阅读说明：本技术 仿生停钻承压堵漏钻井液用仿生聚乙烯醇堵漏凝胶 (Bionic polyvinyl alcohol plugging gel for bionic drill-stopping pressure-bearing plugging drilling fluid ) 是由 蒋官澄 董腾飞 孙金声 崔凯潇 贺垠博 杨丽丽 骆小虎 耿铁 罗健生 史赫 于 2021-08-26 设计创作，主要内容包括：本发明涉及油气井钻井领域,具体涉及仿生停钻承压堵漏钻井液用仿生聚乙烯醇堵漏凝胶。该聚乙烯醇堵漏凝胶含有经硼类交联剂交联的改性聚乙烯醇和增粘剂,其中,所述改性聚乙烯醇为二羟基苯甲醛改性的聚乙烯醇。本发明基于自然界中贻贝等生物展现出的水下粘附性能,通过在凝胶堵漏剂分子链上引入仿生强粘附基团,来提高凝胶堵漏剂在水润湿环境下粘附桥接堵漏剂和裂缝壁面的能力,有效避免堵漏凝胶被地层水或钻井液冲散、冲垮,提高有机凝胶滞留能力,改善堵漏效果。(The invention relates to the field of oil and gas well drilling, in particular to bionic polyvinyl alcohol plugging gel for bionic drill-stopping pressure-bearing plugging drilling fluid. The polyvinyl alcohol plugging gel contains modified polyvinyl alcohol crosslinked by a boron crosslinking agent and a tackifier, wherein the modified polyvinyl alcohol is polyvinyl alcohol modified by dihydroxybenzaldehyde. Based on the underwater adhesion performance exhibited by organisms such as mussels in nature, the bionic strong adhesion group is introduced into the molecular chain of the gel plugging agent, so that the capability of the gel plugging agent in adhering and bridging the plugging agent and the crack wall surface in a water-wet environment is improved, the leaking stoppage gel is effectively prevented from being dispersed and broken by formation water or drilling fluid, the retention capability of the organic gel is improved, and the plugging effect is improved.)

1. A bionic polyvinyl alcohol leakage stoppage gel is characterized by comprising modified polyvinyl alcohol crosslinked by a boron crosslinking agent and a tackifier, wherein the modified polyvinyl alcohol is polyvinyl alcohol modified by dihydroxybenzaldehyde.

2. The bionic polyvinyl alcohol leaking stoppage gel as claimed in claim 1, wherein the dosage weight ratio of the modified polyvinyl alcohol to the tackifier is 1: 0.01 to 0.8, preferably 1: 0.1-0.5.

3. The bionic polyvinyl alcohol leakage-stopping gel according to claim 1 or 2, wherein the content of the modified group provided by the dihydroxybenzaldehyde on the modified polyvinyl alcohol is 5-40 wt%.

4. The bionic polyvinyl alcohol leaking stoppage gel as claimed in any one of claims 1 to 3, wherein the dosage weight ratio of the modified polyvinyl alcohol to the boron crosslinking agent is 1: 0.01 to 0.8, preferably 1: 0.1-0.5.

5. The bionic polyvinyl alcohol leakage blocking gel according to any one of claims 1 to 4, wherein the tackifier is sodium carboxymethyl cellulose and/or low-viscosity polyanionic cellulose.

6. A preparation method of bionic polyvinyl alcohol plugging gel is characterized by comprising the following steps:

(1) modifying polyvinyl alcohol by using dihydroxybenzaldehyde to obtain modified polyvinyl alcohol;

(2) and (2) carrying out a crosslinking reaction on the modified polyvinyl alcohol and the tackifier in an aqueous solvent in the presence of a boron crosslinking agent.

