Preparation Method of Fluorocarbon Clay Stabilizer for Oil and Gas Fields

Abstract

The present invention belongs to the technical field of oil and gas exploitation and oilfield chemistry, and relates to a preparation method of a fluorocarbon-based clay stabilizer for oil and gas fields. The present invention uses acrylamide, acrylic acid and fluorinated acrylate monomers as raw materials, N,N-dimethylformamide as a solvent, and azobisisobutyronitrile as an initiator to prepare a fluorocarbon-based clay stabilizer through a free radical polymerization reaction. By introducing fluorine-containing groups, the prepared fluorocarbon-based clay stabilizer has excellent anti-hydration swelling performance and chemical stability, and is applicable to oil and gas field drilling, fracturing and water injection operations.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploitation and oilfield chemistry, and relates to a method for preparing a fluorocarbon clay stabilizer for oil and gas fields. Background Art

[0002] In the process of oil and gas field development, drilling, fracturing and water injection operations are three key links, and the hydration and expansion of clay minerals is a common technical problem in the above operations. Clay minerals (such as montmorillonite, illite, rectorite, etc.) are widely present in sedimentary rocks. When they encounter water, they will hydrate and expand, resulting in rock structure destruction, reduced formation permeability and deterioration of working fluid performance. For example, during the drilling process, after the drilling fluid comes into contact with the clay minerals in the formation, the clay minerals will hydrate and expand, which may cause well wall collapse, drill stuck and other problems, seriously affecting drilling efficiency and safety; in shale gas development, after the fracturing fluid comes into contact with the clay minerals in the formation, the hydration and expansion of the clay minerals will cause the cracks to close and the conductivity to decrease, thereby reducing the fracturing effect; in the later stage of oil field development, after the injected water comes into contact with the clay minerals in the formation, the hydration and expansion of the clay minerals will cause the formation porosity to decrease and the permeability to decrease, thereby affecting the water injection effect and the final crude oil recovery rate.

[0003] In recent years, in response to the reservoir damage caused by the hydration and expansion of clay minerals during oil and gas production, domestic and foreign scholars have successively developed a variety of clay stabilizers, mainly including inorganic salts, inorganic cationic polymers, surfactants and organic cationic polymers. Among them, inorganic salts inhibit the hydration and expansion of clay minerals through ion exchange and double layer compression effect, and have the advantages of low cost and strong adaptability. However, the radius of inorganic cations is small, and ion diffusion and ion exchange are easy to lead to desorption, reducing their long-term inhibition ability. Trivalent and above metal ions in inorganic cationic polymers can dissociate under specific conditions to form multi-nuclear hydroxyl bridged complexes, which neutralize the negative charge on the clay surface through electrostatic adsorption, thereby inhibiting expansion and particle migration. Compared with inorganic salts, its stabilization effect is more lasting, but when the pH value is non-neutral, the anti-swelling efficiency is reduced. Cationic surfactants achieve clay stabilization through charge neutralization and wettability regulation, but they have limitations in practical applications; surfactant molecule adsorption may induce wetting reversal phenomenon, forming liquid phase closure, and aggravating the water lock effect of the reservoir. Organic cationic polymers have the characteristics of low dosage, strong adsorption, and acid and alkali resistance. However, their relative molecular mass is relatively high, and they are prone to physical blockage at the pore throats of low permeability reservoirs, resulting in secondary permeability damage, which restricts their applicability in complex reservoirs.

[0004] In view of the problem that the above-mentioned clay stabilizers have limited applicability in certain complex reservoirs, the present invention prepares fluorocarbon clay stabilizers by introducing fluorocarbon chains, which not only significantly improves the hydrophobicity and anti-swelling properties of the stabilizer, but also overcomes the problems of insufficient stability and limited applicability of traditional stabilizers in complex reservoir environments, thereby providing a more efficient and reliable solution for drilling, fracturing and water injection operations in oil field development. Summary of the invention

[0005] The present invention introduces a fluorocarbon chain to prepare a fluorocarbon clay stabilizer, which significantly improves the hydrophobicity and thermal stability of the stabilizer; the fluorocarbon chain has extremely strong hydrophobicity and can form a hydrophobic protective film on the surface of clay minerals, effectively preventing water molecules from entering the interior of clay particles, thereby significantly inhibiting the hydration expansion of the clay; at the same time, the fluorocarbon chain has excellent thermal stability, is not easy to decompose and fail under high temperature and high pressure environments, and can meet the needs under complex geological conditions; in addition, by reasonably designing the monomer ratio and polymerization process, the obtained stabilizer can produce a good inhibitory and anti-swelling effect on various types of clay minerals (such as montmorillonite, illite, rectorite, etc.).

