WO2017007362A1

WO2017007362A1 - Composite additive for hydraulic fracturing of a formation with reagents for inhibiting sediments (variants)

Info

Publication number: WO2017007362A1
Application number: PCT/RU2015/000423
Authority: WO
Inventors: Анатолий Владимирович МЕДВЕДЕВ; Светлана Анатольевна НАЙДУКОВА; Максим Григорьевич ИВАНОВ; Алексей Владимирович АЛЕКСЕЕВ
Original assignee: Шлюмберже Текнолоджи Корпорейшн; Шлюмберже Канада Лимитед; Сервисес Петролиерс Шлюмберже; Шлюмберже, Текнолоджи Б.В.
Priority date: 2015-07-07
Filing date: 2015-07-07
Publication date: 2017-01-12

Abstract

The invention relates to providing for the stimulation of an oil-bearing formation by means of hydraulic fracturing of the formation. The invention describes a composite additive, which is injected, along with a proppant, into a hydraulic fracturing crack. The additive contains a reagent which inhibits the sedimentation of organic or inorganic sediments from an extracted formation fluid. As a result of the delivery of the composite additive, based on a matrix, to a borehole, said matrix decomposing in borehole conditions and containing a sediment inhibitor, an adjustable and sustained release of the inhibitor into the extracted fluid takes place, and furthermore, a gradual recovery of the conductivity of the proppant packing takes place.

Description

COMPOSITE ADDITIVE FOR HYDROGRAPHIC RESISTANCE WITH REAGENTS FOR INHIBITING SEDIMENTS (OPTIONS)

Technical field

The present invention relates to the field of oil production. More specifically, the invention relates to additives that inhibit deposition in a proppant pack.

Prior art

Hydraulic fracturing (Fracturing) is based on the formation of cracks in the zone of the wellbore to increase the permeability of the formation and increase oil production. To prevent crack closure, a proppant (proppant) is added to the fracturing fluid. The proppant is fed into the crack along with the fluid and remains there, mechanically preventing the crack from closing after the pressure drop. Accordingly, in order to fulfill its function, the proppant must have a certain set of properties. In particular, to increase oil production, it is necessary that the proppant package has sufficient permeability.

A proppant pack penetrates the formation, and its hydraulic permeability is significantly higher than the permeability of the formation. However, the permeability of the actual packing of the proppant formed inside the formation is usually significantly lower than the permeability of the pure proppant. There are a number of reasons for the reduced permeability of the proppant packaging, such as:

immersion of the proppant in the walls of the crack;

the remainder of the polymer fracturing fluid partially clogs the pores and forms a filter cake on the walls of the crack;

insufficient penetration of the proppant into the formation, namely, the small length of the wedged area.

These problems are usually considered and solved when designing a hydraulic fracture.

Another reason for the decrease in permeability is associated with the formation of crack inorganic and organic deposits. Inorganic deposits form in cracks and perforations during the extraction of formation water with high salinity; organic deposits form in cracks and perforations during the extraction of oil with a high content of heavy fractions, such as paraffins and (or) asphaltenes.

The problems associated with the formation of deposits can be solved by conducting downhole operations, when the deterioration of production parameters becomes noticeable. In the presence of undesirable inorganic and organic deposits, it is also possible to use inorganic scale inhibitors and paraffin / asphaltene inhibitors, which are injected into the formation during its hydraulic fracturing. However, the duration of such treatment is short-lived, since the injected chemicals are easily washed out of the formation and from the proppant pack during production. Therefore, the effectiveness of such processing is rather low.

To ensure that measures against these deposits are highly effective, it is important to add chemicals (these sediment inhibitors) to the liquid at a low concentration (slightly above the MCI - minimum inhibitor concentration) over a long period of time.

Therefore, it would be desirable to provide such an inhibitory deposition of the additive, which leads to a delayed and controlled release of the active substance and in low concentrations.

The issue of inhibition of organic and inorganic deposits is disclosed in a number of works, patents and patent applications. Some examples of the chemical composition and physical properties of conventional organic scale inhibitors can be found in patents RU2480505, RU2242503 (depressant additive), RU2208042, RU2326153.

