Evaluation method for uniform heating of rock sample

Abstract

The invention relates to a method for evaluating uniform heating of a rock sample, which comprises the following steps of: controlling the relationship between the surface temperature of a sample and the center temperature of the sample by using the surface temperature, the heating rate, the heat conductivity of the sample, the equivalent diameter of the sample and the porosity of the sample in the heating process of the rock sample, and establishing a relational expression between the center temperature and the surface temperature of the rock sample; the matching relation between the equivalent diameter and the heating rate of uniform heating of the rock is determined, so that uniform heating of the rock sample is realized, a basis is provided for improving the experiment efficiency and the experiment result reliability, and the method has important significance for accurately evaluating the oil gas output under the condition of determining the temperature and the heating rate in the shale in-situ heating process.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration and development, and in particular to a method for evaluating uniform heating of a rock sample. Background Art

[0002] In order to study hydrocarbon generation in source rocks or changes in reservoir properties of rocks with heating temperature during oil and gas exploration and development, thermal simulation experiments need to be conducted in the laboratory. Since the hydrocarbon generation rate, amount and quality of organic matter in source rocks are closely related to temperature, and the pores generated by the decomposition of organic matter or inorganic minerals in rocks are closely related to temperature, it is necessary to ensure the consistency of the internal and surface temperatures of the samples during the thermal simulation process, that is, to heat the samples uniformly to ensure the reliability of the relationship between the experimental results and the temperature; at the same time, in the process of evaluating the amount of oil and gas produced by in-situ heating of shale, choosing the appropriate equivalent sample diameter and heating rate is the key to ensuring the relative consistency of the produced oil products and improving the accuracy of oil and gas evaluation.

[0003] CN 109613213A discloses a multifunctional hydrocarbon generation and rock formation high temperature and high pressure simulation experimental device and a method for using the same. The device comprises a hydrocarbon generation reaction and fluid generation system for a source rock, an auxiliary system, a hydrocarbon expulsion reaction and a hydrocarbon source fluid transfer system, a hydrocarbon source fluid-rock interaction system and a product separation and collection system. The fluid of the hydrocarbon generation reaction and fluid generation system for a source rock is released into the hydrocarbon expulsion reaction and hydrocarbon source fluid transfer system, and then the hydrocarbon source fluid is injected into a reservoir rock sample in a core holder. A heating and pressurizing device is started to allow the fluid and rock to react at a set temperature, pressure and time.

[0004] CN 114460122A discloses a method for selecting rock chip samples for thermal simulation experiments of hydrocarbon source rocks, comprising the following steps: designing target sampling points for thermal simulation experiments, sampling and packaging with paper bags, processing rock chip samples, rock pyrolysis analysis, judging the results of the rock pyrolysis analysis of the rock chip samples, total organic carbon analysis, judging the results of the total organic carbon analysis of the rock chip samples and water washing, and finally putting the obtained rock chip samples into sample bags.

[0005] In the above thermal simulation technologies, the samples are crushed into powder and heated to achieve uniform heating of the samples. However, when the samples are crushed into powder, the retained oil in the samples will be lost. In addition, when studying the physical properties of shale reservoirs, it is difficult to accurately determine the physical properties of the reservoirs by crushing the samples into powder. There is no method or technology in the prior art to determine the relationship between sample size and heating rate, which restricts the reliability or experimental speed of thermal simulation experiments, and also restricts the reasonable configuration of sample particle size and heating rate in shale in-situ heating simulation experiments, thereby affecting the accuracy of the evaluation.

