Method for determining viscosity-concentration relation parameter of polymer solution and application
By establishing a mathematical model through indoor experiments and the nonlinear least squares method, the viscosity-concentration parameters of the polymer solution are calculated, which solves the problems of slow speed and low accuracy in the existing technology and realizes efficient parameter calculation and accurate description of polymer flooding numerical simulation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-27
- Publication Date
- 2026-03-27
AI Technical Summary
Existing methods for calculating the viscosity-concentration relationship parameters of polymer solutions are slow and lack accuracy, affecting the accuracy of polymer flooding numerical simulations.
The viscosity-concentration relationship curve of polymer solution was determined by indoor experiments. A mathematical model was established using the nonlinear least squares method to calculate the viscosity-concentration relationship parameters Ap1, Ap2, Ap3 and Sp of polymer solution, thus achieving automated calculation.
It improves the calculation speed and accuracy of polymer solution viscosity-concentration parameters, provides accurate parameters for polymer flooding numerical simulation, and enhances the ability to describe the viscous oil displacement mechanism.
Smart Images
Figure CN121747739A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of tertiary oil recovery technology in oilfield development, and in particular to a method for calculating viscosity-concentration parameters in polymer flooding. Background Technology
[0002] The statements in this section provide only background information in connection with this disclosure and do not constitute prior art.
[0003] In numerical simulation studies of polymer flooding, numerous physicochemical phenomena are described by equations. Many parameters in these equations are crucial indicators of the polymer flooding mechanism, among which the viscosity-concentration relationship parameter of the polymer solution is a key indicator of the viscous flooding mechanism. Accurately determining this parameter is critical for describing the viscous flooding mechanism. Currently, neither domestic nor international numerical simulation software possesses the function to calculate the viscosity-concentration relationship parameter of the polymer solution, nor does it offer a specific method for such calculation. Traditional methods typically involve manual calculation, which is not only inefficient but also lacks accuracy. Therefore, it is necessary to establish a method for calculating the viscosity-concentration relationship parameter of the polymer solution to improve the calculation speed and accuracy, thereby providing accurate parameters for describing the viscous flooding mechanism in polymer flooding numerical simulations.
[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art. Summary of the Invention
[0005] In view of this, this disclosure provides a method for determining the viscosity-concentration relationship parameter of a polymer solution and its application, which solves the problem that traditional methods for determining the viscosity-concentration parameter of polymer solutions rely on manual calculation, which is not only slow but also difficult to guarantee accuracy.
[0006] To address the aforementioned problems, the present invention discloses a method for determining the viscosity-concentration relationship parameter of a polymer solution. The underlying principle is as follows:
[0007] The viscosity-concentration relationship curve of a polymer solution was determined using indoor experiments. A mathematical model for calculating the viscosity-concentration relationship parameter of the polymer solution was established based on the nonlinear least squares method. Based on this mathematical model, the viscosity-concentration relationship parameter A of the polymer solution was calculated using experimental data, the effective salt concentration of the polymer, and other relevant parameters. p1 A p2 A p3 and S p .
[0008] Based on the technical concept of this invention, and to achieve the above-mentioned objective, in a first aspect, the method for determining the viscosity-concentration relationship parameter of the polymer solution includes:
[0009] Viscosity-concentration curves and effective salt concentrations of the polymer solution in the target block were obtained through indoor experiments. A mathematical model for calculating the viscosity-concentration relationship parameters of the polymer solution was established using the nonlinear least squares method. Based on this mathematical model, the viscosity-concentration relationship parameter A of the polymer solution in the target block was calculated using the experimental data and the effective salt concentrations of the polymer solution. p1 A p2 A p3 and S p .
[0010] In this disclosure and possible embodiments, the mathematical model for calculating the polymer solution viscosity-concentration parameter is:
[0011] in, The viscosity of the polymer solution at zero shear rate. The viscosity of the zero-shear rate polymer solution was determined in an indoor experiment.