One of the problems of using inhibitors is the rapid reagent consumption in the early stages of reservoir operation. Periodic operations associated with the introduction of additional reagent are expensive and time consuming. SPE 168615 (Baker Hughes) describes the characteristics and application of a new nanotechnology-based substrate with a large surface area for chemical adsorption, which is used to inhibit the formation of barium sulfate deposits. This product is the latest version of the product declared by Szymczak in 2006, used as an additive to a proppant, has a higher strength than a proppant of medium strength, and a large surface area for chemical adsorption. The disadvantages of this product include insufficient functioning time.

In the international application N ° WO2012148819, a product is presented consisting of a calcined porous substrate of nanoscale - calcined porous metal oxide and a processing reagent (sediment and paraffin inhibitors are listed) absorbed into the pore spaces of the porous substrate. It is worth noting that the chemical agent introduced into the pores of the substrate is quickly washed out of the pores. On the other hand, using a porous ceramic matrix it is indeed possible to achieve a slow release of the agent, however, introducing this agent into the porous matrix is difficult.

Moreover, after washing out the active agent, a porous ceramic matrix remains, which clogs the space in the proppant package and leads to a decrease in its permeability.

US8393395 discloses an aqueous suspension of particles comprising well treatment reagents that are encapsulated in a matrix made of a carrier material insoluble in water. The encapsulating matrix is selected so as to provide a delayed release of the reagent placed in the matrix from the particles into the surrounding fluid after placing the suspended particles in the fracture. The encapsulating matrix is made of a polymer, at least partially amorphous, and having a glass transition temperature below the temperature of the treated formation. However, restrictions on the method of producing particles (emulsion polymerization) and small particle sizes (200 microns) reduce the effectiveness of the method of delivery of the reagent. Moreover, the presence of carrier material insoluble in water and in the well fluid leads to clogging of the proppant agent packaging space, which leads to a decrease in its permeability.

A key aspect of this solution is the delayed release of chemicals in the wellbore so that their presence provides longer-term protection against organic and inorganic deposits. The present solution is aimed at delayed release of chemical reagents from solid polymer particles into the produced oil-containing liquid.

The closest analogue of this solution is the patent US 4670166 (Exxon Chemical Services, 1987). It describes particles (balls) based on a solid polymer matrix, which includes a water-soluble chemical reagent (salt inhibitor, corrosion inhibitor, biocides, blowing agents, etc.) to change the chemical properties of the well fluid. The polymer matrix of particles contains 5-30% of a useful reagent. Under borehole conditions, polymer solid water-insoluble particles retain their integrity, and the reagent enters the surrounding fluid due to the permeability and internal porosity of the polymer matrix (1 pf). The flow of well fluid flushes the powdered reagent from polymer balls pumped together with proppant into the rock. Since the softening temperature of the polymer (Tg) is higher than the temperature of the well conditions, this helps to maintain the stability of the particle geometry.

Obviously, when the reagent is released by the mechanism of permeability of water into the permeable matrix, the strength of the composite particle decreases (the reagent powder acts as a filler for the liquid matrix to break the polymer matrix), and this will cause deformation of the balls and long-term blockage of the pore space of the proppant pack with injected polymer ones ( soft) balls, which leads to a decrease in the permeability of the pack of proppant.

To restore the conductivity of this package, it would be desirable to completely get rid of the polymer matrix after completion of the beneficial effects of chemicals on the fluid inside the hydraulic fracture.

In contrast to the prototype, in which after the release of the reagent from polymer matrix due to diffusion into the volume of the crack, the specified liquid insoluble matrix remains in the volume of the crack, according to the present solution, the polymer matrix containing the reagent is destroyed (as a result of dissolution).

Short description

The deposition of organic and inorganic compounds in tubing, perforations or formations during hydrocarbon production is still a serious problem affecting the economic efficiency of well operation. Existing methods of solving the problem, such as the introduction of inhibitors of all kinds, are considered to be no more than satisfactory, since they give only a short-term effect. An ideal solution would be the injection of inhibitors at the stage of hydraulic fracturing operation (Fracturing) and the slow subsequent release of inhibitors to the target zone.

The specified delayed release is ensured by the use of well-decomposable polymers (such as polylactic acid, polybutylene succinate, polyglycolic acid, polyethylene terephthalate, polyvinyl alcohol, nylon and others, as well as their copolymers, mixtures and modifications) containing inhibitor particles. The gradual decomposition of the polymer in the borehole conditions is designed to maintain a constant concentration of inhibitors in the return fluid.

