A CO2 solubilizing and viscosity reducing agent and its preparation method and application

Abstract

The present invention relates to the technical field of viscosity reduction for heavy oil production, and discloses a CO2 solubilizing and viscosity reducing agent, its preparation method, and application. The CO2 solubilizing and viscosity reducing agent comprises component A and supercritical CO2; component A comprises ethylene glycol dimethyl ether, sodium lauryl sulfate, and an emulsion stabilizer; the emulsion stabilizer is sodium polyphosphate and / or polyacrylamide. The CO2 solubilizing and viscosity reducing agent provided by the present invention has excellent CO2 solubilization and heavy oil viscosity reduction effects, a simple preparation process, and high economic value.

Description

Technical Field

[0001] The present invention relates to the technical field of viscosity reduction mining of heavy oil, and in particular to a CO2 solubilizing and viscosity reducing agent, a preparation method thereof and an application thereof. Background Art

[0002] Conventional methods cannot efficiently recover heavy oil due to its high viscosity and poor fluidity, making gas injection difficult. Currently, heavy oil recovery primarily relies on cold recovery, thermal recovery, and combined cold and hot recovery techniques. CO2 injection has emerged as an effective development method in recent years.

[0003] The main problems faced in using thermal recovery technology to develop heavy oil are as follows: the injection pressure of the reservoir is basically higher than the critical pressure of steam. When reaching the target layer, the high-temperature steam is converted into high-temperature hot water. The heat and thermal enthalpy it carries are much lower than steam. The effective oil leakage diameter is less than 35m, and the effect of heavy oil thermal recovery by steam is greatly reduced.

[0004] CO2 development technology can effectively increase oil and gas recovery by dissolving and reducing viscosity, enhancing fluidity through miscibility, and widening the sweep range. However, heavy oil recovery through CO2 injection faces challenges. Heavy oil has high viscosity due to its high asphaltene and wax content, which limits CO2's solubility in heavy oil. This results in limited effectiveness in enhancing heavy oil recovery using CO2.

[0005] Using a solubilizing viscosity reducer as an auxiliary agent for CO2 can, on the one hand, increase the solubility of CO2 in crude oil, increasing the amount of CO2 dissolved, and thus expanding the viscosity reduction range. On the other hand, the oil-soluble viscosity reducer dissolves in the CO2 and reaches the target reservoir together, fully contacting the crude oil, achieving a dual viscosity reduction effect of CO2 and the oil-soluble viscosity reducer. Furthermore, the dosage of the oil-soluble viscosity reducer is smaller than that of conventional water-soluble viscosity reducers because it is directly miscible with the crude oil and loses less water.

[0006] For example, CN112079954A discloses a CO2-solubilized crude oil viscosity reducer, its preparation method, and its application. The CO2-solubilized crude oil viscosity reducer is prepared by copolymerizing three monomers: 1-acryloyloxy-2-pyrrolidone, ethyl allyl ether, and methyl 4-vinylbenzoate. This prior art can reduce the minimum miscibility pressure of crude oil and CO2, enhance crude oil fluidity, and improve crude oil recovery; however, the finished product production process is complex, requiring monomer polymerization and strict experimental conditions. Summary of the Invention

[0007] The purpose of the present invention is to provide a CO2 solubilizing and viscosity reducing agent which has good CO2 solubilizing and heavy oil viscosity reducing effects and a simple preparation process.

[0008] In order to achieve the above-mentioned object, the first aspect of the present invention provides a CO2 solubilizing and viscosity reducing agent, which comprises component A and supercritical CO2; the component A comprises: ethylene glycol dimethyl ether, sodium lauryl sulfonate, and an emulsion stabilizer; the emulsion stabilizer is sodium polyphosphate and / or polyacrylamide;

[0009] In the component A, the mass ratio of the ethylene glycol dimethyl ether, the sodium lauryl sulfate, and the emulsion stabilizer is: 3-4:1-2:1;

[0010] The mass ratio of the component A to the supercritical CO2 is 1:1.86-3.

