CN113234425B - Composite aluminum gel plugging agent for deep profile control of medium-low permeability oil reservoir and preparation method and application thereof - Google Patents

Abstract

The invention relates to a composite aluminum gel plugging agent for profile control of a medium-low permeability oil reservoir deep part, and a preparation method and application thereof. 6 to 10 percent of polyaluminium chloride, 2 to 6 percent of forced hydrolytic agent, 0.05 to 0.1 percent of polyacrylamide, 1 to 2 percent of chromium crosslinking agent, 0.1 to 0.2 percent of organic acid and the balance of water. The composite aluminum gel plugging agent suitable for medium-temperature oil reservoirs and high-temperature oil reservoirs is prepared by screening polyaluminum chlorides with different basicities. The prepared composite aluminum gel gelling solution has low viscosity and good injectivity in low-permeability oil reservoirs; the prepared composite aluminum gel has controllable gelling time and is suitable for profile control and plugging of the deep part of an oil reservoir; the prepared composite aluminum gel has high strength after gelling, the elastic modulus is more than 10000Pa, and the composite aluminum gel has good plugging capability in cracks and the breakthrough pressure is more than 5MPa.

Description

Composite aluminum gel plugging agent for deep profile control of medium-low permeability oil reservoir and preparation method and application thereof

The technical field is as follows:

the invention mainly relates to a salt-tolerant high-strength composite aluminum gel plugging agent, a preparation method and application thereof. Is applied to the technical field of oilfield chemistry.

Background art:

with the increasing demand for petroleum resources, the recoverable reserve of medium-high permeability oil reservoirs is decreased and the proportion of low permeability reserve explored in China is as high as 65%, so that the development of low permeability oil reservoirs becomes the key point of current research. In the low-permeability reservoir, reservoir fractures are developed relatively, and the fractured low-permeability reservoir is formed. Due to the existence of the cracks, injected water can easily flow along the cracks in the water injection development process, and the water drive efficiency is reduced. At present, the profile control plugging technology is one of effective means for solving the problem. The key of the profile control plugging of the low-permeability oil field is that the oil layer is not damaged while the crack is effectively plugged. Therefore, the polymer gel plugging agent is widely applied to oil fields due to the advantages of simple operation, controllable gelling time and the like. In a fractured low-permeability oil reservoir, the injection capacity of the plugging agent is limited due to small matrix permeability, so the viscosity of the plugging agent is required to be not too high; in addition, when the plugging agent is used for plugging cracks, the plugging agent is required to have high plugging strength in the cracks.

For profile control plugging of fractured low-permeability oil reservoirs, the commonly used polymer gel plugging agents comprise a pre-gel system and organogels suitable for different oil reservoir conditions. The pre-gelled system is applied to a fractured oil reservoir, the gelling performance of the pre-gelled system can be prevented from being influenced by formation factors, and the plugging capability of the pre-gelled system is limited. In addition, aiming at different oil reservoir conditions, the organogel plugging agent with good performance is prepared by selecting different types of polymers, additives and the like, but the organogel plugging agent still has many problems, on one hand, the plugging agent is expensive to prepare, so that the large-range use of the plugging agent is limited, on the other hand, the plugging agent can reach the strength for plugging cracks, the amount of the polymers needs to be relatively high, the initial viscosity of the gelling solution is very high, and the injection capacity is poor.

There are also many patent documents reported about blocking agents, such as: CN104449618A discloses a temperature-resistant salt-tolerant high-temperature self-crosslinking in-situ polymerization water shutoff gel, and CN109280542A discloses a high-temperature-resistant gel plugging agent, and a preparation method and application thereof. The technology mainly forms the high-strength plugging agent by polymerizing the high-dosage monomers underground, and the plugging agent has the characteristics of good injectability, long-term stability, good plugging performance and the like, but has the advantages of high cost, short gelling time, sensitive system formula, great influence of stratum factors and unsuitability for deep profile control.

