WO2018026301A1

WO2018026301A1 - Well treatment method using polymeric fibres

Info

Publication number: WO2018026301A1
Application number: PCT/RU2016/000516
Authority: WO
Inventors: Владимир Александрович ПЛЯШКЕВИЧ; Ирина Александровна ЛОМОВСКАЯ
Original assignee: Шлюмберже Канада Лимитед; Шлюмберже Текнолоджи Корпорейшн; Шлюмберже Текнолоджи Б.В.; Сервисес Петролиерс Шлюмберже
Priority date: 2016-08-05
Filing date: 2016-08-05
Publication date: 2018-02-08

Abstract

The present invention relates to the field of oil and gas extraction. Proposed, for use in a composition for hydraulic fracturing, is a polymeric fibre coated with a finishing agent that contains a base oil, a lubricant based on said oil, both having a viscosity index of at least 120 determined according to standard ASTM D2270, or mixtures thereof. Also proposed are a composition for hydraulic fracturing which contains such fibres, a hydraulic fracturing method using said composition, and a method of producing said fibres. The present invention provides for improved dispersibility of the fibres in a carrier fluid, improved proppant transport in the fractures of a formation and reduced bridging of the fractures in the formation by the fibres, as well as increasing inflow area for formation fluids, which increases the effectiveness of the hydraulic fracturing method and improves well yield, and reducing energy expenditure when carrying out the hydraulic fracturing method, while being simple to carry out and not requiring great energy expenditure or labour costs.

Description

POLYMER FIBER FOR USE in the composition for hydraulic fracturing, a composition for hydraulic fracturing, a method of hydraulic fracturing, a production method

POLYMER FIBERS.

FIELD OF TECHNOLOGY

The present technical solution relates to the field of oil and gas production, namely to hydraulic fracturing, as well as to a composition for use in hydraulic fracturing operations, a fiber coated with a sizing agent for use in said composition, and also to a method for producing said fiber .

BACKGROUND

Hydrocarbon production from unconventional fields, for example, oil and gas low permeability reservoirs, such as shale reservoirs, dense sandstones, limestones, etc., has become relevant in the extraction of energy resources and this sector has been demonstrating a growing demand for technology in recent years.

Hydraulic fracturing (Fracturing) is a widespread method of stimulating oil and gas production. At the same time, long permeable cracks are created in the reservoir, which increases the inflow area and the flow rate of the well. In order for the resulting hydraulic fracture to remain open and permeable to fluids, proppant (proppant) is introduced into it. The choice of a fluid system is responsible for creating a crack with a certain length and placing proppant in it.

It is known that conventional fracturing systems are based on a gel in the form of a crosslinked polymer, and such highly viscous carrier fluids have been used for hydraulic fracturing in various types of formations. For some types of unconventional formations, such systems can also be successfully applied.

Due to their low cost and ease of use, water-based liquid systems are widely used in technologies for processing unconventional formations. The low viscosity of such fluid systems is very useful for creating extended and branched cracks in the rock, but the ability of the composition to transfer proppant, which depends on the viscosity of the carrier fluid, is reduced. Due to the ineffective proppant transfer by the composition, in low viscosity fluid systems, proppant sedimentation is rapid, which prevents proppant delivery to many secondary and tertiary fractures. This fact negatively affects the flow rate of a stimulated well, since it is believed that for unconventional reservoirs with low permeability, oil flow can be obtained through the creation of a branched system of connected fractures. The maximum flow rate from the treated formation is obtained if open fractures remain proppant-wedged and have a connection between the fractures.

The addition of fibers as a proppant transfer enhancing element in a low viscosity fluid system can significantly improve the horizontal and vertical proppant distribution in the fracture created. In such a fluid system, a low-viscosity fluid is responsible for the length and branching of the fracture system, and the suspension of fibers provides sufficient proppant transfer for optimal placement of proppant throughout the volume of the network of branched cracks.

The effectiveness of a suspension of fiber materials for proppant (sand) transfer was used in hydraulic fracturing operations using the FiberFRAC ™ and HiWAY ™ technologies (Schlumberger company). Since the fibers themselves in suspension at high concentrations tend to clog the created cracks (English - “bridging”), this property was used in the StimMORE * and MaxCOZ * Acid technologies (Schlumberger company).

However, the tendency to plug cracks in the fiber flow is a negative feature when it comes to hydraulic fracturing stimulation of low permeability reservoirs. The reason is that the low viscosity of the carrier fluid and the small width of the formed cracks enhances the clogging properties of the fiber material.

Thus, the maximum efficiency of hydraulic fracturing treatment when using a low-viscosity hydraulic fracturing carrier fluid is achieved if the fiber suspension has a minimal tendency to plug formation cracks (channels).

A technical solution is disclosed in patent application PCT / RU2014 / 000837 (WO2015160277 A1, 10/22/2015) "Treatment fluid", which describes a solution to improve proppant transfer in low-viscosity liquids by adding modified polymer fibers containing the composition of the silicone material by weight from 0.1 to 20%, which helps to control the deposition rate of proppant and to avoid the tendency to clog cracks.

However, the specified modification of the fibers with silicone material is a process that requires the use of special equipment and materials in the manufacture of fibers, which leads to a change in the technology of fiber production, and increases the energy and labor costs for the manufacture of fibers.

The nuances of using low-viscosity fluids in hydraulic fracturing compositions have been described above, however, some nuances also arise when using high-viscosity fluids for hydraulic fracturing. The main purpose when performing hydraulic fracturing with highly viscous fluids - The main purpose when performing hydraulic fracturing with highly viscous fluids is to create high and wide primary cracks. However, in cases of stimulation of formations with a relatively small height of the productive zone, the board, for example, sandstones, strictly select the viscosity of the liquid. The possibility of pumping high proppant concentrations at relatively low pumping speeds is ensured by the high transport properties of such a fluid, which depend directly on the stability of the viscosity characteristics. Premature decomposition of the fluid (conditions of high temperature, high shear stress rates), or incorrect selection of components, cause a sharp drop in the transport properties of the fluid and the impossibility of further work and / or a decrease in the efficiency of hydraulic fracturing. The addition of fibers to highly viscous liquids consists in an additional improvement in transport properties and prevention of rapid proppant sedimentation under static conditions, i.e. after uploading. The prevention of rapid subsidence is caused, first of all, by the relatively large height of the cracks obtained as a result of the use of highly viscous fluids. In high viscosity fracturing fluids, clogging of cracks with fibers occurs at lower injection rates than in low viscosity fluids.

