Water shutoff and profile control agent for low-permeability reservoir and preparation method of water shutoff and profile control agent

Abstract

The invention discloses a water shutoff and profile control agent for a low-permeability reservoir and a preparation method of the water shutoff and profile control agent. The water shutoff and profile control agent for the low-permeability reservoir comprises the following raw materials in parts by weight: 20-30 parts of carboxymethyl cellulose; 30 to 40 parts of fumaropimaryl acrylamide; 1-2 parts of a surfactant; 0.5 to 1 part of an initiator; and 5-10 parts of a cross-linking agent. The low-permeability reservoir water shutoff and profile control agent is obtained by crosslinking the carboxymethyl cellulose and the fumaropimaryl acrylamide, and the low-permeability reservoir water shutoff and profile control agent has high shutoff rate at different temperatures because the low-permeability reservoir water shutoff and profile control agent has high temperature resistance due to the addition of the fumaropimaryl acrylamide, so that the shutoff rate of the low-permeability reservoir water shutoff and profile control agent is high; the prepared water shutoff and profile control agent for the low-permeability oil reservoir has high gel strength due to the fact that carboxymethyl cellulose and fumaropimaryl acrylamide form spatial network crosslinking, the gel strength of the water shutoff and profile control agent is greatly improved, on the other hand, fumaropimaryl acrylamide can serve as a cross-linking agent, and the gel forming time is further prolonged.

Description

Technical Field

[0001] This invention belongs to the field of water shut-off and profile control agent technology, specifically relating to a water shut-off and profile control agent for low-permeability oil reservoirs and its preparation method. Background Technology

[0002] As construction time lengthens, low-permeability oilfields generally experience a decline in crude oil production and an increase in overall water cut. With increased water injection, the injected water also forms dominant flow channels, resulting in a smaller water-bearing volume and decreased well production. Injecting water-blocking and profile-modifying agents into injection wells is the main method for sealing permeable layers in oilfields both domestically and internationally. Whether for water plugging or profile modification, chemical plugging agents are currently the most effective. These plugging agents can be categorized into granular plugging agents, foam plugging agents, resin plugging agents, and gel plugging agents.

[0003] Chinese patent application CN116589637A discloses a profile control and water-blocking agent, its preparation method, and its application. The method involves mixing a cellulose compound, acrylamide, and water, then adding a crosslinking agent, followed by an initiator to initiate a polymerization reaction; the mixture is then mixed with a metal salt solution to obtain the profile control and water-blocking agent. Compared to existing profile control and water-blocking agents, this application, while possessing a unique dual-network structure hydrogel material with good stability and maintaining good strength under high temperature and high salt conditions, still primarily uses acrylamide, a petrochemical product, as its raw material, thus lacking environmental friendliness. Therefore, developing environmentally friendly profile control and water-blocking agents is crucial. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of poor sealing performance in the prior art, thereby providing a water shut-off and profile control agent for low-permeability reservoirs and its preparation method, using natural products as the main raw materials to obtain a water shut-off and profile control agent for low-permeability reservoirs with good temperature resistance.

[0005] To achieve the above objectives, the present invention provides a water shut-off and profile control agent for low-permeability reservoirs, comprising the following raw materials: 20-30 parts of carboxymethyl cellulose; 30-40 parts of fumarate-based acrylamide; 1-2 parts surfactant; Initiator 0.5~1 part; 5-10 parts of crosslinking agent.

[0006] Preferably, the surfactant is sodium dodecyl sulfate, and the initiator is at least one of ammonium persulfate, sodium bisulfite, potassium persulfate, or azobisisobutyrazoline hydrochloride.

[0007] Preferably, the crosslinking agent is an organochromium crosslinking agent.

[0008] This invention also provides a method for preparing a water shut-off and profile control agent for low-permeability reservoirs, comprising the following steps: (1) Fumaropyric acid is added to thionyl chloride to prepare fumaropiloyl chloride. Ammonia gas is introduced and reacted at 0~25℃ for 4~8h to obtain fumaropiloyl amide. An acid-binding agent is added and acryloyl chloride is added at 20~40℃ for 1~3h to obtain fumaropiloyl acrylamide. (2) Add carboxymethyl cellulose to water and stir for 30-60 min. Add surfactant and continue stirring for 30-60 min. Then add fumarate-salicylic acid, initiator and crosslinking agent and stir for 1-3 h to obtain low-permeability reservoir water shut-off and profile control agent.

