A method for determining oil viscosity-temperature model

Abstract

The invention provides a method for determining a viscosity-temperature model of an oil product, belonging to the technical field of oil product performance simulation, and comprising: obtaining the actual viscosity of the oil product at a plurality of different temperatures, establishing a power model and an exponential model for calculating the viscosity of the oil product, and obtaining constants of the model; establishing a viscosity-temperature model, wherein the constants of the power model and the exponential model and the coefficients of the viscosity-temperature model can be fitted according to the viscosity data of the oil product, and can also be obtained according to the inventor's empirical formula. When the empirical formula is adopted, it is only necessary to obtain the density of the oil product at 20° C. and the viscosity at 50° C. The method is simple to operate, can quickly obtain the viscosity-temperature model, and the accuracy of the result obtained by the viscosity-temperature model is significantly improved compared with the existing exponential model and power model.

Description

Technical Field

[0001] The present invention relates to the technical field of oil product performance simulation, in particular to viscosity-temperature characteristic estimation, and specifically to a method for determining an oil product viscosity-temperature model. The method is applicable to petroleum fractions and mixtures thereof, such as a mixture of gasoline, diesel, kerosene and heavy oil. Background Art

[0002] Determining the viscosity of oil at different temperatures can help us understand the properties and changes of oils so that we can use them better. At the same time, different types of oils have different viscosity performances at different temperatures. Therefore, in the fields of oil field production, mechanical design, etc., it is necessary to select suitable oils and temperature conditions according to specific application needs.

[0003] Generally speaking, the most accurate way to measure the viscosity of oil products under different temperature conditions is to use indoor viscometers and rheometers, but this requires a lot of time and cost. At present, it is gradually becoming a popular trend to directly use data models to calculate the viscosity of oil products under different temperature conditions. According to different modeling ideas and theoretical foundations, oil viscosity models include theoretical models and empirical models. Among them, theoretical models have strong theoretical significance and can provide more oil information, but the disadvantage is that many physical parameters need to be provided, and the calculation process is extremely complicated; empirical equations have the advantages of being simple and easy to use, having a wide range of applications and few input parameters, but the calculation accuracy and reliability are low. Therefore, it is necessary to develop an oil viscosity-temperature calculation model with a relatively simple calculation process and relatively high accuracy. Summary of the invention

[0004] In view of the above problems, an object of the present invention is to provide a method for determining an oil viscosity-temperature model to improve the accuracy of the existing empirical model.

[0005] The technical solution of the present invention is:

[0006] A method for determining an oil viscosity-temperature model comprises the following steps:

[0007] S1. Obtain the actual viscosity of the oil at multiple different temperatures

[0008] S2. Establish a power model and an exponential model for calculating the viscosity of oil products and obtain the constants of the model;

[0009] Among them, the power model is as follows:

[0010]

[0011] Exponential Model:

[0012]

[0013] Among them, T i is the ith temperature value; a, b, c, d are all constants; The temperature T i Calculation viscosity of power model and exponential model under certain conditions;

[0014] S3, constructing oil viscosity-temperature model;

[0015] The oil viscosity-temperature model is as follows:

[0016]

[0017] in,

[0018]

[0019] In the formula, are coefficients respectively; n is the total number of oil temperature points;

[0020] Of course, from the calculation formula, we can see that Therefore, this relationship can also be used to Find the value of any one of them and then find the value of the other one to simplify the calculation.

[0021] Step S2 of the present invention involves determining a power model and an exponential model for determining the viscosity of oil products, and mainly determines constants a, b, c, and d therein. These constants can be constants disclosed by currently known empirical formulas, or can be obtained by fitting the data obtained in step S1. Fitting requires reprocessing the data, which is time-consuming. Of course, the constants obtained by fitting a single oil product are more accurate for calculating the viscosity of the oil product.

