阅读说明：本技术 一种用于压裂返排液重复配液的交联剂及其制备方法和应用 (Crosslinking agent for fracturing flow-back fluid repeated fluid and preparation method and application thereof ) 是由 吴亚 张科良 白海涛 陈刚 陈世军 蔡晴 于 2020-06-19 设计创作，主要内容包括：本发明公开一种用于压裂返排液重复配液的交联剂及其制备方法和应用,将乙二醇、正丁醇和硼酸,混合均匀,加热回流,分出产生的水,直到产生的水不再增加,冷却至室温,得到混合液；将混合液与聚乙烯亚胺混合,搅拌加热回流,同时分离出正丁醇,直到混合物成淡黄色液体,冷却至室温；然后加入多元醇,加热后冷却至室温,再加入氢氧化钠和乙二醛处理,室温搅拌得淡黄色油状物,即为超支化氨基硼交联剂。该交联剂合成工艺简单、易行,可用于压裂返排液重复配制压裂液,有效解决现有压裂返排液重复配制得到的压裂液不耐高温、抗剪切性能差以及返排液排放引起的环境污染。(The invention discloses a cross-linking agent for a fracturing flow-back fluid repeated fluid and a preparation method and application thereof, wherein glycol, n-butyl alcohol and boric acid are uniformly mixed, heated and refluxed, generated water is separated until the generated water is not increased any more, and cooled to room temperature to obtain a mixed solution; mixing the mixed solution with polyethyleneimine, stirring, heating and refluxing, simultaneously separating n-butanol until the mixture becomes light yellow liquid, and cooling to room temperature; and then adding polyol, heating, cooling to room temperature, adding sodium hydroxide and glyoxal for treatment, and stirring at room temperature to obtain a light yellow oily substance, namely the hyperbranched amino boron crosslinking agent. The cross-linking agent has simple and feasible synthesis process, can be used for repeatedly preparing the fracturing fluid from the fracturing flow-back fluid, and effectively solves the problems that the fracturing fluid obtained by repeatedly preparing the existing fracturing flow-back fluid is not high-temperature resistant and has poor shearing resistance and the environmental pollution caused by the discharge of the flow-back fluid.)

1. A cross-linking agent for a fracturing flow-back fluid repeating fluid is characterized by having the following chemical structure:

2. the method of preparing a cross-linking agent for a frac flowback fluid repeat fluid of claim 1, comprising the steps of:

step one, mixing ethylene glycol, n-butanol and boric acid uniformly, heating and refluxing, separating out generated water until the generated water is not increased any more, and cooling to obtain a mixed solution 1;

secondly, mixing the mixed solution 1 with polyethyleneimine to obtain a mixed solution 2, stirring, heating and refluxing, simultaneously separating n-butanol until the n-butanol is not distilled off to obtain a light yellow liquid, and cooling;

step three, adding polyalcohol into the yellowish liquid obtained in the step two, heating for reaction, and cooling to obtain a mixed solution 3 after the reaction is finished;

and fourthly, adding sodium hydroxide and glyoxal into the mixed solution 3, and uniformly stirring to obtain the hyperbranched amino boron crosslinking agent.

3. The method for preparing a cross-linking agent for a fracturing fluid-return fluid repeating fluid according to claim 2, wherein in the first step, the ethylene glycol is 48%, the n-butanol is 32%, and the boric acid is 20% by mass.

4. The preparation method of the cross-linking agent for the fracturing flow-back fluid repeating fluid as claimed in claim 2, wherein in the second step, the molecular weight of polyethyleneimine is 600 to 10000, and the addition amount of the polyethyleneimine is 30-60% of the mass of boric acid.

5. The preparation method of the cross-linking agent for the fracturing flow-back fluid repeating fluid as claimed in claim 2, wherein in the third step, the polyol is any one of pentaerythritol, dipentaerythritol and triethanolamine, and the addition amount of the polyol is 30-50% of the mass of the boric acid.

6. The method for preparing a cross-linking agent for a fracturing fluid flowback fluid repeating fluid according to claim 2, wherein in the third step, the heating temperature is 150 ℃ and the heating time is 1 hour.

7. The preparation method of the cross-linking agent for the fracturing flow-back fluid repeating fluid according to claim 2, wherein in the fourth step, the addition amount of sodium hydroxide is 30-80% of the mass of boric acid.

8. The use of the cross-linking agent of claim 1 in the preparation of a fracturing fluid using a frac flowback fluid.

Technical Field

The invention belongs to the field of oilfield chemistry, and particularly relates to a cross-linking agent for a fracturing flow-back fluid repeated fluid, and a preparation method and application thereof.

Background

Hydraulic fracturing is an economically viable technology in oil and shale gas development. However, hydraulic fracturing requires large amounts of fresh water and produces large amounts of fracturing waste water (about 5000m per well)³) Which contains high concentrations of salts, toxic metals/metalloids, radionuclides and various organic components, have a great impact on the environment. Water application and disposal has therefore become the most challenging problem for hydraulic fracturing. The fracturing fluid is returned to the ground surface, and the treatment problem of the fracturing fluid is urgently needed to be solved due to the complex composition, poor biodegradability and high treatment difficulty. The repeated liquid preparation of the fracturing flowback liquid can greatly reduce the using amount of underground water, save energy, reduce emission, reduce the water treatment cost and solve the problem of environmental pollution to a certain extent.

