Cement paste rheological property prediction method based on multiple linear regression

Abstract

The invention discloses a cement paste rheological property prediction method based on multiple linear regression. The method comprises the following steps: S1, preparing cement paste; s2, performing a cement paste normal-temperature rheological experiment on the cement paste; s3, performing a cement paste high-temperature and high-pressure rheological experiment on the cement paste; s4, standardizing the temperature T, the shear rate gamma, the pressure p and the shear stress tau in the two groups of experimental test data obtained in the step S2 and the step S3; s5, respectively obtaining a cement paste normal-pressure rheological property fitting equation and a cement paste high-temperature and high-pressure rheological property fitting equation by adopting a multivariate nonlinear regression model; the method is simple and easy to use, and can accurately predict the rheological properties of different cement slurries under the influence of multiple factors such as different temperatures, pressures and shear rates, so that the rheological parameters of the cement slurries at different depths of a shaft under the temperature and pressure conditions are more accurately predicted, and whether the pressure of the shaft is in a safety window or not is judged.

Description

Technical Field

[0001] The invention relates to the technical field of petroleum and natural gas cementing, and in particular to a cement slurry rheology prediction method based on multivariate linear regression. Background Art

[0002] As one of the most important links in oil and gas well engineering, cementing is mainly aimed at isolating the oil layer, gas layer and water layer in the wellbore, protecting the casing of the oil and gas well, increasing the life of the oil and gas well and improving the oil and gas production. In the actual cementing and cementing process, under the influence of the high temperature and high pressure environment downhole, the rheology of the cement slurry itself is prone to malignant changes, which may increase the friction resistance of the fluid flow in the wellbore and cause complex accidents such as well leakage, making the annular space isolation ineffective, and seriously threatening the safety of cementing operations. Therefore, how to master the rheological change characteristics of cement slurry under high temperature and high pressure environment is an urgent problem to be solved in the current cementing field.

[0003] Generally speaking, cement slurry is a non-Newtonian fluid, and its shear stress and shear deformation rate show a nonlinear relationship. Its rheological properties are sensitive to temperature and pressure. At the same time, considering the characteristics of cement's own water loss and solidification, the use of general high-temperature and high-pressure rheometer measurements can easily lead to cement consolidation and damage to the instrument. Therefore, it is extremely difficult to directly obtain the real-time rheological parameters of downhole cement slurry through experiments.

[0004] At present, the rheological test method of conventional cement slurry is stipulated in the standard GB / T19139-2012 Oil Well Cement Test Method, and its main contents are: 1) Pour the prepared cement slurry immediately into the slurry cup of the atmospheric pressure viscometer or the pressurized viscometer for stirring, and heat to the required test temperature (<90°C); 2) Continue to stir the cement slurry for 20 minutes after rising to the test temperature; 3) Pour the cement slurry immediately into the sample cup of the viscometer to the scale line; 4) When the rotor rotates at a low speed, raise the slurry cup and measure the reading again, where the rated shear rate on the inner cylinder wall is according to the formula: Calculate the shear stress according to the formula: Calculation; where γ is the rated shear rate, S -1 ;n r is the speed of the viscometer, r / min; R1 and R2 are the radii of the coaxial cylinders (R2>R1), m; τ is the shear stress, Pa; T is the torque per unit length, N; 5) Finally, the rheological properties of the cement slurry are obtained based on the linear function fitting of the measured data.

[0005] Based on the measurement method specified in the standard GB / T19139-2012, many scholars have made innovations on it. Liu Quansheng, Lu Chaobo and Liu Bin from the Wuhan Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, published an article entitled "Research on the Rheological Properties of Cement Slurry Considering the Effects of Temperature and Hydration Time" in the journal "Journal of Rock Mechanics and Engineering". The main content of the article is to use a rotational viscometer to measure the rheological parameters of cement slurry at water grayscale of 1.0-2.0 and temperature of 20-50℃, and describe it based on the simplified Bingham rheological model, and fit and calculate the flow index (n), consistency coefficient (k), and yield stress (τ) at the corresponding temperature point, see Figure 1 ; At the same time, linear equations can also be used to fit the functional relationship between temperature, fluidity index (n), consistency coefficient (k), and yield stress (τ), see Figure 2 This fitting method can simply predict the rheological properties of cement slurry at high temperature, but the fitting accuracy is low (R 2 <0.900), which seriously distorts the prediction results.

