An oil displacement agent with both tension and adhesion reduction functions and its design method and application

Abstract

The present invention provides an oil displacement agent having the functions of reducing tension and adhesion work, and a design method and application thereof, belonging to the technical field of oil and gas field development. The present invention first establishes a heavy oil molecular simulation model based on the properties of heavy oil in the target oil reservoir, and then uses molecular dynamics to select lipophilic and hydrophilic compounds, and then designs an oil displacement agent. The method of the present invention greatly reduces the experimental workload and experimental cost, the required period for determining the oil displacement agent is short, and the crude oil specificity of the oil displacement agent is enhanced; the designed oil displacement agent can effectively take into account the performance of reducing adhesion work and oil-water interfacial tension, and greatly improve the recovery rate of crude oil.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas field development, and in particular relates to an oil displacement agent with the functions of reducing tension and adhesion, and a design method and application thereof. Background Art

[0002] my country has abundant high-viscosity oil reservoirs. Currently, such reservoirs are mainly developed by water flooding and steam huff-and-puff, with high water content and low recovery rate. The adhesion work between high-viscosity crude oil and rock is high, and the remaining oil adhering to the rock surface in the displacement fluid affected area is difficult to start, the oil recovery efficiency is low, and the existing chemical oil recovery agents are not applicable. Therefore, it is urgent to develop new chemical oil recovery agents to efficiently start the remaining oil, significantly increase the recovery rate, and provide a guarantee for the stable production of crude oil in my country.

[0003] Studies have shown that oil displacement agents are enriched and penetrated at the oil-water interface, dispersing oil droplets by reducing the oil-water interfacial tension; they are enriched and adsorbed at the rock solid-liquid interface, stripping crude oil by reducing the adhesion work. The number of carbon chains and the number of ethylene oxide structural units are the main controlling factors for the ability of oil displacement agents to reduce adhesion work and permeate and disperse crude oil. Therefore, for the target reservoir crude oil, optimizing and determining the molecular structure of oil displacement agents such as the number of carbon chains and synthesizing oil displacement agents that have both tension and adhesion reduction is the key to improving oil recovery in high-viscosity reservoirs.

[0004] Traditionally, the design of oil displacement agents relies on indoor experiments, which involves compounding different proportions of different lipophilic and hydrophilic compounds and screening them based on synthetic sample performance tests. This method has unclear understanding of the microscopic mechanism, large experimental workload, long cycle, high cost, and is not very targeted to crude oil. Summary of the invention

[0005] In view of the deficiencies of the prior art, the present invention provides an oil displacement agent that has the functions of reducing tension and adhesion work, and a design method and application thereof. The present invention first establishes a heavy oil molecular simulation model based on the properties of the target reservoir heavy oil, and then uses molecular dynamics to select lipophilic and hydrophilic compounds, and then designs an oil displacement agent. The method of the present invention greatly reduces the experimental workload and experimental cost, the required period for determining the oil displacement agent is short, and the crude oil specificity of the oil displacement agent is enhanced; the designed oil displacement agent can effectively take into account the performance of reducing adhesion work and oil-water interfacial tension, and greatly improve the recovery rate of crude oil.

[0006] The technical solution adopted by the present invention is:

[0007] A method for designing an oil displacement agent having both tension reduction and adhesion reduction functions, comprising the steps of:

[0008] (1) Establishment of a heavy oil molecular simulation model based on the properties of the target reservoir heavy oil

[0009] Analyze the properties of the target reservoir's heavy oil, including the percentage distribution of four components: saturates, aromatics, asphaltene and resins, and the percentage distribution of five elements: carbon, hydrogen, oxygen, nitrogen and sulfur;

[0010] Based on the properties of the target reservoir's heavy oil, molecular simulation software was used to construct an average molecular structure model of the four components of heavy oil, and then molecular dynamics methods were used to optimize it to obtain a heavy oil molecular simulation model;

[0011] (2) Prefer lipophilic compounds and hydrophilic compounds

[0012] The structural models of acrylic acid with different carbon chain lengths were constructed respectively; the molecular dynamics method was used to simulate the mixing energy between acrylic acid with different carbon chain lengths and saturated components respectively, and the acrylic acid with the lowest mixing energy was the preferred lipophilic compound;

[0013] The structural models of hydrophilic compounds containing hydrophilic groups such as phosphate, carboxyl, amide, amine, hydroxyl and alcoholamide are respectively constructed; the mixing energy of the above hydrophilic compounds with water is simulated by molecular dynamics method, and the hydrophilic compounds are ranked from small to large according to the mixing energy, and the top three hydrophilic compounds are the preferred hydrophilic compounds;

[0014] (3) Designing oil displacement agents that reduce tension and adhesion work

[0015] A molecule of the lipophilic compound determined in step (2) is connected to a molecule of the hydrophilic compound through a carbon-carbon single bond to construct a molecular structure model, and then mixed with the heavy oil molecular simulation model determined in step (1), and energy minimization optimization is performed using molecular simulation to calculate the adhesion work and interfacial tension of the mixed system. The hydrophilic compound and lipophilic compound corresponding to the lowest adhesion work and interfacial tension are the reaction raw materials for synthesizing the oil displacement agent, thereby designing an oil displacement agent with reduced tension and reduced adhesion work.