[0011] The second aspect of the present invention provides a method for preparing the CO2 solubilizing and viscosity reducing agent described in the first aspect, the method comprising:

[0012] The components in component A are stirred and mixed with supercritical CO2 to obtain the CO2 solubilizing and viscosity reducing agent; the component A contains ethylene glycol dimethyl ether, sodium lauryl sulfate, and an emulsion stabilizer;

[0013] The stirring and mixing conditions include: temperature of 50-70° C., pressure of 13-18 MPa, and stirring speed of 120-240 rpm.

[0014] The third aspect of the present invention provides the use of the CO2 solubilizing and viscosity reducing agent described in the first aspect in heavy oil production.

[0015] The fourth aspect of the present invention provides a method for heavy oil production, which comprises: contacting and reacting a CO2 solubilizing and viscosity reducing agent with raw heavy oil; the mass ratio of the CO2 solubilizing and viscosity reducing agent to the raw heavy oil is 3-5:100; the CO2 solubilizing and viscosity reducing agent is the CO2 solubilizing and viscosity reducing agent described in the first aspect above.

[0016] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0017] (1) The CO2 solubilizing and viscosity reducing agent provided by the present invention can be directly injected into the deep formation, miscible with the heavy oil, and at the same time increase the solubility of CO2 in the heavy oil, better play the effect of CO2 dissolving and viscosity reduction and extraction, and achieve the dual viscosity reduction effect of CO2 and viscosity reducing agent, thereby further improving the recovery rate of heavy oil;

[0018] (2) The CO2 solubilizing and viscosity reducing agent provided by the present invention uses an oil-soluble viscosity reducing agent, and does not require water as a carrier fluid. The system can carry the remaining chemicals into the formation through supercritical CO2, and the sweep diffusion effect is better than that of water carrying.

[0019] (3) The CO2 solubilizing and viscosity reducing agent provided by the present invention will not induce formation water sensitivity, and the amount of oil-soluble viscosity reducing agent used is small, which can reduce the difficulty and cost of separation when crude oil is produced.

[0020] (4) The technical solution provided by the present invention has a simple process and can be used to screen high-wax crude oil in a targeted manner, with good test results. DETAILED DESCRIPTION

[0021] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0022] It should be noted that, in various aspects of the present invention, for the same components or terms in various aspects, the present invention is only described once in one aspect without repeated description, which should not be understood by those skilled in the art as a limitation of the present invention.

[0023] As mentioned above, the first aspect of the present invention provides a CO2 solubilizing and viscosity reducing agent, which contains component A and supercritical CO2; the component A contains: ethylene glycol dimethyl ether, sodium lauryl sulfonate, and an emulsion stabilizer; the emulsion stabilizer is sodium polyphosphate and / or polyacrylamide;

[0024] In the component A, the mass ratio of the ethylene glycol dimethyl ether, the sodium lauryl sulfonate, and the emulsion stabilizer is: 3-4: 1-2; 1;

[0025] The mass ratio of the component A to the supercritical CO2 is 1:1.86-3.

[0026] Preferably, the sodium polyphosphate is sodium hexametaphosphate and / or sodium tripolyphosphate.

[0027] Preferably, the polyacrylamide is cationic polyacrylamide.

[0028] Preferably, the mass ratio of the ethylene glycol dimethyl ether to the sodium lauryl sulfate is 3-4: 1. The inventors of the present invention have found in their research that the CO2 solubilizing and viscosity reducing agent prepared under the preferred conditions has a better viscosity reducing effect on heavy oil, and the solubility of CO2 in heavy oil is significantly improved.

[0029] Preferably, the emulsion stabilizer is a combination of sodium polyphosphate and polyacrylamide in a mass ratio of 0.1-0.15:1. The inventors of the present invention have found in their research that the CO2 solubilizing and viscosity reducing agent prepared under these preferred conditions has a better viscosity reducing effect on heavy oil, and the solubility of CO2 in heavy oil is significantly improved.

