compaction, and reseal the sand-filling model. After compacting the sand, the electric heater 1, the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8 need to be buried in the predetermined positions as required. Then, connect the multi-element injection system to the injection port on the sand-filling model, connect the production system to the extraction port on the sand-filling model, and complete the connection of the temperature and pressure monitoring system to the data acquisition module 9 and the control module 10.

[0107] Step 2, Saturation of the sand-filled model with water: Inject formation water into the sand-filled model through a multi-element injection system. If the injection volume reaches 4PV, stop the injection and age the model at the original temperature for 48 hours.

[0108] Step 3, Saturating the sand-filled model with oil: Inject crude oil into the sand-filled model through a multi-element injection system. If the oil injection volume reaches 2PV and the water content of the product is less than 1%, stop the oil injection and age the product at the original temperature for 48 hours.

[0109] Step 4, Model Preheating: Turn on the electric heaters 1 at both ends of the formation model and start thermal tracking compensation of the formation model to keep the temperature inside the formation model the same as the temperature inside the insulation sleeve 2. Monitor the temperature transfer inside the model through the measurement data of the second temperature sensor 7.

[0110] Step 5, conduct heat transfer experiments: After model preheating, dynamic heat transfer experiments are conducted to simulate preheating via slug-assisted electric heating during displacing agent injection. The displacing agent is an oil displacement solvent, including: Step 5b1: The two ends of the formation model are continuously heated for 3 hours by electric heater 1. The surface temperature of electric heater 1 is kept between 330°C and 350°C by monitoring the measurement data of the first temperature sensor 6. The temperature transfer inside the model is monitored by the measurement data of the second temperature sensor 7.

[0111] Step 5b2: The oil displacement solvent slug is injected into the formation model simultaneously from two injection ports through the multi-element injection system. The injection pressure inside the formation model is monitored by the pressure measurement unit 8. When the injection pressure reaches the upper limit of reservoir pressure of 5 MPa, the injection of oil displacement solvent is stopped and the injection volume of oil displacement solvent is recorded. The electric heater 1 continues to heat, and the temperature transfer inside the model is continuously monitored by the measurement data of the second temperature sensor 7.

[0112] Step 5b3: After the electric heater 1 continues heating for 1 day, turn on the production system and start draining at a rate of 200 ml / min. When the draining rate is less than 5 ml / min, stop draining and record the amount of liquid drained.

[0113] Step 5b4, repeat steps 5b2 to 5b3 until 15 to 20 rounds are reached, where steps 5b2 to 5b3 constitute one injection round.

[0114] Step 5b5: The temperature change at the center point of the formation model is monitored by the measurement data (i.e., T314) of the second temperature sensor 7 located in the center. When the temperature at the center point of the formation model rises to between 130°C and 150°C, the electric heater 1 stops heating and records dynamic data such as heating time, temperature change inside the formation model, and injection cycle.

[0115] Experimental results show that using the solvent-assisted electric heating huff and puff method for preheating SAGD injection and production wells significantly accelerated the preheating rate by 53% and shortened the preheating time; at the same time, a large amount of crude oil was produced, accounting for 12% of the crude oil produced in the saturation model.

[0116] Example 13: This experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil uses a physical simulation experimental device for thermal recovery of extra-heavy oil reservoirs, including: Step 1, Preparation Stage: Open the sand-filling model, complete the sand filling and compaction, and reseal the sand-filling model. After compacting the sand, the electric heater 1, the first temperature sensor 6, the second temperature sensor 7, and the pressure measuring unit 8 need to be buried in the predetermined positions as required. Then, connect the multi-element injection system to the injection port on the sand-filling model, connect the production system to the extraction port on the sand-filling model, and complete the connection of the temperature and pressure monitoring system to the data acquisition module 9 and the control module 10.

[0117] Step 2, Saturation of the sand-filled model with water: Inject formation water into the sand-filled model through a multi-element injection system. If the injection volume reaches 4PV, stop the injection and age the model at the original temperature for 48 hours.

[0118] Step 3, Saturating the sand-filled model with oil: Inject crude oil into the sand-filled model through a multi-element injection system. If the oil injection volume reaches 2PV and the water content of the product is less than 1%, stop the oil injection and age the product at the original temperature for 48 hours.

[0119] Step 4, Model Preheating: Turn on the electric heaters 1 at both ends of the formation model and start thermal tracking compensation of the formation model to keep the temperature inside the formation model the same as the temperature inside the insulation sleeve 2. Monitor the temperature transfer inside the model through the measurement data of the second temperature sensor 7.

[0120] Step 5, conduct heat transfer experiments: After model preheating, conduct static heat transfer experiments to simulate static heat transfer and reservoir temperature rise between SAGD injection and production wells, where the displacement agent is steam, including: Step 5b1: After continuously heating both ends of the formation model with electric heater 1 for 12 hours, the surface temperature of electric heater 1 is kept between 330°C and 350°C by monitoring the measurement data of the first temperature sensor 6, and the temperature transfer inside the model is monitored by the measurement data of the second temperature sensor 7.

