CN114181683B

CN114181683B - Hydrophobic surface modified nano plugging agent and fracturing fluid containing same

Info

Publication number: CN114181683B
Application number: CN202110766759.0A
Authority: CN
Inventors: 郭彤楼; 雷炜; 谭佳; 潘宝风; 刘多容; 兰林; 王文耀; 杨东梅; 李志鑫; 李洪波
Original assignee: China Petroleum and Chemical Corp; Sinopec Southwest Oil and Gas Co
Current assignee: China Petroleum and Chemical Corp; Sinopec Southwest Oil and Gas Co
Priority date: 2021-07-07
Filing date: 2021-07-07
Publication date: 2023-03-31
Anticipated expiration: 2041-07-07
Also published as: CN114181683A

Abstract

The invention provides a hydrophobic surface modified nano plugging agent and a fracturing fluid containing the same, wherein the hydrophobic surface modified nano plugging agent is prepared by the following preparation method: 1) Adding hydrophobic nano silicon dioxide, water and citric acid into a container in sequence, and uniformly mixing to obtain a first mixture; 2) Adding ethylene glycol into the first mixture at the temperature of 60-80 ℃, and uniformly mixing to obtain a second mixture; 3) Adding urea and a fluorocarbon surfactant into the second mixture at the temperature of between 60 and 80 ℃, and uniformly mixing to obtain a third mixture; 4) Reacting for 4 to 6 hours at the temperature of between 60 and 80 ℃ to prepare the hydrophobic surface modified nano plugging agent.

Description

Hydrophobic surface modified nano plugging agent and fracturing fluid containing same

Technical Field

The invention provides a hydrophobic surface modified nano plugging agent, in particular to guanidine gum fracturing fluid containing the hydrophobic surface modified nano plugging agent.

Background

The compact sandstone reservoir in the west China has the characteristics of small porosity, low permeability and strong heterogeneity, and the sand adding difficulty in fracturing modification construction is high. At present, the conventional guanidine gum fracturing fluid is mainly used in fracturing modification, and has serious damage to a rock core matrix of a reservoir, the damage rate reaches 30 percent, so that the liquid is difficult to flow back after construction, and the gas production effect of part of wells is not ideal. Three major factors that cause matrix damage include debris in the guanidine gum fracturing fluid, adsorption retention of the fracturing fluid, and water lock damage. The residue content of the conventional guanidine gum fracturing fluid is more than 400mg/L, and the residue can directly block the pore throat, so that the seepage channel is reduced; the guanidine gum in the fracturing fluid has adsorption retention damage in a rock porous medium, and accounts for more than 60% of the total damage amount; the water lock damage causes the fracturing fluid to be soaked into a reservoir stratum, the flowback is difficult, the flowback rate is low, and the yield after the fracturing is influenced. Aiming at the three damage factors, the damage to a reservoir is generally reduced at home and abroad by reducing the concentration of guanidine gum and adding a nano plugging agent and a waterproof locking agent into guanidine gum fracturing fluid.

According to data research, the existing nano plugging agent for fracturing fluid is hydrophilic, and compared with the conventional guanidine gum fracturing fluid, the damage rate is not obviously reduced, so that the development benefit of a compact reservoir is severely restricted.

Therefore, the development of a fracturing fluid capable of reducing damage is urgently needed to meet the technical requirement of fracturing modification of more low-permeability tight gas reservoirs.

Disclosure of Invention

The invention provides a hydrophobic surface modified nano plugging agent, which is prepared by the following preparation method:

1) Adding hydrophobic nano silicon dioxide, water and citric acid into a container in sequence, and uniformly mixing to obtain a first mixture;

2) Adding ethylene glycol into the first mixture at the temperature of 60-80 ℃, and uniformly mixing to obtain a second mixture;

3) Adding urea and a fluorocarbon surfactant into the second mixture at the temperature of between 60 and 80 ℃, and uniformly mixing to obtain a third mixture;

4) Reacting for 4 to 6 hours at the temperature of between 60 and 80 ℃ to prepare the hydrophobic surface modified nano plugging agent.