[0016] According to the present invention, in step (1), the molecular simulation software is Materials studio 2020, and the COMPASS force field and Forcite modules are selected to construct an average molecular structure model of the four components of the heavy oil according to the properties of the target reservoir heavy oil.

[0017] According to the present invention, in step (1), the molecular dynamics method is based on Materials studio 2020 molecular simulation software, and the NPT ensemble is selected for 200 ps molecular dynamics simulation, wherein the pressure is set to 5.0 MPa; then the NVT ensemble is selected for 3,000 ps molecular dynamics simulation, and the van der Waals force and electrostatic interaction in the simulation are both Atom Based method, with a cutoff distance of 12 Å, the temperature control method uses the Nose-Hoover-Langevin (NHL) method, the pressure control method uses the Berendsen method, and the simulation step size is 1.0 fs.

[0018] Preferably, in step (1), the molecular dynamics method is used to adjust the number of molecules in the average molecular structure model so that the errors between the percentage distribution of the four components and the percentage distribution of the five elements in the model and the percentage distribution of the four components and the percentage distribution of the five elements in the target reservoir heavy oil are less than 1%.

[0019] According to the present invention, in step (2), the acrylates with different carbon chain lengths refer to acrylates with ester groups with different carbon chain lengths; preferably, the carbon chain length is 2-20.

[0020] According to the present invention, in step (2), the molecular simulation software Materials studio 2020 is used to construct the acrylic acid structure model with different carbon chain lengths. Currently, the lipophilic group with better effect in the oil displacement agent used in the mine is the acrylic acid ester group.

[0021] According to the present invention, in step (2), the molecular dynamics method adopts the Forcite module in the molecular simulation software Materials studio2020.

[0022] According to the present invention, in step (2), the molecular simulation software Materials studio 2020 is used to construct a hydrophilic compound structure model. The hydrophilic compound is a hydrophilic compound containing a hydrophilic group and a double bond, which is determined according to the hydrophilic-lipophilic balance and the application conditions of the mine. Preferably, the hydrophilic compound is a hydrophilic compound containing a propylene group and a hydrophilic group.

[0023] According to the present invention, in step (3), according to the reaction mechanism between double bonds, a molecule of lipophilic compound and a molecule of hydrophilic compound are connected via a carbon-carbon single bond and a molecular structure model is constructed.

[0024] According to the present invention, in step (3), the molecular structure model is constructed using the molecular simulation software Materials studio 2020.

[0025] According to the present invention, in step (3), the molecular simulation for energy minimization optimization is performed using the molecular simulation software Materials studio 2020, which can calculate the interaction energy between the heavy oil molecules and the solid wall. The greater the interaction energy, the greater the adhesion work between the heavy oil molecules and the solid wall. After adding the oil displacement agent molecules, the interaction energy between the heavy oil molecules and the solid wall can be reduced. The reduction in the interaction energy reflects the reduction ratio of the adhesion work.

[0026] According to the present invention, in step (3), after determining the reaction raw materials for synthesizing the oil-displacing agent, the oil-displacing agent with reduced tension and reduced adhesion work is obtained through conventional optimization experiments in combination with the prior art. Preferably, the preparation method of the oil-displacing agent with reduced tension and reduced adhesion work comprises the steps of: dissolving a hydrophilic compound in a sodium hydroxide aqueous solution with a pH value of 9, adding a lipophilic compound, and mixing thoroughly; dropping an initiator, and reacting under the protection of a protective gas; then adding the resulting reaction solution to methanol, filtering, and drying to obtain the oil-displacing agent with reduced tension and reduced adhesion work. The specific experimental conditions are obtained through conventional optimization experiments.