Chemical sizing is used in the textile industry to turn yarn or finished fabric into useful material. This kind of surface treatment is done after dyeing the yarn / fabric to improve appearance, antistatic properties, or to improve the tactile sensations of the treated tissue.

However, the procedure for treating the fibers with a sizing agent has not previously been used to improve the properties of the fibers in the hydraulic fracturing composition in downhole operations.

Thus, in the technical field there is a need to improve the properties of the fibers for use in the composition for conducting hydraulic fracturing, using methods that do not require significant energy and labor.

SUMMARY OF THE ESSENCE

The present disclosure proposes the use of a polymer fiber coated with a sizing agent comprising a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof.

The present disclosure provides improved dispersibility of the fibers in the carrier fluid in the hydraulic fracturing composition, improved proppant transfer by the suspension of the fibers in the fractures, improved dispersibility of the hydraulic fracturing composition in the fractures, reduced clogging of the fractures with the fibers, increases the area of flow of formation fluids into the fractures, which increases the effectiveness of the method of hydraulic fracturing and increases the flow rate of the well, while the present disclosure has ease of implementation, not requiring significant energy or labor costs, and also reduces the resource requirements of the equipment used for hydraulic fracturing (hydraulic fracturing), which reduces energy consumption for the implementation of hydraulic fracturing.

The present disclosure contains the following main aspects listed below:

In one aspect, the present disclosure comprises a polymer fiber for use in a fracturing composition. The fiber is coated with a sizing agent, which includes a base oil, a lubricant based on said oil, having a viscosity index of at least 120 as determined according to ASTM D2270, or mixtures thereof.

In another aspect, the present disclosure comprises a fracturing composition. The composition contains: carrier fluid

proppant

polymer fibers coated with a sizing agent, including a base oil, a lubricant based on these oils, having a viscosity index greater than 120 when determined according to ASTM D2270, or mixtures thereof.

In yet another aspect, the present disclosure comprises a hydraulic fracturing method. The method comprises the steps of:

pumping a composition for hydraulic fracturing containing a carrier fluid, proppant, polymer fibers through a well into an underground formation, wherein

the fibers are coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof.

In yet another aspect, the present disclosure comprises a method for producing polymer fibers for use in a fracturing composition. The method comprises the steps of:

coating the polymer fiber with a sizing agent by means of a coating agent, the sizing agent comprising a base oil, a lubricant based on said oil having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof,

dried fiber coated with a sizing agent.

In another aspect, the present disclosure comprises a polymer fiber for use in a fracturing composition obtained by the method of any one of claims. 36-42, wherein the fibers are coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

1 - (A) illustrates the dispersion of a fracturing composition containing untreated fibers in a fracture, (B) illustrates dispersing a fracturing composition containing fibers coated with a sizing agent in a fracture of a formation.

DETAILED DESCRIPTION OF EMBODIMENTS

The following description of embodiments of the disclosure is illustrative only and is not intended to limit the present disclosure, its use, or use cases. It should be understood that the disclosure allows for other embodiments, and some of their details allow modification in various aspects without departing from the essence of the disclosure. Signs mentioned in the singular do not exclude a plurality of signs, unless otherwise indicated.

The disclosure indicates some non-limiting examples of possible means for implementing the claimed disclosure, but one skilled in the art should understand that the nature of the disclosure is not limited to a specific implementation. To implement the disclosure, any hardware known in the art and suitable for performing the disclosure may be used. All numerical values and ranges disclosed in the present description should first be understood as modified by the word "approximately", and then, repeatedly, without the specified word "approximately".

The propagation (filling) of hydraulic fractures by a composition containing a low-viscosity carrier fluid differs from the process of fracturing fractures by a composition containing a highly viscous (cross-linked) carrier fluid. The benefits of low viscosity carrier fluids are especially relevant for stimulating shale deposits.

During hydraulic fracturing with compositions containing low-viscosity carrier fluids, a fracture in the formation creates a much lower and narrower, but longer and branched one, i.e. in fact, the contact area of the bottomhole zone and the reservoir increases. In general, the higher the viscosity of the liquid system, the wider, higher, and shorter the crack is created, and the lower the viscosity, the lower the crack, the longer. For successful injection of compositions containing low-viscosity fluids (i.e., to exceed reservoir pressure to maintain a crack open during hydraulic fracturing operations), a higher (3-5 times) injection speed is maintained compared to the injection of compositions containing highly viscous carrier fluids. Undesirable premature tendency clogging of the crack with proppant and fibers, which can cause the impossibility of further hydraulic fracturing, in the case of compositions containing low-viscosity carrier fluids, is very high. To prevent such blockage, the injection rate should be increased and the proppant concentration should be reduced, which ultimately causes less quality filling of the fracture with proppant and a decrease in the efficiency of the well.

The addition of fibers to a low viscosity carrier fluid increases the load capacity of the low viscosity fluid. However, there is a chance of clogging of the crack with fiber, which depends on several parameters, listed below: a. Carrier fluid viscosity: the lower the viscosity, the greater the likelihood of clogging of the crack with fiber.

b. Pumping speed: the higher the speed, the less the likelihood of clogging, however, an excessive increase in speed can disrupt the creation of the correct crack geometry and require tangible equipment resources, which increases the cost of work.

c. Proppant concentration: the higher the proppant concentration, the worse the proppant transfer and the less branched fracture geometry.

d. Crack width: the smaller the crack width, the easier it is to plug it with any solid particles, including fibers.

e. Proppant particle size: the smaller, the better the transfer and more uniform filling of the crack. Thus, the clogging of cracks with fibers in low viscosity fluids is higher than in high viscosity fluids (crosslinked gels) due to the lower viscosity of the fluid and the smaller width of the crack.

f. Fiber concentration: the risk of clogging increases with its increase. g. Fiber dispersion uniformity: Dispersion deterioration causes an increase in local fiber concentrations.

