Bio-gel retarder for acidification, and preparation method therefor and use thereof

Abstract

The present application belongs to the technical field of fracturing fluids, and relates to a bio-gel retarder for acidification, and a preparation method therefor and the use thereof. The preparation method for a bio-gel retarder for acidification comprises the following steps: 1) mixing a bio-gel mother liquor with an alkaline solution, reacting same by means of vibration to obtain a first reaction product, and then performing alcohol precipitation, centrifugation and drying to obtain a preliminary sample product; 2) mixing, in an organic alcohol, a p-hydroxybenzene compound containing a hydrophilic group, paraformaldehyde, and a primary amine compound containing a double bond, carrying out a reflux reaction, and filtering the resulting reflux product to obtain an intermediate product; and 3) mixing the preliminary sample product, the intermediate product, a cationic monomer and water, adding an initiator thereto, and carrying out a reaction to obtain a bio-gel retarder for acidification. The bio-gel retarder for acidification can effectively slow down the acid-rock reaction rate, and has the advantages of being environmentally friendly, resistant to high temperature, etc., which are conducive to achieving remote deep acidification and solving problems regarding deep penetration and stimulation of carbonate reservoirs.

Description

A biological gel retarding agent for acidification and a preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. 202411027132.3, filed on July 29, 2024, and entitled "A biological gel retarding agent for acidification and a preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of fracturing fluid, in particular to a biological gel retarding agent for acidification and a preparation method and application thereof. BACKGROUND

[0003] In China, carbonate reservoirs account for a considerable proportion in oil and gas reservoir formations, such as Ordos Basin, Sichuan Basin and Tarim Basin, etc. The reservoirs in these regions are mainly carbonate reservoirs. The characteristics of this type of reservoir are that the oil and gas reservoirs are buried deep, the permeability is low, and the heterogeneity is serious. Acid fracturing is a key technology for the development and yield increase of carbonate reservoirs. However, the hydrochloric acid used in the traditional acid fracturing system reacts quickly with carbonate rocks, and can only etch the carbonate rocks near the wellbore of the oil layer, the communication distance at the bottom of the oil well is short, and a high fracture conductivity cannot be formed.

[0004] At present, thickened acid technology is mostly used to slow down the reaction rate of the acid system with carbonate rocks. Specifically, a good thickening agent is added to the acid solution of a certain concentration to increase the viscosity of the acid system, reduce the diffusion rate of H + to the rock surface, so as to slow down the acid-rock reaction rate and ultimately achieve the purpose of retarding. At the same time, the high-viscosity acid system can make the acid enter the deeper part of the rock fracture for deep acidification, increase the action radius of acidification construction, and communicate the deep oil and gas area, so as to achieve the purpose of increasing the yield of oil and gas wells. However, as the reservoir temperature rises, the thickening agent molecules are broken and shrunk in the formation under the influence of the formation temperature, which makes the viscosity of the acid solution decrease rapidly, the release rate of H + increases, the acid-rock reaction rate increases, and the effective migration distance becomes shorter. For high-temperature carbonate reservoirs, if the acid-rock reaction rate is very fast when the conventional acid fracturing technology is used, the acid etching fracture length is short, and the yield increase effect is often not ideal, which is one of the technical problems faced by acid fracturing reconstruction of this type of reservoir for a long time. In addition, the residues of commonly used thickening agents such as acrylamide and its modified products will cause irreversible damage to the formation environment after use, which does not meet the double carbon requirements.

[0005] Therefore, how to provide an environmentally friendly, high-temperature resistant, and effective acid-rock reaction rate retarding agent for acidification is a technical problem to be solved in the field. SUMMARY

[0006] The application provides a biological glue retarder for acidification and a preparation method and application thereof, which is prepared from raw materials including a biological glue mother liquor and an alkaline solution, and is applied to an acid liquid system, so that the acid rock reaction rate can be effectively slowed down, and the biological glue retarder has advantages of environmental protection, high temperature resistance and the like, and helps to realize remote deep acidification and solve the deep penetration reconstruction problem of a carbonate rock reservoir.

[0007] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme.

[0008] In a first aspect, the application provides a preparation method of a biological glue retarder for acidification, comprising the following steps:

[0009] 1) mixing a biological glue mother liquor and an alkaline solution, oscillating and reacting to obtain a first reaction product, then performing alcohol precipitation, centrifugation and drying to obtain a preliminary sample product;

[0010] 2) mixing a p-hydroxybenzene compound containing a hydrophilic group, polyformaldehyde and a primary amine compound containing a double bond in an organic alcohol, performing reflux reaction, and filtering the reflux product to obtain an intermediate product;

[0011] 3) mixing the preliminary sample product, the intermediate product, a cationic monomer and water, adding an initiator to react to obtain the biological glue retarder for acidification.

[0012] In the preparation method of the biological glue retarder for acidification, in step 1), the biological glue in the biological glue mother liquor includes at least one of a sphingan glue, a welan glue, a xanthan gum and a diutan glue.

[0013] In the preparation method of the biological glue retarder for acidification, in step 1), the alkaline solution includes at least one of a NaOH solution and a KOH solution.

[0014] In the preparation method of the biological glue retarder for acidification, in step 1), the mass ratio of the biological glue mother liquor to the alkaline solution is 5-12:2-5.

[0015] In the preparation method of the biological glue retarder for acidification, in step 1), the mass-volume concentration of the biological glue in the biological glue mother liquor is 3-6 mg / mL.

[0016] In the preparation method of the biological glue retarder for acidification, in step 1), the viscosity-average molecular weight of the biological glue is 1 million Da-20 million Da.

[0017] In the preparation method of the biological glue retarder for acidification, in step 1), the concentration of the alkaline solution is 0.1-0.2 mol·L -1 .

[0018] In the present application, the biological glue mother liquor can undergo a hydrolysis reaction in an alkaline solution to remove part of the acetyl group to obtain a partially deacetylated sphingosine glue (i.e., the first reaction product or the preliminary sample product of the biological glue retarding agent); by adjusting the concentration of the alkaline solution, the amount of acetyl group removed can be controlled, thereby obtaining partially deacetylated sphingosine glue with different acetyl group contents, wherein the acetyl group content has a certain influence on the performance of the product.

[0019] In the above method for preparing the biological glue retarding agent for acidification, in step 1), the biological glue is prepared by a preparation method comprising the following steps:

[0020] The production strain is inoculated into a seed culture medium for culture, and then the cultured production strain is inoculated into a fermentation culture medium for fermentation to obtain a strain fermentation liquor;

[0021] The strain fermentation liquor is subjected to alcohol precipitation, and the precipitate obtained by alcohol precipitation is sequentially subjected to suction filtration treatment, washing treatment, and freeze-drying treatment to obtain the biological glue.

[0022] In the above method for preparing the biological glue retarding agent for acidification, in step 1), the biological glue (e.g., sphingosine glue) has a backbone structure with a tetrasaccharide repeating unit structure, and the four sugars are D-glucose, D-glucuronate, L-rhamnose, and L-mannose. For example, the structure of the biological glue is as follows:

[0023] In the present application, the biological glue forms a three-dimensional network structure in an aqueous solution through intermolecular interactions such as covalent bonds and hydrogen bonds, and the structure of the biological glue can still be formed in an acid solution, so the biological glue has acid resistance. In addition, the three-dimensional structure of the biological glue increases the viscosity of the biological glue aqueous solution system.

[0024] The biological glue provided by the present application has good stability and unique shear thinning property. The aqueous solution thereof has thermal stability, and the viscosity thereof is basically unchanged in the temperature change range of 80-150°C; the viscosity is basically not affected in the pH range of 2-13; the salt stability is high (the concentration of potassium chloride, chloride, and calcium chloride is <100 g / L), and the biological glue has compatibility with most salts. When the temperature continues to rise, the viscosity of the solution decreases, and when the temperature decreases, the viscosity can fully recover. When a certain shear force is applied, the viscosity rapidly decreases, and the viscosity can still recover once the shear force is removed.