Further in the text the concepts “inorganic scale inhibitor”, “scale inhibitor” and “mineral salt scale inhibitor” are used as equivalent concepts.

Essence

Thus, the technical task was to create an additive that inhibits deposits, which provides work for long-term goals, namely, the release time of inhibitors of organic or inorganic deposits will be months or more, which ensures a gradual restoration of the initial conductivity of the proppant package.

The problem is solved by choosing a specific polymer matrices with the desired degradation time, which controls the length of time the release of the reagent from the matrix. The sizes of particles (granules) provide for the joint transportation of proppant and polymer additive into the depth of the hydraulic fracture, as a result of which the suspension does not separate into the additive and proppant.

As a result of using the composite additive according to the present solution, there is a gradual (delayed, long-term) and controlled release of a chemical reagent (active substance) for treating a hydraulic fracture from a polymer matrix. For long-term purposes, composite materials can be used at temperatures below the glass transition temperature. At the same time, the release time of the active component will be months or more.

As a result of the simultaneous and controlled retention of the active substance in the matrix, the integrity (stability, consolidation) of the proppant pack is achieved (particles remain in it, and do not clog the pores of the fracture space).

After degradation of the polymer matrix under borehole conditions, the proppant pack conductivity is restored (disintegration and leaching of the polymer matrix and reagent leaves free pore space). Slow release of the chemical reagent from the polymer matrix of the granules prevents the formation of inorganic or organic deposits in the fracture and in the well for a long time, while the degradation of the polymer matrix during the release of the chemical agent restores the hydraulic conductivity of the crack (approaching the initial hydraulic conductivity of the crack without use of additives).

As a result of the selection of a polymer matrix with the desired degradation time for a known formation / fracture temperature, as well as through the use of a granular form of an additive of a certain size, integrity (stability, consolidation) of the proppant package is achieved.

Thus, the proposed method of processing the formation, including the introduction into the well of a composite additive for inhibiting inorganic deposits or a composite additive for inhibiting organic deposits. The formation of deposits is prevented at the places of formation fluid inflow.

Detailed description

As mentioned above, inhibitors, which include the following chemical agents: inhibiting agents such as paraffin and asphaltene modifiers, crystal growth modifiers and dispersants, sediment cleansers, inorganic scale inhibitors of polymer and inorganic nature, they are added to the polymer material before or in the process of melting the polymer. The specified polymer should be made from a decomposable polymer under formation conditions (such as polylactic acid, polybutylene succinate, polyglycolic acid, polyethylene terephthalate, polyvinyl alcohol, nylon and others, as well as their copolymers, mixtures, modifications and combinations). To ensure the distribution of inhibitors within the polymer matrix, they are thoroughly mixed.

From this material containing a polymer and inhibitors embedded in its structure, solid granules of the required shape (rods, tapes, etc.) and with the required characteristic ratio are produced.

These particles are added to the fracturing fluid in the form of dry additives at the proppant stage together with the proppant. In this case, particles containing inhibitors are evenly distributed among the proppant particles or, in some cases, are intentionally concentrated in the near-wellbore zone. As an alternative, it is possible to pump these particles at the stage of phase injection without a proppant, and it is also possible to use a proppant with heterogeneous placement.

After the crack is closed, the particles containing the inhibitors are distributed between the proppant particles, which prevents their washing out by the reverse flow at the first stage of production.

At a certain time and under certain temperature conditions after the crack closes, the polymer begins to decompose slowly at the calculated rate, and a chemical reagent (this inhibitor) is released from media, providing a reduction in the formation of inorganic and organic deposits.

The decomposition rates of the polymers available on the market at different temperatures are well known, therefore, at a known temperature of the treated formation, it is possible to isolate the inhibitor continuously or selectively at a specific time.

The use of large particles (additive granules) up to 2-4 mm in diameter allows avoiding delamination of the suspension when injecting the hydraulic fracturing and leaching the granules from the pack of proppant at the oil production stage.

Obtaining a polymer-reagent composite by polymer extrusion allows to obtain a higher concentration of the active component in the polymer matrix. In the examples with polymer granules, the concentration of the active component of 20 and more weight percent was easily achieved, while providing a high proportion of the load of the active component (scale inhibitor) in the polymer matrix.

