Gel valve capable of breaking gel automatically as well as preparation method and application of gel valve

Abstract

The invention belongs to the technical field of unbalanced drilling, and discloses a gel valve capable of breaking gel automatically and a preparation method and application thereof. The gel valve capable of breaking gel automatically is prepared from the following raw materials in percentage by mass: 8%-15% of a monomer, 1%-2% of a degradable cross-linking agent, 0.01%-0.015% of an initiator, 0.2%-0.5% of a dispersing agent and 82.485%-90.79% of water, wherein the degradable cross-linking agent is derived from a reaction product obtained by reacting anhydrous strong acid, poly (ethylene glycol) methacrylate and methoxylated benzaldehyde. The gel-forming agent is in a liquid state before gel forming, is easy to pump and inject, good in gel-forming performance and stable in strength, can replace a casing valve and pack bottom hole pressure, has more suitable gel-forming time and gel-breaking time, and is wider in adaptability. After the operation is finished, the gel valve can gradually hydrolyze the self-made degradable cross-linking agent through autocatalysis, and mechanical gel breaking or gel breaking by adding a gel breaker is not needed.

Description

Technical Field

[0001] The invention belongs to the technical field of underbalanced drilling, and in particular relates to a self-breaking jelly valve and a preparation method thereof, and application thereof in pressure control of underbalanced drilling. Background Art

[0002] With the in-depth research and promotion of underbalanced drilling technology, the requirements for this technology are getting higher and higher at home and abroad. How to achieve full-process underbalanced drilling operations has gradually become a research hotspot. The core of full-process underbalanced drilling technology lies in pressure control. In terms of pressure control methods, the commonly used technologies are downhole casing valve technology and gel valve technology. Downhole casing valve technology has high cost and low safety factor; while gel valve technology has low cost and good isolation effect, which can effectively replace casing valves to achieve full-process underbalanced drilling.

[0003] The gel valve technology refers to the technology of injecting gel fluid with ultra-high viscosity into the wellbore, and the gel fluid gels under certain pressure and temperature in the wellbore to form a gel plug, thereby isolating the wellbore. The gel plug has certain strength and pressure resistance, which can play an isolation role; it also has certain adhesion and recovery, forming a static seal with the casing and a dynamic seal with the drilling and completion string. The viscosity of the gel is used to achieve a certain pressure difference resistance, and it remains stationary in the wellbore, that is, the "valve" is fixed; the solid mechanical properties of the gel are used to isolate and seal the oil and gas in the wellbore, that is, the "valve" is sealed; the viscoelasticity of the gel is used to achieve smooth penetration of the string and its own recovery, that is, the "valve" is opened and closed; the gel-breakable properties of the gel are used to achieve gel-breakage and return to the ground after the operation is completed, that is, the "valve" is unlocked. The commonly used gel valve at present is a gel formed by polymers and cross-linking agents. After the operation is completed, a large amount of gel-breaking agents need to be added to break the gel. The addition of gel-breaking agents will increase the construction process on the one hand. In addition, due to the insufficient contact between the degelling agent and the gel valve, the gel is not completely broken and is difficult to return. Third, degelling agents are mostly strong oxidants, which will cause certain corrosion to the tubing. For example, Chinese patent application CN112480888A discloses a downhole gel valve and its preparation method. After the construction of this method is completed, ammonium persulfate solution needs to be injected into the well for gel breaking. The operation is cumbersome and the process is complicated, and self-degradation cannot be achieved; Chinese patent application CN113185656A discloses a temperature-responsive self-degradable temporary plugging agent and a well repair method, which can gel at 55-85°C and the gel breaking time is 72-95h. However, as the temperature increases, the gelling time gradually increases, while the gel breaking time shortens, which cannot meet the needs of long-term downhole operations. Summary of the invention

[0004] The purpose of the present invention is to provide a self-breaking jelly valve and its preparation method and application in underbalanced drilling pressure control. The self-breaking jelly valve provided by the present invention is in liquid state before gelation, has low viscosity, good fluidity, is easy to pump, has good gelation performance, stable strength, can replace casing valve, isolate bottom hole pressure, and has more suitable gelation time and gel breaking time, and has wider adaptability. After the operation is completed, the jelly valve can gradually hydrolyze the self-made degradable cross-linking agent through self-catalysis, resulting in the breaking of cross-linking points, and the three-dimensional network structure degrades low-viscosity linear polymers, without the need for mechanical gel breaking or adding a gel breaker to break the gel.

[0005] One of the purposes of the present invention is to provide a self-destructing jelly valve, comprising the following raw materials in percentage by mass: 8%-15% of an olefin-containing monomer, 1%-2% of a degradable cross-linking agent, 0.01%-0.015% of an initiator, 0.2%-0.5% of a dispersant, and 82.485%-90.79% of water;

[0006] Wherein, the degradable cross-linking agent is derived from the reaction product obtained by reacting anhydrous strong acid, poly(ethylene glycol) methacrylate as shown in formula (1) and methoxylated benzaldehyde as shown in formula (2);

[0007]

[0008] In formula (2), the position indicated by 1 and / or the position indicated by 2 is substituted by a methoxy group.