[0030] Preferably, the purity of CO2 in the CO2-containing gas stream used to prepare the supercritical CO2 is greater than 80%. The CO2 purity described in the present invention refers to the mass percentage.

[0031] The present invention does not particularly limit the types and contents of gas components other than CO2 in the CO2-containing gas stream. These can be adjusted by those skilled in the art based on CO2 supercritical conditions. For example, gas components other than CO2 described herein include nitrogen, methane, and hydrogen, which are not further detailed herein and should not be construed as limiting the present invention by those skilled in the art.

[0032] As mentioned above, the second aspect of the present invention provides a method for preparing the CO2 solubilizing and viscosity reducing agent described in the first aspect, the method comprising:

[0033] The components in component A are stirred and mixed with supercritical CO2 to obtain the CO2 solubilizing and viscosity reducing agent; the component A contains ethylene glycol dimethyl ether, sodium lauryl sulfate, and an emulsion stabilizer;

[0034] The stirring and mixing conditions include: temperature of 50-70° C., pressure of 13-18 MPa, and stirring speed of 120-240 rpm.

[0035] According to a preferred embodiment, the method for preparing a CO2 solubilizing and viscosity reducing agent according to the present invention further comprises:

[0036] S1: Before performing the stirring and mixing operation, ethylene glycol dimethyl ether and sodium lauryl sulfate in the component A are introduced into a reaction kettle for first mixing to obtain a mixture I;

[0037] S2: performing a second mixing of the mixture I and the emulsion stabilizer in the component A to obtain a mixture II;

[0038] S3: introducing a CO2-containing gas flow into the reactor containing the mixture II, continuously pressurizing until supercritical CO2 is formed, and then stirring and mixing to obtain the CO2 solubilizing and viscosity reducing agent.

[0039] The present invention has no particular limitation on the conditions of the first mixing and the second mixing, as long as the materials can be mixed uniformly. The present invention will not elaborate on these conditions, and those skilled in the art should not interpret them as limitations on the present invention.

[0040] The present invention has no particular limitation on the device for performing the stirring and mixing, and those skilled in the art can select one based on equipment known in the art. Exemplarily, the device for stirring and mixing is an electromagnetic stirrer.

[0041] The present invention has no particular limitation on the storage device of the CO2 solubilizing and viscosity reducing agent, as long as the CO2 therein can be maintained in a supercritical state. For example, a gas cylinder is used for storage. The present invention will not be further described herein, and those skilled in the art should not be construed as limiting the present invention.

[0042] As mentioned above, the third aspect of the present invention provides the use of the CO2 solubilizing and viscosity reducing agent described in the first aspect in heavy oil production.

[0043] Preferably, the wax content of the thick oil is 15-40 wt%, preferably 30-40 wt%, and the viscosity is 800-2800 mPa·s, preferably 1000-2000 mPa·s.

[0044] As mentioned above, the fourth aspect of the present invention provides a method for heavy oil production, which includes: contacting and reacting a CO2 solubilizing and viscosity reducing agent with raw heavy oil; the mass ratio of the CO2 solubilizing and viscosity reducing agent to the raw heavy oil is 3-5:100; the CO2 solubilizing and viscosity reducing agent is the CO2 solubilizing and viscosity reducing agent described in the first aspect above.

[0045] Preferably, the contact reaction conditions include: temperature of 50-70° C. and time of 5-10 h.

[0046] Preferably, the raw material heavy oil has a wax content of 15-40 wt%, preferably 30-40 wt%, and a viscosity of 800-2800 mPa·s, preferably 1000-2000 mPa·s.

[0047] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0048] In the following examples, unless otherwise specified, the room temperature refers to 25±2°C.

[0049] In the following examples, the raw material heavy oil used was Tuha Tiaohu Formation heavy oil, with the four main components being 26.3 wt% asphaltenes, 33.6 wt% colloids, 30.2 wt% saturates, and 9.9 wt% aromatics. The raw material heavy oil had a viscosity of 1657 mPa·s and a wax content of 32 wt%.