In one embodiment, the hydrophobic nanosilica has a particle size of 3 to 5nm.

In one embodiment, the hydrophobic nanosilica is prepared by the following steps:

preparing hydrophobic nano-silica from hydrophilic silica and chlorosilane or hexamethyldisilazane at the mass ratio of 1.

In one embodiment, in step 2), stirring is carried out at 60 to 80 ℃ for 4 to 6 hours, and then standing is carried out at 60 to 80 ℃ for a constant temperature of 18 to 20 hours.

In one embodiment, the content of the hydrophobic nanosilica is from 1% to 2% by mass, taken as 100% by mass of the total system; the content of the citric acid is 0.5-1.5%, the content of the ethylene glycol is 2.6-5.2%, the content of the urea is 5-10%, and the content of the fluorocarbon surfactant is 3-5%.

In one embodiment, the fluorocarbon surfactant is sodium perfluorononenoxybenzenesulfonate.

The second invention provides a nano-plugging type guanidine gum fracturing fluid, the pH value of the fracturing fluid is 9-10, the fracturing fluid comprises a bactericide, a thickening agent, a cleanup additive, a clay stabilizer, a pH regulator, the hydrophobic surface modified nano-plugging agent as in any one of the first invention, a cross-linking agent and the balance of water, wherein the mass concentration of the bactericide is 0.3-0.5%, the mass concentration of the thickening agent is 0.3-0.6%, the mass concentration of the cleanup additive is 0.3-0.5%, the mass concentration of the clay stabilizer is 0.3-0.5%, the mass concentration of the hydrophobic surface modified nano-plugging agent is 0.3-0.5%, and the mass concentration of the cross-linking agent is 0.3-0.6%, based on 100% of the mass of the water.

In one embodiment, the biocide is at least one of formaldehyde, glutaraldehyde and dodecyltrimethylammonium chloride.

In one embodiment, the thickening agent is hydroxypropyl guar and/or carboxymethyl hydroxypropyl guar.

In one embodiment, the cleanup additive is a polyoxyethylene amine ether and/or a polyoxyethylene fatty alcohol ether.

In one embodiment, the clay stabilizer is a trimethyl alkylammonium salt and/or dodecyl trimethyl ammonium chloride.

In one embodiment, the trimethyl alkyl ammonium salt is selected from at least one of trimethyl methyl ammonium salt, trimethyl hydroxyethyl ammonium salt and trimethyl propenyl ammonium salt.

In one embodiment, the pH adjusting agent is sodium carbonate and/or sodium hydroxide.

In one embodiment, the crosslinker is an organoboron crosslinker.

The invention has the beneficial effects that:

the fracturing fluid is a nano-plugging guanidine gum fracturing fluid, and a hydrophobic surface modified nano-plugging agent contained in the fracturing fluid can prevent a large amount of liquid from entering a reservoir matrix in construction to reduce damage.

Compared with a comparative example, the damage of the nano plugging type guanidine gum fracturing fluid to the matrix of the compact sandstone reservoir is obviously reduced, the damage rate is less than 15%, and the damage reduction rate reaches more than 50%.

Detailed Description

The present invention is further illustrated by the following examples, which are intended to be purely exemplary of the invention and are not to be construed as limiting the invention in any way.

Unless otherwise specified, all of the above chemicals are commercially available.

Hydrophobic nano-silica was purchased from shanghai river chemical ltd.

