Multi-element and multi-phase thermophysical property testing system and method based on transient plane heat source method

Abstract

The invention provides a multi-element and multi-phase thermophysical property testing system and method based on a transient plane heat source method, the system comprises a plane heat source host, a data acquisition and processing unit, a pressure unit, a high-pressure closed bin and a temperature control unit, and the high-pressure closed bin is located in the temperature control unit; the temperature control unit is connected to the data acquisition and processing unit, and the data acquisition and processing unit regulates and controls the test temperature of the temperature control unit; the pressure unit is connected to the high-pressure closed bin and is used for injecting a filling body into the high-pressure closed bin to apply confining pressure to formation pressure; the plane heat source host is connected to the data acquisition and processing unit and the high-pressure closed bin, and the plane heat source host applies instantaneous heat pulse to the high-pressure closed bin under the control of the data acquisition and processing unit. The method has the advantages of simple test operation, convenient data acquisition and accurate and reliable test values, and is suitable for determining the thermal conductivity, specific heat capacity and thermal diffusivity of rocks with oil, gas and water under oil reservoir conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of rock analysis, and particularly to a multi-component and multi-phase thermal property testing system and method based on the transient plane heat source method. Background Art

[0002] The transient plane heat source method is based on the principle of one-dimensional unsteady heat conduction in a plane. In an infinite medium, when a plane heat source under the initial equilibrium state receives an instantaneous heat pulse, a dynamic temperature field is generated inside the medium. By using the mathematical solution method of the heat conduction equation based on the relationship between the temperature increment on the medium surface and time, the thermal conductivity and thermal diffusivity of the medium can be obtained. This method has a relatively wide range of applications and can measure various samples such as bulk samples, thin film samples, and powders.

[0003] In oil development, the temperature field determines the viscosity field and directly affects the development effect of heavy oil. The thermal conductivity and specific heat coefficient are the main model data for heavy oil thermal recovery data simulation. Through the thermal property data, the heat absorption rate, heat conduction rate, and heat loss rate of the reservoir can be understood, which helps to analyze the temperature field and heat distribution of the reservoir, optimize the steam injection parameters, determine the gas injection speed and gas injection volume, maximize the heating area of the steam, and reach the highest average temperature of the reservoir, thereby improving the development effect of heavy oil thermal recovery.

[0004] In the Chinese patent application with the application number: CN201710047390.1, it relates to a sensor and its testing device for measuring the thermal conductivity of rock mass using the transient plane heat source method. The probe of the sensor includes a conductive nickel foil etched into a double helix structure with a radius between 6 - 7 mm. The sensor uses a polyimide film with a thickness between 60 μm and 25 μm. The testing device includes a circular test bench, a rock sample placement table, calibration screws, a fixing plate, fixing screws, and a sensor. The rock sample placement table is installed at the center of the circular test bench, and the placement table is connected to the circular test bench through calibration screws. A circular rock sample is placed on the rock sample placement table, and the circular rock sample consists of two sub-samples. The sensor is arranged between the two sub-samples and is connected to a computer through a data cable. This device can quickly and effectively measure the thermal conductivity of rock salt, providing a convenient and accurate test method for the indoor test of the thermodynamic properties of rock mass, and has important significance for shallow geothermal flux research and energy pile engineering practice.

[0005] In the Chinese patent application with application number: CN201520019659.1, a clamping device for determining the thermal properties of heavy oil samples by the plane heat source method is involved, including a heavy oil container for containing heavy oil, a hole for inserting a probe into the room to observe the heavy oil sample is provided on the side wall of the heavy oil container, and a heavy oil test probe fixing device for fixing the probe is also provided on the side wall of the heavy oil container. The probe can be kept stationary in the fluid. A heavy oil sealing device is also provided at the opening on the heavy oil container to ensure that the fluid test is not interfered by the outside world during the measurement process. The utility model expands the measurement range and accuracy of the plane heat source method in the thermal property test of heavy oil reservoirs through the clamping device. The heavy oil sample container can effectively avoid the difficulty of sample insertion and sample residue caused by the closed structure, and improve the experimental efficiency and accuracy.

[0006] In the Chinese patent application with application number: CN201910281544.2, a transient test system and method for thermal properties of rocks under high temperature and high pressure is involved. The test system includes multiple temperature measuring components; a heat preservation and pressure device, in which a pressurized heating medium flows, and a rock sample isolated from the pressurized heating medium is built in, a set confining pressure is applied to the rock sample and it is heated, and the rock sample is equipped with multiple temperature measuring components; a heating control device, which sets the temperature and heats the heat preservation and pressure device; a pressure device, which sets the pressure to pressurize the heat preservation and pressure device; a data acquisition device, which records the change of the surface temperature of the rock sample over time during the transient process; a cooling device, which cools the rock sample when the measured temperature of the rock sample reaches the set temperature; a circulation path, which connects the heat preservation and pressure device, the pressure device and the cooling device. The invention can simultaneously measure the changes of thermal conductivity and specific heat capacity of rock samples with temperature and pressure.

[0007] The above application provides a corresponding clamping device and testing method for the separate testing of rocks and crude oil. However, rocks or crude oil in the oil reservoir do not exist completely independently. Oil and water exist in the rock pores, and the distribution states of oil and water in the rock pores are also different. Oil, water, and rocks have different thermophysical parameters. Testing rocks or crude oil alone cannot truly reflect the thermophysical parameters under reservoir conditions. For this reason, we have invented a new multi-element multi-phase thermophysical property testing system and method based on the transient plane heat source method. Summary of the invention

[0008] The purpose of the present invention is to provide a multi-component and multi-phase thermophysical property testing system and method based on a transient plane heat source method for testing multi-component and multi-phase rock samples under high temperature and high pressure conditions.