[0025] In the above method for preparing the biological glue retarding agent for acidification, in step 1), in the backbone structure of the biological glue, the mass content of the D-glucose, D-glucuronate, L-rhamnose, and L-mannose is 55%-60%, 2.0%-2.5%, 18%-33%, and 6.0%-7.2%, respectively.

[0026] In the preparation method of the acidizing biological gum retarder, the side chain structure of the biological gum in the step 1) contains L-mannose and L-rhamnose.

[0027] In the preparation method of the acidizing biological gum retarder, the molar ratio of the L-mannose and the L-rhamnose in the side chain structure of the biological gum in the step 1) is 1:(1.5-2).

[0028] In the preparation method of the acidizing biological gum retarder, the side chain structure of the biological gum in the step 1) contains at least one of acetyl, carboxyl and pyruvic acid groups.

[0029] In the preparation method of the acidizing biological gum retarder, the side chain structure of the biological gum in the step 1) contains acetyl, and the content of the acetyl in the side chain structure of the biological gum is 6.6%-7.5%.

[0030] In the preparation method of the acidizing biological gum retarder, the side chain structure of the biological gum in the step 1) contains carboxyl and pyruvic acid groups.

[0031] In the present application, the side chain structure of the biological gum contains carboxyl and pyruvic acid groups, and the biological gum has electrostatic shielding effect in aqueous solution through the charges of the two groups, which can increase the stability of the biological gum in aqueous solution, so that the biological gum can maintain certain viscosity and stability in acid solution. The acidizing biological gum retarder can effectively reduce the friction of the acid system when applied to the acid system.

[0032] In the preparation method of the acidizing biological gum retarder, the biological gum in the biological gum mother liquor in the step 1) is a sphingan.

[0033] In the preparation method of the acidizing biological gum retarder, the sphingan in the step 1) is a fermentation product of Sphingomonas sp. WG (i.e., a production strain), and the preservation number of the Sphingomonas sp. WG is CCTCC No: M2013161.

[0034] In the preparation method of the acidizing biological gum retarder, the shock reaction in the step 1) is carried out at a temperature of 90-120°C.

[0035] In the preparation method of the acidizing biological gum retarder, the time of the shock reaction in the step 1) is 20-60 min.

[0036] In the preparation method of the acidizing biological gum retarder, the mixing in the step 1) is carried out by vortex.

[0037] In the preparation method of the acidizing biogel retarder, in the step 1), the rotation speed of the vortex is 1100 rpm to 1300 rpm.

[0038] In the preparation method of the acidizing biogel retarder, in the step 1), the mass content of acetyl groups in the first reaction product or the preliminary sample product is 3% to 6%.

[0039] In the preparation method of the acidizing biogel retarder, in the step 1), the biogel mother liquor and the alkaline solution are mixed to make the final concentration of the alkaline solution reach a pH value of 10 to 12, and then vortexed and mixed uniformly to obtain a biogel alkaline mixed solution, and then the shock reaction is performed.

[0040] By adjusting the concentration of the alkaline solution, the content of acetyl groups in the preliminary sample product obtained by alkaline decomposition can be controlled. Since acetyl groups can interact with hydrogen ions, controlling the content of acetyl groups can control the hydrogen release performance of the reaction product in an acidic system, thereby controlling the retarding and corrosion inhibition performance of the acidizing biogel retarder product.

[0041] In the preparation method of the acidizing biogel retarder, in the step 1), the biogel mother liquor and the alkaline solution are mixed, and the first reaction is performed at a temperature of 90 to 120°C to obtain a first reaction product. After cooling to room temperature, the pH value is adjusted to 6.5 to 7.5, and then alcohol precipitation, centrifugation, and drying treatment of the supernatant are performed to obtain a preliminary sample product.

[0042] In the preparation method of the acidizing biogel retarder, in the step 1), the pH value is adjusted by an HCl solution.

[0043] In the preparation method of the acidizing biogel retarder, in the step 1), the alcohol used in the alcohol precipitation process includes at least one of ethanol, methanol, and isopropyl alcohol.

[0044] In the preparation method of the acidizing biogel retarder, in the step 1), the concentration of the HCl solution is 0.1 to 1 mol·L -1 .

[0045] In the preparation method of the acidizing biogel retarder, in the step 1), the supernatant is dried to obtain a preliminary sample product.

[0046] In the preparation method of the acidizing biogel retarder, in the step 2), the mass ratio of the hydrophilic group-containing p-hydroxybenzene compound, the paraformaldehyde, the primary amine compound containing double bonds, and the organic alcohol is 20 to 50:10 to 30:10 to 30:20 to 50.

[0047] In the preparation method of the acidification biological glue retarder, in the step 2), the hydrophilic group comprises at least one of a carboxylate salt group and a sulfonate salt group.

[0048] In the preparation method of the acidification biological glue retarder, in the step 2), the p-hydroxybenzene compound comprises at least one of sodium methyl p-hydroxybenzoate, sodium ethyl p-hydroxybenzoate, sodium propyl p-hydroxybenzoate and sodium p-hydroxybenzenesulfonate.

[0049] The p-hydroxybenzene compound with a hydrophilic group is used in the application, which can increase the solubility of the p-hydroxybenzene compound in the organic alcohol, thereby facilitating the reflux reaction between the p-hydroxybenzene compound, the paraformaldehyde and the primary amine compound containing a double bond, and obtaining the required intermediate product.

[0050] In the preparation method of the acidification biological glue retarder, in the step 2), the primary amine compound containing a double bond comprises at least one of an allylamine and an acetamide.

[0051] In the preparation method of the acidification biological glue retarder, in the step 2), the p-hydroxybenzene compound with a hydrophilic group and the paraformaldehyde are mixed in the organic alcohol, and then the primary amine compound containing a double bond is added for reflux reaction.

[0052] In the preparation method of the acidification biological glue retarder, in the step 2), the mixing temperature is 60-70°C.

[0053] In the preparation method of the acidification biological glue retarder, in the step 2), the organic alcohol comprises butanol.

[0054] In the preparation method of the acidification biological glue retarder, in the step 2), the reflux reaction temperature is 120-130°C.

[0055] In the preparation method of the acidification biological glue retarder, in the step 2), butanol is added into a reaction kettle, the p-hydroxybenzene compound with a hydrophilic group, the paraformaldehyde are sequentially added under stirring, the temperature is increased to 60-70°C, the primary amine compound containing a double bond is slowly added, the temperature is increased to 120-130°C for reflux reaction for 6-8h, and then the intermediate product is obtained after filtration.

[0056] In the preparation method of the acidification biological glue retarder, in the step 3), the mass ratio of the preliminary sample product, the intermediate product, the cationic monomer, the initiator and the water is 7-17:8-15:2-5:0.2-1:70-85.

[0057] In the preparation method of the acidizing bio-gel retarder, in the step 3), the cationic monomer comprises at least one of hexadecyl methyldiallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride and methacryloyl propyl trimethyl ammonium chloride.

[0058] In the preparation method of the acidizing bio-gel retarder, in the step 3), the initiator comprises at least one of ammonium persulfate, potassium persulfate and azobisdimethylaminoform hydrochloride.

[0059] In the preparation method of the acidizing bio-gel retarder, in the step 3), the reaction temperature is 60-90℃.

[0060] In the preparation method of the acidizing bio-gel retarder, in the step 3), the reaction time is 3-5h.