[0012] In this disclosure and possible embodiments, based on the fact that the partial derivatives of both sides of the mathematical model with respect to the fitting coefficients are zero, the viscosity-concentration parameter A of the polymer solution in the target block is calculated by solving a system of four linear equations. p1 A p2 A p3 and S p .
[0013] In this disclosure and possible embodiments, the effective salt concentration of the polymer is calculated using the following formula:
[0014] C SEP =C 40 +6.5*C 50 ;
[0015] Among them, C 40 To determine the anion concentration in the water, the chloride ion concentration is used; C 50 The cation concentration in the water is calculated by summing the calcium ion concentration and the magnesium ion concentration.
[0016] In this disclosure and possible embodiments, the method for determining the viscosity-concentration relationship parameter of the polymer solution further includes:
[0017] Determine the accuracy of parameter calculations;
[0018] The determination method involves comparing the calculated viscosity of the same polymer solution with the results of indoor experimental measurements.
[0019] The formula for calculating the viscosity of the polymer solution is:
[0020]
[0021] Among them, C p The concentration of the polymer in the solution; μ w C is the viscosity of the aqueous phase. SEP This represents the effective salt concentration of the polymer.
[0022] Secondly, the method for determining the viscosity-concentration relationship parameter of the polymer solution described in the first aspect is applied to the prediction of the development effect of the target block.
[0023] In this disclosure and possible embodiments, the application method includes:
[0024] The viscosity-concentration relationship parameters of the polymer solution calculated by the determination method described in any one of the first aspects are entered into the chemical flooding numerical simulation software;
[0025] Set the parameters for the polymer drive process based on the dynamic data of the target block polymer drive mining farm;
[0026] The polymer flooding history of the target block was fitted using the chemical flooding numerical simulation software. Based on the good results achieved in the history fitting, the development effect of the target block was predicted.
[0027] In this disclosure and possible embodiments, the dynamic data of the target block polymer flooding mine includes the injection rate, injection time, polymer molecular weight, and polymer concentration during the polymer injection stage.
[0028] In this disclosure and possible embodiments, the fitting indices for the historical fitting include instantaneous oil production, instantaneous water production, and water cut of the entire region.
[0029] In this disclosure and possible embodiments, the history fitting is performed using CHEMEOR chemical flooding numerical simulation software.
[0030] The beneficial effects of this invention are as follows:
[0031] The method for determining the viscosity-concentration relationship parameter of a polymer solution disclosed herein establishes a mathematical model for calculating the viscosity-concentration parameter of the polymer solution based on a polymer solution viscosity-concentration relationship curve determined in the laboratory. Then, by solving a system of four linear equations, the viscosity-concentration parameter A of the polymer solution in the target block is calculated. p1 A p2 A p3 and S pThis technology enables automated calculation of viscosity-concentration parameters for polymer flooding, overcoming the technical bottlenecks of slow speed and low accuracy in manual calculations. Furthermore, the calculation results are applied to the numerical simulation research of polymer flooding to describe the mechanism of polymer viscous oil displacement. Combined with the dynamic data of polymer flooding mines in the target block, the development effect of the target block can be predicted. Attached Figure Description
[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the specification, serve to illustrate the technical solutions of this disclosure.
[0033] Figure 1 This is a flowchart of the polymer flooding viscosity-concentration parameter determination method according to an embodiment of this disclosure;
[0034] Figure 2 The polymer solution viscosity-concentration relationship curves, measured in the laboratory, are for the polymer used in the target block in this embodiment of the disclosure.
[0035] Figure 3 This is a visualization interface for calculating the viscosity-concentration parameters of the polymer solution in the embodiments of this disclosure;
[0036] Figure 4 This is a comparison chart of the polymer solution viscosity-concentration data and the calculated polymer solution viscosity-concentration data for the target block in this embodiment of the present disclosure.
[0037] Figure 5 This is a moisture content fitting curve for the target block in this embodiment of the disclosure;
[0038] Figure 6 This is a prediction curve of the development effect of the target block in the embodiments of this disclosure. Detailed Implementation
[0039] The present disclosure is described below based on embodiments; however, it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.
[0040] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."
