Underground in-situ crosslinked lignin plugging agent and preparation method and application thereof

Abstract

The invention discloses an underground in-situ crosslinked lignin plugging agent as well as a preparation method and application thereof. The invention discloses an underground in-situ crosslinked lignin blocking agent and a preparation method and application thereof. The blocking agent comprises lignin, a catalyst, a thickening agent, an assistant crosslinker, a cosolvent and the like, and the underground in-situ crosslinked lignin blocking agent is prepared by uniformly mixing the raw materials including the lignin, the catalyst, the thickening agent, the assistant crosslinker, the cosolvent and water. The plugging agent disclosed by the invention can be used for controllably gelling (1.5-120 hours) within a relatively wide temperature range (more than 120 DEG C), does not break gel at a high temperature of 300 DEG C for 60 days, has a dehydration rate of less than 5.1% and a plugging rate of higher than 98.8%, can effectively plug a steam channeling channel for a long time, and realizes efficient development of a heavy oil reservoir.

Description

Technical Field

[0001] The present invention relates to the technical field of plugging agents for crude oil production. Further, it relates to an in-situ crosslinked lignin plugging agent for underground use, its preparation method and application. Background Art

[0002] At present, thermal recovery technologies such as steam huff and puff and steam flooding are the main methods used in the development of heavy oil. In the later stage of development, due to limitations such as the underdevelopment of formation barriers, permeability differences between layers, and development conditions, problems such as low injection-production ratio, low formation pressure, serious steam channeling, sand production, and edge water flooding have emerged, making it difficult to maintain stable production.

[0003] There are various methods for plugging steam channels and suppressing edge water invasion in heavy oil, but they generally have some defects. For example, the plugging effect of mechanical plugging in the vertical direction is not good; using cement or solid mud to plug high-permeability underground layers, the biggest problem is that the oil-bearing production layers are also plugged. Using chemical plugging agents for plugging is also an effective method to control steam channeling. The plugging agents mainly include water-in-oil emulsions, steam foams, inorganic particles, high-temperature gels, etc. Among them, the on-site construction process of injecting foam is complex, and inorganic particles often remain in the near-wellbore area. High-temperature gels still have problems such as short plugging validity period and easy loss of plugging effect at high temperature and high salinity. In view of the increasingly serious problems of steam channeling and edge water invasion, there is an urgent need to develop a chemical plugging system with good injectability, high temperature resistance, high strength, and suitable for deep plugging to achieve the expansion of the steam sweep area in the plane and the improvement of the utilization degree.

[0004] Lignin has the second largest reserve in nature after cellulose and is the second largest natural organic matter. Industrial lignin is rich in sources and low in price, and can be used as a raw material for producing oilfield chemicals. Using lignin as a raw material for preparing plugging agents can turn waste into treasure and the cost of preparing plugging agents is low. With the rising price of petrochemical raw materials and the increasing environmental protection requirements, green chemicals using low-cost natural renewable resources such as lignin have become an international hot research and development direction.

[0005] However, the main connection methods between the structural main bodies of natural lignin are ether bonds and carbon-carbon bonds. These two types of bonds have small molecular polarity, high bond energy and are difficult to react. Moreover, they have a high methoxy content, a low hydroxyl content, and large steric hindrance on the benzene ring, resulting in significantly insufficient reactivity. For commercially available industrial by-product lignin, due to the condensation reaction after chemical treatment, its reaction sites are even fewer.

[0006] In the process of oilfield application, on the one hand, the strength of lignin-based plugging materials is generally low and gel formation is uncontrollable; on the other hand, it leads to a generally high use concentration of lignin, high cost, and affects its popularization and application. Summary of the Invention

[0007] To solve the problems in the prior art, the present invention provides an in-situ crosslinked lignin plugging agent for underground use, its preparation method and application. The plugging agent in the present invention includes lignin, a catalyst, a thickening agent, a co-crosslinking agent, a co-solvent, etc. This plugging agent can be controllably gelled (1.5 - 120 h) within a relatively wide temperature range (>120 °C), does not break gel within 60 days at a high temperature of 300 °C, has a dehydration rate <5.1%, a plugging rate higher than 98.8%, and can effectively plug the steam channel for a long time, realizing the efficient development of heavy oil reservoirs.