[0009] In a preferred embodiment of the present invention, the self-destructive jelly valve comprises the following raw materials in percentage by mass: 10%-13% of olefin-containing monomers, 1.5%-2% of degradable cross-linking agents, 0.012%-0.014% of initiators, 0.35%-0.45% of dispersants, and 84.536%-88.138% of water.

[0010] According to the present invention, the methoxylated benzaldehyde is selected from 4-methoxybenzaldehyde and / or 3-methoxybenzaldehyde, more preferably 4-methoxybenzaldehyde.

[0011] In a preferred embodiment of the present invention, the number average molecular weight of the poly(ethylene glycol) segment in the poly(ethylene glycol) methacrylate is 200-600; preferably, the number average molecular weight of the poly(ethylene glycol) segment in the poly(ethylene glycol) methacrylate is at least one of 200, 300, 400, and 600, preferably at least one of 200 and 300; most preferably 200.

[0012] In the present invention, "poly(ethylene glycol)~" also refers to "polyethylene glycol~", for example, a poly(ethylene glycol) chain segment also refers to a polyethylene glycol chain segment.

[0013] According to the present invention, the role of the anhydrous strong acid is to catalyze the reaction between poly(ethylene glycol) methacrylate and methoxylated benzaldehyde, i.e., a catalyst. There are many types of the anhydrous strong acid to be selected. In a preferred embodiment of the present invention, the anhydrous strong acid is selected from at least one of p-toluenesulfonic acid and trifluoromethanesulfonic acid.

[0014] In a more preferred embodiment of the present invention, the structural formula of the degradable cross-linking agent is as shown in formula (3):

[0015]

[0016] According to the present invention, the preparation method of the degradable cross-linking agent includes but is not limited to the preparation method of the present invention. Preferably, the preparation method of the degradable cross-linking agent comprises the following steps: mixing anhydrous strong acid, poly(ethylene glycol) methacrylate, methoxylated benzaldehyde, and anhydrous tetrahydrofuran, and performing a cross-linking reaction, preferably further comprising filtering, removing the solvent by reduced pressure distillation, and purifying by silica gel column chromatography after the cross-linking reaction to obtain the degradable cross-linking agent.

[0017] According to the present invention, the mass ratio of anhydrous strong acid, poly(ethylene glycol) methacrylate, and methoxylated benzaldehyde can be selected within a wide range. In a more preferred embodiment of the present invention, the mass ratio of anhydrous strong acid, poly(ethylene glycol) methacrylate, and methoxylated benzaldehyde is 1:(15-25):(4-10), preferably 1:(15-20):(5-8).

[0018] According to the present invention, the conditions of the cross-linking reaction can be selected within a wide range. In a more preferred embodiment of the present invention, the temperature of the cross-linking reaction is 0-10°C, preferably 0-5°C; and / or the time of the cross-linking reaction is 5-7h, preferably 5.5-6h.

[0019] According to the present invention, the mass ratio of the poly(ethylene glycol) methacrylate to anhydrous tetrahydrofuran can be selected within a wide range. In a more preferred embodiment of the present invention, the mass ratio of the poly(ethylene glycol) methacrylate to anhydrous tetrahydrofuran is (2-3):1.

[0020] As an example, the preparation method of the degradable crosslinking agent RJ-2 preferably comprises the following steps:

[0021] p-Toluenesulfonic acid monohydrate, poly(ethylene glycol) (Mn: 200) methacrylate, 4-methoxybenzaldehyde and anhydrous tetrahydrofuran were mixed, and cross-linked, filtered, the solvent was removed by vacuum distillation, and purified by silica gel column chromatography to obtain a degradable cross-linking agent RJ-2.

[0022] In the above technical scheme, the mass ratio of p-toluenesulfonic acid monohydrate, poly(ethylene glycol) methacrylate and 4-methoxybenzaldehyde is preferably 1:18:7; the mass ratio of poly(ethylene glycol) methacrylate and anhydrous tetrahydrofuran is preferably 18:8; the temperature of the cross-linking reaction is preferably 0-10°C, more preferably 0-5°C; the time of the cross-linking reaction is preferably 5-7h, more preferably 5.5-6h; the eluent for the silica gel column chromatography purification is preferably ethyl acetate: hexane = 1:9; the reduced pressure distillation temperature is preferably 40-55°C, more preferably 45-50°C. The present invention does not specifically limit the filtering process, and the filtering process well known in the art can be used.