[0041] In a specific embodiment of this disclosure, the method for determining the polymer viscosity-concentration parameter can be implemented through the following technical solution, the specific steps of which are: Step S10: Obtain the viscosity-concentration relationship curve of the polymer solution in the target block and the effective salt concentration of the polymer through indoor experiments; Step S20: Establish a mathematical model for calculating the polymer solution viscosity-concentration relationship parameter based on the nonlinear least squares method; Step S30: Based on the mathematical model, calculate the viscosity-concentration relationship parameter A of the polymer solution in the target block using the experimental data of the polymer solution viscosity-concentration relationship and the effective salt concentration of the polymer. p1 A p2 A p3 and S p .
[0042] The following provides a detailed explanation of each of the above steps.
[0043] Step S10: Obtain the viscosity-concentration relationship curve of the polymer solution in the target block and the effective salt concentration of the polymer through indoor experiments, as detailed below:
[0044] 1. Conduct laboratory experiments based on the polymer used in the target area, and obtain the viscosity-concentration relationship curve of the polymer solution determined in the laboratory experiments. The specific steps of the laboratory experiments are as follows:
[0045] 1) Measure the solid content S of the polymer sample;
[0046] 2) Weigh (2 / 5)g of sample, accurate to 0.0001g;
[0047] 3) Weigh (400-2 / S) g of standard saline or on-site water into a 1000 mL beaker, accurate to 0.01 g;
[0048] 4) Adjust the speed of the mechanical stirrer to (500±20) r / min to form a vortex in the water. Slowly and evenly sprinkle the sample into the shoulder of the vortex within 30s. Stir for 2 hours and let stand for 2 hours. At this time, the mass concentration of the solution is 0.5%.
[0049] 5) Weigh 4.00g, 8.00g, 12.00g, 16.00g, 20.00g, 24.00g, 28.00g, 32.00g, 36.00g, and 40.00g of polymer solution into 250mL beakers respectively;
[0050] 6) Add standard saline or fresh water to each beaker in step 5 to a final volume of 100.00g;
[0051] 7) Add the rotor to each beaker and stir on a magnetic stirrer for 30 minutes to prepare a polymer sample solution;
[0052] 8) Set the constant temperature water bath to the formation temperature, turn on the Brookfield viscometer, connect the rotor to the viscometer, set the rotation speed to 6 r / min, measure 17 mL of sample solution and transfer it into the measuring cylinder, install it into the viscometer, and start the test after the constant temperature is maintained for 10 min. Read the viscosity value after the displayed value is relatively stable.
[0053] 9) Plot a graph with polymer solution concentration on the x-axis and polymer solution viscosity on the y-axis.
[0054] 2. Based on the concentrations of anions and cations in the prepared water determined by indoor experiments, the effective salt concentration of the polymer is calculated. The calculation method is as follows:
[0055] The effective salt concentration of the polymer is calculated based on the concentrations of anions and cations in the injection water. The anion concentration used is the chloride ion concentration, and the cation concentration is the sum of the calcium and magnesium ion concentrations. The formula for calculating the effective salt concentration of the polymer is as follows:
[0056] C SEP =C 40 +6.5*C 50 (1)
[0057] Among them, C 40 To adjust the concentration of anions in the water, C 50 This refers to the cation concentration in the prepared water.
[0058] Step S20: Based on the polymer solution viscosity-concentration relationship curve and the effective salt content of the polymer determined by indoor experiments, a mathematical model for calculating the polymer solution viscosity-concentration parameters is established using the nonlinear least squares method. The specific process is as follows:
[0059] 1) Obtain the viscosity-concentration relationship equation of the polymer solution at zero shear rate:
[0060] In this field, the viscosity of a polymer solution at zero shear rate is... It is the concentration C of the polymer solution. p and salt content C SEP The function is represented by the following function:
[0061]
[0062] Among them, C p The concentration of the polymer in the solution; μ w C is the viscosity of the aqueous phase. SEP This represents the effective salt concentration of the polymer. A is the viscosity of the polymer solution at zero shear rate. p1 A p2 A p3 and S p This refers to the viscosity-concentration parameter of the polymer solution.
