Oil displacement composition based on mixed alcohol amine as well as preparation method and application of oil displacement composition

Abstract

The invention relates to an oil displacement composition based on mixed alkylol amine and a preparation method and application thereof, and the method comprises the following steps: adding ethanediamine and diethanol amine into water to obtain an alkylol amine solution; and mixing the alcohol amine solution and the block type hydrophobic association polymer to form the oil displacement composition. According to the invention, bidentate chelation and strong basicity of ethidene diamine and hydrogen bond bridging and stable interface synergy of diethanol amine are utilized to replace a surfactant or a weak base system adopted in the prior art, and diethanol amine and ethidene diamine jointly promote hydrophobic block aggregation, so that the hydrophobic property of the surfactant is improved. The tackifying efficiency of the oil displacement composition can be effectively improved, and the critical association concentration (CAC) is reduced, so that high tackifying can be realized at low concentration.

Description

Technical Field

[0001] This invention relates to the field of chemical flooding for enhanced oil recovery, specifically to an oil displacement system based on mixed alkanolamines, its preparation method, and its application. Background Technology

[0002] The oil extraction process can be divided into the initial extraction stage, the water injection development stage, and the enhanced oil recovery stage. Among them, in the enhanced oil recovery (EOR) stage, specific displacement media are injected into the reservoir. By utilizing their physicochemical interaction with crude oil, the fluidity of crude oil is improved, the mobility ratio of the displacement media to crude oil is reduced, thereby effectively improving the displacement efficiency and recovery rate of crude oil.

[0003] Among existing Enhanced Oil Recovery (EOR) technologies, chemical flooding is the most commonly used method. Poly(petroleum sulfonate) ternary composite flooding technology is a widely applied chemical flooding technique. It uses a ternary system composed of partially hydrolyzed polyacrylamide (HPAM), petroleum sulfonate, and sodium carbonate / sodium bicarbonate. It synergistically improves oil washing efficiency through a triple mechanism of wettability reversal, reduction of oil-water interfacial tension (IFT), and mobility control. However, the three reagents have problems with chromatographic separation and electrostatic neutralization, long indoor commissioning cycles, and in field applications, fluctuations in formation temperature and salinity can easily cause IFT to degrade. rebounded to The above may lead to system failure; furthermore, weak bases such as sodium carbonate react with formation water. , The reaction produces precipitates, which cause high formation damage and maintenance costs, and also increase the total cost of the reagents.

[0004] Systems consisting of a single alkanolamine and a polymer, such as a system composed of diethanolamine (DEA) and partially hydrolyzed polyacrylamide (HPAM), utilize the weak basicity of the alkanolamine to adjust rock wettability, while the polymer controls flowability. This eliminates the need for surfactants and weak bases, reducing the compatibility difficulty of ternary systems. However, single alkanolamines and... , It can only form monodentate complexes, and is prone to hydroxyl salt precipitation at high salinity, making it unsuitable for medium- to high-salinity reservoirs. Moreover, single alkanolamines cannot maintain polymer stability, and the decrease in viscosity leads to a rapid decline in the mobility control capability of the displacement system. Furthermore, single alkanolamines have weak interfacial tension regulation capabilities, making them unable to effectively strip away thin-film residual oil within rock pores.

[0005] In addition, the system composed of nanoparticles, polymers and surfactants can enhance the stability of the system through the interfacial adsorption and steric hindrance of nanoparticles. However, the preparation of nanoparticles requires special grinding, the process is complicated, the total reagent cost is higher than that of traditional ternary systems, and nanoparticles are prone to agglomeration, requiring the addition of dispersants. Furthermore, the injection pressure of this system is higher than that of traditional systems.

[0006] Therefore, it is necessary to propose an oil displacement system to solve the problems existing in the current oil displacement system. Summary of the Invention

[0007] One objective of this invention is to provide a method for preparing an oil displacement composition based on mixed alkanolamines. The mixed alkanolamines, composed of ethylenediamine (EDA) and diethanolamine (DEA), are combined with a hydrophobic associative polymer (HAWP) to construct an oil displacement system. This system can be applied to oil reservoirs with high temperature and medium salinity, solving the problems of difficult compatibility, excessive precipitation, and high cost of traditional ternary flooding systems, weak IFT reduction and salt gradient resistance of single alkanolamine / polymer binary flooding, and high cost and difficult injection of nano-flooding.