7. The method of claim 6, wherein the modified polyvinyl alcohol and the tackifier are used in a weight ratio of 1: 0.01 to 0.8, preferably 1: 0.1-0.5;

preferably, the content of the modified group provided by the dihydroxybenzaldehyde on the modified polyvinyl alcohol is 5-40 wt%;

preferably, the dosage weight ratio of the modified polyvinyl alcohol to the boron crosslinking agent is 1: 0.01 to 0.8, preferably 1: 0.1-0.5;

preferably, the viscosifier is sodium carboxymethyl cellulose and/or a low viscosity polyanionic cellulose.

8. The bionic polyvinyl alcohol plugging gel prepared by the method of claim 6 or 7.

9. The use of the biomimetic polyvinyl alcohol lost circulation gel of claims 1-5 and 8 as a lost circulation agent in drilling fluids.

10. A water-based drilling fluid containing the biomimetic polyvinyl alcohol plugging gel of claims 1-5 and 8 as a plugging agent.

11. Use of the water-based drilling fluid of claim 10 in oil and gas drilling.

Technical Field

The invention relates to the field of oil and gas well drilling, in particular to bionic polyvinyl alcohol plugging gel for bionic drill-stopping pressure-bearing plugging drilling fluid.

Background

In geological drilling, due to the existence of various natural leakage passages such as macropores, large cracks, large karst caves or a combination thereof in underground strata, when drilling the strata containing the leakage passages, working fluid such as drilling fluid inevitably enters the deep part of the strata, and a large amount of expensive drilling fluid is lost. The serious harm of the well leakage is that the leakage can cause the liquid level of a drilling fluid column in a shaft to be reduced, so that the drilling fluid column meets the requirement of supporting the underground mechanical balance, underground complex accidents such as well wall collapse, overflow, kick, blowout and the like are caused, even the well hole is scrapped, and the safety of a well site and workers is threatened. Therefore, how to prevent and control lost circulation and avoid the occurrence of lost circulation hazards is an important research topic for drilling fluid engineers.

The method for treating the malignant leakage mainly comprises a bridging material leakage stopping method, an organic gel leakage stopping method, a cement leakage stopping method, a leakage stopping tool leakage stopping method and the like. The bridging material plugging method is characterized in that a certain concentration of plugging material is added into base slurry to form suspended plugging slurry, the plugging slurry enters a leakage passage through circulation, and bridging plugging materials such as walnut shells, peanut shells and the like are bridged and accumulated at the narrow part of the leakage passage to realize retention, so that the size of the leakage passage is reduced, and finally complete plugging is realized. The bridging lost circulation material has the advantages of high particle strength and wide material size source, but because inert accumulation is adopted among particles, the accumulation structure is easy to loosen when the pressure fluctuates, so that secondary leakage is caused; the cement leakage stoppage method is a leakage stoppage method for plugging a leakage passage by using a cement inorganic cementing material, is usually used as a final selection method for leakage stoppage construction, and has the effect of fully plugging the leakage passage, but has the defects of long waiting setting time, need of drilling a cement plug and the like, so that the cost of leakage stoppage time is increased; the plugging tool method is to mechanically seal a leakage channel by using a mechanical tool such as an expansion pipe, and the success of the method depends on the reliability of the tool and is less in application; the organogel plugging method is also called chemical gel plugging method, and generally utilizes the mode of molecular crosslinking, self-assembly and the like among chemical substances to realize the conversion from a freely flowing dilute solution into a thick fluid or a crosslinking body with poor fluidity, and the thick fluid or the crosslinking body is filled, blocked and retained in a leakage channel to block the leakage of the drilling fluid. The organic gel is usually rechecked with a bridging plugging material, so that the retention probability of the glue solution before gelling is improved by virtue of the bridging capacity of the bridging material, and the situation that the glue solution flows to the deep part of a leaking layer and cannot form effective plugging at the position close to the well wall is prevented. The currently applied organogel plugging agent types comprise polypropylene glycol gel, polyacrylamide gel, hydrolyzed polyacrylonitrile thick slurry and the like, and compared with other plugging methods, the organogel plugging agent has the advantages of adjustable gelling time and self-adaption of the size of a leaking layer, and has better application prospect. However, certain disadvantages are also exposed in the application process of the current plugging gel, and secondary leakage occurs after the partial plugging gel is plugged, which is mainly because although a reliable cross-linked structure is formed between gel bodies, the connection between the gel and a bridging material, and between the gel and the inner wall of a crack or a pore is poor, so that a residual leakage space exists between the gel and a leakage channel, and the gel bodies move under the influence of formation water scouring and pressure fluctuation in a shaft, so that the re-leakage is caused. Therefore, how to improve the connection strength between the organogel and the compound bridging material and the inner wall of the leakage passage and enhance the adhesive capacity of the leakage stoppage gel is an important way for improving the leakage stoppage effect of the organogel.