[0063] The purpose of this disclosed method is to determine the viscosity-concentration parameter A of the polymer solution. p1 A p2 A p3 and S p .
[0064] 2) In the above formula (2), A p1 A p2 A p3 and S p These are the nonlinear fitting coefficients, and the general method for determining the fitting coefficients in a nonlinear function is the nonlinear least squares method. Specifically, first, an initial value is given to the fitting coefficients, and then, based on the principle of the nonlinear least squares method, a mathematical model for parameter calculation is established:
[0065]
[0066] in, The viscosity of the zero-shear rate polymer solution was determined in an indoor experiment.
[0067] Step S30: Based on the mathematical model, using experimental data on the viscosity-concentration relationship of the polymer solution and the effective salt content of the polymer, calculate the viscosity-concentration relationship parameter A of the polymer solution in the target block. p1 A p2 A p3 and S p The calculation method is as follows:
[0068] 1) Using the chemical flooding numerical simulation software CHEMEOR, the partial derivatives of both sides of the equation with respect to the fitting coefficients are equal to zero. A can be obtained by solving the system of four linear equations. p1 A p2 A p3 and S p .
[0069] 2) Compare the calculated polymer solution viscosity-concentration data with the polymer solution viscosity-concentration data measured in the laboratory to determine the accuracy of the parameter calculation.
[0070] In a specific embodiment of this disclosure, the method for predicting the development effect of a target block using the polymer flooding viscosity-concentration parameter determination method includes the following steps:
[0071] 1. In the chemical flooding numerical simulation software CHEMEOR, set the polymer solution viscosity-concentration parameters as follows:
[0072] The calculated polymer solution viscosity-concentration parameter A p1 A p2 A p3 and Sp The parameters are entered into the chemical flooding numerical simulation software CHEMEOR to provide basic parameters for describing the polymer viscous displacement mechanism.
[0073] 2. The polymer flooding history of the target block was fitted using the chemical flooding numerical simulation software CHEMEOR, as detailed below:
[0074] The polymer flooding process parameters are set based on the dynamic data of the target block's polymer flooding mine. These parameters mainly include the injection rate, injection time, polymer molecular weight, and polymer concentration during the polymer injection stage. However, the specific data for the injection rate, injection time, polymer molecular weight, and polymer concentration during the polymer flooding stage are not limited to the values in this patent and should be customized based on the actual data from the mine.
[0075] The polymer flooding history of the target block was fitted using chemical flooding numerical simulation software. The fitting indices included instantaneous oil production, instantaneous water production, and water cut of the entire area.
[0076] 3. Based on historical data matching, predict the development effect of the target block to provide technical support for evaluating the polymer-driven effect, as detailed below:
[0077] Based on the good results achieved in historical fitting, the development effect prediction of the target block is carried out, and the recovery degree of polymer flooding stage is calculated when the comprehensive water cut of the whole area reaches 98%.
[0078] Example
[0079] This embodiment takes a target block as an example and calculates the polymer flooding viscosity-concentration parameters for that target block, such as... Figure 1 As shown, the calculation process includes the following steps:
[0080] 1. Based on the polymer used in the target area, the viscosity-concentration relationship curve of the polymer solution was determined in the laboratory:
[0081] The laboratory determined the polymer viscosities at polymer solution concentrations of 800 mg / L, 1000 mg / L, 1200 mg / L, 1400 mg / L, 1600 mg / L, 1800 mg / L, 2000 mg / L, 2200 mg / L, and 2400 mg / L, as shown in Table 1. Figure 2 As shown:
[0082] Table 1. Viscosity-concentration data of polymer solutions measured in the laboratory.
[0083]
[0084] Based on the data in Table 1, a plot was created with polymer solution concentration on the x-axis and polymer solution viscosity on the y-axis. Figure 2 The viscosity-concentration relationship curve of the polymer solution is shown.
