RU2645688C1 - Carbonate formation hydraulic fracturing method - Google Patents

Abstract

FIELD: oil industry.

SUBSTANCE: invention relates to oil industry and may be used in hydraulic fracturing of a carbonate formation (FGD). Method includes perforating the walls of the well in its necessary interval with channels of a depth not less than the extent of the stress concentration zone in the rocks from the wellbore, descent of the tubing string into the zone of fracturing with sealing of the annular space with a packer above the perforation interval, cyclic injection and squeezing of a gel-like fracturing fluid and acid into the well. In this case, the permeability and thickness of the formation are predetermined. As a gel-like fracturing fluid, a linear gel with a concentration of 3 kg/m³ is used, prepared at the rate of 1.5 m³ on 1 m of a layer thickness, and as acid – a mixture of hydrochloric and hydrofluoric acids, prepared at the rate of 1 m³ per 1 m of the formation thickness, mixture of a 15 % aqueous solution of hydrochloric acid and a hydrocarbon solvent, prepared at a rate of 0.5 m³ per 1 m of the thickness of the formation. Prepared solutions are divided into three equal portions and sequentially injected in three cycles. Moreover, at a permeability of more than 100 mD, a mixture of a 12 % aqueous solution of hydrochloric acid and a 3 % aqueous solution of hydrofluoric acid is pumped, and a mixture of a 15 % aqueous solution of hydrochloric acid with a hydrocarbon solvent at a ratio of 9:1, with a permeability of 20 to 100 mD, a mixture of a 10 % aqueous solution of hydrochloric acid and a 2 % aqueous solution of hydrofluoric acid is pumped, and a mixture of a 15 % aqueous solution of hydrochloric acid with a hydrocarbon solvent at a ratio of 8:2, with a permeability less than 20 mD, a mixture of a 6 % aqueous solution of hydrochloric acid and a 1 % aqueous solution of hydrofluoric acid is pumped, and a mixture of a 15 % aqueous solution of hydrochloric acid with a hydrocarbon solvent at a ratio of 7:3. After completion of the last injection cycle, the squeezing is carried out with fresh water.

EFFECT: technical effect: to maintain the conductivity of the fracture after the fracturing with increasing efficiency of hydraulic fracturing.

1 cl, 3 dwg

Description

The invention relates to the oil industry and may find application in hydraulic fracturing of a carbonate formation.

A known method of hydraulic fracturing (hydraulic fracturing) (patent RU No. 2451174, IPC E21B 43/267, published on 05/20/2012 in bull. No. 14), including the descent into the well of the column of tubing into the hydraulic fracturing zone, sealing annular the space of the well with a packer, injecting gas, fracturing fluid under pressure along the tubing string, performing hydraulic fracturing with the formation of a fracture, supplying a proppant and subsequent development of the well, while the gas is supplied together with the fracturing fluid, which is used as crude oil, and the proppant after fluid injection and rupture, the gas being inert and injected in a volume of 20-30% at a pressure of 8 MPa of the volume of the rupture liquid, and an acid emulsion with the addition of inert gas in a volume of 20-30% at a pressure of 9 MPa of the volume of the proppant is used as a proppant after which the cycle of pumping the gas-discontinuity liquid and the proppant is repeated 3-6 times, and before being developed into the tubing string, the process liquid with inert gas is pumped in a volume of 20-30% at a pressure of 10 MPa with a total volume equal to one and a half times internal the volume of the tubing, followed by processing delay of 2-3 hours, wherein in each cycle of the fracturing fluid and proppant pumped in equal parts by volume.

The disadvantages of this method are:

- firstly, the low efficiency of hydraulic fracturing associated with limiting the development of a fracture in length, since hydraulic fracturing is carried out by cyclic injection of a fracturing fluid and a proppant, therefore, when a fracture is wedged, an acid emulsion reacts with the rock in the near-wellbore zone. For this reason, it is not possible to deliver the oil-acid emulsion deep into the reservoir, therefore, the fracture does not develop in length, and when the fracturing fluid and the proppant are cycled in equal parts of the total volume, the fracture only partially increases in volume;

- secondly, the low quality of the crack opening, since the formed crack has a low filtration capacity due to the formation of a filter cake on the walls of the crack due to subsidence in the pores of the crack, not destroyed by an oil emulsion;

- thirdly, the low quality of cleaning the bottom-hole formation zone from reaction products. As a result, the stratified pores of the formation reduce oil recovery after hydraulic fracturing;

- fourthly, the use of crude oil creates a high fire hazard and requires more technical and quality control.

