In-situ emulsification water plugging system for oil well water plugging and preparation method thereof

Abstract

The invention relates to the technical field of petrochemical engineering, in particular to an in-situ emulsification water shutoff system for oil well water shutoff and a preparation method of the in-situ emulsification water shutoff system. The system comprises an oil phase, modified molybdenum disulfide nanosheets and an emulsifier, the modified molybdenum disulfide nanosheet is obtained by modifying a molybdenum disulfide nanosheet through an organic solvent. The oil-based water plugging system prepared from the modified molybdenum disulfide nanosheet and the emulsifier can be injected into an underground in-situ emulsified water phase, so that the selective plugging capacity of the plugging agent in a stratum is improved, namely, the plugging effect is generated only at a water outlet layer; and through the synergistic effect of the nanosheets and the emulsifier, the viscosity of the emulsion and the capability of emulsifying water are improved, and the plugging efficiency is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petrochemical engineering, and particularly relates to an in-situ emulsifying water plugging system for oil wells and a preparation method thereof. Background Art

[0002] Emulsion is an important water plugging system for oil wells. The emulsion is mainly composed of a surfactant as an emulsifier to emulsify the oil phase and water to form a relatively stable profile control and displacement system. However, the water-in-oil emulsion water plugging system undergoes emulsification on the ground, resulting in too high initial viscosity of the emulsion and great difficulty in injection. The water-in-oil emulsion has a lower injection pressure, but the plugging strength is smaller. The traditional active oil water plugging system adds an emulsifier to the oil phase, so that underground emulsification occurs with the produced water in the formation, increasing the viscosity to play a role in water plugging. However, in the emulsion stabilized by an oil-based emulsifier, the ability of the active oil to emulsify formation water is poor. When the mass ratio of formation water to active oil is greater than 7:1, an oil-in-water emulsion cannot be formed, resulting in the inversion of the emulsion type to a water-in-oil emulsion type, causing a decrease in viscosity and a deterioration in the plugging effect.

[0003] Chinese Patent Document CN202110396640.9 discloses a water-in-oil emulsion water plugging agent based on ethylene tar, a preparation method thereof and an application. The water-in-oil emulsion water plugging agent based on ethylene tar comprises the following components in percentage by weight: 1.0% - 2.0% of an oil-soluble anionic surfactant, 1.0% - 2.0% of a non-ionic surfactant, 0.05% - 0.15% of a co-surfactant, 1.0% - 2.0% of a modified nanoparticle, 30% - 45% of ethylene tar, and the balance being water.

[0004] Chinese Patent Document CN201510535437.X discloses a profile control and water plugging agent for heavy oil emulsion phase inversion. The profile control and water plugging agent for heavy oil emulsion phase inversion comprises: 50 of active heavy oil, 30 of water, 10 of limestone powder, 0.5 - 0.7 of an emulsifier, 2 - 7 of a phase inversion agent, and 0.3 - 0.7 of a stabilizer. The invention uses heavy oil that does not damage the oil reservoir as the main profile control and water plugging material. Before injection into the bottom layer, a water-in-oil emulsion with low viscosity is first prepared. After injection into the formation, the temperature of the formation and the added phase inversion agent are used to change the water-in-oil heavy oil emulsion into a water-in-oil emulsion with greater viscosity. Because the stabilizer and limestone powder are added to the profile control and water plugging agent, the water-in-oil emulsion entering the formation is more stable and has a very high viscosity, and can also have a good water plugging effect on the rock layer with large gaps.

[0005] Chinese Patent Document CN02128876.3 discloses a method for profile control and water plugging by phase inversion of heavy oil emulsion and a phase inversion agent. It is achieved by adding 0.4 - 1.0% water-in-oil emulsion and 3% - 10% phase inversion agent to the heavy oil system and then injecting it into the formation. The water-in-oil emulsion is a mixture of non-ionic surfactants such as OP series, Tween series, Span series, and sodium carboxylate and inorganic salts such as sodium carbonate; the phase inversion agent is a mixture of oil-soluble surfactants such as OP series or Span series or organic acid esters and solid powders such as rosin powder, asphalt powder, coal powder, or bentonite.

