Method for catalyzing the stable conversion of asphaltene in carbon dioxide flooding of heavy oil by oil-soluble transition metal salt

Abstract

The application relates to a method for stabilizing the conversion of asphaltene in carbon dioxide flooding of heavy oil by using an oil-soluble transition metal salt. The method comprises dispersing the oil-soluble transition metal salt in a cosolvent to prepare a solution with a mass percentage of 5-30%; adding a heavy oil sample from an oil field, heating and stirring uniformly; continuing the reaction in the presence of nitrogen and carbon dioxide, cooling to room temperature after the reaction is completed, and obtaining a required oil sample. The method has good universality for heavy oils from different places and effectively solves the contradiction between viscosity reduction and asphaltene deposition in carbon dioxide flooding of heavy oil.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a method for stabilizing asphaltene conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts. Background Technology

[0002] Heavy oil accounts for over 70% of the world's remaining petroleum resources, and its high content of gum and asphaltenes results in extremely poor fluidity. Carbon dioxide flooding (CFD) technology, due to its dual benefits of enhanced oil recovery and carbon sequestration, has become a core technology for the green and low-carbon development of heavy oil. However, after carbon dioxide injection, the low-polarity carbon dioxide molecules dissolve in the heavy oil, reducing the overall polarity of the system, disrupting the dispersion balance of heavy components, and inducing asphaltenes flocculation and deposition. The deposited asphaltenes clog reservoir pores and throats, causing a decrease in permeability and severely limiting the effectiveness of CFD. Therefore, the contradiction between viscosity reduction and asphaltenes deposition in heavy oil CFD has become a key scientific problem restricting the application efficiency of this technology.

[0003] Existing technologies for inhibiting asphaltene deposition mainly rely on physical dispersants or surfactants to delay aggregation through electrostatic or steric hindrance. However, these physical inhibitors can only delay deposition and cannot change the strong polarity and π-π stacking tendency of asphaltene molecules, let alone fundamentally reverse the self-associative nature of asphaltene. Studies have shown that colloids have a stabilizing effect on asphaltene—colloids adsorb onto the asphaltene surface to form a viscous adsorption layer, encapsulating the asphaltene in a spherical shape. When the mass ratio of colloids to asphaltene is greater than 2:1, the resulting colloid-asphaltene structure tends to be stable, effectively inhibiting the associative deposition between asphaltene molecules. Therefore, if some asphaltene can be directionally converted into colloids through chemical means, shifting the colloid / asphaltene ratio of the system towards a stable range, asphaltene stabilization can be achieved from the source.

[0004] In recent years, oil-soluble transition metal salts have attracted attention in the field of heavy oil upgrading due to their excellent oil solubility and catalytic activity. Studies have shown that aryl fatty acid transition metal salts (such as iron oleate) can form a hydrogen-donating catalytic cracking system in heavy oil, promoting the hydrogenation and ring-opening cracking of polycyclic aromatic hydrocarbons, and significantly increasing the content of saturated hydrocarbons and aromatic hydrocarbons. However, existing research mainly focuses on the catalytic viscosity-reducing effect and has not yet addressed the technical solution of using oil-soluble transition metal salts to achieve the "directional conversion of asphaltenes to resins" under carbon dioxide flooding conditions. This invention addresses the above-mentioned technological gap by providing a method for stabilizing the conversion of asphaltenes in heavy oil carbon dioxide flooding catalyzed by oil-soluble transition metal salts. Summary of the Invention

[0005] To address the technical shortcomings of existing carbon dioxide flooding processes, such as the tendency of asphaltenes to flocculate and deposit, and the fact that traditional physical inhibitors can only delay deposition but cannot reverse the self-association nature of asphaltenes, this invention provides a method for stabilizing the conversion of asphaltenes in heavy oil carbon dioxide flooding using oil-soluble transition metal salt catalysts. By using oil-soluble transition metal salt catalysts under carbon dioxide flooding conditions, asphaltenes are directionally converted into resins, increasing the resin / asphalt mass ratio of the system to a stable range, thereby inhibiting asphaltenes deposition from the source.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0008] The first step involves dispersing the oil-soluble transition metal salt in a co-solvent and stirring until uniformly dissolved to prepare a solution with a mass percentage of 5-30%. The oil-soluble transition metal salt is one or more of the following: ferric oleate, nickel oleate, cobalt oleate, manganese oleate, copper oleate, zinc oleate, ferric dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, cobalt dodecylbenzenesulfonate, manganese dodecylbenzenesulfonate, copper dodecylbenzenesulfonate, zinc dodecylbenzenesulfonate, ferric dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, cobalt dodecylbenzenesulfonate, manganese dodecylbenzenesulfonate, copper dodecylbenzenesulfonate, and zinc dodecylbenzenesulfonate, with industrial-grade or higher purity. The co-solvent is one or more of the following: toluene, xylene, petroleum ether, n-hexane, anhydrous ethanol, and anhydrous propanol, with industrial-grade or higher purity.