[0023] The preparation of cross-linking agent RJ-2 includes but is not limited to the method described in the embodiments of the present invention. The specific preparation method of the cross-linking agent RJ-2 is as follows: 1.0 g of p-toluenesulfonic acid monohydrate is dissolved in a round-bottom flask containing anhydrous tetrahydrofuran, then an appropriate amount of molecular sieves is added, followed by adding 18.0 g of poly (ethylene glycol) methacrylate and 7.0 g of 4-methoxybenzaldehyde to mix evenly, and the round-bottom flask is placed in ice water to react for several hours. The molecular sieves are removed by filtration and the solvent is removed by vacuum distillation. After removing the solvent, the transparent liquid residue is purified by silica gel column chromatography to obtain cross-linking agent RJ-2.

[0024] The cross-linking agent in the present invention can cross-link the linear olefin-containing monomers to form a three-dimensional network structure, thereby enhancing the strength and adhesion of the jelly valve.

[0025] In a preferred embodiment of the present invention, the olefinic monomer is selected from one or more of acrylamide, methyl methacrylate, hydroxyethyl methacrylate, ethyl acrylate, and vinyl acetate.

[0026] According to the present invention, the initiator can be selected from a wide range. In a preferred embodiment of the present invention, the initiator is selected from one or more of ammonium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate / sodium bisulfite and azobisisobutyramidine hydrochloride.

[0027] According to the present invention, the dispersant can be selected from a wide range. In a preferred embodiment of the present invention, the dispersant is selected from one or more of sodium dodecylbenzene sulfonate, dodecylphenol polyoxyethylene ether, Tween 40, Tween 60 and Tween 80.

[0028] According to the present invention, the self-breaking jelly valve can self-degrade and break the jelly. Preferably, the self-breaking time is 4-12 days, preferably 5-10 days, and more preferably 7-8 days.

[0029] According to the present invention, the time for the raw materials of the self-destructible jelly valve to gel is 1-5 hours, preferably 1-4 hours, and more preferably 2-3 hours.

[0030] In a preferred embodiment of the present invention, the self-destructing jelly valve is prepared by the following method: mixing the preparation raw materials including the olefinic monomer, the degradable cross-linking agent, the initiator, the dispersant and water to obtain a self-destructing jelly valve base liquid, and then gelling to obtain the self-destructing jelly valve;

[0031] Preferably, the gelation time is 1-5 h, preferably 1-4 h, more preferably 2-3 h.

[0032] The self-breaking gel valve of the present invention has excellent comprehensive performance in gelling and self-breaking time. Within the gelling time range, the raw materials of the self-breaking gel valve can be transported to the underground, and the transportation time of the raw materials of the self-breaking gel valve is reserved, which is more convenient for operation. If the gelling time is too short, gelling may occur during the transportation process or before reaching the target isolation area, which is not convenient for operation and cannot achieve the expected isolation effect. If the gelling time is too long, the construction efficiency is too low. The self-breaking time of the self-breaking gel valve of the present invention is more conducive to construction. Before the self-breaking gel begins, a suitable drilling pressure control time for underbalanced drilling is reserved. If the self-breaking time is too short, the isolation time may be insufficient, that is, the gel may be broken, and the pressure control effect during the construction process cannot be achieved. If the self-breaking time is too long, the construction efficiency is too low. More preferably, the raw material gelling time of the self-breaking jelly valve is 1-5h, preferably 1-4h, more preferably 2-3h; the self-breaking time is 4-12d, preferably 5-10d, more preferably 7-8d.

[0033] The present invention can change the rate of self-catalytic degradation of the gel valve by changing the type of monomer, the amount of monomer added, and the type of cross-linking agent to achieve regulation of the gelling time and the degradation time within the range of 60-80°C. The gel valve breaks the gel automatically after maintaining high strength (above 15MPa) for a period of time, thereby better meeting the needs of 60-80°C formation construction, solving the problems of complex construction procedures of the existing gel valve system and possible corrosion caused by the gel breaker, achieving safe operation, and causing no pollution to the underground environment.

[0034] According to the present invention, preferably, the self-breaking jelly valve of the present invention has a breakthrough pressure of more than 15 MPa and has a high pressure-bearing performance.

[0035] According to the present invention, the self-degradation time of the self-degradable jelly valve, i.e., the self-degradation time, refers to the time from the gelation of the self-degradable jelly valve to the start of self-degradation. Before the start of degradation, the strength of the self-degradable jelly valve remains stable.

[0036] According to the present invention, the self-degradable jelly valve generally completes the self-degradation within 1-2 hours after starting the self-degradation.

[0037] As mentioned above, the self-breaking time refers to the time when the gel valve starts to break, and the breakthrough pressure starts to decrease from the time when the gel valve starts to break.