[0006] In view of the shortcomings of the existing technology, there is an urgent need to provide an evaluation method that can achieve uniform heating of samples, improve efficiency and reliability of experimental results, and improve the accuracy of oil and gas evaluation. Summary of the invention

[0007] The purpose of the present invention is to provide an evaluation method for uniform heating of rock samples. By establishing a matching relationship between equivalent diameter and heating rate, uniform heating of rock samples is achieved, which provides a basis for improving experimental efficiency and reliability of experimental results and improving accuracy of oil and gas evaluation.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for evaluating uniform heating of a rock sample, the method comprising the following steps:

[0010] (1) The heating rate and thermal conductivity are fixed, and the surface temperature and center temperature of rock samples with different equivalent diameters are measured to obtain the relationship between the center temperature and surface temperature of the rock samples;

[0011] (2) establishing a relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample obtained in step (1) and the equivalent diameter of the rock sample;

[0012] (3) adjusting the heating rate to obtain the empirical coefficient b in the relationship between the empirical coefficient a in step (2) and the equivalent diameter of the rock sample at different heating rates, and then establishing a relationship between the empirical coefficient b and the heating rate;

[0013] (4) adjusting the thermal conductivity to obtain the empirical coefficient b described in step (3) under different thermal conductivities, and establishing a relationship between the thermal conductivity and the empirical coefficient b;

[0014] (5) adjusting the porosity of the rock sample to obtain a correction coefficient b' of the empirical coefficient b in step (3) at different porosities, and establishing a relationship between the porosity and the correction coefficient b';

[0015] (6) According to steps (1) to (5), the relationship between the center temperature and the surface temperature of the rock sample is integrated to obtain the matching relationship between the equivalent diameter of the rock sample and the heating rate, thereby achieving uniform heating of the rock sample.

[0016] The evaluation method provided by the present invention utilizes the sample surface temperature, heating rate, sample thermal conductivity, sample equivalent diameter, and sample porosity during the rock sample heating process to control the relationship between the sample surface temperature and the sample center temperature, establishes a relationship between the rock sample center temperature and the surface temperature, and realizes the evaluation of the matching relationship between the equivalent diameter and the heating rate of uniformly heated rocks, determines the maximum heating rate required for a fixed equivalent diameter when the rock is uniformly heated, or the maximum equivalent diameter required for a fixed heating rate when the rock is uniformly heated; sets the maximum heating rate according to the equivalent diameter of the rock sample or determines the maximum equivalent diameter of the uniformly heated rock sample according to the heating rate, thereby realizing optimal uniform heating, providing a basis for improving experimental efficiency and the reliability of experimental results, and is of great significance for accurately evaluating the oil and gas production under the conditions of determined temperature and heating rate during the in-situ heating of shale.

[0017] Preferably, the relationship between the center temperature and the surface temperature of the rock sample in step (1) is as follows:

[0018] T c =T f -a

[0019] Where: T c is the center temperature of the rock sample; T f is the surface temperature of the rock sample; a is the empirical coefficient.

[0020] Preferably, the relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample in step (2) and the equivalent diameter of the rock sample is as follows:

[0021] a=b×D 2

[0022] Where: b is the empirical coefficient; D is the equivalent diameter of the rock sample.

[0023] Preferably, the relationship between the empirical coefficient b and the heating rate in step (3) is as follows:

[0024] b=c×r

[0025] Where: b is the empirical coefficient; r is the heating rate.

[0026] Preferably, the relationship between the thermal conductivity and the empirical coefficient b in step (4) is as follows:

[0027] b=c×λ d

[0028] Where: c and d are empirical coefficients; λ is thermal conductivity.

[0029] Preferably, the relationship between the porosity and the correction coefficient b' in step (5) is as follows:

[0030] b'=e×Фf

[0031] Where: b' is the correction coefficient of the empirical coefficient b; e and f are empirical coefficients; Ф is the porosity.

[0032] Preferably, the relationship between the center temperature and the surface temperature of the integrated rock sample in step (6) is as follows:

[0033] T c =T f -g×r×D 2 ×λ d × f

[0034] Where: T c is the center temperature of the rock sample; T f is the surface temperature of the rock sample; r is the heating rate; λ is the thermal conductivity; D is the equivalent diameter of the rock sample; Ф is the porosity; g, d, f are empirical coefficients.

[0035] Preferably, the determination of the surface temperature and the center temperature of the rock sample in step (1) is carried out in a sample temperature measuring device, which includes a heater, which is sleeved on the outside of the rock sample; a temperature controller is provided on the side wall of the heater, and the bottom of the heater is connected to a product collector through a product discharge pipe; a temperature measuring device is provided at the inner center of the rock sample, and the temperature measuring device is connected to a temperature receiver.