[0008] One of the purposes of the present invention is to provide an in-situ crosslinked lignin plugging agent for underground use, and the plugging agent includes lignin, a catalyst, a thickening agent, a co-crosslinking agent, a co-solvent and water;

[0009] Based on the total weight of lignin, a catalyst, a thickening agent, a co-crosslinking agent, a co-solvent and water being 100%, it includes:

[0010] the content of the lignin is 1 - 7.5 wt%;

[0011] the content of the catalyst is 0.1 - 0.75 wt%;

[0012] the content of the thickening agent is 0.02 - 0.2 wt%;

[0013] the content of the co-crosslinking agent is 0.3 - 2 wt%;

[0014] the content of the co-solvent is 0.5 - 5 wt%;

[0015] the balance is water.

[0016] In the in-situ crosslinked lignin plugging agent for underground use of the present invention, preferably,

[0017] the content of the lignin is 2 - 5 wt%; and / or,

[0018] the content of the catalyst is 0.2 - 0.5 wt%; and / or,

[0019] the content of the thickening agent is 0.05 - 0.15 wt%; and / or,

[0020] the content of the co-crosslinking agent is 0.5 - 1.8 wt%; and / or,

[0021] the content of the co-solvent is 1 - 3 wt%.

[0022] In the present invention, those skilled in the art can also add other commonly used substances in the art according to the common knowledge in the art, and the amount of this substance added is according to the ordinary amount in the art.

[0023] In the in-situ crosslinked lignin plugging agent for underground use of the present invention, preferably,

[0024] The lignin is selected from at least one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the effective content of lignin in the lignin is 80-99.9 wt%.

[0025] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0026] The catalyst is selected from at least one of solid acid catalysts;

[0027] Preferably, the catalyst is selected from at least one of MOR zeolite, USY zeolite and ZSM-5 zeolite;

[0028] Further preferably, the particle size of the catalyst is 500 nm to 5000 nm.

[0029] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0030] The thickener is selected from amide thickeners, preferably selected from at least one of acrylamide polymers;

[0031] Further preferably, the thickener is selected from at least one of acrylamide (AM) / 2-acrylamido-2-methylpropanesulfonic acid (AMPS) copolymers; specifically, at least one of AM / AMPS copolymers with different AM / AMPS ratios or different molecular weights;

[0032] Further preferably, the molecular weight of the thickener is 10 million to 20 million.

[0033] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0034] The co-crosslinking agent is selected from at least one of aldehydes and hexamethylenetetramine;

[0035] Preferably, the aldehyde is selected from at least one of formaldehyde, acetaldehyde, furfural and hexamethylenetetramine;

[0036] In the present invention, the co-crosslinking agent reacts with the phenolic hydroxyl groups in the "unreacted lignin and degradation products" to form a phenolic aldehyde prepolymer, which plays a role similar to that of a phenolic aldehyde resin crosslinking agent, and can also crosslink with the amide groups in the amide thickener to form a complex interpenetrating network structure;

[0037] More preferably, the co-crosslinking agent is a mixture of aldehyde and hexamethylenetetramine;

[0038] More preferably, the co-crosslinking agent is a mixture of formaldehyde and hexamethylenetetramine, and the mass ratio of formaldehyde to hexamethylenetetramine is 1:(8 - 15). In the system of the present invention, the combined action of the two is that below the decomposition temperature of hexamethylenetetramine, formaldehyde can crosslink with lignin first, and hexamethylenetetramine decomposes at high temperature to form formaldehyde, and hexamethylenetetramine plays a role only after high-temperature decomposition.