[0008] This invention is achieved through the following technical solution:

[0009] A method for preparing an oil displacement composition based on mixed alkanolamines includes the following steps:

[0010] Ethylenediamine and diethanolamine are added to water to obtain an alcohol amine solution;

[0011] The oil displacement composition is formed by mixing the alkanolamine solution with a block-type hydrophobic associative polymer.

[0012] In this technical solution, ethylenediamine and diethanolamine are dissolved in water to obtain a homogeneous and transparent amine solution. In one or more embodiments, the water can be formation water or simulated formation water. In some preferred embodiments, ethylenediamine and diethanolamine are added to water at room temperature and stirred for 5-20 minutes to obtain the amine solution.

[0013] In this technical solution, after obtaining the alkanolamine solution, it is compounded with a block-type hydrophobic associating polymer and stirred evenly to obtain an oil displacement composition. In some preferred embodiments, the block-type hydrophobic associating polymer is slowly added to the alkanolamine solution and stirred for 120-200 minutes, controlling the rotation speed at 200-300 rpm to avoid the formation of fisheyes.

[0014] In this technical solution, the oil displacement system constructed by mixing alkanolamines and block-type hydrophobic associative polymers can utilize the synergistic effect of the bidentate chelation of ethylenediamine, its strong alkalinity, and the hydrogen bonding bridging and interfacial stability of diethanolamine to replace the surfactants or weak alkaline systems used in existing technologies. Specifically, the diamino groups of ethylenediamine... With formation water or It forms bidentate chelates, while the hydroxyl group (-OH) of diethanolamine forms bidentate / monodentate mixed chelates through assisted coordination, achieving bimodal complexation and salt resistance; simultaneously, the moderately strong basicity of ethylenediamine (pKb≈4.07) can neutralize the organic acids in crude oil to form bipolar petroleum acid soaps, and diethanolamine's... Adsorbed via hydrogen bonding at the oil-water interface, a soap-alkanolamine composite film is formed. This film effectively reduces IFT (internal free radical) and stabilizes IFT at a certain level. Therefore, efficient oil washing can be achieved without the need to add surfactants.

[0015] Furthermore, in this technical solution, the hydroxyl groups of diethanolamine can form hydrogen bonds with the hydrophilic carboxyl groups of the hydrophobic associating polymer, while the diamino groups of ethylenediamine can form hydrogen bonds with the hydrophilic segments of the hydrophobic associating polymer. Diethanolamine and ethylenediamine together promote the aggregation of hydrophobic blocks, improve the viscosity-enhancing efficiency of the oil displacement composition, and reduce the critical association concentration (CAC), thereby achieving high viscosity enhancement at low concentrations.

[0016] Furthermore, the ethylenediamine concentration in the oil displacement composition is 0.15%~0.6% by mass. In the system, if the concentration of ethylenediamine is too low, the chelating ability decreases, making it prone to scaling and clogging the formation, thus affecting the stability of the oil displacement system. Simultaneously, an excessively low ethylenediamine concentration cannot adequately neutralize the organic acids in the crude oil to form bipolar petroleum acid soaps, making it difficult to reduce IFT to the desired target range. Moreover, hydrogen bonding with the hydrophilic segments of hydrophobic polymers decreases, making it difficult to promote hydrophilic block aggregation and resulting in low thickening efficiency. Conversely, if the concentration of ethylenediamine is too high, the pH of the system increases accordingly, thereby damaging the stability of other components, such as the hydrophobic polymers. Excessive amines can also lead to excessive accumulation of the soap-amine composite film, making it difficult to reduce IFT to the target range. Therefore, in this technical solution, preferably, the mass-volume concentration of ethylenediamine in the oil displacement composition is set to 0.15%~0.6%.