[0006] The water plugging system injected in the above-mentioned invention forms an emulsion on the ground and forms a water-in-oil emulsion after entering the ground to achieve the purpose of water plugging. However, since a large amount of water is emulsified during the injection process, the ability to further emulsify water in the formation is greatly weakened. At the same time, traditional stable emulsions mainly use oil-soluble surfactants, and their ability to emulsify water and the stability of the emulsion are lower than those of emulsions stabilized by nanoparticles. In the currently reported technologies, spherical particles such as nano-silica are mainly used to stabilize emulsions.

[0007] Nanomaterials can adsorb on the oil-water interface to stabilize emulsions. According to their shapes, they can be divided into spherical, nanosheet, and rod-shaped nanomaterials. Spherical and rod-shaped nanoparticles exist in the form of "point-plane" contact at the oil-water interface, resulting in a small effective contact area between the particles and the interface, a large amount of material used, and unsatisfactory economic benefits. Therefore, there is an urgent need to improve the plugging efficiency of the water plugging system. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the present invention provides an in-situ emulsifying water plugging system for oil well water plugging and its preparation method. The oil-based water plugging system prepared by the present invention using modified molybdenum disulfide nanosheets and emulsifiers can achieve in-situ emulsification of the water phase after being injected underground, improve the selective plugging ability of the plugging agent in the formation, that is, the plugging effect only occurs at the water-producing layer, and the viscosity of the emulsion and the ability to emulsify water are improved through the synergistic effect of nanosheets and emulsifiers, further improving the plugging efficiency.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention provides an in-situ emulsifying water plugging system for oil well water plugging, and the system includes an oil phase, modified molybdenum disulfide nanosheets, and an emulsifier; the modified molybdenum disulfide nanosheets are obtained by modifying molybdenum disulfide nanosheets with an organic solvent.

[0011] Furthermore, the mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.05% - 1.0%; the mass fraction of the emulsifier in the oil phase is 1% - 10%.

[0012] Further, the preparation method of the modified molybdenum disulfide nanosheets is as follows:

[0013] (1) Ammonium molybdate and thiourea are added to an aqueous solution. After complete dissolution, the solution is transferred to a high-pressure reactor and heated for reaction. After the reaction, the precipitate is centrifuged, washed, and dried to obtain molybdenum disulfide nanosheets;

[0014] (2) The molybdenum disulfide nanosheets are placed in a solvent, and n-octadecanethiol is added. The mixture is stirred for reaction. After centrifugation, washing, and drying, modified molybdenum disulfide nanosheets are obtained.

[0015] Furthermore, in step (1), the reaction time is 8 - 16 h, and the reaction temperature is 180 - 220 °C.

[0016] Furthermore, in step (1), the weight ratio of ammonium molybdate to thiourea is 1:1 - 10.

[0017] Furthermore, in step (2), the mass ratio of molybdenum disulfide nanosheets to n-octadecanethiol is 1:0.05 - 0.15.

[0018] Furthermore, in step (2), the solvent is water or ethanol.

[0019] Further, the oil phase is thin oil.

[0020] Further, the emulsifier is a fatty acid ester-based oil-based emulsifier.

[0021] The present invention also provides a preparation method of the in-situ emulsifying water plugging system for oil well water plugging described above. The method includes the following steps:

[0022] An emulsifier is added to thin oil and stirred for dissolution; then modified molybdenum disulfide nanosheets are added and stirred thoroughly.

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

[0024] 1. The present invention uses nano-sheet molybdenum disulfide, and by modifying the molybdenum disulfide nanosheets, the molybdenum disulfide is changed from strongly hydrophilic to weakly hydrophilic, so that it can be adsorbed on the oil-water interface.

[0025] 2. The oil-based water plugging system prepared by the present invention using modified molybdenum disulfide nanosheets and an emulsifier can realize in-situ emulsification of the water phase injected underground, improving the selective plugging ability of the plugging agent in the formation - the plugging effect only occurs in the water-producing layer.

[0026] 3. The present invention improves the viscosity of the emulsion and the ability to emulsify water through the synergistic effect of modified molybdenum disulfide nanosheets and an emulsifier, further improving the plugging efficiency. Specific Embodiments

[0027] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention pertains.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular forms are also intended to include the plural forms. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0029] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0030] The reagents and materials used in the examples, unless otherwise specified, can be obtained commercially or prepared according to existing technologies; the methods used, unless otherwise specified, are all existing technologies.

[0031] Example 1

[0032] An in-situ emulsifying water plugging system for oil wells, which is composed of an oil phase, modified molybdenum disulfide nanosheets, and an emulsifier.