[0039] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0040] The co-solvent is selected from polar organic solvents miscible with water, preferably alcohol solvents, and more preferably at least one of ethanol, ethylene glycol, and isopropanol.

[0041] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0042] In the present invention, the water is not specifically limited and can be river water, lake water, atmospheric water, seawater, groundwater, artificial water, oilfield produced water, etc.; preferably, the water has a salinity of less than 50000 mg / L, and preferably, the salinity of the water is 0 - 20000 mg / L.

[0043] The present invention pumps the above plugging agent into and migrates it to the deep formation. With the injection of steam, the formation temperature increases. Under the action of a solid acid catalyst and a co-solvent, lignin decomposes in-situ to produce highly active degradation products, and these products undergo crosslinking reactions with other components in the reaction to plug the steam channeling path; in addition, the solid acid catalyst not only plays a catalytic role in the reaction system but also acts as an inorganic particle plugging agent, enhancing the colloid strength and facilitating plugging. This system expands the temperature range of use and has a relatively high strength, with the characteristics of large plugging strength, wide application range, high plugging efficiency, etc. It effectively reduces the concentrations of the main agent and the crosslinking agent, reduces the production cost of the plugging agent, meets the performance and economic requirements of on-site construction, and has high practicality.

[0044] The second object of the present invention is to provide a preparation method of an in-situ crosslinked lignin plugging agent for underground, comprising the following steps:

[0045] Mix the raw materials including lignin, catalyst, thickener, co-crosslinking agent, co-solvent, and water evenly to obtain the in-situ crosslinked lignin plugging agent for underground;

[0046] Preferably, it is used for the preparation of the in-situ crosslinked lignin plugging agent for underground described in any one of the first objects of the present invention.

[0047] In the preparation method of the in-situ crosslinked lignin plugging agent of the present invention, preferably, it includes the following steps:

[0048] (1) Dissolve the thickener in water until completely dissolved;

[0049] (2) Add a co-crosslinking agent and a co-solvent, mix evenly, and optionally adjust the pH value.

[0050] (3) Add lignin and dissolve it completely, then add a catalyst and mix evenly to obtain the in-situ crosslinked lignin plugging agent underground.

[0051] Preferably, adjust the pH value to 8.5 - 10.5. The pH regulators used for adjusting the pH in the present invention are common acids and bases.

[0052] In the preparation method of the in-situ crosslinked lignin plugging agent underground according to the present invention, preferably,

[0053] Based on the total weight of lignin, catalyst, thickener, co-crosslinking agent, co-solvent and water being 100%, it includes:

[0054] The content of the lignin is 1 - 7.5 wt%.

[0055] The content of the catalyst is 0.1 - 0.75 wt%.

[0056] The content of the thickener is 0.02 - 0.2 wt%.

[0057] The content of the co-crosslinking agent is 0.3 - 2 wt%.

[0058] The content of the co-solvent is 0.5 - 5 wt%.

[0059] In the preparation method of the in-situ crosslinked lignin plugging agent underground according to the present invention, preferably,

[0060] The content of the lignin is 2 - 5 wt%; and / or,

[0061] The content of the catalyst is 0.2 - 0.5 wt%; and / or,

[0062] The content of the thickener is 0.05 - 0.15 wt%; and / or,

[0063] The content of the co-crosslinking agent is 0.5 - 1.8 wt%; and / or,

[0064] The content of the co-solvent is 1 - 3 wt%.

[0065] In the present invention, those skilled in the art can also add other commonly used substances in the art according to the common knowledge in the art, and the amount of this substance added is the ordinary amount in the art.

[0066] In the preparation method of the in-situ crosslinked lignin plugging agent underground according to the present invention, preferably,

[0067] The lignin is selected from at least one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the effective content of lignin in the lignin is 80-99.9 wt%.