[0085] 2. Calculate the effective salt concentration of the polymer based on the anion and cation concentrations in the prepared water as determined in the laboratory:
[0086] Laboratory tests showed that the concentration of chloride ions in the prepared water was 1451.2 mg / L, the concentration of calcium ions was 76.8 mg / L, and the concentration of magnesium ions was 3.5 mg / L.
[0087] First, calculate the anion concentration C. 40 That is, to calculate the chloride ion concentration:
[0088] C 40 =1451.2 / (1000*35.5)*1=0.0408meq / ml;
[0089] Then calculate the cation content C. 50 That is, calculate the sum of the calcium ion concentration and the magnesium ion concentration:
[0090] C 50 =76.8 / (1000*40)*2+3.5 / (1000*24)*2=0.0041meq / ml;
[0091] Finally, the effective salt concentration of the compound was calculated:
[0092] C SEP =C 40 +6.5*C 50 =0.0408+6.5*0.0041=0.0677meq / ml.
[0093] 3. Based on the polymer solution viscosity-concentration relationship curve and the effective salt content of the polymer determined in the laboratory, a mathematical model for calculating the polymer solution viscosity-concentration parameter is established using the nonlinear least squares method:
[0094]
[0095] in, The viscosity of the zero-shear rate polymer solution was determined in an indoor experiment.
[0096] 4. Import the laboratory-measured polymer solution viscosity-concentration curve and the calculated effective salt concentration of the polymer into the chemical flooding numerical simulation software CHEMEOR. Input the basic parameters, including an aqueous phase viscosity of 0.6 mPa·s, a polymer viscosity loss coefficient (polymer solution viscosity loss caused by polymer flooding injection, pipelines, and perforations) of 0.5, and the four parameters A required for the nonlinear least squares method. p1 A p2 A p3 and S pThe initial values for the iterations are 5, 100, 100, and -0.531.
[0097] Based on the above data, the polymer solution viscosity-concentration parameter A was calculated. p1 A p2 A p3 and S p The values are 13.6, 197, 866, and -0.65, respectively. Figure 3 As shown.
[0098] 5. Compare the calculated polymer solution viscosity with the laboratory-measured polymer solution viscosity using software, as shown in Table 2. Figure 4 As shown, the accuracy of parameter calculation is determined based on the relative error between the measured and calculated values.
[0099] Table 2 Comparison of Measured and Calculated Polymer Solution Viscosity-Concentration Data
[0100]
[0101] From Table 2 and Figure 4 It can be seen that the maximum relative error between the calculated polymer solution viscosity value and the measured polymer solution viscosity value is about 1%, indicating that the viscosity-concentration parameter of the polymer solution calculated by this method has high accuracy.
[0102] 6. In the chemical flooding numerical simulation software CHEMEOR, set the polymer solution viscosity-concentration parameter A obtained in step 5. p1 A p2 A p3 and S p The aim is to provide basic parameters for the polymer viscous displacement mechanism.
[0103] 7. Apply the chemical flooding numerical simulation software CHEMEOR to fit the polymer flooding history of the target block:
[0104] The parameters for the polymer flooding process are set based on the dynamic data of the target block polymer flooding mine: mainly including the injection rate, injection time, polymer molecular weight, and polymer concentration in the injection stage. However, the specific data for the injection rate, injection time, polymer molecular weight, and polymer concentration in the injection stage are not limited to the values in this patent and should be customized according to the actual data of the mine.
[0105] In this embodiment, the polymerization stage injection rate is 0.2 PV / a, the polymerization time is 5 years, the polymer molecular weight is 25 million, and the polymer concentration is 2000 mg / L.
[0106] The polymer flooding history of the target block was fitted using chemical flooding numerical simulation software. In this embodiment, the fitting indices included instantaneous oil production, instantaneous water production, and water cut across the entire area, yielding the following results. Figure 5 The moisture content fitting curve for the target block is shown.
[0107] 8. Based on the good results obtained from historical fitting, predict the development effect of the target block and obtain... Figure 6 The development effect prediction curve of the target block shown indicates that the recovery rate of polymer flooding stage is 14% when the overall water content of the entire area reaches 98%.