[0033] The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.2%; the mass fraction of the emulsifier in the oil phase is 1%.

[0034] The oil phase is light oil, and the emulsifier is a fatty acid ester oil-based emulsifier.

[0035] The modified molybdenum disulfide nanosheets are prepared by the following method:

[0036] (1) Ammonium molybdate and thiourea are mixed in 100 mL of deionized water at a mass ratio of 1:10 g and stirred for 2 h. The obtained solution is transferred to a high-pressure reactor with a capacity of 150 mL and heated in an oven at 200 °C for 12 h;

[0037] (2) After the reaction is completed and the reactor is cooled to room temperature, the product is centrifuged and washed several times to remove impurities and reaction by-products, and placed in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets;

[0038] (3) 1 g of molybdenum disulfide nanosheets are dispersed in 100 mL of ethanol solution and ultrasonicated for 30 min at room temperature; then 0.1 g of n-octadecanol is added and stirred for 24 h;

[0039] (4) Centrifuge and wash the reaction solution to remove the ungrafted modifier and reaction by-products, and place it in a vacuum drying oven at 60 °C for drying to obtain modified molybdenum disulfide nanosheets.

[0040] The preparation method of the water plugging system is as follows:

[0041] Add a fatty acid ester-based oil-in-water emulsifier to the thin oil in the oilfield and stir to dissolve it; then add the modified molybdenum disulfide nanosheets prepared by the above method and stir well to disperse them to obtain the product.

[0042] Mix the above water plugging system with 8 times its own mass of formation water in a beaker and stir to form an oil-in-water emulsion, indicating that the system can emulsify 8 times its own mass of formation water without inverting to a water-in-oil emulsion.

[0043] Inject the water plugging system into a sand-packed tube with a permeability of 1842×10 -3 μm 2 Subsequent water flooding shows that after the water plugging system emulsifies water in situ, the water-phase permeability decreases by 85%.

[0044] Example 2

[0045] An in-situ emulsifying water plugging system for oil wells, which is composed of an oil phase, modified molybdenum disulfide nanosheets and an emulsifier.

[0046] The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.05%; the mass fraction of the emulsifier in the oil phase is 5%.

[0047] The oil phase is thin oil, and the emulsifier is a fatty acid ester-based oil-in-water emulsifier.

[0048] The modified molybdenum disulfide nanosheets are prepared by the following method:

[0049] (1) Mix ammonium molybdate and thiourea in a mass ratio of 1:10 g in 100 mL of deionized water and stir for 2 h, transfer the obtained solution to a high-pressure reactor with a capacity of 150 mL and heat it in an oven at 220 °C for 8 h;

[0050] (2) After the reaction is completed and the reactor is cooled to room temperature, centrifuge and wash the product several times to remove impurities and reaction by-products, and place it in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets;

[0051] (3) Disperse 1 g of molybdenum disulfide nanosheets in 100 mL of ethanol solution and ultrasonicate for 30 min at room temperature; then immediately add 0.05 g of n-octadecanol and stir for 24 h;

[0052] (4) Centrifuge and wash the reaction solution to remove the ungrafted modifier and reaction by-products, and place it in a vacuum drying oven at 60 °C for drying, then modified molybdenum disulfide nanosheets can be obtained.

[0053] The preparation method of the water plugging system is the same as that described in Example 1.

[0054] Inject the water plugging system into a sand-packed tube with a permeability of 1229×10 -3 μm 2 . Subsequent water flooding shows that after the in-situ emulsification of water by the water plugging system, the water phase permeability decreases by 82%.

[0055] Example 3

[0056] An in-situ emulsifying water plugging system for oil wells, which consists of an oil phase, modified molybdenum disulfide nanosheets and an emulsifier.

[0057] The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.1%; the mass fraction of the emulsifier in the oil phase is 3%.

[0058] The oil phase is thin oil, and the emulsifier is a fatty acid ester-based oil emulsifier.