Thus, extrusion is a more advanced method of manufacturing composite materials as leading to a high content of the active component, which is more advisable from an economic point of view.

Description of drawings

Figure 1 shows a first embodiment of a composite proppant additive.

Figure 2 shows a second embodiment of a polymer modified proppant additive.

Fig. 3 shows an example of granules of the first embodiment.

Figure 4 shows the degree of release of the salt deposition inhibitor from the polymer matrix depending on the duration of degradation at T = 70 ° C (three types of polymers).

5 shows an example of granules of a first embodiment based on epoxy resin.

Figa shows the dependence of the degree of release of the inhibitor of deposits from the granules when they are kept in water at a temperature of 95 ° C (examples 2015/000423

a polymer matrix carrier with a high degree of crosslinking and a polymer matrix carrier with a low degree of crosslinking).

Figb shows the dependence of the degree of release of the inhibitor from the obtained particles when they are kept in water at a temperature of 70 ° C.

Fig.7 shows the dependence of the degree of release of the inhibitor from the obtained granules of the additive when they vyderzhivaniya in an aqueous medium at a temperature of 40 ° C.

Fig. 8 is a micrograph of a slice of a polylactic acid (PMA) composite particle of Example 3 coated with a cured epoxy resin layer.

Fig.9 shows the degree of release of the chemical agent from the polymer matrix for the particles of example 3, uncoated and coated with a layer of epoxy resin.

Figure 10 is a comparison of the hydraulic permeability of proppant packs: a pack without a composite additive, a pack with an additive in the form of PLA granules (PMA) (additive 1% of proppant volume) mixed with conventional proppant, and also proppant pack after complete degradation of the PLA granules.

Detailed description

The following shows in more detail embodiments of the disclosure in detail, which should not be construed as limitations.

Options for implementation (in terms of the structure of the composite additive)

First Embodiment

In a first embodiment, the present solution comprises powdered inhibitor particles uniformly distributed within a matrix of a degradable polymer. Alternatively, if applicable (there is a liquid inhibitor and the ability to mix the solution with the polymer), a solution of the scale inhibitor can be mixed evenly with the polymer (see FIG. 1).

Particles obtained from the specified composite mixture of polymer and inhibitors may have different shapes and proportions (rods, flakes, granules, ribbons, etc.). The shape of the particles affects the rate of surface degradation of the polymer, and hence the rate of release of the inhibitor reagent. Thus, the surface degradation rate of a polymer is higher, the higher the specific surface area of the particles. Therefore, a delayed release of reagent compared to other types of particles will provide granules. Thus, the selection of the forms of the granules (elongated shape, cylinders, plates, etc.) provides little flexibility in ensuring the speed of exit of the reagent.

If we proceed from the influence on the achievement of another technical result, namely, on maintaining the integrity of the proppant packaging, then the form of the additive is of secondary importance compared to the size of the granules. Larger-sized additive granules due to a larger hydrodynamic radius provide a pellet deposition rate in the working fluid similar to proppant particles. This avoids the separation of the suspension by the type of particles (proppant and additive granules). The additive will be placed evenly throughout the proppant pack.

Second Embodiment

The second embodiment is shown in FIG. 2 and is an extension of the first embodiment. In particular, particles of the first embodiment (degradable polymer particles with an inhibitor embedded in the polymer matrix are coated with a second polymer with a reduced rate of degradation under the same conditions). In this case, the release of the inhibitor from the matrix of the first polymer does not begin until decomposition of the second (external) polymer occurs. Thus, the second embodiment provides an additional mechanism for delaying the release of inhibitors.

In this case, the solid degradable polymer matrix in the additive particles remains neutral with respect to the chemical reagent at the softening temperature of the polymer of the solid polymer matrix or at the polymerization temperature. In other words, the polymer matrix is only a temporary carrier of the reagent (an inhibitor of the deposition of inorganic or organic deposits). 0423

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EXAMPLE 1

The incorporation of dry powder into the polymer matrix. The polymers PBS (polybutylene succinate), PLA (polylactic acid), and PHB (polyhydroxybutyrate) were selected from the group of thermoplastic polymers that slowly degrade in the aqueous medium at elevated temperatures. Anhydrous copper sulfate (P) with a particle size of 5-10 μm was chosen as solids as an indicator of the dissolution (degradation) of the polymer matrix, as well as the active component of the additive — an inorganic scale inhibitor (diethylene triamine pentamethylene phosphonic acid or DTPMP — scale inhibitor and corrosion inhibitor) .