Patent documents on inorganic gel blocking agents, for example: CN103627376A discloses a water glass inorganic gel plugging agent and a preparation method and a use method thereof, the plugging agent has excellent injectivity, has good plugging capability and water scouring resistance after gelling, is suitable for profile control plugging of medium and low permeability reservoirs, has short gelling time, and is largely dehydrated and condensed into a compact glass body at high temperature. CN108300438A discloses an inorganic aluminum gel water shutoff agent, which is suitable for high salinity, has good salt tolerance, and good gelling time and plugging performance, but is poor in thermal stability at high temperature, serious in dehydration, and not suitable for high-temperature oil reservoirs.

The invention content is as follows:

aiming at the defects of the prior art, particularly in a low-permeability fracture oil reservoir, the contradiction between the injectivity and the plugging strength of the plugging agent is difficult to realize effective water control. The invention provides a composite aluminum gel plugging agent and preparation and application thereof. The composite aluminum gel comprises the components of polyaluminum chloride (PAC), a forced hydrolyzing agent, polyacrylamide, a chromium crosslinking agent and an organic acid.

Description of terms:

degree of salification of polyaluminum chloride: the basic component for causing the poly aluminum chloride to be varied is OH ions, and the index for measuring the OH ions in the poly aluminum chloride is Basicity (B), which is also called alkalization degree and hydroxyl-aluminum ratio. The basicity is generally defined as one third of the equivalent percentage of OH to Al in the polyaluminum chloride molecule ([ OH ]/[ Al ] × 100 (%)).

The technical scheme of the invention is as follows:

the composite aluminum gel plugging agent comprises the following components in percentage by mass:

6 to 10 percent of polyaluminum chloride, 2 to 4 percent of forced hydrolytic agent, 0.05 to 0.1 percent of polyacrylamide, 1 to 2 percent of chromium crosslinking agent, 0.1 to 0.2 percent of organic acid and the balance of water.

According to the invention, preferably, the composite aluminum gel plugging agent comprises the following components in percentage by mass:

8% of polyaluminum chloride, 2% -4% of forced hydrolytic agent, 0.1% of polyacrylamide, 1% of chromium crosslinking agent, 0.1% of organic acid and the balance of water.

According to the invention, preferably, the composite aluminum gel plugging agent comprises the following components in percentage by mass:

8% of polyaluminium chloride, 2% of forced hydrolytic agent, 0.1% of polyacrylamide, 1% of chromium crosslinking agent, 0.15% of organic acid and the balance of water.

According to the invention, the polyaluminium chloride is preferably light yellow powder with the effective content of 30%;

preferably, the salinity of the polyaluminium chloride is 40% -80%, further preferably 40%, 60% and 80%; most preferably, the basicity is 80% for reservoir temperatures of 70 ℃ to 90 ℃ and 60% for reservoir temperatures >90 ℃.

According to the invention, preferably, the forced hydrolysis agent is urea.

According to the present invention, preferably, the polyacrylamide is nonionic or cationic polyacrylamide, further preferably cationic polyacrylamide;

preferably, the cationic polyacrylamide has an ionic degree of 5% to 30%, more preferably 5%, 15%, 30%, most preferably 5%;

preferably, the cationic polyacrylamide has a molecular weight of 700 to 800 ten thousand.

According to the present invention, preferably, the chromium crosslinking agent is chromium acetate, chromium lactate or chromium citrate, more preferably chromium acetate.

According to the invention, preferably, the organic acid is acetic acid, malonic acid or citric acid, more preferably citric acid.

According to the invention, the functions of the components are as follows:

the polyaluminum chloride used in the invention is an inorganic high molecular polymer with low price and environmental protection, not only can meet the requirement of high strength, but also has good stability, simple preparation and little influence from stratum conditions. Especially under severe oil reservoir conditions such as high temperature and high salinity, the use cost of the polymer gel system is greatly increased. The invention adopts the polyaluminum chloride, and can form stable high-strength aluminum gel under the conditions of reservoir temperature of 130 ℃ and mineralization degree of 0-100000 mg/L.