The closest in technical essence and the achieved result is a method of hydraulic fracturing of a carbonate formation in a well (patent RU 2455478, IPC E21B 43/26, published in bulletin No. 19 dated July 10, 2012), including perforation of the walls of the well in the required interval of the well channels with a depth not less than the length of the zone of stress concentration in the rocks from the wellbore, descent of the pipe string into the hydraulic fracturing zone with the packer sealing the annulus above the perforation interval and cyclic injection of a gel-like fracturing fluid into the well, before hydraulic fracturing, the well is filled with technological fluid for 0.2-0.4 volumes of the wellbore, the total volume of injected gel-like fracturing fluid is calculated, and the gel-like fracturing fluid is pumped in equal portions in 3-5 cycles with 0.7 portions of acid being pumped after them. -0.75 volume of gel-like liquid of rupture, at the end of the last injection cycle, chemicals are forced into the crack by the injection of marketable oil in a 1.5-fold volume of the pipe string, followed by an exposure of 1-2 hours, after which they add the reaction products of acid with the rock, remove the packer and remove it from the pipe string from the well.

The disadvantages of this method are:

- firstly, the low conductivity of the fracture due to the fact that inside the fracture the gel-like fracturing fluid reacts with acid, as a result of which a polymer precipitates, which plugs the pores of the formation;

- secondly, the low efficiency of hydraulic fracturing, due to the fact that the composition of the acid and its concentration used in the implementation of the method for etching the cracks do not take into account the permeability of the formation. This reduces the quality of etching of the fracture cracks and the magnitude of its opening;

- thirdly, the low productivity of the well after hydraulic fracturing, since it is impossible to produce acid deviations into less permeable layers of the formation in order to form a network of branched microcracks;

- fourthly, when carrying out hydraulic fracturing, salable oil is used, which creates a high fire hazard and has a negative impact on the environment when the oil spills at the wellhead.

The technical objectives of the invention are to preserve the conductivity of the fracture and increase the efficiency of hydraulic fracturing, increase the productivity of the well after hydraulic fracturing and eliminate fire hazards during hydraulic fracturing and the negative impact on the environment.

The tasks are solved by the method of hydraulic fracturing of a carbonate formation — hydraulic fracturing in a well, including perforation of the walls of the well in the required interval of the well with channels not less than the length of the stress concentration zone in the rocks from the well bore, lowering the tubing string — tubing to the hydraulic fracturing zone with annulus sealing packer above the perforation interval, cyclic injection and injection into the well of a gel-like fracturing fluid and acid.

What is new is that the permeability and thickness of the formation are preliminarily determined, a linear gel with a concentration of 3 kg / m ³ prepared at the rate of 1.5 m ³ per 1 m of the formation thickness is used as a gel-like fracturing liquid, and a mixture of hydrochloric and hydrofluoric acid, prepared at the rate of 1 m ³ per 1 m of the formation thickness, an additional mixture of a 15% aqueous solution of hydrochloric acid with a hydrocarbon solvent is additionally injected, prepared at the rate of 0.5 m ³ per 1 m of the formation thickness, the prepared solutions are divided into three equal by and perform sequential injection in three cycles, with a permeability of more than 100 mD, a mixture of a 12% aqueous hydrochloric acid solution and a 3% aqueous hydrofluoric acid solution is pumped, and a mixture of a 15% aqueous hydrochloric acid solution with a hydrocarbon solvent at a ratio of 9 : 1, with a permeability of 20 to 100 mD, a mixture of a 10% aqueous solution of hydrochloric acid and a 2% aqueous solution of hydrofluoric acid is pumped, and a mixture of a 15% aqueous solution of hydrochloric acid with a hydrocarbon solvent at a ratio of 8: 2, with a permeability n a mixture of 6% aqueous hydrochloric acid solution and 1% aqueous hydrofluoric acid solution is injected with 20 mD, and a mixture of 15% aqueous hydrochloric acid solution with a hydrocarbon solvent at a ratio of 7: 3; at the end of the last injection cycle, fresh water is pressed .