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A method for preparing a fluorocarbon clay stabilizer for oil and gas fields comprises the following steps:

[0007] Step 1: Add three monomers, acrylamide, acrylic acid and fluorinated acrylate, in a container in order, with the weight ratios of 300 parts, 195-150 parts and 5-50 parts respectively, and then add 675-1350 parts of solvent N,N-dimethylformamide; stir and dissolve at room temperature, introduce nitrogen to deoxygenate, and heat to 50°C for standby use;

[0008] Step 2: Take 1-4 parts of azobisisobutyronitrile as an initiator, add 75-150 parts of N,N-dimethylformamide as a solvent, and dissolve to obtain an initiator solution;

[0009] Step 3: Under a nitrogen atmosphere, slowly drop the initiator solution obtained in step 2 into the monomer mixed solution obtained in step 1 for 15 min to 30 min, and slowly heat to 60°C to 75°C, stir, and perform polymerization for 5 h to 10 h;

[0010] Step 4: The reaction product obtained in step 3 is cooled to room temperature, precipitated with anhydrous ethanol, shredded, washed, filtered, vacuum dried at 50°C to 70°C for 24 h to 48 h, and crushed to obtain a fluorocarbon clay stabilizer.

[0011] Furthermore, in step 1, the fluorocarbon chain (—C m F n ) mis 3 - 8, the number of fluorine atoms n is 6 - 17.

[0012] The present invention also provides an application of a fluorocarbon - based clay stabilizer in the fields of oil and gas well drilling, fracturing, water injection development, etc., and the mass concentration of the fluorocarbon - based clay stabilizer is 0.2% - 2.0%.

[0013] The beneficial effects of the present invention are:

[0014] By introducing fluorocarbon chains to prepare the fluorocarbon - based clay stabilizer, the present invention has excellent anti - hydration swelling performance, chemical stability and thermal stability. It not only significantly improves the hydrophobic and anti - swelling properties of the stabilizer, but also overcomes the problems of insufficient stability and limited applicability of traditional stabilizers in complex reservoir environments, providing a more efficient and reliable solution for drilling, fracturing and water injection operations in oilfield development, meeting social and economic benefits and having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the reaction equation diagram of the fluorocarbon - based clay stabilizer;

[0016] Figure 2 is the infrared spectrum diagram of the clay stabilizer PAF - 13;

[0017] Figure 3 is the infrared spectrum diagram of the monomers AM, AA, FA13 and the clay stabilizer PAF - 13;

[0018] Figure 4 is the contact angle test diagram of distilled water and the clay stabilizer PAF - 13 on rectorite;

[0019] Figure 5 is the contact angle test diagram of distilled water and the clay stabilizer PAF - 13 on illite;

[0020] Figure 6 is the swelling curve diagram of distilled water and the clay stabilizer PAF - 13 on rectorite;

[0021] Figure 7 is the swelling curve diagram of distilled water and the clay stabilizer PAF - 13 on illite. DETAILED DESCRIPTION OF THE INVENTION

[0022] The principles and features of the present invention will be described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0023] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0024] The present invention provides a preparation method of a fluorocarbon clay stabilizer for oil and gas fields, comprising the following steps:

[0025] Step 1: Sequentially add three monomers, acrylamide, acrylic acid, and fluorinated acrylate, with the masses of the monomers being 300 parts, 195 - 150 parts, and 5 - 50 parts respectively, and then add 675 - 1350 parts of the solvent N,N-dimethylformamide; at room temperature, stir to dissolve, after purging with nitrogen to remove oxygen, heat up to 50 °C, and set aside;

[0026] Step 2: Take 1 - 4 parts of the initiator azobisisobutyronitrile, add 75 - 150 parts of the solvent N,N-dimethylformamide, and dissolve to obtain an initiator solution;

[0027] Step 3: Under a nitrogen atmosphere, slowly dropwise add the initiator solution obtained in Step 2 to the monomer mixed solution obtained in Step 1, complete the dropping within 15 min - 30 min, and at the same time slowly heat up to 60 °C - 75 °C, stir, and carry out a polymerization reaction for 5 h - 10 h;

[0028] Step 4: Cool the reaction product obtained in Step 3 to room temperature, precipitate with absolute ethanol, cut into pieces, wash, filter, and vacuum dry at 50 °C - 70 °C for 24 h - 48 h, and pulverize to obtain a fluorocarbon clay stabilizer.