[0009] The second step involves adding heavy oil samples from the oilfield to a high-pressure reactor equipped with a stirring device and two valves, and adding the solution prepared in the first step at a mass percentage of 0.1-5% of the heavy oil. The mixture is then heated to 20-40°C above the pour point of the oil sample and stirred until homogeneous.

[0010] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 5-20 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 2-12 MPa, and close all valves; heat to 100-200℃ with stirring, and react for 4-24 hours; the nitrogen and carbon dioxide mentioned are industrial grade or higher purity products.

[0011] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0012] Unlike existing technologies, this invention has the following advantages: the oil-soluble transition metal salt catalyst combines Lewis acid catalytic activity, oil-soluble dispersion function, and hydrogen-donating cracking capability. Its metal ions, acting as Lewis acid centers, can coordinate and activate polar functional groups (such as hydroxyl, amino, and carboxyl groups) in heavy oil components; the long-chain alkyl groups endow it with good oil solubility, allowing it to be uniformly dispersed in heavy oil and at the oil-CO2 interface, directly acting on the active sites of asphaltenes aggregates. The catalyst promotes the hydrogenation and ring-opening cracking of polycyclic aromatic hydrocarbons through a hydrogen-donating catalytic cracking mechanism, disrupting the π-π stacking and hydrogen bond association structure of asphaltenes; simultaneously, it catalyzes the carboxylation reaction of highly polar functional groups in asphaltenes with carbon dioxide, reducing the polarity of asphaltenes molecules, weakening their self-association tendency, and achieving the directional conversion of asphaltenes into resins, thereby fundamentally solving the contradiction between viscosity reduction and asphaltenes deposition during heavy oil carbon dioxide flooding.

[0013] The beneficial effects of this invention are as follows:

[0014] (1) This invention uses oil-soluble transition metal salts to catalyze the chemical reaction between carbon dioxide and asphaltenes, thereby converting asphaltenes into resins in a directional manner. This increases the resin / asphalt mass ratio of the system from about 2:1 or less in conventional heavy oil to a stable range (≥2:1), thus inhibiting asphaltenes flocculation and deposition from the source.

[0015] (2) The oil-soluble transition metal salt catalyst selected in this invention has Lewis acid catalytic activity, oil-soluble dispersion function and hydrogen-donating cracking ability. It can destroy the structure of asphaltene aggregates through the coordination activation of metal ions, and at the same time catalyze the reaction of polar functional groups with carbon dioxide. The dual effects work together to achieve the precise conversion of asphaltene into resin.

[0016] (3) Based on the real environment of heavy oil reservoirs, this invention utilizes the high temperature and high pressure microreactor environment of the reservoir formed by carbon dioxide displacement, without the need for additional energy input, with low catalyst dosage (only 0.05-1% of the heavy oil mass), viscosity reduction rate can reach 70%-90%, and asphaltene content reduced by more than 35%.

[0017] (4) The method of the present invention has good universality for heavy oil from different origins, and effectively solves the contradiction between viscosity reduction and asphalt deposition in heavy oil carbon dioxide flooding. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments.

[0019] Example 1

[0020] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0021] First, weigh 2.0 g of analytical grade nickel oleate into a 25 mL beaker, add 8.0 g of chemically pure toluene as a co-solvent, stir until uniformly dissolved, and prepare a solution with a mass percentage of 20%.

[0022] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 0.6 g of the solution prepared in the first step according to the heavy oil mass percentage of 0.5% and adding it to the reactor; heating the system to 28°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0023] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 18 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 6 MPa, and close all valves; heat to 120°C with stirring, and react for 6 hours; the nitrogen and carbon dioxide are industrial grade products.