Disclosure of Invention

The invention aims to combine the bionics principle, imitate the marine organism mussel mucus to have the advantage of strong adhesion characteristic underwater, introduce strong adhesion group in the organogel structure, strengthen the adhesion ability of organogel, improve its anti-impact thin and anti-pressure fluctuation ability in the leakage passage, reduce the emergence of the secondary leakage, in order to achieve the above-mentioned goal, the invention provides a bionical polyvinyl alcohol plugging gel on the one hand, the polyvinyl alcohol plugging gel contains modified polyvinyl alcohol and tackifier cross-linked by boron cross-linking agent, wherein, said modified polyvinyl alcohol is polyvinyl alcohol modified by dihydroxybenzaldehyde.

The second aspect of the invention provides a preparation method of bionic polyvinyl alcohol plugging gel, which comprises the following steps:

(1) modifying polyvinyl alcohol by using dihydroxybenzaldehyde to obtain modified polyvinyl alcohol;

(2) and (2) carrying out a crosslinking reaction on the modified polyvinyl alcohol and the tackifier in an aqueous solvent in the presence of a boron crosslinking agent.

The third aspect of the invention provides the bionic polyvinyl alcohol plugging gel prepared by the method.

The fourth aspect of the invention provides the application of the bionic polyvinyl alcohol plugging gel as a plugging agent in drilling fluid.

The fifth aspect of the invention provides a water-based drilling fluid containing the bionic polyvinyl alcohol plugging gel as a plugging agent.

In a sixth aspect the present invention provides the use of the above water-based drilling fluid in oil and gas drilling.

Based on the underwater adhesion performance exhibited by organisms such as mussels in nature, the bionic strong adhesion group is introduced into the molecular chain of the gel plugging agent, so that the capability of the gel plugging agent in adhering and bridging the plugging agent and the crack wall surface in a water-wet environment is improved, the leaking stoppage gel is effectively prevented from being dispersed and broken by formation water or drilling fluid, the retention capability of the organic gel is improved, and the plugging effect is improved.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a bionic polyvinyl alcohol plugging gel which contains modified polyvinyl alcohol crosslinked by a boron crosslinking agent and a tackifier, wherein the modified polyvinyl alcohol is polyvinyl alcohol modified by dihydroxybenzaldehyde.

Preferably, the weight ratio of the modified polyvinyl alcohol to the tackifier is 1: 0.01 to 0.8, preferably 1: 0.1 to 0.5, for example 1: 0.05-0.08, 1: 0.1-0.15, 1: 0.16-0.2, 1: 0.22-0.3, 1: 0.32-0.4, preferably 1: 0.05 to 0.15, or preferably 1: 0.15 to 0.3, or preferably 1: 0.2-0.4.

According to the present invention, the polyvinyl alcohol may be a polyvinyl alcohol having a certain degree of polymerization and a certain degree of hydrolysis (also understood as a degree of alcoholysis), and the present invention may be applied to polyvinyl alcohols having a wide range of degrees of polymerization and hydrolysis, preferably, the polyvinyl alcohol is a polyvinyl alcohol having a degree of polymerization of 500-3000, more preferably, a polyvinyl alcohol having a degree of polymerization of 1000-2500, and more preferably, a polyvinyl alcohol having a degree of polymerization of 1500-2000. Preferably, the polyvinyl alcohol has a degree of hydrolysis of 50 to 99%, preferably 60 to 90%, more preferably 70 to 85%. Specifically, the polyvinyl alcohol may be one or more of polyvinyl alcohol 17 to 88 (degree of hydrolysis 88%, degree of polymerization 1700), polyvinyl alcohol 17 to 78 (degree of hydrolysis 78%, degree of polymerization 1700), and the like.