[0009] The object of the present invention can be achieved by the following technical measures: A multi-component and multi-phase thermal property testing system based on the transient plane heat source method. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method includes a plane heat source mainframe, a data acquisition and processing unit, a pressure unit, a high-pressure sealed chamber, and a temperature control unit. The high-pressure sealed chamber is located in the temperature control unit; the temperature control unit is connected to the data acquisition and processing unit, and the data acquisition and processing unit regulates the test temperature of the temperature control unit; the pressure unit is connected to the high-pressure sealed chamber and applies confining pressure to the formation pressure by injecting fluid into the high-pressure sealed chamber; the plane heat source mainframe is connected to the data acquisition and processing unit and the high-pressure sealed chamber, and the plane heat source mainframe applies an instantaneous heat pulse to the high-pressure sealed chamber under the control of the data acquisition and processing unit.

[0010] The object of the present invention can also be achieved by the following technical measures:

[0011] The high-pressure sealed chamber includes a disc top seat, a disc bottom seat, two sample chambers, a test probe chamber, and a double helix test probe. The two sample chambers are distributed on the disc top seat and the disc bottom seat; the test probe chamber is placed on the disc bottom seat, and the double helix test probe is placed in the test probe chamber. The double helix test probe is placed between two identical and flat-surfaced rock samples; the plane heat source mainframe applies heat pulses of different times and intensities to the double helix test probe.

[0012] The high-pressure sealed chamber further includes a shrinkage gasket. The two sample chambers are distributed on the disc top seat and the disc bottom seat, and the sample size is adjusted by the shrinkage gasket.

[0013] The two sample chambers and the test probe chamber are vertically distributed.

[0014] The high-pressure sealed chamber further includes a pressure interface. There are 8 symmetric screw holes around the high-pressure sealed sample chamber, and the height-adjustable pressure interface is provided in the Y-axis direction and is connected to the pressure unit, which can inject fluid into the high-pressure sealed sample chamber to apply confining pressure to the formation pressure.

[0015] The high-pressure sealed chamber further includes a shrinkage joint. The double helix test probe is connected to the cable through the shrinkage joint, and the other end of the cable is connected to the plane heat source mainframe. The plane heat source mainframe applies an instantaneous heat pulse through the cable.

[0016] The data acquisition and processing unit provides test power and heating time for the double helix test probe connected to the plane heat source mainframe. The plane heat source mainframe applies heat pulses of different times and intensities to the double helix test probe. The data acquisition and processing unit measures the resistance value of the double helix structure metal wire in real time, and obtains the thermal conductivity and thermal diffusivity of the medium by using the mathematical solution method of the heat conduction equation based on the relationship between the surface temperature increase value of the core and time.

[0017] The mathematical solution method using the heat conduction equation to obtain the thermal conductivity and thermal diffusivity of the medium includes:

[0018] The calculation of the temperature increment and the characteristic time function should be determined according to formula (1):

[0019]

[0020] Where:

[0021] ΔΤ s (τ) is a function of the temperature increment on the sample surface varying with τ during the test, with the unit of Kelvin (K);

[0022] P o The output power of the probe, with the unit of watt (W);

[0023] r is the outermost radius of the double helix structure, with the unit of millimeter (mm);

[0024] λ is the thermal conductivity of the sample, with the unit of watt per meter per Kelvin (W / (m·K)); a dimensionless characteristic time function;

[0025] D(τ)D(T) should be calculated according to formula (2):

[0026]

[0027] Where:

[0028] m is the total number of turns of the double helix structure;

[0029] The integration variable of the dimensionless characteristic time function;

[0030] J o The zero-order modified Bessel function;

[0031] In the above formula, τ should be calculated according to formula (3):

[0032]

[0033] Where:

[0034] t is the test time, with the unit of second (s);

[0035] t c The calibration time, with the unit of second (s);

[0036] r is the outermost radius of the double helix structure, with the unit of millimeter (mm);

[0037] a is the thermal diffusivity of the sample, with the unit of square millimeter per second (mm 2 / s);

[0038] Calculation of the thermal diffusivity:

[0039] As known from Equation (1), ΔT S There is a linear relationship between (τ) and D(τ). By taking the thermal diffusivity a and the correction time t c as optimization variables for iterative calculations, D(τ) is calculated according to Equations (2) and (3) to make it have a strict linear correspondence with ΔT S (τ), and finally the value of the thermal diffusivity a is obtained;

[0040] Thermal conductivity calculation:

[0041] By fitting the linear relationship between △T S (τ) and D(τ) using the least squares method, the slope of this equation is the value of P in Equation (1) O / (Π 3 / 2 γλ), and finally the thermal conductivity λ of the sample is obtained.

[0042] The object of the present invention can also be achieved by the following technical measures: A multi-component and multi-phase thermal property testing method based on the transient plane heat source method. This multi-component and multi-phase thermal property testing method based on the transient plane heat source method uses a multi-component and multi-phase thermal property testing system based on the transient plane heat source method, including:

[0043] Step 1, perform sample filling and test probe placement;

[0044] Step 2, set the reservoir temperature and set the test parameters;

[0045] Step 3, set the test pressure;

[0046] Step 4, stabilize the temperature field;

[0047] Step 5, perform bridge balance and apply a heat pulse;

[0048] Step 6, perform data acquisition and processing;

[0049] Step 7, verify the validity of the measurement results.