A composite polymer (granular) additive was obtained by melting a polymer (e.g., PBS, PLA, or PHB) at a temperature slightly above the melting point of the selected polymer. Then, a portion of anhydrous copper sulfate (I) was added to the melt (matrix) with an inorganic scale inhibitor DTPMP with simultaneous stirring. The mass ratio of anhydrous copper sulfate and inhibitor was 1: 3, while the function of anhydrous copper sulfate was only to provide a spectrophotometric method for measuring its concentration as an indicator of the release of a powder additive in an aqueous solution. The weight concentration of the scale inhibitor in the polymer matrix was 15%.

Then this polymer melt with dry additives (inhibitor powder and indicator powder) was poured onto a Teflon substrate, cooled and cut into pieces 0.5-2.5 mm in size (Fig. 3).

The obtained additive particles were placed in vessels with deionized water (in a mass ratio of 3: 100) and thermostated at 70 ° C (typical temperature in a number of wells).

The concentration of copper cations (an indicator of the reagent yield from the polymer matrix into the solution) was recorded on a spectrophotometer. The dependences of the concentration of the inhibitor in water (recalculated based on the mass ratio of anhydrous copper sulfate and inhibitor 1: 3), as well as the degree of release of the inhibitor from the polymer matrix over time, are shown in 3

12 figure 4. It turned out that the total yield of the chemical reagent from the polymer matrix depends on the nature of the selected polymer (polymer matrix). So, for PLA polymer, a full yield is achieved in 10 days, while for a polymer matrix of PBS and PHB (delayed polymer degradation) - in 30 days.

The use of any other polymer from the group of thermoplastic polymers (for example, acrylonitrile butadiene styrene (ABS plastic), acrylic, polyamide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polybenzimidazole, etc.) allows you to choose the appropriate polymer degradation time in the well fluid (water and oil in various proportions) and the rate of release of the chemical agent. Also, the use of another inhibitor, including an inhibitor of organic deposits, will lead to the same technical results, since the yield of a chemical agent in a liquid is determined by the degradation rate of the host polymer matrix.

This example demonstrates that the reagent incorporated into the polymer gradually enters the aqueous solution as the polymer degrades. Slowed release of the reagent from the polymer matrix will provide long-term inhibition of inorganic salts (or organic deposits), depending on the type of inhibitor selected. In this case, composite granules can be created on the basis of a polymer melt or using industrial polymer extruders.

EXAMPLE 2

Another example of the introduction of a dry powdery substance into a polymer matrix. An epoxy resin was chosen as the polymer matrix. Ethylene diamine was chosen as the hardener of the epoxy polymer matrix. It is known that cured epoxy resin has high thermal stability compared to thermoplastics. Accordingly, in this case, you can count on the high duration of the release of the active agent from this polymer. This example demonstrates that the concentration of the hardener during curing of the resin affects the rate of release of the chemical reagent from the cured granules.

Resin, hardener, anhydrous copper sulfate (P) with a particle size of 5-10 T RU2015 / 000423

13 microns, as well as an inhibitor of organic deposits (polyethylene in finely divided form) were kneaded by heating in a water bath (to reduce the viscosity of the resin and facilitate mixing of the components). Then, the still not hardened viscous composite was poured into a cylindrical form with a cylinder diameter of 10 mm. The polymerized resin was allowed to solidify within 1-2 days. The mass ratio of anhydrous copper sulfate and inhibitor was 1: 3, while the function of anhydrous copper sulfate was only to provide a spectrophotometric method for its detection (and hence the indicated inhibitor) in an aqueous solution. The final concentration of inhibitor in the resin was 16.5 weight percent. Hardener was added to the resin both in deficiency (5 weight percent) and in excess (10 weight percent) - this affects the strength of the granules of the composite additive and the rate of degradation of the granules in the oily liquid.

The resulting rods were removed from the molds and cut into pieces so that the final product had the form of cylinders with a height of 0.5-10 mm and a diameter of 1.0 mm (granules).

The obtained additive granules were placed in vessels with water, which in turn were thermostated at 70 ° C or at 95 ° C.