Preferably, the modified polyvinyl alcohol has a content of the modified group provided by the dihydroxybenzaldehyde of 5 to 40% by weight. The dihydroxybenzaldehyde may be one or more of 2, 3-dihydroxybenzaldehyde, 3, 4-dihydroxybenzaldehyde, 2, 5-dihydroxybenzaldehyde, 2, 6-dihydroxybenzaldehyde, 3, 5-dihydroxybenzaldehyde, etc., preferably 3, 4-dihydroxybenzaldehyde.

Preferably, the dosage weight ratio of the modified polyvinyl alcohol to the boron crosslinking agent is 1: 0.01 to 0.8, preferably 1: 0.1 to 0.5, for example 1: 0.05-0.08, 1: 0.1-0.15, 1: 0.16-0.2, 1: 0.22-0.3, 1: 0.32-0.4, preferably 1: 0.05 to 0.15, or preferably 1: 0.15 to 0.3, or preferably 1: 0.2-0.4.

Preferably, the boron crosslinking agent is borax and/or boric acid.

Preferably, the viscosifier is sodium carboxymethyl cellulose and/or a low viscosity polyanionic cellulose.

According to the invention, the viscosity of the bionic polyvinyl alcohol plugging gel is preferably 8-40 ten thousand mPa.s, preferably 10-30 ten thousand mPa.s, and more preferably 12-28 ten thousand mPa.s.

The second aspect of the invention provides a preparation method of bionic polyvinyl alcohol plugging gel, which comprises the following steps:

(1) modifying polyvinyl alcohol by using dihydroxybenzaldehyde to obtain modified polyvinyl alcohol;

(2) and (2) carrying out a crosslinking reaction on the modified polyvinyl alcohol and the tackifier in an aqueous solvent in the presence of a boron crosslinking agent.

Preferably, the weight ratio of the modified polyvinyl alcohol to the tackifier is 1: 0.01 to 0.8, preferably 1: 0.1 to 0.5, for example 1: 0.05-0.08, 1: 0.1-0.15, 1: 0.16-0.2, 1: 0.22-0.3, 1: 0.32-0.4, preferably 1: 0.05 to 0.15, or preferably 1: 0.15 to 0.3, or preferably 1: 0.2-0.4.

Preferably, the modified polyvinyl alcohol has a content of the modified group provided by the dihydroxybenzaldehyde of 5 to 40% by weight.

Preferably, the dosage weight ratio of the modified polyvinyl alcohol to the boron crosslinking agent is 1: 0.01 to 0.8, preferably 1: 0.1 to 0.5, for example 1: 0.05-0.08, 1: 0.1-0.15, 1: 0.16-0.2, 1: 0.22-0.3, 1: 0.32-0.4, preferably 1: 0.05 to 0.15, or preferably 1: 0.15 to 0.3, or preferably 1: 0.2-0.4.

Preferably, the viscosifier is sodium carboxymethyl cellulose and/or a low viscosity polyanionic cellulose.

According to the present invention, preferably, in step (1), the conditions for the modification include: the temperature is 50-95 deg.C, and the time is 40-240 min. Wherein, the modification process is only required to modify the polyvinyl alcohol by the dihydroxybenzaldehyde, and preferably, in the step (1), the modification process comprises the following steps: an aqueous solution containing polyvinyl alcohol (concentration may be, for example, 5 to 15 wt%) is prepared, the pH is adjusted to be acidic (pH may be 1 to 4, and may be adjusted by hydrochloric acid, sulfuric acid, or the like), then dihydroxybenzaldehyde is introduced to perform a contact reaction under protection of an inert gas such as nitrogen (reaction conditions may be, for example, 70 to 95 ℃ for, for example, 30 to 180min), then the pH is adjusted to be basic (pH may be, for example, 8 to 10, and may be adjusted by aqueous ammonia, sodium hydroxide solution, or potassium hydroxide solution), and the reaction is continued with stirring (reaction conditions may be, for example, 40 to 70 ℃ for, for example, 10 to 60 min). The reaction product may be added to water to precipitate the desired modified polyvinyl alcohol product.

