RU2507389C1 - Method of formation hydraulic fracturing - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method includes filling formation with mixture of fracturing liquid with proppant agent. As proppant agent gas crystallohydrates are used. Filling is performed under thermobaric conditions of existence of gas crystallohydrates. After formation fracture gas crystallohydrates are decomposed with extraction of gaseous phase additional to splitting macro and micro-cracks of formation fracture. Filling of fracturing liquid mixture with proppant agent, formation fracture and crystallohydrates decomposition are performed one or several times.

EFFECT: improving formation permeability during hydraulic fracturing.

4 cl, 5 dwg

Description

The invention relates to the field of hydrocarbon production and can be used to intensify the flow of fluid to the well due to the formation of cracks in the reservoir.

A known method of hydraulic fracturing, including injecting fluid into the reservoir and fracturing by increasing the bottomhole pressure to create a predetermined size crack, lowering the bottomhole pressure below the fracture pressure, injecting the slurry with fixing material and injecting the displacement fluid at a rate that ensures the bottomhole pressure rises above the fracture pressure formation, and the fracturing fluid is pumped in a volume that ensures the creation of a crack with a length exceeding the radius of the borehole zone of the formation of reduced permeability and, use a suspension with a fixing material in the form of a gel and pump it in a volume greater than the volume of the created crack (Patent RU No. 2164290, ЕВВ 43/26, publ. March 20, 2001).

A common feature of the known and proposed methods is the injection of fluid into the formation and its fracture.

The main disadvantage of this method is the use of a suspension with a fixing material in the form of a gel and pumping it in a volume larger than the volume of the created crack. The gel fills the fracture cracks and thereby leads to a decrease in fluid inflow from the formation (flow rate), i.e. to reduce the efficiency of the hydrocarbon production process.

The closest in technical essence and the achieved result to the proposed one is a method of hydraulic fracturing, which includes injecting a mixture of fracturing fluid with a proppant into the reservoir, gas-filled granules being used as proppant, the density of which is close to the density of the fracturing fluid and makes it possible to hold the proppant in suspended state in the fracturing fluid, while the fluid used is the one that is compatible with the formation rock and fluid, For example water or oil (Patent RU №2096603, E 21 B 43/26, publ. 20.11.1997).

A common feature of the known and proposed method is the injection into the reservoir of a mixture of fracturing fluid with a proppant.

The main disadvantage of this method is the use of gas-filled granules as a proppant, after the destruction of which and gas evolution from them, aluminosilicate particles and polymer films remain, clogging the pores of the formation and reducing its permeability for the passage of the produced fluid. Those. this leads to a decrease in the efficiency of the hydrocarbon production process.

The problem solved by the invention is to increase the efficiency of the hydrocarbon production process. The technical result is to increase the permeability of the formation during hydraulic fracturing.

The technical result is achieved by the fact that gas crystalline hydrates are used as a proppant, the injection is carried out under thermobaric conditions for the existence of the latter, gas fractures are decomposed after the formation ruptures, and a gas phase is separated from them, additionally wedging macro- and microcracks in the formation rupture, and the mixture of fracturing fluid is injected with proppant, fracturing and decomposition of crystalline hydrates produced once or repeatedly.

In addition, crystalline hydrates of hydrocarbon and / or non-hydrocarbon gases are used.

In addition, crystalline hydrates are decomposed by adding an antihydrate reagent to the mixture of the fracturing liquid with the proppant and / or changing its thermobaric parameters.

In addition, multiple injection of a mixture of fracturing fluid with a proppant, formation fracturing and decomposition of crystalline hydrates is performed with the formation of thermal or / and pressure waves in the reservoir.

The technique, which consists in using gas crystalline hydrates as the proppant, leads to high filtration of the mixture from the fracturing fluid and crystalline hydrates into the formation. High permeability is due to the fact that the particles of crystalline hydrates have a finely dispersed structure and are easily destroyed in pore channels and capillaries under the action of a forcing pressure. In addition, crystalline hydrates are a combination of water and gas, which after decomposition of crystalline hydrates do not clog the pores of the reservoir.