The concentration of copper cations (the result of the release of copper sulfate from the granules) was recorded on a spectrophotometer. The time dependences of the inhibitor concentration in water, calculated on the basis of the mass ratio of anhydrous copper sulfate and inhibitor 1: 3, for different temperatures, both cases for a hardener deficiency and for an excess of hardener, are shown in Fig. B and 66.

From figa and 66 it can be concluded that the concentration of the hardener resin also affects the rate of exit of the chemical reagent from the polymer matrix, and increasing the concentration of the hardener leads to a decrease in the rate of exit.

In addition, we can conclude that the rate of release of the reagent from the polymer matrix is determined by the temperature of the medium. After linear approximations in Fig. B and 66, it was determined the number of days for the complete release of the chemical reagent from the polymer matrix depending on temperature 15 000423

14 water. In particular, for a liquid temperature of 95 ° C, a complete yield of the reagent is achieved within 80 days with a lack of resin hardener, and about 200 days with its excess. For a temperature of 70 ° C, the full yield of the reagent is achieved within about 200 days with a hardener deficiency, and more than 1000 days with an excess of it.

A fundamentally similar technical result of the delayed release of a chemical agent will be achieved using an inorganic scale inhibitor (salt formation inhibitor) in the form of a powder.

This example demonstrates that the epoxy resin releases a chemical agent that is mixed in it, and the release rate of this reagent is determined by the concentration of the hardener in the resin and the temperature. The slow release of the reagent from the polymer matrix will provide long-term prevention of the formation of inorganic or organic deposits, depending on the nature of the selected reagent.

EXAMPLE 3. Production of additive granules from a thermoplastic polymer by extrusion

Granules PLA (thermoplastic polymer) with additives were obtained by extrusion on a single screw extruder. Dried PLA granules in an amount of 80 g were mixed with 5 g of dye E1 10 "Sunset" and 15 g of an inorganic scale inhibitor (salts of ethylenediamine tetraacetic acid - EDTA) by dry mechanical stirring. In this case, the dye and inhibitor were thoroughly mixed with polymer granules. Granules with powder were poured into the hopper of the extruder. The mixing zone was heated to 160 ° C, and then the polymer was extruded with additives through a die with a hole diameter of 2 mm. The result was granules with a size of about 2 mm and containing 5% by weight of the dye E1 10 "Sunset" and 15% by weight of an inorganic scale inhibitor (EDTA).

The granules were placed in water heated to a temperature of 40 ° C. In this case, the concentration of the dye released from the polymer at various points in time was measured (see Fig. 7). According to the mass ratio of inhibitor and dye, 3: 1, the amount of inhibitor released together with the indicator from the polymer matrix was determined. PT / RU2015 / 000423

fifteen

This example demonstrates that a chemical reagent embedded in a degradable polymer matrix from polylactic acid leaves it for approximately 10 months at a temperature of 40 ° C, while the material of the polymer matrix itself degrades over time and turns into low molecular weight products that are soluble in the formation fluid .

The use of any other polymer from the group of thermoplastic polymers (for example, acrylonitrile butadiene styrene, acrylic, polyamide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polybenzimidazole, etc.) allows you to choose the appropriate polymer degradation time and the rate of release of the chemical agent.

EXAMPLE 4. The manufacture of additive granules according to the second variant implementation

An example is the possibility of implementing the second embodiment of the solution. In this case, the granules of Example 3 were taken and coated with a layer of epoxy resin with a thickness of 30-40 μm (see Fig. 8). Then, after drying the resin, the particles were placed in vessels with water, which, in turn, were thermostated at 95 ° C. A temperature of 95 ° C was chosen to accelerate the output of degradation of the granules, so that in laboratory conditions for a short time to get a tangible result. Figure 9 shows a comparison of the yield of a chemical agent from the particles of Example 3 (granule without a temporary coating) and from particles coated with an epoxy resin layer. It can be concluded that this coating allowed us to reduce the yield of the chemical agent by about half. The selection of the brand of epoxy resin, as well as the degree of crosslinking by the hardener, will optimize the rate of release of the chemical agent in accordance with the necessary requirements.

