CN113265026B - Water-swelling rubber flexible temporary plugging particle and preparation method thereof - Google Patents

Abstract

The invention provides water-swelling rubber flexible temporary plugging particles, which are prepared by the following method: dissolving acrylamide, bentonite and functional monomers in water; adding the solution into natural latex, and curing at 45-50 ℃ for 2 h; adding an initiator and a cross-linking agent, and sealing and reacting for 4-5h at 45-50 ℃ to form gel; drying and crushing a product after reaction to obtain the catalyst; the adding amount of each substance is as follows by mass percent: 10-15% acrylamide; 2.5-5% of bentonite; 9.6-12.6% of natural latex by mass of dry glue; 10% of acrylamide and natural latex dry glue mass; 0.28-0.33% of cross-linking agent based on the sum of the mass of acrylamide and natural latex dry glue; 0.22-0.39% of the sum of the dry mass of acrylamide and natural latex; total solid content 28-32%, and water in balance. The water-swelling rubber flexible temporary plugging particles have controllable particle size and can be adjusted according to the requirement of the entering depth; the residue rate after degradation is lower than 3 percent, and the residue is easy to flow back; and has certain temperature resistance and salt tolerance.

Description

A kind of water-swellable rubber flexible temporary plugging particles and preparation method thereof

technical field

The invention belongs to the technical field of oilfield chemistry, and in particular relates to a water-swellable rubber flexible temporary plugging particle and a method for preparing the temporary plugging particle.

Background technique

With the development of oil and gas fields in the middle and late stages, oil and gas in high-permeability reservoirs are preferentially exploited due to the heterogeneity of the formation. How to improve the oil recovery factor of low-permeability reservoirs has always been a research hotspot. Stimulation measures such as fracturing and acidification are often used, and fracturing fluid and acid fluid will preferentially enter the high-permeability layer to improve the physical properties of the high-permeability layer. The low-permeability layer has not been effectively improved. also increased substantially. Therefore, the key to solving the problem is to control the diversion and diversion of fracturing fluid and acid fluid, and enter the low-permeability reservoir for treatment. In addition, for tight reservoirs and thicker reservoirs, artificial temporary plugging is often required to force the fracturing fluid to divert the fracturing fluid to the reservoir to create a complex fracture network to expand the oil drainage area of the oil well and improve the recovery factor. Compared with mechanical temporary plugging, chemical temporary plugging has lower risk in complex well conditions, higher construction success rate and higher reservoir stimulation effectiveness, so it has a better application effect in working fluid diversion technology.

Chemical temporary plugging technology is widely used in temporary plugging acidification, refracturing, and temporary plugging acid fracturing. Temporary plugging and acidification can achieve the purpose of uniform acidification and avoid the rapid rise of water content in the well. After acidification, the temporary plugging agent can degrade rapidly and will not pollute the formation; in repeated fracturing and temporary plugging acid fracturing, the temporary plugging agent can hold back the The static pressure inside the fracture opens new fractures. After the fracturing is completed, the temporary plugging agent dissolves in the formation water, and the plugged fractures are unobstructed again. Chemical temporary plugging agents can be divided into acid-soluble, water-soluble, and oil-soluble according to their dissolution characteristics; according to their forms, they can be divided into fiber temporary plugging agents, particle temporary plugging agents, polymer cross-linked temporary plugging agents, water-swellable temporary plugging agents, and foams. Temporary blocking agent, etc. Fiber temporary plugging agent has low strength, low density and is easy to scatter; polymer cross-linking temporary plugging agent has more residue after degradation, and the cross-linking process is easily affected by pH value and temperature; foam type plugging agent has poor high temperature stability and high cost; water absorption The expansion-type temporary plugging agent has elasticity, and the plugging strength is not high. The particle-type plugging agent has low cost and good temperature and pressure resistance.

The water-swellable flexible temporary plugging particles are flexible and variable, have a controllable particle size, can enter the deep formation, are resistant to temperature and salt, have low cost, and have good development prospects.

SUMMARY OF THE INVENTION

In order to solve the aforementioned problems, the present invention proposes a water-swellable rubber flexible temporary plugging particle, the particle size of which is controllable, can be adjusted according to the depth of entry, and can be degraded at the same time. contamination of the reservoir.