[0038] The second aspect of the present invention is to provide a method for preparing the self-destructing jelly valve described in the first aspect, comprising mixing the preparation raw materials including the olefin-containing monomer, the degradable cross-linking agent, the initiator, the dispersant and water to obtain a self-destructing jelly valve base liquid, and then gelling to obtain the self-destructing jelly valve; preferably,

[0039] The gelling time is 1-5 hours, preferably 1-4 hours, more preferably 2-3 hours; and / or the gelling temperature is 60-80°C.

[0040] Unless otherwise specified, the present invention has no special requirements on the sources of the raw materials used in the preparation, and commercially available products known to those skilled in the art can be used.

[0041] The self-destructible jelly valve provided by the present invention comprises 8% to 15% by mass of olefin-containing monomers, preferably 10% to 13% by mass.

[0042] In the present invention, the olefinic monomer is preferably one or more of acrylamide, methyl methacrylate, hydroxyethyl methacrylate, ethyl acrylate, and vinyl acetate, and more preferably acrylamide. When there are multiple monomers, the present invention has no special restrictions on the ratio of different types of monomers, and any ratio is acceptable.

[0043] The present invention preferably achieves controllable regulation of the gelling and self-breaking rates of the gel valve by adjusting the type and amount of monomers, without adding an external breaker or catalyst, and can achieve self-breaking by self-catalytic degradation of the cross-linking agent, thereby reducing the construction process.

[0044] The self-destructible jelly valve provided by the present invention comprises 0.01%-0.015% by mass of initiator, preferably 0.012%-0.014% by mass.

[0045] In the present invention, the initiator is preferably one or more of ammonium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate / sodium bisulfite and azobisisobutylamidine hydrochloride, more preferably ammonium persulfate. When there are multiple initiators, the present invention has no special restrictions on the ratio of different types of initiators, and any ratio is acceptable.

[0046] The self-destructible jelly valve provided by the present invention comprises 1%-2% by mass of a degradable cross-linking agent, preferably 1.5%-2% by mass.

[0047] The degradable cross-linking agent in the present invention has been described in detail in the part of the self-destructible jelly valve in the first aspect, and will not be described again here.

[0048] The self-destructible jelly valve provided by the present invention comprises 0.2%-0.5% by mass of a dispersant, preferably 0.35%-0.45%, for example 0.4%.

[0049] In the present invention, the dispersant is preferably one or more of sodium dodecylbenzene sulfonate, polyoxyethylene dodecylphenol, Tween 40, Tween 60 and Tween 80, more preferably sodium dodecylbenzene sulfonate. When there are multiple types of dispersants, the present invention has no special restrictions on the ratio of different types of dispersants, and any ratio is acceptable.

[0050] The crosslinking agent RJ-2 in the present invention is oil-soluble and difficult to dissolve in water. After adding the dispersant, the crosslinking agent can be evenly dispersed in water, so that the gelling reaction proceeds smoothly and the obtained jelly valve has a uniform texture.

[0051] The self-breaking jelly valve provided by the present invention comprises residual water.

[0052] In the present invention, olefin-containing monomers, initiators, degradable cross-linking agents, dispersants and water are mixed. The mixing is preferably carried out under stirring conditions. The present invention has no special restrictions on the time and power of the stirring. The materials can be mixed evenly according to actual conditions.

[0053] The third aspect of the present invention is to provide a method for controlling pressure in drilling, comprising the following steps:

[0054] According to the raw materials and proportions of the self-destructing jelly valve, the raw materials including the olefinic monomer, the degradable cross-linking agent, the initiator, the dispersant and water are mixed to obtain a self-destructing jelly valve base liquid;

[0055] The self-destructing jelly valve base liquid is transported downhole, and the self-destructing jelly valve base liquid is gelled at the temperature of the reservoir section to form a self-destructing jelly valve, that is, the base liquid is gelled at the temperature of the reservoir section to seal the reservoir section;

[0056] When the self-degradation and gel-breaking time of the self-degrading jelly valve is reached, the self-degrading jelly valve starts to self-degrade, and the resulting gel-breaking liquid is returned to the ground, that is, the construction is carried out during the time before the self-degrading jelly valve starts to degrade, and after the construction is completed, the self-degrading jelly valve self-catalytically degrades, and the resulting gel-breaking liquid is returned to the ground;

[0057] The self-breaking jelly valve is the self-breaking jelly valve described in the first aspect or the self-breaking jelly valve prepared by the preparation method described in the second aspect.

[0058] In a preferred embodiment of the present invention, the reservoir section temperature is 60-80° C.; and / or the gelation time is 1-5 h, preferably 1-4 h, more preferably 2-3 h.

[0059] In a preferred embodiment of the present invention, the time for the self-breaking jelly valve to start self-breaking is 4-12 days, preferably 5-10 days, and more preferably 7-8 days.

[0060] The fourth aspect of the present invention is to provide an application of the self-destructing jelly valve described in the first aspect, the self-destructing jelly valve prepared by the preparation method described in the second aspect, or the drilling pressure control method described in the third aspect in the field of underbalanced drilling technology.