[0036] The temperature controller is used to control the temperature and heating rate of the heater to keep the temperature at different positions on the sample surface consistent.

[0037] Preferably, the connecting line between the temperature measuring device and the temperature receiver is covered with a heat insulating sheath.

[0038] The heat-insulating sheath is used to insulate the connection line between the temperature receiver and the temperature measuring device, so as to ensure that the connection line will not affect the temperature of the temperature measuring device.

[0039] The temperature receiver is used to receive and record the temperature of the temperature measuring device, and can perform temperature recording in real time.

[0040] Preferably, the temperature measurer comprises a thermocouple or an optical fiber.

[0041] Preferably, a heat-insulating layer is provided outside the heater.

[0042] The heater is used to heat the rock sample in all directions. A heat-insulating layer is arranged outside the heater to reduce heat loss and maintain the temperature of the heater.

[0043] The product discharge pipe is used for timely discharge of the product of the rock sample during the heating process, so as to prevent the sealing damage or uneven heating caused by the increase in pressure due to hydrocarbon generation of organic matter or the increase in pressure due to decomposition of inorganic matter during the heating process.

[0044] The product collector is used to collect outputs during the heating process of rock samples, which can be used for product measurement or component analysis.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] The evaluation method provided by the present invention utilizes the sample surface temperature, heating rate, sample thermal conductivity, sample equivalent diameter, and sample porosity during the rock sample heating process to control the relationship between the sample surface temperature and the sample center temperature, establishes a relationship between the rock sample center temperature and the surface temperature, and realizes the evaluation of the matching relationship between the equivalent diameter and the heating rate of uniformly heated rocks, determines the maximum heating rate required for a fixed equivalent diameter when the rock is uniformly heated, or the maximum equivalent diameter required for a fixed heating rate when the rock is uniformly heated; sets the maximum heating rate according to the equivalent diameter of the rock sample or determines the maximum equivalent diameter of the uniformly heated rock sample according to the heating rate, thereby realizing optimal uniform heating, providing a basis for improving experimental efficiency and the reliability of experimental results, and is of great significance for accurately evaluating the oil and gas production under the conditions of determined temperature and heating rate during the in-situ heating of shale. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a flow chart of a method for evaluating uniform heating of a rock sample provided by an embodiment of the present invention;

[0048] Figure 2 The graph of the relationship between the center temperature and the surface temperature of the rock samples provided by the embodiment of the present invention has a thermal conductivity of 1.8 W / (mk), a heating rate of 2° C. / hr, and equivalent diameters of 10 cm, 30 cm, and 60 cm, respectively;

[0049] Figure 3 The graph of the relationship between the center temperature and the surface temperature of the rock samples provided by the embodiment of the present invention has a thermal conductivity of 1.8 W / (mk), a heating rate of 5°C / hr, and equivalent diameters of 10 cm, 30 cm, and 60 cm respectively;

[0050] Figure 4 The graph of the relationship between the center temperature and the surface temperature of the rock samples provided by the embodiment of the present invention, with a thermal conductivity of 1.8 W / (mk), a heating rate of 10° C. / hr, and equivalent diameters of 10 cm, 30 cm, and 60 cm respectively;

[0051] Figure 5 It is a relationship diagram between the empirical coefficient a and the equivalent diameter of the rock sample under the condition of a heating rate of 2°C / hr provided in an embodiment of the present invention;

[0052] Figure 6 It is a relationship diagram between the empirical coefficient a and the equivalent diameter of the rock sample under the condition of a heating rate of 5°C / hr provided in an embodiment of the present invention;

[0053] Figure 7 It is a relationship diagram between the empirical coefficient a and the equivalent diameter of the rock sample under the condition of a heating rate of 10°C / hr provided in an embodiment of the present invention;

[0054] Figure 8 is a relationship diagram between the empirical coefficient b and the heating rate provided in an embodiment of the present invention;

[0055] Fig. 9 is a relationship diagram between the empirical coefficient b and thermal conductivity provided by an embodiment of the present invention;