[0108] In this embodiment, the viscosity-concentration relationship curve of the polymer solution, as determined in the laboratory, is preferably used. Based on the nonlinear least squares method, a mathematical model for calculating the viscosity-concentration parameter of the polymer solution is established, and a visual interface for parameter calculation is developed. By simply inputting the experimental data of the viscosity-concentration relationship of the polymer solution, the effective salt content of the polymer, and other relevant parameters into the interface, the viscosity-concentration parameter A of the polymer solution can be automatically calculated. p1 A p2 A p3 and S p .
[0109] Verification through examples shows that the polymer flooding viscosity-concentration parameter calculation method of this application has high practical value, improves the calculation speed and accuracy of polymer solution viscosity-concentration parameters, and provides basic parameters for describing the viscous oil displacement mechanism through polymer flooding numerical simulation.
[0110] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical applications, or technical improvements to the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.
Claims
1. A method for determining the viscosity-concentration relationship parameter of a polymer solution, characterized in that, include: Viscosity-concentration curves and effective salt concentrations of the polymer solution in the target block were obtained through indoor experiments. A mathematical model for calculating the viscosity-concentration relationship parameters of the polymer solution was established using the nonlinear least squares method. Based on this mathematical model, the viscosity-concentration relationship parameter A of the polymer solution in the target block was calculated using the experimental data and the effective salt concentrations of the polymer solution. p1 A p2 A p3 and S p .
2. The method for determining the viscosity-concentration relationship parameter of a polymer solution according to claim 1, characterized in that, The mathematical model for calculating the viscosity-concentration parameter of the polymer solution is: in, The viscosity of the polymer solution at zero shear rate. The viscosity of the zero-shear rate polymer solution was determined in an indoor experiment.
3. The method for determining the viscosity-concentration relationship parameter of a polymer solution according to claim 2, characterized in that: Based on the fact that the partial derivatives of both sides of the mathematical model with respect to the fitting coefficients are zero, the viscosity-concentration parameter A of the polymer solution in the target block is calculated by solving a system of four linear equations. p1 A p2 A p3 and S p .
4. The method for determining the viscosity-concentration relationship parameter of a polymer solution according to any one of claims 1-3, characterized in that, The formula for calculating the effective salt concentration of the polymer is as follows: C SEP =C 40 +6.5*C 50 ; Among them, C 40 To determine the anion concentration in the water, the chloride ion concentration is used; C 50 The cation concentration in the water is calculated by summing the calcium ion concentration and the magnesium ion concentration.
5. The method for determining the viscosity-concentration relationship parameter of a polymer solution according to claim 4, characterized in that, Also includes: Determine the accuracy of parameter calculations; The determination method involves comparing the calculated viscosity of the same polymer solution with the results of indoor experimental measurements. The formula for calculating the viscosity of the polymer solution is: Among them, C p The concentration of the polymer in the solution; μ w C is the viscosity of the aqueous phase. SEP This represents the effective salt concentration of the polymer.
6. The application of the method for determining the viscosity-concentration relationship parameter of the polymer solution according to any one of claims 1-5 in predicting the development effect of the target block.
7. The application according to claim 6, characterized in that: The viscosity-concentration relationship parameters of the polymer solution calculated by the determination method described in any one of claims 1-5 are entered into the chemical flooding numerical simulation software; Set the parameters for the polymer drive process based on the dynamic data of the target block polymer drive mining farm; The polymer flooding history of the target block was fitted using the chemical flooding numerical simulation software. Based on the good results achieved in the history fitting, the development effect of the target block was predicted.
8. The application according to claim 7, characterized in that: The dynamic data of the target block polymer flooding mine includes the injection rate, injection time, polymer molecular weight, and polymer concentration during the polymer injection stage.
9. The application according to claim 7 or 8, characterized in that: The historical fitting indices include instantaneous oil production, instantaneous water production, and water cut for the entire region.
10. The application according to claim 9, characterized in that: The historical data was fitted using CHEMEOR chemical flooding numerical simulation software.