According to the present invention, in step (2), the conditions of the crosslinking reaction preferably include: the temperature is 20-40 deg.C (e.g. 25-35 deg.C), the stirring rate is 1500-. In order to achieve the above object, preferably, in step (2), the crosslinking reaction process may include: an aqueous solution (concentration may be, for example, 2 to 6 wt%) containing the modified polyvinyl alcohol is provided, and a boron-based crosslinking agent is added and stirred to dissolve, and then a tackifier is introduced and stirred at high speed to prepare a high-viscosity gel.

The third aspect of the invention provides the bionic polyvinyl alcohol plugging gel prepared by the method.

According to the invention, the bionic polyvinyl alcohol plugging gel has higher pressure-bearing strength, for example, the pressure-bearing strength can reach more than 3MPa, preferably more than 4MPa, and particularly can reach 5-6.5 MPa. The viscosity can be adjusted in a wide range, and is preferably controlled to 10000-200000mPa.s, preferably 11000-180000mPa.s, such as 11000-55000mPa.s, 50000-65000mPa.s, 60000-78000mPa.s, 75000-85000mPa.s, 100000-120000mPa.s, 130000-150000mPa.s, 160000-180000 mPa.s.

The fourth aspect of the invention provides the application of the bionic polyvinyl alcohol plugging gel as a plugging agent in drilling fluid.

The fifth aspect of the invention provides a water-based drilling fluid containing the bionic polyvinyl alcohol plugging gel as a plugging agent.

In a sixth aspect the present invention provides the use of the above water-based drilling fluid in oil and gas drilling.

The bionic polyvinyl alcohol plugging gel provided by the invention has the following advantages: compared with the rubber before modification, the rubber has higher adhesive forming degree; the biocompatibility is good, and the environment is friendly; the high-viscosity cement has high adhesiveness and higher bonding strength with the wall surface of a crack, and is favorable for resisting pressure fluctuation in a shaft and formation water scouring.

According to the invention, by combining the bionics principle, the side group modification is carried out on the polyvinyl alcohol by utilizing the bionic adhesion group to form the bionic strong adhesion polyvinyl alcohol organogel plugging agent, so that the adhesion of the organogel to a leakage passage and a bridging plugging material is greatly improved, the plugging strength of a gel slug is enhanced, and the occurrence of secondary leakage is avoided.

The present invention will be described in detail below by way of examples.

Modified polyvinyl alcohol production example 1

(1) Heating 80g of 10 wt% polyvinyl alcohol 1788 aqueous solution in a water bath to 80 ℃, stirring at the speed of 100-150 r/min, and dropwise adding hydrochloric acid (the concentration of the hydrochloric acid is 10 wt%) by using a dropper to adjust the pH of the system to 1-2;

(2) under the protection of nitrogen, 4g of 36 weight percent 3, 4-dihydroxy benzaldehyde aqueous solution is dripped in about 30 min; continuously reacting for 0.5h, and cooling to 60 ℃; and (4) dropwise adding ammonia water to adjust the pH value of the system to 8-9, and continuously reacting for 30 min.

(3) Dropping the reaction liquid into a large amount of deionized water to obtain grey white precipitate, repeatedly washing the product to neutrality by using the deionized water, and washing unreacted 3, 4-dihydroxy benzaldehyde and redundant acid and alkali by using a large amount of deionized water.

(4) And (3) drying the product at 50-60 ℃ in vacuum for 24h, and crushing to obtain the modified polyvinyl alcohol m-PVA powder C1.