[0056] Fig.10 is a relationship diagram between porosity and correction coefficient b' provided in an embodiment of the present invention;

[0057] Fig.11 is a graph showing the relationship between the center temperature of a rock sample and the heating rate provided by an embodiment of the present invention;

[0058] Fig.12 is a schematic structural diagram of a sample temperature measurement device provided by an embodiment of the present invention;

[0059] Among them: 1, heater; 2, rock sample; 3, temperature controller; 4, product discharge pipe; 5, product collector; 6, thermocouple; 7, insulation jacket; 8, temperature receiver. DETAILED DESCRIPTION

[0060] The technical scheme of the present invention is further illustrated by specific examples below. Those skilled in the art should understand that the examples are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0061] This embodiment provides a method for evaluating uniform heating of a rock sample. The flow chart of the evaluation method is as follows: Figure 1 As shown, the evaluation method comprises the following steps:

[0062] (1) The heating rate and thermal conductivity are fixed, and the surface temperature and center temperature of rock samples with different equivalent diameters are measured to obtain the relationship between the center temperature and surface temperature of the rock samples;

[0063] (2) establishing a relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample obtained in step (1) and the equivalent diameter of the rock sample;

[0064] (3) adjusting the heating rate to obtain the empirical coefficient b in the relationship between the empirical coefficient a in step (2) and the equivalent diameter of the rock sample at different heating rates, and then establishing a relationship between the empirical coefficient b and the heating rate;

[0065] (4) adjusting the thermal conductivity to obtain the empirical coefficient b described in step (3) under different thermal conductivities, and establishing a relationship between the thermal conductivity and the empirical coefficient b;

[0066] (5) adjusting the porosity of the rock sample to obtain a correction coefficient b' of the empirical coefficient b in step (3) at different porosities, and establishing a relationship between the porosity and the correction coefficient b';

[0067] (6) According to steps (1) to (5), the relationship between the center temperature and the surface temperature of the rock sample is integrated to obtain the matching relationship between the equivalent diameter of the rock sample and the heating rate, thereby achieving uniform heating of the rock sample.

[0068] In combination with the thermal simulation experiment, each step involved in the above embodiment is described in detail as follows in combination with the accompanying drawings:

[0069] Step (1): The thermal conductivity is fixed at 1.8 W / (mk), the heating rate is 2°C / hr, and the center temperature and surface temperature of rock samples with equivalent diameters of 10 cm, 30 cm, and 60 cm are measured. The relationship between the center temperature and surface temperature of the rock samples is shown in the figure below: Figure 2 As shown;

[0070] The thermal conductivity is fixed at 1.8W / (mk), the heating rate is 5℃ / hr, and the center temperature and surface temperature of rock samples with equivalent diameters of 10cm, 30cm, and 60cm are measured. The relationship between the center temperature and surface temperature of the rock sample is shown in the figure below: Figure 3 As shown;

[0071] The thermal conductivity is fixed at 1.8W / (mk), the heating rate is 10℃ / hr, and the center temperature and surface temperature of rock samples with equivalent diameters of 10cm, 30cm, and 60cm are measured. The relationship between the center temperature and surface temperature of the rock sample is shown in the figure below: Figure 4 shown.

[0072] According to the surface temperature and center temperature data of rock samples with the same heating rate, thermal conductivity and different equivalent diameters, the relationship between the center temperature and surface temperature of the rock sample (1) is obtained as follows:

[0073] T c =T f -a (1)

[0074] In formula (1): T c is the center temperature of the rock sample, °C; T fis the surface temperature of the rock sample, ℃; a is the empirical coefficient, dimensionless.

[0075] The empirical coefficient a for the equivalent diameters of different rock samples and at different heating rates was calculated, and the results are shown in Table 1.