[0029] The specific reaction equation is shown in Figure 1 where R is a fluorocarbon chain (—C m F n ), m is 3 - 8, n is 6 - 17.

[0030] The present invention also provides an application of the fluorocarbon clay stabilizer in the fields of oilfield drilling, fracturing, water injection development, etc., and the mass concentration of the fluorocarbon clay stabilizer is 0.2% - 2.0%.

[0031] Example 1: Using acrylamide, acrylic acid, and 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8 - heptadecafluorooctyl acrylate as monomers, prepare the fluorocarbon clay stabilizer PAF - 13, and the specific implementation steps are as follows.

[0032] Step 1: Sequentially add the reaction monomers acrylamide (AM) 6.0 g, acrylic acid (AA) 3.40 mL, 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8 - heptadecafluorooctyl acrylate (FA13) 0.33 mL, and the solvent N,N-dimethylformamide (DMF) 30.0 mL into a three-necked flask. At room temperature, stir to dissolve, after purging with nitrogen to remove oxygen, heat up to 50 °C, and set aside;

[0033] Step 2: Dissolve 0.04 g of the initiator azobisisobutyronitrile (AIBN) in 3 mL of the solvent N,N-dimethylformamide to obtain an initiator solution;

[0034] Step 3: Under a nitrogen atmosphere, slowly drop the initiator solution obtained in Step 2 into the monomer mixed solution obtained in Step 1, while slowly heating up to 65 °C. The dropping time and the heating-up time are controlled within 15 min to 30 min. Stir and carry out the polymerization reaction for 6 h;

[0035] Step 4: Cool the reaction product obtained in Step 3 to room temperature, precipitate with absolute ethanol, cut it into pieces, wash, filter, dry it under vacuum at 65 °C for 48 h, and pulverize it to obtain the fluorocarbon clay stabilizer PAF-13.

[0036] Characterize the molecular structure of the fluorocarbon clay stabilizer prepared in the above example, and further evaluate its inhibitory and anti-swelling properties against common clay minerals (rectorite, illite) in oilfield development. The relevant test results are as follows:

[0037] 1. Structure characterization of the clay stabilizer

[0038] Take out a small amount of the clay stabilizer prepared in the example after vacuum drying, mix it evenly with potassium bromide (spectral pure), press it into a tablet for sample preparation, and then use a Fourier transform infrared spectrometer for testing. The experimental results are as Figure 2 shown. Use the potassium bromide tablet pressing method for acrylamide, acrylic acid, and 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,13,13,13-tridecafluorooctyl acrylate, and test it with a Fourier transform infrared spectrometer. The experimental results are as Figure 3 shown.

[0039] Figure 2 is the infrared spectrogram of the clay stabilizer PAF-13, with the wave number / cm -1 as the abscissa and the transmittance / % as the ordinate. It can be obtained from Figure 2 that the stretching vibration characteristic peaks of O—H in the carboxyl group (—COOH) are at 3549 cm -1 and 3471 cm -1 ; the "double peaks" at 3418 cm -1 and 3214 cm -1 are the stretching vibration characteristic peaks of N—H in the primary amide (O=CH—NH 2 ); the stretching vibration characteristic peak of —CH -1 — in the carbon chain is at 2947 cm 2 ; the stretching vibration characteristic peak of C=O in the ester group (—COOR) is at 1719 cm -1 ; the stretching vibration characteristic peaks of C=O in the carboxyl group and primary amide are at 1654 cm -1 ; the bending vibration characteristic peak of —CH -1 — in the carbon chain is at 1449 cm 2 ; the bending vibration characteristic peak is at 1404 cm -1is the characteristic peak of the stretching vibration of C—N in the primary amide; 1240 cm -1 and 1113 cm -1 are the characteristic peaks of the bending vibration of C—F in —CF 3 and —CF 2 —; 1187 cm -1 is the characteristic peak of the stretching vibration of C—O—C in the ester group; 618 cm -1 is the characteristic peak of the bending vibration of —NH 2 in the primary amide.