[0006] In addition, as deep wells, ultra-deep wells and offshore deep wells become hotspots for oil and gas exploration and development, the static temperature of the bottom of the well during cementing operations generally reaches 150°C. The existing detection methods can only measure the rheological properties of cement slurry in the range of 20 to 50°C, and it is difficult to obtain rheological parameters under high temperature conditions; the published patent CN201610531165 provides an evaluation method for the rheological properties of water-based drilling fluids, which is based on the 130-77 high-temperature and high-pressure rheometer to measure the rheological properties of water-based drilling fluids at pressures of 0.1 to 60 MPa and shear rates of 0 to 350 S -1 The apparent viscosity value is measured at a temperature of 60-130°C with a temperature increase of 10°C, and then the fitting equation is obtained by fitting the scatter plot of apparent viscosity versus temperature using the least squares polynomial to achieve the purpose of predicting the rheological properties of high-temperature and high-pressure drilling fluids. However, this method still cannot avoid the problem of distortion of the prediction results due to multiple factors, such as the cement slurry at low shear (<10.2S -1 ) rate, resulting in inaccurate measurement results at high temperature (>100℃) rheological prediction data distortion (R 2 Low), and less consideration is given to the accurate prediction of the rheological properties of cement slurry under the coupling of temperature and pressure.

[0007] Based on the above situation, there is an urgent need to establish a cement slurry rheology prediction method that can simulate the high temperature and high pressure environment downhole. It can not only accurately predict the high temperature and high pressure rheology of cement slurry, and adjust the slurry rheological parameters in real time to ensure the safety of cementing construction and efficient displacement, but also contribute to the realization of the long-term goals of automated cementing and digital oil fields in the industry. Summary of the invention

[0008] The purpose of the present invention is to provide a cement slurry rheology prediction method based on multivariate linear regression to solve the problems that the existing cement slurry rheology evaluation method cannot obtain the cement slurry rheology parameters under high temperature and high pressure conditions, and the conventional fitting method has low prediction accuracy.

[0009] To this end, the technical solution of the present invention is as follows:

[0010] A method for predicting cement slurry rheology based on multivariate linear regression, the steps are:

[0011] S1. According to the predicted needs on site, cement ash and admixtures on site are used to prepare cement slurry;

[0012] S2, using the cement slurry prepared in step S1 to conduct a room-temperature rheological experiment on the cement slurry, and measuring the shear stress of the cement slurry at each specified experimental temperature and at each rotational speed of the rotational viscometer;

[0013] S3, using the cement slurry prepared in step S1 to perform a high-temperature and high-pressure rheological test on the cement slurry, and measuring the shear stress of the cement slurry at each specified experimental temperature, specified experimental pressure, and specified experimental shear rate;

[0014] S4, standardize the temperature T, shear rate γ, pressure p and shear stress τ in the two sets of experimental test data obtained in step S2 and step S3, and the standardization formula is:

[0015]

[0016] In the formula, x i is the data to be processed, i.e., temperature T, shear rate γ, pressure p or shear stress τ, dimensionless; is the mean, dimensionless; s is the variance, dimensionless;

[0017] S5, using a multivariate nonlinear regression model, the shear stress τ in the normal temperature rheological test data of cement slurry obtained by standardization in step S4 i Set as the strain variable, temperature T i and shear rate γ i As the independent variable, the fitting equation of the normal pressure rheology of cement slurry is obtained: shear stress = a i *Temperature+c i * shear rate + D; the shear stress τ in the high temperature and high pressure rheological test data of cement slurry obtained by standardization in step S4 i Set as the strain variable, temperature T i , pressure p and shear rate γ i The fitting equation of high temperature and high pressure rheology of cement slurry is obtained by fitting with :

[0018] Shear stress = a i *Temperature+bi *Pressure+c i * Shear rate + D; In the above two formulas, a i is the temperature fitting coefficient, dimensionless; b i is the pressure fitting coefficient, dimensionless; c i is the shear rate fitting coefficient, dimensionless; D is the fitting constant, dimensionless.

[0019] Furthermore, in step S2, before each designated experimental temperature test, the slurry cup temperature of the atmospheric pressure viscosifier should be ≤90°C.