[0009] Preferably, the molar ratio of fumaric acid to thionyl chloride is 1:3 to 1:8, the reaction temperature of fumaric acid and thionyl chloride is 0 to 30°C, and the reaction time is 1 to 3 hours.

[0010] Preferably, the acid-binding agent is triethylamine.

[0011] Preferably, the molar ratio of fumarate to acryloyl chloride is 1:3 to 1:6.

[0012] Preferably, the reaction temperature in step (2) is 30~50℃.

[0013] By adopting the above technical solution, the present invention has the following beneficial effects: 1. The water shut-off and profile control agent for low-permeability reservoirs provided by this invention uses natural products as the main raw materials. Through modification of natural products, the temperature resistance, plugging rate and gel strength of the water shut-off and profile control agent for low-permeability reservoirs are improved. 2. The preparation method of the low-permeability reservoir water shut-off and profile control agent provided by the present invention obtains the low-permeability reservoir water shut-off and profile control agent by crosslinking carboxymethyl cellulose and fumarate-pinelacrylamide. It has a high sealing rate at different temperatures. This is because the addition of fumarate-pinelacrylamide makes the low-permeability reservoir water shut-off and profile control agent have high temperature resistance, resulting in a high sealing rate. The prepared low-permeability reservoir water shut-off and profile control agent has strong gel strength. This is because carboxymethyl cellulose and fumarate-pinelacrylamide form a spatial network crosslinking, which greatly improves its gel strength. On the other hand, fumarate-pinelacrylamide itself can act as a crosslinking agent, further improving the gelation time.

[0014] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below. Detailed Implementation

[0015] The invention can be further understood in conjunction with the following detailed description of preferred embodiments and included examples. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. If any definition of a specific term disclosed in the prior art differs from any definition provided herein, the definition provided herein shall prevail.

[0016] It should be noted that the implementation conditions used in the examples can be further adjusted according to the specific experimental environment, and the implementation conditions not specified are usually those in conventional experiments. Unless otherwise specified, the preparation methods mentioned in this invention are all conventional methods; unless otherwise specified, all chemical reagents and chemicals mentioned in the following examples are commercially available.

[0017] The present invention will be further described below with reference to embodiments. It should be further noted that the following embodiments involve the following test methods: (1) Blocking rate test method: A sand-filling pipe with a length of 30cm and an inner diameter of 2.54cm was prepared using 80-mesh quartz sand. The sand-filling pipe was evacuated and saturated with clean water for 3 hours. Then, the initial permeability of the water phase in the sand-filling pipe was measured with clean water. 1.0PV of water shut-off and profile control agent for low-permeability reservoirs was injected, and the system was heated to different temperatures and allowed to solidify for 24 hours. The permeability of the sand-filling pipe after sealing was measured by reverse displacement with clean water.

[0018] The formula for calculating the blocking rate is as follows: E = (K0 - K1) / K0 × 100%. In the formula: K0 is the initial permeability, %; K1 is the permeability after plugging, %.

[0019] (2) Method for testing gel strength: 100 ml of water shut-off and profile control agent for low-permeability reservoirs was added to a 100 ml vial. After deoxygenation and nitrogen purging, the vial was sealed and placed in a 120°C oven for heating to form a gel. The gelation process was monitored every hour. When the water shut-off agent rapidly thickened, the gel strength was measured every 20 minutes using a HAKKERS 150 high-temperature rheometer at a shear rate of 1.5 s⁻¹. The time when the gel strength reached its maximum was the gelation time, and the strength at which the gel strength stabilized was the gel strength.

[0020] Example 1 A method for preparing a water shut-off and profile control agent for low-permeability oil reservoirs includes the following steps: (1) 41.9g fumaric acid was dissolved in 250mL of dichloromethane, 59.8g of thionyl chloride was added, and the reaction was carried out at 0℃ for 2h to prepare 42.6g fumaric acid acyl chloride. Then ammonia gas was introduced until the outlet pH test paper was alkaline. After reacting at 15℃ for 6h, fumaric acid acyl amide was obtained. 15.2g of triethylamine was added, and 36.1g of acyl chloride was added at 30℃ for 2h to obtain 48.0g fumaric acid acyl amide. (2) Add 30g of carboxymethyl cellulose to 1000mL of water and stir for 40min. Add 1g of sodium dodecyl sulfate and continue stirring for 40min. Then add 35g of fumarate-salicylic acid, 1g of ammonium persulfate and 5g of organic chromium crosslinking agent. Stir and react at 30℃ for 2h to obtain a low-permeability reservoir water shut-off and profile control agent.