[0024] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0025] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1310 Pa·s to 289 Pa·s, with a viscosity reduction rate of 77.9%; the asphalt content is reduced from 17.8% to 5.4%, with a content reduction of 69.6%; the gum content is increased from 36.6% to 46.8%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

[0026] Example 2

[0027] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0028] First, weigh 1.6 g of industrial grade ferric oleate into a 25 mL beaker, add 8.4 g of analytical grade n-hexane as a co-solvent, stir until uniformly dissolved, and prepare a solution with a mass percentage of 16%.

[0029] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 2.42 g of the solution prepared in the first step according to the heavy oil mass percentage of 2% and adding it to the reactor; heating the system to 25°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0030] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 12 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 4 MPa, and close all valves; heat to 110℃ with stirring, and react for 4 hours; the nitrogen and carbon dioxide are industrial grade products.

[0031] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0032] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1310 Pa·s to 313 Pa·s, with a viscosity reduction rate of 76.1%; the asphalt content is reduced from 17.8% to 4.1%, with a content reduction of 76.9%; the gum content is increased from 36.6% to 47.9%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

[0033] Example 3

[0034] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0035] First, weigh 0.6 g of analytical grade cobalt oleate into a 25 mL beaker, add 9.4 g of industrial grade petroleum ether as a co-solvent, stir until uniformly dissolved, and prepare a solution with a mass percentage of 6%.

[0036] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 4.84 g of the solution prepared in the first step according to the heavy oil mass percentage of 4% and adding it to the reactor; heating the system to 35°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0037] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 10 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 10 MPa, and close all valves; heat to 160℃ with stirring, and react for 10 hours; the nitrogen and carbon dioxide are industrial grade products.

[0038] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0039] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1310 Pa·s to 288 Pa·s, with a viscosity reduction rate of 78.0%; the asphalt content is reduced from 17.8% to 4.3%, with a content reduction of 76.0%; the gum content is increased from 36.6% to 45.8%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

[0040] Example 4

[0041] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0042] First, weigh 1.0 g of analytical grade ferric dodecylbenzenesulfonate into a 25 mL beaker, add 9.0 g of analytical grade anhydrous ethanol as a co-solvent, stir until uniformly dissolved, and prepare a 10% (w / w) solution.

[0043] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 1.21 g of the solution prepared in the first step according to the 1% mass percentage of heavy oil and adding it to the reactor; heating the system to 23°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0044] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 10 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 4 MPa, and close all valves; heat to 110℃ with stirring, and react for 8 hours; the nitrogen and carbon dioxide are industrial grade products.

[0045] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0046] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1442 Pa·s to 790 Pa·s, with a viscosity reduction rate of 45.2%; the asphalt content is reduced from 26.7% to 20.0%, a reduction of 25.1%; the gum content is increased from 36.5% to 41.4%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

[0047] Example 5

[0048] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0049] First, weigh 1.5 g of industrial grade ferric dodecyl sulfonate into a 25 mL beaker, add 8.5 g of industrial grade anhydrous ethanol as a co-solvent, stir until uniformly dissolved, and prepare a solution with a mass percentage of 15%.

[0050] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 3.02 g of the solution prepared in the first step according to the heavy oil mass percentage of 2.5% and adding it to the reactor; heating the system to 30°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0051] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 15 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 8 MPa, and close all valves; heat to 150℃ with stirring, and react for 4 hours; the nitrogen and carbon dioxide mentioned are industrial grade products.

[0052] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0053] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1360 Pa·s to 887 Pa·s, with a viscosity reduction rate of 34.8%; the asphalt content is reduced from 26.5% to 21.0%, with a content reduction of 20.8%; the gum content is increased from 38.5% to 42.9%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

[0054] Example 6

[0055] A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts, comprising the following steps:

[0056] First, weigh 2.5 g of industrial grade cobalt dodecyl sulfonate into a 25 mL beaker, add 7.5 g of industrial grade anhydrous propanol as a co-solvent, stir until uniformly dissolved, and prepare a solution with a mass percentage of 25%.