[0061] In the preparation method of the acidizing bio-gel retarder, in the step 3), water, intermediate product, primary sample product and cationic monomer are added into a reaction kettle, and stirred sufficiently and heated to 60-90℃, then the initiator is slowly added dropwise, and reacted for 3-5h, and after drying, the acidizing bio-gel retarder is obtained.

[0062] According to the second aspect of the present application, an acidizing bio-gel retarder is provided, which is prepared by any of the preparation methods of the acidizing bio-gel retarder.

[0063] According to the preparation method of the acidizing bio-gel retarder, the acidizing bio-gel retarder with excellent performance can be prepared, and the preparation process is environmentally friendly, simple and easy to operate.

[0064] According to the third aspect of the present application, an acidizing bio-gel retarder is provided for use as an acidizing fracturing fluid in the development of oil and gas reservoirs, wherein the acidizing bio-gel retarder is prepared according to the second aspect of the present application, or the acidizing fracturing fluid comprises at least the acidizing bio-gel retarder according to the second aspect of the present application.

[0065] In the above use, the acidizing bio-gel retarder is suitable for acidizing treatment of high-temperature carbonate reservoirs with a reservoir temperature of 120℃ or higher.

[0066] In the above use, the acidizing fracturing fluid comprises hydrochloric acid, acidizing bio-gel retarder, aldehyde ketone amine condensate corrosion inhibitor, fluorocarbon cleanup aid, iron ion stabilizer, cationic surfactant and water.

[0067] In the application, the acid fracturing fluid comprises the following components by mass percentage: 15-20% of hydrochloric acid, 2-5% of the acidification biological gel retardant, 0.5-2% of fluorocarbon cleanup additive, 1-3% of aldehyde ketone amine condensate corrosion inhibitor, 0.5-2% of iron ion stabilizer, 0-0.4% of cationic surfactant, and the balance of water.

[0068] In the application, the fluorocarbon cleanup additive comprises quaternary ammonium salt cationic fluorocarbon surfactant and / or ethoxy nonionic fluorocarbon surfactant.

[0069] In the application, the aldehyde ketone amine condensate corrosion inhibitor is formed by aldehyde ketone amine condensation with a molecular weight less than 10 million.

[0070] In the application, the iron ion stabilizer comprises CT1-7 reducing agent.

[0071] In the application, the acid fracturing fluid has a viscosity less than 45 mPa·s at 25℃, a retardation rate of 81.13% or more at 120℃, and a corrosion rate less than 2 g / (m 2 ·h).

[0072] According to the acid fracturing fluid of the application, since the acid fracturing fluid comprises any one of the acidification biological gel retardants according to the first aspect of the application, the acid liquid system can effectively slow down the reaction rate of acid rock reaction (i.e., acidification etching reaction of the acid liquid system on the carbonate rock reservoir), and is easy to be injected into the carbonate rock reservoir, automatically broken after the acid rock reaction, and has no residue, so that the acid liquid system can reduce the damage to the carbonate rock reservoir.

[0073] The implementation of the application has at least the following beneficial effects:

[0074] (1) The acidification biological gel retardant provided by the application is prepared from raw materials including biological gel mother liquor and alkaline solution. The acetyl content in the side chain structure of the biological gel can be controlled by alkaline hydrolysis of the biological gel mother liquor in different concentrations of alkaline solution, and the viscosity is controlled in a suitable range. When the acidification biological gel retardant is applied to the acid liquid system, the acid rock reaction rate can be slowed down, the slow release of H + is realized, so that the purpose of remote deep acidification and solving the deep penetration reconstruction problem of the carbonate rock reservoir is achieved.

[0075] (2) The acidification biological gel retardant according to the application can effectively reduce the frictional resistance of the acid liquid system because the biological gel contains carboxyl and pyruvic acid groups.

[0076] (3) The acidification biological gel retardant according to the application has the advantages of easy injection, easy flowback, and reducing secondary damage to the reservoir.

[0077] (4) The preparation method of the acidizing biological gel retarder provided by the application can prepare an acidizing biological gel retarder with excellent performance, and the preparation process is environmentally friendly and simple and easy to operate;

[0078] (5) The acidizing fracturing fluid according to the application is automatically broken after the acid-rock reaction ends, has no residue, has low reservoir damage, and is suitable for high-temperature carbonate reservoirs with a reservoir temperature of 120℃ or above. BRIEF DESCRIPTION OF DRAWINGS

[0079] The drawings incorporated into the specification and forming a part of the specification, show embodiments consistent with the application, and together with the specification serve to explain the principles of the application.

[0080] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or related technical descriptions will be briefly introduced below. Obviously, for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0081] Figure 1 is a preparation flowchart of the acidizing biological gel retarder in an embodiment of the application;

[0082] Figure 2 is a standard curve graph of acetyl content testing;

[0083] Figure 3 is a resistance reduction curve graph of the acidizing fracturing fluid in Example 1;

[0084] Figure 4 is a resistance reduction curve graph of the acidizing fracturing fluid in Example 2;

[0085] Figure 5 is a resistance reduction curve graph of the acidizing fracturing fluid in Example 3;

[0086] Figure 6 is a resistance reduction curve graph of the acidizing fracturing fluid in Example 4;

[0087] Figure 7 is a curve graph of acid concentration over time of the acidizing fracturing fluid in Examples 3-6 and a 20% hydrochloric acid solution. DETAILED DESCRIPTION

[0088] In order to make the purpose, technical solutions and advantages of the application more clear, the technical solutions in the embodiments of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0089] Some embodiments of the first aspect of the application provide a preparation method of an acidizing biological gel retarder, comprising the following steps:

[0090] 1) mixing the bio-gum mother liquor and the alkaline solution, oscillating to obtain a first reaction product, then alcohol precipitation, centrifugation and drying to obtain a preliminary sample product;

[0091] 2) mixing the p-hydroxybenzene compound containing a hydrophilic group, paraformaldehyde and the primary amine compound containing a double bond in an organic alcohol, performing a reflux reaction, and filtering the reflux product to obtain an intermediate product;

[0092] 3) mixing the preliminary sample product, the intermediate product, the cationic monomer and water, adding an initiator to obtain the acidizing bio-gum retarding agent.

[0093] In some embodiments, in the step 1), the bio-gum in the bio-gum mother liquor comprises at least one of a sphingan, a welan gum, a xanthan gum and a diutan gum.

[0094] In the present application, the bio-gum refers to a polysaccharide polymer metabolized by microorganisms, which can be obtained by fermentation or purchased on the market. For example, the bio-gum can be a fermentation product sphingan obtained by fermentation of Sphingomonas sp. WG, i.e., a production strain. The accession number of Sphingomonas sp. WG is CCTCC No: M2013161.

[0095] In the present application, the viscosity of the bio-gum mother liquor has little change in the temperature range of 80-140℃, the pH range of 2-11 and the salinity range of 500-2500. Specifically, the viscosity of the xanthan gum mother liquor has no significant change even at a high temperature of 130℃, which can ensure the viscosity of the acidizing bio-gum retarding agent, thereby helping to ensure the viscosity of the acidizing system.

[0096] The present application does not limit the ratio of the raw materials for preparing the bio-gum retarding agent. In some embodiments, in the step 1), the mass ratio of the bio-gum mother liquor to the alkaline solution can be 5-12:2-5. By limiting the ratio of the raw materials, the performance of the bio-gum retarding agent can be maximized.

[0097] The present application does not limit the physical parameters of the bio-gum mother liquor. For example, in some embodiments, the mass-volume concentration of the bio-gum in the bio-gum mother liquor is 3-6 mg / mL, such as 4 mg / mL, 4.5 mg / mL, 5 mg / mL, 5.5 mg / mL, 6 mg / mL or a range consisting of any two of them; and the viscosity-average molecular weight of the bio-gum is 1 million Da-20 million Da (e.g., 5 million Da, 8 million Da, 10 million Da, 12 million Da, 15 million Da, 18 million Da or 19 million Da). The viscosity-average molecular weight can be measured by the dilute solution viscosity method.