[0020] Further, in step S2, the experimental temperatures are specified as: 30°C, 60°C and 90°C; the rotational speed of the rotational viscometer is set to 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min respectively.

[0021] Further, in step S3, the designated experimental temperature range is determined according to the predicted needs of on-site construction, and the designated experimental temperature is set at a temperature interval of 30°C to 40°C; the designated experimental pressure range is determined according to the predicted needs of on-site construction, and the designated experimental pressure is set at a pressure interval of 30MPa to 40MPa; the designated shear rates are sequentially set to the corresponding shear rates converted based on the viscometer speeds of 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min in step S2.

[0022] Compared with the existing technology, the cement slurry rheology prediction method based on multivariate linear regression is simple to use and easy to use. It can accurately predict the rheological properties of different cement slurries under the influence of multiple factors such as temperature, pressure, shear rate, etc., thereby more accurately predicting the rheological parameters of cement slurry under temperature and pressure conditions at different depths in the wellbore, thereby judging whether the wellbore pressure is within the safety window, and effectively guiding the rheology and density adjustment of the pre-fluid and cement slurry in shale oil and long horizontal wells, which not only avoids the occurrence of complex accidents during cementing, but also creates conditions for efficient displacement during injection, providing a powerful tool for oil and gas exploration and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of the cement slurry rheology prediction method based on multivariate linear regression of the present invention;

[0024] Figure 2 The rheological fitting result of cement slurry at corresponding temperature points achieved by using an existing technology;

[0025] Figure 3This is the fitting result of cement slurry temperature-yield stress achieved by using another existing technology. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the following embodiments are by no means intended to limit the present invention in any way.

[0027] See also Figure 1 The specific steps of the cement slurry rheology prediction method based on multivariate linear regression are as follows:

[0028] S1. According to the forecast needs, cement ash and admixtures on site are used to prepare cement slurry for the normal temperature rheology test of cement slurry and the high temperature and high pressure rheology test of cement slurry;

[0029] Specifically, when weighing cement ash and admixtures on site, an electronic balance with an accuracy of ±0.1% should be used; cement slurry should be prepared using a special high-speed mixer; the density of cement slurry should be measured after preparation, and the measurement error of cement slurry density should be ensured to be less than 0.5%;

[0030] S2. Rheological test of cement slurry at room temperature: pour the cement slurry prepared in step S1 into the slurry cup of the atmospheric pressure viscometer and stir it, then heat the cement slurry to the specified experimental temperature and continue stirring for 20 minutes, then pour the cement slurry into the sample cup of the rotational viscometer, and measure the shear stress of the cement slurry at the specified experimental temperature and the rotational viscometer at 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min respectively; wherein the specified experimental temperatures are: 30°C, 60°C and 90°C;

[0031] Among them, before each specified experimental temperature test, the slurry cup temperature of the atmospheric pressure thickener should be ≤90℃ (preferably room temperature) to avoid the possibility of thermal shock to temperature-sensitive admixtures;

[0032] S3. High temperature and high pressure rheological experiment of cement slurry: Add the cement slurry prepared in step S1 into the slurry cup in the high temperature and high pressure rheometer, and then control the cement slurry to reach the specified experimental temperature, pressure and rotation speed, and continue stirring for 20 minutes, and measure the shear stress of the cement slurry at each specified experimental temperature, pressure and shear rate; wherein, the specified experimental temperature range is determined according to the predicted needs of on-site construction, and the specified experimental temperature is set at a temperature interval of 30°C to 40°C; the specified experimental pressure range is determined according to the predicted needs of on-site construction, and the specified experimental pressure is set at a pressure interval of 30MPa to 40MPa; the specified shear rate is the corresponding shear rate obtained based on the rotation speeds of the viscometer selected in step S2 at 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min, respectively, according to the conversion formula between shear rate and rotation speed (see background technology).

[0033] In this embodiment, the high temperature and high pressure rheometer preferably adopts the Qiandele 7600 high temperature and high pressure rheometer, which has a measuring temperature range of 0 to 316°C, a measuring pressure range of 0.1 to 276 MPa, and a shear rate of 0 to 1533S. -1 , not only has a wide measuring range, but also has high accuracy.