Preparation of hydrophobic surface modified nano plugging agent

Example 1

The total amount is 100g. 2g of 3-5nm hydrophobic nano-silica is put into a three-necked flask containing 76.3g of distilled water and stirred, 1.5g of citric acid is added, 5.2g of ethylene glycol is added after the mixture is heated to 60 ℃, the mixture is stirred for 4 hours at 60 ℃, then the mixture is kept stand at 60 ℃ and kept at a constant temperature for 18 hours, 10g of urea and 5g of sodium perfluorononenyloxy benzene sulfonate as a fluorocarbon surfactant are added at 60 ℃, the mixture is uniformly mixed, and the mixture is reacted for 4 hours at 60 ℃ to prepare the hydrophobic surface modified nano-plugging agent No. 1 which is a homogeneous milky white liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare an aqueous solution with the mass concentration of 0.3%, and the surface tension of the solution is determined to be 21.98mN/m, the foam height is 88mm and the half-life period is 54min according to the standard of Q/SH 1500 0029-2019 'fracturing material technical Specification'.

Example 2

The total amount is 100g. Putting 1g of 3-5nm hydrophobic nano-silica into a three-neck flask containing distilled water, stirring, adding 0.5g of citric acid, heating to 70 ℃, adding 2.6g of ethylene glycol, stirring for 5 hours at 70 ℃, standing at 70 ℃, keeping the temperature constant for 19 hours, adding 5g of urea and 3g of fluorocarbon surfactant perfluorononenoxybenzene sodium sulfonate at 80 ℃, uniformly mixing, and reacting for 5 hours at 70 ℃ to obtain the hydrophobic surface modified nano-blocking agent No. 2 which is a homogeneous milky liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare an aqueous solution with the mass concentration of 0.3%, and the surface tension of the solution is 21.12mN/m, the foam height is 90mm and the half-life period is 58min according to the standard of Q/SH 1500 0029-2019 fracturing material technical Specification.

Example 3

The total amount is 100g. Putting 1.5g of 3-5nm hydrophobic nano-silica into a three-necked flask filled with distilled water, stirring, adding 1g of citric acid, heating to 80 ℃, then adding 4g of ethylene glycol, stirring for 6h at 80 ℃, then standing at 80 ℃, keeping the temperature constant for 20h, then cooling to 70 ℃, adding 8g of urea and 4g of sodium perfluorononenoxybenzenesulfonate as a fluorocarbon surfactant, uniformly mixing, heating to 80 ℃, and reacting for 6h at 80 ℃ to obtain the hydrophobic surface modified nano-plugging agent No. 3 which is a homogeneous milky white liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare an aqueous solution with the mass concentration of 0.3%, and the surface tension of the solution is measured to be 20.87mN/m, the foam height is 92mm, and the half-life period is 64min according to the standard of Q/SH 1500 0029-2019 'fracturing material technical specification'.

Comparative example 1

The total amount is 100g. Putting 2g of 3-5nm hydrophobic nano-silica into a three-neck flask containing distilled water, stirring, adding 1.5g of acetic acid, heating to 60 ℃, adding 5.2g of ethanol, stirring for 4 hours at 60 ℃, keeping the temperature of 60 ℃ constant for 18 hours, adding 10g of urea and 5g of surfactant Tween 80 at 60 ℃, uniformly mixing, and reacting for 4 hours at 60 ℃ to obtain the hydrophobic surface modification nano-blocking agent No. 4 which is a white crystalline solid-liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare an aqueous solution with the mass concentration of 0.3%, and according to the standard of Q/SH 1500 0029-2019 fracturing material technical Specification, the surface tension of the solution is measured to be 27.21mN/m, the foam height is 40mm, and the half-life period is 25min.

Comparative example 2

The total amount is 100g. Putting 1g of 3-5nm hydrophobic nano-silica into a three-necked flask filled with distilled water, stirring, adding 0.5g of acetic acid, heating to 70 ℃, adding 2.6g of diethylene glycol, stirring for 5 hours at 70 ℃, keeping the temperature of 70 ℃ constant for 19 hours, adding 5g of urea and 3g of sodium dodecyl benzene sulfonate as a surfactant at 70 ℃, uniformly mixing, and reacting for 5 hours at 70 ℃ to obtain the hydrophobic surface modified nano-plugging agent No. 5, which is a cream white layered liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare an aqueous solution with the mass concentration of 0.3%, and the surface tension of the solution is measured to be 28.34mN/m, the foam height is 30mm and the half-life period is 20min according to the standard of Q/SH 1500 0029-2019 & ltfracturing material technical Specification & gt.