Modified polyvinyl alcohol production example 2

Modified polyvinyl alcohol m-PVA powder C2 was obtained according to the method described in preparation example 1, except that polyvinyl alcohol 1778 was used in place of polyvinyl alcohol 1788 in an equal weight.

Example 1

Adding 4 wt% of the modified polyvinyl alcohol m-PVA powder C1 into 400mL of distilled water, and stirring for 10min at the speed of 150-200 r/min until the m-PVA powder is completely dissolved. Then 0.3 weight percent of cross-linking agent borax is added, the mixture is stirred for 3min at room temperature of 200-250 r/min until the mixture is completely dissolved, then 0.5 weight percent of tackifier sodium carboxymethyl cellulose (purchased from Athia technologies, Inc.) is added, and the mixture is stirred for 10-15min at room temperature of 2000-2500r/min, thus preparing the bionic strong-adhesion polyvinyl alcohol organogel plugging B1.

Examples 2 to 6

The method of embodiment 1, except that:

example 2: the dosage of the cross-linking agent borax is 0.2 weight percent, so as to prepare the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B2.

Example 3: the dosage of the cross-linking agent borax is 0.5 weight percent, so as to prepare the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B3.

Example 4: the dosage of the cross-linking agent borax is 0.7 weight percent, so as to prepare the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B4.

Example 5: the dosage of the cross-linking agent borax is 1 weight percent, so as to prepare the bionic strong-adhesion polyvinyl alcohol organogel plugging B5.

Example 6: the dosage of the cross-linking agent borax is 1.5 weight percent, so as to prepare the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B6.

Examples 7 to 9

The method of embodiment 5 except that:

example 7: the dosage of the tackifier sodium carboxymethyl cellulose is 0.3 weight percent, so that the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B7 is prepared.

Example 8: the dosage of the tackifier sodium carboxymethyl cellulose is 0.7 weight percent, so that the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B8 is prepared.

Example 9: the dosage of the tackifier sodium carboxymethyl cellulose is 1 weight percent, so that the bionic strong-adhesion polyvinyl alcohol organogel leak stopping B9 is prepared.

Example 10

According to the method described in the embodiment 5, except that the modified polyvinyl alcohol m-PVA powder C2 is adopted to replace the modified polyvinyl alcohol m-PVA powder C1, so as to prepare the bionic strong adhesion polyvinyl alcohol organogel plugging B10.

Comparative example 1

The method of example 1 was followed except that unmodified polyvinyl alcohol 1788 was used in equal amounts to replace the highly adherent group modified polyvinyl alcohol 1788 to prepare unmodified polyvinyl alcohol organogel lost circulation a 1.

Test example 1

The results of the tests of the plugging performance and the gel viscosity of the plugging agent are shown in the following table, wherein the gel viscosity is measured at room temperature by using a DV-1 type rotational viscometer, and the plugging performance is measured by using the following devices and methods:

the modified 71-type high-temperature high-pressure filtration loss instrument has the temperature control range of room temperature to 180 ℃ and the pressure range of 0MPa to 7 MPa; the leakage layer simulation medium of the instrument is an artificial sandstone core fracture mould with different openings, the thickness of the artificial sandstone core fracture mould is 50mm, and the sizes of the openings in the middle of the fracture are respectively 0.5mm, 1mm and 3 mm. The organic gel plugging slurry can pass through a crack die under the action of pressure and is extruded from a lower valve rod of an instrument, the stronger the adhesion capacity of the organic gel and the larger the gelling viscosity, the higher the strength of a plugging layer is, the smaller the extrusion proportion of the gel is, and the higher the pressure bearing is. The artificial sandstone mould is soaked in clear water for 24 hours in advance, so that the surface of the artificial sandstone mould is in a water-wet state.

Evaluation step:

(1) and (4) adding a steel crack mould into the bottom of the test cup to form a test assembly.