The forced hydrolyzing agent used in the present invention is urea which is inexpensive and mainly plays a role of promoting the hydrolysis of aluminum salt. The process of converting polyaluminium chloride into aluminium gel is mainly generated by hydrolysis of aluminium ions, the spontaneous hydrolysis process is usually very slow, and the hydrolysis process is accelerated by adding alkaline substances into the polyaluminium chloride solution to increase the pH value of the polyaluminium chloride solution. The hydrolysis process is mainly hydrolysis of aluminum salt to form monomer oligomer, further form oligomer, high polymer and larger aggregate, and form a network structure through hydroxyl bridging.

The polyacrylamide used in the invention is cationic polyacrylamide, and has good compatibility with aluminum gel. Although the single aluminum gel system has high strength, the formed jelly is cellular and has poor elasticity. On one hand, the cationic polyacrylamide can be crosslinked with organic chromium to form weak gel in the system, so that the toughness of the system is improved; on the other hand, the aluminum gel is complexed with part of polyaluminium chloride to form a network structure, so that the elasticity of the aluminum gel is improved, and the dehydration rate of the system is reduced.

The chromium crosslinking agent used in the invention can be crosslinked with part of cationic polymer to form weak gel, thereby enhancing the viscoelasticity of the system.

The organic acid used in the invention can adjust the reaction rate of the system, thereby controlling the gelling time of the gel. Under the condition of high-temperature oil reservoir (more than or equal to 90 ℃), the gelling time of the system is greatly shortened along with the rise of the temperature. The organic acid can be added to adjust the pH value of the gel forming liquid and control the hydrolysis rate of the polyaluminium chloride, and can be complexed with the chromium crosslinking agent to reduce the crosslinking speed of the polymer and chromium, so that the gel forming time of the whole system is delayed.

The preparation method of the composite aluminum gel plugging agent provided by the invention comprises the following steps:

(1) Preparing 1% of cationic polyacrylamide mother liquor, and fully stirring to completely dissolve the cationic polyacrylamide mother liquor;

(2) Adding a certain amount of polyaluminum chloride into water, uniformly stirring to completely dissolve the polyaluminum chloride, sequentially adding a forced hydrolyzing agent and a chromium crosslinking agent, and uniformly stirring; finally, adding a certain amount of cationic polymer mother liquor and the balance of water, and uniformly stirring;

(3) And (3) sealing the materials obtained in the step (2), and aging the materials at different oil reservoir temperatures respectively to obtain the composite aluminum gel plugging agent.

According to the invention, the composite aluminum gel plugging agent is applied as a plugging agent for profile control plugging of a low-permeability fracture oil reservoir, so that the water flooding wave and coefficient are improved, and the crude oil recovery rate is further improved.

The invention has the following beneficial effects:

1. the colloid-forming liquid prepared by the invention has low viscosity and good injectivity in low-permeability oil reservoirs.

2. The composite aluminum gel plugging agent provided by the invention has adjustable gelling time of 3-50 h, and is suitable for deep profile control of a fractured reservoir.

3. The composite aluminum gel has high strength and elasticity, the elastic modulus after aging for 10 days is more than 10000Pa, and the dehydration rate is less than 5%.

4. The composite aluminum gel has good temperature resistance (70-130 ℃) and salt tolerance (0-220000 mg/L), is low in preparation cost, and is suitable for profile control and plugging under severe oil reservoir conditions.

5. The composite aluminum gel has the advantages that through selecting the polyaluminium chlorides with different basicities, the gel prepared by the composite aluminum gel with high basicity has good stability and higher plugging strength at a medium oil reservoir temperature, and the breakthrough pressure is more than 5MPa; under the condition of a high-temperature oil reservoir, the composite aluminum gel prepared with low basicity has long gelling time and high plugging strength under the action of citric acid, and is suitable for deep profile control plugging of a low-permeability fracture oil reservoir.