Comparative example 3

The total amount is 100g. Putting 1.5g of 3-5nm hydrophobic nano silicon dioxide into a three-necked flask filled with distilled water, stirring, adding 1g of acetic acid, heating to 80 ℃, adding 4g of polyvinyl alcohol, stirring for 6h at 80 ℃, keeping the temperature of 80 ℃ constant for 20h, adding 8g of urea and 4g of surfactant sodium hexadecyl sulfate at 80 ℃, uniformly mixing, and reacting for 6h at 80 ℃ to obtain the hydrophobic surface modified nano plugging agent 6#, which is a white viscous liquid product.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare a 0.3 mass percent aqueous solution, and the surface tension of the solution is measured to be 28.01mN/m, the foam height is 35mm and the half-life period is 22min according to the standard of Q/SH 1500 0029-2019 'fracturing material technical specification'.

Comparative example 4

The total amount is 100g. 2g of 3-5nm hydrophobic nano-silica is put into a three-neck flask containing distilled water and stirred, 1.5g of citric acid is added, 5.2g of diethylene glycol is added after the mixture is heated to 80 ℃, the mixture is stirred for 5 hours at 80 ℃, then the temperature of 80 ℃ is kept constant for 20 hours, 10g of melamine and 5g of fluorocarbon surfactant perfluorononenoxybenzene sodium sulfonate are added at 80 ℃, the mixture is uniformly mixed, the temperature is reduced to 60 ℃, and the mixture reacts for 6 hours at 60 ℃ to prepare the hydrophobic surface modified nano-plugging agent No. 7, which is a liquid product containing white insoluble substances.

0.3g of the prepared hydrophobic surface modified nano plugging agent is added into 100g of distilled water to prepare a 0.3 mass percent aqueous solution, and according to the standard of Q/SH 1500 0029-2019 'fracturing material technical specification', the surface tension of the solution is measured to be 28.59mN/m, the foam height is 15mm, and the half-life period is 18min.

Preparation of fracturing fluids

Example 4

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the stirring condition of 400 revolutions per minute, mixing 1.5g of formaldehyde and glutaraldehyde in a ratio of 1 to 10 as a bactericide, adding the bactericide into the water, uniformly stirring, continuously adding 1.5g of a thickening agent, namely hydroxypropyl guar gum, and continuously stirring until the hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene amine ether, 2.5g of clay stabilizer dodecyl trimethylamine chloride and 1.5g of hydrophobic surface modification nano plugging agent 2# into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

step 4, adding 0.5g of sodium carbonate into the second solution, stirring until the sodium carbonate is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 9;

and 5, adding 1.5g of an organic boron crosslinking agent (DongyngSporui petroleum engineering technology Co., ltd.) into the base fluid of the fracturing fluid, and uniformly stirring to obtain the fracturing fluid (or called as fracturing fluid gel).

Example 5

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the condition of stirring at 400 revolutions per minute, adding 1.5g of dodecyl trimethyl ammonium chloride serving as a bactericide into the water, uniformly stirring, continuously adding 2.0g of thickening agent hydroxypropyl guar gum, and continuously stirring until the hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene amine ether, 2.5g of clay stabilizer trimethyl propenyl ammonium salt and 1.5g of hydrophobic surface modification nano plugging agent 2# into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

step 4, adding 0.75g of sodium carbonate into the second solution, stirring until the sodium carbonate is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 9.5;

and 5, adding 2.0g of an organic boron crosslinking agent (DongyngSporui petroleum engineering technology Co., ltd.) into the base fluid of the fracturing fluid, and uniformly stirring to obtain the fracturing fluid (or called as fracturing fluid gel).