[0068] In the in-situ crosslinked lignin plugging agent in the ground of the present invention, preferably,

[0069] The catalyst is selected from at least one of solid acid catalysts;

[0070] Preferably, the catalyst is selected from at least one of MOR zeolite, USY zeolite and ZSM-5 zeolite;

[0071] Further preferably, the particle size of the catalyst is 500 nm to 5000 nm.

[0072] In the preparation method of the in-situ crosslinked lignin plugging agent in the ground of the present invention, preferably, the thickener is selected from amide thickeners, preferably selected from at least one of acrylamide polymers;

[0073] Further preferably, the thickener is selected from at least one of acrylamide (AM) / 2-acrylamido-2-methylpropanesulfonic acid (AMPS) copolymers; specifically, at least one of AM / AMPS copolymers with different AM / AMPS ratios or different molecular weights;

[0074] Further preferably, the molecular weight of the thickener is 10 million to 20 million.

[0075] In the preparation method of the in-situ crosslinked lignin plugging agent in the ground of the present invention, preferably,

[0076] The co-crosslinking agent is selected from at least one of aldehydes and hexamethylenetetramine;

[0077] Preferably, the aldehyde is selected from at least one of formaldehyde, acetaldehyde, furfural and hexamethylenetetramine;

[0078] In the present invention, the co-crosslinking agent reacts with the phenolic hydroxyl groups in "unreacted lignin and degradation products" to form a phenolic aldehyde prepolymer, which plays a role similar to that of a phenolic resin crosslinking agent, and can also crosslink with the amide groups in the amide thickener to form a complex interpenetrating network structure;

[0079] More preferably, the co-crosslinking agent is a mixture of aldehyde and hexamethylenetetramine;

[0080] Even more preferably, the co-crosslinking agent is a mixture of formaldehyde and hexamethylenetetramine, and the mass ratio of formaldehyde to hexamethylenetetramine is 1:(8-15). In the system of the present invention, the combined action of the two is that when the temperature is lower than the decomposition temperature of hexamethylenetetramine, formaldehyde can crosslink with lignin first, and hexamethylenetetramine decomposes at high temperature to form formaldehyde, and hexamethylenetetramine only plays a role after high-temperature decomposition.

[0081] In the preparation method of the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0082] The co-solvent is selected from polar organic solvents miscible with water, preferably alcohol solvents, and more preferably at least one of ethanol, ethylene glycol, and isopropanol.

[0083] In the in-situ crosslinked lignin plugging agent of the present invention, preferably,

[0084] The water in the present invention is not specifically limited and can be river water, lake water, atmospheric water, seawater, groundwater, artificially made water, produced water from oilfields, etc.; preferably, the water has a salinity of less than 50000 mg / L, and more preferably, the salinity of the water is 0 - 20000 mg / L.

[0085] The third object of the present invention is to provide the application of the in-situ crosslinked lignin plugging agent described in any one of the first object of the present invention or the in-situ crosslinked lignin plugging agent prepared by the method described in any one of the second object of the present invention in oil exploitation, preferably in plugging steam channeling channels in heavy oil exploitation.

[0086] In the application of the present invention, preferably,

[0087] Pump the in-situ crosslinked lignin plugging agent into the ground and transport it to the target formation; inject steam and preheat the formation to the required reaction temperature to cause the in-situ crosslinked lignin plugging agent to react and plug the steam channeling pores;

[0088] Preferably, the reaction temperature is higher than 120 °C.

[0089] In the present invention, the undiluted plugging agent is pumped into the ground and transported to the target formation; steam is injected to preheat the formation to the required reaction temperature, and lignin is in-situ degraded under the action of a catalyst to obtain highly active products; the highly active products react with other components in the undiluted solution to obtain a high-strength plugging agent to plug the pores.