[0098] The present application does not limit the specific type of alkaline solution. Illustratively, in some embodiments, the alkaline solution comprises at least one of NaOH solution and KOH solution; the concentration of the alkaline solution is 0.1-0.2 mol·L-1(e.g. 0.1 mol / L, 0.15 mol / L or 0.18 mol / L).

[0099] In the present application, the bio-gel mother liquor can undergo a hydrolysis reaction in the alkaline solution to remove part of the acetyl group, obtaining a partially deacetylated sphingan glue (i.e. the first reaction product or the preliminary sample product of the bio-gel retarder); by adjusting the concentration of the alkaline solution, the amount of acetyl group removed can be controlled, thereby obtaining a partially deacetylated sphingan glue containing different acetyl group contents, wherein the acetyl group content has a certain influence on the performance of the product.

[0100] In some embodiments, the bio-gel of the present application is a powder. The bio-gel mother liquor can be prepared by mixing the bio-gel with a solvent. Specifically, the bio-gel of the present application is easily soluble in water, insoluble in polar solvents such as alcohol and ketone, and the bio-gel mother liquor can be prepared by mixing the bio-gel with water at room temperature.

[0101] In some embodiments, in the step 1), the bio-gel is prepared by a preparation method comprising the following steps:

[0102] The production strain is inoculated into a seed culture medium for culture, and then the cultured production strain is inoculated into a fermentation culture medium for fermentation, obtaining a strain fermentation liquor;

[0103] The strain fermentation liquor is subjected to alcohol precipitation, and the precipitate obtained by alcohol precipitation is sequentially subjected to suction filtration treatment, washing treatment and freeze-drying treatment, obtaining the bio-gel.

[0104] In some embodiments, in the step 1), the bio-gel (e.g. sphingan glue) has a backbone structure of a tetrasaccharide repeating unit structure, and the tetrasaccharide is D-glucose, D-glucuronate, L-rhamnose and L-mannose, respectively.

[0105] In the present application, the bio-gel forms a three-dimensional network structure in an aqueous solution through intermolecular interactions such as covalent bonds and hydrogen bonds, and the structure of the bio-gel can still be formed in an acid solution, so the bio-gel has acid resistance. In addition, the three-dimensional structure of the bio-gel increases the viscosity of the bio-gel aqueous solution system.

[0106] The biological glue provided in the application has good stability and unique shear thinning property. The aqueous solution of the biological glue has thermal stability, and the viscosity of the solution is basically unchanged in the temperature range of 80-150 DEG C. The viscosity of the solution is basically not affected in the pH range of 2-13. The solution has high salt stability (the concentration of potassium chloride, chloride and calcium chloride is less than 100 g / L), and is compatible with most salts. The viscosity of the solution decreases when the temperature continues to rise, and the viscosity can be completely restored when the temperature decreases. When a certain shear force is applied, the viscosity decreases rapidly, and the viscosity can still recover once the shear force is lost.

[0107] In some embodiments, in the main chain structure of the biological glue, the mass content of the D-glucose, D-glucuronate, L-rhamnose and L-mannose is 55%-60%, 2.0%-2.5%, 18%-33% and 6.0%-7.2%, respectively.

[0108] In some embodiments, in the side chain structure of the biological glue, the molar ratio of the L-mannose to the L-rhamnose is 1:(1.5-2).

[0109] In some embodiments, in the side chain structure of the biological glue, the side chain structure contains at least one of an acetyl group, a carboxyl group and a pyruvic acid group.

[0110] In some embodiments, in the side chain structure of the biological glue, the side chain structure contains an acetyl group, and the content of the acetyl group in the side chain structure of the biological glue is 6.6%-7.5% (for example, 7%).

[0111] In some embodiments, in the side chain structure of the biological glue, the side chain structure contains a carboxyl group and a pyruvic acid group.

[0112] In the application, the side chain structure of the biological glue contains a carboxyl group and a pyruvic acid group. Through the charges carried by the two groups, the biological glue has an electrostatic shielding effect in the aqueous solution, which can increase the stability of the biological glue in the aqueous solution, so that the biological glue can maintain a certain viscosity and stability in the acid solution. The acidizing biological glue retarder can be applied to the acid liquid system to effectively reduce the friction of the acid liquid system.

[0113] In some embodiments, in the step 1), the oscillation reaction is carried out at a temperature of 90-120 DEG C (for example, 95 DEG C, 100 DEG C, 105 DEG C, 110 DEG C or 115 DEG C), and the oscillation reaction time is 20-60 min (for example, 30 min, 40 min or 50 min).

[0114] In some embodiments, in the step 1), the mixing is performed by vortexing at a rotation speed of 1100 rpm to 1300 rpm (for example, 1200 rpm).

[0115] In some embodiments, in the step 1), the mass content of acetyl groups in the first reaction product or the preliminary sample product is 3% to 6%. By regulating the mass content of acetyl groups in the first reaction product to be within the range of 3% to 6%, the retarding performance of the acidizing biogum retarder can be maximized.

[0116] In some embodiments, in the step 1), the biogum mother liquor and the alkaline solution are mixed to obtain a biogum alkaline mixture, in which the final concentration of the alkaline solution is adjusted to a pH value of 10 to 12, and then the mixture is subjected to vortex mixing and shock reaction.

[0117] By adjusting the concentration of the alkaline solution, the content of acetyl groups in the preliminary sample product obtained by alkaline decomposition can be regulated. Since acetyl groups can interact with hydrogen ions, regulating the content of acetyl groups can regulate the hydrogen release performance of the reaction product in an acidic system, thereby regulating the retarding and corrosion inhibition performance of the acidizing biogum retarder product.

[0118] In some embodiments, in the step 1), the biogum mother liquor and the alkaline solution are mixed, and the first reaction is performed at a temperature of 90 to 120°C to obtain a first reaction product. After cooling to room temperature, the pH value is adjusted to 6.5 to 7.5, and then the preliminary sample product is obtained by alcohol precipitation, centrifugation, and drying treatment of the centrifugal supernatant.

[0119] In the present application, the sphingan has a tetrasaccharide repeating unit backbone structure, i.e., glucose-glucuronide-glucose-X (X is L-rhamnose or L-mannose). Meanwhile, the biogum contains carboxyl groups, O-acyl groups, and the like on its structure, and contains single-chain L-mannose or L-rhamnose on the side chain. Therefore, the biogum mother liquor and the alkaline solution can react at a temperature of 90 to 120°C as follows: R-COOH-R' + MOH → R-COOHM + HOR', wherein M can be at least one of Na and K.

[0120] The preparation raw material of the application includes a bio-gum mother liquor and an alkaline solution. By controlling the reaction process of the two, the content of acetyl groups in the side chain structure of the bio-gum can be regulated, and the overall viscosity can be controlled within a suitable range. The application of the bio-gum acidizing retarder in an acid liquid system can slow down the acid-rock reaction rate, especially in carbonate rocks. Second, compared with the prior art, the bio-gum acidizing retarder has moderate and stable viscosity, good flowability in the acid liquid, easy injection, no obvious viscosity increase, and can be hydrolyzed and desorbed from the rock surface after the acid-rock reaction is completed, easy to flow back and will not cause secondary damage to the reservoir. In addition, the bio-gum acidizing retarder has good thermal stability and strong temperature resistance, and the viscosity remains stable even at 120℃ or above, which is beneficial to the acidizing treatment of carbonate reservoirs.