The technical scheme of the present invention is as follows: a method for preparing water-swellable rubber flexible temporary plugging particles, comprising the following steps:

1) Dissolving or dispersing acrylamide, bentonite and functional monomers in water;

2) Add the solution obtained in step 1) into the natural latex, stir evenly, and ripen for 2 hours at 45-50°C;

3) Add initiator and cross-linking agent, stir evenly, then seal and react at 45-50℃ for 4-5h to form glue;

4) oven dry and pulverize the reacted product;

In the above steps, in terms of mass percentage, the amount of each substance added is as follows: 10-15% of acrylamide; 2.5-5% of bentonite; in terms of dry rubber mass, 9.6-12.6% of natural latex; acrylamide and natural latex 10% of the dry rubber mass and functional monomer; 0.28-0.33% of the dry rubber mass of acrylamide and natural latex cross-linking agent; 0.22-0.39% of the acrylamide and natural latex dry rubber mass of the initiator; total The solid content is 28-32%, and the balance is water.

One embodiment of the present invention is that the functional monomer is one or any two of diacetone acrylamide, sodium p-styrene sulfonate hydrate, methyl methacrylate, and octadecyl methacrylate. kind of mix.

One embodiment of the present invention is that the crosslinking agent is one or both of N'N-methylenebisacrylamide and polyethylene glycol.

One embodiment of the present invention is that the initiator is composed of initiator one and initiator two with a mass ratio of 1:1, the initiator one is one of potassium persulfate or ammonium persulfate, the The second initiator is one of sodium bisulfite or sodium thiosulfate.

An embodiment of the present invention is that, in the step 3), the reaction is carried out to form a gel under airtight conditions.

One embodiment of the present invention is that the specific operation of the step 4) is as follows: the reaction product is cut into small pieces, dried at 90° C., and pulverized after drying.

Another object of the present invention is to provide a water-swellable rubber flexible temporary plugging particle, which is prepared by the method described in any of the above.

In the present invention, in order to make the prepared product as homogeneous as possible and avoid moisture loss of the product located at the top due to frequent air flow, it is necessary to make it react in a sealed state.

In the present invention, the rubber molecular chain and the monomer chain are intertwined with each other, the hydrophilic group first adsorbs the bound water, and the cross-linked network binds the free water, thereby swelling and blocking. After the temporary plugging agent swelled by water absorption is released from the water environment, the free water bound in the cross-linked network evaporates first, while the bound water adsorbed by the water-absorbing group is not easily released and has a certain water retention. The addition of a small amount of bentonite brings a large amount of hydroxyl (-OH), carboxyl (-COOH) and sodium carboxylate (-COONa) groups, and there are many active points. When there is water, the compensation ions between the crystal layers are easy to Exchanged by other cations in the solution, among which variable charge and exchangeable cations can enhance the salt tolerance of the temporarily plugged particles.

The water absorption process of the water-swellable temporary plugging agent is divided into two stages: in the first stage, in the initial stage of water absorption, water molecules enter the interior through surface adsorption, capillary action and diffusion, and the hydrophilic groups pass through coordination bonds or hydrogen bonds. The bound water is connected with the bound water through hydrogen bonds or orientation force, the cross-linked network expands rapidly, and the rubber expands and deforms; the second stage of water seepage or water absorption is caused by the adjustment of the network conformation, and the expanded polymer network In the cross-linked network and rubber network structure including the water-absorbing component, the adjustment of conformation cannot keep up with the expansion rate, so the rate is slower. In the first stage, the rubber can still maintain certain mechanical properties. In the second stage, due to the continuous and massive infiltration of water molecules, the network is gradually destroyed, resulting in a decline in mechanical properties until it begins to gradually degrade.

The water-absorbing swellable rubber flexible temporary plugging particles of the present invention have degradation performance. After the inventor's research, this is because the method of the present invention does not remove oxygen during the preparation process. During the synthesis process, the rubber contacts with oxygen and thermal oxidation occurs. During the aging process of rubber, the heat in the formation promotes the oxidation of the rubber particles, further aggravates the decline of the mechanical properties of the rubber particles, and finally promotes the degradation of the flexible temporary plugging particles of the water-swellable rubber.

Beneficial effects of the present invention:

The low-ammonia type concentrated natural rubber latex used in the present invention has a small tendency to crust on the surface, and the loss of glue material is correspondingly small. The synthesized water-swellable rubber flexible temporary plugging particles have a controllable particle size and can be adjusted according to the depth of entry; the mode of "migration, plugging, elastic deformation, re-migration, and re-plugging" can be realized in the formation pores; At the same time, it can be degraded naturally under the condition of 70-150 ℃, the residue rate after degradation is less than 3%, and it is easy to flow back; and it has a certain temperature resistance and salt resistance, which is suitable for water plugging and profile control or fracture network in heterogeneous oil reservoirs Temporary plugging process for fracturing.

Description of drawings

Figure 1 shows the water absorption ratios of the water-swellable flexible temporary plugging particles of the present invention at 70°C, 90°C, 125°C and 150°C, respectively.