[0076] Table 1

[0077]

[0078] Step (2): The heating rate is fixed at 2°C / hr, and the relationship between the empirical coefficient a and the equivalent diameter of the rock sample is obtained as follows: Figure 5 As shown;

[0079] The heating rate is fixed at 5℃ / hr, and the relationship between the empirical coefficient a and the equivalent diameter of the rock sample is shown in the figure below: Figure 6 As shown;

[0080] The heating rate is fixed at 10℃ / hr, and the relationship between the empirical coefficient a and the equivalent diameter of the rock sample is shown in the figure below: Figure 7 shown.

[0081] The relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample obtained in step (1) and the equivalent diameter of the rock sample is as follows:

[0082] a=b×D 2 (2)

[0083] In formula (2), b is the empirical coefficient, dimensionless; D is the equivalent diameter of the sample, cm.

[0084] Step (3): The heating rates were adjusted to 2°C / hr, 5°C / hr, and 10°C / hr, respectively, to obtain the empirical coefficient b in the relationship between the empirical coefficient a in step (2) and the equivalent diameter of the rock sample at different heating rates. The results are shown in Table 2.

[0085] Table 2

[0086] Heating rate (℃ / hr) b 2 0.018519 5 0.046296 10 0.092593

[0087] According to the data in Table 2, a relationship diagram is drawn. Under the condition of thermal conductivity of 1.8W / (mk), the equivalent diameters of rock samples are 10cm, 30cm, and 60cm, and the heating rates are 2℃ / hr, 5℃ / hr, and 10℃ / hr, respectively. The relationship diagram between the empirical coefficient b and the heating rate is shown in the figure below: Figure 8 shown.

[0088] Then the relationship between the empirical coefficient b and the heating rate is established as follows;

[0089] b=c×r (3)

[0090] In formula (3), b is the empirical coefficient, dimensionless; r is the heating rate, °C / hr.

[0091] Step (4): When other conditions are the same and only the thermal conductivity is changed, experiments are carried out on rock samples with different thermal conductivities, different equivalent diameters, and different combinations of heating rates to obtain the empirical coefficient b described in step (3) when the thermal conductivity is 1.5 W / (mk), 1.8 W / (mk), 2.2 W / (mk), 2.5 W / (mk), and 2.8 W / (mk). The results are shown in Table 3.

[0092] Table 3

[0093]

[0094]

[0095] According to the data in Table 3, a relationship diagram is drawn. Under the conditions of thermal conductivity of 1.5W / (mk), 1.8W / (mk), 2.2W / (mk), 2.5W / (mk), and 2.8W / (mk), the relationship diagram between the empirical coefficient b and thermal conductivity is obtained as shown in Fig. 9 shown.

[0096] Then the relationship between thermal conductivity and empirical coefficient b is established as follows:

[0097] b=c×λ d (4)

[0098] In formula (4), c and d are empirical coefficients, dimensionless, 0.0169 and -1.027 respectively; λ is thermal conductivity, W / (mk).

[0099] Step (5): When other conditions are the same and only the porosity is changed, rock sample experiments with a thermal conductivity of 1.8 W / (mk), different equivalent diameters, different heating rates, and porosity combinations are carried out to obtain the empirical coefficient b. The correction coefficient b' of the empirical coefficient b described in step (3) is obtained by comparing it with the empirical coefficient b without considering the influence of porosity to obtain the correction coefficient b' under the conditions of porosity of 1.602%, 2.413%, 3.109%, and 4.124%, respectively. The results are shown in Table 4.

[0100] Table 4

[0101] Porosity(%) b’ 1.602 0.97645 2.413 0.95536 3.109 0.94526 4.124 0.93267

[0102] According to the data in Table 4, a relationship diagram is drawn to obtain the relationship diagram between porosity and correction coefficient b' as shown in Fig.10 shown.

[0103] Then the relationship between porosity and correction coefficient b' is established as follows:

[0104] b'=e×Ф f (5)

[0105] In formula (5), b' is the correction coefficient of the empirical coefficient b, dimensionless; e and f are empirical coefficients, dimensionless, 0.9982 and -0.048224 respectively; Ф is the porosity, %.