[0061] Before the self-breaking gel raw material of the present invention is formed into gel, the base liquid viscosity is low and it is easy to pump. After being pumped into the formation, the monomer undergoes a free radical polymerization reaction to form a gel with a certain strength, and the strength of the gel can be maintained for a period of time. As time goes by, the polymer gradually hydrolyzes under the formation conditions to produce acidic substances, and the homemade cross-linking agent hydrolyzes under acidic conditions, resulting in the breaking of cross-linking points, and the three-dimensional network structure of the gel collapses to become linear small molecules, which is conducive to returning to the ground.

[0062] As mentioned above, the self-destructive jelly valve provided by the present invention gels under the action of formation temperature (60-80°C, i.e., downhole temperature) and maintains strength and viscosity for a period of time (before self-destruction begins). After gelling, the self-destructive jelly valve is a viscoelastic solid with a three-dimensional network structure. As time goes by, when the self-degradation and destructing time of the self-destructive jelly valve is reached, the jelly valve gradually hydrolyzes the degradable cross-linking agent through self-catalysis, resulting in the breaking of the cross-linking points, and the three-dimensional network structure is degraded into a small molecular linear structure, thereby realizing the self-destruction of the jelly valve. The present invention can change the rate of self-catalytic degradation of the gel valve by changing the type and amount of monomers and the type of cross-linking agent to achieve regulation of the gel time and degradation time within the range of 60-80°C (gel time is 1-5h, preferably 1-4h, more preferably 2-3h; self-break gel time is 4-12d, preferably 5-10d, more preferably 7-8d), which is more conducive to selecting different self-break gel valve formulas according to different construction conditions and progress requirements, meeting construction requirements, and having wider adaptability. The gel valve of the present invention breaks gel by itself after maintaining high strength (above 15MPa) for a period of time, without mechanical breaking gel or adding a breaking agent to break gel or a degradation catalyst to break gel, better meeting the needs of 60-80°C formation construction, solving the problems of complex construction procedures of existing gel valve systems and possible corrosion of breaking agents, achieving safe operation, and no pollution to the underground environment.

[0063] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 The figure is a structural formula diagram of a preferred degradable cross-linking agent. DETAILED DESCRIPTION

[0065] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0066] Detection method:

[0067] 1. Detection method of breaking time:

[0068] Visual inspection method: Invert the reagent bottle during evaluation. When the colloid can flow, it is the gel breaking time of the gel valve.

[0069] 2. Testing method for pressure bearing performance of self-breaking jelly valve:

[0070] The pressure bearing performance of the prepared self-destructive jelly valve was tested by nitrogen reverse displacement experiment using a multifunctional core displacement device. First, a certain amount of jelly valve base liquid was prepared, and then the prepared base liquid was injected into the core using a horizontal flow pump. The core was then placed in a constant temperature oven to react into gel. The pressure bearing performance of the prepared self-destructive jelly valve was tested by nitrogen reverse displacement. The maximum reading of the pressure gauge was the breakthrough pressure of the self-destructive jelly valve.

[0071] In the following examples, unless otherwise specified, all the devices and raw materials used are conventional commercially available products.

[0072] Example 1

[0073] In a 250 mL round-bottom flask, 1.0 g of p-toluenesulfonic acid monohydrate was dissolved in anhydrous tetrahydrofuran, and then 1 g of molecular sieves (spherical Molecular sieve 3mm-5mm), then add 18g poly (ethylene glycol) methacrylate (Mn of polyethylene glycol: 200) and 7g 4-methoxybenzaldehyde and mix well, put the round bottom flask into ice water and stir to react for 6 hours. Remove the molecular sieve by filtration and remove the solvent by vacuum distillation. After removing the solvent, purify the transparent liquid residue by silica gel column chromatography to obtain crosslinker RJ-2.

[0074] 10 g acrylamide (methyl methacrylate / vinyl acetate), 0.012 g ammonium persulfate, 1.5 g crosslinking agent RJ-2, and 0.4 g sodium dodecylbenzene sulfonate were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C to react for a period of time (i.e., gelation time, see Table 1). According to different monomer types, 3 groups of self-destructive jelly valve products were obtained. The experimental results are shown in Table 1.

[0075] Table 1 Effect of monomer type on gel formation time and gel breaking time of gel valve

[0076] serial number Monomer type Gelation time / h Breaking time / day 1 Acrylamide 3 7 2 Methyl Methacrylate 3.5 8 3 Vinyl acetate 4 10

[0077] It can be seen from Table 1 that the monomer type will affect the gelling and breaking time of the gel valve. In practical applications, the autocatalytic rate can be adjusted by changing the monomer type to control the gelling and breaking time of the gel valve.