[0121] In addition, the bio-gum acidizing retarder of the application contains carboxyl and pyruvic acid groups, has certain biological surface activity, and can effectively reduce the frictional resistance of the acid liquid system.

[0122] In some embodiments, the bio-gum retarder is prepared by a method comprising the following steps: mixing a bio-gum mother liquor and an alkaline solution and vortexing until uniform to obtain a mixed solution; placing the mixed solution in a constant temperature shaking water bath for a first reaction; placing the product after the first reaction in ice water until it cools to room temperature, adjusting the pH to 6.5-7.5, adding 3-5 times the volume of an ethanol solution, alcohol precipitation for 3-8 hours after vortexing to separate the layers, high-speed centrifugal treatment for 20-60 minutes, and taking the supernatant; vacuum drying the supernatant to obtain the bio-gum acidizing retarder.

[0123] In the process of mixing and vortexing the bio-gum mother liquor and the alkaline solution, the bio-gum mother liquor and the alkaline solution can be added in batches. For example, the bio-gum mother liquor is divided into three parts (the first part of the bio-gum mother liquor, the second part of the bio-gum mother liquor, and the remaining bio-gum mother liquor), and the alkaline solution is divided into three parts (the first part of the alkaline solution, the second part of the alkaline solution, and the remaining alkaline solution). First, the first part of the bio-gum mother liquor and the first part of the alkaline solution are mixed and vortexed uniformly, then the second part of the bio-gum mother liquor, the second part of the alkaline solution, the remaining bio-gum mother liquor, and the remaining alkaline solution are added in turn, and the addition of the total amount of the bio-gum mother liquor and the alkaline solution is completed. Specifically, the operation of adding the bio-gum mother liquor and the alkaline solution in batches is beneficial to improving the diffusion rate and ensuring the smooth progress of the subsequent reaction. The operation of adding in batches is mainly used to adjust the addition amount of the reaction raw material and to fully react. The vortexing rate is 1100-1300 rpm, and the time is 1-2 min.

[0124] On the basis of controlling the addition amount of the bio-gum mother liquor and the alkaline solution, the first reaction time and the reaction temperature are combined to obtain a first reaction product with an acetyl group content of 3-6%.

[0125] In some embodiments, in the step 2), the mass ratio of the p-hydroxybenzene compound containing hydrophilic groups, the paraformaldehyde, the primary amine compound containing double bonds, and the organic alcohol is 20-50: 10-30: 10-30: 20-50. That is, in the step 2), the mass fraction of the p-hydroxybenzene compound containing hydrophilic groups is 20-50 parts (for example, 25 parts, 30 parts, 40 parts, or 45 parts), the mass fraction of the paraformaldehyde is 10-30 parts (for example, 15 parts, 20 parts, 25 parts, or 28 parts), the mass fraction of the primary amine compound containing double bonds is 10-30 parts (for example, 15 parts, 20 parts, 25 parts, or 28 parts), and the mass fraction of the organic alcohol is 20-50 parts (for example, 25 parts, 30 parts, 40 parts, or 45 parts).

[0126] The present application does not limit the specific type of raw materials, and exemplarily, in some embodiments, the p-hydroxybenzene compound containing hydrophilic groups is selected from a compound as shown in formula A1, wherein M is a hydrophilic group.

[0127] In some embodiments, in the step 2), the hydrophilic group includes at least one of a carboxylate salt group and a sulfonate salt group; and the p-hydroxybenzene compound includes at least one of methyl p-hydroxybenzoate sodium, ethyl p-hydroxybenzoate sodium, propyl p-hydroxybenzoate sodium, and sodium p-hydroxybenzenesulfonate.

[0128] The present application uses a p-hydroxybenzene compound with a hydrophilic group, which can increase the solubility of the p-hydroxybenzene compound in the organic alcohol, thereby facilitating the reflux reaction between the p-hydroxybenzene compound, the paraformaldehyde, and the primary amine compound containing double bonds, and obtaining the required intermediate product.

[0129] In some embodiments, in the step 2), the primary amine compound containing double bonds includes at least one of an allyl amine and an acetamide.

[0130] In some embodiments, in the step 2), the p-hydroxybenzene compound containing hydrophilic groups and the paraformaldehyde are mixed in the organic alcohol, and then the primary amine compound containing double bonds is added for reflux reaction. Wherein, the organic alcohol includes butanol.

[0131] In some embodiments, in the step 2), the mixing temperature is 60-70°C (for example, 62°C, 64°C, 65°C, 67°C, or 68°C).

[0132] In some embodiments, in the step 2), the temperature of the reflux reaction is 120-130°C (for example, 122°C, 124°C, 125°C, 127°C, or 129°C), and the reflux reaction time is 6-8h (for example, 7h).

[0133] In some embodiments, in the step 2), butanol is added to the reaction kettle, and then the hydrophilic group-containing p-hydroxybenzene compound, paraformaldehyde, and the primary amine compound containing a double bond are sequentially added under stirring, the temperature is raised to 60-70°C, the primary amine compound containing a double bond is slowly added, the temperature is raised to 120-130°C for reflux reaction for 6-8h, and then the intermediate product is obtained after filtration.

[0134] In this application, the hydrophilic group-containing p-hydroxybenzene compound, paraformaldehyde, and the primary amine compound containing a double bond react to obtain an intermediate product, which is an allyl-containing benzoxazine. Since the intermediate product contains an oxazine ring, the oxazine ring contains an active group with a lone pair of electrons, which can form a coordination compound with H+ in the acid solution to produce chemical adsorption, stabilize H+ in the acid solution, thereby reducing the consumption rate of H+, achieving the effect of slow release of H+, and further achieving remote deep acidification, solving the deep penetration modification problem of carbonate reservoirs.

[0135] In some embodiments, in the step 3), the mass ratio of the preliminary sample product, the intermediate product, the cationic monomer, the initiator, and the water is 7-17:8-15:2-5:0.2-1:70-85. That is, in the step 3), the mass fraction of the preliminary sample product is 7-17 parts (for example, 8 parts, 10 parts, 12 parts, or 15 parts), the mass fraction of the intermediate product is 8-15 parts (for example, 9 parts, 10 parts, 12 parts, or 14 parts), the mass fraction of the cationic monomer is 2-5 parts (for example, 2.5 parts, 3 parts, 4 parts, or 4.5 parts), the mass fraction of the initiator is 0.2-1 parts (for example, 0.3 parts, 0.5 parts, 0.8 parts, or 0.9 parts), and the mass fraction of the water is 70-85 parts (for example, 72 parts, 75 parts, 78 parts, 80 parts, or 82 parts).

[0136] In some embodiments, in the step 3), the cationic monomer includes at least one of hexadecylmethyldiallylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, and methacryloylpropyltrimethylammonium chloride; and the initiator includes at least one of ammonium persulfate, potassium persulfate, and azobis (isobutylamidine) hydrochloride.

[0137] In some embodiments, in the step 3), the reaction temperature is 60-90°C (for example, 65°C, 70°C, 75°C, 80°C, or 85°C), and the reaction time is 3-5h (for example, 4h).

[0138] In some embodiments, in step 3), water, the intermediate product, the preliminary sample product, and the cationic monomer are added into a reaction kettle, and stirred thoroughly and heated to 60-90°C, then the initiator is slowly added dropwise, and the reaction is carried out for 3-5 hours, and after drying, the acidizing biological gel retarding agent is obtained.

[0139] In the present application, the biological gel retarding agent is a product obtained by cross-linking the preliminary sample product and the intermediate product under the action of the cationic monomer and the initiator at 60-90°C; the product can enhance the retarding effect of the acidizing retarding agent, in addition, the intermediate product and the preliminary sample product both have good temperature resistance, which can further improve the temperature resistance of the acidizing biological gel retarding agent, so that the formed acid liquid system has good temperature resistance, retarding property, drag reduction property, and low damage property. The cationic monomer and the initiator can be cross-linked as cross-linking agents.