[0057] The second step involves adding 130 mL (120.9 g) of heavy oil sample from the oilfield to a 200 mL high-pressure reactor equipped with a stirrer and a double valve; weighing 3.63 g of the solution prepared in the first step according to the heavy oil mass percentage of 3% and adding it to the reactor; heating the system to 32°C above the pour point of the heavy oil and turning on the stirrer to mix thoroughly.

[0058] Third step: Connect one valve to nitrogen gas, open the other valve to purge air from the reactor for 10 minutes, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the pressure to 7 MPa, and close all valves; heat to 130℃ with stirring, and react for 12 hours; the nitrogen and carbon dioxide are industrial grade products.

[0059] Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

[0060] The beneficial effects of this invention are as follows: after the above treatment, the viscosity of the heavy oil is reduced from 1360 Pa·s to 699 Pa·s, with a viscosity reduction rate of 48.6%; the asphalt content is reduced from 26.5% to 21.4%, with a content reduction of 19.3%; the gum content is increased from 38.5% to 43.0%; at the same time, the viscosity of the heavy oil and the asphalt content are reduced (conversion of asphalt to gum) are achieved.

Claims

1. A method for stabilizing asphaltenes conversion during carbon dioxide flooding of heavy oil using oil-soluble transition metal salts as catalysts, characterized in that... Includes the following steps: The first step is to disperse the oil-soluble transition metal salt in a co-solvent and stir until it is uniformly dissolved, thus preparing a solution with a mass percentage of 5-30%.

2. The method according to claim 1, characterized in that... Includes the following steps: The second step involves adding heavy oil samples from the oilfield to a high-pressure reactor equipped with a stirring device and two valves. The solution prepared in the first step is added at a mass percentage of 0.1-5% of the heavy oil. The mixture is then heated to 20-40°C above the pour point of the oil sample and stirred until homogeneous.

3. The method according to claim 2, characterized in that... Includes the following steps: Third, connect one valve to nitrogen and open the other valve to purge air from the reactor for 5-20 minutes, then close the outlet valve; replace the inlet valve with carbon dioxide, purge the pressure to 2-12 MPa, and close all valves; heat to 100-200℃ with stirring, and react for 4-24 hours.

4. The method according to claim 3, characterized in that... Includes the following steps: Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

5. The method according to claim 1, characterized in that... Includes the following steps: The first step is to disperse the oil-soluble transition metal salt in a co-solvent and stir until it is uniformly dissolved, so as to prepare a solution with a mass percentage of 5-30%. The second step involves adding heavy oil samples from the oilfield to a high-pressure reactor equipped with a stirring device and two valves, and adding the solution prepared in the first step at a mass percentage of 0.1-5% of the heavy oil. The mixture is then heated to 20-40°C above the pour point of the oil sample and stirred until homogeneous. Third step: Connect one valve to nitrogen gas, open the other valve to purge air for 5-20 minutes to remove air from the reactor, and close the outlet valve; replace the inlet valve with carbon dioxide, purge the gas pressure to 2-12 MPa, and close all valves; heat to 100-200℃ with stirring, and react for 4-24 hours. Fourth step: After the reaction is complete, cool to room temperature, open the reaction vessel, take out the oil sample, determine the viscosity of the heavy oil using the method specified in SY-T 7549-2000, and determine the content of gums and asphaltenes using the method specified in NB / SH / T 0509-2010.

6. The method according to claim 1, characterized in that... Includes the following steps: The oil-soluble transition metal salt is one or more of the following with industrial grade or higher purity: iron oleate, nickel oleate, cobalt oleate, manganese oleate, copper oleate, zinc oleate, iron dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, cobalt dodecylbenzenesulfonate, manganese dodecylbenzenesulfonate, copper dodecylbenzenesulfonate, zinc dodecylbenzenesulfonate, iron dodecylbenzenesulfonate, nickel dodecylbenzenesulfonate, cobalt dodecylbenzenesulfonate, manganese dodecylbenzenesulfonate, copper dodecylbenzenesulfonate, and zinc dodecylbenzenesulfonate; the co-solvent is one or more of the following with industrial grade or higher purity: toluene, xylene, petroleum ether, n-hexane, anhydrous ethanol, and anhydrous propanol.

7. The method according to claim 3, characterized in that... The process includes the following steps: the nitrogen and carbon dioxide are products of industrial grade or higher purity.

8. Use of the method according to any one of claims 1-7 in the petrochemical field.