[0078] Example 2

[0079] In a 250 mL round-bottom flask, 1.0 g of p-toluenesulfonic acid monohydrate was dissolved in anhydrous tetrahydrofuran, and then 1 g of molecular sieves (spherical Molecular sieve (3mm-5mm), then add 20g poly (ethylene glycol) methacrylate (Mn of polyethylene glycol: 300) and 5g 4-methoxybenzaldehyde and mix well, put the round bottom flask into ice water and stir to react for 6 hours. Remove the molecular sieve by filtration and remove the solvent by vacuum distillation. After removing the solvent, purify the transparent liquid residue by silica gel column chromatography to obtain crosslinker RJ-3.

[0080] In a 250 mL round-bottom flask, 1.0 g of p-toluenesulfonic acid monohydrate was dissolved in anhydrous tetrahydrofuran, and then 1 g of molecular sieves (spherical Molecular sieve 3mm-5mm), then add 25g poly (ethylene glycol) methacrylate (Mn of polyethylene glycol: 600) and 5g 4-methoxybenzaldehyde and mix well, put the round bottom flask into ice water and stir to react for 6 hours. Remove the molecular sieve by filtration and remove the solvent by vacuum distillation. After removing the solvent, purify the transparent liquid residue by silica gel column chromatography to obtain crosslinking agent RJ-6.

[0081] 10 g acrylamide, 0.012 g ammonium persulfate, 1.5 g cross-linking agent (RJ-2, RJ-3), and 0.4 g sodium dodecylbenzene sulfonate were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C to react for a period of time (i.e., gelation time, see Table 2) to obtain two groups of self-destructive jelly valve products. The experimental results are shown in Table 2.

[0082] Table 2 Effect of cross-linking agent molecular weight on gel formation time and gel breaking time of gel valve

[0083] serial number Crosslinker type Gelation time / h Breaking time / day 1 RJ-2 3 7 2 RJ-3 2.5 5

[0084] It can be seen from Table 2 that the molecular weight of the cross-linking agent will affect the gelling and breaking time of the gel valve. The larger the molecular weight of the cross-linking agent, the shorter the breaking time of the gel valve.

[0085] Example 3

[0086] 9 g (12 g / 15 g) of acrylamide, 0.01 g of ammonium persulfate, 1.5 g of crosslinking agent RJ-2, and 0.5 g of sodium dodecylbenzene sulfonate were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C to react for a period of time (i.e., gelation time, see Table 3) to obtain 3 groups of self-destructive jelly valve products. The experimental results are shown in Table 3.

[0087] Table 3 Effect of monomer dosage on gel formation time and gel breaking time of gel valve

[0088] serial number Monomer dosage / g Gelation time / h Breaking time / day 1 9 5 9 2 12 3 8 3 15 2.5 7

[0089] As can be seen from Table 3, the amount of monomer used will also affect the gelling and breaking time of the gel valve. The more monomer is used, the shorter the gelling time and breaking time of the gel valve. The self-breaking gel valve can adjust the degradation time of the gel valve by controlling the amount of monomer added. In actual work, the breaking time of the gel valve can be controlled according to the actual construction conditions on site, which has strong adaptability.

[0090] Example 4

[0091] 15 g acrylamide, 0.015 g ammonium persulfate, 2 g crosslinking agent RJ-2, and 0.5 g sodium dodecylbenzene sulfonate were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C (60 ° C / 70 ° C) to react for a period of time (i.e., gelation time, see Table 4), and 3 groups of self-destructive jelly valve products were obtained. The experimental results are shown in Table 4.

[0092] Table 4 Effect of temperature on gel formation time and gel breaking time of gel valve

[0093] serial number Temperature / ℃ Gelation time / h Breaking time / day 1 60 5 12 2 70 4 9 3 80 2 7

[0094] It can be seen from Table 4 that the higher the temperature, the shorter the gelling time and gel breaking time of the gel valve.

[0095] Example 5

[0096] Add 12g acrylamide, 0.01g ammonium persulfate, 2g crosslinker RJ-2, 0.5g sodium dodecylbenzene sulfonate to a 150mL reagent bottle, and then add distilled water to prepare a 100mL mixed solution. Use a horizontal flow pump to inject 1PV of the prepared mixed solution into the core with a permeability of 2100mD, and place it in a constant temperature oven at 80℃ to react for 3h to form a gel.

[0097] The pressure-bearing performance of the self-breaking jelly valve prepared was tested by nitrogen reverse displacement. The experimental results showed that the breakthrough pressure of the jelly valve reached 15.1MPa, indicating that the self-breaking jelly valve has strong pressure-bearing performance and strong adaptability in formations below 15.1MPa. It has been verified that the breakthrough pressure of the self-breaking jelly valve has remained stable within 9 days. After 9 days, the breakthrough pressure of the self-breaking jelly valve began to decrease and the jelly began to break. After 1-2 hours, the self-breaking jelly valve completely broke into liquid.

[0098] The breakthrough pressure of the self-breaking jelly valves obtained in other embodiments is greater than 15 MPa.