In FIG. 1, 2 and 3 schematically and sequentially depict the proposed method.

The proposed method of hydraulic fracturing of a carbonate formation is as follows.

The hydraulic fracturing method in well 1 (see Fig. 1) includes perforation of the walls of the well with channels 2 with a depth of at least the length of the stress concentration zone in the rocks from the wellbore 1. Next, the tubing string 3 with packer 4 is lowered into the fracturing zone 1 so that the packer 4 was 5-10 m above the roof 5 of the formation 6 subject to hydraulic fracturing, after which annular space was sealed, i.e. make the passage packer of any known design. Before hydraulic fracturing (see Fig. 1) at the wellhead, the upper end of the pipe string 3 is tied through the pump units 7, 8, 9 with the corresponding containers for gel-like liquid 10, a mixture of acids 11, an acid emulsion 12. On the discharge lines of the pump units 7, 8 and 9, the corresponding valves 13, 14, 15 are installed.

In the process of hydraulic fracturing, a fracture crack is formed and developed by triple cyclic injection of chemical reagents into formation 6 (see Fig. 1, 2 and 3) along the tubing string 3.

Each cycle consists of a sequential injection of a gel-like fracturing liquid, a mixture of acids and an acid emulsion.

As a gel-like fracturing liquid, a linear gel with a concentration of 3.0 kg / m ^{3 is used} . This means that 1.0 m ^{3 of} fresh water with a density of 1000 kg / m ³ contains 3.0 kg of gelling agent of any well-known manufacturer.

Before hydraulic fracturing, the necessary amount of chemical reagents is prepared in the tank based on the assumption that in each cycle the linear gel is pumped in portions of 1.5 m ³ per 1 m of formation thickness 6, divided by the number of cycles, an acid mixture is 1 m ³ per 1 m of formation thickness 6 divided by the number of cycles, and the acidic emulsion - 0.5 m ³ per 1 m of formation thickness 6, divided by the number of cycles. For example, the thickness of the formation 6 to be subjected to hydraulic fracturing is 6 m, taking into account the foregoing, the proposed hydraulic fracturing process is implemented in three cycles, and the required amount of chemicals for each cycle is calculated:

- a linear gel with a concentration of 3 kg / m ^{3 is} pumped in portions of

1.5 m ³ / m m⋅6 / 3 = 9.0 m ^3/3 = 3.0 m ^3;

- acid mixture injected in portions of 1.0 m ³ / m m⋅6,0 / 3 = 6.0 m ^3/3 = 2.0 m ^3;

- an acid emulsion was injected in portions of 0.5 m ³ / m m⋅6,0 / 3 = 3.0 m ^3/3 = 1.0 m ^3.

Next, the concentration of the mixture of acids and acid emulsion is selected depending on the permeability of the rocks of the formation 6, which was experimentally selected.

A mixture of acids consists of a mixture of hydrochloric acid - HCI and hydrofluoric acid - HF. The efficiency of etching a hydraulic fracture and increasing the magnitude of its opening depends on the concentration of the acid mixture, which, in turn, depends on the permeability of the formation rocks 6.

With permeability of formation rocks over 100 mD concentration:

- a mixture of acids: 12% aqueous HCl and 3% aqueous HF. A mixture of acids is prepared at the wellhead in a container 11 for a mixture of acids. To prepare a 1.0 m ³ mixture of acids with a concentration of (12% aqueous HCl, 3% aqueous HF), HCl — 0.12 m ³ ; HF - 0.03 m ³ ; water - the rest;

- acid emulsion: a mixture of a 15% HCl solution with a hydrocarbon solvent at a ratio of 9: 1. An acidic emulsion is prepared at the wellhead in an acid emulsion tank 12. To prepare 1.0 m ³ acid emulsion at a ratio of 9: 1 (15% aqueous HCl: hydrocarbon solvent), HCl — 0.9 m ³ ; hydrocarbon solvent - 0.1 m ³ .

Acids of any manufacturer may be used.

As the hydrocarbon solvent, for example, a distillate of any known manufacturer is used.