[0090] The endpoints and any values within the ranges disclosed in the present invention are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0091] Compared with the prior art, the present invention has at least the following advantages:

[0092] The present invention provides an underground in-situ crosslinked lignin plugging agent, a preparation method thereof, and an application. The lignin plugging agent in this patent comprises lignin, a catalyst, a thickener, a co-crosslinking agent, and a co-solvent. This plugging agent can be controllably gelled (1.5 - 120 h) within a relatively wide temperature range (> 120 °C), does not break gel within 60 days at a high temperature of 300 °C, has a dehydration rate < 5.1%, and a plugging rate higher than 98.8%, and can effectively plug the steam channel for a long time, achieving efficient development of heavy oil reservoirs.

[0093] Pump the above-mentioned plugging agent into and migrate it to the deep formation. With the injection of steam, the formation temperature rises above 120 °C. Under the action of a solid acid catalyst and a co-solvent, lignin decomposes in-situ to produce highly active degradation products such as guaiacol and homovanillic acid. These products undergo crosslinking reactions with the co-crosslinking agent and thickener in the reaction, plugging the steam channel. In addition, the solid acid catalyst not only plays a catalytic role in the reaction system but also acts as an inorganic particle plugging agent, enhancing the gel strength and facilitating plugging. This system expands the temperature range of use and has a relatively high strength, with characteristics such as a large plugging strength, a wide application range, and a high plugging efficiency. It effectively reduces the concentrations of the main agent and the crosslinking agent, reduces the production cost of the plugging agent, meets the performance and economic requirements of on-site construction, and has high practicality. Specific embodiments

[0094] The following describes the present invention in detail with reference to specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention still fall within the protection scope of the present invention.

[0095] In addition, it should be noted that the various specific technical features described in the following specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0096] Furthermore, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions thus formed belong to a part of the original public content of this specification and also fall within the protection scope of the present invention.

[0097] Source of raw materials:

[0098] The enzymatically hydrolyzed lignin is purchased from Shandong Lonli Biological Technology Co., Ltd., and the effective lignin content is 94.8 wt%.

[0099] The alkali lignin is purchased from J&K Scientific Ltd.

[0100] The amide thickener (AM / AMPS copolymer) was purchased from Shandong Baomo Biochemical Co., Ltd., with an effective content of about 88 wt%, and a weight-average molecular weight of 15 million. The amide thickener used is a commonly used amide thickener in the art, with a white granular appearance, less than 12 wt% water content, and an effective content greater than 88 wt%.

[0101] USY zeolite, ZSM-5 zeolite, and MOR zeolite were purchased from Tianjin Nanhua Catalyst Co., Ltd., with particle sizes of 1000 nm - 1500 nm, 600 nm - 1200 nm, and 1000 nm - 2000 nm, respectively.

[0102] For the raw materials used in the examples and comparative examples, if not specifically defined, they are all disclosed in the prior art. For example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0103] Testing methods:

[0104] Gel formation test:

[0105] Place the plugging agent in a high-temperature and high-pressure reactor, at the gel formation temperature. Observe the gel formation progress by taking samples from the reactor every 4 h; after gel formation, observe the gel formation progress by taking samples from the reactor every 2 days.

[0106] Strength test:

[0107] The gel strength was tested by the breakthrough vacuum method. The specific operation is as follows: Place the formed gel in the test bottle of the breakthrough vacuum experimental device. Insert the tip of a 1 mL pipette 1 cm below the gel surface. Start the vacuum pump and slowly adjust the knob to increase the system vacuum. When air breaks through the gel, the maximum reading of the vacuum gauge is the breakthrough vacuum of the gel. Each sample was measured 3 times, and the arithmetic mean was taken as its final strength value.

[0108] Plugging rate test:

[0109] Prepare a simulated core (core diameter is 25 mm, length is 600 mm), evacuate and saturate it with water. First, inject water into the core at a certain flow rate and measure the pre-plugging permeability (k0) of the core; then, under the condition of a gas-liquid ratio of 1:1, inject different plugging agents into the core at an injection rate of 2 mL / min. After stabilization (gel formation), heat it to 300 °C with a heating jacket for subsequent steam flooding; finally, inject water and measure the post-plugging permeability (k') of the core. Use the plugging rate as a parameter to characterize the plugging effect of the plugging agent. The calculation formula for the plugging rate is where k0 is the pre-plugging permeability, μm 2 ; k' is the post-plugging permeability, μm 2 .