[0040] Figure 3 are the infrared spectra of monomers AM, AA, FA13 and clay stabilizer PAF-13, with the wave number / cm -1 as the abscissa and the transmittance / % as the ordinate. By comparing the infrared spectra of monomers AM, AA, FA13 and the synthesized clay stabilizer PAF-13, it is found that the characteristic peaks of the stretching vibration of N—H in the primary amide of AM (3364 cm -1 , 3179 cm -1 ), the characteristic peak of the stretching vibration of O—H in the carboxyl group of AA (3413 cm -1 ), the characteristic peaks of the stretching vibration of C=O and C—O—C in the ester group of FA13 (1743 cm -1 , 1195 cm -1 ), and the characteristic peaks of the bending vibration of C—F in the fluorocarbon chain (1248 cm -1 , 1080 cm -1 ) are basically consistent with the positions of the corresponding characteristic peaks in the infrared spectrum of PAF-13. At the same time, the characteristic peaks of C=C stretching vibration in AM, AA, FA13 (1629 cm -1 , 1563 cm -1 , 1612 cm -1 ) disappear in the infrared spectrum of PAF-13. Thus, it can be proved that all three monomers participated in the polymerization reaction and the synthesis was successful.

[0041] 2. Performance evaluation of clay stabilizer

[0042] (1) Contact angle measurement

[0043] Press the rectorite or illite powder into a cylindrical specimen with a smooth plane of 18 mm in diameter and 2 mm in thickness. Use an SDC-350 contact angle measuring instrument and adopt the sessile drop method to measure the contact angles of distilled water and the clay stabilizer PAF-13 solution (mass concentration of 1.0%) on the surface of the rectorite or illite specimen respectively.

[0044] Figure 4 are the contact angles of distilled water and the clay stabilizer PAF-13 on rectorite; fromFigure 4 It can be seen that the contact angle between distilled water and the surface of rectorite is 34.07°, showing strong hydrophilicity; after adding the clay stabilizer PAF-13, the contact angle between the solution and the surface of rectorite increases to 55.99°, reducing the hydrophilicity of the rectorite surface.

[0045] Figure 5 is the contact angle of distilled water and the clay stabilizer PAF-13 on illite; from Figure 5 It can be seen that the contact angle between distilled water and the surface of illite is 27.90°, showing strong hydrophilicity; after adding the clay stabilizer PAF-13, the contact angle between the solution and the surface of rectorite increases to 39.41°, reducing the hydrophilicity of the illite surface.

[0046] (2)Anti-swelling performance test

[0047] 1) Linear swelling rate V H

[0048] According to the "Shale physical and chemical properties test method" (SY / T 5613-2000) in the "shale swelling test" method, prepare rectorite and illite cores, and measure the original thickness H (mm) of the cores with a vernier caliper; use the NP-01 type shale swelling instrument, after filling the measuring cylinder with the test fluid, that is, distilled water or clay stabilizer PAF-13 solution (mass concentration of 1.0%), obtain the linear swelling amount R t (mm) at different times. Calculate the linear swelling rate V t (%) at 2 h, 8 h or 16 h respectively according to the following formula: H :

[0049] V H = R t / H × 100%

[0050] Table 1 Linear swelling rate of clay minerals in different fluids

[0051]

[0052] Figure 6 is the swelling curve of distilled water and the clay stabilizer PAF-13 on rectorite. From Figure 6 It can be seen that in distilled water, rectorite shows particularly significant hydration swelling, and the linear swelling rate increases rapidly. After 20 min, the linear swelling rate is as high as 16.79%. After 2 h, the increase rate of the linear swelling rate tends to be flat, V 2h 、V 8hThey are 48.17% and 55.19% respectively. In the PAF-13 solution of clay stabilizer (mass concentration is 1.0%), the hydration swelling phenomenon of rectorite is inhibited, and there is no obvious hydration swelling phenomenon within 20 min, and the growth trend of linear swelling rate significantly tends to be gentle; after 2 h, the linear swelling rate is only 6.19%, compared with that in distilled water, the decrease rate of linear swelling rate is as high as 87.15%. V 8h is 21.89%, only 39.66% of the linear swelling rate in distilled water. After 12 h, the linear swelling rate basically remains unchanged, V 16h is as low as 27.21%, indicating that the clay stabilizer PAF-13 has excellent anti-hydration swelling performance for rectorite.