[0050] In the following examples, the pretreatment method for the heavy oil used was as follows: 80 g of the raw heavy oil was placed in a 100 mL beaker and stirred in an oil bath at 100°C for 1 hour to thoroughly mix. The mixture was then removed and allowed to cool naturally at room temperature to obtain a heavy oil sample.

[0051] In the following examples, the amount of CO2 solubilizing and viscosity reducing agent obtained in each preparation example is 100 mL.

[0052] Polyacrylamide: purchased from Shanghai Titan Technology Co., Ltd., CAS number 9003-05-8;

[0053] Sodium polyphosphate I: sodium hexametaphosphate, purchased from Shanghai Boer Chemical Reagent Co., Ltd.; CAS number: 10124-56-8;

[0054] Sodium polyphosphate II: sodium tripolyphosphate, purchased from Shanghai Boer Chemical Reagent Co., Ltd.; CAS number 7758-29-4;

[0055] Reactor: The manufacturer is Jiangsu Tuochuang Company, and the model is a 500mL thickened container.

[0056] Preparation Example 1

[0057] S1: Ethylene glycol dimethyl ether and sodium lauryl sulfate in component A are introduced into a reaction kettle and stirred at room temperature for more than 1 hour to fully mix them to obtain a mixture I;

[0058] S2: Add the emulsion stabilizer in component A to the reactor and stir at room temperature for 4 hours to mix thoroughly to obtain mixture II;

[0059] The emulsion stabilizer is a combination of sodium polyphosphate I and polyacrylamide in a mass ratio of 0.1:1; the mass ratio of ethylene glycol dimethyl ether, sodium lauryl sulfate, and emulsion stabilizer is 3:1:1;

[0060] S3: introducing a CO2-containing gas stream into the reactor containing the mixture II, continuously pressurizing it until supercritical CO2 is formed, and then stirring and mixing to obtain a CO2-solubilizing viscosity-reducing agent, named J1;

[0061] The mass ratio of component A to supercritical CO2 is 1:1.86; the purity of CO2 in the CO2-containing gas flow is 90%; the stirring temperature is 50°C, the pressure is 13 MPa, and the stirring speed is 120 rpm.

[0062] Preparation Example 2

[0063] S1: Ethylene glycol dimethyl ether and sodium lauryl sulfate in component A are introduced into a reaction kettle and stirred at room temperature for more than 1 hour to fully mix them to obtain a mixture I;

[0064] S2: Add the emulsion stabilizer in component A to the reactor and stir at room temperature for 4 hours to mix thoroughly to obtain mixture II;

[0065] The emulsion stabilizer is a combination of sodium polyphosphate I and polyacrylamide in a mass ratio of 0.1:1; the mass ratio of ethylene glycol dimethyl ether, sodium lauryl sulfate, and emulsion stabilizer is 4:1:1;

[0066] S3: introducing a CO2-containing gas stream into the reactor containing the mixture II, continuously pressurizing it until supercritical CO2 is formed, and then stirring and mixing to obtain a CO2-solubilizing viscosity-reducing agent, named J2;

[0067] The mass ratio of component A to supercritical CO2 is 1:3; the mass purity of CO2 in the CO2-containing gas flow is 90%; the stirring temperature is 70°C, the pressure is 18 MPa, and the stirring speed is 240 rpm.

[0068] Preparation Example 3

[0069] S1: Ethylene glycol dimethyl ether and sodium lauryl sulfate in component A are introduced into a reaction kettle and stirred at room temperature for more than 1 hour to fully mix them to obtain a mixture I;

[0070] S2: Add the emulsion stabilizer in component A to the reactor and stir at room temperature for 4 hours to mix thoroughly to obtain mixture II;

[0071] The emulsion stabilizer is a combination of sodium polyphosphate I and polyacrylamide in a mass ratio of 0.15:1; the mass ratio of ethylene glycol dimethyl ether, sodium lauryl sulfate, and emulsion stabilizer is 3.5:1:1;

[0072] S3: introducing a CO2-containing gas stream into the reactor containing the mixture II, continuously pressurizing until supercritical CO2 is formed, and then stirring and mixing to obtain a CO2-solubilizing viscosity-reducing agent, named J3;

[0073] The mass ratio of component A to supercritical CO2 is 1:2.43; the purity of CO2 in the CO2-containing gas flow is 90%; the stirring and mixing temperature is 60°C, the pressure is 15.5 MPa, and the stirring speed is 180 rpm.