Figure 2 shows the expansion times of the water-swelling flexible temporary plugging particles of the present invention in 100,000, 150,000, 200,000 and 250,000 salinity water at 125°C.

Fig. 3 is the comparative effect before and after centrifugation of the water-swellable flexible temporary plugging particles of the present invention after being degraded.

Detailed ways

In order to make the technical solutions and technical advantages of the present invention clearer, the technical solutions in the implementation process of the present invention will be clearly and completely described below with reference to the embodiments and the accompanying drawings.

Materials and medicines used in the embodiment: natural latex (Maoming Yuanmao Petrochemical Co., Ltd., low ammonia latex, dry rubber content is 60.12%);

Acrylamide, diacetone acrylamide, sodium p-styrene sulfonate hydrate, potassium persulfate, ammonium persulfate, sodium bisulfite, sodium chloride (Chengdu Kelong Chemical Co., Ltd.);

Bentonite (Lingshou County Shuolong Mineral Products Processing Plant).

Example 1

In the present embodiment, the following steps are used to prepare water-swellable rubber flexible temporary plugging particles:

(1) Dissolve 10g acrylamide, 4g bentonite and 1.8g diacetone acrylamide successively in 50g deionized water by ultrasonic;

(2) adding the aqueous solution obtained in step (1) into 16.63 g of concentrated natural latex, stirring evenly, sealing, and curing in a constant temperature water bath at 45°C for 2 hours;

(3) Add 0.035g potassium persulfate, 0.035g sodium bisulfite, 0.06g N'N-methylenebisacrylamide, stir evenly, seal and react at 45°C for 4.5h to form a gel;

(4) Use scissors to cut into pieces of about 1cm×1cm×1cm, put them in a 90°C oven for drying, and pulverize the dried pieces with a pulverizer.

Example 2

In the present embodiment, the following steps are used to prepare water-swellable rubber flexible temporary plugging particles:

(1) Dissolve 10g of acrylamide, 4g of bentonite and 1.8g of sodium p-styrene sulfonate hydrate successively in 50g of deionized water using ultrasound;

(2) adding the aqueous solution obtained in step (1) into 16.63 g of concentrated natural latex, stirring evenly, sealing, and curing in a constant temperature water bath at 45°C for 2 hours;

(3) Add 0.035g potassium persulfate, 0.035g sodium bisulfite, 0.06g N'N-methylenebisacrylamide, stir evenly, seal and react at 45°C for 4.5h to form a gel;

(4) Use scissors to cut into pieces of about 1cm×1cm×1cm, put them in a 90°C oven for drying, and pulverize the dried pieces with a pulverizer.

Example 3

In the present embodiment, the following steps are used to prepare water-swellable rubber flexible temporary plugging particles:

(1) Dissolve 10g acrylamide, 4g bentonite and 1.8g diacetone acrylamide successively in 50g deionized water by ultrasonic;

(2) Add to 16.63g of concentrated natural latex, stir evenly, seal, and place in a constant temperature water bath at 45°C for 2 hours;

(3) Add 0.035g ammonium persulfate, 0.035g sodium thiosulfate, 0.06g N'N-methylenebisacrylamide, stir evenly, seal and react at 45°C for 4.5h to form a gel;

(4) Use scissors to cut into pieces of about 1cm×1cm×1cm, put them in a 90°C oven for drying, and pulverize the dried pieces with a pulverizer.

The following methods are used to further illustrate the effect of the water-absorbing swellable rubber flexible temporary plugging particles prepared in the above examples.

NaCl water with salinity of 10×10 ⁴ mg/L, 15×10 ⁴ mg/L, 20×10 ⁴ mg/L and 25×10 ⁴ mg/L was prepared for use.

1. Water swellability of water swellable rubber flexible temporary plugging particles

Put the dried flexible granules in Example 1 into an aging tank, add an appropriate amount of tap water, and heat them for 48 hours at 70°C, 90°C, 125°C, and 150°C, respectively, and take them out at regular intervals to remove excess surface. Moisture, measure its water-swelling ratio.

After 48 hours, the expansion ratios at 70°C, 90°C, 125°C and 150°C were 15.1 times, 18.9 times, 30.46 times, and 37.26 times, respectively. The higher the temperature, the faster the expansion and the sooner the water absorption equilibrium was reached. As can be seen in Figure 1, the initial 9h expansion rate is fast, and the expansion rate gradually slows down after 9h. In the first stage of the water absorption process of temporarily plugged particles, water molecules enter the interior through surface adsorption, capillary action and diffusion, hydrophilic groups bind water molecules through coordination bonds or hydrogen bonds, and bound water combines with hydrogen bonds or orientation forces. Water connection, the cross-linked network expands rapidly, and the rubber expands and deforms; the adjustment of the polymer network conformation after expansion in the second stage cannot keep up with the expansion rate, so the rate is slower than that in the first stage.

