Simulation method for predicting arrangement of betaine surfactant molecules on thickened oil water interface

Abstract

The invention provides a simulation method for predicting arrangement of betaine surfactant molecules on a thickened oil water interface, which comprises the following steps of: establishing a carboxylate and sulfonate betaine surfactant molecular model through crude oil analysis and model construction of an offshore thickened oil field; molecular dynamics simulation is used for researching migration and distribution rules of different types of betaine surfactants on the heavy oil water interface. The method has the beneficial effects that a carboxylate and sulfonate betaine surfactant molecular model is established by analyzing crude oil in a heavy oil field and constructing the model, migration and distribution rules of different types of betaine surfactants on a heavy oil water interface are studied by utilizing molecular dynamics simulation, the applicability of the betaine surfactants is evaluated, and the application prospect is wide. And the interaction and extraction action mechanism of the betaine surfactant and the crude oil component is further analyzed, and the model is reasonably analyzed to provide microcosmic molecular level interpretation of a macroscopic experiment result, so that theoretical guidance is provided for the molecular structure design of a surfactant system applicable to an offshore heavy oil field.

Description

Technical Field

[0001] The present invention relates to the technical field of surfactant oil-water interface and recovery for offshore chemical flooding, and more specifically to a simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water. Background Art

[0002] In view of the conditions of heavy oil reservoirs, further research is still needed on the properties of crude oil and process conditions, analyzing the structural characteristics of active components in heavy oil, revealing the interaction mechanism between crude oil and surfactants, and maximizing the ultra-low interfacial tension for heavy oil by adjusting the molecular structure of surfactants.

[0003] Betaine-based surfactant raw materials are green, cheap, high-performance, and can achieve ultra-low interfacial tension in a low concentration range. They also have good stability and reservoir adaptability, and excellent resistance to high temperature and high salinity. Therefore, the development and mechanism research of betaine-based surfactants suitable for offshore heavy oil conditions has important theoretical and practical significance for the development of new surfactant products and improving the effect of heavy oil development.

[0004] Through traditional experimental simulation, from indoor tests to field tests, it is currently difficult to explain the microscopic flow mechanism of the oil displacement process in underground reservoirs. Molecular simulation technology uses computers to simulate the structure and behavior of molecules at the atomic level, and then simulates various physical and chemical properties of molecular systems, which can provide physical quantities that cannot be measured by existing experiments in the studied system.

[0005] Therefore, molecular simulation technology can reveal the seepage mechanism of oil recovery at the microscopic scale, enrich the oil recovery flow theory system and oil field development oil recovery technology, provide a theoretical basis for improving oil and gas recovery, and provide guidance for the design of oil recovery agent molecules based on molecular simulation of oil recovery mechanism. Summary of the invention

[0006] The invention overcomes the deficiencies in the prior art and provides a simulation method for predicting the arrangement of betaine surfactant molecules at a heavy oil-water interface.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] The simulation method for predicting the arrangement of betaine surfactant molecules at the heavy oil-water interface includes the following specific steps:

[0009] S1. Construct the initial model, use the software to establish the oil molecule model and the betaine surfactant molecule model, use the software to optimize the geometric structure through quantum chemical calculation, obtain the full atomic structure charge parameters, and generate the corresponding force field parameters from the AMBER force field;

[0010] S2. Construct a heavy oil model. First, construct an 8×8×8nm 3 The heavy oil box is designed. According to the actual heavy oil component ratio of offshore oil fields, asphaltene, colloid and hydrocarbon are added in sequence. The heavy oil model is obtained by performing energy minimization program using the steepest descent method in molecular dynamics calculation software and molecular dynamics simulation processing under the NPT system.