[0034] In the above steps S2 and S3, considering that the data read from the rheological properties of cement slurry are often not repeatable when the shear rate is low, the shear stresses obtained by testing at rotation speeds of 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min are used respectively, instead of the shear stresses usually obtained by testing at rotation speeds of φ1, φ3, φ6, φ100, φ300 and φ600 as the original data for fitting, which can effectively improve the fitting of the data.

[0035] S4, performing Z-score standardization on the temperature T, shear rate γ, pressure p and shear stress τ in the two sets of experimental test data obtained in step S2 and step S3, so as to convert the data into dimensionless index evaluation values, i.e., temperature T i , shear rate γ i , pressure p and shear stress τ i , so that the values ​​of each indicator are at the same level;

[0036] The standardized formula for temperature T, shear rate γ, pressure p and shear stress τ is:

[0037]

[0038] In the formula, x iis the data to be processed, i.e., temperature T, shear rate γ, pressure p or shear stress τ, dimensionless; is the mean, dimensionless; s is the variance, dimensionless;

[0039] In step S4, the calculation error caused by the difference in order of magnitude between the data is eliminated by dimensionlessly converting the different data measured in the experiment.

[0040] S5, using a multivariate nonlinear regression model, the shear stress τ in the two sets of data obtained in step S4 i Set as the strain variable, temperature T i , pressure p and shear rate γ i The fitting equations of the normal pressure rheology of cement slurry and the high temperature and high pressure rheology of cement slurry were obtained respectively.

[0041] I. The fitting equation of the normal pressure rheology of cement slurry is:

[0042] Shear stress = a i *Temperature+c i * Shear rate + D,

[0043] II. The fitting equation of high temperature and high pressure rheology of cement slurry is:

[0044] Shear stress = a i *Temperature+b i *Pressure+c i * Shear rate + D,

[0045] In the above two formulas, a i is the temperature fitting coefficient, dimensionless; b i is the pressure fitting coefficient, dimensionless; c i is the shear rate fitting coefficient, dimensionless; D is the fitting constant, dimensionless;

[0046] In the specific fitting process, this embodiment is implemented using the commercial software SPSS. By calling the function of multiple linear regression, shear stress is set as the dependent variable, temperature (or temperature and pressure) and shear rate are set as independent variables, and R is selected. 2 The variation and collinearity diagnosis are then regressed and fitted to obtain a fitting equation; then, the standardized atmospheric rheology fitting equation of cement slurry and the high-temperature and high-pressure standardized rheology fitting equation of cement slurry are reversely transformed through the standardization method of step S4 to obtain the normal equation for the atmospheric rheology fitting of cement slurry and the normal equation for the high-temperature and high-pressure rheology fitting of cement slurry, so as to directly substitute the values ​​of temperature, pressure, and shear rate to obtain the predicted value of shear stress;

[0047] In step S5, the rheology of cement slurry is predicted by using a multivariate linear regression model, which can further improve the scientificity and accuracy of the prediction results compared to the existing technical methods. At the same time, it can introduce cement slurry rheology parameters such as temperature conditions and pressure conditions according to actual needs, adapt to the actual situation of on-site operations and improve its prediction accuracy.

[0048] S6. After the above steps S1 to S5, the fitting equation of the normal pressure rheology of cement slurry and the fitting equation of the high temperature and high pressure rheology of cement slurry are obtained; then, the shear stress of cement slurry at different temperatures and shear rates can be obtained through the two equations, which is the high temperature rheological property of cement slurry, thereby guiding the actual production on site.

[0049] Example 1

[0050] The experimental data in the article "Research on the Length of Cement Replacement Slurry for Oil and Gas Wells" (author: Wen Dayang) mentioned in the background technology (temperature range is 30°C to 90°C, pressure is normal pressure 0.1MPa) is used as the data obtained in the normal pressure rheology experiment obtained in step S2 of this application.

[0051] Some experimental data are shown in Table 1 below.

[0052] Table 1: Experimental data of some temperatures, spacer fluid mixing and cement slurry rheology

[0053]

[0054]

[0055] According to step S3 of the present application, the temperature T, shear rate γ and shear stress τ in the experimental data of Table 1 are subjected to Z-score standardization, and the data are converted into dimensionless index evaluation values, namely, temperature T i , shear rate γ i and shear stress τ i .