[0021] The sealing rates of the obtained low-permeability reservoir water shut-off and profile control agents at different temperatures are shown in Table 1, and the gel strength of the obtained low-permeability reservoir water shut-off and profile control agents is shown in Table 2.

[0022] Example 2 A method for preparing a water shut-off and profile control agent for low-permeability oil reservoirs includes the following steps: (1) Dissolve 34.9g fumaric acid in 250mL dichloromethane, add 50.6g thionyl chloride, and react at 5℃ for 2h to prepare 33.6g fumaric acid acyl chloride. Then, pass ammonia gas until the outlet pH test paper is alkaline. After reacting at 25℃ for 8h, fumaric acid acyl amide is obtained. Add 13.0g triethylamine, and at 40℃, add 32.0g acyl chloride and react for 3h to obtain 34.6g fumaric acid acyl amide. (2) Add 25g of carboxymethyl cellulose to 1000mL of water and stir for 60min. Add 1g of sodium dodecyl sulfate and continue stirring for 60min. Then add 40g of fumarate-salicylic acid, 1g of ammonium persulfate and 10g of organic chromium crosslinking agent. Stir and react at 50℃ for 3h to obtain a low-permeability reservoir water shut-off and profile control agent.

[0023] The sealing rates of the obtained low-permeability reservoir water shut-off and profile control agents at different temperatures are shown in Table 1, and the gel strength of the obtained low-permeability reservoir water shut-off and profile control agents is shown in Table 2.

[0024] Example 3 A method for preparing a water shut-off and profile control agent for low-permeability oil reservoirs includes the following steps: (1) Dissolve 35.6g fumaric acid in 250mL dichloromethane, add 52.5g thionyl chloride, and react at 0℃ for 2h to prepare 35.0g fumaric acid acyl chloride. Then, pass ammonia gas until the outlet pH test paper is alkaline. After reacting at 0℃ for 6h, fumaric acid acylamide is obtained. Add 12.6g triethylamine, and at 20℃, add 33.0g acyl chloride and react for 1h to obtain 30.6g fumaric acid acylamide. (2) Add 20g of carboxymethyl cellulose to 1000mL of water and stir for 30min. Add 1g of sodium dodecyl sulfate and continue stirring for 30min. Then add 30g of fumarate-salicylic acid, 0.5g of ammonium persulfate and 7g of organic chromium crosslinking agent. Stir and react at 40℃ for 1h to obtain a low-permeability reservoir water shut-off and profile control agent.

[0025] The sealing rates of the obtained low-permeability reservoir water shut-off and profile control agents at different temperatures are shown in Table 1, and the gel strength of the obtained low-permeability reservoir water shut-off and profile control agents is shown in Table 2.

[0026] Comparative Example 1 Add 30g of carboxymethyl cellulose to 1000mL of water and stir for 40min. Add 1g of sodium dodecyl sulfate and continue stirring for 40min. Then add 1g of ammonium persulfate and 5g of organic chromium crosslinking agent. Stir and react at 30℃ for 2h to obtain a low-permeability reservoir water shut-off and profile control agent.

[0027] The sealing rates of the obtained low-permeability reservoir water shut-off and profile control agents at different temperatures are shown in Table 1, and the gel strength of the obtained low-permeability reservoir water shut-off and profile control agents is shown in Table 2.

[0028] Comparative Example 2 Add 30g of carboxymethyl cellulose to 1000mL of water and stir for 40min. Add 1g of sodium dodecyl sulfate and continue stirring for 40min. Then add 1g of ammonium persulfate and 5g of organic chromium crosslinking agent. Stir and react at 30℃ for 2h to obtain a low-permeability reservoir water shut-off and profile control agent.

[0029] The sealing rates of the obtained low-permeability reservoir water shut-off and profile control agents at different temperatures are shown in Table 1, and the gel strength of the obtained low-permeability reservoir water shut-off and profile control agents is shown in Table 2.

[0030] Table 1. Plugging rates of different embodiments and comparative examples at different temperatures.