Example 6

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the stirring condition of 400 revolutions per minute, mixing 2.5g of formaldehyde and glutaraldehyde according to a ratio of 1 to 10 as a bactericide, adding the bactericide into the water, uniformly stirring, continuously adding 2.5g of thickener carboxymethyl hydroxypropyl guar gum, and continuously stirring until the carboxymethyl hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 4, adding 0.05g of sodium hydroxide into the second solution, stirring until the sodium hydroxide is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 9.5;

and 5, adding 2.5g of an organic boron crosslinking agent (DongyngSporui petroleum engineering technology Co., ltd.) into the base fluid of the fracturing fluid, and uniformly stirring to obtain the fracturing fluid (or called as fracturing fluid gel).

Example 7

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the condition of stirring at 400 revolutions per minute, adding 2.5g of dodecyl trimethyl ammonium chloride serving as a bactericide into the water, uniformly stirring, continuously adding 3.0g of thickening agent hydroxypropyl guar gum, and continuously stirring until the hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene amine ether, 2.5g of clay stabilizer trimethyl hydroxyethyl ammonium salt and 1.5g of hydrophobic surface modified nano plugging agent No. 2 into the first solution, and continuously stirring until the viscosity of the solution is not changed, so as to obtain a second solution;

step 4, adding 0.075g of sodium hydroxide into the second solution, stirring until the sodium hydroxide is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 10;

and 5, adding 3.0g of organic boron crosslinking agent (DongyngSporui petroleum engineering technology Co., ltd.) into the base fluid of the fracturing fluid, and uniformly stirring to obtain the fracturing fluid (or called as fracturing fluid gel).

Example 8

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the condition of stirring at 400 revolutions per minute, mixing 1.5g of formaldehyde and glutaraldehyde according to a ratio of 1 to 10 as a bactericide, adding the bactericide into the water, uniformly stirring, continuously adding 1.5g of thickener carboxymethyl hydroxypropyl guar gum, and continuously stirring until the carboxymethyl hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 1.5g of cleanup additive polyoxyethylene fatty alcohol ether, 1.5g of clay stabilizer dodecyl trimethylamine chloride and 1.5g of hydrophobic surface modification nano plugging agent No. 2 into the first solution, and continuously stirring until the viscosity of the solution is not changed, so as to obtain a second solution;

Example 9

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene fatty alcohol ether, 2.5g of clay stabilizer trimethyl methyl ammonium salt and 1.5g of hydrophobic surface modified nano plugging agent 2# into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

step 4, adding 0.75g of sodium carbonate into the second solution, stirring until the sodium carbonate is completely dissolved in the water, and standing for 30min to obtain a base fluid of the fracturing fluid, wherein the pH value of the base fluid is 9.5;

and 5, adding 1.75g of an organic boron crosslinking agent (DongyngSporui petroleum engineering technology Co., ltd.) into the base fluid of the fracturing fluid, and uniformly stirring to obtain the fracturing fluid (or called as fracturing fluid gel).

Example 10

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene fatty alcohol ether, 2.5g of clay stabilizer dodecyl trimethylamine chloride and 2.5g of hydrophobic surface modification nano plugging agent 2# into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

step 4, adding 1.0g of sodium carbonate into the second solution, stirring until the sodium carbonate is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 9.5;

Example 11

Step 1.25 ℃, 500g of tap water is placed in a 1000mL container;

step 2, under the condition of stirring at 400 revolutions per minute, adding 2.5g of dodecyl trimethyl ammonium chloride serving as a bactericide into the water, uniformly stirring, continuously adding 2.5g of thickening agent hydroxypropyl guar gum, and continuously stirring until the hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene fatty alcohol ether, 2.5g of clay stabilizer trimethyl propenyl ammonium salt and 2.5g of hydrophobic surface modification nano plugging agent 1#, and continuously stirring until the viscosity of the solution is not changed any more to obtain a second solution;