The technical technique, which consists in the fact that the injection is carried out under thermobaric conditions for the existence of gas crystalline hydrates, leads to the creation of optimal conditions for: filtering the mixture of fracturing fluid and crystalline hydrates into the pores of the formation, the fracturing process, because the mixture of liquid and crystalline hydrates is incompressible and intensely affects the solid rock, destroying the latter. This ultimately increases the permeability of the formation during fracturing.

The technical technique, which consists in the fact that after fracturing, gas crystalline hydrates decompose with the release of a gas phase from them, additionally wedging macro- and microcracks of fracturing, leads to an increase in the permeability of the formation.

The technique, which consists in the fact that the injection of the mixture, fracturing and decomposition of crystalline hydrates is carried out once or repeatedly, makes it possible to control the process of hydraulic fracturing, creating an extensive network of macro- and microcracks in it.

The technique, which involves the use of crystalline hydrates of hydrocarbon or / and non-hydrocarbon gases, makes it possible to wedge macro- and microcracks by the gas phase, choosing the optimal thermobaric effect on the formation solid rock by using individual thermobaric decomposition parameters of crystalline hydrates of individual gases. That is, using crystalline hydrates from individual gases, the necessary temperatures and pressures are selected to wedge macro- and microcracks. Figure 1 shows the equilibrium thermobaric curves of crystalline hydrates from gases: nitrogen (N ₂ ), argon (Ar), methane (CH ₄ ), carbon dioxide (CO ₂ ), ethane (C ₂ H ₆ ) [Istomin VA, Yakushev BC Gas hydrates in nature. - M .: Subsoil. - 1992. - 235 p .; Makogon Yu.F. Gas hydrates, prevention of their formation and use. - M .: Subsoil. - 1985. - 232 p.]. From these graphs it can be seen that at temperatures from 263 K (-10 ° C) to 300 K (17 ° C) the decomposition pressure of crystalline nitrogen gas hydrates (N ₂ ) is from 10.0 to 50.0 MPa or more; argon (Ar) - from 7.0 to 50.0 MPa or more; methane (CH ₄ ) - from 1.8 to 20.0 MPa; carbon dioxide (CO ₂ ) - from 1.9 to 4.5 MPa; ethane (C ₂ H ₆ ) - from 0.3 to 3.5 MPa. Using the crystalline hydrates of these gases, it is possible to select in a fairly wide range the thermobaric conditions for the effect of the gas phase on the formation.

The technical method, which consists in the fact that crystalline hydrates are decomposed by adding an antihydrate reagent to the mixture of the fracturing liquid with a proppant and / or changing its thermobaric parameters, makes it possible to control the decomposition of crystalline hydrates, i.e. to control the thermobaric parameters of the gas phase, wedging macro- and microcracks. The use of only an antihydrate reagent can reduce the energy costs of the decomposition of crystalline hydrates. Figure 2, 3 presents graphs of parameters (pressure and temperature) decomposition of methane crystalline hydrates [Handbook for the transport of combustible gases. - M .: State Scientific and Technical Publishing House of Oil and Mining and Fuel Literature // Ed. K.S. Zarembo. - 1962. - P.193]. Figure 3 graphs of the parameters of the decomposition of methane crystalline hydrates from the action of 10% aqueous solutions of antihydrate reagents: ammonia - 1; methanol - 2; ethyl alcohol and calcium chloride - 3; normal propyl alcohol - 4; acetone - 5. From the graphs in figure 2 it can be seen that, by selecting antihydrate reagents, it is possible to change the parameters of the hydrate decomposition process in a rather wide range: temperature from minus 4 to plus 17 ° C, and pressure from 10 to 70 MPa. Figure 3 presents graphs reflecting the effect of the concentration of methyl alcohol in an aqueous solution on the decomposition parameters of methane crystalline hydrates. From the graphs in figure 3 it follows that by changing the concentration of an aqueous solution of methanol from 0 to 25%, it is possible to change the parameters of the process of decomposition of hydrates: temperature from minus 7 to plus 77 ° C and pressure from 10 to 70 MPa.

The combined use of an antihydrate reagent and changes in the thermobaric parameters of the mixture of the fracturing liquid with the proppant allows one to intensify the decomposition of gas hydrates and increase the rate of release of the gas phase from them, wedging macro- and microcracks. Changing only the thermobaric parameters of the mixture of the fracturing fluid with the proppant can reduce the operating costs associated with the acquisition, delivery, storage, protection, etc. of antihydrate reagents.