[0027] The technical features and beneficial effects of the present invention are:

[0028] 1. The present invention first establishes a molecular simulation model of heavy oil based on the properties of heavy oil in the target reservoir, then uses molecular dynamics to select lipophilic and hydrophilic compounds, and then designs an oil-displacing agent, and calculates the reduction of adhesion work and interfacial tension through molecular simulation software, thereby finally determining a tension-reducing and adhesion-reducing oil-displacing agent suitable for a specific crude oil. The method of the present invention avoids the problems of unclear microscopic mechanism, large experimental workload, high experimental cost, long cycle, poor crude oil targeting, etc. faced by traditional screening of synthetic oil-displacing agents based on experimental testing methods, greatly reduces the experimental workload and experimental cost, and the required cycle for determining the molecular structure of the oil-displacing agent is short, which enhances the crude oil targeting of the oil-displacing agent.

[0029] 2. In order to solve the problem of high adhesion work between high-viscosity crude oil and rock and difficulty in starting, the present invention changes the research and development idea of ​​oil-displacing agent from the traditional "focusing on oil-water interface" to "giving equal importance to oil-water and solid-liquid interfaces". By optimizing hydrophilic compounds and lipophilic compounds, it is achieved that the oil-water interfacial tension is reduced while the adhesion work of high-viscosity crude oil is greatly reduced, providing an effective oil-displacing agent for greatly improving the recovery rate of crude oil in high-viscosity reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The mixing energy simulation results corresponding to different acrylate carbon chain lengths in Example 1;

[0031] Figure 2 are the mixing energy simulation results corresponding to different hydrophilic groups in Example 1;

[0032] Figure 3The simulation results of reducing adhesion work corresponding to different oil displacement agent molecular structures in Example 1;

[0033] Figure 4 This is a real picture of the oil washing effect of the tension-reducing and adhesion-reducing oil displacement agent synthesized in the test example on heavy oil.

[0034] Figure 5 This is a physical picture of the oil washing effect of traditional petroleum sulfonate on heavy oil in the test example. DETAILED DESCRIPTION

[0035] In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, further detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0036] The methods described in the examples are all existing methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.

[0037] Example 1

[0038] A method for designing an oil displacement agent having both tension reduction and adhesion reduction functions, comprising the following steps:

[0039] (1) Establishment of a heavy oil molecular simulation model based on the properties of the target reservoir heavy oil

[0040] The heavy oil sample was taken from a production well in a block of Shengli Oilfield with a viscosity of 800mPa.s. Based on the heavy oil component analysis, the percentage distribution of four components, namely saturated fraction, aromatic fraction, asphaltene and colloid, as well as the percentage distribution of five elements, namely carbon, hydrogen, oxygen, nitrogen and sulfur, were statistically analyzed. The statistical results are shown in Table 1.

[0041] Table 1 Statistical results of components and element percentages of heavy oil samples

[0042]

[0043] Based on the results of heavy oil property analysis, the molecular simulation software (Materials studio 2020) was used to construct the average molecular structure model of the four components of heavy oil (COMPASS force field and Forcite module were selected). Then the molecular dynamics method was used (based on Materialsstudio 2020 molecular simulation software, the NPT ensemble was selected for 200 ps molecular dynamics simulation, in which the pressure was set to 5.0 MPa. Then the NVT ensemble was selected for 3 000 ps molecular dynamics simulation, and the van der Waals force and electrostatic interaction in the simulation were both Atom Based method, with a cutoff distance of 12Å, the temperature control method used the Nose-Hoover-Langevin (NHL) method, the pressure control method used the Berendsen method, and the simulation step size was 1.0 fs) to adjust the number of molecules in the average molecular structure model, so that the percentage distribution of the four components and the percentage distribution of the five elements in the model and the percentage distribution of the four components and the percentage distribution of the five elements in the target reservoir heavy oil were less than 1%, and the molecular simulation model of heavy oil was obtained.

[0044] The error statistics of the percentage distribution of the four components and the percentage distribution of the five elements in the constructed heavy oil molecular simulation model and the percentage distribution of the four components and the percentage distribution of the five elements in the heavy oil sample are shown in Table 2. The maximum error is 0.5%, which is less than 1%.

[0045] Table 2 Component and element percentages in the heavy oil molecular simulation model and the error statistics compared with the real sample

[0046]

[0047] (2) Prefer lipophilic compounds and hydrophilic compounds

[0048] The molecular simulation software Materials studio 2020 was used to construct the structural models of acrylic resins with different carbon chain lengths (carbon chain length 2-20). The molecular dynamics method (using the Forcite module in the molecular simulation software Materials studio 2020) was used to simulate the mixing energy between saturated molecules and acrylic resins with different carbon chain lengths. The simulation results are shown in the figure below. Figure 1 The carbon chain length that can obtain the lowest mixing energy is selected. In this embodiment, the carbon chain length is 18, that is, acrylic acid ester with a carbon chain length of 18 is used as the lipophilic compound.