[0022] The inventors have fitted a variety of oil products and found the following: For some oil products, these constants and coefficients are closely related to the density ρ0 of the oil products at 20°C. These constants and coefficients can be calculated with high accuracy through the density at 20°C and the correlation formula between them; however, for some oil products, when the constants and coefficients determined by the above empirical formula are used to calculate the viscosity of the oil products, the accuracy is significantly reduced. However, the inventors have further found that for the viscosity of these oil products, the density of the oil products at 20°C can be corrected by the viscosity at 50°C. After the corrected density is used to calculate the viscosity of the oil products, the prediction accuracy is significantly improved. Therefore, for these oil products, it is necessary to correct the density of the oil products by the viscosity at 50°C, and then determine its constants, so as to improve the calculation accuracy of the viscosity of the oil products. In this regard, the inventors have proposed a new method for determining the viscosity-temperature model of oil products, which includes the following steps:

[0023] S1. Obtain the density ρ0 of the oil at 20°C and the viscosity μ at 50°C 150 ;

[0024] S2. Obtain constants of a power model and an exponential model for calculating the viscosity of oil products. This can be obtained using an existing empirical formula or an empirical formula disclosed in the present invention. Use the empirical formula to obtain coefficients of a temperature model and establish a viscosity-temperature model.

[0025] The viscosity-temperature model is as follows:

[0026]

[0027] The empirical formula for calculating the constant in the viscosity-temperature model is as follows:

[0028] When ρ0≤0.860g / cm 3 hour,

[0029]

[0030]

[0031]

[0032]

[0033] When 0.860<ρ0≤0.916g / cm 3 hour:

[0034]

[0035]

[0036]

[0037]

[0038] When ρ0>0.916g / cm 3 hour:

[0039]

[0040]

[0041]

[0042]

[0043] The empirical formula for calculating the coefficient in the viscosity-temperature model is as follows:

[0044] When ρ0>0.90g / cm 3 hour,

[0045] When 0.860<ρ0≤0.90g / cm 3 hour,

[0046] When 0.830≤ρ0≤0.860g / cm 3 hour,

[0047] When ρ0<0.830g / cm 3 hour,

[0048] S3, calculate the viscosity of the oil at 50°C using the viscosity-temperature model established in step S2, and compare the viscosity calculated by the viscosity-temperature model with the oil viscosity μ at 50°C obtained in step S1 150 When the error between the two is not greater than the preset threshold, the viscosity-temperature model obtained in step S2 is used as the final viscosity-temperature model of the oil; when the error between the two is greater than the preset threshold, the oil viscosity μ at 50°C obtained in step S1 is used as the final viscosity-temperature model of the oil. 150 The corrected density ρ1 of the oil is obtained by using the density correction empirical formula, and the density of the oil at 20°C is replaced by the corrected density ρ1, and the process returns to step S2 to update the constants and coefficients of the viscosity-temperature model to obtain the final viscosity-temperature model of the oil;

[0049] The density correction empirical formula for the corrected density ρ1 is as follows:

[0050] When ρ0>0.916g / cm 3 hour,

[0051]

[0052] When 0.860<ρ0≤0.916g / cm 3 hour:

[0053]

[0054] When ρ0≤0.860g / cm 3 hour,

[0055]

[0056] For the preset threshold, those skilled in the art can determine it according to actual results. For example, for ρ0≤0.860g / cm 3 Oil (light oil), the relative error is no more than 15.7%, for 0.860 < ρ0 ≤ 0.916 g / cm 3 The relative error of oil products (medium quality oil products) is no more than 0.4%. For ρ0>0.916g / cm 3 For oil products (heavy oil products), the relative error is no more than 2.0%.

[0057] Beneficial effects:

[0058] The present invention provides a method for determining a viscosity-temperature model of an oil product. The method is simple to operate and can quickly obtain a viscosity-temperature model. Moreover, the accuracy of the result obtained by the viscosity-temperature model is significantly improved compared with the existing exponential model and power model. DETAILED DESCRIPTION

[0059] The specific implementation modes of the present invention will be described clearly and completely below with reference to examples. Obviously, the examples described are only some embodiments of the present invention, rather than all embodiments.