Example 12

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the stirring condition of 400 revolutions per minute, mixing 2.5g of formaldehyde and glutaraldehyde according to the proportion of 1 to 10 as a bactericide, adding the bactericide into the water, uniformly stirring, continuously adding 3.0g of thickener carboxymethyl hydroxypropyl guar gum, and continuously stirring until the carboxymethyl hydroxypropyl guar gum is completely dissolved in the water to obtain a first solution;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene fatty alcohol ether, 2.5g of clay stabilizer dodecyl trimethylamine chloride and 2.0g of hydrophobic surface modification nano plugging agent 3# into the first solution, and continuously stirring until the viscosity of the solution is not changed to obtain a second solution;

Example 13

Step 1.25 ℃, putting 500mL of tap water into a 1000mL container;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene fatty alcohol ether, 2.5g of clay stabilizer trimethyl propenyl ammonium salt and 2.5g of hydrophobic surface modification nano plugging agent 2# into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

step 4, adding 1.5g of sodium carbonate into the second solution, stirring until the sodium carbonate is completely dissolved in water, and standing for 30min to obtain a fracturing fluid base fluid, wherein the pH value of the fracturing fluid base fluid is 10;

Comparative example 5

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene amine ether and 2.5g of clay stabilizer dodecyl trimethylamine chloride into the first solution, and continuously stirring until the viscosity of the solution is not changed, so as to obtain a second solution;

Comparative example 6

Step 1.25 ℃, 500mL of tap water is placed in a 1000mL container;

step 2, under the condition of stirring at 400 revolutions per minute, mixing 1.5g of formaldehyde and glutaraldehyde according to a ratio of 1;

step 3, under the stirring state, sequentially adding 2.5g of cleanup additive polyoxyethylene amine ether, 2.5g of clay stabilizer dodecyl trimethylamine chloride and hydrophilic surface modification nano plugging agent (sold in the market) into the first solution, and continuously stirring until the viscosity of the solution is not changed any more, so as to obtain a second solution;

Comparative example 7

The hydrophobic surface-modified nano plugging agent used was prepared from comparative example 1, and the rest was the same as example 7.

Comparative example 8

The hydrophobic surface-modified nano plugging agent used was prepared from comparative example 2, and the rest was the same as example 7.

Comparative example 9

The hydrophobic surface-modified nano plugging agent used was prepared by comparative example 3, and the rest was the same as example 7.

Comparative example 10

The hydrophobic surface-modified nano plugging agent used was prepared from comparative example 4, and the rest was the same as example 7.

The fracturing fluid prepared by the embodiment and the comparative example is used for carrying out a damage performance evaluation experiment on the compact sandstone core, and the specific experimental conditions and requirements are as follows: the fracturing fluid gel samples of the embodiments and the comparative examples are respectively added into a high-temperature high-pressure filtration apparatus, the temperature is set to be 80 ℃, the pressure is set to be 3.5MPa, 300mL of filtrate is prepared, a compact sandstone natural core with the permeability of the same order of magnitude is selected, and the core permeability reduction rate before and after the filtrate damage is measured to be the core damage rate. The results of the fracturing fluid damage performance evaluation tests shown in table 1 were obtained through the above-described tests.

TABLE 1

Examples	Tight sandstone core damagePercent of damage/%)
		Example 4	13.22
Example 5	13.78
		Example 6	13.96
Example 7	14.35
		Example 8	12.97
Example 9	13.04
		Example 10	13.43
Example 11	14.21
		Example 12	14.52
Example 13	14.68
		Comparative example 5	30.01
Comparative example 6	25.14
		Comparative example 7	29.38
Comparative example 8	29.11
		Comparative example 9	28.76
Comparative example 10	28.34

It can be clearly seen from the experimental results in table 1 that the damage rates of the nano plugging type guanidine gum fracturing fluid prepared in the above embodiments of the present invention to the tight sandstone core are all less than 15%, and compared with the comparative examples 5 to 10, the damage reduction rate is more than 50%. Therefore, the nano plugging type guanidine gum fracturing fluid can be widely suitable for fracturing modification of various compact sandstone gas reservoirs.