[0011] S3. Construct a simulation system of heavy oil, water and betaine surfactant, and expand the heavy oil box to 8×8×16nm in the molecular dynamics calculation software 3 , and then insert betaine surfactant molecules and water molecules into the remaining space of the heavy oil box, and after completion, a system model of heavy oil, water and betaine surfactant is obtained;

[0012] S4. Molecular dynamics simulation of heavy oil, water and betaine surfactant system. In the molecular dynamics calculation software, the simulation system is first subjected to energy minimization using the steepest descent method, and then molecular dynamics simulation is performed under the NVT or NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state;

[0013] S5. Analysis of oil-water interface performance: By visualizing the three-phase system model of heavy oil, water and betaine surfactant in a stable state, the distribution characteristics of betaine surfactant molecules at the interface of heavy oil and water are analyzed, and the heavy oil and water interface characteristics of betaine surfactant molecules are evaluated using density distribution and solvent accessible surface area parameters.

[0014] In S1, the betaine surfactants include sulfonate betaine surfactants and carboxylate betaine surfactants. The sulfonate betaine surfactants include octaalkyldimethyl hydroxysulfonate, dodecyldimethyl hydroxysulfonate, hexadecyldimethyl hydroxysulfonate and hexacosyldimethyl hydroxysulfonate. The carboxylate betaine surfactants include octaalkyldimethyl hydroxycarboxylates, dodecyldimethyl hydroxycarboxylates, hexadecyldimethyl hydroxycarboxylates and hexacosyldimethyl hydroxycarboxylates.

[0015] In S1, the oil molecules include asphaltenes, colloids and hydrocarbons. The hydrocarbons include alkanes and aromatic hydrocarbons. The alkanes are n-octane and the aromatic hydrocarbons are toluene.

[0016] In S1, Gaussian software was used to establish the oil molecule model and the betaine surfactant molecule model, and the geometric structure was optimized through quantum chemical calculations to obtain the full-atom structure charge parameters, and the corresponding force field parameters were generated through the AMBER force field.

[0017] In S2, Packmol software was used to establish the initial model of heavy oil, and the heavy oil model was obtained by performing energy minimization program and molecular dynamics simulation through molecular dynamics calculation software GROMACS.

[0018] In S3, the box was expanded in the molecular dynamics calculation software GROMACS, and the betaine surfactant molecules and water molecules were inserted. The water molecules used the opc3 model.

[0019] In S4, the AMBER force field was selected in the molecular dynamics calculation software GROMACS to perform molecular dynamics calculations on the established simulation system of heavy oil, water and betaine surfactant.

[0020] The simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water according to claim 1 is characterized in that: in S5, molecular dynamics simulation visualization is performed by VMD software to analyze the arrangement characteristics of betaine surfactant molecules at the interface of heavy oil and water.

[0021] The beneficial effects of the present invention are:

[0022] The invention provides a simulation method for predicting the arrangement of betaine surfactant molecules at a heavy oil-water interface in an offshore oil field. The method comprises the following steps: by analyzing crude oil in the heavy oil field and constructing a model, establishing carboxylate and sulfonate betaine surfactant molecular models, using molecular dynamics simulation to study the migration and distribution laws of different types of betaine surfactants at a heavy oil-water interface, evaluating the applicability of the betaine surfactants, further analyzing the interaction and recovery mechanism between the betaine surfactants and crude oil components, providing a microscopic molecular level explanation of macroscopic experimental results, and providing theoretical guidance for the molecular structure design of a surfactant system applicable to offshore heavy oil fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a structural diagram of a heavy oil molecule in the present invention;

[0024] Figure 2 is a structural diagram of carboxylate and sulfonate betaine surfactant molecules in the present invention;

[0025] Figure 3 It is the equilibrium configuration and number density distribution diagram of the system of heavy oil, water and different types of betaine surfactants in the present invention;

[0026] Figure 4 It is a diagram showing the change in the simulated process of the solvent accessible surface area of ​​the heavy oil, water and different types of betaine surfactant systems in the present invention. DETAILED DESCRIPTION

[0027] Example 1

[0028] S1. Constructing the initial model: Using Gaussian software to build the oil molecule model and the octaalkyl dimethyl hydroxycarboxylate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry structure was optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters were generated from the AMBER force field.