(2) Preparing 400mL of organic gel static leaking stoppage slurry, weighing the mass of the organic gel static leaking stoppage slurry by using a balance, then injecting the static leaking stoppage slurry into a test cup, closing a cock on the test cup, connecting a pressure pipeline, and standing for 5 min.

(3) Pre-adding 0.5MPa into the test cup, closing the upper and lower valve rods, heating the test cup to make the instrument reach the specified temperature, standing for the specified time, and waiting for the organic gel to stand still to block the leakage and gelatinize.

(4) And opening the upper valve rod, uniformly pressurizing the test cup, and enabling the pressure to reach the set pressure within 30 s.

(5) And under the set temperature and pressure, opening the lower valve rod, placing the beaker and the balance, opening the upper valve rod, opening the air source to add the pressure of 1.0MPa into the test cup, and testing the instantaneous extrusion quality of the organogel under the pressure of 1.0 MPa. Because the polymer gel has higher gel forming strength but still has flowing deformation under high temperature and high pressure, the polymer gel can be extruded from the valve stem, and the mass of the extruded gel is recorded by a balance. If the test slurry is completely extruded, replacing the crack die or changing the test conditions, and carrying out the test again; if the test slurry is extruded by only a part of mass, the plugging effect of the organogel plugging material is represented, the test slurry is maintained for 30min, the accumulated extrusion mass is recorded, and the extrusion mass proportion is calculated.

(6) And if the organic gel is not completely extruded, continuously pressurizing the test cup through an air source, pressurizing for 0.5MPa every time, maintaining for 5min, recording the accumulated extruded quality of the organic gel, and simultaneously testing the pressure bearing capacity of the blocking layer until the pressure reaches the upper pressure bearing limit of an instrument or the air source or the plugging slurry is completely extruded.

(7) And after the test is finished, releasing pressure and cooling the instrument, taking out the crack mold, and observing the distribution state and the plugging characteristics of the organic gel static plugging agent on the surface and the inner wall of the crack.

TABLE 1

Gel plugging agent	Extrusion mass fraction of%	Bearing pressure, MPa	Viscosity, mPas
				A1	54.3％	1.5MPa	11350
B1	25.6％	4.5MPa	76350
				B2	30.7％	3.5MPa	65430
B3	21.3％	4.5MPa	83560
				B4	15.6％	5.0MPa	118630
B5	10.7％	6.0MPa	142030
				B6	5.6％	6.5MPa	170230
B7	27.1％	4.0MPa	54320
				B8	21.7％	4.5MPa	93680
B9	9.8％	5.5MPa	138690
				B10	27.6％	4.5MPa	62320

As can be seen from the table above, the system A1 is a conventional polyvinyl alcohol organogel plugging system, and although the plugging system has a certain plugging effect on artificial cracks wetted by 2mm of water after gelling, the extrusion proportion is large after pressurization, and the pressure bearing is lower than 3 MPa. The organogel plugging system B1 modified by the polyvinyl alcohol with the bionic adhesion group has high crack wall surface connection force and large moving friction resistance due to the strong adhesion effect of the gel, so the pressure bearing is higher and reaches 5MPa, and the extrusion proportion is less. As can be seen from the organogel plugging systems B2-B6 under different cross-linking agent addition amounts, the viscosity of the system is gradually increased along with the increase of the cross-linking agent addition amount, the extrusion proportion is gradually reduced, the pressure bearing is also gradually improved, and the highest pressure bearing can be 6.0 MPa. As can be seen from the organogel plugging system B7-B9 with different tackifier contents, the viscosity of the system can be obviously increased along with the increase of the tackifier content, and meanwhile, the extrusion proportion is reduced and the pressure-bearing capacity is improved. For an organogel plugging system B10 obtained by using polyvinyl alcohol with lower hydrolysis degree, the internal hydroxyl content is reduced by the low hydrolysis degree, so that the absorption groups are reduced, the viscosity is slightly reduced, the extrusion proportion is slightly increased, but the pressure bearing capacity can still reach 4.5MPa, and the good pressure bearing effect is achieved.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.