Oil displacement agent as well as preparation method and application thereof

Abstract

The invention relates to an oil-displacing agent, which is branched hydroxyl sulfo-containing betaine with a structure as shown in the following formula (I): # imgabs0 #, wherein R1 is C4-C10 alkyl; r2 is alkyl of C3-C8; m is an integer from 2 to 10. The invention also relates to a preparation method and application of the oil-displacing agent.

Description

Technical Field

[0001] The present invention relates to a chemical agent for oilfield development, and particularly to a displacement agent, a preparation method and uses thereof. Background Art

[0002] In China, heavy oil resources are abundant, with reserves accounting for more than 1 / 3 of China's oil reserves, having great resource potential. However, heavy oil has high viscosity and poor fluidity, so it is very difficult to economically and effectively exploit heavy oil reservoirs using the general exploitation methods used in light oil exploitation. Therefore, in view of the characteristics of high viscosity of heavy oil, technologies such as heavy oil thermal recovery and heavy oil cold recovery have been proposed. At present, the main heavy oil exploitation method is thermal recovery, and development methods such as steam stimulation, steam flooding, and in-situ combustion are mostly used. However, a large amount of heat energy is lost in the near-wellbore area, the utilization rate is greatly reduced, the development effect gradually declines, and its process is complex, and problems such as gas channeling are serious, restricting the continuous and stable development of thermal recovery in heavy oil development. The heavy oil cold recovery process is a method of exploiting heavy oil reservoirs by using physical or chemical methods to improve the fluidity of heavy oil without relying on high-temperature and high-pressure heat media generated externally to heat the crude oil in the reservoir. The cold recovery method can not only reduce the exploitation cost, but also reduce the damage to the formation, and is an effective way to improve the productivity of oil wells. Currently, the commonly used heavy oil cold recovery technologies are mainly viscosity reducer flooding, and the viscosity reducers used are mainly oil-soluble viscosity reducers and water-soluble viscosity reducers. Among them, oil-soluble viscosity reducers have high costs and high safety and environmental protection risks in on-site use, and are generally used in small doses on-site. Water-soluble viscosity reducers are widely used in heavy oil reservoir exploitation due to their small dosage, low cost, and small impact on oil products. The currently commonly used water-soluble viscosity reducers have the following problems in on-site applications: poor micro-power emulsification performance; high oil product selectivity; the viscosity of its aqueous solution is similar to that of water and is relatively low, and it is prone to channeling after being injected into the formation.

[0003] Therefore, there is still a need to provide a new displacement agent to at least partially solve the problems existing in the prior art. Summary of the Invention

[0004] An object of the present invention is to solve the above problems of the prior art and provide a displacement agent, which is a branched hydroxy sulfobetaine having the following formula (I) structure:

[0005]

[0006] Wherein, R 1 is an alkyl group of C 4 -C 10 ;

[0007] R 2 is an alkyl group of C 3 -C 8 ;

[0008] M is an integer from 2 to 10.

[0009] In another aspect, the present invention also provides a method for preparing the oil displacement agent, which comprises the following steps:

[0010] (1) Reacting an alkyl amide hydroxy sulfobetaine having an olefinic bond in the alkyl moiety with formic acid in the presence of an oxidant under an inert atmosphere and elevated temperature to obtain an intermediate product A;

[0011] (2) Reacting the intermediate product A obtained in step (1) with a monohydric alcohol at an elevated temperature to obtain a product of the oil displacement agent having the structure of formula (I);

[0012] (3) Optionally purifying the product obtained in step (2) to obtain a purified oil displacement agent having the structure of formula (I).

[0013] In yet another aspect, the present invention also provides the use of the oil displacement agent for improving the recovery rate of water-flooded heavy oil reservoirs.

[0014] The oil displacement agent of the present invention is a branched amphoteric surfactant. After the tail group is branched, the interfacial activity is increased, and it has high performance in stripping and dispersing crude oil and low oil product selectivity. Moreover, the head group contains hydroxy sulfonate, which increases the solubility and temperature and salt tolerance. After the oil displacement agent is injected into the formation, it can micro-dynamically emulsify crude oil in situ to reduce the viscosity of crude oil, and can form worm-like micelles in formation water to increase viscosity, solving the problem of easy channeling in the formation. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the nuclear magnetic resonance spectrum of the present invention.