[0106] Step (6): Based on steps (1) to (5), the relationship between the center temperature and the surface temperature of the integrated rock sample is as follows:

[0107] T c =T f -g×r×D 2 ×λ d × f (6)

[0108] In formula (6): T c is the center temperature of the rock sample, °C; T f is the surface temperature of the rock sample, ℃; r is the heating rate, ℃ / hr; λ is the thermal conductivity, W / (mk); D is the equivalent diameter of the rock sample, cm; Ф is the porosity, %; g, d, f are empirical coefficients, dimensionless, which are 0.01687, -1.027, and -0.048224, respectively.

[0109] When the thermal conductivity is 1.8 W / (mk), the porosity is 2.413%, the equivalent diameters of the rock samples are 0.01 cm, 0.1 cm, 1 cm, 10 cm, 20 cm, 50 cm, and 100 cm, respectively, the heating rates are 0.001 °C / hr, 0.01 °C / hr, 0.1 °C / hr, 1 °C / hr, 10 °C / hr, 100 °C / hr, and 1000 °C / hr, respectively, and the surface temperature of the rock sample is 425 °C, the center temperature of the rock sample is calculated using formula (6), and the relationship between the center temperature of the rock sample and the heating rate is obtained as shown in the figure: Fig.11 As shown, the matching relationship between the equivalent diameter of the rock sample and the heating rate can be obtained: in this embodiment, when the equivalent diameter of the rock sample is less than 0.1 cm and the heating rate is less than 1000°C / hr, or the equivalent diameter of the rock sample is 1 cm and the heating rate is less than 100°C / hr, or the equivalent diameter of the rock sample is 10 cm and the heating rate is less than 1°C / hr, or the equivalent diameter of the rock sample is 20 cm and the heating rate is less than 0.1°C / hr, or the equivalent diameter of the rock sample is 50 cm and the heating rate is less than 0.01°C / hr, or the equivalent diameter of the rock sample is 100 cm and the heating rate is less than 0.001°C / hr, the center temperature of the rock sample is consistent with the surface temperature, and uniform heating of the rock sample can be achieved at this time.

[0110] The determination of the surface temperature and the center temperature of the rock sample in step (1) is carried out in a sample temperature measuring device. The schematic diagram of the structure of the sample temperature measuring device is as follows: Fig.12 As shown, the sample temperature measuring device includes a heater 1, which is sleeved on the outside of a rock sample 2 and is used to heat the rock sample 2 in all directions; a temperature controller 3 is provided on the side wall of the heater 1, which is used to control the temperature and heating rate of the heater 1 to keep the temperature of different positions on the surface of the rock sample 2 consistent; the bottom of the heater 1 is connected to a product collector 5 through a product discharge pipe 4, and the product discharge pipe 4 is used for timely discharge of the product of the rock sample 2 during the heating process to prevent the sealing from being damaged or increased due to the increase in pressure caused by the generation of hydrocarbons by organic matter or the decomposition of inorganic matter during the heating process. The heat is uneven, and the product collector 5 is used to collect the output during the heating process of the rock sample 2, which can be used for product measurement or component analysis; the outside of the heater 1 is provided with an insulation layer to reduce heat loss and maintain the temperature of the heater 1; a thermocouple 6 is provided at the inner center of the rock sample 2, and the thermocouple 6 is connected to a temperature receiver 8 through a connecting line covered with an insulating sheath 7, and the insulating sheath is used to insulate the connecting line between the temperature receiver 8 and the thermocouple 6 to ensure that the connecting line will not affect the temperature of the thermocouple, and the temperature receiver 8 is used to receive and record the temperature of the thermocouple 6 in real time.

[0111] In summary, the evaluation method provided by the present invention utilizes the sample surface temperature, heating rate, sample thermal conductivity, sample equivalent diameter, and sample porosity during the heating process of the rock sample to control the relationship between the sample surface temperature and the sample center temperature, establishes a relationship between the rock sample center temperature and the surface temperature, and realizes the evaluation of the matching relationship between the equivalent diameter and the heating rate of uniformly heated rock, determines the maximum heating rate required for a fixed equivalent diameter when the rock is uniformly heated, or the maximum equivalent diameter required for a fixed heating rate when the rock is uniformly heated; sets the maximum heating rate according to the equivalent diameter of the rock sample or determines the maximum equivalent diameter of the uniformly heated rock sample according to the heating rate, thereby achieving optimal uniform heating, providing a basis for improving experimental efficiency and the reliability of experimental results, and is of great significance for accurately evaluating the oil and gas production under the conditions of determined temperature and heating rate during the in-situ heating of shale.