With permeability of formation rocks from 20 to 100 mD concentration:

- a mixture of acids: 10% aqueous HCl and 2% aqueous HF. A mixture of acids is prepared at the wellhead in a container 11 for a mixture of acids. To prepare a 1.0 m ³ mixture of acid with a concentration of (10% aqueous HCl, 2% aqueous HF), HCl — 0.10 m ³ ; HF - 0.02 m ³ ; water - the rest;

- acid emulsion: a mixture of a 15% HCl solution with a hydrocarbon solvent in a ratio of 8: 2. An acidic emulsion is prepared at the wellhead in an acid emulsion tank 12. To prepare 1.0 m ^{3 of an} acidic emulsion at a ratio of 8: 2 (15% aqueous HCl: hydrocarbon solvent), HCl — 0.8 m ³ ; hydrocarbon solvent - 0.2 m ³ .

With permeability of formation rocks below 20 mD concentration:

- a mixture of acids: 6% aqueous HCl and 1.0% aqueous HF. A mixture of acids is prepared at the wellhead in an acid tank 11. To prepare a 1.0 m ³ mixture of acids with a concentration of (6% aqueous HCl, 1% aqueous HF), HCl is mixed with 0.06 m ³ ; HF - 0.01 m ³ ; water - the rest;

- acid emulsion: a mixture of a 15% aqueous HCl solution with a hydrocarbon solvent in a ratio of 7: 3. An acidic emulsion is prepared at the wellhead in an acid emulsion tank 12. To prepare 1 m ^{3 of an} acidic emulsion at a ratio of 8: 2 (a mixture of a 15% aqueous solution of HCl: hydrocarbon solvent), HCl is mixed - 0.7 m ³ ; hydrocarbon solvent - 0.3 m ³ .

The efficiency of hydraulic fracturing increases, since the composition of the acid and the concentration of the mixture of acids and acid emulsion used to etch the formed crack during the implementation of the method are selected depending on the permeability of the formation rock, which improves the quality of etching of the fracture and increases the size of its opening. For example, the permeability of formation rocks is 120 mD with a formation thickness of 6 equal to 2 m, consisting of three injection cycles. Then the concentration of chemicals:

- a mixture of acids: 12% aqueous HCl and 3% aqueous HF;

- acid emulsion: a mixture of a 15% aqueous hydrochloric acid solution with a hydrocarbon solvent in a ratio of 9: 1.

Thus, in a container for a gel-like liquid 10, they prepare: 1.5 m ³ / m /2 m (formation thickness) ⋅3 (number of cycles) = 9.0 m ^{3 of a} linear gel with a concentration of 3.0 kg / m ³ .

In a container for a mixture of acids 11, they prepare: 1.0 m ³ / m (2 m (reservoir thickness) ⋅3 (number of cycles) = 6.0 m ^{3 of a} mixture of acids of the following concentration: 12% aqueous HCl and 3% - aqueous solution of HF.

In a container for an acidic emulsion, 0.5 m ³ / m⋅2 m (layer thickness) ⋅3 (number of cycles) = 3.0 m ^{3 of an} acidic emulsion is prepared at a ratio of 9: 1 (a mixture of a 15% aqueous HCl: hydrocarbon solution solvent), i.e. mixed with HCl - 0.9 m ³ ⋅3 = 2.7 m ³ ; hydrocarbon solvent - 0.1⋅3 = 0.3 m ³ .

Begin the hydraulic fracturing process.

First cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3, 3.0 m ^{3 of} linear gel with a concentration of 3 kg / m ^{3 are} pumped into the formation. The initial fracture gap 16 'is formed in the formation 6 (see Fig. 1). Next, close the valve 13, open the valve 14 with the valve 15 closed, start the pump unit 8 and from the tank 11 for the acid mixture using the pump unit 8 through the tubing string 3, pump 2.0 m ³ of the acid mixture into the reservoir at a concentration of 12% aqueous HCl solution and a 3% aqueous solution of HF, etch and open a crack 16 '. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started and from the tank 12 for the acidic emulsion using the pumping unit 9 through the tubing string 3, 1.0 m ^{3 of the} acidic emulsion are pumped into the formation at a 9: 1 ratio of mixture 15 % HCl solution with a hydrocarbon solvent.

As a result of exposure to the acidic emulsion from the fracture 16 ', new branched cracks 17' are formed, directed into the less permeable interlayers of the formation 6.