In this case, undesirable clogging of cracks with fibers in the case of using highly viscous hydraulic fracturing fluids is also possible, it occurs at lower injection rates than for low-viscosity fluids.

Since sizing fibers during production, as well as during hydraulic fracturing, are exposed to various temperatures and media, the sizing agent for applying to the fibers should create a uniform a coating resistant in a wide temperature range, providing a slippery surface that can reduce the adhesion of fibers, improve their dispersibility.

The authors of the present disclosure found that polymer fibers coated with a sizing agent, including a base oil, a lubricant based on the specified oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, have a uniform coating, have improved dispersible properties in the carrier fluid, show a reduced tendency to adhesion between the fibers themselves, as well as between the fibers and any surfaces with which they come into contact during injection into the reservoir, and so on at the same time, the likelihood of formation of bundles of fibers that can plug the fracture is reduced, such fibers provide improved proppant transfer to the fractures, improve the dispersibility of the fracturing composition in the reservoir fracture, which allows creating an effective fracture system that increases the flow of formation fluids to the bottom of the well, which increases well production and hydraulic fracturing efficiency. At the same time, the use of such fibers in the hydraulic fracturing method (Fracturing) reduces the resource requirements of the equipment used during hydraulic fracturing, which reduces energy costs for the implementation of hydraulic fracturing, and the method for producing such fibers has a simple implementation that does not require large energy and labor costs.

The lubricity of the oil is closely related to the viscosity values of the oils. For example, an oil having a viscosity as low as possible allows two surfaces not to touch. If the value of the oil viscosity is too low, the surfaces come into contact and the friction increases, if the value of the oil viscosity is too high, friction losses occur and a negative effect on the uniformity of the surface coating with oil is possible.

Oil viscosity index is a relative value showing the degree to which oil viscosity changes with temperature. The higher the oil viscosity index value, the lower the oil viscosity is temperature dependent.

According to the classification of the American Petroleum Institute (API), base oils are divided into five groups according to their inherent viscosity index. Base oils of the first and second groups have a viscosity index value of less than 120, which characterizes a large dependence of the viscosity of these oils on temperature. Base oils of the third, fourth and fifth groups are characterized by a viscosity index of at least 120, which means that the viscosity of these oils is subject to relatively small changes in a wide temperature range, which allows the use of these oils in a wide temperature range.

Oils of the third group, according to the API classification, are obtained by the method of catalytic hydrocracking, and contain a relatively large proportion of saturated hydrocarbons (CAS number # 64742-54-7). The oils of the fourth group are synthetic oils based on polyalphaolefins, (CAS # 68649-12-7, CAS # 68649-l l-6), the oils of the fifth group are synthetic oils, including polyalkylene glycols, polyesters, and more. The term "lubricant" means a lubricant product based on the specified oil, which may contain various additives known to specialists in the field of technology, the lubricant may also include a base oil mixed with non-aqueous diluent known to a person skilled in the technical field, and with the viscosity index for the resulting solution is at least 120. Saturated and unsaturated hydrocarbons of a number of alkanes and alkenes with a carbon chain length are primarily used as diluents and at least 5 (pentane, hexane, etc.). It is paramount to coat the fibers with undiluted oils or lubricants having a viscosity index of at least 120, as determined according to ASTM D2270.

In one embodiment, the sizing agent may include a base oil with a viscosity index of at least 120 as determined according to ASTM D2270, in another embodiment, the sizing agent may include a lubricant based on said base oil or a mixture of a lubricant and a base oil . The sizing agent may be selected from mineral oil, synthetic oil, or mixtures thereof. The sizing agent may have a viscosity in the range of 2-40 cSt at 40 ° C.

Fibers suitable for processing with a sizing agent, including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, can be any polymer fibers used to create compositions for hydraulic fracturing and well-known specialist in the field of technology. For example, fibers can be made of polyesters (polylactide, polyglycolide, polyethylene terephthalate, polybutylene terephthalate, etc.), polyamides (nylon-6, nylon-6.6, nylon-12, etc.), polyolefins (polypropylene, polyethylene etc.), cellulose fiber, viscose fiber, acetate fiber, or combinations thereof. The fibers may be selected from degrading or non-degrading fibers, or mixtures thereof. The fibers may be of direct or indirect shape, or may be a mixture of direct and indirect fibers. The fibers can have the following dimensions: a diameter in the range of from about 3 to about 40 microns, especially from about 3 to about 7 microns, a length in the range of from about 3 to about 12 mm, especially from about 3 to about 6 mm. Fibers can be selected from single component fibers, bicomponent fibers or multicomponent fibers, or mixtures thereof. Mostly, the fibers according to the present disclosure are polylactides, polyethylene terephthalate, polybutylene terephthalate, cellulosic or viscose fibers. These fibers are most effective in improving the transport properties of the carrier fluid in the composition for hydraulic fracturing and economic feasibility.

The value of the mass fraction of the coating from the sizing agent on the fibers, calculated on the total weight of the fibers, is selected from the range of effective values of the mass fraction of the coating. The term "range of effective values of the mass fraction of the coating" refers to those values at which the fibers coated with a sizing agent exhibit improved properties that lead to a decrease in the tendency to clog channels.

The authors of the solution found that polymer fibers coated with a sizing agent, including a base oil, a lubricant based on the specified oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or a mixture thereof, exhibit improved properties already at about 0.5% of the mass, to at least about 50% of the mass of the coating, based on the total weight of the fibers.

At values below 0.5% of the mass, a slight improvement in the properties of the fibers may also occur or the improvement does not occur.

In this case, the greatest effect is manifested when the mass fraction of coating of the sizing agent on the fibers is equal to from about 1% of the mass, calculated on the total mass of fibers and up to about 30% of the mass. At values of more than 50% of the mass, based on the total weight of the fibers, no further improvement in properties is observed.