[0110] Dehydration rate test: After the high-temperature stability test at 300 °C, measure the volume of free water outside the colloid in the reactor. The dehydration rate is the ratio of the volume of free water to the total volume of the gelling solution, and the volumes are all measured at room temperature.

[0111] Example 1

[0112] Dissolve 0.1 g of amide thickener (AM / AMPS copolymer) in 80 g of prepared water with a salinity of 10,000 mg / L, and stir until evenly dissolved at a rotation speed of 500 r / min; then, add 1.2 g of a mixture of formaldehyde and hexamine (the mass ratio of formaldehyde to hexamine is 1:12), 2.2 g of isopropanol, and then add sodium hydroxide to adjust the pH to 9.5; finally, add 3.5 g of enzymatically hydrolyzed lignin and dissolve it completely, and then add 0.38 g of solid acid catalyst ZSM-5 molecular sieve, stir until evenly mixed, and quantitatively add prepared water with a salinity of 10,000 mg / L to 100 g to obtain a plugging agent.

[0113] After the above plugging agent gels at 150 °C, its strength reaches 0.088 MPa; and it does not break gel at 300 °C for 78 days, with a dehydration rate of 3.6%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 99.5%.

[0114] Example 2

[0115] Dissolve 0.05 g of amide thickener (AM / AMPS copolymer) in 80 g of prepared water with a salinity of 20,000 mg / L, and stir until evenly dissolved at a rotation speed of 500 r / min; then, add 0.5 g of a mixture of formaldehyde and hexamine (the mass ratio of formaldehyde to hexamine is 1:8), 1 g of isopropanol, and then add sodium hydroxide to adjust the pH to 9; finally, add 2 g of enzymatically hydrolyzed lignin and dissolve it completely, and then add 0.2 g of solid acid catalyst ZSM-5 molecular sieve, stir until evenly mixed, and quantitatively add prepared water with a salinity of 20,000 mg / L to 100 g to obtain a plugging agent.

[0116] After the above plugging agent gels at 180 °C, its strength reaches 0.083 MPa; and it does not break gel at 300 °C for 66 days, with a dehydration rate of 5.0%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 99.0%.

[0117] Example 3

[0118] Dissolve 0.15 g of amide thickener (AM / AMPS copolymer) in 80 g of prepared water with a salinity of 8000 mg / L, and stir until evenly dissolved at a rotation speed of 500 r / min; then, add 1.8 g of a mixture of formaldehyde and hexamethylenetetramine (mass ratio of formaldehyde to hexamethylenetetramine is 1:15), 3 g of isopropanol, and then add sodium hydroxide to adjust the pH to 9; finally, add 5 g of enzymatically hydrolyzed lignin and dissolve it completely, and then add 0.5 g of solid acid catalyst ZSM-5 molecular sieve, stir until evenly mixed, and quantitatively add prepared water with a salinity of 8000 mg / L to 100 g to obtain a plugging agent.

[0119] After the above plugging agent gels at 120 °C, the strength reaches 0.081 MPa; and it does not break gel at 300 °C for 62 days, with a dehydration rate of 4.7%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 99.2%.

[0120] Example 4

[0121] Dissolve 0.1 g of amide thickener (AM / AMPS copolymer) in 80 g of prepared water with a salinity of 10000 mg / L, and stir until evenly dissolved at a rotation speed of 500 r / min; then, add 1.2 g of furfural, 2.2 g of ethanol, and then add sodium hydroxide to adjust the pH to 9.5; finally, add 3.5 g of alkali lignin and dissolve it completely, and then add 0.38 g of solid acid catalyst USY molecular sieve, stir until evenly mixed, and quantitatively add prepared water with a salinity of 10000 mg / L to 100 g to obtain a plugging agent.