[0050] The object of the present invention can also be achieved by the following technical measures:

[0051] This multi-component and multi-phase thermal property testing method based on the transient plane heat source method further includes, before Step 1, turning on the plane heat source mainframe and preheating for 20 minutes; performing rock sample treatment to ensure the smoothness of the rock sample surface. For rock samples with uneven surfaces, they need to be polished with sandpaper.

[0052] In Step 1, place two rock samples in the high-pressure sealed chamber respectively and select appropriate gaskets according to the rock sample size; place the test probe in the test probe chamber, and the double-spiral test probe is located exactly in the middle of the two rock samples and tightened with screws.

[0053] In step 2, place the high-pressure sealed chamber inside the temperature control unit, and set the reservoir temperature through the data acquisition and processing unit; set the pulse detection radius, test probe model, temperature, pulse power, and pulse time through the data acquisition and processing unit.

[0054] In step 3, connect the pressure unit to the high-pressure sealed chamber. After the temperature control unit reaches the set temperature, apply confining pressure to the formation pressure by injecting water and gas.

[0055] In step 4, the data acquisition and processing unit needs to be stable for more than 20 minutes, and the internal temperature of the sample-test probe-sample triple-layer structure shows a scattered distribution.

[0056] In step 5, the planar heat source mainframe balances the Wheatstone bridge. The voltage used for the Wheatstone bridge should ensure that the system current does not exceed 1 mA, and the reading of the digital voltmeter of the Wheatstone bridge test system is zero after the bridge is balanced; the planar heat source mainframe applies a heat pulse. According to the total test time and output power, apply a constant direct current to the probe to generate a heat pulse in the sample, and the sliding contact of the potentiometer should not be adjusted during the test.

[0057] In step 6, the data acquisition and processing unit collects the unbalanced voltage. During the total test time, scan and record the unbalanced voltage, that is, the potential change amount, at appropriate time intervals, and the number of acquisitions should be greater than 100 times.

[0058] In step 7, judge the validity of the measurement result according to the relationship between the measurement time t, probe radius r, and thermal diffusivity α, αt / r 2 should be between 0.3 - 1.0, otherwise adjust the measurement time or output power and re-measure.

[0059] This multi-component and multi-phase thermal property testing method based on the transient plane heat source method further includes, after step 7, step 8, conduct data precision examination. Under the same conditions, repeat steps 4 - 7 for two independent measurements; the relative deviation of the results should not be greater than 2%.

[0060] In step 8, the calculation method of thermal property parameters is as follows:

[0061] When the probe is electrically heated, the calculation of the probe resistance is shown in formula (2.1):

[0062] R(t) = R 0 {1 + β[ΔT i (t) + ΔT s (t)]} (2.1)

[0063] The calculation of thermal conductivity is shown in formula (2.2):

[0064]

[0065] The calculation of δ is shown in formula (2.3):

[0066]

[0067] The calculation of D(δ) is shown in formula (2.4):

[0068]

[0069] In formulas (2.1) - (2.4):

[0070] R(t) —— The resistance of the probe at time t;

[0071] R 0 —— The initial resistance of the probe;

[0072] β —— The temperature coefficient of resistivity (TCR) of the probe;

[0073] ΔT i (t) —— The temperature difference of the insulating thin layer of the probe;

[0074] ΔT s (t) —— The temperature difference on the surface of the sample;

[0075] q —— The output power;

[0076] r —— The radius of the outermost layer of the double - helix structure of the probe;

[0077] λ —— The thermal conductivity;

[0078] D(δ) —— The characteristic time function;

[0079] t —— The measurement time;

[0080] α —— The thermal diffusivity;

[0081] n —— The total number of turns of the double - helix structure of the probe;

[0082] σ —— The integration variable of the dimensionless characteristic time function;

[0083] J 0 —— The zero - order modified Bessel function;

[0084] l 1 、l 2 —— The summation variable not greater than the total number of turns of the double - helix structure.

[0085] This multi - component and multi - phase thermal property testing method based on the transient plane heat source method also includes, after step 8, performing data self - inspection. Before measuring each batch of samples, use a standard block for self - inspection. The relative error of the measured thermal conductivity result should be less than 3%, and the relative error of the measured thermal diffusivity result should be less than 5%.

[0086] The present invention considers the pressure field and temperature field of reservoir conditions, and a multi-component and multi-phase (oil, gas, water, core) thermal property testing method based on the transient plane heat source method, including a specially designed high-pressure sealed chamber, which is applicable to the testing of thermal property parameters of multi-component, multi-phase and multi-size cores under different saturation states; at the same time, the understanding improvement from separately considering the thermal parameters of oil, water and core to overall considering the thermal property parameters under different saturations in reservoir conditions can contribute to the improvement of software related to thermal properties. The present invention has carried out sample testing. The results show that the thermal conductivity increases with the increase of pressure, the thermal diffusivity increases with the increase of pressure, and the specific heat coefficient first increases and then decreases.