[0056] The standardized results of the experimental data are shown in Table 2 below.

[0057] Table 2: Standardized data

[0058]

[0059] Based on the standardized data in Table 2, the method of step S4 of the present application was used to perform multivariate linear regression fitting on the dimensionless data, but it was found that the fitting degree was not high. Considering that the rheological measurement stability of low-speed cement slurry was not good; therefore, four sets of data with rotation speeds of φ100, φ200, φ300 and φ600 were then used and multivariate linear regression fitting was performed using the commercial software SPSS to obtain the atmospheric pressure rheological fitting equation of the cement slurry, which is expressed as follows:

[0060] τ i =-0.226*T i +0.933*γ i +0.001,

[0061] Where, T i is the normalized temperature, dimensionless; γ i is the normalized shear rate, dimensionless; τ i is the normalized shear stress, dimensionless.

[0062] The fitting accuracy R of the atmospheric rheological fitting equation of the cement slurry is 2 It is 0.957901, which is significantly better than the existing technology method.

[0063] Furthermore, through the standardization method in step S3 of this application, the expression is further organized as follows:

[0064] τ=-0.336*T+0.0955*γ+27.6519,

[0065] Where T is temperature, °C; γ is shear rate, s -1 ; τ is shear stress, Pa.

[0066] In practical applications, the shear stress prediction results of a specified cement slurry can be obtained by directly substituting the temperature conditions and shear rate conditions.

[0067] In order to further verify the reliability of the cement slurry rheology prediction method of the present application, the experimental data corresponding to the same cement slurry in the "Research on the Length of Cement Displacement Slurry in Oil and Gas Wells" and in the same temperature range as the fitting equation for the normal pressure rheology of the cement slurry were used, and the experimental parameters were substituted into the above-mentioned normal pressure rheology fitting equation for the cement slurry to obtain the prediction result of shear stress.

[0068] The comparison between the actual measured results and the fitting results is shown in Table 3.

[0069] Table 3: Comparison of measured results and fitting results

[0070] Temperature(℃) <![CDATA[Shear rate (s -1 )]]> Fitting shear stress (Pa) Measured shear stress (Pa) error 30 1021.38 115.1161457 122.129 7.012854255 60 1021.38 105.1619077 92.491 12.67090773 90 1021.38 95.20766971 86.359 8.848669713 30 510.69 86.25395379 97.09 10.83604621 60 510.69 56.29971577 49.567 6.732715775 90 510.69 46.34547776 48.034 1.688522241 30 340.46 49.96655647 48.985 0.981556472 60 340.46 40.01231846 38.325 1.687318456 90 340.46 30.05808044 36.792 6.73391956 30 170.23 33.67915915 36.792 3.112840846 60 170.23 23.72492114 18.396 5.328921138 90 170.23 13.77068312 16.863 3.092316878

[0071] From the fitting accuracy R of the fitting equation 2It can be seen from the error values ​​between the experimental results shown in Table 3 and the predicted results calculated according to the fitting equation that, within the temperature range of 30 to 90°C and the viscometer speed range of φ100 to φ600, the predicted error values ​​of shear stress are all less than 10Pa except for a few temperature points that are slightly greater than 10Pa, which proves that the prediction results of the method of the present application are accurate and reliable, that is, the cement rheology prediction method of the present application is superior to the prior art method disclosed in the background technology.

[0072] Example 2

[0073] The anti-channeling cement slurry system used in the domestic DG oil field drilling project was used as the cement slurry prepared in step S1 of this application (cement slurry formula: G-grade cement 740g + microsilicon 14.8g + Flok-2 37g + water 292g + HX-12L 24g + FS-13L 32g + HX-36L 3%); the density of the cement slurry is 1.90g / cm 3 .

[0074] According to the method of step S3 of the present application, a Qiandelu 7600 high temperature and high pressure rheometer is used to measure the change of shear stress of cement slurry with shear rate in the operating temperature range (60°C to 150°C) and pressure range (30Mpa to 110Mpa).

[0075] Some test results are shown in Table 4 below.