[0074] Preparation Example 4

[0075] The process was similar to that of Preparation Example 1, except that in step S2, only sodium polyphosphate I was used as the emulsion stabilizer, and the amount of the emulsion stabilizer remained unchanged.

[0076] A CO2 solubilizing and viscosity reducing agent was prepared and named J4.

[0077] Preparation Example 5

[0078] The process was similar to that of Preparation Example 1, except that in step S2, sodium polyphosphate I was replaced by sodium polyphosphate II of equal mass.

[0079] A CO2 solubilizing and viscosity reducing agent was prepared and named J5.

[0080] Comparative Preparation Example 1

[0081] A similar process to Preparation Example 1 was adopted, except that in step S1, the total amount of component A remained unchanged, and the mass ratio of ethylene glycol dimethyl ether, sodium lauryl sulfate, and emulsion stabilizer in component A was adjusted from 3:1:1 to 1:1:1.

[0082] A CO2 solubilizing and viscosity reducing agent was prepared and named DJ1.

[0083] Comparative Preparation Example 2

[0084] The process was similar to that of Preparation Example 1, except that in step S1, ethylene glycol dimethyl ether was replaced with ethanol of equal mass.

[0085] A CO2 solubilizing and viscosity reducing agent was prepared and named DJ2.

[0086] Comparative Preparation Example 3

[0087] The process was similar to that of Preparation Example 1, except that in step S1, sodium dodecyl sulfate was replaced with an equal mass of sodium stearate.

[0088] A CO2 solubilizing and viscosity reducing agent was prepared and named DJ3.

[0089] Example 1

[0090] The CO2 solubilizing and viscosity reducing agent was added to the heavy oil sample obtained by the aforementioned pretreatment method, and the reaction was carried out at 50°C for 5 hours to obtain the heavy oil after viscosity reduction;

[0091] The CO2 solubilizing and viscosity reducing agent is J1, and the mass ratio of the CO2 solubilizing and viscosity reducing agent to the heavy oil is 3:100.

[0092] Examples 2-4

[0093] A similar process to Example 1 was used, except that the CO2 solubilizing and viscosity reducing agent J1 in Example 1 was replaced with a CO2 solubilizing and viscosity reducing agent of equal mass shown in Table 1, and the rest was the same as Example 1;

[0094] A thick oil with reduced viscosity is prepared.

[0095] Comparative Examples 1-3

[0096] A similar process to Example 1 was used, except that the CO2 solubilizing and viscosity reducing agent J1 in Example 1 was replaced with a CO2 solubilizing and viscosity reducing agent of equal mass shown in Table 1, and the rest was the same as Example 1;

[0097] A thick oil with reduced viscosity is prepared.

[0098] Table 1

[0099]

[0100] Test Example 1: Solubility of CO2 in Heavy Oil

[0101] Test method: The viscosity-reduced heavy oil samples prepared in each embodiment and comparative example were pressurized to a preset pressure, stirred thoroughly, and the pressure value and the initial pump reading were recorded after the pressure stabilized; the metering pump pressure was maintained, and a certain volume of separator oil sample was discharged, and the final pump reading was recorded. The initial and final pump readings were kept the same for each test. The gas volume V was measured using a gas meter. c , called the discharged oil mass m y .

[0102] Calculation formula: Solubility C c (mol%) = n c / (n y +n c )×100%; where n c =V c / V m , n y =m y / M y ;

[0103] Among them, n c is the number of moles of CO2, mol; n y is the number of moles of discharged oil, mol; V c is the volume of CO2, L; V m is the molar volume, L / mol; m y is the mass of discharged oil, g; M y is the molar mass of the expelled oil, g / mol.