[0087] The multi-component and multi-phase thermal property testing method based on the transient plane heat source method in the present invention, based on the HotDisk double-sided measurement technology of the transient plane heat source method, includes a plane heat source main machine, a data acquisition and processing unit, and a temperature control unit, and can obtain the thermal conductivity, thermal diffusivity, and specific heat capacity at constant pressure of the core in a short time. The test operation is simple, data acquisition is convenient, the test values are accurate and reliable, and it is applicable to the determination of the thermal conductivity, specific heat capacity, and thermal diffusivity of rocks containing oil, gas, and water under reservoir conditions.

[0088] Compared with the conventional plane heat source method that does not consider reservoir conditions, does not consider the oil-water saturation, does not consider the distribution of oil and water in the core, uses atmospheric pressure single-phase testing for crude oil, and separately tests the core; moreover, the thermal property parameters of loose rock samples have poor repeatability, and the obtained thermal property parameters of loose rock samples are 1 / 3 - 1 / 2 of those of dense rock samples. The advantages of the present invention are wide application range, which can be used for the determination of the thermal conductivity, specific heat capacity, and thermal diffusivity of oil, water, oil-gas-water mixed systems, multi-component, multi-phase, multi-size rocks in different saturation states, and is convenient to implement, simple in steps, and fast in measurement. Description of the Drawings

[0089] Figure 1 It is a schematic structural diagram of the multi-component and multi-phase thermal property testing system of the transient plane heat source method of the present invention;

[0090] Figure 2 It is a schematic structural diagram of the high-pressure sealed chamber of the multi-component and multi-phase thermal property testing system of the transient plane heat source method of the present invention;

[0091] Figure 3 It is a flow chart of a specific embodiment of the multi-component and multi-phase thermal property testing method of the transient plane heat source method of the present invention;

[0092] Figure 4 It is a schematic diagram of the test curve of the thermal conductivity in a specific embodiment of the present invention;

[0093] Figure 5 It is a schematic diagram of the test curve of the thermal diffusivity in a specific embodiment of the present invention;

[0094] Figure 6Schematic diagram of the specific heat coefficient test curve in a specific embodiment of the present invention;

[0095] Figure 7 Schematic diagram of the double - helix structure test probe in a specific embodiment of the present invention;

[0096] Figure 8 Circuit diagram of the unbalanced bridge used to record the increased resistance of the probe in a specific embodiment of the present invention.

[0097] In the figure, 11: planar heat source main body; 12: data acquisition and processing unit; 13: temperature control unit; 14: high - pressure sealed chamber; 15: pressure unit; 1: disc top seat; 2: disc base; 3: fixing bolt; 4: sample chamber; 5: test probe chamber; 6: shrinkage joint; 7: shrinkage gasket; 8: pressure interface; 9: probe interface. Specific embodiments

[0098] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0099] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they specify the presence of features, steps, operations, and / or combinations thereof.

[0100] The multi - component and multi - phase thermal property test system of the transient plane heat source method of the present invention includes a data acquisition and processing unit, a temperature control unit, and a pressure unit.

[0101] The data acquisition and processing unit is respectively connected to the temperature control unit and the planar heat source main body. The high - pressure sealed sample chamber is placed in the temperature control unit, and the data acquisition and processing unit regulates the test temperature of the temperature control unit; the data acquisition and processing unit can simulate a high - pressure test system for reservoir pressure, and the pressure unit includes a high - pressure sealed chamber.

[0102] The high-pressure sealed chamber includes: a disc top seat, a disc bottom seat, fixing bolts, nuts, two sample chambers, a test probe chamber, test probes, a shrink joint, a shrink gasket, a pressure interface, and a probe interface. The two sample chambers are distributed on the disc top seat and the disc bottom seat, and the sample size is adjusted by the shrink gasket; the test probe chamber is placed on the disc bottom seat, and the double-helix test probe is placed in the test probe chamber. The sample chamber and the test probe chamber are vertically distributed, and the double-helix test probe is placed between two identical and flat-surfaced rock samples; there are 8 symmetric screw holes around the high-pressure sealed sample chamber, and a height-adjustable pressure application interface is provided in the Y-axis direction, which is connected to the pressure unit and can inject water and gas into the high-pressure sealed sample chamber, etc., to apply confining pressure to the formation pressure; the double-helix test probe is connected to the cable through the shrink joint, and the other end of the cable is connected to the plane heat source mainframe. The plane heat source mainframe applies an instantaneous heat pulse through the cable; the data acquisition and processing unit is respectively connected to the temperature control unit and the plane heat source mainframe. The high-pressure sealed sample chamber is placed in the temperature control unit, and the data acquisition and processing unit regulates the test temperature of the temperature control unit; the data acquisition and processing unit provides the test power and heating time for the double-helix test probe connected to the plane heat source mainframe. The plane heat source mainframe applies heat pulses of different times and intensities to the double-helix test probe. The data acquisition and processing unit measures the resistance value of the double-helix structure metal wire in real time, and obtains the thermal conductivity and thermal diffusivity of the medium by using the mathematical solution method of the heat conduction equation based on the relationship between the surface temperature increase of the core and time.

[0103] Inject gas and water into the high-pressure sealed chamber to apply confining pressure to the formation pressure; at the same time, set the temperature of the temperature control unit to reach the reservoir temperature. The present invention is applicable to the determination of the thermal conductivity, specific heat capacity, and thermal diffusivity of crude oil, water, oil-gas-water mixed systems, different saturated multi-component multi-phase, and multi-size rocks under reservoir conditions.