[0121] Step 5b2: Steam slugs are injected into the formation model simultaneously from two injection ports using a multi-element injection system. The injection pressure inside the formation model is monitored by the pressure measurement unit 8. When the injection pressure reaches the upper limit of reservoir pressure of 5 MPa, steam injection is stopped and the amount of steam injected is recorded. The electric heater 1 continues to heat the model, and the temperature transfer inside the model is continuously monitored by the measurement data of the second temperature sensor 7. The temperature of the steam is 200°C and the injection pressure is 5 MPa.

[0122] Step 5b3: After the electric heater 1 continues heating for 1 day, turn on the production system and start draining at a rate of 200 ml / min. When the draining rate is less than 5 ml / min, stop draining and record the amount of liquid drained.

[0123] Step 5b4, repeat steps 5b2 to 5b3 until 15 to 20 rounds are reached, where steps 5b2 to 5b3 constitute one injection round.

[0124] Step 5b5: The temperature change at the center point of the formation model is monitored by the measurement data (i.e., T314) of the second temperature sensor 7 located in the center. When the temperature at the center point of the formation model rises to between 130°C and 150°C, the electric heater 1 stops heating and records dynamic data such as heating time, temperature change inside the formation model, and injection cycle.

[0125] Experimental results show that using steam slug-assisted electric heating huff and puff for SAGD injection-production well preheating significantly accelerated the preheating rate by 30% and shortened the preheating time; at the same time, a large amount of crude oil was produced, accounting for 6% of the crude oil produced in the saturation model.

[0126] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. An experimental device for heat transfer in an electrically heated reservoir of extra-heavy oil, characterized in that it includes a formation model, a multi-element injection system, and a production system. Both ends of the formation model are equipped with injection ports and production ports. Both ends of the sand-filled model are equipped with electric heaters in the middle. The electric heaters can directly heat the formation model and provide different experimental temperatures required for the experiment. The formation model includes at least one sand-filled model, in which multiple sand-filled models connected in series are used to simulate heat transfer experiments at different well spacings. One end of the sand-filled model is used to simulate a steam injection horizontal well, the other end of the sand-filled model is used to simulate a production horizontal well, and the sand-filled model in between is used to simulate the inter-well reservoir. The multi-element injection system is connected to two injection ports of the formation model and is used to inject experimental fluids into the formation model. The experimental fluids include, but are not limited to, steam, oil displacement solvents, crude oil and formation water. The production system is connected to the two production outlets of the formation model, enabling gas-liquid separation and separate metering of the gas and liquid components in the production of the formation model. The formation model is also connected to a temperature and pressure monitoring system to monitor the temperature changes on the surface of the electric heater, as well as the temperature transfer and pressure conditions inside the model.

2. The experimental device for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 1, characterized in that each sand-filled model includes an insulation sleeve and a hollow sand-filling pipe, an insulation sleeve is installed on the outside of the sand-filling pipe, and the outside of the insulation sleeve is provided with mounting holes adapted to the temperature and pressure monitoring system along the length direction. The two adjacent sand-filling pipes are connected by a flange seal. The free ends of the sand-filling pipes at both ends of the corresponding formation model can be detachably sealed with end caps. Each end cap is equipped with mounting holes that are compatible with the electric heater, multi-element injection system and production system.

3. The experimental apparatus for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 1 or 2, characterized in that the temperature and pressure monitoring system includes a first temperature sensor, a second temperature sensor, a pressure measurement unit, a data acquisition module, and a control module. Several first temperature sensors are evenly spaced along the length of the outer side of the electric heater to detect the temperature of the surface of the electric heater; multiple second temperature sensors are evenly spaced along the length of the outer side of the formation model to detect the temperature transfer inside the formation model. Several pressure measurement units are spaced along the length of the side of the formation model, and pressure measurement units are also provided at both ends of the formation model. The number of pressure measurement units is much smaller than the number of temperature measurement units. Multiple pressure measurement units work together to detect the pressure conditions inside the formation model. The data acquisition module automatically collects measurement data from the first temperature sensor, the second temperature sensor, and the pressure measurement unit, and uploads the measurement data to the control module. The control module can dynamically adjust the heating power of the electric heater based on the difference between the measurement data from the first temperature sensor and the measurement data from the second temperature sensor.

4. The experimental apparatus for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 3, characterized in that the electric heater is an electric heater with segmented heating function, and the control module can dynamically adjust the number of heating segments of the electric heater according to the difference between the measurement data of the first temperature sensor and the measurement data of the second temperature sensor, so as to adjust the heating power of the electric heater. Alternatively, one end of the formation model is also connected to a back pressure controller, which is used to control the pressure inside the formation model during the experiment.

5. The experimental apparatus for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 1, 2, or 4, characterized in that the multi-element injection system comprises several intermediate containers, injection pipelines, a first driving component, a steam generator, and a second driving component. Several intermediate containers are connected in parallel in the injection pipeline and each contains a variety of experimental fluids. The output end of the injection pipeline is connected to two injection ports of the formation model. The first driving component is connected to the injection pipeline and can output the experimental fluids in the intermediate containers from the two injection ports into the formation model. The steam generator is connected to the two injection ports of the formation model, and the second drive unit is connected to the steam generator, which can deliver steam from the two injection ports into the formation model.