As the coating of the granules, it is also possible to use a polymer that degrades for a longer time than the polymer matrix. In particular, they can be more heat-resistant thermoplastic polymers (for example, acrylonitrile butadiene styrene, acrylic, polyamide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polybenzimidazole, etc.) or thermosetting polymers (for example, based on phenol-formaldehyde, polyester, epoxy and carbides pitches). 00423

16

EXAMPLE 5. Selection of the boundaries of the concentration of the active component

This example defines the boundaries of the concentration of the active component in the polymer matrix. A typical concentration of a dry additive in a fracturing fluid is about 2 percent of the mass of the fracturing fluid injected into the formation. Standard fracturing work involves the injection of about 2,000 barrels of fluid (320 thousand liters), which allows about 6 thousand kg of dry additive to be pumped into the fracture (M).

The amount of inhibitor required to process the formation for at least one year (t) was determined. Accepted average flow of produced water from the well (Q) at the level of 500 barrels per day. Typically, the minimum inhibitor concentration (MIC) necessary to effectively prevent the formation of both inorganic and organic deposits varies from 0.5 to 120 ppm. Thus, to prevent the formation of solid deposits during the year, all you need is a scale inhibitor in the amount of m = MICxQxt = l 5-3000 kg.

Thus, it is possible to determine the intervals of the mass concentration of the inhibitor placed in the polymer matrix of granules: c = t / M = 0.25-60%.

In addition, the upper limit of the concentration of inhibitor in the polymer matrix can be determined by the fact that the granules prepared according to example 1 and example 3 lose their mechanical strength at a mass concentration of the additive above 60%.

This example demonstrates that the concentration of inhibitor in the polymer matrix is in the range from 0.25 to 60 weight percent.

EXAMPLE 6. Selection of recommended concentration limits of the active component

According to example 5, the concentration of inhibitor in the polymer matrix is in the range from 0.25 to 60 weight percent. Moreover, for most underground formations, to prevent the deposition of both inorganic and organic deposits, MIC varies in the range from 0.5 to 40 ppm. Thus, the desired intervals of the mass concentration of the inhibitor in the polymer matrix with = 0.25-20%.

EXAMPLE 7. Degradation of a polymer matrix and an increase in conductivity 00423

17 proppant packs after the release of the chemical agent from the polymer matrix

This example compares the hydraulic conductivity of proppant packs without additives, as well as the mixing of polymer particles. Conductivity experiments were performed in accordance with API 19D. The test samples were pure proppant CarboHSP 20/40, as well as proppant CarboHSP 20/40 with the addition of granules PLA with a concentration of 1% by weight of proppant. Samples were loaded into a conduction cell, providing a surface concentration of 2 psi. foot. The resulting proppant packs were pressurized at 5,000 psi. inch (psi), and then the conduction cell was heated to 121 ° C. Figure 10 presents the obtained results of hydraulic conductivity for pure proppant (without additives / additives), for proppant pack with additive / additive particles (1% PLA particles), as well as for proppant pack after degradation of polymer particles. The results indicate that after polymer degradation, the conductivity is close to the conductivity of a clean proppant pack.

Thus, this example demonstrates that after the release of the chemical agent and subsequent degradation of the disclosed polymer particles, the hydraulic permeability of the proppant pack remains close to the conductivity of a clean proppant pack.

Obviously, the embodiments described above should not be construed as limiting the scope of patent claims of the invention. For any person skilled in the art it is clear that there is the opportunity to make many changes to the above options and, without departing from the principles of the invention claimed in the claims.

Claims

18 FORMULATION OF THE INVENTION

1. A composite additive for treating a formation in the form of granules containing a solid polymer matrix and a chemical reagent to prevent or reduce the deposition of inorganic deposits, while the solid polymer matrix degrades under borehole conditions, releasing the specified chemical reagent.

2. The additive according to claim 1, in which the content of the chemical reagent is by weight of the additive from about 0.25 wt.% To about 60.0 wt.%, Mainly from about 0.25 wt.% To about 20.0 wt. %

3. The additive according to claim 1, in which the size of the composite additive is selected from

0.2 mm to 4.0 mm, in most cases from 0.5 mm to 1.0 mm.

4. The additive according to claim 1, in which the solid polymer matrix contains a water-degradable polymer or a water-soluble polymer.