[0104] The following are specific embodiments of applying the present invention

[0105] Embodiment 1

[0106] In a specific Embodiment 1 of applying the present invention, as Figure 1 shown, the multi-component multi-phase thermal property test system of the transient plane heat source method includes a plane heat source mainframe 11, a data acquisition and processing unit 12, a pressure unit 15, a high-pressure sealed chamber 14, and a temperature control unit 13.

[0107] The high-pressure sealed chamber 14 is filled with rock samples and is located in the temperature control unit 13. The temperature control unit 13 is connected to the data acquisition and processing unit 12, and the data acquisition and processing unit regulates the test temperature of the temperature control unit 13. The pressure unit 15 is connected to the high-pressure sealed chamber 14 to inject gas and water into the high-pressure sealed chamber 14 and apply confining pressure to the formation pressure. The planar heat source mainframe 11 is connected to the data acquisition and processing unit 12 and the high-pressure sealed chamber 14. Under the control of the data acquisition and processing unit 12, the planar heat source mainframe 11 applies an instantaneous heat pulse to the high-pressure sealed chamber 14.

[0108] As Figure 2 shown, the high-pressure sealed chamber includes: a disc top seat 1, a disc bottom seat 2, fixing bolts 3, nuts, two sample chambers 4, a test probe chamber 5, test probes, a shrinkage joint 6, a shrinkage gasket 7, a pressure interface 8, and a probe interface 9. The two sample chambers 4 are distributed on the disc top seat 1 and the disc bottom seat 2, and the sample size is adjusted by the shrinkage gasket 7; the test probe chamber 5 is placed on the disc bottom seat 2, and the double-helix test probe is placed in the test probe chamber 5. The sample chamber 4 and the test probe chamber 5 are vertically distributed, and the double-helix test probe is placed between two identical and flat-surfaced rock samples; the fixing bolts 3 and nuts seal the high-pressure sealed chamber to achieve high-pressure sample measurement. There are 8 symmetric screw holes around the high-pressure sealed sample chamber, and a height-adjustable pressure interface 8 is provided in the Y-axis direction and is connected to the pressure unit, which can inject water, gas, etc. into the high-pressure sealed sample chamber and apply confining pressure to the formation pressure; the double-helix test probe is connected to the cable through the shrinkage joint 6, and the other end of the cable is connected to the planar heat source mainframe. The planar heat source mainframe applies an instantaneous heat pulse through the cable; the data acquisition and processing unit is respectively connected to the temperature control unit and the planar heat source mainframe, places the high-pressure sealed sample chamber in the temperature control unit, and the data acquisition and processing unit regulates the test temperature of the temperature control unit; the data acquisition and processing unit provides the test power and heating time for the double-helix test probe connected to the planar heat source mainframe. The planar heat source mainframe applies heat pulses of different times and intensities to the double-helix test probe. The data acquisition and processing unit measures the resistance value of the double-helix structure metal wire in real time, and obtains the thermal conductivity and thermal diffusivity of the medium by using the mathematical solution method of the heat conduction equation based on the relationship between the surface temperature increase value of the core and time.

[0109] The probe intersects the sample chamber perpendicularly. As Figure 7As shown in the figure, the outer layer of the probe is made of double-layer polyimide or other film materials as the protective layer, and the inner layer is a thin sheet with a continuous double-helix structure formed by etching a material with a linear temperature resistance coefficient - nickel conductive metal as the planar probe. It has two functions, namely, a heat source and a temperature sensor. Before the test, the sample to be measured is placed in the sample chamber, and the probe interface 9 is placed between two samples to be measured at a right angle intersection, forming a sample-probe-sample triple-layer structure. After the measurement starts, the probe generates heat and transfers it into the internal part of the sample to be measured. During the test, the probe outputs a constant current, and the probe generates a temperature rise of 2-5K within the effective test time. Since the probe is in direct contact with the sample, its heat will be conducted into the internal part of the sample to be measured, and the rate of heat dissipation of the probe will vary depending on the different thermal conductivities of the samples.

[0110] The thermal conductivity and thermal diffusivity of the medium are obtained by using the mathematical solution method of the heat conduction equation, including:

[0111] The calculation of the temperature increment and the characteristic time function should be determined according to formula (1):

[0112]

[0113] In the formula:

[0114] ΔΤ s (τ) is the function of the temperature increment on the sample surface changing with τ during the test process, with the unit of Kelvin (K);

[0115] P o The output power of the probe, with the unit of watt (W);

[0116] r is the outermost radius of the double-helix structure, with the unit of millimeter (mm);

[0117] λ is the thermal conductivity of the sample, with the unit of watt per meter per Kelvin (W / (m.K)); the dimensionless characteristic time function;

[0118] D(τ)D(T) should be calculated according to formula (2):

[0119]

[0120] In the formula:

[0121] m is the total number of turns of the double-helix structure;

[0122] The integration variable of the dimensionless characteristic time function;

[0123] J o The zero-order modified Bessel function;

[0124] In the above formula, τ should be calculated according to formula (3):

[0125]

[0126] In the formula:

[0127] t is the test moment, in seconds (s);

[0128] t c is the calibration time, in seconds (s);

[0129] r is the outermost radius of the double helix structure, in millimeters (mm);

[0130] a is the thermal diffusivity of the sample, in square millimeters per second (mm 2 / s);

[0131] Calculation of thermal diffusivity:

[0132] As known from formula (1), there is a linear relationship between ΔT S (τ) and D(τ). By taking the thermal diffusivity a and the calibration time t c as optimization variables for iterative calculations, D(τ) is calculated according to formulas (2) and (3) and made to have a strict linear correspondence with ΔT S (τ), and finally the value of the thermal diffusivity a is obtained;

[0133] Calculation of thermal conductivity:

[0134] By fitting the linear relationship between △T S (τ) and D(τ) by the least squares method, the slope of this formula is P in formula (1) O / (Π 3 / 2 γλ), and finally the thermal conductivity λ of the sample is obtained.