While the invention has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes can be made without departing from the true spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation, material, composition of matter, and method to the essential scope and spirit of the present invention. All such modifications are intended to be included within the scope of the present invention as defined in the appended claims.

Claims

1. A hydrophobic surface modified nano plugging agent is prepared by the following preparation method:

2) Adding ethylene glycol into the first mixture at 60-80 ℃, and uniformly mixing to obtain a second mixture;

3) Adding urea and a fluorocarbon surfactant into the second mixture at 60-80 ℃, and uniformly mixing to obtain a third mixture;

4) Reacting for 4 to 6 hours at the temperature of between 60 and 80 ℃ to prepare the hydrophobic surface modified nano plugging agent;

the mass of the total system is taken as 100 percent, and the content of the hydrophobic nano silicon dioxide is 1 to 2 percent; the content of the citric acid is 0.5-1.5%, the content of the ethylene glycol is 2.6-5.2%, the content of the urea is 5-10%, and the content of the fluorocarbon surfactant is 3-5%.

2. The hydrophobic surface-modified nano blocking agent according to claim 1, wherein the hydrophobic nano silica has a particle size of 3 to 5nm.

3. The hydrophobic surface modified nano plugging agent according to claim 1, wherein the hydrophobic nano silica is prepared by the following steps:

the hydrophilic silica and chlorosilane or hexamethyldisilazane are prepared into hydrophobic nano-silica at 1700-1900 ℃ in a mass ratio of 1.

4. The hydrophobic surface-modified nano plugging agent according to claim 1, wherein in step 2), stirring is performed at 60 to 80 ℃ for 4 to 6 hours, and then standing is performed at 60 to 80 ℃ for a constant temperature of 18 to 20 hours.

5. The hydrophobic surface-modified nano blocking agent according to claim 1, wherein the fluorocarbon surfactant is sodium perfluorononenoxybenzene sulfonate.

6. A nano-plugging guanidine gum fracturing fluid with the pH value of 9 to 10 comprises a bactericide, a thickening agent, a cleanup agent, a clay stabilizer, a pH regulator, the hydrophobic surface modified nano-plugging agent as claimed in any one of claims 1 to 5, a cross-linking agent and the balance of water, wherein the mass concentration of the bactericide is 0.3 to 0.5 percent, the mass concentration of the thickening agent is 0.3 to 0.6 percent, the mass concentration of the cleanup agent is 0.3 to 0.5 percent, the mass concentration of the clay stabilizer is 0.3 to 0.5 percent, the mass concentration of the hydrophobic surface modified nano-plugging agent is 0.3 to 0.5 percent and the mass concentration of the cross-linking agent is 0.3 to 0.6 percent based on 100 percent of water.

7. The fracturing fluid of claim 6, wherein the biocide is at least one of formaldehyde, glutaraldehyde, and dodecyltrimethylammonium chloride.

8. The fracturing fluid of claim 6, wherein the viscosifying agent is hydroxypropyl guar and/or carboxymethyl hydroxypropyl guar; and/or

The cleanup additive is polyoxyethylene amine ether and/or polyoxyethylene fatty alcohol ether.

9. The fracturing fluid of claim 6, wherein the clay stabilizer is a trimethyl alkylammonium salt and/or dodecyl trimethyl ammonium chloride.

10. The fracturing fluid of claim 9, wherein the trimethyl alkyl ammonium salt is selected from at least one of trimethyl hydroxyethyl ammonium salt and trimethyl propenyl ammonium salt.

11. The fracturing fluid of any of claims 6 to 10, wherein the pH modifier is sodium carbonate and/or sodium hydroxide; and/or the crosslinking agent is an organoboron crosslinking agent.