[0099] Comparative Example 1

[0100] 10 g acrylamide, 0.015 g ammonium persulfate, 1 g cross-linking agent (RJ-2, RJ-6), and 0.5 g sodium dodecylbenzene sulfonate were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C to react for a period of time (i.e., gelation time, see Table 5) to obtain 2 groups of self-destructive jelly valve products. The experimental results are shown in Table 5.

[0101] 10 g acrylamide, 0.015 g ammonium persulfate, and 1 g cross-linking agent (polyethylene glycol diacrylate, Mn of the polyethylene glycol segment is 200) were added to a 150 mL reagent bottle in sequence, and then distilled water was added to prepare a 100 mL mixed solution. The reagent bottle was placed in a constant temperature water bath at 80 ° C to react for a period of time (i.e., gelation time, see Table 5) to obtain a group of self-destructive jelly valve products. The experimental results are shown in Table 5.

[0102] Note: Among the above self-destructive jelly valve products, the self-destructive jelly valve products corresponding to the cross-linking agents RJ-2 and RJ-6 are examples, and the self-destructive jelly valve products corresponding to polyethylene glycol diacrylate are comparative examples (i.e., the main description object of comparative example 1). For a more intuitive description, these three groups of products are reviewed together.

[0103] Table 5 Effect of cross-linking agent type on gel formation time and gel breaking time of gel valve

[0104] serial number Crosslinker type Gelation time / h Breaking time / day 1 RJ-2 4.5 6 2 RJ-6 3.5 4 3 Polyethylene glycol diacrylate 1.5 2

[0105] Comparative Example 2

[0106] The base liquid of the gel valve was prepared according to the following formula: by mass percentage, (5%, 20%) monomer (acrylamide) + 1% degradable crosslinking agent RJ-2 + 0.01% initiator (ammonium persulfate) + 0.2% dispersant (sodium dodecylbenzene sulfonate) + the balance was water. The base liquid was then placed in a constant temperature water bath at 80°C to form a gel. The experimental results are shown in Table 6.

[0107] Table 6

[0108] serial number Monomer addition / % Gelation time / h Breaking time / day 1 5 5.5 13 2 20 1 4

[0109] Comparative Example 3

[0110] The base liquid of the gel valve was prepared according to the following formula: by mass percentage, 8% monomer (acrylamide) + (0.5%, 3%) degradable crosslinking agent RJ-2 + 0.01% initiator (ammonium persulfate) + 0.2% dispersant (sodium dodecylbenzene sulfonate) + the balance was water. The base liquid was then placed in a constant temperature water bath at 80°C to form a gel. The experimental results are shown in Table 7.

[0111] Table 7

[0112] serial number Degradable cross-linking agent dosage / % Gelation time / h Breaking time / day 1 0.5 4 3 2 3 1.5 20

[0113] The gel breaking time of these two groups of experiments was too fast or too slow, which did not meet the requirements of on-site construction.

[0114] Comparative Example 4

[0115] The base liquid of the gel valve was prepared according to the following formula: by mass percentage, 8% monomer (acrylamide) + 1% degradable crosslinking agent RJ-2 + (0.005%, 0.02%) initiator (ammonium persulfate) + 0.2% dispersant (sodium dodecylbenzene sulfonate) + the balance was water. The base liquid was then placed in a constant temperature water bath at 80°C to form a gel. The experimental results are shown in Table 8.

[0116] Table 8

[0117] serial number Initiator dosage / % Gelation time / h Breaking time / day 1 0.005 6 6 2 0.02 0.5 6

[0118] The gelation time of these two groups of experiments was too fast or too slow, which did not meet the requirements of on-site construction.

[0119] Comparative Example 5

[0120] The base liquid of the gel valve was prepared according to the following formula: by mass percentage, 8% monomer (acrylamide) + 1% degradable crosslinker RJ-2 + 0.01% initiator (ammonium persulfate), (0.1%, 0.6%) dispersant (sodium dodecylbenzene sulfonate) + the balance was water. The base liquid was then placed in a constant temperature water bath at 80°C to form a gel. The experimental results are shown in Table 9.

[0121] Table 9

[0122]

[0123]

[0124] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention rather than all the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

[0125] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0126] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0127] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0128] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0129] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0130] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A self-breaking jelly valve, comprising the following raw materials in percentage by mass: 8%-15% olefin-containing monomer, 1%-2% degradable crosslinking agent, 0.01%-0.015% initiator, 0.2%-0.5% dispersant, 82.485%-90.79% water; in, The degradable cross-linking agent is derived from a reaction product obtained by reacting an anhydrous strong acid, poly(ethylene glycol) methacrylate as shown in formula (1) and methoxylated benzaldehyde as shown in formula (2); In formula (2), the position indicated by 1 and / or the position indicated by 2 is substituted by a methoxy group.