[0135] Example 2

[0136] A method for measuring the thermal conductivity, specific heat capacity, and thermal diffusivity of oil, water, oil-gas-water mixed systems, and multi-component, multi-phase, multi-size rocks in different saturation states under reservoir conditions by the plane heat source method includes the following steps ( Figure 3 ):

[0137] Step (1): Equipment startup: Turn on the plane heat source mainframe (11) and preheat for 20 minutes.

[0138] Step (2): Rock sample treatment: Ensure that the surface of the rock sample is smooth. For rock samples with uneven surfaces, they need to be polished with sandpaper; the flatness is less than 0.1 mm;

[0139] Step (3): Sample filling: Place two rock samples in the high-pressure sealed chamber (14) respectively, and select appropriate gaskets according to the size of the rock samples;

[0140] Step (4): Placement of test probe: The test probe is placed in the test probe chamber, and the double - helix probe is located exactly in the middle of the two rock samples; then it is clamped with screws and placed in the high - pressure sealed chamber;

[0141] Step (5): Setting of reservoir temperature: Place the high - pressure sealed chamber (14) in the temperature control unit (13), and set the reservoir temperature through the data acquisition and processing unit;

[0142] Step (6): Setting of test parameters: Set the pulse detection radius, test probe model, temperature, pulse power, and pulse time through the data acquisition and processing unit (12); the temperature in this step should be consistent with the temperature of the temperature control unit;

[0143] Step (7): Setting of test pressure: The pressure unit (15) is connected to the high - pressure sealed chamber (14). After the temperature control unit (13) reaches the set temperature, confining pressure can be applied to the formation pressure by means of water injection, gas injection, etc.;

[0144] Step (8): Stabilization of temperature field: The data acquisition and processing unit needs to be stable for more than 20 minutes, and the temperature shows a scatter distribution;

[0145] Step (9): Bridge balance: The planar heat source mainframe (11) balances the bridge. The voltage used for balancing the bridge should make the system current not greater than 1 mA, and the reading of the digital voltmeter of the bridge test system is zero after the bridge is balanced.

[0146] Step (10): Application of heat pulse: The planar heat source mainframe (11) applies a heat pulse. According to the total test time and output power, a constant direct current is applied to the probe to generate a heat pulse in the sample. During the test, the sliding contact of the potentiometer should not be adjusted.

[0147] Step (11): Data acquisition and processing: The data acquisition and processing unit (12) acquires the unbalanced voltage. During the total test time, scan and record the unbalanced voltage, that is, the potential change amount, at appropriate time intervals, and the number of acquisitions should be greater than 100 times.

[0148] Step (12): Verification of the validity of the measurement result: Judge the validity of the measurement result according to the relationship between the measurement time t, probe radius r, and thermal diffusivity α. αt / r 2 should be between 0.3 and 1.0. Otherwise, adjust the measurement time or output power and re - measure.

[0149] Step (13): Investigation of data precision: Under the same conditions, repeat steps 8 - 12 for two independent measurements. The relative deviation of the results should not be greater than 2%.

[0150] As Figure 8 shown, it is the circuit schematic diagram when Hot Disk works. The calculation method of thermal physical parameters is as follows:

[0151] When the probe is electrically heated, the calculation of the probe resistance is shown in formula (2.1).

[0152] R(t) = R 0 {1 + β[ΔT i (t) + ΔT s (t)]} (2.1)

[0153] The calculation of the thermal conductivity is shown in (2.2).

[0154]

[0155] The calculation of δ is shown in formula (2.3).

[0156]

[0157] The calculation of D(δ) is shown in formula (2.4):

[0158]

[0159] In formulas (2.1) - (2.4):

[0160] R(t) —— The resistance of the probe at time t;

[0161] R 0 —— The initial resistance of the probe;

[0162] β —— The temperature coefficient of resistivity (TCR) of the probe. The resistance temperature coefficient of the nickel probe is shown in Table 1

[0163] ΔT i (t) —— The temperature difference across the insulating thin layer of the probe;

[0164] ΔT s (t) —— The temperature difference on the surface of the sample;

[0165] q —— The output power;

[0166] r —— The radius of the outermost layer of the double - helix structure of the probe;

[0167] λ —— The thermal conductivity;

[0168] D(δ) —— The characteristic time function;

[0169] t —— The measurement time;

[0170] α —— The thermal diffusivity;

[0171] n —— The total number of turns of the double - helix structure of the probe;

[0172] σ —— The integration variable of the dimensionless characteristic time function;

[0173] J0 —— Modified Bessel function of the zero order;

[0174] l 1 and l 2 —— Summation variables not greater than the total number of loops of the double helix structure.

[0175] Table 1 Resistance Temperature Coefficient Table (TCR) of Nickel Probes at Different Temperatures

[0176]

[0177]

[0178] Step (14): Data self-check: Before measuring each batch of samples, use a standard block for self-check. The relative error of the thermal conductivity measurement result should be less than 3%, and the relative error of the thermal diffusivity measurement result should be less than 5%.