[0140] Generally, the acidizing biological gel retarding agent is a white solid.

[0141] Some embodiments of the second aspect of the present application provide an acidizing biological gel retarding agent, which is prepared by the preparation method of the acidizing biological gel retarding agent.

[0142] According to the preparation method of the acidizing biological gel retarding agent of the present application, an acidizing biological gel retarding agent with excellent performance can be prepared, and the preparation process is environmentally friendly, simple, and easy to operate.

[0143] Some embodiments of the third aspect of the present application provide an application of an acidizing biological gel retarding agent as an acidizing fracturing fluid in the development of oil and gas reservoir formations, wherein the acidizing biological gel retarding agent is the acidizing biological gel retarding agent of the second aspect of the present application.

[0144] The present application does not limit the specific components of the acidizing fracturing fluid, as long as the acidizing fracturing fluid contains the acidizing biological retarding agent described above.

[0145] In some embodiments, the acidizing fracturing fluid comprises the following components by mass percentage: hydrochloric acid 15%-20% (for example, 16% or 18%), acidizing biological gel retarding agent 2%-5% (for example, 3% or 4%), fluorocarbon cleanup additive 0.5%-2% (for example, 0.8%, 1%, 1.2%, 1.5%, or 1.8%), aldehyde ketone amine condensate corrosion inhibitor 1%-3% (for example, 1.2%, 1.5%, 2.0%, 2.5%, or 2.8%), iron ion stabilizer 0.5%-2% (for example, 0.8%, 1%, 1.2%, 1.5%, or 1.8%), cationic surfactant 0-0.4% (for example, 0.1%, 0.2%, 0.3%, or 0.35%), and the balance is water.

[0146] In some embodiments, the fluorocarbon cleanup additive includes a quaternary ammonium salt cationic fluorocarbon surfactant and / or an ethoxylated nonionic fluorocarbon surfactant; the aldehyde ketone amine condensate corrosion inhibitor is formed by aldehyde ketone amine condensation with a molecular weight less than 10 million.

[0147] The present application does not limit the type of iron ion stabilizer, and the iron ion stabilizer commonly used in the art can be used. Exemplarily, in some embodiments, the iron ion stabilizer includes a CT1-7 reducing agent.

[0148] In some embodiments, the acid fracturing fluid has a viscosity less than 45 mPa·s at 25℃, a retardation rate of 81.13% or more at 120℃, and a corrosion rate less than 2 g / (m2·h).

[0149] In some embodiments, the acidizing biogel retarder is suitable for acidizing treatment of high-temperature carbonate reservoirs with a reservoir temperature of 120℃ or more.

[0150] The present application does not limit the preparation process of the acid fracturing fluid, and as an example, the preparation method of the acid fracturing fluid can include the following steps:

[0151] S1: adding the acidizing biogel retarder to hydrochloric acid with a mass concentration of 15-20%, stirring thoroughly, and standing for 2-4 hours;

[0152] S2: sequentially adding the aldehyde ketone amine condensate corrosion inhibitor, the fluorocarbon cleanup additive, and the iron ion stabilizer, and stirring uniformly at room temperature to obtain the acid fracturing fluid.

[0153] The preparation method of the acid fracturing fluid of the present application is simple, easy to control, and conducive to large-scale industrial application.

[0154] The present application is further illustrated by specific examples and comparative examples. In the following examples, the materials, reagents, etc. can be obtained by commercial means unless otherwise specified; or the reagents and materials involved can be obtained by conventional synthesis methods. In the following examples, the sphingan is obtained by laboratory fermentation of Sphingomonas sp. WG, and the accession number of Sphingomonas sp. WG is CCTCC No: M2013161. The obtained sphingan has a viscosity average molecular weight of 10 million Da-2000 million Da.

[0155] The aldehyde ketone amine condensate corrosion inhibitor is CT1-3D (purchased from China Petroleum and Natural Gas Group Co., Ltd.); the fluorocarbon cleanup additive is CT5-12A (purchased from China Petroleum and Natural Gas Group Co., Ltd.); and the iron ion stabilizer is CT1-7 (purchased from China Petroleum and Natural Gas Group Co., Ltd.).

[0156] Example 1

[0157] A preparation method of a biological gel retarder for acidification, as shown in FIG. 1, comprises the following steps:

[0158] S1: 5mg / mL sphingan mother liquor 30mL and 0.1mol / L KOH solution and 0.5mo / L HCl solution were prepared respectively; the sphingan mother liquor was mixed with the KOH solution, and the amount of KOH solution added was adjusted so that the final concentration of the alkali solution reached 0.01mol·L-1, and vortexed to be uniform to obtain a mixed solution; the mixed solution was placed in a constant temperature shaking water bath at 120rpm, and reacted at 110℃ for 2h; after the reaction was completed, the first reaction product was immediately taken out, placed in ice water until cooled to room temperature, the pH value of the sample was adjusted to about 7.0 using 0.5mol / L HCl solution, 4 times the volume of 95%(volume fraction) ethanol solution was added, vortexed at 1200rmp, and then alcohol precipitation was carried out for 4h to separate layers, high-speed centrifugation was carried out for 20min, the supernatant was taken, vacuum drying was carried out for 24h until completely dried to constant mass, and the dried product was obtained as a preliminary sample product of the biological gel retarder for acidification;

[0159] S2: 40g of butanol was added to a reaction kettle, 45g of sodium p-hydroxybenzenesulfonate and 15g of polyformaldehyde were sequentially added, the temperature was raised to 60℃, 14g of allylamine was slowly added, after completion, the temperature was raised to 120℃ to reflux, and the reaction was continued for 7h, the reaction was stopped and filtered to obtain an intermediate product;

[0160] S3: 75g of water, 10g of the intermediate product, 8g of the preliminary sample, 2g of cetyl methyldiallyl ammonium chloride were added to a reaction kettle, stirred thoroughly and the temperature was raised to 60℃, then 1g of initiator ammonium persulfate was slowly added dropwise, the reaction was carried out for 3h, the reaction was stopped and dried, and a white solid was obtained as the biological gel retarder for acidification.

[0161] Example 2

[0162] A preparation method of a biological gel retarder for acidification, as shown in FIG. 1, comprises the following steps:

[0163] S1: 1 mg / mL sphingan mother liquor 30 mL and 0.2 mol / L NaOH solution and 0.5 mol / L HCl solution were prepared respectively; the sphingan mother liquor was mixed with the NaOH solution, so that the final concentration of the NaOH solution in the mixed solution reached 0.04 mol / L, and the mixture was vortexed until uniform to obtain a mixed solution; the mixed solution was placed in a constant temperature shaking water bath at a rotation speed of 120 rpm, and reacted at 110℃ for 2 h; after the reaction was completed, the sample was immediately taken out and placed in ice water until it cooled to room temperature; the pH value of the sample was adjusted to about 7.0 using 0.5 mol / L HCl solution, 4 times the volume of 95% ethanol solution was added, and after vortexing, the sample was alcohol precipitated for 4 h to separate layers, high-speed centrifugation was performed for 20 min, the supernatant was taken, vacuum drying was performed for 24 h until complete drying to constant mass to obtain a preliminary sample;

[0164] S2: 40 g of butanol was added to a reaction kettle, followed by the addition of 45 g of methyl p-hydroxybenzoate sodium and 30 g of polyformaldehyde, the temperature was raised to 60℃, and then 30 g of allylamine was slowly added, after completion, the temperature was raised to 120℃ to reflux, and the reaction was continued for 7 hours, after the reaction was completed, filtration was performed to obtain an intermediate product;

[0165] S3: 75 g of water, 10 g of the intermediate product, 10 g of the preliminary sample, and 3 g of cetyl methyldiallyl ammonium chloride were added to a reaction kettle, and the mixture was stirred and heated to 60℃, then 1 g of initiator ammonium persulfate was slowly added dropwise, the reaction was carried out for 3 hours, and after the reaction was completed, drying was performed to obtain a white solid, which was the acidizing biological gel retarder.