[0016] Figure 2 is the emulsification effect when the concentration of the branched hydroxy sulfonate-containing betaine prepared in Example 1 of the present invention is 0.3% by weight.

[0017] Figure 3 is the emulsification effect when the concentration of the commonly used oil displacement agent in the oil field used in Table 1 is 0.3% by weight.

[0018] Figure 4 is the surface tension of the branched hydroxy sulfonate-containing betaine prepared in Example 1 of the present invention at different weight concentrations.

[0019] Figure 5 is the curve of the viscosity of the branched hydroxy sulfonate-containing betaine prepared in Example 1 of the present invention varying with the weight concentration. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention provides an oil displacement agent, which is a branched hydroxy

[0021] sulfonate-containing betaine having the following formula (I):

[0022]

[0023] wherein R 1 is C 4 -C 10 alkyl;

[0024] R 2 is C 3 -C 8 alkyl;

[0025] M is an integer from 2 to 10.

[0026] In one embodiment of the present invention, in the structure of formula (I), R 1 is C 6 -C 8 alkyl; R 2 is C 4 -C 6 alkyl; M is an integer from 2 to 8.

[0027] In one embodiment of the present invention, the oil displacement agent is a hydroxy sulfobetaine having the following structural formula:

[0028]

[0029] or any combination thereof in any proportion.

[0030] The present invention also provides a method for preparing the oil displacement agent, which comprises the following steps:

[0031] (1) In an inert atmosphere and at an elevated temperature, in the presence of an oxidizing agent, reacting an alkyl amide hydroxy sulfobetaine having an olefinic bond in the alkyl moiety with formic acid to obtain an intermediate product A;

[0032] (2) Reacting the intermediate product A obtained in step (1) with a monohydric alcohol at an elevated temperature to obtain a product of the oil displacement agent having the structure of formula (I);

[0033] (3) Optionally purifying the product obtained in step (2) to obtain the oil displacement agent having the structure of formula (I).

[0034] In the context of the present application, the purification method in step (3) is known per se to those skilled in the art, such as distillation, crystallization, chromatography, etc. Preferably, for economic reasons, the product of the oil displacement agent having the structure of formula (I) prepared in the present application can be directly used in the production process without purification, without affecting the interfacial properties of the oil displacement agent.

[0035] In step (3), the product of the oil displacement agent containing the structure of formula (I) contains at least 90% by weight of the oil displacement agent of the structure of formula (I), and the balance is reaction raw materials and by-product short-chain hydroxysulfobetaine, preferably contains at least 92% by weight of the oil displacement agent of the structure of formula (I), especially at least 95% by weight of the oil displacement agent of the structure of formula (I), in each case based on the total amount of the product of the oil displacement agent containing the structure of formula (I).

[0036] In one embodiment of the present invention, the oxidizing agent in step (1) is selected from one or more of hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium monopersulfate, strontium peroxide.

[0037] In one embodiment of the present invention, the weight ratio of alkylamide hydroxysulfobetaine, formic acid and oxidizing agent in step (1) is 70:5 - 10:1 - 5, preferably 70:6 - 8:2 - 3.

[0038] In one embodiment of the present invention, the alkylamide hydroxysulfobetaine in step (1) is selected from one or more of hexadecene amide hydroxysulfobetaine, oleic acid amide hydroxysulfobetaine and erucic acid amide hydroxysulfobetaine; their structures are as follows:

[0039]

[0040] In one embodiment of the present invention, the monohydric alcohol in step (2) is a C 3 -C 8 alkanol, such as propanol, butanol, pentanol, hexanol, heptanol, octanol or any mixture thereof, preferably n-butanol or n-pentanol, or a mixture in any proportion thereof.

[0041] In one embodiment of the present invention, the weight ratio of alkylamide hydroxysulfobetaine to monohydric alcohol is 70:15 - 30, and the optimal is 70:16 - 25.

[0042] The present invention also provides the use of the said oil displacement agent for improving the recovery rate of waterflooding heavy oil reservoirs. The said oil displacement agent is usually formulated for use as an aqueous solution of 0.5% - 0.6% by weight. In the present invention, the concentration of the oil displacement agent is calculated based on the amount of the pure oil displacement agent compound in the prepared product.