[0049] The molecular simulation software Materials studio 2020 was used to construct the structural models of hydrophilic compounds containing hydrophilic groups such as phosphate, carboxyl, amide, amine, hydroxyl, and alcohol amide. Considering the hydrophilic-lipophilic balance and the application experience of the mine, the above hydrophilic compounds were selected from allyl dimethyl phosphate (corresponding to phosphate), acrylic acid (corresponding to carboxyl), 2-acrylamide-2-methylpropanesulfonic acid (corresponding to amide), allylamine (corresponding to amine), 2-propylene-1-ol (corresponding to hydroxyl) and N-hydroxymethyl acrylamide (corresponding to alcohol amide). The molecular dynamics method (using the Forcite module in the molecular simulation software Materials studio 2020) was used to simulate the mixing energy of the above hydrophilic compounds with water. The simulation results are shown in the figure. Figure 2 As shown. The mixing energy is ranked from small to large, which is hydroxyl, amide, amine, carboxyl, alcohol amide, and phosphate. The top three groups, hydroxyl, amide, and amine, i.e., hydrophilic compounds, are 2-propylene-1-ol, 2-acrylamide-2-methylpropanesulfonic acid, and allylamine.

[0050] (3) Designing the molecular structure of oil displacement agents that reduce tension and adhesion

[0051] According to the reaction mechanism of double bonds and double bonds, a molecule of the lipophilic compound determined in step (2) is connected to a molecule of the hydrophilic compound through a carbon-carbon single bond, and a molecular structure model is constructed using the molecular simulation software Materials studio 2020. Then it is mixed with the heavy oil molecular simulation model determined in step (1), and energy minimization optimization is performed using molecular simulation (molecular simulation software Materials studio 2020) to calculate the adhesion work and interfacial tension of the mixed system. The calculation results are shown in the figure. Figure 3 The hydrophilic compound and lipophilic compound with the lowest adhesion work and interfacial tension are selected as the reaction raw materials for synthesizing the oil displacement agent. In this embodiment, octadecyl acrylate and 2-acrylamide-2-methylpropanesulfonic acid are selected.

[0052] In combination with the prior art, an oil displacement agent for reducing tension and adhesion work is obtained through conventional optimization experiments, and the preparation method thereof comprises the steps of:

[0053] 1.5 g of 2-acrylamide-2-methylpropanesulfonic acid was dissolved in 20.0 mL of sodium hydroxide aqueous solution with a pH value of 9, and the mixture was placed in a flask equipped with a condenser, a thermometer and a stirring device. Then, 4.0 g of octadecyl acrylate was added. After stirring evenly, nitrogen was introduced to replace the air for 20 min. 2.0 mL of initiator azobisisobutyronitrile was added dropwise using a constant pressure dropping funnel at a constant temperature of 80°C. The mixture was stirred for 3.5 h in a nitrogen atmosphere at 80°C to initiate the reaction. After that, the temperature was raised to 100°C. After stirring for 7.0 h in a nitrogen atmosphere, the reaction solution was added into methanol, the solid was precipitated, filtered, and vacuum dried at 70°C for 3 h to obtain a tension-reducing and adhesion-reducing oil displacement agent.

[0054] Test example

[0055] 20 ml of heavy oil with a viscosity of 800 mPa.s (heavy oil used in Example 1) was mixed evenly with 80 g of quartz sand and added to a beaker, and aged at a constant temperature of 60°C for 7 days. The aged oil sand mixture was evenly distributed and placed in beakers ① and ② respectively. Then, 450 mL of an aqueous solution of the oil displacement agent prepared in Example 1 with a mass fraction of 0.4 wt% was added to beaker ①, and 450 mL of an aqueous solution of petroleum sulfonate commonly used in mines with a mass fraction of 0.4 wt% was added to beaker ②. Both beakers were left to stand at a constant temperature of 60°C for 48 hours.

[0056] The mixed solution in beaker ① is shown in the following figure: Figure 4 As shown in the figure, the solution in the beaker turns dark black, indicating that the high-viscosity crude oil adhering to the surface of the quartz sand can be washed off after adding the oil displacement agent solution. The interfacial tension of the oil-water phase is tested by an interfacial tension meter, which is 4.3*10 -3 mN / m, and after further separation of oil and water from the mixed solution in the beaker, the volume of the heavy oil was measured to be 3.8 mL, that is, the oil washing rate was 38%.