[0060] A method for determining an oil viscosity-temperature model, comprising:

[0061] S1. Obtain the actual viscosity of the oil at multiple different temperatures

[0062] The mixed oil in this embodiment is a mixed oil of heavy oil and liquid light hydrocarbon (kerosene); the experimental oil was dehydrated by DWY-6A crude oil dehydrator, and the viscosity of the mixed oil was measured multiple times at the same temperature by DV3TLVTJ0 viscometer, and the average value was taken. The test shear rate was 7.36s -1 , the test data of each oil product are shown in Table 1 and Table 2.

[0063] Table 1 Viscosity and density data of various oil products

[0064] serial number Oil name Density(20℃) Viscosity (50℃) Sample 1 kerosene 0.7751 0.76 Sample 2 gasoline 0.7473 0.38 Sample 3 diesel fuel 0.8257 1.79 Sample 4 Light crude oil A 0.8179 2.40 Sample 5 Medium crude oil H 0.8827 73.93 Sample 6 Heavy Oil 0.9334 1320.00 Sample 7 Light mixed oil Q4 0.8478 5.38 Sample 8 Medium mixed oil NT1 0.8768 54.80 Sample 9 Heavy mixed oil MH0 0.9246 1354.00

[0065] Table 2 Statistics of viscosity of various oil products at different temperatures

[0066]

[0067]

[0068] S2. Establish a power model and an exponential model for calculating oil viscosity;

[0069] Among them, the power model is as follows:

[0070]

[0071] Exponential Model:

[0072]

[0073] Among them, T i is the oil product at the ith temperature; a, b, c, d are all constants; The temperature T i Calculation viscosity of power model and exponential model under certain conditions;

[0074] In this embodiment, each oil product is fitted respectively, and the constants of the power model and the exponential model are obtained as shown in Table 3:

[0075] Table 3 Constant statistics of power model and exponential model for different oil products

[0076]

[0077] S3, constructing an oil viscosity-temperature model based on the calculation deviation of the power model and the exponential model;

[0078] The oil viscosity-temperature model is as follows:

[0079]

[0080] in,

[0081]

[0082] In the formula, are coefficients respectively; n is the total number of oil temperature points;

[0083] In order to simplify the calculation in this embodiment, first obtain According to The specific results are shown in Table 4.

[0084] Table 4 Statistics of coefficients in viscosity-temperature models for different oils

[0085]

[0086] Calculation of the deviation of various oil products calculated using different models: For the same oil product, the measured viscosity under different temperature conditions is compared with the calculated viscosity using the power model, the exponential model, and the model of the present invention, and the average deviation is calculated. The specific calculation formula is as follows:

[0087]

[0088] is the calculated viscosity using a certain model;

[0089] The calculation results of the above method are as follows:

[0090] Table 5 Statistics of calculation deviations of different models

[0091] serial number Power model (%) Index model (%) Model of the present invention (%) Sample 1 2.88 2.70 2.12 Sample 2 9.38 6.57 5.34 Sample 3 9.28 6.29 7.45 Sample 4 3.95 3.86 2.53 Sample 5 6.60 5.39 3.44 Sample 6 4.17 9.36 1.41 Sample 7 2.08 3.99 2.14 Sample 8 4.10 3.97 1.23 Sample 9 14.13 5.49 4.85 Average Error 6.29 5.29 3.39

[0092] It can be seen from the above data that the average fitting errors of the power model and the exponential model fitted by the measured data are 6.29% and 5.29%, while the average calculation error of the model obtained by the present invention is 3.39%, which is significantly better than the former.