The technical technique, which consists in the fact that multiple injection of a mixture of fracturing fluid with a proppant, formation fracturing and decomposition of crystalline hydrates is carried out with the formation of thermal or / and pressure waves in the reservoir, makes it possible to intensify the indicated formation rock destruction and the formation of additional macro- and microcracks in it , i.e. increase its permeability and ultimately increase the efficiency of the hydrocarbon production process.

The authors are not aware of the current level of technology to increase the efficiency of the hydrocarbon production process by increasing the permeability of the formation during hydraulic fracturing in a similar way.

Figures 4 and 5 are diagrams illustrating the technological and technical aspects of the implementation of the hydraulic fracturing method.

Hydraulic fracturing according to the proposed method is as follows.

Hydraulic fracturing (Fig. 4) is carried out by pumping 1 into the formation 2 of a mixture 3 of a fracturing fluid 4 from a reservoir 5 with a proppant 6 supplied from the container 7 and increasing the bottomhole pressure. In this case, gas crystalline hydrates are used as a proppant (see Fig. 1), injection is carried out under thermobaric conditions (temperatures and pressures - see Fig. 1) of the existence of the latter. After fracturing 8 of formation 2, gas crystalline hydrates decompose (FIG. 5), releasing a gas phase 9 from them, additionally wedging macro- and microcracks 10 of fracturing 8 of formation 2. Moreover, (FIGS. 4, 5) injection of a mixture of 3 fracturing fluids 4 with a proppant 6, fracture 8 of formation 2 and decomposition of crystalline hydrates is performed once or repeatedly.

Crystalline hydrates of hydrocarbon [for example, (see FIG. 1) methane (CH ₄ ethane (C ₂ H ₆ )] and / or non-hydrocarbon gases [for example, nitrogen (N ₂ ), carbon dioxide (CO ₂ )] are used.

The crystal hydrates are decomposed by adding an antihydrate reagent to the mixture of the fracturing liquid with the proppant and / or changing its thermobaric parameters.

Crystalline hydrates are decomposed by adding an antihydrate reagent 11 to pump 12 from a container 12 to a mixture of 3 fracture liquids 4 with a proppant agent 6 from a reservoir 13. Crystalline hydrates are decomposed by also changing thermobaric conditions (for example, heating the fracture fluid 4 with a proppant 6 in the bottom-hole zone using a heating cable 14 of the electric generating installation 15 to a temperature higher than the temperature of existence of gas crystalline hydrates). This increases the pressure of the gas phase 9, wedging macro- and microcracks 10.

Multiple injection of the mixture 3 of the fracturing fluid 4 with the proppant 6, fracturing of the reservoir 8 by increasing the bottomhole pressure (Fig. 4) and decomposition of crystalline hydrates (Fig. 5) produce thermal or / and pressure waves in the reservoir. These waves intensify the destruction of formation 2 rock and the formation of additional macro- and microcracks 10 in it, i.e. contribute to increasing its permeability, which, ultimately, increases the efficiency of the hydrocarbon production process.

The implementation of the method is illustrated by examples.

EXAMPLE 1

Hydraulic fracturing (Fig. 4) at the bottom of a well with a depth of 2300 m with a reservoir pressure of 19 MPa is carried out by pumping 1 into the formation 2 a mixture of fracturing fluid 3 (ClearWater) in a volume of 120 m ³ from reservoir 5 with proppant 6 supplied from container 7, and increase bottomhole pressure to 45 MPa. In this case, methane gas crystalline hydrates (CH ₄ ) in a volume of 40 m ³ are used as a proppant, injection is carried out at a pressure of 30 MPa and a temperature of 25 ° C. After the fracture 8 of the formation 2, gas methane crystalline hydrates decompose (figure 5). Crystal hydrates are decomposed by adding a 25% aqueous methanol solution to the mixture of fracturing fluid with a proppant at a bottomhole pressure of 34 MPa, which was established after the fracturing. In this case, a gas phase 9 is liberated from crystalline hydrates in a volume of 18.8 m ³ . In connection with good penetration, the gas phase additionally wedges macro- and microcracks 10 of fracture 8 of formation 2 by 12.7%.