[0112] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A method for evaluating uniform heating of rock samples, characterized in that: The evaluation method comprises the following steps: (1) The heating rate and thermal conductivity are fixed, and the surface temperature and center temperature of rock samples with different equivalent diameters are measured to obtain the relationship between the center temperature and surface temperature of the rock samples; (2) establishing a relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample obtained in step (1) and the equivalent diameter of the rock sample; (3) adjusting the heating rate to obtain the empirical coefficient b in the relationship between the empirical coefficient a in step (2) and the equivalent diameter of the rock sample at different heating rates, and then establishing a relationship between the empirical coefficient b and the heating rate; (4) adjusting the thermal conductivity to obtain the empirical coefficient b described in step (3) under different thermal conductivities, and establishing a relationship between the thermal conductivity and the empirical coefficient b; (5) adjusting the porosity of the rock sample to obtain a correction coefficient b' of the empirical coefficient b in step (3) at different porosities, and establishing a relationship between the porosity and the correction coefficient b'; (6) According to steps (1) to (5), the relationship between the center temperature and the surface temperature of the rock sample is integrated to obtain the matching relationship between the equivalent diameter of the rock sample and the heating rate, thereby achieving uniform heating of the rock sample.

2. The evaluation method according to claim 1, characterized in that: The relationship between the center temperature and the surface temperature of the rock sample in step (1) is as follows: T c =T f -a Where: T c is the center temperature of the rock sample; T f is the surface temperature of the rock sample; a is the empirical coefficient.

3. The evaluation method according to claim 2, characterized in that: The relationship between the empirical coefficient a in the relationship between the center temperature of the rock sample and the surface temperature of the sample in step (2) and the equivalent diameter of the rock sample is as follows: a=b×D 2 Where: b is the empirical coefficient; D is the equivalent diameter of the rock sample.

4. The evaluation method according to claim 3, characterized in that: The relationship between the empirical coefficient b and the heating rate in step (3) is as follows: b=c×r Where: b is the empirical coefficient; r is the heating rate.

5. The evaluation method according to claim 4, characterized in that: The relationship between the thermal conductivity and the empirical coefficient b in step (4) is as follows: b=c×λ d Where: c and d are empirical coefficients; λ is thermal conductivity.

6. The evaluation method according to claim 5, characterized in that: The relationship between the porosity and the correction coefficient b' in step (5) is as follows: b’=e×Ф f Where: b' is the correction coefficient of the empirical coefficient b; e and f are empirical coefficients; Ф is the porosity.

7. The evaluation method according to claim 6, characterized in that: The relationship between the center temperature and the surface temperature of the integrated rock sample in step (6) is as follows: T c =T f -g×r×D 2 ×λ d ×Ф f Where: T c is the center temperature of the rock sample; T f is the surface temperature of the rock sample; r is the heating rate; λ is the thermal conductivity; D is the equivalent diameter of the rock sample; Ф is the porosity; g, d, f are empirical coefficients.

8. The evaluation method according to any one of claims 1 to 7, characterized in that: The surface temperature and center temperature of the rock sample in step (1) are measured in a sample temperature measuring device, which includes a heater, which is sleeved on the outside of the rock sample; a temperature controller is provided on the side wall of the heater, and the bottom of the heater is connected to a product collector through a product discharge pipe; a temperature measuring device is provided in the inner center of the rock sample, and the temperature measuring device is connected to a temperature receiver.

9. The evaluation method according to claim 8, characterized in that: The connecting line between the temperature measuring device and the temperature receiver is covered with a heat insulating sheath; Preferably, the temperature measurer comprises a thermocouple or an optical fiber.

10. The evaluation method according to claim 8 or 9, characterized in that: A heat-insulating layer is arranged outside the heater.

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