CN113512414B - Delayed crosslinking type high-temperature-resistant low-friction-resistance aggravated guanidine gum fracturing fluid and application method thereof - Google Patents

Abstract

The invention discloses a delayed crosslinking type high-temperature-resistant low-friction-resistance aggravated guanidine gum fracturing fluid which comprises the following components in percentage by mass: 25-55% of composite weighting agent, 0.25-0.45% of multi-element modified guanidine gum, 0.05-0.1% of weighting auxiliary agent 1, 0.7-1.0% of weighting auxiliary agent 2, 0.3-0.5% of alkaline regulator, 0.3-0.4% of deoxidant, 0.3-0.5% of high-efficiency cleanup additive, 0.6-1.2% of delayed crosslinking agent, 0.02-0.1% of gel breaker and the balance of fresh water; the composite weighting agent consists of a weighting agent A and a weighting agent B according to a mass ratio of 1:3, wherein the weighting agent A is sodium lactate or potassium lactate, and the weighting agent B is potassium formate or potassium sulfate. The invention adopts the composite weighting agent to weight, thereby not only meeting the liquid performance requirement, but also reducing the liquid cost, and the density of the fracturing fluid is between 1.2 and 1.45g/cm ³ The range is adjustable; the high-temperature deep well fracturing construction requirement of 120-180 ℃ can be met through formula adjustment.

Description

Delayed cross-linking type anti-high temperature and low friction aggravated guar gum fracturing fluid and its application method

technical field

The invention relates to the technical field of oil and gas reservoir stimulation, in particular to a delayed cross-linked anti-high temperature and low friction aggravating guar gum fracturing fluid which can be applied to high temperature deep well reservoir stimulation and an application method thereof.

Background technique

Fracturing fluid is one of the keys to the stimulation of low-permeability reservoirs. With the continuous development of fracturing to deep wells and ultra-deep wells, fracturing fluid technology must face difficult challenges. For deep wells with high temperature, high pressure and abnormal fracture pressure , Ultra-deep well reservoirs, due to the development of tight oil and gas reservoirs, strong tectonic stress, high formation pore pressure, serious reservoir damage, high formation fracture pressure and fracture extension pressure, etc., the surface construction pressure will be too high, and some even The construction has to be terminated because the bearing capacity of the ground equipment is exceeded, which also puts forward new and higher technical requirements for the fracturing fluid.

Weighted fracturing fluid technology is recognized as one of the effective means to reduce construction pressure and reduce construction risks. The pressure of the liquid column is increased by increasing the density of the fracturing fluid by the weighting agent, thereby reducing the construction pressure at the wellhead, and achieving the purpose of fracturing the reservoir and extending the fracture. So far, the weighted fracturing fluid technology has the longest application time and the widest application range is the weighted guar gum fracturing fluid system. According to literature research and application reports: many experts and scholars believe that the technical advantages and disadvantages of the system coexist through laboratory experiments and field application studies, and further research is needed. Ordinary guar gum weighted fracturing fluid has good temperature resistance, but its shortcomings such as high residue content, difficult to control crosslinking time, large pipeline friction, and poor shear resistance cannot be ignored; secondly, some modified guanidine The rubber fracturing fluid significantly reduces the residue content, but its temperature resistance and shear resistance are affected, the operating temperature is limited, and the compatibility with weighting agents is poor, and it cannot meet the fracturing construction requirements of high temperature, high pressure, and deep well reservoirs. .

At present, relevant enterprises at home and abroad have also carried out some research on fracturing fluids and achieved certain results, such as "A Recipe for Weighted Fracturing Fluid" with application number 200510105813.8 and "Ultra-high temperature weighted fracturing fluid" with application number 201310756267.9 and its preparation", "An organic boron weighted fracturing fluid and its preparation method" with application number 201710685790.5, "A high temperature resistant weighted fracturing fluid and its preparation method" of 201910464347.4, etc., but these weighted guar gum fracturing There are still no small problems in the realization of the functions of reducing the cost, reducing the construction friction, ensuring the breaking performance, and improving the flowback of the breaking liquid.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problems existing in the existing guar gum weighted fracturing fluid system, through the optimization of the compound weighting agent, the multi-component modification of guar gum, the layer-by-layer wrapping, the multi-component chelation delaying the preparation of the cross-linking agent, and the high-efficiency drainage aid compound. It provides a delayed cross-linking type guar fracturing fluid with high temperature resistance, low friction and aggravation.

The delayed cross-linking type anti-high temperature and low friction aggravated guar gum fracturing fluid provided by the present invention comprises the following components by mass percentage:

Compound weighting agent 25%～55%, multivariate modified guar gum 0.25%～0.45%, weighting aid No. 1 0.05%～0.1%, weighting aid No. 2 0.7%～1.0%, alkaline regulator 0.3%～0.5 %, oxygen scavenger 0.3%-0.4%, high-efficiency drainage aid 0.3%-0.5%, retarding cross-linking agent 0.6%-1.2%, gel breaker 0.02%-0.1%, and the rest are fresh water.

Wherein, the compound weighting agent is composed of weighting agent A and weighting agent B in a mass ratio of 1:3, weighting agent A is sodium lactate or potassium lactate, and weighting agent B is potassium formate or potassium sulfate. The pH value of the potassium sulfate aqueous solution is equal to 7 to meet the requirements, and when potassium sulfate is used, the density of the weighting liquid is in the range of 1.2 to 1.31 g/cm ³ . The use of the composite weighting agent simplifies the salt water weighting process and reduces the weighting agent. cost, and ultimately meet the performance requirements of weighted fracturing fluids.

The multi-component modified guar gum is prepared by using guanidine collagen powder, NaOH, epichlorohydrin, sodium bromoacetate, and halohexadecane as main raw materials, and ethanol, isopropanol, acetone, hydrochloric acid, water, etc. as auxiliary materials. , the specific method is as follows:

(1) Add 150 parts to 180 parts of ethanol to the reaction kettle, add 50 parts to 65 parts of guanidine collagen powder under the condition of medium speed stirring (150r/min), stir for 30min, after mixing evenly, add to the mixed solution Add 50 to 80 parts of deionized water and 8 to 10 parts of 15% NaOH solution, set low-speed stirring (80 r/min), the temperature of the reactor is 40 ° C to 50 ° C, and allow guar gum to be alkalized in the solution for 80min~ 150min;

(2) set the temperature of the reactor to 65°C to 72°C, set the medium-speed stirring (300r/min), add 100 to 120 parts of isopropanol, and dropwise add epichlorohydrin 28 to the solution in the top additive tank of the reactor parts to 32 parts, the dropwise addition time is 40min to 50min, and the etherification reaction is continued for 90min to 120min after the dropwise addition;

(3) stop stirring, cool the reaction kettle, and set the temperature to be 35 ℃～40 ℃, when the temperature reaches the requirement, open medium speed stirring (300r/min), add 8 parts～11 parts of bromoacetic acid in the reaction kettle Sodium, after stirring for 30min, set low-speed stirring (80r/min), and continue the carboxymethylation reaction for 90min-110min;

(4) The reaction kettle is heated to 75 ℃～85 ℃, set the medium speed stirring (300r/min) to drip 25 parts～30 parts of halohexadecane into the solution from the top, drip time 60min, after dripping is completed Set low-speed stirring (80r/min), and then continue hydrophobic modification for 240-300min. During the reaction process, the pH value change of the solution in the reaction kettle is detected from time to time, and the reaction stop standard is when the pH does not change;

(5) stop heating, keep stirring at low speed (80r/min), and add 6 to 9 parts of 25% hydrochloric acid according to the pH value to neutralize to pH neutrality;

(6) Distillation under reduced pressure, washing, drying and pulverization to obtain multi-component modified guar gum powder.