Thus, under the term “range of effective coating values”, a range of from about 0.5% by weight to at least about 50% by weight of the coating sizing agent, based on the total fiber weight, mainly from about 1%, can be characterized mass, up to about 30% of the mass, calculated on the total weight of the fibers.

The method for producing polymer fibers according to the disclosure comprises the following steps.

Coat the polymer fiber with a sizing agent by means of a coating agent. The coating agent may be a sizing agent coating roller. The specified roller is immersed in a sizing agent, while coating the fiber with the specified sizing agent by rolling the roller through the fiber. The coating can also be carried out by spraying the sizing agent on the fiber, where the coating agent is a spraying device for applying the sizing agent, for example, a nozzle, a spray gun and the like. The temperature of application of the sizing agent does not exceed the glass transition temperature of the fiber material (for example, if the polymer fiber is polyester (polylactide, polyethylene terephthalate, polybutylene terephthalate), then the temperature of application of the sizing agent does not exceed 40-70 degrees Celsius). The coating agent may be a container with a sizing agent, wherein said fiber is coated with a sizing agent by immersing said fiber in a container with a sizing agent, and the fiber is mixed vigorously in said container, and then the fibers coated with the sizing agent are discharged. If there is an excess of the sizing agent deposited on the fibers, then it can be removed by pressing. The authors of the solution note that the selected type of fiber (polyamide (nylon-6, nylon-6.6), polyolefin (polyethylene, polypropylene) and cellulose (including viscose), polyester (polylactides, polyethylene terephthalate, polybutylene terephthalate) do not affect the properties of the final coating from sizing agent, as well as the content of the achieved final coating on the fiber. Then, the coated fiber from the sizing agent is dried, and the drying temperature of the coated fiber from the sizing agent affects the achievement of optimal dispersibility properties of the obtained fibers in the carrier fluid and is set at least 20 degrees Celsius below the melting temperature of the fiber material. Mixing, unloading, drying and, in some cases, spinning of the fibers can be carried out by any means known to the person skilled in the art, such as mixers, screw conveyors, rollers, drying ovens, spinning devices, and the like. The coating of the fibers can be carried out at the final stages in the industrial production of fibers, when devices known in the industry are used to coat / lubricate the fibers. Also, coating of the sizing agent on the fibers can be carried out when preparing the fracturing composition before pumping the composition into the well.

Polymer fibers coated with the aforementioned sizing agent can be successfully used in hydraulic fracturing compositions.

The fracturing composition according to the present disclosure includes a carrier fluid, proppant, and polymer fibers, wherein said fibers are coated with a sizing agent including a base oil, a lubricant based on said oil having a viscosity index of at least 120 at definition according to ASTM D2270, or mixtures thereof.

The carrier fluid can be a low viscosity fluid, which can be water, an aqueous solution of polyacrylamide, guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl cellulose, xanthan gum, sodium alginate, a suspension of polyacrylonitrile, as well as derivatives thereof known to those skilled in the art .

The carrier fluid may also be a highly viscous carrier fluid known to a person skilled in the art, which can be used the above aqueous solutions of polymers with a crosslinking agent based on boric acid, soluble salts of zirconium (IV) and aluminum (III), or combinations thereof.

The viscosity of the carrier fluid can lie in the range: for low-viscosity (non-crosslinked) fluids - from about 1 · 10 ^"3 Pa - s to about 5 · 10 ^{" 2} Pa - s, measured at a shear rate of 170 s ^"1 and a temperature of 25 ° C, for example, from about 2 · 10 ^{" 3} Pa s to about 3.5 · 10 ^"2 Pa s, and above all, from 2 · 10 ^{" 3} Pa s to 2 - 10 ^"2 Pa s, for highly viscous (crosslinked) liquids - from about 1 - 10 ^{" 1} Pa s to about 20 Pa s, measured at a shear rate of 170 s ^"1 and a temperature of 25 ° C, for example, from about 2 10 ^{" 1} Pa s to about 5 10 ^"1 Pa s, and above all, from about 2 · 10 ^" 'Pa s to about 3 10 ^"1 Pa s.

Proppant for filling cracks during hydraulic fracturing must have high mechanical strength and not collapse under conditions of volumetric compression under the action of pressure of overlying rocks. As proppant, particles of any material that is typically used as a proppant in the technical field can be used. For example, materials such as ceramics, sand, bauxite, glass, walnut shells, polymer proppant or mixtures thereof can be used. Proppant materials can vary in density from about 2.4 to 3.8 g / cm ³ , mechanical strength in the range of application of about 300-1,500 atm, particle size from about 0.1-2 mm.

A fracturing composition comprising fibers coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, may further comprise various additives, well-known specialist in the field of technology, according to existing needs. For example, the composition may contain a clay stabilizer, antifoam agents, emulsifiers, high temperature stabilizing agents, corrosion inhibitors, etc.

The hydraulic fracturing method according to the present disclosure comprises the following steps: pumping the hydraulic fracturing composition containing the aforementioned carrier fluid, proppant, polymer fibers through a borehole into an underground formation, wherein the fibers are coated with a sizing agent, including base oil, lubricant based on said oil having a viscosity index of at least 120 as determined according to ASTM D2270, or mixtures thereof.

The flow rate, the rate of injection of the specified composition into the underground formation is maintained at a level that does not cause plugging of the formation cracks with the injected fluid. Moreover, a specialist in the field of technology on the basis of general knowledge and the prior art, the choice of values of flow rate and injection rate of the composition for hydraulic fracturing, depending on the specific existing conditions and specific operations of hydraulic fracturing. For hydraulic fracturing, any device known to a person skilled in the art can be used.

EXAMPLES

Reducing the tendency of clogging of the channels with fibers containing a coating of a sizing agent in the composition for hydraulic fracturing.

The beneficial effects of using fibers in a hydraulic fracturing (HF) composition coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, are demonstrated in a series of laboratory experiments on the example of the use of fibers from various polymeric materials. Application of a sizing agent is possible on fibers of various shapes (direct, indirect, for example, corrugated).