6. The composite aluminum gel system has better unblocking performance, can be degraded by earth acid after gelling, has good degradation effect and little damage to the stratum.

The specific implementation mode is as follows:

the invention is further illustrated, but not limited, by the following specific examples.

The raw materials used in the examples are all conventional raw materials.

The salinity of the polyaluminum chloride used in the examples is determined by the reservoir temperature. Under the condition of medium-temperature oil reservoir, the polyaluminium chloride with 80% basicity is selected, and when the oil reservoir temperature is higher than 90 ℃, the polyaluminium chloride with 60% basicity is selected. The screening criteria were as follows:

1. gel forming time

The gel forming time of the composite aluminum gel is reduced along with the increase of the basicity, and the system gel forming time is longer at a medium reservoir temperature, so the polyaluminum chloride with high basicity is preferred. Under a high-temperature oil reservoir, the gel forming time of the system is greatly shortened, and the preferred polyaluminium chloride with low basicity can prolong the gel forming time of the system under the high-temperature condition, and the results are shown in table 1.

TABLE 1 influence of polyaluminium chloride basicity on gel formation time

2. Gel strength

The gel forming strength of the composite aluminum gel is improved along with the increase of the basicity, and at a medium oil reservoir temperature, the degree of gel forming reaction of the system is relatively low, and the strength is weaker than that of a high-temperature oil reservoir, so that the polyaluminium chloride with high basicity is preferably used for improving the gel forming strength of the system. Under the high-temperature oil reservoir, the system has high gelling reaction degree, the formed gel strength is higher, the polyaluminium chloride with low basicity can meet the strength requirement, and the polyaluminium chloride with low basicity is selected to combine into the gel time requirement, so the polyaluminium chloride with relatively low basicity is preferably selected in the high-temperature oil reservoir, and the results are shown in table 2.

TABLE 2 influence of polyaluminium chloride basicity on gel strength (5 days of ageing)

3. Rate of dewatering

The higher the basicity, the higher the dehydration rate of the composite aluminum gel with the increase of the temperature. The increase of the dehydration rate can reduce the strength and the plugging capability of the system, so the dehydration rate of the system is controlled as much as possible under the condition of meeting the gelling time and the gel strength. Therefore, the polyaluminium chloride with high basicity is preferred at the medium reservoir temperature, and the polyaluminium chloride with low basicity is preferred at the high reservoir temperature, and the results are shown in table 3.

TABLE 3 influence of degree of basicity of polyaluminum chloride on dehydration rate (aging 100 days)

For a clearer understanding of the present invention, reference will now be made in detail to the following examples, which are not intended to limit the scope of the present invention. In the embodiment, 1% of cationic polyacrylamide mother liquor is prepared for standby, the ionicity of polyacrylamide is 5%, and the molecular weight is 700-800 ten thousand.

Example 1:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Example 2:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with the basicity of 60% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the mixture into an ampoule bottle, sealing, and placing the ampoule bottle in a constant-temperature oil bath at 110 ℃ to measure the gelling property.

Example 3:

preparing 100g of gel-forming liquid, adding 6g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Example 4:

preparing 100g of gel-forming liquid, adding 10g of polyaluminium chloride with basicity of 80 percent into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1 percent cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Example 5:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 4g of urea, 1g of chromium acetate and 0.1g of citric acid, uniformly stirring to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Example 6:

preparing 100g of gel-forming liquid, adding 6g of polyaluminium chloride with the basicity of 60% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 4g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the mixture into an ampoule bottle, sealing, and placing the ampoule bottle in a constant-temperature oil bath at 110 ℃ to measure the gelling property.