[0029] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0030] In this embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules. Gel molecules, including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules. 1126 n-octane molecules and 522 toluene molecules are added in sequence. AMBER force field was selected in the molecular dynamics calculation software GROMACS, and the energy minimization program was performed on the established oil box using the steepest descent method. The energy convergence standard was 100 kJ / (mol·nm). A 5 ns molecular dynamics simulation was performed in the Isothermal-isobaricensemble system, i.e., the isothermal and isobaric system, hereinafter referred to as the NPT system. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Berendsen pressure bath with a time constant of 0.5 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 0.9 nm. After completion, a heavy oil model was obtained.

[0031] S3. Construction of simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in molecular dynamics calculation software GROMACS 3 Then, 35 octaalkyldimethylhydroxycarboxylate molecules were inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant was obtained.

[0032] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0033] S5. Analysis of oil-water interface performance: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using Visual Molecular Dynamics software (hereinafter referred to as VMD software) to analyze the arrangement characteristics of octaalkyl dimethyl hydroxycarboxylate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface characteristics of octaalkyl dimethyl hydroxycarboxylate, such as Figure 3 and Figure 4 shown.

[0034] Example 2

[0035] S1. Constructing the initial model: Using Gaussian software to construct the oil molecule model and the dodecyl dimethyl hydroxycarboxylate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0036] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0037] In this embodiment, asphaltene molecules were added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules; colloid molecules, including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. AMBER force field was selected in molecular dynamics calculation software GROMACS, and the energy minimization program was performed on the established oil box using the steepest descent method. The energy convergence standard was 100 kJ / (mol·nm). A 5 ns molecular dynamics simulation was performed under the NPT system. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Berendsen pressure bath with a time constant of 0.5 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was calculated using a truncation method with a truncation distance of 0.9 nm. After completion, a heavy oil model was obtained.

[0038] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3 , and then insert 35 dodecyl dimethyl hydroxycarboxylate molecules into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0039] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0040] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of dodecyl dimethyl hydroxycarboxylate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of dodecyl dimethyl hydroxycarboxylate, such as Figure 3 and Figure 4 shown.

[0041] Example 3

[0042] S1. Constructing the initial model: Using Gaussian software to build the oil molecule model and the hexadecyl dimethyl hydroxycarboxylate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0043] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0044] In the embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules; colloid molecules, including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0045] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3Then, 35 hexadecyl dimethyl hydroxycarboxylate molecules are inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0046] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0047] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of hexadecyl dimethyl hydroxycarboxylate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of hexadecyl dimethyl hydroxycarboxylate, such as Figure 3 and Figure 4 shown.

[0048] Example 4

[0049] S1. Constructing the initial model: Using Gaussian software to construct the oil molecule model and the hexadecyl dimethyl hydroxycarboxylate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0050] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0051] In the embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules; colloid molecules, including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0052] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3 Then, 35 hexadecyl dimethylhydroxycarboxylate molecules are inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0053] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0054] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of hexadecyl dimethyl hydroxycarboxylate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of hexadecyl dimethyl hydroxycarboxylate, such as Figure 3 and Figure 4 shown.

[0055] Example 5

[0056] S1. Constructing the initial model: Using Gaussian software to construct the oil molecule model and the octaalkyl dimethyl hydroxysulfonate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0057] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0058] In the embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules; colloid molecules, including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0059] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3Then, 35 octaalkyldimethylhydroxysulfonate molecules were inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant was obtained.

[0060] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0061] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of octaalkyl dimethyl hydroxysulfonate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of octaalkyl dimethyl hydroxysulfonate, such as Figure 3 and Figure 4 shown.

[0062] Example 6

[0063] S1. Construct the initial model: Use Gaussian software to build the oil molecule model and the dodecyl dimethyl hydroxysulfonate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0064] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0065] In the embodiment, asphaltene molecules, including 6 ASP1 molecules, 6 ASP2 molecules, and 6 ASP3 molecules, colloid molecules, including 35 RES1 molecules, 35 RES2 molecules, 35 RES3 molecules, 1126 n-octane molecules, and 522 toluene molecules are added in sequence. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0066] S3. Construction of simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in molecular dynamics calculation software GROMACS 3 , then insert 35 dodecyl dimethyl hydroxysulfonate molecules into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0067] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0068] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of dodecyl dimethyl hydroxysulfonate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of dodecyl dimethyl hydroxysulfonate, such as Figure 3 and Figure 4 shown.