[0179] Example 3

[0180] In a specific embodiment of applying the present invention, the multi-component and multi-phase thermal property testing method is investigated. The selected core is gray-green mudstone, about 5 cm long and 2.5 cm wide. The initial resistance R0 of the probe in the high-pressure sealed chamber is the same as the initial resistance R of the conventional test probe. 0 The results of the thermal property parameters at 25°C and atmospheric pressure are shown in Table 2, indicating that the test values in the high-pressure sealed chamber of the multi-component and multi-phase thermal property testing system of the present invention are accurate and reliable.

[0181] Table 2 Multi-Component and Multi-Phase Thermal Property Test Table Based on the Transient Plane Heat Source Method

[0182]

[0183] To further study the influence of pressure on the thermal conductivity coefficient and specific heat, at 25°C, the core is placed in a high-pressure sealed chamber and filled with nitrogen. Pressures of 0 Mpa, 2 Mpa, 4 Mpa, 5 Mpa, 7 Mpa, and 9 Mpa are applied in sequence. The results are shown in Figures 4 - 6 . As the pressure increases, the thermal conductivity coefficient of the core increases, and the specific heat coefficient decreases. The present invention realizes the measurement of the thermal conductivity, specific heat capacity, and thermal diffusivity of multi-component and multi-phase rocks in a reservoir condition.

[0184] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0185] Except for the technical features described in the specification, all are well-known technologies to those skilled in the art.

Claims

1. A multi-component and multi-phase thermal property testing system based on the transient plane heat source method, characterized in that, the multi-component and multi-phase thermal property testing system based on the transient plane heat source method includes a plane heat source mainframe, a data acquisition and processing unit, a pressure unit, a high-pressure sealed chamber, and a temperature control unit. The high-pressure sealed chamber is located in the temperature control unit; the temperature control unit is connected to the data acquisition and processing unit, and the data acquisition and processing unit regulates the test temperature of the temperature control unit; the pressure unit is connected to the high-pressure sealed chamber to inject a fluid into the high-pressure sealed chamber and apply a confining pressure to the formation pressure; the plane heat source mainframe is connected to the data acquisition and processing unit and the high-pressure sealed chamber, and the plane heat source mainframe applies an instantaneous heat pulse to the high-pressure sealed chamber under the control of the data acquisition and processing unit.

2. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 1, characterized in that, the high-pressure sealed chamber includes a disc top seat, a disc bottom seat, two sample chambers, a test probe chamber, and a double helix test probe. The two sample chambers are distributed on the disc top seat and the disc bottom seat; the test probe chamber is placed on the disc bottom seat, and the double helix test probe is placed in the test probe chamber. The double helix test probe is placed between two identical and flat-surfaced rock samples; the plane heat source mainframe applies heat pulses with different times and intensities to the double helix test probe.

3. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 2, characterized in that, the high-pressure sealed chamber further includes a shrinkage gasket. The two sample chambers are distributed on the disc top seat and the disc bottom seat, and the sample size is adjusted by the shrinkage gasket.

4. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 2, characterized in that, the two sample chambers and the test probe chamber are vertically distributed.

5. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 2, characterized in that, the high-pressure sealed chamber further includes a pressure interface. There are 8 symmetric screw holes around the high-pressure sealed sample chamber, and the height-adjustable pressure interface is provided in the Y-axis direction and is connected to the pressure unit, and can inject fluid into the high-pressure sealed sample chamber and apply a confining pressure to the formation pressure.

6. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 2, characterized in that, the high-pressure sealed chamber further includes a shrinkage joint. The double helix test probe is connected to a cable through the shrinkage joint, and the other end of the cable is connected to the plane heat source mainframe. The plane heat source mainframe applies an instantaneous heat pulse through the cable.

7. The multi-component and multi-phase thermal property testing system based on the transient plane heat source method according to claim 6, characterized in that, The data acquisition and processing unit provides test power and heating time for the double - helix test probe connected to the planar heat source host. The planar heat source host applies thermal pulses of different durations and intensities to the double - helix test probe. The data acquisition and processing unit measures the resistance value of the metal wire of the double - helix structure of the double - helix test probe in real time, and obtains the thermal conductivity and thermal diffusivity of the medium by using the mathematical solution method of the heat conduction equation based on the relationship between the temperature increase value on the core surface and time.

8. The multi - component and multi - phase thermal property test system based on the transient plane heat source method according to claim 7, characterized in that, obtaining the thermal conductivity and thermal diffusivity of the medium by using the mathematical solution method of the heat conduction equation includes: The calculation of the temperature increase value and the characteristic time function shall be determined according to formula (1): where: ΔΤ s (τ) is the function of the surface temperature increment of the sample varying with τ during the test, with the unit of Kelvin (K); P o Output power of the probe, unit: watt (W); r is the outermost radius of the double - helix structure, in millimeters (mm); λ is the thermal conductivity of the sample, in watts per meter per kelvin (W / (m·K)); the dimensionless characteristic time function; D(τ)D(T) shall be calculated according to formula (2): where: m is the total number of turns of the double - helix structure; the integration variable of the dimensionless characteristic time function; J o zero-order modified Bessel function; τ in the above formula shall be calculated according to formula (3): where: t is the test time, in seconds (s); t c Calibration time, unit is second (s); r is the outermost radius of the double - helix structure, in millimeters (mm); The thermal diffusivity of a sample, in square millimeters per second (mm 2 / s); Calculation of the thermal diffusivity: As known from Equation (1), ΔT S There is a linear relationship between S (τ) and D(τ). By taking the thermal diffusivity a and the correction time t c as optimization variables for iterative calculations, D(τ) is calculated according to Equations (2) and (3) to make it have a strict linear correspondence with ΔT S (τ), and finally the value of the thermal diffusivity a is obtained; Calculation of the thermal conductivity: Fitting △T by the least squares method S (τ) and the linear relationship of D(τ), and the slope of this formula is P in formula (1) O / (Π 3 / 2 γλ), and finally obtain the thermal conductivity λ of the sample.