5. The additive according to claim 1, in which the solid polymer matrix contains a polymer selected from the group consisting of polybutylene succinate, polylactic acid, polyhydroxybutyrate, acrylonitrile butadiene styrene, acrylic, polyamide, polystyrene, polybenzimidazole and mixtures thereof.

6. The additive according to claim 1, in which the solid polymer matrix contains a polymer selected from the group of thermosetting polymers, in particular, based on phenol-formaldehyde, polyester, epoxy and urea resins.

7. The additive according to claim 1 or 6, in which the solid polymer matrix remains neutral with respect to the chemical reagent at the softening temperature of the polymer of the solid polymer matrix or at the polymerization temperature.

8. The additive according to claims 1 and 7, in which the chemical reagent for preventing or reducing inorganic deposits is selected from the group of chelating agents, including potassium, sodium, ammonium salts of ethylenediamine tetraacetic, citric or tartaric acid; or from organic phosphorus-containing compounds, for example OMTNR, DETPMP, NMTRMP, HMDP, EDTMPA, NTP, HEDP, EAVMRA, EAVMRA, NRAA; or from polymers and copolymers of aspartic, acrylic, methacrylic acids, their derivatives and combinations.

9. The additive according to claim 1, in which the chemical reagent is selected in dispersed form, for example, in the form of a powder or paste.

10. The additive according to claim 1, which further has a coating, which is a film-forming polymer having a lower degradation rate than the polymer matrix.

1 1. The additive according to claim P, wherein the film-forming polymer is selected from the group consisting of degradable polymers, such as polyesters, for example polylactic acid, as well as polyvinyl alcohol, nylon, polyethylene terephthalate, combinations thereof or derivatives.

12. The additive according to claim 1, characterized in that it is obtained by extrusion.

13. A composite additive for treating the formation in the form of granules containing a solid polymer matrix and a chemical reagent to prevent or reduce organic deposits, while the solid polymer matrix degrades in the borehole conditions, releasing the specified chemical reagent.

14. The additive according to item 13, in which the content of the chemical reagent is by weight of the additive from about 0.25 wt.% To about 60.0 wt.%, Mainly from about 0.25 wt.% To about 20.0 wt. %

15. The additive according to item 13, in which the size of the composite additive is selected from about 0.2 mm to about 4.0 mm, in most cases from about 0.5 mm to about 1.0 mm.

16. The additive according to item 13, in which the solid polymer matrix contains a degradable in oil or oil soluble polymer.

17. The additive according to item 13, in which the solid polymer matrix contains a polymer selected from the group comprising polyhydroxyl butyrate, acrylonitrile butadiene styrene, acrylic, polyamide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polybenzimidazole and mixtures thereof.

18. The additive according to item 13, in which the solid polymer matrix contains a polymer selected from the group of thermosetting polymers, for example, based on phenol-formaldehyde, polyester, epoxy and urea resins.

19. The additive according to item 13 or 18, in which the solid polymer matrix remains essentially neutral with respect to the chemical reagent when the softening temperature of the polymer of the solid polymer matrix or at the polymerization temperature.

20. The additive according to item 13, in which the chemical reagent for preventing or reducing organic deposits is an inhibitor of the formation of solid paraffins and / or asphaltenes.

21. The additive according to item 13 or 20, in which the chemical agent for preventing or reducing organic deposits is selected from the group consisting of olefin / maleic esters, olefin / maleic amides, ethylene vinyl acetate, modified ethylene vinyl acetates, alkyl phenolic resins, alkyl acrylates, alkyl phenol-formaldehyde resins, amines alkylphenol formaldehyde resins, polyalkyl anhydrides, maleic anhydride of alpha-olefin polyesters, esters of polyacrylates, their derivatives and combinations.

22. The additive according to item 13, in which the chemical reagent is selected in the form of a powder or paste.

23. The additive according to item 13, which further has a coating representing a film-forming polymer and having a lower degradation rate than a solid polymer matrix.

24. The additive according to item 23, in which the film-forming polymer is selected from the group comprising degrading polymers, such as polyesters, for example polylactic acid, as well as polyvinyl alcohol, nylon, polyethylene terephthalate, combinations thereof or derivatives.

25. The additive according to item 13, obtained by extrusion.

26. A method of treating a formation, comprising introducing into the well a composite additive for inhibiting inorganic deposits according to claims 1-

12 or a composite additive for inhibiting organic deposits according to claims 13-25.