[0069] Example 7

[0070] S1. Construct the initial model: Use Gaussian software to build the oil molecule model and the hexadecyl dimethyl hydroxysulfonate surfactant molecule model, the structure is as follows Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0071] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0072] In the embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, 6 ASP3 molecules, and colloid molecules; including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The Particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0073] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3Then, 35 hexadecyl dimethyl hydroxysulfonate molecules are inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0074] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0075] S5. Analysis of oil-water interface performance: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of hexadecyl dimethyl hydroxysulfonate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface characteristics of hexadecyl dimethyl hydroxysulfonate, such as Figure 3 and Figure 4 shown.

[0076] Example 8

[0077] S1. Constructing the initial model: Gaussian software was used to construct the oil molecule model and the hexadecyl dimethyl hydroxysulfonate surfactant molecule model, the structure of which is as follows: Figure 1 and Figure 2 As shown, the geometry is optimized by quantum chemical calculation using Gaussian software to obtain the all-atom structure charge parameters, and the corresponding force field parameters are generated from the AMBER force field.

[0078] S2. Construct heavy oil model: First construct 8×8×8nm in Packmol software 3 The heavy oil box is then used to determine the number of oil molecules based on the actual heavy oil component ratio in the offshore oil field.

[0079] In the embodiment, asphaltene molecules are added in sequence, including 6 ASP1 molecules, 6 ASP2 molecules, 6 ASP3 molecules, and colloid molecules; including 35 RES1 molecules, 35 RES2 molecules, and 35 RES3 molecules; 1126 n-octane molecules and 522 toluene molecules. Then, the AMBER force field is selected in the molecular dynamics calculation software GROMACS, and the energy minimization program is performed on the established oil box using the steepest descent method. The energy convergence standard is 100 kJ / (mol·nm). A 5ns molecular dynamics simulation is performed under the NPT system. During the simulation process, a Velocity-rescale heat bath with a time constant of 0.2ps and a Berendsen pressure bath with a time constant of 0.5ps are used to control the temperature and pressure of the system. At 1atm and 303K, the integration step is set to 2fs, and periodic boundary conditions are set for all directions of the system. The Particle-mesh Ewald method is used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction adopts a truncation method with a truncation distance of 0.9nm. After completion, a heavy oil model is obtained.

[0080] S3. Construction of the simulation system of heavy oil, water and betaine surfactant: Enlarging the box to 8×8×16nm in the molecular dynamics calculation software GROMACS 3 Then, 35 molecules of hexadecyl dimethyl hydroxysulfonate are inserted into the remaining space of the box, followed by water molecules. After completion, a simulation system model of heavy oil, water and betaine surfactant is obtained.

[0081] S4. Molecular dynamics simulation of the simulation system of heavy oil, water and betaine surfactant: In the molecular dynamics calculation software GROMACS, the simulation system was first subjected to energy minimization using the steepest descent method with an energy convergence criterion of 500 kJ / (mol·nm). Then, a 20 ns molecular dynamics simulation was performed under the NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state. During the simulation, a Velocity-rescale heat bath with a time constant of 0.2 ps and a Parrinello-rahman pressure bath with a time constant of 2.0 ps were used to control the temperature and pressure of the system. At 1 atm and 303 K, the integration step was set to 2 fs, and periodic boundary conditions were set for all directions of the system. The Particle-mesh Ewald method was used to calculate the electrostatic interaction, and the calculation of the van der Waals interaction was performed using a truncation method with a truncation distance of 1.4 nm.

[0082] S5. Analysis of oil-water interface properties: The three-phase system model of heavy oil, water and betaine surfactant in a stable state was visualized using VMD software to analyze the arrangement characteristics of hexadecyl dimethyl hydroxysulfonate molecules at the interface of heavy oil and water. The density distribution gmx density and solvent accessible surface area gmx sasa were used to evaluate the heavy oil and water interface properties of hexadecyl dimethyl hydroxysulfonate, such as Figure 3 and Figure 4 shown.