EXAMPLE 2

Hydraulic fracturing (Fig. 4) at the bottom of a well with a depth of 2300 m with a reservoir pressure of 19 MPa is performed in cold atmospheric conditions by pumping a mixture of fracturing fluid 3 (ClearWater) into a reservoir in a volume of 120 m ³ from a reservoir 5 with a proppant 6, supplied from the container 7 and increasing the bottomhole pressure to 45 MPa. At the same time, gas crystalline hydrates of nitrogen (N ₂ ) in a volume of 40 m ³ are used as a proppant; injection is carried out at a pressure of 30 MPa and a temperature of 5 ° C. After the fracture 8 of the formation 2, gas methane crystalline hydrates decompose (figure 5). Crystal hydrates are decomposed by adding a 25% aqueous methanol solution to the mixture of fracturing fluid with a proppant at a bottomhole pressure of 34 MPa, which was established after the fracturing. In this case, a gas phase 9 is liberated from crystalline hydrates in a volume of 18.8 m ³ . In connection with good penetration, the gas phase additionally wedges macro- and microcracks 10 of fracture 8 of formation 2 by 12.9%.

EXAMPLE 3

Hydraulic fracturing (Fig. 4) is carried out as in Example 1, and the crystalline hydrates are decomposed (Fig. 5) by heating to 30 ° C using the heating cable 14 of the power generating installation 15. In this case, the pressure of the gas phase increases from 9 to 55 MPa (extrapolation of the equilibrium line to figure 1 conditionally does not show these parameters). Under the influence of this pressure, the gas phase penetrates into macro- and microcracks 10 and wedges them, increasing the volume of cracks by about 15%.

EXAMPLE 4

Hydraulic fracturing (Fig. 4) is carried out as in Example 1, and the crystalline hydrates are decomposed (Fig. 5), adding a 25% aqueous solution of methanol to the mixture of fracturing fluid 3 with proppant 6 and heating it to 30 ° C using a heating cable 14 installations 15. At the same time, the rate of decomposition of gas crystalline hydrates increases 2.5-3.2 times due to which the expansion of the gas phase in macro- and microcracks 10 is shock-like. As a result of this, fracture fracturing and wedging occurs more intensively, increasing the volume of cracks by about 17%.

EXAMPLE 5

Hydraulic fracturing (Fig. 4) is carried out over 4 hours with a frequency of 30 min; multiple: injection of a mixture of 3 fracturing fluids 4 with a unit volume of 20-30 m ³ with a proppant 6 of 7-10 m volume under a pressure of 30 MPa; increase bottomhole pressure (figure 4) to 45 MPa for 5-7 minutes; the decomposition of crystalline hydrates (figure 5) by exposure to a solution of methanol and heating according to examples 1-4. Under such conditions, baric waves with an amplitude of 74 MPa and thermal waves with an amplitude of 60 ° C are formed in the reservoir. These waves intensify the formation of 2 additional macro- and microcracks 10 in the formation by 23% -27%. This helps to increase the permeability of the reservoir, which, ultimately, increases the efficiency of the hydrocarbon production process.

Claims (4)

1. A method of hydraulic fracturing, which includes injecting a mixture of fracturing fluid with a proppant into the reservoir, characterized in that gas crystalline hydrates are used as the proppant, injection is carried out under thermobaric conditions for the existence of the latter, and gas crystalline hydrates are decomposed after the formation is fractured to produce a gas phase additionally propping up macro- and microcracks of fracturing, and pumping a mixture of fracturing fluid with a proppant, fracturing and decomposition of crista llohydrates are produced once or repeatedly. 2. The method according to claim 1, characterized in that the use of crystalline hydrates of hydrocarbon and / or non-hydrocarbon gases. 3. The method according to claim 1, characterized in that the crystalline hydrates are decomposed by adding an antihydrate reagent to the mixture of the fracturing liquid with a proppant and / or changing its thermobaric parameters. 4. The method according to claim 1, characterized in that the multiple injection of a mixture of fracturing fluid with a proppant, fracturing and decomposition of crystalline hydrates is performed with the formation of thermal or / and pressure waves in the reservoir.

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