[0122] After the above plugging agent gels at 150 °C, the strength reaches 0.080 MPa; and it does not break gel at 300 °C for 66 days, with a dehydration rate of 4.9%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 98.8%.

[0123] Example 5

[0124] Conduct the experiment according to the method of Example 1, except that only 1.2 g of formaldehyde is added. The obtained plugging agent has a strength of 0.082 MPa after gelling at 150 °C; and it does not break gel at 300 °C for 62 days, with a dehydration rate of 5.0%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 98.9%.

[0125] Example 6

[0126] Conduct the experiment according to the method of Example 1, except that only 1.2 g of hexamethylenetetramine is added. The obtained plugging agent has a strength of 0.081 MPa after gelling at 150 °C; and it does not break gel at 300 °C for 66 days, with a dehydration rate of 4.7%; the obtained plugging agent is subjected to a plugging test, and the plugging rate is 99.2%.

[0127] Example 7

[0128] The experiment was carried out according to the method of Example 1, except that 0.38 g of solid acid catalyst MOR zeolite was added. The strength of the obtained plugging agent reached 0.078 MPa after gelling at 150 °C; and it did not break gel at 300 °C for 62 days, with a dehydration rate of 4.6%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 98.8%.

[0129] Example 8

[0130] The experiment was carried out according to the method of Example 1, except that 1.2 g of a mixture of acetaldehyde and hexamethylenetetramine (mass ratio of acetaldehyde to hexamethylenetetramine was 1:12) was added. The strength of the obtained plugging agent reached 0.076 MPa after gelling at 150 °C; and it did not break gel at 300 °C for 62 days, with a dehydration rate of 4.3%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 99.1%.

[0131] Example 9

[0132] The experiment was carried out according to the method of Example 1, except that sodium hydroxide was further added to adjust the pH to 10.5. The strength of the obtained plugging agent reached 0.082 MPa after gelling at 150 °C; and it did not break gel at 300 °C for 68 days, with a dehydration rate of 5.1%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 99.2%.

[0133] Comparative Example 1

[0134] The experiment was carried out according to the method of Example 1, except that the enzymatically hydrolyzed lignin was replaced with an amide thickener. The strength of the obtained plugging agent was 0.091 MPa after gelling at 150 °C, and it broke gel in 2 days, with a dehydration rate of 82.6%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 91.2%.

[0135] Comparative Example 2

[0136] The experiment was carried out according to the method of Example 1, except that the solid acid catalyst ZSM-5 zeolite was replaced with γ-Al2O3. The strength of the obtained plugging agent was 0.043 MPa after gelling at 150 °C, and it broke gel in 46 days, with a dehydration rate of 28.9%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 50.2%.

[0137] Comparative Example 3

[0138] The experiment was carried out according to the method of Example 1, except that isopropanol was replaced with n-butanol. The strength of the obtained plugging agent was 0.055 MPa after gelling at 150 °C, and it broke gel in 48 days, with a dehydration rate of 26.1%; the obtained plugging agent was subjected to a plugging test, and the plugging rate was 62.1%.

[0139] The present invention has been described in detail in connection with specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention shall be subject to the appended claims.

[0140] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0141] When this specification uses prefixes such as "known to those skilled in the art", "prior art", or their similar terms to introduce materials, substances, methods, steps, devices, or components, etc., the objects introduced by such prefixes cover those commonly used in the art at the time when this application is filed, but also include those that are not commonly used at present but will become recognized by the art as suitable for similar purposes.

[0142] In the context of this specification, any matters or things not mentioned, except for the clearly stated content, shall directly apply to those known in the art without any changes.