[0053] Figure 7 are the swelling curves of illite for distilled water and the clay stabilizer PAF-13. From Figure 7 it can be seen that in distilled water, illite also shows particularly significant hydration swelling, and the linear swelling rate increases sharply. After 20 min, the linear swelling rate is as high as 19.00%. After 30 min, the increase rate of linear swelling rate tends to be gentle, V 2h 、V 8h are 22.22% and 22.80% respectively. In the PAF-13 solution of clay stabilizer (mass concentration is 1.0%), the hydration swelling phenomenon of illite is inhibited. After 30 min, the growth trend of linear swelling rate significantly tends to be gentle; after 2 h, the linear swelling rate is only 7.62%, compared with that in distilled water, the decrease rate of linear swelling rate is as high as 65.70%. V 8h is 9.76%, only 57.21% of the linear swelling rate in distilled water. V 16h is only 10.82% either, indicating that the clay stabilizer PAF-13 also has excellent anti-hydration swelling performance for illite.

[0054] 2) Anti-swelling rate B 1

[0055] According to the "Performance Evaluation Method for Clay Stabilizers Used in Oil and Gas Field Fracturing Acidizing and Water Injection" (SY / T 5971-2016), "Measurement of Swelling Volume" (centrifugation method), weigh a certain mass of clay mineral powder (for convenient later reading), accurate to 0.01 g, put it into a 10 mL centrifuge tube, add the PAF-13 solution of clay stabilizer (mass concentration is 1.0%), shake well, place it at room temperature for 2 h, put it into a centrifuge, and centrifuge at a rotation speed of 1500 r / min for 15 min, and read the volume V 1 (mL) of the clay mineral after swelling. Repeat the experiment, and use distilled water and kerosene to replace the clay stabilizer solution respectively to measure the swelling volumes of the clay mineral in distilled water and kerosene, that is, V 2 (mL), V3 (mL). Calculate the anti-swelling rate B according to the following formula 1 (%):

[0056] B 1 = [(V 2 — V 1 ) / (V 2 — V 0 )] × 100%

[0057] The measurement results show that the fluorocarbon clay stabilizer PAF-13 solution with a mass concentration of 1.0% has good anti-swelling ability for rectorite and illite, and the anti-swelling rates are 91.28% and 85.92% respectively.

[0058] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluorocarbon clay stabilizer for oil and gas fields, characterized in that: The following steps are involved: Step 1: Add three monomers of acrylamide, acrylic acid and fluorinated acrylate into a container in sequence, with the weight ratios of the monomers being 300 parts, 195-150 parts and 5-50 parts respectively, and then add 675-1350 parts of solvent N,N-dimethylformamide; stir and dissolve at room temperature, introduce nitrogen to deoxygenate, and heat to 50° C. for standby use; Step 2: Take 1-4 parts of azobisisobutyronitrile as an initiator, add 75-150 parts of N,N-dimethylformamide as a solvent, and dissolve to obtain an initiator solution; Step 3: Under nitrogen atmosphere, slowly drop the initiator solution obtained in step 2 into the monomer mixed solution obtained in step 1, and complete the dropwise addition over 15 min to 30 min. Meanwhile, slowly heat the mixture to 60° C. to 75° C., stir, and perform polymerization reaction for 5 h to 10 h. Step 4: Cool the reaction product obtained in step 3 to room temperature, precipitate with anhydrous ethanol, chop, wash, filter, vacuum dry at 50°C to 70°C for 24 h to 48 h, and grind to obtain a fluorocarbon clay stabilizer; Furthermore, in step 1, the fluorocarbon chain of the fluorinated acrylate monomer m F n Number of carbon atoms m 3~8, the number of fluorine atoms n From 6 to 17.

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