[0083] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water, characterized in that: The specific steps include: S1. Construct the initial model, use the software to establish the oil molecule model and the betaine surfactant molecule model, use the software to optimize the geometric structure through quantum chemical calculation, obtain the full atomic structure charge parameters, and generate the corresponding force field parameters from the AMBER force field; S2. Construct a heavy oil model. First, construct an 8×8×8nm 3 The heavy oil box is designed. According to the actual heavy oil component ratio of offshore oil fields, asphaltene, colloid and hydrocarbon are added in sequence. The heavy oil model is obtained by performing energy minimization program using the steepest descent method in molecular dynamics calculation software and molecular dynamics simulation processing under the NPT system. S3. Construct a simulation system of heavy oil, water and betaine surfactant, and expand the heavy oil box to 8×8×16nm in the molecular dynamics calculation software 3 , and then insert betaine surfactant molecules and water molecules into the remaining space of the heavy oil box, and after completion, a system model of heavy oil, water and betaine surfactant is obtained; S4. Molecular dynamics simulation of heavy oil, water and betaine surfactant system. In the molecular dynamics calculation software, the simulation system is first subjected to energy minimization using the steepest descent method, and then molecular dynamics simulation is performed under the NVT or NPT system to obtain a three-phase system model of heavy oil, water and betaine surfactant in a stable state; S5. Analysis of oil-water interface performance: By visualizing the three-phase system model of heavy oil, water and betaine surfactant in a stable state, the distribution characteristics of betaine surfactant molecules at the interface of heavy oil and water are analyzed, and the heavy oil and water interface characteristics of betaine surfactant molecules are evaluated using density distribution and solvent accessible surface area parameters.

2. The simulation method for predicting the arrangement of betaine surfactant molecules at the heavy oil-water interface according to claim 1, characterized in that: In S1, the betaine surfactants include sulfonate betaine surfactants and carboxylate betaine surfactants. The sulfonate betaine surfactants include octaalkyldimethyl hydroxysulfonate, dodecyldimethyl hydroxysulfonate, hexadecyldimethyl hydroxysulfonate and hexacosyldimethyl hydroxysulfonate. The carboxylate betaine surfactants include octaalkyldimethyl hydroxycarboxylates, dodecyldimethyl hydroxycarboxylates, hexadecyldimethyl hydroxycarboxylates and hexacosyldimethyl hydroxycarboxylates.

3. The simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water according to claim 1, characterized in that: In S1, the oil molecules include asphaltenes, colloids and hydrocarbons. The hydrocarbons include alkanes and aromatic hydrocarbons. The alkanes are n-octane and the aromatic hydrocarbons are toluene.

4. The simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water according to claim 1, characterized in that: In S1, Gaussian software was used to establish the oil molecule model and the betaine surfactant molecule model, and the geometric structure was optimized through quantum chemical calculations to obtain the full-atom structure charge parameters, and the corresponding force field parameters were generated through the AMBER force field.

5. The simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water according to claim 1, characterized in that: In S2, Packmol software was used to establish the initial model of heavy oil, and the heavy oil model was obtained by performing energy minimization program and molecular dynamics simulation through molecular dynamics calculation software GROMACS.

6. The simulation method for predicting the arrangement of betaine surfactant molecules at the interface of heavy oil and water according to claim 1, characterized in that: In S3, the box was expanded in the molecular dynamics calculation software GROMACS, and the betaine surfactant molecules and water molecules were inserted. The water molecules used the opc3 model.

7. The simulation method for predicting the arrangement of betaine surfactant molecules at the heavy oil-water interface according to claim 1, characterized in that: In S4, the AMBER force field was selected in the molecular dynamics calculation software GROMACS to perform molecular dynamics calculations on the established simulation system of heavy oil, water and betaine surfactant.

8. The simulation method for predicting the arrangement of betaine surfactant molecules at the heavy oil-water interface according to claim 1, characterized in that: In S5, molecular dynamics simulation visualization was performed using VMD software to analyze the arrangement characteristics of betaine surfactant molecules at the interface between heavy oil and water.

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