[0031] As can be seen from Table 1, the low-permeability reservoir water shut-off and profile control agents prepared in Examples 1 to 3 of this application have high plugging rates at different temperatures. This is because the addition of fumarate-salicylic acid gives the low-permeability reservoir water shut-off and profile control agents high temperature resistance, resulting in a high plugging rate.

[0032] Table 2. Gel strength and gelation time of different embodiments and comparative examples

[0033] As can be seen from Table 2, the low-permeability reservoir water shut-off and profile control agents prepared in Examples 1 to 3 of this application have strong gel strength. This is because the low-permeability reservoir water shut-off and profile control agents prepared in Examples 1 to 3 utilize carboxymethyl cellulose and fumarate-pinelacrylamide dual bio-based raw materials to form a spatial network crosslinking, which significantly improves their gel strength. On the other hand, the fumarate-pinelacrylamide itself can act as a crosslinking agent, further improving the gelation time.

[0034] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A water shut-off and profile control agent for low-permeability oil reservoirs, characterized in that, Includes the following components by weight: 20-30 parts of carboxymethyl cellulose; 30-40 parts of fumarate-based acrylamide; 1-2 parts surfactant; Initiator 0.5~1 part; 5-10 parts of crosslinking agent.

2. The low-permeability reservoir water shut-off and profile control agent as described in claim 1, characterized in that, The surfactant is sodium dodecyl sulfate.

3. The low-permeability reservoir water shut-off and profile control agent as described in claim 1, characterized in that: The initiator is at least one of ammonium persulfate, sodium bisulfite, potassium persulfate, or azobisisobutyrazoline hydrochloride. The crosslinking agent is an organochromium crosslinking agent.

4. The low-permeability reservoir water shut-off and profile control agent as described in claim 1, characterized in that, The preparation method of the fumaropine acrylamide is as follows: Fumaropyric acid was added to thionyl chloride to prepare fumaropiloyl chloride. Ammonia gas was introduced and the reaction was carried out at 0-25°C for 4-8 hours to obtain fumaropiloylamide. An acid-binding agent was added and acryloyl chloride was added at 20-40°C for 1-3 hours to obtain fumaropiloylacrylamide.

5. The low-permeability reservoir water shut-off and profile control agent as described in claim 4, characterized in that: The molar ratio of fumaric acid to thionyl chloride is 1:3 to 1:8, the reaction temperature of fumaric acid and thionyl chloride is 0 to 30°C, and the reaction time is 1 to 3 hours.

6. The low-permeability reservoir water shut-off and profile control agent as described in claim 4, characterized in that: The acid-binding agent is triethylamine.

7. The low-permeability reservoir water shut-off and profile control agent as described in claim 4, characterized in that: The molar ratio of fumarate to acryloyl chloride is 1:3 to 1:

6.

8. A method for preparing a low-permeability reservoir water shut-off and profile control agent according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: S1. Preparation of fumaropine-based acrylamide Fumaropioid chloride was prepared by adding fumaric acid to thionyl chloride, wherein the molar ratio of fumaric acid to thionyl chloride was 1:3 to 1:

8. Ammonia gas was introduced into fumarate acyl chloride, and the reaction was carried out at 0~25℃ for 4~8h to obtain fumarate acylamide. An acid-binding agent is added to fumarate-pinelamide, and acryloyl chloride is added at 20-40°C and reacted for 1-3 hours to obtain fumarate-pinelacrylamide; the molar ratio of fumarate-pinelamide to acryloyl chloride is 1:3-1:

6. S2. Preparation of water shut-off and profile control agents for low-permeability reservoirs Add 20-30 parts by weight of carboxymethyl cellulose to water and stir for 30-60 minutes. Add 1-2 parts by weight of surfactant and continue stirring for 30-60 minutes. Then add 30-40 parts by weight of fumarate-salicylic acid amide prepared by S1, 0.5-1 parts by weight of initiator, and 5-10 parts by weight of crosslinking agent. Stir and react for 1-3 hours to obtain a low-permeability reservoir water shut-off and profile control agent.

9. The preparation method of the low-permeability reservoir water shut-off and profile control agent as described in claim 8, characterized in that, The acid-binding agent is triethylamine, and the molar ratio of the acid-binding agent to acryloyl chloride is (0.3~1):

1.

10. The preparation method of the low-permeability reservoir water shut-off and profile control agent as described in claim 8, characterized in that: In step S2, the reaction temperature is 30~50℃.

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