The cross-linked hydroxypropyl guar gum is a practical and feasible hydraulic fracturing fluid at present. Forest snow et al think that the composition and type of salt in the fracturing flow-back waste liquid have different degrees of influence on the characteristics of the prepared fracturing fluid by simulating different types and concentrations of brine (drilling fluid and completion fluid, 2013, 30 (2): 73-76). The Wu Xinmin group proposed that the residual cross-linking agent in the fracturing flowback fluid causes the viscosity of the base fluid of the repeatedly prepared fracturing fluid to be too high, and the recycling of the fracturing flowback fluid is influenced (drilling fluid and completion fluid, 2015, 32 (3): 81-85). In order to improve the temperature and shear resistance of the fracturing fluid and reduce the dosage of a thickening agent or a crosslinking agent, an organic boron crosslinking agent, an inorganic boron coating crosslinking agent, an over-crosslinking delayed boron crosslinking agent and the like are developed in succession, wherein Magnus Lgemah develops the tetraethylenepentamine boron crosslinking agent which can reduce the dosage of guar gum and enables the fracturing fluid prepared by clean water to resist shear at higher temperature (SPE 164118). However, the application of the complex-composition fracturing flowback fluid re-preparation system is not ideal.

Disclosure of Invention

In order to overcome the defects of the prior art and effectively solve the problems that the existing fracturing flow-back fluid repeated fluid is not high-temperature resistant and has poor anti-shearing performance and the environmental pollution caused by the discharge of the flow-back fluid, the invention provides a cross-linking agent for the fracturing flow-back fluid repeated fluid and a preparation method and application thereof.

The invention is realized by the following technical scheme:

a cross-linking agent for a fracturing flow-back fluid repeating fluid, the chemical structure of the cross-linking agent is as follows:

the preparation method of the cross-linking agent for the fracturing flow-back fluid repeated fluid comprises the following steps:

step one, mixing ethylene glycol, n-butanol and boric acid uniformly, heating and refluxing, separating out generated water until the generated water is not increased any more, and cooling to obtain a mixed solution 1;

secondly, mixing the mixed solution 1 with polyethyleneimine to obtain a mixed solution 2, stirring, heating and refluxing, simultaneously separating n-butanol until the n-butanol is not distilled off to obtain a light yellow liquid, and cooling;

step three, adding polyalcohol into the yellowish liquid obtained in the step two, heating for reaction, and cooling to obtain a mixed solution 3 after the reaction is finished;

and fourthly, adding sodium hydroxide and glyoxal into the mixed solution 3, and uniformly stirring to obtain the hyperbranched amino boron crosslinking agent.

The invention is further improved in that in the first step, the mass percentage of the ethylene glycol is 48%, the mass percentage of the n-butanol is 32%, and the mass percentage of the boric acid is 20%.

The invention is further improved in that in the second step, the molecular weight of the polyethyleneimine is 600 to 10000, and the addition amount of the polyethyleneimine is 30 to 60 percent of the mass of the boric acid.

The further improvement of the invention is that in the third step, the polyalcohol is any one of pentaerythritol, dipentaerythritol and triethanolamine, and the addition amount of the polyalcohol is 30-50% of the mass of the boric acid.

In a further development of the invention, in the third step, the heating is carried out at a temperature of 150 ℃ for a time of 1 hour.

The further improvement of the invention is that in the fourth step, the adding amount of the sodium hydroxide is 30-80% of the mass of the boric acid.

The cross-linking agent is applied to preparing fracturing fluid by utilizing the fracturing flow-back fluid.

Compared with the prior art, the invention has the following beneficial technical effects:

the crosslinking agent is a hyperbranched amino boron crosslinking agent, is different from the existing organic boron crosslinking agent, and is crosslinked with a fracturing fluid thickener hydroxypropyl guar gum to form a huge hyperbranched network structure, so that the degradation of gel molecules at high temperature is slowed, and the temperature resistance of the gel molecules is improved; meanwhile, the crosslinking agent has primary amine groups and secondary amine groups with strong reactivity and is easy to combine with high-valence metal ions, so that the coordination effect of the high-valence ions and the hydroxypropyl guar gum is shielded to a certain extent, the interference of the high-valence ions in the fracturing flow-back fluid on the crosslinking of the hydroxypropyl guar gum is prevented, and the salt resistance is improved. The temperature resistance and shear resistance tests of the fracturing flowback fluid repeated fluid show that in a crosslinking agent and hydroxypropyl guar gum fracturing fluid system containing the product, when the crosslinking ratio of a hydroxypropyl guar gum base fluid to the crosslinking agent is 100:0.4, the fracturing fluid jelly prepared by the fracturing flowback fluid has good hanging performance, and the jelly is at 80 ℃ for 170s^-1The viscosity is over 90 mPas after shearing for 70min, the viscosity of the gel breaking liquid after gel breaking is lower than 3.5 mPas, the residue amount of the gel breaking liquid is low, and the requirement of site construction can be met.