[0043] In the context of the present application, heavy oil has the meaning well-known in the art, and it generally refers to crude oil with a viscosity greater than 100 mPa·s and a relative density greater than 0.92 according to the Chinese heavy oil classification standard.

[0044] In one embodiment of the present invention, the preparation method of the oil displacement agent of the present invention specifically comprises the following steps:

[0045] (1) Add a certain amount of alkyl amide hydroxy sulfobetaine with an olefin bond in the alkyl part to the reactor, continuously introduce nitrogen into the reactor, stir, and raise the temperature to the reaction temperature of 60 - 90 °C. Add a certain amount of formic acid and oxidant in proportion, and react for 1 - 5 h to obtain intermediate product A;

[0046] (2) When the temperature in the reactor in step (1) drops to 30 - 50 °C, add a certain amount of monohydric alcohol to the product A obtained in step (1), stir for 10 - 20 min, then raise the temperature to the reaction temperature of 90 - 130 °C, stop heating after reacting for 5 - 8 h, and stop stirring and introduce nitrogen after the temperature in the reactor drops to room temperature to obtain a product containing the oil displacement agent with the structure of formula (I);

[0047] (3) Optionally, purify the product obtained in step (2) to obtain the oil displacement agent with the structure of formula (I).

[0048] Further, the temperature in step (1) is preferably 70 - 85 °C, and the reaction time is 1.5 - 2.5 h;

[0049] Further, the alcohol in step (1) is preferably n - butanol or n - pentanol, or a mixture of any ratio thereof;

[0050] Further, the weight ratio of alkyl amide hydroxy sulfobetaine, formic acid and oxidant in step (1) is 70:5 - 10:1 - 5, preferably 70:6 - 8:2 - 3.

[0051] Further, the weight ratio of alkyl amide hydroxy sulfobetaine to monohydric alcohol in step (2) is 70:15 - 30, and the optimal ratio is 70:16 - 25.

[0052] Further, the reaction temperature in step (2) is 100 - 120 °C, and the reaction time is 6 - 7 h.

[0053] Unexpectedly, it has been found that the oil displacement agent of the present invention, which is a tail - branched type betaine, has increased interfacial activity after tail - branching, and the head group containing hydroxy sulfonate increases solubility and temperature and salt tolerance. Compared with the commonly used viscosity reducers in oil fields, not only the emulsifying viscosity - reducing performance is enhanced, but also the selectivity for oil products is reduced, the applicable crude oil range is wider, and different from the fact that the viscosity of the commonly used viscosity reducer in aqueous solution is approximately the same as that of water, this profile - control and displacement agent can form worm - like micelles in water, greatly increasing the water - phase viscosity. After being injected into the formation, it can prevent channeling and also play a role in microscopic profile control, thereby improving the recovery rate of water - flooded heavy - oil reservoirs.

[0054] Example

[0055] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0056] Example 1

[0057] Add 700 kg of erucamide hydroxy sulfobetaine into a reaction kettle. While stirring, introduce nitrogen gas, raise the temperature to 80 °C, add 70 kg of formic acid and 20 kg of hydrogen peroxide. After reacting for 4 h, stop heating. After the temperature drops to 40 °C, add 180 kg of n-pentanol. After stirring for 15 min, raise the temperature to 110 °C. After reacting for 6 h, stop heating. After the reaction kettle cools to room temperature, stop stirring and introducing nitrogen gas, and discharge the material to obtain the product, wherein the content of the target oil displacement agent is 92.6% by weight.

[0058] The NMR spectrum of the obtained product is as Figure 1 shown. It can be seen from the spectrum that the synthesized compound is consistent with the structure of the target oil displacement agent.

[0059] Example 2

[0060] The preparation method is the same as that of Example 1, except that hexadecene amide hydroxy sulfobetaine and n-butanol are used as raw materials. In the obtained product, the content of the target oil displacement agent is 93.2% by weight.

[0061] Example 3

[0062] The preparation method is the same as that of Example 1, except that oleic acid amide hydroxy sulfobetaine is used as the raw material. In the obtained product, the content of the target oil displacement agent is 93.0% by weight.