Example 7:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with the basicity of 60% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 5g of urea, 1g of chromium acetate and 0.2g of citric acid, uniformly stirring to fully mix the polyaluminium chloride, adding 10g of 0.5% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the mixture into an ampoule bottle, sealing, and placing the ampoule bottle in a constant-temperature oil bath at 110 ℃ to measure the gelling property.

Comparative example 1:

preparing 100g of gel forming liquid, adding 8g of polyaluminum chloride with basicity of 80%, adding 50g of water, stirring to completely dissolve the polyaluminum chloride, adding 2g of sodium hydroxide, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix, adding 10g of 1% cationic polyacrylamide mother liquor and the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Comparative example 2:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with the basicity of 60% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Comparative example 3:

preparing 100g of gel-forming liquid, adding 4g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Comparative example 4:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate, 0.1g of citric acid and the balance of water, and stirring uniformly to fully mix the materials to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Comparative example 5:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea and 0.1g of citric acid, uniformly stirring to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the gel in an ampoule bottle, sealing, and placing in a constant-temperature water bath at 80 ℃ to determine the gelling property.

Comparative example 6:

preparing 100g of gel-forming liquid, adding 8g of polyaluminium chloride with basicity of 80% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea, 1g of chromium acetate and 0.1g of citric acid, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel-forming liquid. Placing the mixture into an ampoule bottle, sealing, and placing the ampoule bottle in a constant-temperature oil bath at 110 ℃ to measure the gelling property.

Comparative example 7:

preparing 100g of gel forming liquid, adding 8g of polyaluminium chloride with the basicity of 60% into a beaker, adding 50g of water, stirring to completely dissolve the polyaluminium chloride, adding 2g of urea and 1g of chromium acetate, stirring uniformly to fully mix the polyaluminium chloride, adding 10g of 1% cationic polyacrylamide mother liquor, adding the balance of water, and stirring for 10min to obtain the composite aluminum chloride gel forming liquid. Placing the mixture into an ampoule bottle, sealing, and placing the ampoule bottle in a constant-temperature oil bath at 110 ℃ to measure the gelling property.

Evaluation of plugging performance:

the plugging ability of the composite aluminum gels provided in examples 1 to 2 and comparative examples 1 to 7 was examined. A stainless steel tubule with the inner diameter of 1mm and the length of 0.5m is used for simulating cracks, the plugging capability of the plugging agent in the tubule is investigated, and the specific experimental process is as follows: 1) Cleaning a pipeline, namely injecting alcohol into a thin pipe, soaking for a period of time, then washing with clear water, and finally rinsing with gelling liquid to ensure midday sundries of the pipeline; 2) Injecting and aging the gelling solution, namely uniformly injecting the gelling solution into the cleaned pipeline until a large amount of gelling solution flows out of the outlet end, then sealing the inlet end and the outlet end, and aging in a constant-temperature water bath or oil bath to gelatinize; 3) And (3) water injection displacement, after the gel forming liquid is aged in the tubule for 10 days, displacing the plugging agent in the tubule at a water drive speed of 1ml/min, recording pressure change, and recording the pressure when the first drop flowing out from the outlet end continuously discharges liquid as breakthrough pressure.

The gelling properties of the composite aluminum gels prepared in example 1 and comparative examples 1-6 are shown in Table 4.

TABLE 4 measurement and evaluation of gelling Properties of composite aluminum gels of different systems

As can be seen from Table 4, in comparative example 1, sodium hydroxide is used as the strengthening hydrolytic agent, although high-strength gel can be formed, the gelling time is extremely short, the dehydration rate is relatively high, and the deep profile control plugging of the plugging agent is difficult to ensure. Comparative example 2 has a salt content of 60% and can satisfy the requirements of gel formation time and dehydration rate, but has relatively weak strength, and in addition, the application of the polyaluminum chloride with a salt content of 80% can satisfy the requirements of gel formation time, strength and dehydration rate. Comparative example 3 uses 4% polyaluminium chloride, which after gelling, has a greatly reduced strength and is not conducive to plugging of cracks. Compared with the systems of comparative examples 4 and 5, polyacrylamide and chromium cross-linking agents are not added respectively, so that the formed gel has relatively weak strength and poor elasticity, and the blocking capacity is obviously reduced. For example 6, the gel strength increased greatly with increasing temperature, but the dehydration rate was high.