[0104] The results are shown in Table 2.

[0105] Test Example 2: Viscosity reduction rate of heavy oil using CO2 solubilizing and viscosity reducing agent

[0106] The viscosity reduction rate of heavy oil by CO2 solubilizing and reducing viscosity is determined using a falling ball viscometer. The falling ball viscometer is connected to the reactor pipeline, and the post-reaction fluid is introduced into the viscometer for pressure measurement of viscosity.

[0107] The viscosity-reduced heavy oil obtained in the aforementioned examples and comparative examples was placed in a PVT reactor and a high-temperature, high-pressure viscometer was used to measure the viscosity at 70°C for 3 minutes. The data was recorded after each measurement. The effect of the CO2-solubilizing viscosity reducer on the viscosity reduction rate was investigated.

[0108] Calculation formula: Viscosity reduction rate (%) = (initial viscosity - final viscosity) / initial viscosity × 100%

[0109] The results are shown in Table 2.

[0110] Table 2

[0111]

[0112] It can be seen from the above results that the preparation process of the CO2 solubilizing and viscosity reducing agent provided by the present invention is simple, and the prepared CO2 solubilizing and viscosity reducing agent can significantly increase the solubility of CO2 in heavy oil, and the viscosity of heavy oil is also significantly reduced, which has good practical value and economic value.

[0113] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A CO2 solubilizing and viscosity reducing agent, characterized in that: The CO2 solubilizing and viscosity reducing agent contains component A and supercritical CO2; the component A contains: ethylene glycol dimethyl ether, sodium lauryl sulfonate, and an emulsion stabilizer; the emulsion stabilizer is sodium polyphosphate and / or polyacrylamide; In the component A, the mass ratio of the ethylene glycol dimethyl ether, the sodium lauryl sulfate, and the emulsion stabilizer is: 3-4:1-2:1; The mass ratio of the component A to the supercritical CO2 is 1:1.86-3.

2. The CO2 solubilizing and viscosity reducing agent according to claim 1, wherein The mass ratio of the ethylene glycol dimethyl ether to the sodium lauryl sulfonate is 3-4:

1.

3. The CO2 solubilizing and viscosity reducing agent according to claim 1 or 2, wherein The emulsion stabilizer is a combination of sodium polyphosphate and polyacrylamide in a mass ratio of 0.1-0.15:

1.

4. The CO2 solubilizing and viscosity reducing agent according to claim 1 or 2, wherein The purity of CO2 in the CO2-containing gas stream used to prepare the supercritical CO2 is greater than 80%.

5. A method for preparing the CO2 solubilizing and viscosity reducing agent according to any one of claims 1 to 4, characterized in that: The method includes: The components in component A are stirred and mixed with supercritical CO2 to obtain the CO2 solubilizing and viscosity reducing agent; the component A contains ethylene glycol dimethyl ether, sodium lauryl sulfate, and an emulsion stabilizer; The stirring and mixing conditions include: temperature of 50-70° C., pressure of 13-18 MPa, and stirring speed of 120-240 rpm.

6. Use of the CO2 solubilizing and viscosity reducing agent according to any one of claims 1 to 4 in heavy oil production.

7. The use according to claim 6, wherein: The wax content of the thick oil is 15-40 wt % and the viscosity is 800-2800 mPa·s.

8. A method for heavy oil production, characterized in that: The method comprises: contacting and reacting a CO2 solubilizing and viscosity reducing agent with a raw material heavy oil; the mass ratio of the CO2 solubilizing and viscosity reducing agent to the raw material heavy oil is 3-5:100; The CO2 solubilizing and viscosity reducing agent is the CO2 solubilizing and viscosity reducing agent according to any one of claims 1 to 4.

9. The method according to claim 8, wherein The conditions of the contact reaction include: temperature of 50-70° C. and time of 5-10 h.

10. The method according to claim 8 or 9, wherein: The raw material heavy oil has a wax content of 15-40 wt% and a viscosity of 800-2800 mPa·s.

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