Example 1

This example shows the effectiveness of reducing crack plugging when using a suspension of fibers containing fibers coated with a sizing agent, in comparison with a suspension of fibers containing untreated fibers (see Table 1 below). The following oils and lubricants were used as a sizing agent:

a. Idemitsu Zepro EcoMedalist SAE 0W20 API SN engine mineral oil (N ° l oil)

b. Synthetic Gear Oil Idemitsu MTF SAE 75W90 API GL-5 (Oil N ° 2)

c. Synthetic transmission oil Havoline Synthetic ATF Multi-Vehicle DEXRON-VI (oil J \ ° 3)

d. Chevron Ulti-Plex Synthetic Grease EP Lubricant (Ν ° 4 Oil) The above oils and lubricants have a viscosity index of at least 120 when determined according to ASTM D2270. To evaluate the effect of sizing (surface treatment) on the tendency of a fiber suspension to clog flow channels, a suspension of raw fibers in a low-viscosity carrier fluid was selected as an initial example, for which a tendency to clog the fibers is known.

Test conditions for the fiber suspension in the slit channel: 1 mm wide slit, loading fibers at a concentration of 2.2 g / l (18 lb / 1,000 gallons). The carrier fluid is an aqueous solution of polyacrylamide with a viscosity of not more than 2 · 10 ^"2 Pa s at 170 s ^{" 1} and at room temperature. Carrier aqueous liquid contains 0.1 wt.% (1 gallon / 1000 gallons) of polyacrylamide polymer. Fibers coated with said sizing agents are polyester fibers (polylactic acid fibers (PML) from Trevira GmbH).

The example shows that coating polymer fibers, including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or a mixture thereof, reduces the tendency to clog channels when pumping a fiber suspension.

Table 1 The tendency of a suspension of fibers to clogging the channel.

Consumption Linear Pure Oil Oil Oil Oil Oil suspension fiber speed W, 20 JN ° 2, 30 JN ° 3, 20 JN ° 4, 15 ml / s suspension mass% mass% mass% mass% at

pumping

across

gap

cm / s

100 1 1. 1 + + + + +

200 22.2 + + + + +

300 33.3 + + - - -

400 44.4 + - - - -

500 55.6 + - - - -

600 66.7 - - - - -

700 77.8 - - - - -

800 88.9 - - - - - Designations for table 1:

+ gap clogging occurs

"-" no gap plugging

In the following series of experiments, it was shown that polymer fibers, when coated with a sizing agent, including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, with mass fraction of the coating from about 0.5% of the mass, to at least about 50% of the mass, calculated on the total weight of the fibers show a decrease in the tendency of the fibers to clog the channel.

In this case, the greatest effect is manifested when the mass fraction of coating of the sizing agent on the fibers is equal to from about 1% to about 30% of the mass, calculated on the total weight of the fibers.

Similar to the experiments in Example 1, other polyester fibers (polyethylene terephthalate, polybutylene terephthalate), polyolefin fibers (polyethylene, polypropylene), cellulose / viscose fibers, polyamide fibers (nylon-6, nylon-66, nylon -12) coated with a sizing agent (various oils and lubricants having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof) in an amount of 0.5; 5; 10; 20, 30, 50% by weight, based on the total weight of fibers suspended in low-viscosity and high-viscosity carrier fluids (with proppant and without proppant) when pumped through slits of 1 and 5 mm.

Example 2

A suspension was prepared comprising polyester fibers (polylactide) coated with a sizing agent (synthetic transmission oil Idemitsu MTF SAE 75W90 API GL-5 (oilL)) in an amount of 0.5; one; 5; 10; twenty; thirty; 50% by weight based on the total weight of the fibers, a low-viscosity carrier fluid (aqueous solution of polyacrylamide or xanthan gum or carboxymethyl cellulose). The fibers of the following geometry were used: 6 mm long, 12 microns in diameter, circular cross section, straight shape. The composition was pumped through a 1 mm wide slotted channel (results in Table 2). Table 2.

Suspension of polyester 100 PD 200 22.2 fibers coated

sizing agent - oil] \ ° 2 (30% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Polyester suspension 300 33.3 600 66.7 coated fibers

sizing agent - oil. M ° 2 (50% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Example 3

A composition for hydraulic fracturing was prepared, including polyester fibers (polylactide fibers, 6 mm long, 12 microns in diameter, circular cross section, straight shape) coated with a sizing agent (oil. M ° 2), in an amount of 1; 5; 10; 20, 30% by weight based on the total weight of the fibers, low-viscosity carrier fluid (aqueous solution of polyacrylamide or xanthan gum or carboxymethyl cellulose; proppant (CarboProp® with an average density of 3.2 g / cm ³ , size 0.4-0.8 diameter mm, concentration 240 g / l). The composition was pumped through a slotted channel with a width of 5 mm. The results on the example of polylactide fibers (PL A) are shown in Table 3.

Table 3.

Suspension of polyester 100 2.22 200 5.55 coated fibers

sizing agent - oil ° 2 (5% of the mass, calculated

per mass of fibers) in

low viscosity fluid

Suspension of polyester 100 2.22 200 5.55 coated fibers

sizing agent - oil N ° 2 (10% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Suspension of polyester 100 2.22 200 5.55 coated fibers

sizing agent - Ml2 oil (20% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Suspension of polyester 100 2.22 200 5.55 coated fibers

sizing agent - o2 oil (30%) of the mass, in

based on the mass of fibers) in

low viscosity fluid

Example 4

A suspension of polyester fibers was prepared (the results are illustrated by polylactide fibers, 6 mm long, 12 microns in diameter, circular cross section, straight shape) coated with a sizing agent (oil> G ° 2) in an amount of 1; 5; 10; twenty; 30% by weight based on the total weight of the fibers, in a highly viscous carrier fluid (crosslinked carboxymethyl cellulose gel), without proppant, and pumped through a 1 mm wide slotted channel.

Table 4.