[0166] Example 3

[0167] An acid fracturing fluid comprises the following components in the following mass percentage:

[0168] The acid fracturing fluid comprises 3.0% of the biological gel retarder, 3% of the aldehyde ketone amine condensate corrosion inhibitor CT1-3D, 1% of the fluorocarbon cleanup additive CT5-12A, 2% of the iron ion stabilizer CT1-7, 20% of hydrochloric acid, and the balance of water. The biological gel retarder is the acidizing biological gel retarder prepared in Example 1.

[0169] The preparation method of the acid fracturing fluid comprises the following steps:

[0170] S1, the acidizing biological gel retarder was added to hydrochloric acid, and the mixture was stirred and placed for 2-4 hours, so that the mass concentration of hydrochloric acid in the final acid solution reached 15%;

[0171] S2: The aldehyde ketone amine condensate corrosion inhibitor, the fluorocarbon cleanup additive, and the iron ion stabilizer were added in sequence, and the mixture was stirred uniformly at room temperature, and then the acid fracturing fluid was obtained after standing.

[0172] Example 4

[0173] An acid fracturing fluid comprises the following components in the following mass percentage:

[0174] Biological gel retarder 3.0%, aldehyde ketone amine condensate type corrosion inhibitor CT1-3D 3%, fluorocarbon type cleanup additive CT5-12A 1%, iron ion stabilizer CT1-7 2%, hydrochloric acid 15%, and the balance of water. The biological gel retarder is prepared by the method of Example 1.

[0175] The acid fracturing fluid is prepared by the method of Example 3.

[0176] Example 5

[0177] An acid fracturing fluid comprises the following components in the following mass percentage:

[0178] Biological gel retarder 3.0%, aldehyde ketone amine condensate type corrosion inhibitor CT1-3D 3%, fluorocarbon type cleanup additive CT5-12A 1%, iron ion stabilizer CT1-7 2%, hydrochloric acid 20%, and the balance of water. The biological gel retarder is prepared by the method of Example 2.

[0179] The acid fracturing fluid is prepared by the method of Example 3.

[0180] Example 6

[0181] An acid fracturing fluid comprises the following components in the following mass percentage:

[0182] Biological gel retarder 3.0%, aldehyde ketone amine condensate type corrosion inhibitor CT1-3D 3%, fluorocarbon type cleanup additive CT5-12A 1%, iron ion stabilizer CT1-7 2%, hydrochloric acid 15%, and the balance of water. The biological gel retarder is prepared by the method of Example 2.

[0183] The acid fracturing fluid is prepared by the method of Example 3.

[0184] Comparative Example 1

[0185] An acid fracturing fluid comprises the following components in the following mass percentage:

[0186] Aldehyde ketone amine condensate type corrosion inhibitor CT1-3D 3%, fluorocarbon type cleanup additive CT5-12A 1%, iron ion stabilizer CT1-7 2%, hydrochloric acid 20%, and the balance of water.

[0187] The preparation method of the acid fracturing fluid comprises the following steps:

[0188] S1, add the aldehyde ketone amine condensate type corrosion inhibitor, the fluorocarbon type cleanup additive, and the iron ion stabilizer into the hydrochloric acid in sequence, and stir uniformly at room temperature,

[0189] S2, standing for 2-4 hours, so that the mass concentration of hydrochloric acid in the final acid liquid reaches 15%, to obtain the acid liquid system of the present comparative example.

[0190] The difference between the present comparative example and example 1 is that the acidizing fracturing fluid does not contain acidizing biogel retarder, and in the preparation method, no acidizing biogel retarder is added in step S1.

[0191] Test example

[0192] 1. Test of acetyl content: the experimental principle is that the sample containing acetyl can generate a complex that can undergo condensation reaction with FeCl3-HCl solution under acidic conditions in alkaline hydroxylamine solution, and the colored compound after reaction can be detected at 540 nm, and the absorbance value is linearly related to the acetyl content, so that the acetyl content in the sample can be determined. The specific test method is as follows.

[0193] (1) Determination of standard curve

[0194] Prepare 1 g / L acetylcholine chloride standard solution, and take 0, 0.2, 0.4, 0.6, 0.8, and 1.0 mL into a test tube with a stopper, respectively. All test samples are diluted to 1 mL with ultrapure water, 2 mL of alkaline hydroxylamine solution is added first, vortexed and mixed, then placed at room temperature for 5 min, then 1 mL of 4 mol / L HCl solution is added, vortexed for 1 min, then 1 mL of 0.37 mol / L FeCl3-HCl solution is added, fully mixed, and the absorbance value is measured at 540 nm, and the absorbance value corresponding to the standard solution concentration is plotted to obtain the standard curve. Figure 2 shows the standard curve of the acetyl content test.

[0195] (2) Determination of acetyl content of experimental group

[0196] Take 1 mL of the sample solution of sphingosine gel (sphingosine gel and the first reaction product in examples 1 and 2) into a test tube, and perform the experiment according to the method in step (1). The acetyl content is calculated using the standard curve. The test results are shown in Table 1.

[0197] The calculation of the acetyl content in the sphingosine gel sample is shown in formula 2-3.

[0198] In formula 2-3, M is the acetyl content calculated by the standard curve; C0 is the concentration of the sphingosine gel sample solution; and V is the volume of the sphingosine gel sample solution.

[0199] 2. Viscosity test of acidizing fracturing fluid: the viscosity of the acidizing fracturing fluid in examples 3-6 was tested using a rheometer, and the results are shown in Table 2.

[0200] 3. The rate reduction test of acid fracturing fluid: the rate reduction performance of the acid fracturing fluid in Examples 3-6 was tested by using the standard test of NB / T 14003.2-2016; the rate reduction curves of the acid fracturing fluid were shown in Figures 3-6, and the rate reduction rates were shown in Table 2.

[0201] 4. The rate control test of acid fracturing fluid: the acid concentration-time relationship of the acid fracturing fluid in Examples 3-6 and the hydrochloric acid solution with a mass concentration of 20% was tested at 120°C, and the results were shown in Figure 7. The rate control test results of the acid fracturing fluid were shown in Table 2.

[0202] 5. The corrosion inhibition rate test of acid fracturing fluid: under the conditions of a temperature of 120°C and a corrosion time of 4h, the corrosion inhibition rate and the average corrosion rate of the acid fracturing fluid provided by Examples 3-6 and Comparative Example 1 and the hydrochloric acid with a mass concentration of 15% and 20% on N80 steel sheets were tested under the same operating conditions, the corrosion inhibition rate test results were shown in Table 2, and the average corrosion rate test results were shown in Table 3.

[0203] Table 1: The vinyl content of the sphingosine gel and the first reaction product in Examples 1-2

[0204] Table 2: The related properties of the acid fracturing fluid in Examples 3-6

[0205] Table 3: The average corrosion rate of the acid fracturing fluid in each example, comparative example and blank group

[0206] According to Figure 7, when the reaction time is 60min, the 20% HCl solution is almost completely consumed, the acid-rock reaction rate is extremely fast, and the rate control rate is 0.33%; according to Tables 2 and 3, the acid liquid system provided by the application has more excellent effect; among them, the reaction rate of the acid liquid system of Examples 3-6 is slow, and the rate control rates are 78.88%, 81.71%, 78.62% and 85.32% respectively, which can meet the needs of field acidizing construction. The acid liquid system provided by the application has a low acid-rock reaction speed, can effectively improve the effective action distance of the acid liquid, can significantly improve the acid-etched fracture conductivity, and can make the fracture be uniformly etched.