[0093] Example 2

[0094] In order to determine the accuracy of the empirical formula of the viscosity-temperature model of the present invention, this embodiment continues to use the measured data of Example 1, but changes the method of obtaining the constants and coefficients in Example 1. This embodiment obtains the constants and coefficients through the density ρ0 of the oil at 20°C and the viscosity at 50°C. The specific steps are as follows:

[0095] S1. Determine the density ρ0 of the oil at 20℃ and the viscosity μ at 50℃ 150 , specific data are shown in Table 1.

[0096] S2. Obtain constants of a power model and an exponential model and coefficients of a viscosity-temperature model for calculating oil viscosity through empirical formulas, and establish a viscosity-temperature model;

[0097] The viscosity-temperature model is as follows:

[0098]

[0099] The empirical formula for calculating the coefficient is as follows:

[0100] When ρ0>0.90g / cm 3 hour,

[0101] When 0.860<ρ0≤0.90g / cm 3 hour,

[0102] When 0.830≤ρ0≤0.860g / cm 3 hour,

[0103] When ρ0<0.830g / cm 3 hour,

[0104] The empirical formula for calculating the constant is as follows:

[0105] If ρ0≤0.860g / cm 3 ,but

[0106]

[0107]

[0108]

[0109]

[0110] If 0.860<ρ0≤0.916g / cm 3 ,but

[0111]

[0112]

[0113]

[0114]

[0115] If ρ0>0.916g / cm 3 ,but

[0116]

[0117]

[0118]

[0119]

[0120] S3, calculate the viscosity of the oil at 50°C using the viscosity-temperature model established in step S2, and compare the viscosity calculated by the viscosity-temperature model with the oil viscosity μ at 50°C obtained in step S1 150 When the error between the two is not greater than the preset threshold, the viscosity-temperature model obtained in step S2 is used as the final viscosity-temperature model of the oil; when the error between the two is greater than the preset threshold, the oil viscosity μ at 50°C obtained in step S1 is used as the final viscosity-temperature model of the oil. 150 The corrected density ρ1 of the oil is obtained by using the density correction empirical formula, and the density of the oil at 20°C is replaced by the corrected density ρ1, and the process returns to step S2 to update the constants and coefficients of the viscosity-temperature model to obtain the final viscosity-temperature model of the oil;

[0121] For the preset threshold, in this embodiment, for ρ0≤0.860g / cm 3 Oil (light oil), the relative error is no more than 15.7%, for 0.860 < ρ0 ≤ 0.916 g / cm 3 The relative error of oil products (medium quality oil products) is no more than 0.4%. For ρ0>0.916g / cm 3 For oil products (heavy oil products), the relative error is no more than 2.0%.

[0122] The empirical formula for correcting the density ρ1 is as follows:

[0123] When ρ0>0.916g / cm 3 hour,

[0124]

[0125] When 0.860<ρ0≤0.916g / cm 3 hour:

[0126]

[0127] When ρ0≤0.860g / cm 3 hour,

[0128]

[0129] The constants and coefficients of oil products obtained according to the empirical formula are shown in Table 6.

[0130] Table 6 Statistics of constants and coefficients obtained by empirical formula for each oil product

[0131] serial number <![CDATA[log 10 a]]> b c d f1 f2 Sample 1 1.399 -0.908 1.8465 -0.017 0.444795 0.555205 Sample 2 1.742 -1.349 1.1466 -0.026 0.473348 0.526652 Sample 3 1.461 -0.727 3.5832 -0.014 0.392824 0.607176 Sample 4 1.657 -0.738 5.4396 -0.014 0.400835 0.599165 Sample 5 5.529 -2.146 633.0201 -0.041 0.438671 0.561329 Sample 6 9.025 -3.468 44863.7426 -0.070 0.489795 0.510205 Sample 7 2.402 -0.984 14.8449 -0.019 0.563181 0.436819 Sample 8 5.214 -2.026 428.2420 -0.039 0.498867 0.501133 Sample 9 8.907 -3.405 39052.4783 -0.069 0.435858 0.564142

[0132] The constants and coefficients obtained by these empirical formulas are used to determine the viscosity-temperature model of this embodiment, and the calculated results are compared with the actual measured values ​​to determine the relative error rate. The specific calculation method is the same as in Example 1 and is not described in detail here. The specific calculation results are shown in Table 7.