Preferably, the optimal component ratio of the main raw materials is guanidine collagen powder: NaOH: epichlorohydrin: sodium bromoacetate: halohexadecane=6:1:2:1:2. The relative molecular weight of the obtained multi-component modified guar gum is 300,000 to 400,000, and its main representative molecular structural formula is as follows:

where a is 300-400, b is 0-200, c is 320-380, d is 320-380, e is 300-400; R ₁ is a long-chain alkyl group.

The weight ratio of each raw material component of the delayed crosslinking agent (the sum of all components is 100 parts) and the preparation method are as follows: (1) 10 to 12 parts of trimethyl borate, 6 to 8 parts of trimethyl borate, 6 to 8 parts of trimethyl borate are added into the reactor. The triethanolamine and 4 to 6 parts of isopropanol are heated to 60°C to 65°C under stirring, and the temperature is kept constant for 0.5h to 1.2h. (2) add 21 parts to 23 parts of methanol in the reaction kettle, then evenly add 22 parts to 23 parts of sorbitol (adjust the speed of the stirrer, and control the adding speed), until the sorbitol dissolves completely, raise the reaction kettle Temperature to 70 ℃ ~ 75 ℃, constant temperature reaction 2h ~ 3h. (3) add 11 parts～13 parts of water in the reaction kettle, then slowly add 12 parts～15 parts sorbitol, 4 parts～6 parts borax and 0.1 part～0.5 parts KOH, keep the reaction kettle temperature 60 ℃～ 80°C, and slowly add 0.5 to 2 parts of succinaldehyde dropwise to the solution through the addition tank (dropwise added within 30 minutes), continue the reaction for 1.8h to 3h, cool and discharge to obtain a delayed crosslinking agent. Through the three-stage reaction, the layer-by-layer encapsulation and multi-chelation of borate ions are realized, which is conducive to slow release in the fracturing fluid, and achieves the purpose of delaying cross-linking, reducing frictional resistance and high temperature resistance.

Preferably, the best preparation method of the delayed crosslinking agent: (1) add 11.5 parts of trimethyl borate, 7.0 parts of triethanolamine and 5.0 parts of isopropanol into the reaction kettle, and under stirring conditions The temperature was raised to 62°C, and the temperature was kept constant for 1h. (2) add 22.0 parts of methanol in the reaction kettle, then evenly add 22.5 parts of sorbitol (adjust the stirring speed and control the adding speed), until the sorbitol dissolves completely, raise the temperature of the reaction kettle to 73 ℃, and keep a constant temperature The reaction is carried out for 2h to 3h. (3) add 12.5 parts of water in the reaction kettle, then slowly add 14.0 parts of sorbitol, 4.3 parts of borax and 0.2 part of KOH, keep the temperature of the reaction kettle at 70 ℃, and slowly add 1 part dropwise to the solution through the feeding tank The succinaldehyde was added dropwise within 30 min, the reaction was continued for 2 h, and the material was cooled and discharged to obtain a delayed cross-linking agent.

The weighting adjuvant No. 1 is citric acid or acetic acid; the weighting adjuvant No. 2 is one of sodium gluconate, sodium nitrilotriacetate, amine trimethylene phosphate and sodium dimercaptopropane sulfonate. The compound use of the weighting aid No. 1 and the weighting aid No. 2 can improve the ionic environment of the weighted salt water, promote the dissolution of the multi-component modified guar gum, and improve the stability of the thickener molecules in the salt water.

The regulator is one of NaOH and KOH.

The oxygen scavenger can remove the dissolved oxygen in the fracturing fluid and reduce the damaging effect of high temperature on the fracturing fluid structure, and is mainly one of sodium sulfite, sodium thiosulfate, potassium thiosulfate, and sodium ascorbate. Two quality ratios.

The high-efficiency drainage aid is a mixture of fluorocarbon modified surfactant, sodium silicate, methanol, and water in a weight ratio of 20:5:20:55. The fluorocarbon modified surfactant is one of a nonionic perfluorooctyl polyoxyethylene ether surfactant and a nonionic perfluoroalkyl ether oxa surfactant. After the high-efficiency drainage aid is used, it can effectively inhibit the salt precipitation, and at the same time greatly reduce the surface tension of the fracturing fluid and improve the wettability of the rock surface, thereby greatly improving the flowback performance of the breaking fluid.

The gel breaker is sodium bromate or sodium bromate capsules or a mixture of the two, wherein the sodium bromate capsules are made by using sodium bromate as the capsule core and using cellulose acetate phosphate and gelatin as the composite capsule coating. Described sodium bromate capsule takes sodium bromate as capsule core, takes cellulose acetate phosphate and gelatin as composite capsule, takes ethyl lactate as solvent, adjusts HLB value and polyethylene glycol through span 85 and Tween 60 600 thickening, prepared by stirring, reacting, vacuuming, filtration, drying and other steps under certain conditions. Further, the consumption of sodium bromate is preferably 0.03% to 0.06%, and the consumption of sodium bromate capsules is preferably 0.02% to 0.1%. The total dosage ratio is 2:1, and the methods of wedge-shaped addition and reverse-wedge-shaped addition are adopted respectively in fracturing construction. The gel breaker can not only ensure the stability of the gel under high temperature during fracturing, but also completely break the gel of the fracturing fluid after the fracturing is completed.

A method for applying the delayed cross-linking type anti-high temperature and low friction aggravating guar fracturing fluid, comprising the following steps:

(1) Calculate the weight percentage of weighting agent under the specified density, and the formula is as follows:

ω _B = 3ω _A

In the formula: ρ is the density required for the design of the weighted fracturing fluid (when potassium sulfate is used as weighting agent B, the value of ρ is 1.2-1.31 g/cm ³ ; when potassium formate is used as weighting agent B, the value of ρ is 1.2-1.45 g/cm 3 ; cm ³ );

ω _A is the weight percent of sodium lactate or potassium lactate;

ω _B is the weight percent of potassium formate, potassium sulfate;

R is the correction coefficient of the weight percentage when sodium lactate and potassium lactate are used. When sodium lactate is used, R=0.87; when potassium lactate is used, R=0.92.

According to the designed weighting liquid density ρ, the weight percentages ω _A and ω _B of the weighting agent are calculated.

(2) Calculate the reserve water volume of the on-site liquid storage tank and the weight of the weighting agent, the formula is as follows:

m _A + m _B = ρ*0.95V _total (ω _A +ω _B )

In the formula: V is the _total volume of the on-site liquid storage tank; the effective volume is usually calculated by multiplying the total volume by a factor of 0.95. For example, a large tank with a total volume of 40 cubic meters has an effective volume of 38 cubic meters.

V _{Reserve water} The amount of clean water required for each liquid storage tank;

_mA is the mass of sodium lactate or potassium lactate;

m _B is the mass of potassium formate or potassium sulfate.

(3) On-site preparation of weighted guar gum fracturing fluid base fluid, the steps are as follows:

S1 _: Clean the liquid storage tank and prepare clean _water according to the calculated V;

S2: Add weighting aid No. ₂ and weighting agent A into the tank under stirring conditions, stir evenly, slowly add weighting agent B, and continue stirring at a constant speed to ensure that weighting agent B dissolves;

S3: When the density of brine reaches the design requirements, add oxygen scavenger and weighting aid No. ₁ to the tank, and circulate and stir evenly;

S4: Under the conditions of circulation and stirring, using jet technology, the multi _- component modified guar gum is inhaled into the tank and dispersed evenly into the liquid, the liquid begins to swell, and the multi-component modified guar gum is added and then continues to circulate and stir for 30 minutes;

S5: After detecting that the viscosity of the liquid base liquid is greater than _50mPa.s , add an alkaline regulator and a high-efficiency drainage aid, and continue to stir for 10 minutes;

_S6 : Stop the circulation and stirring, and let the liquid stand for 2h to 4h, which is the delayed cross-linking type anti-high temperature, low friction and aggravated guar gum fracturing fluid base fluid.

(4) Quality control of fracturing construction fluid

The fracturing construction liquid quality control includes the crosslinking agent addition procedure and the gel breaker addition procedure. During fracturing construction, the sand mixer sucks the weighted fracturing fluid base fluid from the liquid storage tank into the sand mixing tank to delay the delivery. The linking agent is proportionally pumped into the sand mixing tank through the liquid additive pump on the sand mixer, and the breaker is added to the sand mixing tank in proportion through the dry powder additive pump on the sand mixer. After tank mixing, it is slowly cross-linked, and the proppant is pressed into the formation after passing through the fracturing truck and the wellhead distributor.

The described cross-linking agent addition procedure follows the following principles:

When the dosage of multi-component modified guar gum is 0.25%-0.3%, the dosage of retarding cross-linking agent is preferably 0.6%-0.7%, and when the dosage of multi-component modified guar gum is 0.3%-0.35%, the dosage of delaying cross-linking agent is preferably 0.7% ～0.8%, when the dosage of multi-component modified guar gum is 0.35%-0.4%, the dosage of delaying cross-linking agent is preferably 0.8%-1.0%, when the dosage of multi-component modified guar gum is 0.4%-0.45%, the dosage of delaying cross-linking agent is It is preferably 1.0% to 1.2%.

The described breaker addition procedure follows the principles of wedge addition and reverse wedge addition:

1) In the pre-liquid stage, sodium bromate capsules are added in an amount of 0.1% to 0.08%;

2) In the sand-carrying liquid stage, within 30% of the designed sand-carrying liquid amount, add sodium bromate capsules in an amount of 0.08% to 0.06%, and when the designed sand-carrying liquid amount is 30% to 60%, according to 0.06% to 0.04% Add sodium bromate capsules and 0.03% sodium bromate; when the designed amount of sand-carrying liquid is 60% to 80%, add sodium bromate capsules in an amount of 0.04% to 0.02%, and add 0.04% bromine Sodium; when the designed sand-carrying liquid is 80% to 100%, add sodium bromate in an amount of 0.05%;

3) In the displacement liquid stage, sodium bromate is added in an amount of 0.06%.

Compared with the prior art, the advantages of the present invention are:

(1) In the present invention, a composite weighting agent is adopted, including liquid sodium lactate or potassium lactate, solid powder potassium formate and potassium sulfate, which can weight the fracturing fluid within the density range of 1.2 to 1.45 g/cm ³ , and The on-site preparation process is simple and convenient, that is, it meets the liquid performance requirements, reduces the cost of the weighting agent and the construction cost, and more importantly, the weighting agent is compatible with the fracturing fluid system.

(2) In the invention, the guar gum is multi-modified guar gum, that is, the long chain of hydrophilic group carboxymethyl group, hydroxypropyl group and hydrophobic group alkyl group is introduced into the molecular structure of guar gum. After modification, its water solubility in high salinity brine is significantly accelerated, and the dosage is reduced; and due to the introduction of a large number of defunctionalized functional groups, the effect of the matching crosslinking agent is improved; the content of water insoluble matter is reduced by more than 70%, which is significantly Damage reduced.

(3) In the invention, the delayed boron cross-linking agent is used, and through the staged reaction, the layer-by-layer encapsulation and multi-chelation of borate ions are realized, which is beneficial to the slow release in the fracturing fluid and achieves the purpose of delaying the cross-linking. Therefore, fracturing When the liquid increases the density and reduces the wellhead construction pressure, the liquid can effectively reduce the friction of the pipeline, and the resistance reduction rate can reach more than 60%.

(4) After the cross-linking agent interacts with the guar gum base liquid, the jelly has strong structural strength and is reversible, so its temperature and shear resistance and sand-carrying properties are significantly enhanced. Through formula adjustment, it can meet the requirements of 120 ℃ ~ 180 ℃ High temperature and high pressure reservoir fracturing construction requirements.

(5) In the invention, a special gel breaker is selected through a large number of experiments, which can not only ensure the stability of the gel under high temperature during fracturing, but also completely break the fracturing fluid after the fracturing. The problem of fracturing fluid breaking the gel.

(6) In the invention, a composite high-efficiency drainage aid is selected, which can prevent precipitation with fracturing fluid, effectively inhibit salting out, and at the same time effectively solve problems such as precipitation and salting out of gel breaking fluid, and can also greatly reduce fracturing fluid. The surface tension of the gel-breaker is improved, and the wettability of the rock surface is improved, thereby greatly improving the flow-back performance of the gel-breaker.

(7) The calculation formula of the weighted fracturing fluid composition is optimized, and the weighting dose and water reserve required for on-site construction can be calculated only by specifying the density of the weighting fluid, which is simple, convenient and easy to operate.

Other advantages, objects, and features of the present invention will appear in part from the description that follows, and in part will be appreciated by those skilled in the art from the study and practice of the invention.

Description of drawings

Figure 1 is a graph showing the change of crosslinking time and crosslinking temperature of the retarded crosslinking agent in Example 5 of the present invention under different crosslinking ratios (thickening agent 0.45%, regulator 0.4%).

Fig. 2 is the temperature resistance and shear resistance test curve of the delayed cross-linking type high temperature aggravated guar gum fracturing fluid (ρ=1.20g/cm ³ ) aggravated by sodium lactate and potassium formate according to the present invention at 140°C .

Fig. 3 is the temperature resistance and shear resistance test curve of the delayed cross-linking type high temperature aggravated guar gum fracturing fluid (ρ=1.25g/cm ³ ) aggravated by sodium lactate and potassium sulfate of Example 7 of the present invention under the condition of 140°C .

Figure 4 is the temperature and shear resistance test curve of the delayed cross-linking type high temperature aggravated guar gum fracturing fluid (ρ=1.31g/cm ³ ) aggravated by potassium lactate and potassium sulfate according to the present invention at 150°C .

Fig. 5 is the temperature resistance and shear resistance test of potassium lactate and potassium formate aggravated delayed cross-linking type high temperature aggravated guar gum fracturing fluid (ρ=1.45g/cm ³ ) according to Example 9 of the present invention under the condition of 160°C curve.

Figure 6 is the temperature and shear resistance test curve of the delayed cross-linking type high temperature aggravated anti-high temperature guar gum fracturing fluid (ρ=1.45g/cm ³ ) aggravated by sodium lactate and potassium formate of Example 10 of the present invention at 170°C.

Fig. 7 is the temperature resistance and shear resistance test curve of the delayed cross-linking type high temperature aggravated guar gum fracturing fluid (ρ=1.45g/cm ³ ) aggravated by potassium lactate and potassium formate of the present invention at 180°C .

Figure 8 shows the high temperature and high shear resistance test of the delayed cross-linking type high temperature aggravated anti-high temperature aggravated guar gum fracturing fluid (ρ=1.45g/cm ³ ) aggravated by potassium lactate and potassium formate of Example 11 of the present invention at 180°C curve.

FIG. 9 is a schematic diagram of a coiled tubing friction measuring device for frictional resistance testing of a weighted guar gum fracturing fluid according to Example 12 of the present invention.

FIG. 10 is a fitting curve of friction resistance under different displacements of the weighted guar fracturing fluid according to Example 12 of the present invention.

FIG. 11 is the contact angle test image of the core after treatment with the weighted guar gum fracturing fluid in Example 13 of the present invention.

Fig. 12 is the fracturing operation curve of the application of sodium lactate and potassium formate aggravated guar gum fracturing fluid in a well in Yanchang Oilfield in the application case of the present invention.

Detailed ways

The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, but not to limit the present invention.

Unless otherwise specified, the experimental conditions and experimental methods for the performance evaluation of delayed cross-linking type anti-high temperature and low friction aggravated guar gum fracturing fluids involved in the examples refer to "SY/T 5107-2005 Performance Evaluation Method of Water-Based Fracturing Fluids" ".

Unless otherwise specified, the percent sign "%" involved in the examples is all mass percent.

Example 1

The optimized component ratio and preparation conditions of the multi-component modified guar gum provided by the present invention:

Using guanidine collagen powder, NaOH, epichlorohydrin, sodium bromoacetate, and chlorohexadecane as the main raw materials, the weight ratio of guanidine collagen powder, NaOH, epichlorohydrin, sodium bromoacetate, and chlorohexadecane is 6 :1:2:1:2. Using ethanol, isopropanol, acetone, hydrochloric acid, water, etc. as auxiliary materials to prepare multi-component modified guar gum, the preparation process is as follows:

S1: add ₁₈₀ parts of ethanol to the reaction kettle, add 60 parts of guanidine collagen powder under the condition of medium speed stirring (150r/min), stir for 30min, after mixing evenly, add 60 parts of deionized 10 parts of water and 15% NaOH solution, set low-speed stirring (80r/min), set the temperature of the reaction kettle to 43 ° C, and allow guar gum to be alkalized in the solution for 110min;

S2 _: set the temperature of the reactor to 68° C., set the medium-speed stirring (300 r/min), add 120 parts of isopropanol, and add 20 parts of epichlorohydrin to the solution in the additive tank at the top of the reactor, and the dropping time is 50min, continue to carry out etherification reaction 100min after dripping;

S3: stop stirring, cool the reaction kettle, and set the temperature to 40° C., when the temperature reaches the requirement, turn on medium-speed stirring ( ₃₀₀ r/min), add 10 parts of sodium bromoacetate to the reaction kettle, and stir for 30 min, Set low-speed stirring (80r/min), continue the carboxymethylation reaction for 120min;

S ₄ : the reaction kettle is heated to 80° C., medium-speed stirring (300 r/min) is set, and 30 parts of halohexadecane are added dropwise to the solution from the top, the dropping time is 60 min, and low-speed stirring (80 r/ min), then continue the hydrophobic modification for 290min, and detect the pH value change of the solution in the reaction kettle from time to time during the reaction, and take the reaction stop standard when the pH has no change;

S5: stop heating, keep stirring at low speed (80r/min), add ₉ parts of 25% hydrochloric acid for neutralization according to the pH value, and adjust the pH to 7-8;

S ₆ : distillation under reduced pressure, washing, drying and pulverization to obtain multivariate modified guar gum BCGR-180.

The relative molecular weight of the multi-component modified guar gum was determined by the capillary viscometer method to be 388,900, and its representative molecular formula is:

Where a is 300-400, b is 0-200, c is 320-380, d is 320-380, e is 300-400; R ₁ is a long chain of hexadecyl.

Example 2

Compare the performance of the multivariate modified guar gum BCGR-180 prepared in Example 1 with the common guar gum thickener:

The swelling of several thickeners in sodium lactate and potassium formate weighted brine (density 1.4g/cm ³ ) was tested, and the moisture content and water-insoluble content of the thickener were compared. The results are shown in Table 1. It can be seen that the properties of BCGR-180 are superior. When the dosage is low, the swelling speed in brine is fast, the apparent viscosity is high, and the content of water-insoluble matter is greatly reduced.

Table 1 Performance comparison of several guar gum thickeners

In the table, JK101 refers to the hydroxypropyl guar gum thickener of Sinopec Kunshan Company, the model is JK101;

J486R refers to the high temperature resistant guar gum thickener of Sinopec Kunshan Company, the model is J486R;

CJ2-6 HPG refers to the hydroxypropyl guar gum thickener of Sinopec Kunshan Company, the model is CJ2-6.

Example 3

Performance test of weighting aid provided by the present invention:

The addition of salt will affect the dissolution of the thickening agent and the viscosity of the base liquid of the thickening agent solution, so it is necessary to select an additive that can improve the swelling speed and swelling ratio of the thickening agent, that is, the weighting aid of the present invention. First prepare different weighted saline, take 500mL of saline sample and pour it into a sterile mixer, add weighting adjuvant first, weigh 0.45% of the thickener and slowly add it to the mixer, stir for 5 minutes, and then pour it into a beaker , test the change of liquid viscosity with time, the test results are shown in Table 2. It can be seen from the experimental results that when the weighting additives No. 1 and No. 2 are used in combination, the swelling speed of BCGR-180 is the fastest, and the viscosity of the base liquid is the highest. The effect of 1+1>2 is achieved.

Table 2 Influence of weighting additives on swelling properties of BCGR-180 (0.45%)

Example 4

A preparation process of delaying cross-linking agent is as follows:

The first stage: add 11.5 parts of trimethyl borate, 7.0 parts of triethanolamine and 5.0 parts of isopropanol into the reaction kettle, heat up to 62°C under stirring conditions, and keep the temperature constant for 1h;

The second stage: add 22.0 parts of methanol to the reaction kettle, and then evenly add 22.5 parts of sorbitol (adjust the speed of the stirrer and control the addition speed), when the sorbitol dissolves completely, raise the temperature of the reaction kettle to 73 ° C, Constant temperature reaction 2h～3h;

The third stage: add 12.5 parts of water to the reaction kettle, then slowly add 14.0 parts of sorbitol, 4.3 parts of borax and 0.2 parts of KOH, keep the temperature of the reaction kettle at 70 ° C, and slowly add 1 Part of succinaldehyde (dropwise added within 30 minutes), continued to react for 2 h, cooled and discharged to obtain delayed cross-linking agent HT-BC180.

Example 5

The cross-linking time and jelly strength test of the delayed cross-linking agent provided by the present invention:

Prepare a weighted guar gum fracturing fluid base fluid with a density of 1.4g/ ^cm3 according to the optimized formula:

The multivariate modified guar gum of Example 1 0.45% + weighting aid No. 1 citric acid 0.1% + weighting aid No. 2 sodium gluconate 0.8% + regulator KOH 0.4% + oxygen scavenger sodium sulfite 0.4% + high-efficiency drainage aid 0.4%. Among the high-efficiency drainage aids, non-ionic perfluorooctyl polyoxyethylene ether surfactant: sodium silicate: methanol: water weight ratio of 20:5:20:55; non-ionic perfluorooctyl polyoxyethylene ether The surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6.

Different amounts of cross-linking agent HT-BC180 were used for cross-linking with the base fluid, and the temperature and time when the fracturing fluid began to form during the simulated heating process were tested. The test results are shown in Table 3, and the graph is shown in Figure 1. It can be seen from the test results that HT-BC180 retarding crosslinking agent has excellent retarding crosslinking performance. With the increase of the amount of crosslinking agent, the temperature required to start crosslinking becomes lower, and the crosslinking time gradually shortens.

If the cross-linking ratio is too low, the strength of the gel formed is not enough or even cannot be cross-linked. If the cross-linking ratio is too high, the cross-linking speed is too fast, and the gel formed is brittle; the larger the cross-linking ratio, the more borate ions in the system. The faster the crosslinking with guar gum, the shorter the crosslinking time. Therefore, when the dosage of BCGR-180 is 0.45%, the dosage of the cross-linking agent is 1.0% to 1.2%.

The cross-linking time and jelly strength test results of the cross-linking agent in table 3

Crosslinking ratio, % 0.8 0.9 1.0 1.1 1.2 1.3 1.4 Temperature during cross-linking, °C 122 115 113 109 106 98 85 Cross-linking time, min 25 21.3 18.2 17 15.2 12.5 10.6 gel strength weaker weak powerful powerful powerful slightly crispy Strong brittleness

Example 6

Delayed cross-linking type high temperature aggravated guar gum fracturing fluid aggravated by sodium lactate and potassium formate, density 1.2g/cm ³ , temperature resistance 120℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: sodium lactate 6.71%, potassium formate 20.13%;

Weighting aid No. 1: citric acid 0.1%;

Multivariate modified guar gum BCGR-180: 0.25%;

Weighting Auxiliary No. 2: Sodium Gluconate 0.8%;

Oxygen scavenger: sodium thiosulfate 0.3%;

High-efficiency drainage aid: (non-ionic perfluorooctyl polyoxyethylene ether surfactant: sodium silicate: methanol: water = 20:5:20:55) 0.3%; non-ionic perfluorooctyl polyoxyethylene The ether surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6.

Regulator: NaOH 0.3%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel

Add the delayed cross-linking agent HT-BC180 to the base liquid: 0.6%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 0.6% by weight of delayed cross-linking agent HT-BC180 was added to the base fluid. fissure.

Using a high-temperature rheometer at 170s ^-1 , 120℃, the delayed cross-linking type high temperature aggravated guar gum fracturing fluid aggravated by sodium lactate and potassium formate was used to test the temperature and shear resistance for 120min. The test curve is shown in Figure 2. .

From the 120 ℃ rheological test curve, it can be seen that the weighted guar gum fracturing fluid has good retardation and cross-linking performance, and there is a process of secondary cross-linking in the process (indicating that the cross-linking agent is wrapped layer by layer and multi-chelation has played an effect) , after 170s ^-1 of continuous shearing for 120min, the fracturing fluid viscosity is finally greater than 100mPa·s, indicating that the fracturing fluid of this embodiment has good temperature and shear resistance at 120°C.

Example 7

Delayed cross-linking anti-high temperature aggravated guar gum fracturing fluid aggravated by sodium lactate and potassium sulfate, density 1.25g/cm ³ , temperature resistance 140℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: sodium lactate 8.21%, potassium sulfate 24.63%;

Weighting aid No. 1: citric acid 0.05%;

Multivariate modified guar gum BCGR-180: 0.30%;

Weighting Auxiliary No. 2: Sodium Gluconate 0.8%;

Oxygen scavenger: sodium thiosulfate 0.3%;

High-efficiency drainage aid: (non-ionic perfluorooctyl polyoxyethylene ether surfactant: sodium silicate: methanol: water = 20:5:20:55) 0.3%; non-ionic perfluorooctyl polyoxyethylene The ether surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6;

Regulator: NaOH 0.4%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel

Add the delayed cross-linking agent HT-BC180 to the base liquid: 0.7%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 0.7% by weight of delayed cross-linking agent HT-BC180 was added to the base fluid. fissure.

Using a high-temperature rheometer at 170s ^-1 , 140℃, the delayed cross-linking anti-high temperature aggravated guar fracturing fluid aggravated by sodium lactate and potassium sulfate was tested for temperature and shear resistance for 120min. The test curve is shown in Figure 3. .

Example 8

Potassium lactate and potassium sulfate aggravated delayed cross-linking anti-high temperature aggravated guar gum fracturing fluid, density 1.31g/cm ³ , temperature resistance 150℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: potassium lactate 9.79%, potassium sulfate 29.36%;

Weighting aid No. 1: acetic acid 0.1%;

Multivariate modified guar gum BCGR-180: 0.35%;

Weighting Auxiliary No. 2: Sodium Nitrogentriacetate 0.8%;

Oxygen scavenger: potassium thiosulfate 0.4%;

High-efficiency drainage aid: (non-ionic perfluoroalkyl ether oxa surfactant produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6): sodium silicate: methanol: water = 20:5:20:55 ) 0.3%; non-ionic perfluorooctyl polyoxyethylene ether surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6;

Regulator: NaOH 0.4%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel

Add the delayed cross-linking agent HT-BC180 to the base liquid: 0.8%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 0.8% by weight of delayed cross-linking agent HT-BC180 was added to the base fluid. fissure.

Using a high temperature rheometer at 170s ^-1 and 150℃, the delayed crosslinking type high temperature aggravated guar gum fracturing fluid aggravated by potassium lactate and potassium sulfate was tested for temperature and shear resistance for 120min. The test curve is shown in Figure 4. Show.

Example 9

Potassium lactate and potassium formate aggravated delayed cross-linking anti-high temperature aggravated guar gum fracturing fluid, density 1.45g/cm ³ , temperature resistance 160℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: potassium lactate 13.31%, potassium formate 39.93%;

Weighting aid No. 1: citric acid 0.1%;

Multivariate modified guar gum BCGR-180: 0.40%;

Weighting Auxiliary No. 2: Sodium Nitrogentriacetate 0.8%;

Oxygen scavenger: sodium thiosulfate 0.4%;

High-efficiency drainage aid: (non-ionic perfluoroalkyl ether oxa surfactant: sodium silicate: methanol: water = 20:5:20:55) 0.3%; non-ionic perfluorooctyl polyoxyethylene The ether surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6;

Regulator: NaOH 0.4%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel

Add the delayed cross-linking agent HT-BC180 to the base liquid: 1.0%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 1.0% by weight of delayed crosslinking agent HT-BC180 was added to the base fluid, and after fully mixing, a delayed crosslinking type anti-high temperature weighted guar gum was obtained. fissure.

Using a high temperature rheometer at 170s ^-1 and 160℃, the delayed crosslinking type high temperature aggravated guar gum fracturing fluid aggravated by potassium lactate and potassium formate was used to test the temperature and shear resistance for 120min. The test curve is shown in Figure 5. Show.

Example 10

Delayed cross-linking type high temperature aggravated guar gum fracturing fluid aggravated by sodium lactate and potassium formate, density 1.45g/cm ³ , temperature resistance 170℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: sodium lactate 13.48%, potassium formate 40.44%;

Weighting aid No. 1: citric acid 0.1%;

Multivariate modified guar gum BCGR-180: 0.42%;

Weighting Auxiliary No. 2: Gluconic acid 1.0%;

Oxygen scavenger: sodium thiosulfate 0.4%;

High-efficiency drainage aid: (non-ionic perfluorooctyl polyoxyethylene ether surfactant: sodium silicate: methanol: water = 20:5:20:55) 0.3%; non-ionic perfluorooctyl polyoxyethylene The ether surfactant is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6;

Regulator: NaOH 0.5%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel:

Add the delayed cross-linking agent HT-BC180 to the base liquid: 1.1%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 1.1% by weight of delayed cross-linking agent HT-BC180 was added to the base fluid. fissure.

Using a high temperature rheometer at 170s ^-1 and 170℃, the delayed crosslinking type high temperature aggravated guar gum fracturing fluid aggravated by potassium lactate and potassium formate was used to test the temperature and shear resistance for 120min. The test curve is shown in Figure 6. Show.

Example 11

Potassium lactate and potassium formate aggravated delayed cross-linking anti-high temperature aggravated guar gum fracturing fluid, density 1.45g/cm ³ , temperature resistance 180℃. Its components and weight percentages are as follows:

Weighted guar gum fracturing fluid base fluid:

Compound weighting agent: potassium lactate 13.31%, potassium formate 39.93%;

Weighting aid No. 1: citric acid 0.1%;

Multivariate modified guar gum BCGR-180: 0.45%;

Weighting Auxiliary No. 2: Sodium Nitrogentriacetate 1.0%;

Oxygen scavenger: sodium thiosulfate 0.4%;

High-efficiency drainage aid: (non-ionic perfluorooctyl polyether surfactant: sodium silicate: methanol: water = 20:5:20:55) 0.4%; non-ionic perfluorooctyl polyoxyethylene ether surface The active agent is produced by Shanghai Yingzheng Technology Co., Ltd., product code FC-6;

Regulator: NaOH 0.5%;

The remaining components are fresh water.

Cross-linked weighted guar fracturing fluid gel

Add the delayed cross-linking agent HT-BC180 to the base liquid: 1.2%;

The temperature and shear resistance of this formulation were evaluated as follows:

A weighted guar gum fracturing fluid base fluid was prepared. After standing for 4 hours, 1.2% by weight of delayed cross-linking agent HT-BC180 was added to the base fluid. fissure.

Using a high temperature rheometer at 170s ^-1 and 180℃, the delayed crosslinking type high temperature aggravated guar gum fracturing fluid aggravated by potassium lactate and potassium formate was tested for temperature and shear resistance for 120min. The test curve is shown in Figure 7. Show.

From the rheological data, the delayed crosslinking time of the fracturing fluid is more than 15min, and after 120min of continuous shearing, the viscosity is still about 100mPa·s. Because the chemical bond formed by the cross-linking of borate ion and hydroxypropyl guar gum is reversible, after a period of shearing, the formation and destruction of chemical bonds reach a dynamic equilibrium, and the viscosity is basically stable. Overall, it shows that the delayed crosslinking time of the fracturing fluid system can be adjusted, and it has excellent temperature resistance and shear resistance, which can meet the construction requirements of high temperature deep well fracturing at 180 °C.

In order to understand the effect of high shear rate on the aggravated guar fracturing fluid, the process of high shearing of the fracturing fluid into the oil pipe through the sand mixer was simulated, using a high temperature rheometer at 170s ^-1 →510s ^-1 →170s ^-1 , the delayed cross-linking type high temperature aggravated guar gum fracturing fluid aggravated by potassium lactate and potassium formate was tested for temperature and shear resistance at 180℃ for 120min. The test curve is shown in Figure 8 .

It can be seen from the test curve that the viscosity of the fracturing fluid decreases under high shear, but the structure is not destroyed. When the shear rate returns to normal, the viscosity of the fracturing fluid recovers rapidly and begins to cross-link to form a gel. The test is completed. The viscosity of the post-fracturing fluid is kept above 80 mPa.s, and its apparent viscosity is less affected than that of the fluid without high shear, indicating that the boron-crosslinked guar gum fracturing fluid has a reversible system structure and has Excellent shear resistance.

Example 12

Large-scale coiled tubing friction test experiment with weighted guar fracturing fluid:

The on-site friction test of weighted fracturing fluid is very difficult to organize. For example, it is calculated directly from the construction data. Since it is not injected into the bare oil pipe, the obtained data and calculation results have certain deviations. Therefore, the weighted guar gum fracturing fluid was tested. Large coiled tubing friction test experiment.

The friction resistance test under all working conditions is carried out using real coiled tubing and fracturing truck. The experimental setup is shown in Figure 9. This test is used to demonstrate whether the good drag reduction properties of the delayed-type high-temperature aggravated guar gum fracturing fluid of the present invention also exist under field conditions. The coiled tubing used in the experiment is 375m long and has an inner diameter of 25.4mm. A 700-type fracturing truck is used as the power source. The maximum displacement is 1.0m ³ /min, the maximum pressure is 30MPa, and the amount of liquid required for the test is about 10m ³ .

The weighted guar gum fracturing fluid base fluid, cross-linked jelly in Example 7 and Example 11 (simulating field conditions, pumping after adding the cross-linking agent, allowing the fracturing fluid to cross-link during the test) and The coiled tubing friction resistance test was carried out in clear water. The properties of several liquids are shown in Table 4. The variation curve of the measured friction resistance with displacement is shown in Figure 10.

Table 4 Tested Liquid-Related Properties

By polynomial fitting of the pressure drop-displacement curves of several groups of liquids, the polynomial of the liquid friction with the displacement is obtained. , and then calculate the resistance reduction rate of fracturing fluid.

Table 5 Calculation data of several kinds of liquid resistance reduction rate under the specified displacement

It can be seen from the experimental data that when the displacement of several groups of weighted fracturing fluid reaches 6m ³ /min, the resistance reduction rate is above 60%, and the increase of liquid density and fracturing fluid viscosity increases the fluid friction to some extent The friction resistance of the cross-linked jelly is higher, and the friction resistance of the aggravated guar gum fracturing fluid base fluid is lower, but the invention delays the use of the cross-linking agent and reduces this effect as much as possible. After the test, the guar jelly was less damaged by shearing, and it also had better pick-up properties.

Example 13

Evaluation of gel breaking performance of delayed cross-linked anti-high temperature and low friction aggravated guar fracturing fluid:

The weighted guar gum fracturing fluids in Example 7 and Example 11 were used to evaluate the gel breaking performance, and the surface tension and residue content of the gel breaking fluids of the two groups of liquids were tested. The test results are shown in Table 6.

Table 6 Basic data test of fracturing fluid breaker fluid

The experimental results show that the fracturing fluid provided by the present invention has low viscosity of gel breaking fluid, low surface tension, and residue content as low as 150 mg/L or less, which is far lower than the national standard (600 mg/L).

In order to further understand the flowback performance of the gel breaker, two groups of gel breakers were used to treat the core, and the contact angle between the distilled water and the end face of the natural core was tested to understand the wetting performance of the gel breaker on the core. The test results are shown in Table 7 and Figure 11. . The results show that the fracturing fluid gel breaking fluid of the present invention has good wetting performance, changes the core wettability, and promotes the gel breaking fluid flowback.

Table 7 Basic data test of fracturing fluid breaker fluid

Field application example 1

In Well Yanha X, a well in the Inner Mongolia block of Yanchang Oilfield, the target layer is 3248.6m～3260.0m, and the predicted formation temperature is 117.8℃. The well was drilled in October 2018. On May 8, 2019, the fracturing gas test was carried out on the Bayin Gobi Formation from 3249m to 3253m. The 73mm oil pipe + packer injection method was used for fracturing. The maximum construction displacement was ^1.7m3 /min. ～69.2MPa), the amount of sand added (5.0m ³ ) failed to meet the design requirements.

From October 14th to 15th, 2019, a new perforation section of 3253m to 3255m was added, and the 3249m to 3255m of the Bayin Gobi Formation was refracted by the oil-casing injection method, and the total construction displacement was up to 2.2m ³ /min , the amount of sand added is 14.9m ³ , the amount of liquid into the ground is 653m ³ , and there is a certain gas output after pressing.

Table 8 Historical Fracturing Data Table

After the previous fracturing, the construction pressure exceeded the limit pressure and failed to meet the design requirements. According to the opinions of the geological department and the exploration company, it is believed that this layer is a new formation in the area and has certain potential, but the formation is a typical "elastic formation", the construction pressure is abnormal, and the common fracturing fluid used in the early stage is in the sand-carrying and There are certain problems in temperature resistance, and it is recommended to adopt reasonable and effective depressurization and frictional resistance technology to re-fract this layer.

In order to solve the above-mentioned problems, this well adopts the delayed cross-linking type anti-high temperature and low friction aggravated guar gum fracturing fluid ^of the present invention. The field application process is as follows:

(1) According to the geology of the target reservoir and the pre-construction pressure, it is determined to use a delayed cross-linking type high temperature aggravating guar gum fracturing fluid system with a density of 1.35g/cm ³ and a temperature resistance of 120℃, except for the weighting agent. In addition to the component content, the formula adopts the component ratio of the additive in Example 6;

(2) According to the designed weighting liquid density, the calculated weight percentages of weighting agent required are respectively: sodium lactate 10.99%, potassium formate 32.97%;

( ³ ) The construction site is equipped with two types of liquid storage tanks, ^40m3 and 50m3. Therefore, the water reserve of each liquid storage tank and the required weight of the weighting agent are calculated. Among them, 29.6m3 ^of water should be reserved for ^40m3 , and 5.64 of sodium formate should be added. t. Potassium formate ^16.91t , 50m3 should prepare 37m3 ^of water, add sodium formate 7.05t, potassium formate 21.15t, and calculate the amount of other additives according to the weight ratio;

(4) Prepare a weighted guar gum fracturing fluid base fluid on site, and the procedure is as follows:

S1 _: Clean the liquid storage tank to ensure that there is no sundries and residual liquid in the tank, and prepare clean _water according to the calculated V;

S2: Add weighting aid No. ₂ and weighting agent A to the large tank under stirring conditions, and after stirring evenly, start the liquid dosing cycle, slowly add weighting agent B, and continue stirring at a uniform speed to ensure that weighting agent B dissolves;

S3: When the density _of the brine reaches the design requirements, add oxygen scavenger and weighting aid No. 1 to the large tank, and circulate and stir evenly;

S ₄ : Under the condition of circulation and stirring, using jet technology, inhale the multi-modified guar gum into the large tank and make it evenly dispersed into the liquid, the liquid begins to swell, and then continue to circulate and stir for 30 minutes after the multi-component modified guar gum is added ;

S ₅ : After detecting that the viscosity of the liquid base liquid is greater than 50mPa.s, the regulator and the high-efficiency drainage aid can be added, and the stirring is continued for 10 minutes;

_S6 : Stop the circulation and stirring, and let the liquid stand for 2h to 4h, which is the delayed cross-linking type anti-high temperature, low friction and aggravated guar gum fracturing fluid base fluid.

Further, in order to ensure the performance of the fracturing fluid, the feeding sequence and process of preparing the fracturing fluid base fluid must be strictly implemented in accordance with the above procedures.

(5) Quality control of fracturing construction fluid:

The fluid quality control of fracturing construction includes the addition procedure of crosslinking agent and the addition procedure of gel breaker. During fracturing construction, the sand mixer sucks the weighted fracturing fluid base fluid from the liquid storage tank into the sand mixing tank to delay the crosslinking agent. The liquid additive pump on the sand mixer is pumped into the sand mixing tank in proportion, and the breaker is proportionally added to the sand mixing tank through the dry powder additive pump on the sand mixer. The base liquid, delayed crosslinking agent and gel breaker are mixed in the sand mixing tank After slowly cross-linking, the proppant is pressed into the formation after passing through the fracturing truck and the wellhead distributor.

The addition procedure of the crosslinking agent follows the following principles:

When the dosage of multi-component modified guar gum is 0.25%-0.3%, the dosage of retarding cross-linking agent is preferably 0.6%-0.7%, and when the dosage of multi-component modified guar gum is 0.3%-0.35%, the dosage of delaying cross-linking agent is preferably 0.7% ～0.8%, when the dosage of multi-component modified guar gum is 0.35%-0.4%, the dosage of delaying cross-linking agent is preferably 0.8%-1.0%, when the dosage of multi-component modified guar gum is 0.4%-0.45%, the dosage of delaying cross-linking agent is It is preferably 1.0% to 1.2%.

The breaker addition procedure follows the principles of wedge addition and reverse wedge addition:

S ₁ : in the pre-liquid stage, sodium bromate capsules are added in an amount of 0.1% to 0.08%;

S ₂ : In the sand-carrying liquid stage, within 30% of the designed sand-carrying liquid amount, add sodium bromate capsules in an amount of 0.08% to 0.06%. When the designed sand-carrying liquid amount is 30% to 60%, add sodium bromate capsules in an amount of 0.06% to 0.04%. % of sodium bromate capsules, and add 0.03% of sodium bromate; when the designed amount of sand-carrying liquid is 60% to 80%, add sodium bromate capsules in the amount of 0.04% to 0.02%, and add 0.04% of Sodium bromate; when the designed sand-carrying liquid is 80% to 100%, add sodium bromate in an amount of 0.05%;

S ₃ : In the displacement liquid stage, sodium bromate is added in an amount of 0.06%.

On August 16, 2020, the sand fracturing construction was carried out in Yanha X well, and the 3249m-3255m Bayingobi Formation was refracted by means of oil-casing injection. The total amount of guar gum fracturing fluid is 706.6m ³ , 80.3t of ceramsite is added (25t of powder ceramic, 55.3t of medium ceramic), the construction rupture pressure is 61.16MPa, and the general displacement is 2.5m ³ /min～4.5m ³ /min , the sand adding pressure is 57-63MPa, the highest sand ratio is 32%, the fracturing construction is relatively smooth, and the sand adding rate is 91.25%. The successful application of the present invention shows that the system effectively reduces the construction friction resistance and construction pressure, and has temperature resistance and sand-carrying performance. Excellent, compared with the previous three fracturing, the construction parameters have been greatly improved, which can fully meet the fracturing construction requirements of such abnormally high pressure reservoirs. The construction curve is shown in Figure 12.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Technical personnel, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments of equivalent changes by using the technical content disclosed above, but any content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (6)

1. a delayed cross-linked anti-high temperature and low friction aggravating guar fracturing fluid, is characterized in that, comprises the component of following mass percentage: Compound weighting agent 25%～55%, multivariate modified guar gum 0.25%～0.45%, weighting aid No. 1 0.05%～0.1%, weighting aid No. 2 0.7%～1.0%, alkaline regulator 0.3%～0.5 %, oxygen scavenger 0.3%-0.4%, high-efficiency drainage aid 0.3%-0.5%, retarding cross-linking agent 0.6%-1.2%, gel breaker 0.02%-0.1%, and the rest is fresh water; The compound weighting agent is composed of weighting agent A and weighting agent B in a mass ratio of 1:3, weighting agent A is sodium lactate or potassium lactate, and weighting agent B is potassium formate or potassium sulfate; The preparation method of the delayed cross-linking agent is as follows: (1) Add trimethyl borate, triethanolamine and isopropanol into the reaction vessel, turn on stirring, and conduct constant temperature reaction at 60°C～65°C for 0.5h～1.2h; (2) successively adding methanol and part of sorbitol to the reaction solution, heating up to 70°C～75°C, and reacting at constant temperature for 2h～3h; (3) adding water, then slowly adding remaining sorbitol, borax and KOH, keeping the temperature at 60°C～80°C, slowly adding succinaldehyde dropwise, continuing the reaction for 1.8h～3h, cooling and discharging to obtain a delayed crosslinking agent; The weighting adjuvant No. 1 is citric acid or acetic acid; the weighting adjuvant No. 2 is one of sodium gluconate, sodium nitrotriacetate, amine trimethylene phosphate, and sodium dimercaptopropane sulfonate; The preparation method of described multivariate modified guar gum is as follows: (1) Add guanidine collagen powder to ethanol and stir evenly, then add deionized water and NaOH solution to the mixed solution, and at 40°C～50°C, stir at low speed to alkalize guar gum in the solution for 80min～150min; (2) be warming up to 65～72 ℃, add isopropanol, and drip epichlorohydrin, continue to carry out etherification reaction 90min～120min after dripping is completed; (3) stop stirring, cool down to 35 ℃～40 ℃, add sodium bromoacetate, after stirring for 30min, continue carboxymethylation reaction for 90min～110min; (4) heat up to 75 ℃～85 ℃, add halohexadecane dropwise under stirring condition, carry out hydrophobic modification reaction for 240～300min, and detect the pH value change of the solution in the reaction kettle from time to time during the reaction, until there is no change in pH , stop the reaction; (5) stop heating, under stirring conditions, add hydrochloric acid to adjust pH to 7-8 according to the pH value of the solution; (6) Distillation under reduced pressure, washing, drying and pulverization to obtain multi-component modified guar gum powder. 2. The delayed cross-linked anti-high temperature and low friction aggravating guar gum fracturing fluid as claimed in claim 1, wherein the high-efficiency drainage aid is fluorocarbon modified surfactant, sodium silicate, methanol, A mixture of water in a weight ratio of 20:5:20:55. 3. delayed cross-linking type anti-high temperature and low friction aggravating guar fracturing fluid as claimed in claim 1, is characterized in that, described gel breaker is sodium bromate or sodium bromate capsule or both mixtures, so The sodium bromate capsules are made by using sodium bromate as the capsule core and using cellulose acetate phosphate phosphate and gelatin as the composite capsule coating. 4. an application method of delaying cross-linking type anti-high temperature and low friction aggravating guar fracturing fluid as described in any one of claims 1-3, is characterized in that, comprises the following steps of carrying out successively: Calculate the specified density The weight percentage of the lower weighting agent; calculating the water reserve in the on-site storage tank and the weight of the weighting agent; on-site preparation of the weighted guar gum fracturing fluid base fluid; quality control of the fracturing construction fluid; Among them, the weight percentage of weighting agent under the specified density is calculated, and the formula is as follows:

ω _B = 3ω _A In the formula: ρ is the density required for the design of the weighted fracturing fluid, g/cm ³ ; ω _A is the weight percent of sodium lactate or potassium lactate; ω _B is the weight percent of potassium formate, potassium sulfate; R is the correction coefficient of the weight percentage when sodium lactate and potassium lactate are used. When sodium lactate is used, R=0.87; when potassium lactate is used, R=0.92. 5. the application method of delaying cross-linking type anti-high temperature and low friction aggravating guar fracturing fluid as claimed in claim 4, is characterized in that, calculating on-site liquid storage tank water reserve and weight of weighting agent, the formula is as follows:

m _A + m _B = 1000ρ*0.95V _total (ω _A +ω _B ) Where: Vtotal is the _total volume of the on-site liquid storage tank, m ³ '; V _{Prepared water} is the amount of clean water required for each liquid storage tank, m ³ ; _mA is the mass of sodium lactate or potassium lactate, t; m _B is the mass of potassium formate or potassium sulfate, t. 6. the application method of delayed cross-linking type anti-high temperature and low friction aggravating guar fracturing fluid as claimed in claim 4, it is characterized in that, aggravating guar fracturing fluid base fluid is prepared on site, and the steps are as follows: S1 _: Clean the liquid storage tank and prepare clean _water according to the calculated V; S2: Add weighting aid No. ₂ and weighting agent A into the tank under stirring conditions, stir evenly, slowly add weighting agent B, and continue stirring at a constant speed to ensure that weighting agent B dissolves; S3: When the density of brine reaches the design requirements, add oxygen scavenger and weighting aid No. ₁ to the tank, and circulate and stir evenly; S4: Under the condition of circulation and stirring, using the jet technology, the multi _- component modified guar gum is inhaled into the tank and uniformly dispersed into the liquid, the liquid begins to swell, and the multi-component modified guar gum is added and then continues to circulate and stir for 30 minutes; S5: After detecting that the viscosity of the liquid base liquid is greater than _50mPa.s , add an alkaline regulator and a high-efficiency drainage aid, and continue to stir for 10 minutes; _S6 : Stop the circulation and stirring, and let the liquid stand for 2h-4h, which is the delayed cross-linking type anti-high temperature, low friction and aggravating guar gum fracturing fluid base fluid.

Images