[0017] Further, the diethanolamine in the oil displacement composition has a mass-volume concentration of 0.05% to 0.2%. In the system, if the concentration of diethanolamine is too low, the hydrogen bond adsorption of the oil-water cleanser is insufficient, the soap-ethanolamine composite film is incomplete, and the IFT cannot be stabilized within a low range. Similarly, the hydrogen bond interaction with the carboxyl groups of the hydrophobic polymer is weak, making it difficult to effectively promote the aggregation of hydrophilic blocks, resulting in weak thickening or reduction of CAC. Conversely, an excessively high concentration will cause excessive carboxyl groups to compete with the amino groups of ethylenediamine for coordination sites of metal ions, thereby weakening the chelation effect, making the composite film too thick or too hydrophilic, which will hinder the interaction between crude oil and the oil displacement system. Therefore, in this technical solution, it is preferable to set the mass-volume concentration of diethanolamine in the oil displacement composition to 0.05% to 0.2%.

[0018] Furthermore, the mass ratio of ethylenediamine to diethanolamine is 3:1 to 5:1. In the system, ethylenediamine primarily functions for bidentate chelation. or Ethylenediamine neutralizes organic acids to generate petroleum ether soaps for oil displacement and forms hydrogen bonds with the hydrophilic segments of the polymer to promote aggregation. Diethanolamine is mainly used to assist coordination to strengthen chelation, stabilize the composite film through interfacial hydrogen bonds, and assist polymer aggregation. Experiments have shown that the two achieve better results when a specific mass ratio is met. Therefore, in this technical solution, the mass ratio of ethylenediamine to diethanolamine is set to 3:1 to 5:1.

[0019] Furthermore, the concentration of the block-type hydrophobic associative polymer is 1500~2500 mg / L.

[0020] In some preferred embodiments, the block-type hydrophobic associative polymer is AP-P4, which is a copolymer of acrylamide, acrylic acid, and hexadecyl dimethyl allyl ammonium chloride.

[0021] Another objective of this invention is to provide an oil displacement composition prepared by any of the aforementioned methods. This composition forms a soap-alkanolamine composite film through EDA-DEA compounding, stabilizing the interfacial tension (IFT) within an ultra-low interfacial tension range without the need for surfactants, thus solving the problems of difficult surfactant compatibility in traditional ternary flooding and high cost in nano-flooding. Simultaneously, the mixed bidentate and monodentate chelation mechanism of the mixed alkanolamines reduces the adverse effects of salt ion electrostatic shielding on viscosity and avoids polymer precipitation problems under high salinity. Furthermore, the mixed alkanolamines promote hydrophobic association of HAWPs through hydrogen bonding bridging, effectively reducing CAC.

[0022] Another object of the present invention is to provide the application of any of the aforementioned oil displacement compositions. Specifically, the oil displacement composition is used at 75-100°C with a salinity of [missing information]. Oil displacement from reservoirs.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0024] 1. This invention can utilize the synergistic effect of ethylenediamine's bidentate chelation, strong alkalinity, and diethanolamine's hydrogen bonding bridging and interfacial stability to replace the surfactants or weak alkaline systems used in the prior art. At the same time, diethanolamine and ethylenediamine jointly promote the aggregation of hydrophobic blocks, which can effectively improve the viscosity-enhancing efficiency of the oil displacement composition and reduce the critical association concentration (CAC), thereby achieving high viscosity enhancement at low concentrations.

[0025] 2. By adjusting the ratio of ethylenediamine to diethanolamine in the oil displacement system, this invention can more effectively utilize the bidentate chelation of ethylene glycol. or The composition neutralizes organic acids to generate petroleum acid soaps for oil displacement and forms hydrogen bonds with the hydrophilic segments of the polymer to promote aggregation. At the same time, diethanolamine is used to assist coordination to strengthen chelation, and interfacial hydrogen bonds stabilize the composite film and assist polymer aggregation. The synergistic effect of ethylenediamine and diethanolamine further improves the performance of the oil displacement composition.

[0026] 3. The oil displacement composition of the present invention eliminates the need for surfactants or high-concentration weak alkalis, and does not require the addition of nanoparticles or dispersants, which can effectively reduce costs. At the same time, it does not generate precipitation due to high alkali concentration and avoids long-term retention of nanoparticles in the reservoir, making it more formation-friendly. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 This is a flowchart illustrating the preparation method of the oil displacement composition in a specific embodiment of the present invention;

[0029] Figure 2 The variations in viscosity of three oil displacement systems at different sodium chloride concentrations are shown in a specific embodiment of the present invention.

[0030] Figure 3 The viscosity of three oil displacement systems at 80°C over time is shown in a specific embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0032] All raw materials used in this invention are not particularly limited in their source; they can be purchased commercially or prepared using conventional methods well-known to those skilled in the art. The purity of all raw materials used in this invention is not particularly limited; however, this invention preferably adopts the purity requirements conventional in the field of oil displacement agents. All raw materials used in this invention have brand names and abbreviations that are conventional in the field, and each brand name and abbreviation is clearly defined within its relevant application area. Those skilled in the art can obtain them from commercially available sources or prepare them using conventional methods based on the brand name, abbreviation, and corresponding application.

[0033] The present invention does not impose any particular restrictions on the expression of the substituents, and all expressions are well known to those skilled in the art. Based on common sense, those skilled in the art can correctly understand their meaning according to their expression.

[0034] I. Preparation of Oil Displacement Composition

[0035]

Example 1

[0036] Take 1000 mL of simulated formation water, which includes NaCl, and The concentration of NaCl was 50 g / L. The concentration was 1.5 g / L. The concentration was 0.8 g / L. 3 g EDA and 1 g DEA were added to simulated formation water at 25°C, and the mixture was magnetically stirred for 20 minutes at a speed of 200 rpm until EDA and DEA were completely dissolved, thus obtaining an alcoholamine solution.

[0037] Add 1.5 g of AP-P4 dry powder to the amine solution, adjust the rotation speed to 250 rpm, and stir for 120 minutes to obtain the oil displacement composition 1. The viscosity of the oil displacement composition 1 is [missing value]. The mass ratio of EDA to DEA was 3:1, and the total concentration was 0.4%.

[0038]

Example 2

[0039] Take 1000 mL of simulated formation water, which includes NaCl, and The concentration of NaCl was 100 g / L, and the concentration of CaCl2 was 2 g / L. The concentration was 1 g / L. 5 g EDA and 1 g DEA were added to simulated formation water at 25°C, and the mixture was magnetically stirred for 20 minutes at a speed of 200 rpm until EDA and DEA were completely dissolved to obtain an alcohol amine solution.

[0040] Add 2.5 g of AP-P4 dry powder to the amine solution, adjust the rotation speed to 300 rpm, and stir for 200 minutes to obtain the oil displacement composition 2. The viscosity of the oil displacement composition 2 is [missing value]. The mass ratio of EDA to DEA was 5:1, and the total concentration was 0.6%.

[0041] II. Testing of Oil Displacement Compositions

[0042]

Example 3

[0043] In this embodiment, dehydrated crude oil from an oilfield (viscosity) is used. The core sample was taken at 70°C with an acid value of 0.8 mg KOH / g. It was a natural sandstone core (permeability 800 mD, porosity 28%, length 10 cm).

[0044] During the experiment, the core was vacuum saturated with simulated formation water from Example 1 to calculate the pore volume; then the crude oil was resaturated, and the initial oil saturation was measured to be 36%.

[0045] Subsequently, simulated formation water was injected at a rate of 0.5 mL / min until the water cut at the outlet reached 98%, at which point the recovery rate was 27%. Then, 0.4 PV of the oil displacement composition 1 was injected at the same rate, followed by 0.8 PV of simulated formation water for subsequent waterflooding. Ultimately, the recovery rate was 39%, an improvement of 12 percentage points compared to waterflooding. Oil displacement composition 1 is suitable for medium-high temperature, high-salinity reservoirs, at a temperature of 75°C.

[0046]

Example 4

[0047] In this embodiment, dehydrated crude oil from an oilfield (viscosity) is used. The core sample was taken at 100°C with an acid value of 1.5 mg KOH / g. The core was an artificial sandstone core (permeability 1000 mD, porosity 26%, length 10 cm).

[0048] During the experiment, the core was vacuum saturated with simulated formation water from Example 2 to calculate the pore volume; then the crude oil was resaturated, and the initial oil saturation was measured to be 38%.

[0049] Subsequently, simulated formation water was injected at a rate of 0.5 mL / min until the water cut at the outlet reached 98%, at which point the recovery rate was 25%. Then, 0.5 PV of the oil displacement composition 2 was injected at the same rate, followed by 1.0 PV of simulated formation water for subsequent waterflooding. Ultimately, the recovery rate was 36%, an improvement of 11 percentage points compared to waterflooding, and the IFT stabilized at 100°C for 90 days. Oil displacement composition 2 is suitable for high-temperature, high-salinity oil reservoirs, with a temperature of 100°C and high-acid-value crude oil.

[0050]

Example 5

[0051] In this embodiment, the viscosity of three systems—an oil displacement composition (EDA / DEA / AP-P4), a system of a single alkanolamine and a polymer (DEA / AP-P4), and a traditional ternary composite flooding system (petroleum sulfonate / sodium carbonate / HPAM)—was tested at different sodium chloride concentrations. The polymer concentration was 1750 mg / L, the temperature was 25°C, and the shear rate was... .

[0052] The test results are as follows Figure 2 As shown, when the NaCl concentration increases from 0 to 100 g / L, the system viscosity of the oil displacement composition of the present invention increases from... First increase and then decrease to The system of single alkanolamines and polymers from Down to Traditional ternary composite drive systems, on the other hand, are based on... Down to This demonstrates that mixed alkanolamines significantly enhance the salt resistance of oil displacement systems, making them suitable for high-salinity reservoirs.

[0053] Furthermore, Figure 3 The viscosity changes of the three oil displacement systems at 80°C over time are also shown in the figure. Unlike the single amine system and the ternary composite displacement system, the oil displacement composition of the present invention can still maintain high viscosity after 80 days. This indicates that the synergistic structure formed by the components of the system through chelation, hydrogen bonding, etc., does not undergo significant deassociation, degradation, or dispersion during long-term storage, and can continuously maintain a stable molecular aggregation state. The chelating effect of ethylenediamine and the interfacial stabilization / hydrogen bonding assistance of diethanolamine form a "long-term binding" with the association structure of the hydrophobic polymer, avoiding ionic damage to the polymer structure and resisting the risk of mild degradation that should occur.

[0054] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an oil displacement composition based on mixed alkanolamines, characterized in that, Includes the following steps: Ethylenediamine and diethanolamine are added to water to obtain an alcohol amine solution; The oil displacement composition is formed by mixing the alkanolamine solution with a block-type hydrophobic associative polymer.

2. The method for preparing an oil displacement composition based on mixed alkanolamines according to claim 1, characterized in that, The ethylenediamine in the oil displacement composition has a mass-volume concentration of 0.15% to 0.6%.

3. The method for preparing an oil displacement composition based on mixed alkanolamines according to claim 1, characterized in that, The diethanolamine in the oil displacement composition has a mass-volume concentration of 0.05% to 0.2%.

4. A method for preparing an oil displacement composition based on mixed alkanolamines according to any one of claims 1 to 3, characterized in that, The mass ratio of ethylenediamine to diethanolamine is 3:1 to 5:

1.

5. The method for preparing an oil displacement composition based on mixed alkanolamines according to claim 4, characterized in that, The concentration of the block-type hydrophobic associative polymer is 1500~2500 mg / L.

6. The method for preparing an oil displacement composition based on mixed alkanolamines according to claim 1, characterized in that, At room temperature, ethylenediamine and diethanolamine are added to water and stirred for 5 to 20 minutes to obtain the ethanolamine solution.

7. The method for preparing an oil displacement composition based on mixed alkanolamines according to claim 1, characterized in that, The block-type hydrophobic associative polymer is slowly added to the alkanolamine solution, and the mixture is stirred for 120-200 minutes at a speed of 200-300 rpm to obtain the oil displacement composition.

8. An oil displacement composition based on mixed alkanolamines, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The application of an oil displacement composition based on mixed alkanolamines, characterized in that, The oil displacement composition based on mixed alkanolamines as described in claim 8 is used, wherein the oil displacement composition is applied at 75-100°C and has a salinity of [missing information]. Oil displacement from reservoirs.

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