Claims

1. An in-situ crosslinked lignin plugging agent for underground use, characterized in that: The plugging agent comprises lignin, a catalyst, a thickener, a co-crosslinking agent, a cosolvent and water; Based on the total weight of lignin, a catalyst, a thickener, a co-crosslinking agent, a cosolvent and water being 100%, it includes: The content of the lignin is 1-7.5 wt%; The content of the catalyst is 0.1-0.75 wt%; The content of the thickener is 0.02-0.2 wt%; The content of the co-crosslinking agent is 0.3-2 wt%; The content of the cosolvent is 0.5-5 wt%.

2. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The content of the lignin is 2-5 wt%; and / or, The content of the catalyst is 0.2-0.5 wt%; and / or, The content of the thickener is 0.05-0.15 wt%; and / or, The content of the co-crosslinking agent is 0.5-1.8 wt%; and / or, The content of the cosolvent is 1-3 wt%.

3. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The lignin is selected from at least one of alkali lignin and enzymatically hydrolyzed lignin; more preferably, the effective content of lignin in the lignin is 80-99.9 wt%.

4. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The catalyst is selected from at least one of solid acid catalysts; Preferably, the catalyst is selected from at least one of MOR zeolite, USY zeolite and ZSM-5 zeolite; Further preferably, the particle size of the catalyst is 500 nm to 5000 nm.

5. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The thickener is selected from amide thickeners, preferably selected from at least one of acrylamide polymers; Further preferably, the thickener is selected from at least one of acrylamide / 2-acrylamido-2-methylpropanesulfonic acid copolymers; Further preferably, the molecular weight of the thickener is 10 million to 20 million.

6. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The co-crosslinking agent is selected from at least one of aldehyde and hexamethylenetetramine; Preferably, the aldehyde is selected from at least one of formaldehyde, acetaldehyde, furfural and hexamethylenetetramine; More preferably, the co-crosslinking agent is a mixture of aldehyde and hexamethylenetetramine; Still further preferably, the co-crosslinking agent is a mixture of formaldehyde and hexamethylenetetramine, and the mass ratio of formaldehyde to hexamethylenetetramine is 1:(8-15).

7. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The cosolvent is selected from polar organic solvents miscible with water, preferably alcohol solvents, and further preferably at least one of ethanol, ethylene glycol and isopropanol.

8. The in-situ crosslinked lignin plugging agent for underground use according to claim 1, characterized in that: The water is water with a salinity of less than 50000 mg / L, preferably, the salinity of the water is 0-20000 mg / L.

9. A preparation method of an in-situ crosslinked lignin underground plugging agent, characterized in that, It includes the following steps: Mix the raw materials including lignin, catalyst, thickener, co-crosslinking agent, co-solvent and water evenly to obtain an in-situ crosslinked lignin plugging agent for underground use; Preferably used for the preparation of the in-situ crosslinked lignin plugging agent for underground use according to any one of claims 1-8.

10. The preparation method of the in-situ crosslinked lignin plugging agent underground according to claim 9, characterized in that, Comprising the following steps: (1) Dissolve the thickener in water until completely dissolved; (2) Add the co-crosslinking agent and co-solvent, mix evenly, and optionally adjust the pH value; (3) Add lignin, dissolve completely, then add the catalyst, mix evenly to obtain the in-situ crosslinked lignin plugging agent for underground use; Preferably, adjust the pH value to 8.5-10.

5.

11. Application of the in-situ crosslinked lignin plugging agent for underground use according to any one of claims 1-8 or the in-situ crosslinked lignin plugging agent prepared by the method according to any one of claims 9-10 in oil exploitation, preferably in plugging steam channeling channels in heavy oil exploitation.

12. The application according to claim 11, wherein: Pump the in-situ crosslinked lignin plugging agent for underground use into the ground and transport it to the target formation; inject steam to preheat the formation to the required reaction temperature to make the in-situ crosslinked lignin plugging agent for underground use react and plug the steam channeling holes; Preferably, the reaction temperature is higher than 120°C.