[0063] Micro-dynamic emulsification performance test:

[0064] The micro-dynamic emulsification performance is characterized by the micro-dynamic viscosity reduction rate of crude oil. The test method is as follows:

[0065] Record the viscosity of the dehydrated and degassed oil sample of the target reservoir at 50 °C as η 1 ; Prepare an aqueous solution of the oil displacement agent with a mass concentration of 0.5 wt% with clear water. Take 200 g and put it into a glass bottle, add 40 g of the dehydrated and degassed oil sample of the target reservoir. After sealing, place it in an oven at the target oil layer temperature. After keeping it at a constant temperature for 24 h, take out the glass bottle, slowly turn it upside down 180° five times, and then let it stand and cool to room temperature. Take the upper layer oil sample and test its viscosity at 50 °C and record it as η 2 , and the micro-dynamic viscosity reduction rate is calculated according to the following formula:

[0066]

[0067] Where: η 0 —— Micro - dynamic viscosity reduction rate;

[0068] η 1 —— Viscosity of dehydrated and degassed oil sample in the target reservoir, mPa·s;

[0069] η 2 —— Viscosity of crude oil after micro - dynamic emulsification, mPa·s.

[0070] The comparison of the micro - dynamic emulsification performance between the product synthesized in Example 1 and the commonly used water - soluble oil displacement agents in oilfields is shown in Table 1 and Figures 2-3 as follows.

[0071] The experimental process is as follows: In a test tube, crude oil and an aqueous solution of the oil displacement agent at 0.3 wt% are mixed according to a weight ratio of 2:8, taken out after being placed in an oven at 70 °C for 2 h, the test tube is inverted up and down 5 times and then left to stand, the emulsification situation at different times is observed, the viscosity of the upper - layer crude oil before and after viscosity reduction is measured, and the micro - dynamic viscosity reduction rate is measured.

[0072] Table 1 Emulsification situation of the oil displacement agent of the present invention and the comparative oil displacement agent with a concentration of 0.3 wt% prepared with Shengli II - type brine and different crude oils

[0073]

[0074] From the above data, it can be seen that the viscosity reduction rates of crude oils with different viscosities in different blocks measured by using the product synthesized in Example 1 are all above 50%, indicating that the applicable range of crude oils is relatively wide and the oil product selectivity is high.

[0075] Surface tension performance test:

[0076] The surface tension of the product synthesized in Example 1 was tested, and the test method was carried out according to the standard SY / T5370 - 2018, and the results are as Figure 4 follows.

[0077] As Figure 4 shown, the product of Example 1 has a lower surface tension, the stronger the ability to reduce the interfacial energy, and the higher the activity.

[0078] Viscosity performance test:

[0079] The preparation method of Shengli II type brine is as follows: Add 4901.03 g of distilled water into a 5 L narrow-mouth bottle, place a magnetic stir bar in it and then put it on a magnetic stirrer. Start the stirrer to form a vortex in the solution, and sequentially add the following substances in order: 5.7155 g of anhydrous calcium chloride, 4.3201 g of magnesium chloride hexahydrate, and 88.934 g of sodium chloride. Wait for each reagent to completely dissolve before adding another one. Stir with a magnetic stirrer for 15 min and then set aside. The total salinity of the obtained solution is 19334 mg / L, and the total amount of calcium ions and magnesium ions is 514 mg / L. The prepared brine must be homogeneous and transparent without precipitation, and its shelf life is 7 days.

[0080] The aqueous solution viscosities of the products synthesized in Example 1 with different concentrations are as Figure 5 shown. The viscosity measurement of the present invention was carried out in the above-mentioned Shengli II type brine. The viscometer is Brookfield DV-Ⅲ type, and rotor No. 0 was selected, with a rotation speed of 6 revolutions per minute. It can be Figure 5 seen that the aqueous phase viscosity of the water after adding the oil displacement agent of the present invention increases greatly, which means that it can prevent channeling after being injected into the formation.

[0081] From the above experimental results, it can be seen that the product of Example 1 of the present invention has a lower surface tension, better emulsifying viscosity reduction effect than the commonly used viscosity reducers in oilfields, lower selectivity for oil products, and high activity of the oil displacement agent.