[0076] Table 4: Some temperature, pressure-cement slurry rheology test data

[0077]

[0078] Using the method of step S4 of the present application, the temperature T, pressure P, shear rate γ and shear stress τ in the experimental data of Table 4 are normalized by the Z-score in formula 3, that is, the data is converted into a dimensionless index evaluation value, namely, the temperature T i 、Pressure P i , shear rate γ i and shear stress τ i .

[0079] The standardized results of the experimental data are shown in Table 5 below.

[0080] Table 5: Standardized data

[0081]

[0082]

[0083] Based on the standardized data in Table 5, the dimensionless data were subjected to multivariate linear regression fitting using the method in step S4 of the present application to obtain the standardized high temperature and high pressure rheological fitting equation of the cement slurry, which is expressed as follows:

[0084] τ i =-0.238*T i +0.025*P i -0.943*γ i -2.621*10 -7 ,

[0085] Where, T i is the normalized temperature, dimensionless; γ i is the normalized shear rate, dimensionless; τ i is the normalized shear stress, dimensionless.

[0086] The fitting accuracy R of the atmospheric rheological fitting equation of the cement slurry is 2 It is 0.971429, which is significantly better than the existing technology methods.

[0087] Furthermore, through the standardization method in step S3 of the present application, the standardized high temperature and high pressure rheological property fitting equation of the cement slurry is further organized into the high temperature and high pressure rheological property fitting equation of the cement slurry:

[0088] τ=-0.1616*T+0.0199*P-0.0578*γ+16.0981,

[0089] Where T is temperature, °C; γ is shear rate, s -1 ; τ is shear stress, Pa.

[0090] In practical applications, the shear stress prediction result of a specified cement slurry can be obtained by directly substituting the temperature conditions and shear rate conditions, that is, the rheological parameters of the cement slurry under the temperature and pressure conditions at different depths in the wellbore can be accurately predicted, thereby judging whether the wellbore pressure is within the safety window.

[0091] In order to further verify the reliability of the cement slurry rheology prediction method of the present application, different experimental data were selected within the same operating temperature range and pressure range as those of Example 2 using the cement slurry in Example 2, and the experimental parameters were substituted into the high-temperature and high-pressure rheology fitting normal equation of the above-mentioned cement slurry to obtain the prediction results of shear stress; the specific measured results are compared with the fitting results as shown in Table 6 below.

[0092] Table 6: Comparison of measured results and fitting results

[0093] Temperature(℃) Pressure(MPa) <![CDATA[Shear rate (s -1 )]]> Fitting shear stress (Pa) Measured shear stress (Pa) error 60.95 31 1021.38 66.06925291 76.68 10.61074709 62.22 30 851.15 55.98622686 62.93 6.94377314 63.25 30 680.92 45.96189728 49.98 4.018102725 64.19 30 510.69 35.95231718 37.46 1.507682823 65.1 30 340.46 25.94765357 25.28 0.667653573 65.54 30 170.23 16.02001506 12.98 3.040015064 66.01 30 102.14 12.0008938 7.9 4.100893797 66.4 31 51.07 8.999626986 4.18 4.819626986 68.8 71.29 1021.38 65.56296557 73.32 7.757034429 69.4 70 851.15 55.58412555 60.9 5.315874449 70 71 680.92 45.64963023 48.93 3.280369769 70.47 70 510.69 35.69771073 36.73 1.032289271 70.94 70 340.46 25.76515572 24.68 1.085155724 71.21 72 170.23 15.90410635 13.11 2.794106352 71.4 70.58 102.14 11.90337479 7.73 4.173374788 71.6 71 51.07 8.922014373 4.6 4.322014373 118.4 70.25 1021.38 57.41422078 56.26 1.154220779 119 70.12 851.15 47.45784358 44.94 2.517843577 119.6 70 680.92 37.50166002 34.92 2.58166002 120.15 70 510.69 27.55599436 25.77 1.785994361 120.76 70 340.46 17.60049571 17.19 0.410495712 120.98 70.38 170.23 7.716270011 8.53 0.813729989 121.23 71 102.14 3.745209032 5.63 1.884790968 121.48 70.63 51.07 0.740356505 3.46 2.719643495 123.3 111 1021.38 57.40029649 60.38 2.979703507 123.51 110 851.15 47.49098662 48.26 0.769013383 123.84 110 680.92 37.58137526 37.06 0.521375258 124.2 110.59 510.69 27.67827246 27.17 0.508272458 124.6 109.5 340.46 17.73608197 17.91 0.173918027 124.8 111.41 170.23 7.884761619 8.91 1.025238381 125 110 102.14 3.882584867 5.83 1.947415133 125.2 110 51.07 0.893091363 3.26 2.366908637