[0133] Table 7 Calculation deviation statistics of viscosity-temperature model

[0134] serial number Relative error (%) Sample 1 2.58 Sample 2 5.72 Sample 3 3.91 Sample 4 2.56 Sample 5 5.01 Sample 6 4.57 Sample 7 2.02 Sample 8 1.42 Sample 9 3.21 Average Error 3.44

[0135] Combined with the data of Example 1, it can be seen that the average fitting errors of the power model and the exponential model fitted by the measured data are 6.29% and 5.29%, while the average calculation error of the model obtained by the constants and coefficients obtained by the empirical formula of the present invention is 3.44%, which is also significantly better than the former.

[0136] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for determining an oil viscosity-temperature model, characterized in that: The following steps are involved: S1. Obtain the actual viscosity of the oil at multiple different temperatures S2. Establish a power model and an exponential model for calculating oil viscosity and determine the constants in the model; Among them, the power model is as follows: Exponential Model: Among them, T i is the ith temperature value; a, b, c, d are all constants; The temperature T i Calculation viscosity of power model and exponential model under certain conditions; S3, constructing oil viscosity-temperature model; The oil viscosity-temperature model is as follows: in, In the formula, All are coefficients; n is the total number of oil temperature points.

2. A method for determining an oil viscosity-temperature model, characterized in that: The following steps are involved: S1. Obtain the density ρ0 of the oil at 20°C and the viscosity μ at 50°C 150 ; S2. Obtain constants of a power model and an exponential model for calculating oil viscosity, obtain coefficients of a viscosity-temperature model using an empirical formula, and establish a viscosity-temperature model; The viscosity-temperature model is as follows: Where, T i is the i-th temperature value; a, b, c, and d are all constants; All are coefficients; The empirical formula for calculating the coefficient is as follows: When ρ0>0.90g / cm 3 hour, When 0.860<ρ0≤0.90g / cm 3 hour, When 0.830≤ρ0≤0.860g / cm 3 hour, When ρ0<0.830g / cm 3 hour, S3, calculate the viscosity of the oil at 50°C using the viscosity-temperature model established in step S2, and compare the viscosity calculated by the viscosity-temperature model with the oil viscosity μ at 50°C obtained in step S1 150 When the error between the two is not greater than the preset threshold, the viscosity-temperature model obtained in step S2 is used as the final viscosity-temperature model of the oil; when the error between the two is greater than the preset threshold, the oil viscosity μ at 50°C obtained in step S1 is used as the final viscosity-temperature model of the oil. 150 The corrected density ρ1 of the oil is obtained by using the density correction empirical formula, and the density of the oil at 20°C is replaced by the corrected density ρ1, and the process returns to step S2 to update the constants and coefficients of the viscosity-temperature model to obtain the final viscosity-temperature model of the oil; The empirical formula for correcting the density ρ1 is as follows: When ρ0>0.916g / cm 3 hour, When 0.860<ρ0≤0.916g / cm 3 hour: When ρ0≤0.860g / cm 3 hour, 3. The method according to claim 2, characterized in that Step S2 includes obtaining constants of the power model and the exponential model according to the empirical formula: The empirical formulas of constants and densities of power model and exponential model are as follows: If ρ0≤0.860g / cm 3 ,but If 0.860<p0≤0.916g / cm 3 ,but If ρ0>0.916g / cm 3 ,but 4. The method according to claim 2, characterized in that: The rules for presetting the threshold in step S3 are as follows: If ρ0≤0.860g / cm 3 , then the relative error is no more than 15.7%; If 0.860<ρ0≤0.916g / cm 3 , the relative error is no more than 0.4%; If ρ0>0.916g / cm 3 , the relative error is no more than 2.0%.

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