[0057] The mixed solution in beaker ② is shown in the photo Figure 5 As shown in the figure, the solution in the beaker turns light brown, indicating that only a small part of the high-viscosity crude oil adhering to the surface of the quartz sand can be washed off after the addition of the petroleum sulfonate solution. The interfacial tension of the oil-water phase is tested by an interfacial tension meter, which is 1.9*10 -2 mN / m, after the mixed solution in the beaker was separated into oil and water, the volume of the heavy oil was measured to be 1.0 mL, that is, the oil washing rate was 10%.

[0058] By comparing the oil washing effects in beaker ① and beaker ②, it can be seen that, compared with the petroleum sulfonates commonly used in mines, the oil displacement agent determined by the present invention can achieve a higher oil washing rate while achieving ultra-low interfacial tension.

[0059] From the above, the method of the present invention can accurately, effectively and quickly design an oil displacement agent structure for specific heavy oil; it has been verified that the obtained oil displacement agent can effectively reduce the oil-water interfacial tension and the solid-liquid interface adhesion work, and greatly improve the oil washing rate and crude oil recovery rate.

Claims

1. A design method for an oil displacement agent having both tension reduction and adhesion reduction functions, characterized in that: Includes steps: (1) Establish a heavy oil molecular simulation model based on the properties of the target reservoir heavy oil: Analyze the properties of the target reservoir's heavy oil, including the percentage distribution of four components: saturates, aromatics, asphaltene and resins, and the percentage distribution of five elements: carbon, hydrogen, oxygen, nitrogen and sulfur; Based on the properties of the target reservoir's heavy oil, molecular simulation software was used to construct an average molecular structure model of the four components of heavy oil, and then molecular dynamics methods were used to optimize it to obtain a heavy oil molecular simulation model; (2) Preferred lipophilic compounds and hydrophilic compounds: The structural models of acrylates with different carbon chain lengths were constructed respectively; the molecular dynamics method was used to simulate the mixing energy between acrylates with different carbon chain lengths and saturated components respectively, and the acrylate with the lowest mixing energy was the preferred lipophilic compound; The hydrophilic compound is a hydrophilic compound containing an propylene group and a hydrophilic group; structural models of hydrophilic compounds containing hydrophilic groups such as phosphate group, carboxyl group, amide group, amine group, hydroxyl group and alcohol amide group are respectively constructed; the molecular dynamics method is used to simulate the mixing energy of the above hydrophilic compounds with water, and the hydrophilic compounds are sorted from small to large according to the mixing energy, and the top three hydrophilic compounds are the preferred hydrophilic compounds; (3) Designing oil displacement agents that reduce tension and adhesion work: A molecule of the oleophilic compound determined in step (2) is connected to a molecule of the hydrophilic compound through a carbon-carbon single bond to construct a molecular structure model, and then mixed with the heavy oil molecular simulation model determined in step (1), and energy minimization optimization is performed using molecular simulation to calculate the adhesion work and interfacial tension of the mixed system. The hydrophilic compound and oleophilic compound corresponding to the lowest adhesion work and interfacial tension are the reaction raw materials for synthesizing the oil displacement agent, thereby designing an oil displacement agent with reduced tension and reduced adhesion work; The preparation method of the oil displacement agent for reducing tension and adhesion work comprises the steps of: dissolving a hydrophilic compound in a sodium hydroxide aqueous solution with a pH value of 9, adding a lipophilic compound, and fully mixing; dripping an initiator, and reacting under the protection of a protective gas; then adding the obtained reaction solution into methanol, filtering, and drying to obtain the oil displacement agent for reducing tension and adhesion work.

2. The design method of the oil displacing agent having the functions of reducing tension and adhesion according to claim 1, characterized in that: In step (1), the molecular dynamics method is to select the NPT ensemble for a 200 ps molecular dynamics simulation, in which the pressure is set to 5.0 MPa; then the NVT ensemble is selected for a 3 000 ps molecular dynamics simulation. In the simulation, the van der Waals force and electrostatic interaction are both simulated using the Atom Based method with a cutoff distance of 12 Å. The temperature control method uses the Nose-Hoover-Langevin (NHL) method, the pressure control method uses the Berendsen method, and the simulation step size is 1.0 fs.

3. The design method of the oil displacing agent having the functions of reducing tension and adhesion according to claim 1, characterized in that: In step (1), the molecular dynamics method is used to adjust the number of molecules in the average molecular structure model so that the errors between the percentage distribution of the four components and the percentage distribution of the five elements in the model and the percentage distribution of the four components and the percentage distribution of the five elements in the target reservoir heavy oil are less than 1%.

4. The design method of the oil displacing agent having the functions of reducing tension and adhesion according to claim 1, characterized in that: In step (2), the carbon chain length of the acrylic esters with different carbon chain lengths is 2-20.

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