[0059] The modified molybdenum disulfide nanosheets are prepared by the following method:

[0060] (1) Mix ammonium molybdate and thiourea in a mass ratio of 1:10 g in 100 mL of deionized water and stir for 2 h. Transfer the obtained solution to a high-pressure reactor with a capacity of 150 mL and heat it in an oven at 180 °C for 16 h;

[0061] (2) After the reaction is completed and the reactor is cooled to room temperature, centrifuge and wash the product several times to remove impurities and reaction by-products, and place it in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets;

[0062] (3) Disperse 1 g of molybdenum disulfide nanosheets in 100 mL of ethanol solution and ultrasonicate for 30 min at room temperature; then add 0.15 g of n-octadecanol and stir for 24 h;

[0063] (4) Centrifuge and wash the reaction solution to remove the ungrafted modifier and reaction by-products, and place it in a vacuum drying oven at 60 °C for drying, then modified molybdenum disulfide nanosheets can be obtained.

[0064] The preparation method of the water plugging system is the same as that described in Example 1.

[0065] Inject the water plugging system into a sand-packed tube with a permeability of 1286×10 -3 μm 2The saturated crude oil sand-filled tube, subsequent oil flooding showed that the water plugging system had no effect on the oil phase permeability in the oil-bearing sand-filled tube, indicating its excellent characteristic of plugging water without plugging oil.

[0066] Example 4

[0067] An in-situ emulsifying water plugging system for oil wells, the system consists of an oil phase, modified molybdenum disulfide nanosheets and an emulsifier.

[0068] The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 1.0%; the mass fraction of the emulsifier in the oil phase is 1.0%.

[0069] The oil phase is light oil, and the emulsifier is a fatty acid ester-based oil emulsifier.

[0070] The modified molybdenum disulfide nanosheets are made by the following method:

[0071] (1) Ammonium molybdate and thiourea are mixed in 100 mL of deionized water at a mass ratio of 1:1 g and stirred for 2 h. The resulting solution is transferred to a high-pressure reactor with a capacity of 150 mL and heated in an oven at 200 °C for 12 h;

[0072] (2) After the reaction is completed and the reactor is cooled to room temperature, the product is centrifuged and washed several times to remove impurities and reaction by-products, and placed in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets;

[0073] (3) 1 g of molybdenum disulfide nanosheets is dispersed in 100 mL of water and sonicated at room temperature for 30 min; then 0.05 g of n-octadecanol is added and stirred for 24 h;

[0074] (4) The reaction solution is centrifuged and washed to remove unreacted modifiers and reaction by-products, and placed in a vacuum drying oven at 60 °C for drying to obtain modified molybdenum disulfide nanosheets.

[0075] The preparation method of the water plugging system is the same as that described in Example 1.

[0076] Example 5

[0077] An in-situ emulsifying water plugging system for oil wells, the system consists of an oil phase, modified molybdenum disulfide nanosheets and an emulsifier.

[0078] The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.05%; the mass fraction of the emulsifier in the oil phase is 10%.

[0079] The oil phase is light oil, and the emulsifier is a fatty acid ester-based oil emulsifier.

[0080] The modified molybdenum disulfide nanosheets are made by the following method:

[0081] (1) Mix ammonium molybdate and thiourea in a mass ratio of 1:5 g in 100 mL of deionized water and stir for 2 h. Transfer the obtained solution to a high-pressure reactor with a capacity of 150 mL and heat it in an oven at 200 °C for 12 h;

[0082] (2) After the reaction is completed and the reactor is cooled to room temperature, centrifuge and wash the product several times to remove impurities and reaction by-products, and place it in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets;

[0083] (3) Disperse 1 g of molybdenum disulfide nanosheets in 100 mL of water and sonicate for 30 min at room temperature; then add 0.1 g of n-octadecanol and stir for 24 h;

[0084] (4) Centrifuge and wash the reaction solution to remove un-grafted modifiers and reaction by-products, and place it in a vacuum drying oven at 60 °C to dry, and then modified molybdenum disulfide nanosheets can be obtained.

[0085] The preparation method of the water plugging system is the same as that described in Example 1.

[0086] Comparative Example 1

[0087] An in-situ emulsifying water plugging system for oil well water plugging, which is different from Example 1 in that unmodified molybdenum disulfide nanosheets are used.

[0088] The molybdenum disulfide nanosheets are made by the following method:

[0089] (1) Mix ammonium molybdate and thiourea in a mass ratio of 1:10 g in 100 mL of deionized water and stir for 2 h. Transfer the obtained solution to a high-pressure reactor with a capacity of 150 mL and heat it in an oven at 200 °C for 12 h;

[0090] (2) After the reaction is completed and the reactor is cooled to room temperature, centrifuge and wash the product several times to remove impurities and reaction by-products, and place it in a vacuum drying oven at 60 °C overnight to obtain molybdenum disulfide nanosheets.