Description of the fiber sample Clogging the channel Free flow through the channel

Linear flow rate Linear suspension flow rate, suspension speed, ml / min liquid velocity ml / min liquid through the slit, cm / s slit, cm / s

(1) (2) (3) (4) (5) Untreated polyester 200 22.2 300 33.3 fibers in low viscosity

liquids

Suspension of polyester 100 11.1 200 22.2 coated fibers

sizing agent - oil. (1% of the mass, calculated

per fiber mass) in

low viscosity fluid

Suspension of polyester 100 11.1 200 22.2 coated fibers

sizing agent - oil> (5% of the mass, calculated

per fiber mass) in

low viscosity fluid

Suspension of polyester 100 11.1 200 22.2 coated fibers

sizing agent - oil N ° 2 (10% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Suspension of polyester 100 11.1 200 22.2 coated fibers

sizing agent - oil> G ° 2 (20%) of the mass, in

based on the mass of fibers) in

low viscosity fluid

Suspension of polyester 100 11.1 200 22.2 coated fibers

sizing agent - oil 2 (30% of the mass, in

based on the mass of fibers) in

low viscosity fluid

Example 5

A composition for hydraulic fracturing was prepared, including polyester fibers (illustrated is an example of polylactide fibers, 6 mm long, 12 microns in diameter, round cross section, straight shape) coated with a sizing agent (in an amount of 1; 20; 30; 50% by weight based on the total mass of fibers, in a low-viscosity carrier fluid (aqueous solution of polyacrylamide), with CarboISP® proppant (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through the slot 5 mm wide channel. Table 5.

Example 6

A suspension of polyester fibers was prepared (for example, polylactide fiber, 6 mm long, 12 microns in diameter, round cross section, straight shape) coated with a sizing agent NGN FUTURE 0W-20 API SN (oil 1 ° 5, polyalphaolefin base, group IV according to API classification ), in the amount of 1; twenty; thirty; 50% by weight based on the total weight of the fibers, in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), without proppant, and pumped through a 1 mm wide slot channel. A decrease in the tendency to clog the channel when pumping fibers coated with this sizing agent was shown (results in Table 6).

Table 6.

Example 7 A composition for hydraulic fracturing was prepared, including polyester fibers (for example, polylactide fibers, 6 mm long, 12 microns in diameter, round cross section, straight shape) coated with NGN FUTURE 0W-20 API SN sizing agent (oil ° 5, polyalphaolefin base, group IV according to API classification, number C AS 151006-62-1), in the amount of 1; twenty; 50% by weight based on the total weight of the fibers, in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), with proppant CarboISP® (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through a slot channel 5 mm wide. A decrease in the tendency to clog the channel was shown when pumping a composition containing fibers coated with this sizing agent (results in Table 7).

Table 7.

liquids Example 8

A suspension of polyester fibers was prepared (for example, polylactide fiber 6 mm long, 12 microns in diameter, round cross section, straight shape), sizing with Poly (l, 2-butylene glycol) oil (oil-C ^ b, polyalkyl glycol base, group V according to classification API, number C AS 31923-86-1) in the amount of 1; twenty; 50% by weight based on the total weight of the fibers, in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), without proppant, and pumped through a 1 mm wide slot channel. A decrease in the tendency to clog the channel was shown when pumping a suspension containing fibers coated with this sizing agent (results in Table 8).

Table 8.

liquids Example 9

A composition for hydraulic fracturing was prepared, including polyester fibers (for example, polylactide fibers, 6 mm long, 12 microns in diameter, round cross section, straight shape) coated with a sizing agent Poly (l, 2-butylene glycol) (oil. ° 6, base polyalkyl glycol, group V according to API classification, CAS number 31923-86-1) in an amount of 1; twenty; 50% by weight based on the total weight of the fibers, in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), with proppant CarboISP (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through a slot channel 5 mm wide. It has been shown to reduce the tendency to clog the channel when pumping a composition containing fibers coated with this sizing agent.

Table 9.

low viscosity fluid Example 10

A composition was prepared for hydraulic fracturing, including polypropylene fibers (6 mm long, 12 microns in diameter, circular cross section, straight shape), saponified with the following oils: CheZ oil, oil. Ch ° 5, eb oil, in an amount of 10% by weight based on total fiber mass; in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), with the proppant CarboISP® (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through a slot channel 5 wide mm A decrease in the tendency to clog the channel was shown when pumping a composition containing fibers coated with these sizing agents.

Table 10.

liquids Example 11

A composition was prepared for hydraulic fracturing containing nylon-6 fibers (6 mm long, 12 microns in diameter, round cross section, straight shape), sizing with the following oils: oil ЗЗззЗ, oil "5, oil ^ b, in an amount of 10% by weight, calculated on the total mass of fibers; in a low-viscosity carrier fluid (aqueous solution of polyacrylonitrile), with the proppant CarboISP® (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through a slot channel 5 wide mm (results in Table 11).

Table 11.

Example 12

A composition was prepared for hydraulic fracturing, including viscose fibers (6 mm long, 12 microns in diameter, circular cross section, straight shape), sizing with the following oils: MeZE oil, Oils М ° 5, eb oil, in an amount of 10% by weight based on the total weight of the fibers; in low viscosity carrier fluid (aqueous solution polyacrylonitrile), with a proppant CarboISP® (density 3.2 g / cm ³ , average particle size 0.4-0.8 mm, content 240 g / l), and pumped through a slot channel 5 mm wide (see Table 12 )

Table 12.

Example 13

In this example, with reference to FIG. 1, the dispersion efficiency of coated fibers of a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or a mixture thereof, is illustrated. in the composition for hydraulic fracturing during pumping through the formation fracture, in comparison with the untreated fibers in the composition.

Experiments on the flow of a suspension through a vertical narrow channel show the difference in the behavior of untreated and treated fibers in the case of a flow of proppant fiber suspension. It is seen that the suspension with processed fibers provides improved proppant transfer in narrow channels (laboratory model of hydraulic fracture).

Parameters of the laboratory flow model: cell length - 1500 mm, height 400 mm; internal width (distance between walls) - 2 mm, suspension pumping speed (linear flow rate) 0.30 m / s. The cell is made of two transparent sheets of plexiglass. The described laboratory conditions allow us to simulate the flow of the suspension during hydraulic fracturing treatment of the rock.