[0094] From the fitting accuracy R of the fitting equation2 , and the error values ​​between the experimental results shown in Table 6 and the predicted results calculated according to the fitting equation, it can be seen that the error between the predicted results and the experimental measured results is small, and with the increase of temperature, the error value between the predicted results and the experimental measured results tends to decrease; in addition, compared with the prediction of the atmospheric pressure cement slurry rheology experimental data in Example 1, the high temperature and high pressure cement slurry rheology fitting equation is obtained by fitting the experimental data obtained by the method of step S2 of the present application, and thus has higher fitting accuracy than the fitting equation in Example 1, and furthermore, the predicted data obtained based on the high temperature and high pressure cement slurry rheology fitting equation in Example 2 is more consistent with the experimental data, which once again proves that the prediction results obtained by the method of the present application are accurate and reliable.

Claims

1. A method for predicting cement slurry rheology based on multivariate linear regression, characterized in that: The steps are: S1. According to the predicted needs on site, cement ash and admixtures on site are used to prepare cement slurry; S2, using the cement slurry prepared in step S1 to conduct a room-temperature rheological experiment on the cement slurry, and measuring the shear stress of the cement slurry at each specified experimental temperature and at each rotational speed of the rotational viscometer; S3, using the cement slurry prepared in step S1 to perform a high-temperature and high-pressure rheological test on the cement slurry, and measuring the shear stress of the cement slurry at each specified experimental temperature, specified experimental pressure, and specified experimental shear rate; S4, standardize the temperature T, shear rate γ, pressure p and shear stress τ in the two sets of experimental test data obtained in step S2 and step S3, and the standardization formula is: In the formula, x i is the data to be processed, i.e., temperature T, shear rate γ, pressure p or shear stress τ, dimensionless; is the mean, dimensionless; s is the variance, dimensionless; S5, using a multivariate nonlinear regression model, the shear stress τ in the normal temperature rheological test data of cement slurry obtained by standardization in step S4 i Set as the strain variable, temperature T i and shear rate γ i The fitting equation of the normal pressure rheology of cement slurry is obtained by fitting with the independent variable: shear stress = a i *Temperature+c i * shear rate + D; the shear stress τ in the high temperature and high pressure rheological test data of cement slurry obtained by standardization in step S4 i Set as the strain variable, temperature T i , pressure p and shear rate γ i The fitting equation of high temperature and high pressure rheology of cement slurry is obtained by fitting with : shear stress = a i *Temperature+b i *Pressure+c i * Shear rate + D; In the above two formulas, a i is the temperature fitting coefficient, dimensionless; b i is the pressure fitting coefficient, dimensionless; c i is the shear rate fitting coefficient, dimensionless; D is the fitting constant, dimensionless.

2. The method for predicting cement slurry rheology based on multivariate linear regression according to claim 1, characterized in that: In step S2, before each designated experimental temperature test, the slurry cup temperature of the atmospheric pressure viscosifier should be ≤90°C.

3. The method for predicting cement slurry rheology based on multivariate linear regression according to claim 1, characterized in that: In step S2, the experimental temperatures are specified as: 30°C, 60°C and 90°C; the rotational speed of the rotational viscometer is set to 10 r / min, 20 r / min, 30 r / min, 60 r / min, 100 r / min, 200 r / min, 300 r / min and 600 r / min, respectively.

4. The method for predicting cement slurry rheology based on multivariate linear regression according to claim 1, characterized in that: In step S3, the designated experimental temperature range is determined according to the predicted needs of on-site construction, and the designated experimental temperature is set at a temperature interval of 30°C to 40°C; the designated experimental pressure range is determined according to the predicted needs of on-site construction, and the designated experimental pressure is set at a pressure interval of 30MPa to 40MPa; the designated shear rates are sequentially set to the corresponding shear rates converted based on the viscometer speeds of 10r / min, 20r / min, 30r / min, 60r / min, 100r / min, 200r / min, 300r / min and 600r / min in step S2.

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