[0091] Others are the same as in Example 1.

[0092] Inject the water plugging system into a sand-packed tube with a permeability of 1842×10 -3 μm 2 . Subsequent water flooding shows that after the water plugging system emulsifies water in-situ, the water phase permeability only decreases by 37%.

[0093] Comparative Example 2

[0094] An in-situ emulsifying water plugging system for oil well water plugging, which is different from Example 1 in that the system consists of an oil phase and an emulsifier.

[0095] The preparation method of the water plugging system: Add a fatty acid ester-based oil-based emulsifier to light oil in the oilfield, stir and dissolve to obtain it. Others are the same as in Example 1.

[0096] This system can emulsify formation water 6.5 times its own mass to form a water-in-oil emulsion. However, after continuously increasing the formation water, the emulsion is reversed into an oil-in-water emulsion.

[0097] Comparative Example 3

[0098] An in-situ emulsifying water plugging system for oil wells, different from Example 1 in that the system consists of an oil phase and modified molybdenum disulfide nanosheets.

[0099] The preparation method of the water plugging system: Add 0.2% modified molybdenum disulfide nanosheets to light oil in the oilfield, and stir and disperse fully. Others are the same as in Example 1.

[0100] This system is difficult to mix with formation water to form a water-in-oil emulsion.

[0101] From the above, it can be seen that the modified molybdenum disulfide nanosheets prepared in the embodiments of the present invention can adjust their wettability, participate in the formation of in-situ emulsions, and greatly improve the emulsifying ability and the plugging efficiency of the water phase. The addition of modified molybdenum disulfide nanosheets effectively improves the ability of the system to emulsify water, thereby improving the water plugging effect of the emulsion. Moreover, the synergistic effect of modified molybdenum disulfide nanosheets and emulsifiers has a unique effect on the in-situ formation of water-in-oil emulsions underground.

[0102] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An in-situ emulsification water plugging system for oil well water plugging, It is characterized in that The water plugging system comprises an oil phase, modified molybdenum disulfide nanosheets and an emulsifier; the modified molybdenum disulfide nanosheets are obtained by modifying molybdenum disulfide nanosheets with an organic solvent.

2. The in-situ emulsification water plugging system for oil well water plugging according to claim 1, It is characterized in that The mass fraction of the modified molybdenum disulfide nanosheets in the oil phase is 0.05%-1.0%; the mass fraction of the emulsifier in the oil phase is 1%-10%.

3. The in-situ emulsification water plugging system for oil well water plugging according to claim 1 or 2, It is characterized in that The modified molybdenum disulfide nanosheets are prepared by the following method: (1) adding ammonium molybdate and thiourea to an aqueous solution, and after fully dissolving, transferring the solution to a high-pressure reactor, heating, and reacting, centrifuging after the reaction is completed, washing the precipitate, and drying to obtain molybdenum disulfide nanosheets; (2) placing the molybdenum disulfide nanosheets in a solvent, adding n-octadecyl mercaptan, stirring to react, and obtaining modified molybdenum disulfide nanosheets after centrifugation, washing, and drying.

4. The in-situ emulsification water plugging system for oil well water plugging according to claim 3, It is characterized in that The reaction time in step (1) is 8-16 hours, and the reaction temperature is 180-220°C.

5. The in-situ emulsification water plugging system for oil well water plugging according to claim 3, It is characterized in that In step (1), the weight ratio of ammonium molybdate to thiourea is 1:1-10.

6. The in-situ emulsification water plugging system for oil well water plugging according to claim 3, It is characterized in that In step (2), the mass ratio of molybdenum disulfide nanosheets to n-octadecyl mercaptan is 1:0.05-0.

15.

7. The in-situ emulsification water plugging system for oil well water plugging according to claim 3, It is characterized in that The solvent in step (2) is water or ethanol.

8. The in-situ emulsification water plugging system for oil well water plugging according to claim 3, It is characterized in that The oil phase is thin oil.

9. The in-situ emulsification water plugging system for oil well water plugging according to claim 1, It is characterized in that The emulsifier is a fatty acid ester oil-based emulsifier.

10. The method for preparing the in-situ emulsified water plugging system for oil well water plugging according to claim 1, It is characterized in that The following steps are involved: Add emulsifier to thin oil and stir to dissolve; then add modified molybdenum disulfide nanosheets and stir thoroughly.