The gelling properties of the composite aluminum gels prepared in example 2 and comparative examples 2, 6 and 7 are shown in table 5.

TABLE 5 measurement and evaluation of gelling Properties of composite aluminum gels of different systems

As can be seen from Table 5, the temperature of comparative example 2 is increased, the strength of the plugging agent is greatly improved, but the dehydration rate is greatly increased. Comparative example 6 at high temperature, the gel forming time is obviously shortened by using the polyaluminium chloride with high basicity, the dehydration rate is obviously increased, and the plugging capability is deteriorated. Comparative example 7 no organic acid was added, gel formation time was drastically shortened and dehydration rate was greatly increased.

The above results show that: the plugging agent provided by the invention has good stability and excellent plugging performance. Therefore, the high-strength plugging agent can effectively plug water drive channeling, is beneficial to improving the recovery ratio of crude oil, and has long-term stability.

Claims (9)

1. The composite aluminum gel plugging agent comprises the following components in percentage by mass:

6 to 10 percent of polyaluminium chloride, 2 to 4 percent of forced hydrolytic agent, 0.05 to 0.1 percent of polyacrylamide, 1 to 2 percent of chromium crosslinking agent, 0.1 to 0.2 percent of organic acid and the balance of water;

the salinity of the polyaluminium chloride is 40-80%, the forced hydrolyzing agent is urea, and the polyacrylamide is cationic polyacrylamide.

2. The composite aluminum gel plugging agent of claim 1, wherein the composite aluminum gel plugging agent comprises the following components in percentage by mass:

8% of polyaluminum chloride, 2% -4% of forced hydrolytic agent, 0.1% of polyacrylamide, 1% of chromium crosslinking agent, 0.1% of organic acid and the balance of water.

3. The composite aluminum gel plugging agent of claim 1, wherein the composite aluminum gel plugging agent comprises the following components in percentage by mass:

8% of polyaluminum chloride, 2% of forced hydrolytic agent, 0.1% of polyacrylamide, 1% of chromium crosslinking agent, 0.15% of organic acid and the balance of water.

4. The composite aluminum gel plugging agent of claim 1, wherein the basicity suitable for medium and low temperature reservoir temperatures of 70-90 ℃ is 80%, and the basicity suitable for high temperature reservoir temperatures >90 ℃ is 60%.

5. The composite aluminum gel plugging agent of claim 1, wherein the ionic degree of the cationic polyacrylamide is 5% -30%, and the molecular weight of the cationic polyacrylamide is 700-800 ten thousand.

6. The composite aluminum gel plugging agent of claim 1, wherein the chromium crosslinking agent is chromium acetate.

7. The composite aluminum gel plugging agent of claim 1, wherein said organic acid is citric acid.

8. The preparation method of the composite aluminum chloride plugging agent of claim 1, comprising the following steps:

(1) Preparing 1% of cationic polyacrylamide mother liquor, and fully stirring to completely dissolve the cationic polyacrylamide mother liquor;

(2) Adding a certain amount of polyaluminum chloride into water, uniformly stirring to completely dissolve the polyaluminum chloride, sequentially adding a forced hydrolyzing agent and a chromium crosslinking agent, and uniformly stirring; finally, adding a certain amount of cationic polymer mother liquor and the balance of water, and uniformly stirring;

(3) And (3) sealing the materials obtained in the step (2), and aging the materials at different oil reservoir temperatures respectively to obtain the composite aluminum gel plugging agent.

9. The use of the composite aluminum gel plugging agent of claim 1 as a plugging agent for profile control plugging of low permeability fractured reservoirs.