2. The self-breaking jelly valve according to claim 1, characterized in that The preparation comprises the following raw materials in mass percentage: 10%-13% of olefin-containing monomer, 1.5%-2% of degradable cross-linking agent, 0.012%-0.014% of initiator, 0.35%-0.45% of dispersant, 84.536%-88.138% of water.

3. The self-breaking jelly valve according to claim 1, characterized in that: The number average molecular weight of the poly(ethylene glycol) segment in the poly(ethylene glycol) methacrylate is 200-600; preferably, the number average molecular weight of the poly(ethylene glycol) segment in the poly(ethylene glycol) methacrylate is at least one of 200, 300, 400, and 600, preferably at least one of 200 and 300; And / or, the anhydrous strong acid is selected from at least one of p-toluenesulfonic acid and trifluoromethanesulfonic acid; preferably, The structural formula of the degradable cross-linking agent is shown in formula (3):

4. The self-breaking jelly valve according to claim 1, characterized in that The preparation method of the degradable cross-linking agent comprises the following steps: Anhydrous strong acid, poly(ethylene glycol) methacrylate, methoxylated benzaldehyde and anhydrous tetrahydrofuran are mixed to carry out a crosslinking reaction, preferably after the crosslinking reaction, filtering, removing the solvent by reduced pressure distillation and purifying by silica gel column chromatography to obtain the degradable crosslinking agent; preferably, The mass ratio of anhydrous strong acid, poly(ethylene glycol) methacrylate and methoxylated benzaldehyde is 1:(15-25):(4-10), preferably 1:(15-20):(5-8); and / or, The cross-linking reaction temperature is 0-10°C, preferably 0-5°C; and / or, the cross-linking reaction time is 5-7h, preferably 5.5-6h; and / or, The mass ratio of the poly(ethylene glycol) methacrylate to anhydrous tetrahydrofuran is (2-3):

1.

5. The self-breaking jelly valve according to claim 1, characterized in that: The olefinic monomer is selected from one or more of acrylamide, methyl methacrylate, hydroxyethyl methacrylate, ethyl acrylate, and vinyl acetate; and / or, The initiator is selected from one or more of ammonium persulfate, potassium persulfate, sodium persulfate, ammonium persulfate / sodium bisulfite and azobisisobutylamidine hydrochloride; and / or, The dispersant is selected from one or more of sodium dodecylbenzene sulfonate, dodecylphenol polyoxyethylene ether, Tween 40, Tween 60 and Tween 80.

6. The self-breaking jelly valve according to any one of claims 1 to 5, characterized in that: The self-breaking jelly valve can self-degrade and break the jelly, preferably, the self-breaking time is 4-12 days, preferably 5-10 days, more preferably 7-8 days; and / or, The self-destructing jelly valve is prepared by the following method: mixing the preparation raw materials including the olefinic monomer, the degradable cross-linking agent, the initiator, the dispersant and water to obtain a self-destructing jelly valve base liquid, and then gelling to obtain the self-destructing jelly valve; Preferably, the gelling time is 1-5 h, preferably 1-4 h, more preferably 2-3 h.

7. A method for preparing a self-destructing jelly valve according to any one of claims 1 to 6, comprising mixing the raw materials including the olefinic monomer, the degradable cross-linking agent, the initiator, the dispersant and water to obtain a self-destructing jelly valve base liquid, and then gelling to obtain the self-destructing jelly valve; preferably, The gelling time is 1-5 hours, preferably 1-4 hours, more preferably 2-3 hours; and / or the gelling temperature is 60-80°C.

8. A method for controlling pressure during drilling, comprising the following steps: According to the raw materials and proportions of the self-destructing jelly valve, the raw materials including the olefinic monomer, the degradable cross-linking agent, the initiator, the dispersant and water are mixed to obtain a self-destructing jelly valve base liquid; The self-destructing jelly valve base liquid is transported downhole, and the self-destructing jelly valve base liquid is gelled at the temperature of the reservoir section to form a self-destructing jelly valve; When the self-degradation breaking time of the self-degrading jelly valve is reached, the self-degrading jelly valve starts to break itself, and the resulting broken jelly liquid is returned to the ground; The self-breaking jelly valve is the self-breaking jelly valve according to any one of claims 1 to 6 or the self-breaking jelly valve prepared by the preparation method according to claim 7.

9. The method for controlling pressure during drilling according to claim 8, characterized in that: The reservoir temperature is 60-80°C; and / or, the gelling time is 1-5h, preferably 1-4h, more preferably 2-3h; and / or, The time for the self-breaking jelly valve to start self-breaking is 4-12 days, preferably 5-10 days, and more preferably 7-8 days.

10. Application of the self-destructing jelly valve according to any one of claims 1 to 6, the self-destructing jelly valve prepared by the preparation method according to claim 7, or the drilling pressure control method according to claim 8 or 9 in the field of underbalanced drilling technology.

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