6. The experimental apparatus for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 3, characterized in that the multi-element injection system comprises several intermediate containers, injection pipelines, a first driving component, a steam generator, and a second driving component. Several intermediate containers are connected in parallel in the injection pipeline and each contains a variety of experimental fluids. The output end of the injection pipeline is connected to two injection ports of the formation model. The first driving component is connected to the injection pipeline and can output the experimental fluids in the intermediate containers from the two injection ports into the formation model. The steam generator is connected to the two injection ports of the formation model, and the second drive unit is connected to the steam generator, which can deliver steam from the two injection ports into the formation model.

7. The experimental apparatus for heat transfer in an electrically heated reservoir of extra-heavy oil according to any one of claims 1 to 6, characterized in that the production system includes a gas-liquid separator, a production pipeline, a gas flow meter, and an electronic balance measurement system. The gas-liquid separator is connected to the two production outlets of the formation model through the production pipeline. The gas outlet of the gas-liquid separator is connected to a gas flow meter, and the liquid outlet of the gas-liquid separator is connected to an electronic balance measurement system for measuring the amount of produced liquid.

8. A method for heat transfer experiments in an electrically heated reservoir of extra-heavy oil, characterized in that it employs the physical simulation experimental apparatus for thermal recovery of extra-heavy oil reservoirs as described in any one of claims 3 to 7, comprising: Step 1, Preparation stage: Open the sand-filled model, fill and compact the sand, and reseal the sand-filled model. After compacting the sand, the electric heater, the first temperature sensor, the second temperature sensor, and the pressure measurement unit need to be buried in the predetermined positions as required. Then, connect the multi-element injection system and the output system to the sand-filled model respectively, and complete the connection between the temperature and pressure monitoring system and the data acquisition module and control module. Step 2, Saturation of the sand-filled model with water: Formation water is injected into the sand-filled model through a multi-element injection system. If the injection volume reaches the first set multiple of the pore volume, the injection is stopped and the model is aged for the first set period at the original temperature. Step 3, Saturating the sand-filled model with oil: Crude oil is injected into the sand-filled model through a multi-element injection system. If the oil injection volume reaches the second set multiple of the pore volume and the water content of the product is less than the set threshold, the oil injection is stopped and the product is aged for the second set cycle at the original temperature. Step 4, Model Preheating: Turn on the electric heaters at both ends of the formation model and start thermal tracking compensation of the formation model. The temperature inside the formation model is kept the same as the temperature inside the insulation jacket. The temperature transfer inside the model is monitored by the measurement data of the second temperature sensor. Step 5, conduct heat transfer experiments: After the model is preheated, conduct static heat transfer experiments to simulate the static heat transfer and reservoir temperature rise between SAGD injection and production wells, or conduct dynamic heat transfer experiments to simulate preheating by slug-assisted electric heating during displacing agent injection, wherein the displacing agent is steam or oil displacement solvent.

9. The experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 8, characterized in that, The static heat transfer experiment, used to simulate the static heat transfer and reservoir temperature rise between SAGD injection and production wells, includes: Step a1: The two ends of the formation model are continuously heated by an electric heater. The surface temperature of the electric heater is kept within a first set temperature range by a first temperature sensor. The temperature transfer inside the model is monitored by the measurement data of a second temperature sensor. Step a2: Monitor the temperature change at the center point of the formation model using the measurement data from the second temperature sensor located in the center. Once the temperature at the center point of the formation model rises to within the second set temperature range, the electric heater stops heating, and the heating time and temperature change inside the formation model are recorded.

10. The experimental method for heat transfer in an electrically heated reservoir of extra-heavy oil according to claim 8, characterized in that the dynamic heat transfer experiment, used to simulate preheating via slug-assisted electrically heated injection of displacing agent, includes: Step b1: After continuously heating both ends of the formation model with an electric heater for a first set time, the surface temperature of the electric heater is kept within the first set temperature range by monitoring the measurement data of the first temperature sensor, and the temperature transfer inside the model is monitored by the measurement data of the second temperature sensor. Step b2: Displacer slugs are injected into the formation model simultaneously from two injection ports using a multi-element injection system. The injection pressure inside the formation model is monitored by a pressure measurement unit. When the injection pressure reaches the upper limit of the reservoir pressure, the injection of displacement agent is stopped, and the amount of displacement agent injected is recorded. The electric heater continues to heat the model, and the temperature transfer inside the model is continuously monitored by the measurement data of the second temperature sensor. Step b3: After the electric heater continues heating for the second set time, the production system is turned on, and liquid is discharged at the set speed. When the discharge speed is less than the set threshold, the discharge is stopped, and the discharge volume is recorded. Step b4: Repeat steps b2 to b3 until the predetermined injection round is reached, where steps b2 to b3 constitute one injection round; Step b5: Monitor the temperature change at the center point of the formation model using the measurement data from the second temperature sensor located in the center. Once the temperature at the center point of the formation model rises to within the second set temperature range, the electric heater stops heating and records the heating time, temperature changes inside the formation model, injection cycles, drainage volume, and other dynamic data.

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