[0207] According to Table 3, the average corrosion rate of the steel sheet by the acid liquid system in Examples 3-6 is less than 2g / (m 2(h). The average corrosion rate of the acid systems provided in Examples 3-4 was approximately 0.12% of the average corrosion rate of a 15% hydrochloric acid solution; the average corrosion rate of the bio-adhesive acid system provided in Examples 5-6 was only about 0.16% of the average corrosion rate of a 20% hydrochloric acid solution, significantly lower than the average corrosion rate of the hydrochloric acid solution. Therefore, the acid systems provided in Examples 3-6 exhibit significant corrosion inhibition effects, all exceeding the first-level standard required by the "Test Methods and Evaluation Indicators for Acidizing Corrosion Inhibitors for Oilfields." This demonstrates that the acid systems provided in Examples 3-6 of this application can effectively reduce the corrosion rate of downhole tubing and equipment, extend their service life, and reduce maintenance and replacement costs.

[0208] The preferred embodiments and experimental verifications of this application have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of this application without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of this application through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection of this application.

Claims

1. A method for preparing an acidification bio-adhesive retarder, wherein, The preparation method includes the following steps: 1) Mix the bio-glue mother liquor and alkaline solution, shake to react and obtain the first reaction product, then precipitate with alcohol, centrifuge and dry to obtain the preliminary sample product; 2) A hydrophilic p-hydroxybenzene compound, paraformaldehyde, and a primary amine compound containing a double bond are mixed in an organic alcohol and subjected to reflux reaction. The reflux product is then filtered to obtain an intermediate product. 3) Mix the preliminary sample product, intermediate product, cationic monomer and water, add an initiator to react and obtain an acidification bio-adhesive retarder.

2. The method for preparing the acidification bio-adhesive retarder according to claim 1, wherein, In step 1), the bio-gum in the bio-gum mother liquor includes at least one of sphingosine gum, vesin gum, xanthan gum, and diter gum; the alkaline solution includes at least one of NaOH solution and KOH solution; and / or, In step 2), the hydrophilic group includes at least one of a carboxylic acid ester salt group and a sulfonate salt group; The p-hydroxybenzene compound includes at least one of sodium methylparaben, sodium ethylparaben, sodium propylparaben, and sodium p-hydroxybenzenesulfonate. The primary amine compounds containing double bonds include at least one of allylamine and acetamide; The organic alcohol includes butanol; and / or, In step 3), the cationic monomer includes at least one of hexadecylmethyldiallylammonium chloride, methacryloyloxyethyltrimethylammonium chloride, and methacryloylpropyltrimethylammonium chloride; The initiator includes at least one of ammonium persulfate, potassium persulfate, and azobisisobutylamidine hydrochloride.

3. The method for preparing the acidification bio-adhesive retarder according to claim 1 or 2, wherein, In step 1), the mass ratio of the bio-adhesive mother liquor to the alkaline solution is 5–12:2–5; and / or, In step 1), the oscillation reaction is carried out at a temperature of 90–120°C.

4. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-3, wherein, In step 1), the mass-volume concentration of bio-gum in the bio-gum mother liquor is 3-6 mg / mL; the concentration of the alkaline solution is 0.1-0.2 mol / L.

5. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-4, wherein, In step 1), the bio-adhesive mother liquor and the alkaline solution are mixed by vortexing.

6. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-5, wherein, In step 1), the viscosity-average molecular weight of the bio-adhesive is 1 million Da to 20 million Da.

7. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-6, wherein, In step 1), the bio-gum in the bio-gum mother liquor is prepared by a preparation method including the following steps: The production strain is inoculated into a seed culture medium for cultivation, and then the cultured production strain is inoculated into a fermentation culture medium for fermentation to obtain the fermentation broth. The fermentation broth of the bacteria was subjected to alcohol precipitation. The precipitate obtained by alcohol precipitation was then subjected to filtration, washing, and freeze-drying to obtain biogel.

8. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-7, wherein, In step 1), the bio-gum mother liquor contains a main chain structure of bio-gum with a tetrasaccharide repeating unit structure, wherein the tetrasaccharides are D-glucose, D-glucuronic acid, L-rhamnose and L-mannose; the side chain structure of the bio-gum contains L-mannose and L-rhamnose.

9. The method for preparing the acidification bio-adhesive retarder according to claim 8, wherein, In step 1), the mass contents of D-glucose, D-glucuronic acid, L-rhamnose and L-mannose in the main chain structure of the bio-glue are 55%–60%, 2.0%–2.5%, 18%–33% and 6.0%–7.2%, respectively.

10. The method for preparing the acidification bio-adhesive retarder according to claim 8 or 9, wherein, In step 1), the side chain structure of the bio-adhesive in the bio-adhesive mother liquor contains at least one of acetyl, carboxyl, and pyruvate groups.

11. The method for preparing the acidification bio-adhesive retarder according to any one of claims 8-10, wherein, In step 1), the side chain structure of the bio-adhesive contains acetyl groups, wherein the content of the acetyl groups in the side chain structure of the bio-adhesive is 6.6% to 7.5%.

12. The method for preparing the acidification bio-adhesive retarder according to claim 2, wherein, In step 1), the bio-glue in the bio-glue mother liquor is sphingosine gum.

13. The method for preparing the acidification bio-adhesive retarder according to claim 12, wherein, In step 1), the sphingosine gum is a fermentation product of Sphingomonas sp. WG.

14. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-13, wherein, In step 1), the mass content of acetyl groups in the first reaction product or the preliminary sample product is 3% to 6%.

15. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-14, wherein, In step 2), the mass ratio of the hydrophilic p-hydroxybenzene compound, the paraformaldehyde, the primary amine compound containing double bonds, and the organic alcohol is 20-40:10-30:10-30:20-50. In step 3), the mass ratio of the preliminary sample product, the intermediate product, the cationic monomer, the initiator, and the water is 7-17:8-15:2-5:0.2-1:70-85.

16. The method for preparing the acidification bio-adhesive retarder according to any one of claims 1-15, wherein, In step 2), the mixing temperature is 60–70°C; the reflux reaction temperature is 120–130°C. In step 3), the reaction temperature is 60–90°C.

17. A bio-adhesive retarder for acidification, wherein, The bio-adhesive retarder is prepared by the method for preparing the bio-adhesive retarder for acidification according to any one of claims 1-16.

18. The application of a bio-gum retarder for acidizing as an acidizing fracturing fluid in oil and gas reservoir development, wherein, The acidification bio-adhesive retarder is the acidification bio-adhesive retarder according to claim 17.

19. The application of the acidizing bio-gum retarder according to claim 18 as an acidizing fracturing fluid in oil and gas reservoir development, wherein, The acidizing fracturing fluid comprises the following components by mass percentage: 15%–20% hydrochloric acid, 2%–5% bio-adhesive retarder for acidizing, 0.5%–2% fluorocarbon drainage aid, 1%–3% aldehyde-ketone-amine condensate corrosion inhibitor, 0.5%–2% iron ion stabilizer, 0%–0.4% cationic surfactant, and the balance being water.

20. The application of the acidizing bio-gum retarder according to claim 18 or 19 as an acidizing fracturing fluid in oil and gas reservoir development, wherein, The acidizing fracturing fluid is suitable for acidizing high-temperature carbonate reservoirs with reservoir temperatures above 120°C.

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