9. The multi - component and multi - phase thermal property test method based on the transient plane heat source method, characterized in that, the multi - component and multi - phase thermal property test method based on the transient plane heat source method adopts the multi - component and multi - phase thermal property test system based on the transient plane heat source method described in claim 1, and includes: Step 1, filling the sample and placing the probe; Step 2, setting the reservoir temperature and setting the test parameters; Step 3, setting the test pressure; Step 4, stabilizing the temperature field; Step 5, balancing the bridge and applying a thermal pulse; Step 6, performing data acquisition and processing; Step 7, verifying the validity of the measurement results.

10. The multi - component and multi - phase thermal property test method based on the transient plane heat source method according to claim 9, characterized in that, the multi - component and multi - phase thermal property test method based on the transient plane heat source method further includes, before step 1, turning on the planar heat source host and preheating for 20 minutes; performing rock sample treatment to ensure the smoothness of the rock sample surface. For rock samples with uneven surfaces, they need to be polished with sandpaper.

11. The multi - component and multi - phase thermal property test method based on the transient plane heat source method according to claim 9, characterized in that, In step 1, place two rock samples in the high - pressure sealed chamber respectively, and select appropriate gaskets according to the rock sample size; place the double - helix test probe in the test probe chamber, and the double - helix test probe is clamped in the middle of the two rock samples.

12. The multi - component and multi - phase thermal property test method based on the transient plane heat source method according to claim 9, characterized in that, In step 2, place the high - pressure sealed chamber in the temperature control unit, and set the reservoir temperature through the data acquisition and processing unit; set the pulse detection radius, double - helix test probe model, temperature, pulse power and pulse time through the data acquisition and processing unit.

13. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, in step 3, the pressure unit is connected to the high-pressure sealed chamber. After the temperature control unit reaches the set temperature, confining pressure is applied to the formation pressure by injecting water and gas.

14. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, in step 4, the data acquisition and processing unit needs to be stable for more than 20 minutes, and the internal temperature of the sample-double helix test probe-sample triple-layer structure shows a scatter distribution.

15. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, in step 5, the plane heat source mainframe balances the Wheatstone bridge. The voltage used for the Wheatstone bridge should ensure that the system current does not exceed 1 mA, and the digital voltmeter reading of the Wheatstone bridge test system is zero after the bridge is balanced; the plane heat source mainframe applies a heat pulse. According to the total test time and output power, a constant direct current is applied to the probe to generate a heat pulse in the sample, and the sliding contact of the potentiometer should not be adjusted during the test process.

16. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, in step 6, the data acquisition and processing unit collects the unbalanced voltage. During the total test time, the unbalanced voltage, that is, the potential change amount, is scanned and recorded at appropriate time intervals, and the number of acquisitions should be greater than 100 times.

17. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, In step 7, the validity of the measurement result is judged according to the relationship among the measurement time t, the probe radius r, and the thermal diffusivity α, where αt / r 2 should be between 0.3 and 1.0; otherwise, the measurement time or the output power should be adjusted and the measurement should be repeated.

18. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 9, characterized in that, the multi-component and multi-phase thermal property testing method based on the transient plane heat source method further includes, after step 7, step 8, performing data precision examination. Under the same conditions, steps 4 to 7 are repeated for two independent determinations; the relative deviation of the results should not be greater than 2%.

19. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 18, characterized in that, in step 8, the calculation method of the thermal property parameters is as follows: When the probe is electrically heated, the calculation of the probe resistance is shown in formula (2.1): R(t) = R 0 {1 + β[ΔT i (t) + ΔT s (t)]} (2.1) The calculation of the thermal conductivity is shown in (2.2): The calculation of δ is shown in formula (2.3): The calculation of D(δ) is shown in formula (2.4): In formulas (2.1) to (2.4): R(t) - the resistance of the probe at time t; R 0 —— Initial resistance of the probe; β - the temperature coefficient TCR of the probe resistivity; ΔT i (t)——temperature difference of the insulating thin layer of the probe; ΔT s (t)——the temperature difference on the surface of the sample; q - the output power; r - the radius of the outermost layer of the probe double helix structure; λ - the thermal conductivity; D(δ) - the characteristic time function; t - the measurement time; α - the thermal diffusivity; n - the total number of turns of the probe double helix structure; σ - the integration variable of the dimensionless characteristic time function; J 0 —— zero-order modified Bessel function; l 1 、l 2 —— The summation variable not greater than the total number of turns of the double helix structure.

20. The multi-component and multi-phase thermal property testing method based on the transient plane heat source method according to claim 18, characterized in that, The multi-component and multi-phase thermal property testing method based on the transient plane heat source method further includes, after step 8, performing data self-check. Before measuring each batch of samples, use a standard block for self-check. The relative error of the measured thermal conductivity should be less than 3%, and the relative error of the measured thermal diffusivity should be less than 5%.

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