The invention takes boric acid, glycol, polyethyleneimine and polyalcohol as main raw materials to synthesize the hyperbranched amino boron fracturing flow-back fluid repeated fluid cross-linking agent, and the synthesis process is simple and easy to implement.

The hyperbranched amino boron crosslinking agent is used for repeatedly preparing fracturing flow-back fluid, so that the fracturing flow-back fluid can be repeatedly utilized, the economy is improved, and the environmental pollution is reduced.

Drawings

FIG. 1 is the chemical structure of the hyperbranched aminoboron crosslinker.

FIG. 2 is a schematic representation of boron tert-butoxide¹H NMR chart

FIG. 3 is a schematic representation of boron tert-butoxide¹³C NMR chart.

FIG. 4 is a cross-linking agent of hyperbranched aminoboron prepared in example 1¹H NMR chart.

FIG. 5 is an IR plot of the hyperbranched organoboron crosslinkers prepared in example 1.

FIG. 6 shows the fracturing fluid jelly formed in example 1 at 80 ℃ for 170s^-1Shear curve.

FIG. 7 shows the fracturing fluid jelly formed in example 2 at 80 ℃ for 170s^-1Shear curve.

FIG. 8 shows the fracturing fluid jelly formed in example 3 at 80 ℃ for 170s^-1Shear curve.

FIG. 9 is a graph comparing fracturing fluid jelly with tetraethylenepentamine boron crosslinker at 80 deg.C for 170s^-1Shear curve.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

Referring to fig. 1, a cross-linking agent for a fracturing fluid-return fluid repeat fluid has the following structural formula:

a cross-linking agent for a fracturing flow-back fluid repeating liquid is a hyperbranched amino boron cross-linking agent synthesized by using boric acid, ethylene glycol, polyethyleneimine, polyhydric alcohol and glyoxal as main raw materials, and the preparation steps are as follows:

step one, adding 48% of ethylene glycol, 32% of n-butyl alcohol and 20% of boric acid in a reactor according to mass percent, uniformly mixing, heating and refluxing, separating out generated water until the generated water is not increased any more, and cooling to room temperature to obtain a mixed solution 1;

step two, mixing the mixed solution 1 obtained in the step one with polyethyleneimine to obtain a mixed solution 2, stirring, heating and refluxing, simultaneously separating out n-butanol until the n-butanol is not distilled off to obtain a light yellow liquid, and cooling to room temperature;

thirdly, adding polyol into the yellowish liquid obtained in the second step, heating for 1 hour at 150 ℃, and cooling to room temperature to obtain a mixed solution 3;

and step four, adding sodium hydroxide and glyoxal into the mixed solution 3 obtained in the step three for treatment, uniformly stirring, and stirring at room temperature to obtain a light yellow oily substance, namely the hyperbranched amino boron crosslinking agent.

The molecular weight of the polyethyleneimine is 600 to 10000.

The addition amount of the polyethyleneimine is 30-60% of the mass of the boric acid.

The polyhydric alcohol is any one of pentaerythritol, dipentaerythritol and triethanolamine.

The addition amount of the polyhydric alcohol is 30-50% of the mass of the boric acid.

The adding amount of the sodium hydroxide is 30-80% of the mass of the boric acid.

The addition amount of the glyoxal is 0.5-2 times of the mass of the boric acid.

The cross-linking agent is applied to preparing fracturing fluid by utilizing the fracturing flow-back fluid.

Specifically, 0.3% of hydroxypropyl guar gum base liquid by mass fraction is prepared, 0.5% of cleanup additive by mass of hydroxypropyl guar gum base liquid, 0.5% of clay stabilizer by mass of hydroxypropyl guar gum base liquid, 0.1% of bactericide by mass of hydroxypropyl guar gum base liquid and 0.1% of pH regulator by mass of hydroxypropyl guar gum base liquid are added after the hydroxypropyl guar gum base liquid is completely swelled to obtain a mixture, and then the hydroxypropyl guar gum base liquid and the cross-linking agent are mixed and stirred uniformly according to the cross-linking ratio of 100:0.4 to form the fracturing fluid gel.

Wherein the cleanup additive is TOF-1, the clay stabilizer is KCl, the bactericide is CJSJ-3, and the pH regulator is Na₂CO₃。

The present invention is not limited by the following examples, and specific embodiments may be determined according to the technical solutions and practical situations of the present invention. The various chemical reagents and chemical articles mentioned in the invention are all the chemical reagents and chemical articles which are well known and commonly used in the prior art, unless otherwise specified; the percentages in the invention are mass percentages unless otherwise specified; the room temperature in the present invention is generally defined as 25 ℃.

The invention will now be further described with reference to the following examples: