CN108659809B

CN108659809B - Preparation method of concentrated solution based on continuous fracturing

Info

Publication number: CN108659809B
Application number: CN201810381346.9A
Authority: CN
Inventors: 贾振福; 黄兴华; 陈秋林
Original assignee: Chongqing University of Science and Technology
Current assignee: SICHUAN SHENHE NEW MATERIAL TECHNOLOGY Co.,Ltd.
Priority date: 2018-04-25
Filing date: 2018-04-25
Publication date: 2020-10-27
Anticipated expiration: 2038-04-25
Also published as: CN108659809A

Abstract

The invention discloses a preparation method of a concentrated solution based on continuous fracturing, and relates to the technical field of slickwater fracturing of high-salinity stratum. The preparation method comprises the following steps: 1) optimal selection of oil items; 2) selecting a concentrated solution feeding sequence, wherein the concentrated solution feeding sequence comprises a dispersion medium, a stabilizer, a shear strength improving agent, a resistance reducing agent and an emulsifier in turn; 3) optimally selecting the 3# white oil with the content of 30 percent in the concentrated solution; 4) optimally selecting 1.5 percent of stabilizer in the concentrated solution; 5) optimally selecting 2% of the extracting and cutting agent in the concentrated solution; 6) optimally selecting 40% of the drag reducer in the concentrated solution; 7) optimally selecting 3% of emulsifier in the concentrated solution; 8) preparing concentrated solution according to the proportion content of the steps. The method has the advantages of accurate preparation, reasonable proportion, good stability of the prepared concentrated solution, high hydration speed and low viscosity.

Description

Preparation method of concentrated solution based on continuous fracturing

Technical Field

The invention relates to the technical field of high-salinity stratum slickwater fracturing.

Background

The development of shale gas in China is still in the initial stage, and the exploitation mode of shale gas is mainly hydraulic fracturing technology. The hydraulic fracturing technology is characterized in that fracturing fluid is pressed into an oil well, then a stratum is pressed to be cracked, a crack channel with high flow conductivity is generated, and then a propping agent is injected to prop up the crack, so that the recovery rate of an oil-gas field is improved.

The hydraulic fracturing technology has the characteristics of simple operation and low price.

However, the general fracturing fluid is prepared in advance, transported to the site by a tanker truck and then pressed into the ground by a large fracturing truck. In conventional water-based fracturing fluid technology, hydroxypropyl guar dry powder is often used as a thickening agent, and after the hydroxypropyl guar is added into water, the hydroxypropyl guar is often fully stirred in order to be fully hydrated and reach a certain viscosity, and the process is time-consuming, which also indicates that the technology is divided into two steps, wherein the first step is to add the guar and the fracturing fluid additive into the water, and then the second step is to fully stir and hydrate the guar and the fracturing fluid additive, so as to form the fracturing fluid. The conventional fracturing fluid technology is generally called intermittent fracturing fluid technology, which is mainly that after a base station prepares fluid, the fluid is transported to a wellhead and pressed into the bottom layer through fracturing, but because the well conditions of each place are different, unnecessary waste is caused for wells with complicated downhole conditions or base stations which are far away from an oil field, the waste comprises waste of prepared fracturing fluid materials and waste of transportation cost process. The intermittent fracturing fluid is also not suitable for use in severe weather due to the fact that the using amount of the dry guanidine gum powder is large, the dust amount is large, the labor intensity is high, and fish eyes are easily caused to form local gel of the fracturing fluid if the temperature is improper or the stirring is not uniform. In addition, the general tank bottom of the feeding mode has excessive fracturing fluid, and the excessive fracturing fluid cannot be recycled, so that great waste is caused.

Because of various problems existing in the intermittent fracturing technology, research on the intermittent fracturing technology is started at home and abroad, and then the continuous fracturing technology is developed. The continuous fracturing technology is also called as a rapid mixing technology, the conventional fracturing technology of firstly preparing liquid and then constructing is changed into a continuous fracturing technology of simultaneously preparing liquid and pumping, various additives are added in the construction process, so that raw materials and formulas for construction can be debugged on site, liquid can be prepared according to the specific conditions of actual construction, the phenomena of liquid waste, construction limitation and the like can not occur, and the efficiency of fracturing construction can be improved.

The key of the continuous water-based fracturing technology lies in the preparation of concentrated solution, the performance of the prepared concentrated solution has three standards, namely the stability of the concentrated solution, which is the primary condition for the prepared concentrated solution, if the stability is not good, the guanidine gum thickening agent can be caused to sink in water, so that the concentrated solution has a layering phenomenon, the concentration of the formed fracturing solution is not uniform, the fracturing effect of the fracturing solution can be completely influenced, and the fracturing is unsuccessful. Secondly, viscosity, the pumpability of the concentrate is affected by the viscosity, and if the viscosity is low, the pumpability is good. Otherwise, the pumpability is seriously affected. The third performance criterion is hydration rate. The hydration speed refers to the tackifying speed of the guanidine gum thickener in water after the concentrated solution is added into the water, and the hydration speed is very critical in order to achieve the continuous water-based fracturing technology.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preparing a concentrated solution based on continuous fracturing, which has the advantages of accurate preparation, reasonable proportion, good stability of the prepared concentrated solution, high hydration speed and low viscosity.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of a concentrated solution based on continuous fracturing comprises the following steps:

1) optimally selecting oil items, and selecting 3# white oil with the minimum density as a dispersion medium for preparing the concentrated fracturing fluid;

2) selecting a concentrated solution feeding sequence, wherein the concentrated solution feeding sequence comprises a dispersion medium, a stabilizer, a shear strength improving agent, a resistance reducing agent and an emulsifier in turn;

3) optimally selecting the 3# white oil with the content of 30 percent in the concentrated solution;

4) optimally selecting 1.5 percent of stabilizer in the concentrated solution;

5) optimally selecting 2% of the extracting and cutting agent in the concentrated solution;

6) optimally selecting 40% of the drag reducer in the concentrated solution;

7) optimally selecting 3% of emulsifier in the concentrated solution;

8) preparing concentrated solution according to the proportion content of the steps.

The further optimized technical proposal is that the stabilizer in the step 4) is an organic soil polymer stabilizer.

The further optimized technical proposal is that the shear-improving agent in the step 5) is triethylene glycol monobutyl ether.

The further optimized technical proposal is that the emulsifier in the step 7) is span 80 with the component of sorbitan fatty acid ester.

Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the invention combines the prior art to research and develop the proportion of various reagents, and finally selects the fixed charging sequence and proportion thereof through comparison of repeated test data, firstly adds 30% of oil phase (3 # white oil), then adds 1.5% of polymer stabilizer (organic soil), 2% of shear-improving agent (triethylene glycol monobutyl ether), 40% of resistance-reducing agent and finally 3% of emulsifier (span-80). The prepared concentrated solution has high flowback efficiency which can reach more than eighty percent, good high-temperature resistance and shear resistance, can meet the requirement of continuous construction, can be stopped at any time when meeting any problem in the construction process, has high adjustability, is environment-friendly, and can reduce the environmental pollution.

Drawings

FIG. 1 is a flow chart of the formulation of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in figure 1, the invention discloses a preparation method of a concentrated solution based on continuous fracturing, which comprises the following steps:

1) optimally selecting oil items, and selecting 3# white oil with the minimum density as a dispersion medium for preparing the concentrated fracturing fluid; the preparation of the fracturing fluid generally uses 0# diesel oil, but the price of the 0# diesel oil is more expensive than that of white oil, and the white oil is cheap and has wide sources. Therefore, white oil is selected as the dispersion medium. The types of white oil include 3# white oil, 5# white oil, 7# white oil, 10# white oil, 15# white oil, 26# white oil, 32# white oil, 36# white oil, 46# white oil and 68# white oil, and the 3# white oil with the lowest density should be selected in order to achieve good solubility of the friction reducer, and the 3# white oil is cheap and has a wide source. Therefore, 3# white oil which is wide in source, low in price and low in density is adopted as a dispersion medium for preparing the concentrated fracturing fluid. Since the No. 3 white oil was found to be an industrial product and to be less effective, it was purified by distillation.

2) Selecting a concentrated solution feeding sequence, wherein the concentrated solution feeding sequence comprises a dispersion medium, a stabilizer, a shear strength improving agent, a resistance reducing agent and an emulsifier in turn; the experiment is carried out on the raw materials such as white oil, a resistance reducing agent, a stabilizer, an emulsifier, a shear strength improving agent and the like according to different feeding sequences, except that the white oil, the stabilizer, the shear strength improving agent, the resistance reducing agent and the emulsifier are added according to the feeding sequences, and the other feeding modes have small particles which can not be dissolved after the resistance reducing agent is added. Observing different phenomena, selecting an optimal feeding sequence according to simple performance tests of layering time, viscosity and the like, and preparing the concentrated solution with the performance reaching the standard, so that the feeding sequence is finally determined to be white oil, a stabilizer, a shear improver, a resistance reducer and an emulsifier.

3) Optimally selecting the 3# white oil with the content of 30 percent in the concentrated solution; according to the determined feeding sequence of the concentrated solution, the viscosity and the stability of the concentrated solution are tested by taking the content of the white oil as a variable quantity, and finally, a proper percentage content of the white oil is determined; the time of demixing observed when preparing concentrates with different white oil contents, and it was found that the concentrates quickly demixed when the white oil contents were 25% and 30%, probably because the stabilizer and friction reducer were not fully hydrated due to too little oil phase content. When the content of the white oil is 40 percent and the percentage content is 30 percent, the layering time is not greatly different, so the stability is equivalent, but when the content of the white oil is too much, the content of the resistance reducing agent is relatively reduced, so the content of the white oil is more suitable for being about 30 percent in the preparation of the concentrated solution. When the white oil content is 30%, the phenomenon of delamination occurs after 30 hours.

4) Optimally selecting 1.5 percent of stabilizer in the concentrated solution; the polymer stabilizer has the functions of hydrating the resistance reducing agent and dissolving the resistance reducing agent in the concentrated solution for suspension, and the structure of the polymer stabilizer contains a large amount of hydroxyl groups which can form hydrogen bonds with the standing oil phase medium, so that the stabilizer can be connected by the hydrogen bonds in the oil phase medium, and the concentrated solution becomes a substance with a net structure with certain viscosity. Theoretically, a larger concentration of stabilizer is better, but in experiments it is also important to select the optimum polymer stabilizer concentration, since it is limited by various conditions. The principle of the addition of the stabilizer is the same as that of the white oil, and the stabilizer with different amounts is added under the condition that the contents of other components are not changed, so that the optimal percentage content is obtained. Concentrates of different stabilizer concentrations were prepared and the time to delamination was observed. The concentrate becomes more stable with increasing stabilizer content, but the delamination time is instead shortened after the polymer concentration is greater than 1.5%, probably because the effect of the polymer stabilizer on the drag reducer has reached a saturation state, so a suitable concentration of the polymer stabilizer is selected to be 1.5%, and when the concentration is 1.5%, the delamination time is 34 minutes.

5) Optimally selecting 2% of the extracting and cutting agent in the concentrated solution; after it is stirred with the polymer stabilizer, the stabilizer is not completely suspended in the dispersion medium because of its higher density, and a specific substance is required to suspend the stabilizer, and the amount of the shear-enhancing agent selected determines whether the polymer stabilizer can be uniformly distributed. The experimental method comprises the steps of adding different amounts of extracting and cutting agents after adding the stabilizer, standing for a certain time to see whether the stabilizer is a lower layer, and selecting the appropriate amount of extracting and cutting agents to perform the next experiment; adding different contents of the cutting extraction agent, and observing the influence of the content of the cutting extraction agent on the stabilizing agent. When the content of the shear improver is less than 2%, the polymer stabilizer can be settled, but when the content of the suspending agent reaches 2%, the added polymer stabilizer can be completely suspended, so that the content of the shear improver is selected to be 2%.

6) Optimally selecting 40% of the drag reducer in the concentrated solution; the method is characterized in that the drag reducer with different contents is added into the concentrated solution, the concentrated solution is more and more stable along with the increase of the content of the drag reducer, when the content of the drag reducer reaches 50%, the concentrated solution is also required to be layered, but when the content of the drag reducer is 40%, the concentrated solution is not obviously layered within 3 days, so that the content of the drag reducer is selected to be 40%.

7) Optimally selecting 3% of emulsifier in the concentrated solution;

it selects proper emulsifier

Because the HLB value of each emulsifier is different, their emulsifying effect is also different. Suitable emulsifiers will increase the stability and viscosity of the concentrate. Selecting four emulsifiers, namely Span-80, emulsifier No. 1, main and auxiliary emulsifiers and Tween-20.

Selecting proper emulsifier proportion

According to the determined emulsifier types, the preparation steps of the concentrated solution are unchanged, the addition amount of various emulsifiers is changed every time, and the concentrated solution is subjected to performance test to finally determine a proper emulsifier ratio so as to prepare the concentrated solution with the best performance.

After the emulsifiers with the same content and different types are added, the stability of the concentrated solution is influenced to a certain extent, particularly, after the Tween 20 is added, the rapid layering is carried out, the layering time is equivalent after the emulsifier No. 1 and the main and auxiliary emulsifiers are added, but after the Span-80 is added, the layering still does not occur after 72 hours, so the selected emulsifier is Span-80. After the types of the emulsifiers are determined, the addition of other raw materials is controlled to be unchanged, and the addition of the emulsifiers is changed, and finally, the concentrated solution is found not to be layered for 80 hours when the content of the emulsifiers is about 3%, so that the content of the selected emulsifiers is about 3%.

In summary, the content of the traditional Chinese medicine in the obtained concentrated solution and the charging sequence are as follows: firstly adding 30% of oil phase (3 # white oil), then adding 1.5% of polymer stabilizer (organic soil), 2% of cutting improving agent (triethylene glycol monobutyl ether), 40% of resistance reducing agent and finally adding 3% of emulsifier (span-80), and layering the product after 10 days.

The invention combines the prior art to research and develop the proportion of various reagents, and finally selects the fixed charging sequence and proportion thereof through comparison of repeated test data, firstly adds 30% of oil phase (3 # white oil), then adds 1.5% of polymer stabilizer (organic soil), 2% of shear-improving agent (triethylene glycol monobutyl ether), 40% of resistance-reducing agent and finally 3% of emulsifier (span-80). The prepared concentrated solution has high flowback efficiency which can reach more than eighty percent, good high-temperature resistance and shear resistance, can meet the requirement of continuous construction, can be stopped at any time when meeting any problem in the construction process, has high adjustability, is environment-friendly, and can reduce the environmental pollution.

Claims

1. A method for preparing a concentrated solution based on continuous fracturing is characterized by comprising the following steps: the preparation method comprises the following steps:

step 1), selecting an oil phase, and selecting 3# white oil with the minimum density as a dispersion medium for preparing a concentrated fracturing fluid;

step 2) selecting a concentrated solution feeding sequence, wherein the concentrated solution feeding sequence comprises a dispersion medium, a stabilizer, a shear-improving agent, a resistance-reducing agent and an emulsifier;

step 3), selecting the 3# white oil with the content of 30% in the concentrated solution;

step 4), selecting a stabilizer with the content of 1.5% in the concentrated solution;

step 5), selecting 2% of the extracting and cutting agent in the concentrated solution;

step 6), selecting 40% of the resistance reducing agent in the concentrated solution;

step 7), selecting 3% of emulsifier in the concentrated solution;

step 8) preparing a concentrated solution according to the proportion content in the step;

wherein the stabilizer in the step 4) is organic soil;

the extracting and cutting agent in the step 5) is triethylene glycol monobutyl ether;

the emulsifier in the step 7) is span 80 of sorbitan fatty acid ester.