As can be seen from FIG. 1 (A), injection of a composition with raw fibers leads to blockage of the channel in the input region of the slotted channel D ₀ .

As can be seen from Figure 1 (B), the injection of a composition with fibers coated with a sizing agent results in uniform distribution of the fibers and proppant throughout the volume of the slit channel Df. In this case, the longitudinal scale of the proppant placement coincides with the length of the slotted channel Df.

Thus, polymer fibers coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof, have improved dispersibility in a fracture of a formation, and do not form a plugging of a formation crack.

It should be noted that the present disclosure is not limited to the above specific embodiments, and various modifications and changes can be made to them without deviating from the essence of the present disclosure, which is expressed in the attached formula. The terms “contains”, “includes” and their analogs are used in this description in a non-restrictive sense, i.e. in the sense of an open list, and not in an exceptional sense, and therefore do not exclude the presence of other possible components, elements, steps, etc. In the exceptional sense, only the term “consisting of” is used.

Claims

CLAIM

1. A polymer fiber for use in a hydraulic fracturing composition, wherein the fiber is coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof.

2. The fiber according to claim 1, in which the mass fraction of the coating of the sizing agent is from about 0.5 to at least about 50% of the mass, calculated on the total weight of the fibers, mainly from about 1 to about 30% mass, calculated on the total weight of the fibers.

3. The fiber according to claim 1 or 2, in which the base oil includes mineral oil, synthetic oil, or a mixture thereof.

4. The fiber according to claim 1 or claim 2, wherein the base oil comprises an oil selected from group III, IV, V base oils according to the classification of the American Petroleum Institute (API) or a mixture thereof.

5. The fiber according to claim 1 or 2, in which the sizing agent has a viscosity value of about 2-40 cSt at 40 ° C.

6. The fiber according to claim 1, comprising at least one of polyesters, polyamides, polyolefins, cellulose fiber, viscose fiber, acetate fiber, or combinations thereof.

7. The fiber according to claim 1 or claim 6, selected from degrading fibers or non-degrading fibers or mixtures thereof, the fiber has a direct and / or indirect shape, and the fiber is at least one of a single component fiber, a two-component fiber or multicomponent fiber

8. The fiber according to claim 1 or claim 6, having a diameter in the range from about 3 microns to about 40 microns, mainly from about 3 microns to about 7 microns, a length in the range from about 3 mm to about 12 mm, mainly approximately 3 mm to about 6 mm.

9. Composition for hydraulic fracturing, containing:

carrier fluid

proppant polymer fibers coated with a sizing agent, including a base oil, a lubricant based on these oils, having a viscosity index greater than 120 when determined according to ASTM D2270, or mixtures thereof.

10. The composition according to claim 9, in which the mass fraction of the coating of the sizing agent is from about 0.5 to at least about 50% of the mass, calculated on the total weight of the fibers, mainly from about 1 to about 30% mass, calculated on the total weight of the fibers.

11. The composition according to claim 9 or 10, in which the base oil includes mineral oil, synthetic oil, or a mixture thereof.

12. The composition according to claim 9 or 10, in which the base oil includes an oil selected from base oils of group III, IV, V according to the classification of the American Petroleum Institute (API) or a mixture thereof.

13. The composition according to claim 9, in which the sizing agent has a viscosity value of about 2-40 cSt at 40 ° C.

14. The composition according to claim 9, in which the fibers include at least one of polyesters, polyamides, polyolefins, cellulose fiber, viscose fiber, acetate fiber, or combinations thereof.

15. The composition according to claim 9, in which the fibers are selected from degrading fibers or non-degrading fibers or mixtures thereof, the fibers have a direct and / or indirect shape, the fibers being at least one of one-component fibers, two-component fibers, or multicomponent fibers

16. The composition according to claim 9, in which the fibers have a diameter in the range from about 3 microns to about 40 microns, mainly from about 3 microns to about 7 microns, a length in the range from about 3 mm to about 12 mm, mainly , from about 3 mm to about 6 mm.

17. The composition according to claim 9 in which the fiber content in the composition is in the range from about 0.48 g / l to about 4.8 g / l (from 4 to 40 pounds / 1,000 gallons), mainly in the range from about 0.5 g / l to about 2.2 g / l (6 to 18 pounds / 1,000 gallons).

17. The composition according to p. 9, in which the proppant content in the composition is in the range from about 0.03 g / l to about 1.2 g / l (0.25 to 10 pounds / 1,000 gallons), mainly in the range of from about 0.03 g / l to about 0.7 g / l (0.25 to 6 pounds / 1,000 gallons).

18. The composition according to claim 9, in which the value of the viscosity of the carrier fluid is selected in the range from about 1 · 10 ^{~ 3} Pa s to about 5 - 10 ^"2 Pas measured at a shear rate of 170 s ^{" 1} and a temperature of 25 ° With, for example, from about 2 · 10 ^"3 Pa s to about 3.5 · 10 ^{~ 2} Pas, and mainly from about 2 · 10 ^{" 3} Pa s to about 2 10 ^" ² Pa s, or from about 1 · 10 ^"1 Pa s to about 20 Pa s, measured at a shear rate of 170 s ^{" 1} and a temperature of 25 ° C, for example, from about 2 10 ^"1 Pa * s to about 5 - 10 ^{" 1} Pa * s, and the main thus, from about 2 · 10 ^"1 Pas to about 3 to 10 ^{" 1} Pas.

19. The composition according to claim 9, in which the carrier fluid includes at least one of water, an aqueous solution of polyacrylamide, guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl cellulose, xanthan gum, sodium alginate, a suspension of polyacrylonitrile, as well as their derivatives .

20. The composition according to claim 9, in which the carrier fluid includes at least one of an aqueous solution of polyacrylamide, guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl cellulose, xanthan gum, sodium alginate, suspension of polyacrylonitrile, as well as their derivatives, co a crosslinking agent based on boric acid, soluble salts of zirconium (IV) and aluminum (III), or a combination thereof.

21. The composition according to claim 9, additionally containing functional additives, including antifoam agents, emulsifiers, high temperature stabilizing agents, corrosion inhibitors, or combinations thereof.