[0082] Application Example

[0083] The oil displacement agent of the present invention can be injected from a water well, and the on-site use concentration is generally 0.5%-0.6% by weight. For the profile control of high water cut well groups, generally, a plugging slug is injected first before injecting the oil displacement agent slug of the present invention, and generally 2000-6000 m 3 is injected according to needs. After the injection is completed, normal water injection can be carried out without shut-in, which can play a role in controlling water production and increasing oil production. If it is a cold production water flooding heavy oil reservoir, the plugging slug does not need to be injected and the oil displacement agent slug is directly injected. After the injection, normal water injection is directly carried out, which can play a role in reducing viscosity and improving displacement efficiency.

[0084] If the oil displacement agent of the present invention is injected from an oil well, generally 200 m 3 -500 m 3 is injected. After the injection, about 30 m 3 of water injection displacement is carried out. After shut-in for 2-3 days, production can be carried out, which can play a role in reducing viscosity, increasing liquid production and enhancing efficiency.

[0085] The product of Example 1 of the present invention is used in a well group of an oil production plant in Shengli Oilfield: This well group is a water flooding heavy oil reservoir with a reservoir temperature of 60 °C, a water salinity of 17800 mg / L, one water well corresponding to five oil wells, and the daily liquid production of the well group is 56 cubic meters and the daily oil production is 6.5 tons.

[0086] The product of Example 1 of the present invention was formulated into a solution with a concentration of 0.5% by weight, injected into 6000 cubic meters. The daily liquid production of the well group was 56 cubic meters, the daily oil production was 18 tons, and the cumulative increased oil production was 1600 tons, achieving good results.

[0087] The above embodiments are only illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An oil displacement agent, which is a branched hydroxy sulfobetaine having the following formula (I) structure: wherein R 1 is C 4 -C 10 alkyl; R 2 is C 3 -C 8 alkyl; M is an integer from 2 to 10.

2. The oil displacement agent according to claim 1, wherein R 1 is an alkyl group of C 6 -C 8 ; R 2 is an alkyl group of C 4 -C 6 ; and M is an integer from 2 to 8.

3. The oil displacement agent according to claim 1, which is a branched hydroxy sulfobetaine having the following structural formula: Or any combination thereof in any proportion.

4. A method for preparing the oil displacement agent according to any one of claims 1-3, which comprises the following steps: (1) Under an inert atmosphere and elevated temperature, reacting an alkyl amide hydroxy sulfobetaine having an olefinic bond in the alkyl moiety with formic acid in the presence of an oxidizing agent to obtain an intermediate product A; (2) Reacting the intermediate product A obtained in step (1) with a monohydric alcohol at an elevated temperature to obtain a product of the oil displacement agent having the structure of formula (I); (3) Optionally purifying the product obtained in step (2) to obtain a purified oil displacement agent having the structure of formula (I).

5. The method according to claim 4, wherein the oxidizing agent in step (1) is selected from one or more of hydrogen peroxide, sodium peroxide, potassium peroxide, calcium peroxide, magnesium peroxide, zinc peroxide, potassium monopersulfate, strontium peroxide.

6. The method according to claim 4, wherein the weight ratio of the alkyl amide hydroxy sulfobetaine, formic acid and oxidizing agent in step (1) is 70:5-10:1-5.

7. The method according to claim 6, wherein the weight ratio of the alkyl amide hydroxy sulfobetaine, formic acid and oxidizing agent in step (1) is 70:6-8:2-3.

8. The method according to claim 4, wherein the alkyl amide hydroxy sulfobetaine in step (1) is selected from one or more of hexadecene amide hydroxy sulfobetaine, oleic acid amide hydroxy sulfobetaine, erucic acid amide hydroxy sulfobetaine.

9. The method according to claim 4, wherein the monohydric alcohol in step (2) is a C 3 -C 8 alkan-ol, such as propanol, butanol, pentanol, hexanol, heptanol, octanol or any mixture thereof.

10. The method according to claim 9, wherein the monohydric alcohol in step (2) is n-butanol or n-pentanol, or any mixture thereof.

11. The method according to claim 4, wherein the weight ratio of the alkyl amide hydroxy sulfobetaine to the monohydric alcohol is 70:15-30, preferably 70:16-25.

12. The method according to claim 11, wherein the weight ratio of the alkyl amide hydroxy sulfobetaine to the monohydric alcohol is 70:16-25.

13. Use of the oil displacement agent according to any one of claims 1-3 or the oil displacement agent obtained by the method according to any one of claims 4-12 for improving the recovery rate of waterflooded heavy oil reservoirs.

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