At 125℃, the dry flexible particles were put into water with salinity of 10×10 ⁴ mg/L, 15×10 ⁴ mg/L, 20×10 ⁴ mg/L, and 25×10 ⁴ mg/L respectively. , hot roll for 48h, take it out at regular intervals, absorb the excess water on the surface, and measure the expansion ratio of its water absorption.

After 48 hours, the expansion ratios of water-swellable rubber in water with salinity of 10×10 ⁴ mg/L, 15×10 ⁴ mg/L, 20×10 ⁴ mg/L and 25×10 ⁴ mg/L were 12.45 times and 12.45 times respectively. 12 times, 11.17 times, and 10.75 times, as shown in Figure 2, the higher the salinity, the slower the expansion rate, and the expansion rate can still reach more than 10 times at high salinity.

2. Flexibility of water-swellable rubber flexible temporary plugging particles

Use scissors to cut the water-swelling rubber after the reaction into gel in Example 1 into a 1cm×0.2cm×0.2cm block, and it is measured that it can be stretched by 4.5 times at a maximum, reaching Grade E; the dried block absorbs water again. After 24 hours of expansion, it can be stretched up to 3.24 times, and it can still reach grade D or above. It can be seen that the synthesized water-swelling temporary plugging particles have good flexibility, and can be deformed according to the size of pores in the formation to achieve "migration, plugging". , elastic deformation, re-migration, and re-plugging" mode, so as to achieve the purpose of deep formation.

3. Degradation performance of water-swellable rubber flexible temporary plugging particles

Use a pulverizer to pulverize the dried glue blocks in Example 1 into particles of 20-60 meshes, put them in tap water at 125°C to absorb water and swell, and the particles will be completely degraded after 60 hours; take the aforementioned dried glue blocks and pulverize them into 20-60 meshes The particles were swelled by water absorption in water with a salinity of 15×10 ⁴ mg/L at 125℃, and completely degraded in 110h. Centrifuge the degraded liquid at 3500 r/min for 30 minutes (centrifugation results are shown in Figure 3), weigh the bottom residue, the residue rate is less than 3%, and the degradation rate is over 97%. It can be seen that the temporary plugging agent can achieve temporary plugging in the formation. It can be basically completely degraded, does not pollute the formation, and is easy to flow back.

In fact, the water-swellable rubber flexible temporary plugging particles prepared in the above examples can be degraded at 70-150 ℃, and follow the following rules: the lower the temperature, the slower the degradation speed; the higher the salinity, the slower the degradation speed.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Technical personnel, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content disclosed above, but any content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (6)

1. a method for preparing water-swellable rubber flexible temporary blocking particles is characterized in that, the steps of the method are as follows: 1) Dissolve or disperse acrylamide, bentonite and functional monomers in water; 2) Add the solution obtained in step 1) into the natural rubber latex, stir evenly, and age at 45-50°C for 2 hours; 3) Add initiator and cross-linking agent, stir evenly, react at 45-50℃ for 4-5h to form gel; 4) drying and pulverizing the reacted product; In the above steps, in terms of mass percentage, the addition amount of each substance is as follows: 10-15% of acrylamide; 2.5-5% of bentonite; in terms of dry rubber mass, 9.6-12.6% of natural latex; acrylamide and natural latex 10% of functional monomers of dry rubber mass; 0.28-0.33% of acrylamide and natural latex dry rubber mass of cross-linking agent; 0.22-0.39% of acrylamide and natural latex dry rubber mass of initiator; total The solid content is 28-32%, and the balance is water; The functional monomer is one of diacetone acrylamide, sodium p-styrene sulfonate hydrate, methyl methacrylate, and octadecyl methacrylate, or a mixture of any two. 2. method according to claim 1, is characterized in that, described crosslinking agent is one or both in N'N-methylenebisacrylamide, polyethylene glycol. 3. method according to claim 1, is characterized in that, described initiator is made up of initiator one and initiator two that mass ratio is 1:1, and described initiator one is in potassium persulfate or ammonium persulfate. A kind of, described initiator two is a kind of in sodium bisulfite or sodium thiosulfate. 4 . The method according to claim 1 , wherein in the step 3), the entire reaction is carried out under airtight conditions. 5 . 5. The method according to claim 1, wherein the specific operation of the step 4) is as follows: the reaction product is cut into small pieces, dried at 90°C, and pulverized after drying. have to. 6 . A flexible temporary plugging particle of water-absorbing swellable rubber, characterized in that, it is prepared by the method of any one of claims 1-5.

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