22. The composition according to claim 9, in which the proppant has a particle size of about 0.1 to 2 mm, a density of from about 2.4 to about 3.8 g / cm ³ , wherein the proppant includes ceramic, sand, bauxite, glass, walnut shell, polymer proppant, or mixtures thereof.

23. A method of hydraulic fracturing, comprising:

pumping a fracturing composition containing a carrier fluid, proppant, polymer fibers through a well into an underground formation, wherein the fibers are coated with a sizing agent including a base oil, a lubricant based on said oil, having a viscosity index of at least 120 when determined according to ASTM D2270, or mixtures thereof.

24. The method according to item 23, in which the flow rate, the rate of injection of the specified composition into the subterranean formation is maintained at a level that does not cause clogging of the fractures of the formation with the injected composition.

25. The method according to p. 23, in which the mass fraction of the coating of the sizing agent is from about 0.5 to at least about 50% of the mass, calculated on the total weight of the fibers, mainly from about 1 to about 30% mass, calculated on the total weight of the fibers.

26. The method according to p. 23 or p. 25, in which the fibers include at least one of polyesters, polyamides, polyolefins, cellulose fiber, viscose fiber, acetate fiber, or combinations thereof.

27. The method according to p. 23 or A.25, in which the fibers are selected from the group of degrading fibers or non-degrading fibers or mixtures thereof, the fibers have a direct and / or indirect shape, wherein the fiber is at least one of the one-component fibers, bicomponent fibers or multicomponent fibers.

28. The method according to p. 23 or 25, in which the fibers have a diameter in the range from about 3 microns to about 40 microns, mainly from about 3 microns to about 7 microns, a length in the range from about 3 mm to about 12 mm, mainly from about 3 mm to about 6 mm.

29. The method according to p. 23, in which the fiber content in the composition is in the range from about 0.48 g / l to about 4.8 g / l (4 to 40 pounds / 1,000 gallons), mainly in the range from from about 0.5 g / l to about 2.2 g / l (6 to 18 pounds / 1,000 gallons).

30. The method according to p. 23, in which the proppant content in the composition is in the range from about 0.03 g / l to about 1.2 g / l (0.25 to 10 pounds / 1,000 gallons), mainly in the range from about 0.03 g / l to about 0.7 g / l (0.25 to 6 pounds / 1,000 gallons).

31. The method according to p. 23, in which the value of the viscosity of the carrier fluid is selected in the range from about 1 · 10 ^"3 Pa s to about 5 10 ^{" 2} Pa s, measured at a shear rate of 170 s ^"1 and a temperature of 25 ° C, for example, from about 2 - 10 ^"3 groin to about 3.5 · 10 ^"2 Pass, and mainly from about 2 · 10 ^{" 3} Pass to about 2 10 ^" ² Pass or from about 1 10 ^{" 1} Pass to about 20 Pass, measured at a shear rate of 170 s ^"1 and a temperature of 25 ° C, for example, from about 2-10 ^" Pa to about 5-10 ^"1 Pas, and mainly from about 2-10 ^{" 1} Pas up to about 3 - 10 ^"1 pass.

32. The method according to item 23, in which the carrier fluid includes at least one of water, an aqueous solution of polyacrylamide, guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl cellulose, xanthan gum, sodium alginate, suspension of polyacrylonitrile, as well as their derivatives .

33. The method according to item 23, in which the carrier fluid includes at least one of an aqueous solution of polyacrylamide, guar gum, carboxymethyl hydroxypropyl guar gum, carboxymethyl cellulose, xanthan gum, sodium alginate, suspension of polyacrylonitrile, as well as their derivatives, with a crosslinking agent based on boric acid, soluble salts of zirconium (IV) and aluminum (III), or a combination thereof.

34. The method according to item 23, in which the composition for hydraulic fracturing additionally contains functional additives, including antifoam agents, emulsifiers, high temperature stabilizing agents, corrosion inhibitors, or combinations thereof.

35. The method according to item 23, in which the proppant has a particle size of about 0.1-2 mm, a density of from about 2.4 to about 3.8 g / cm ³ , while the proppant includes at least one of the ceramics , sand, bauxite, glass, walnut shell, polymer proppant, or a mixture thereof.

36. A method for producing polymer fibers for use in a fracturing composition, comprising:

coating the polymer fiber with a sizing agent by means of a coating agent, the sizing agent comprising a base oil, a lubricant based on said oil, having a viscosity index of at least 120 as determined according to ASTM D2270, or mixtures thereof,

drying the fiber coated with a sizing agent.

37. The method according to clause 36, in which the mass fraction of the coating of the sizing agent is from about 0.5 to at least about 50% of the mass, calculated on the total weight of the fibers, mainly from about 1 to about 30% of the mass, calculated on the total weight of the fibers.

38. The method of claim 36, wherein the sizing agent is applied at a temperature not exceeding the glass transition temperature of the fiber material, and the coated fibers of the sizing agent are dried at a temperature of at least 20 degrees Celsius below the melting temperature of the fiber material.

39. The method according to any one of claims 36 to 38, further comprising removing the excess applied sizing agent by squeezing the fibers.

40. The method of claim 36, wherein the fibers include at least one of polyesters, polyamides, polyolefins, cellulosic fiber, viscose fiber, acetate fiber, or combinations thereof.

41. The method of claim 36 or claim 40, wherein the fibers are selected from degrading fibers or non-degrading fibers, or mixtures thereof, the fibers having a direct and / or indirect shape.

42. The method according to p. 36 or 40, in which the fibers have a diameter in the range from about 3 microns to about 40 microns, mainly from about 3 microns to about 7 microns, a length in the range from about 3 mm to about 12 mm, mainly from about 3 mm to about 6 mm, wherein the fiber is at least one of unicomponent fibers, bicomponent fibers or multicomponent fibers.

43. A polymer fiber for use in a hydraulic fracturing composition obtained by the method according to any one of claims 36 to 42, wherein the fibers are coated with a sizing agent including a base oil, a lubricant based on said oil having a viscosity index of at least at least 120 when determined according to ASTM D2270, or mixtures thereof.