Second cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3, 3.0 m ^{3 of} linear gel with a concentration of 3 kg / m ^{3 are} pumped into the formation. An initial 16 ″ fracture crack is formed in the formation 6 (see FIG. 2). Next, close the valve 13, open the valve 14 with the valve 15 closed, start the pump unit 8 and from the tank 11 for the acid mixture using the pump unit 8 through the tubing string 3, pump into the reservoir 2.0 m ^{3 of a} mixture of acids with a concentration of 12% aqueous HCl solution and 3% aqueous HF solution, etch and open a 16 '' crack. Then valve 14 is closed, valve 15 is opened at a closed valve 13, start the pump unit 9 and from the reservoir 12 to the acidic emulsion via the pump unit 9, the tubing string is injected into the reservoir 3 to 1.0 m ³ acidic emulsion a mixture of 15% aqueous solution HCl: hydrocarbon solvent at a ratio of 9: 1. As a result of the action of the acidic emulsion from the 16 "fracture, new branched 17" fractures are formed, directed into the less permeable interlayers of the formation 6.

Third cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3, 3.0 m ^{3 of} linear gel with a concentration of 3 kg / m ^{3 are} pumped into the formation. An initial 16 ину ’fracture crack is formed in the formation 6 (see FIG. 3). Next, close the valve 13, open the valve 14 with the valve 15 closed, start the pump unit 8 and from the tank 11 for the acid mixture using the pump unit 8 through the tubing string 3, pump into the reservoir 2.0 m ^{3 of a} mixture of acids with a concentration of 12% aqueous HCl solution and 3% aqueous HF solution, etch and open a 16 '' crack. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started and from the tank 12 for the acidic emulsion, using the pump unit 9, 6 1.0 m ^{3 of an} acidic emulsion of a 15% aqueous mixture are pumped into the formation 6 through a tubing string 3 HCl solution: hydrocarbon solvent at a ratio of 9: 1. As a result of exposure to the acidic emulsion from the 16 ″ ″ fracture, new 17 ″ ″ branched cracks are formed, directed into the less permeable layers of the formation 6.

The productivity of the well increases due to the formation of the initial fracture with its subsequent development, etching and the creation of a network of branched fractures in less permeable layers of the formation, namely:

- the first cycle consists of the formation of the initial fracture of the fracture, the etching of the initial fracture of the fracture and the formation of new ones by deflecting the acid into less permeable layers of the formation;

- the second and subsequent cycles consist of the sequential development of the initial fracture and their etching and the formation of new ones by deflecting the acid into less permeable layers of the formation.

At the end of the third cycle, the injected chemicals are sold from the tubing string 3 to the reservoir 6 with fresh water, for example, with a density of 1000 kg / m ³ in the 1.5-fold volume of the tubing string 3, for example, in the volume of 6.0 m ³ , from the auto capacity 18 using a pump unit 7 (see Fig. 3) through an open valve 13, with closed valves 14 and 15. After that, well 1 remains in response to the formation rock for 1-2 hours

The use of fresh water instead of crude oil for the sale of chemicals from the tubing string 3 into the reservoir after the completion of the last injection cycle eliminates the fire hazard of hydraulic fracturing and does not adversely affect the environment.

Then, the reaction products of the acid with the rock are removed by any known method, for example, swabbing (not shown in FIGS. 1, 2 and 3), along the tubing string 3 (see FIG. 3) in a double volume of wellbore 1, for example, in a volume of 30.0 m ³ . Then tear the packer 4 and remove it with the tubing string 3 from the well 1. The hydraulic fracturing process is completed.

As a result of hydraulic fracturing, the conductivity of the fracture is preserved, since a linear gel with a concentration of 3.0 kg / m ³ is used as a gel-like liquid, which excludes a chemical reaction with acid and does not clog the pores of the formation, since the linear gel does not precipitate.

The above is an example with permeability of formation rocks over 100 mD.

Below, we consider two examples of the implementation of the method with the permeability of formation rocks from 20 to 100 mD and below 20 mD.

1. An example of a specific application for the permeability of formation rocks 6 from 20 to 100 mD.

The permeability of the formation rocks is 70 mD; the thickness of the formation 6 is 9 m.

The proposed hydraulic fracturing process is implemented in three cycles.

Then in each cycle:

- a linear gel with a concentration of 3 kg / m ^{3 is} pumped in portions:

1.5 m ³ / m m⋅9,0 / 3 = 13.5 m ^3/3 = 4.5 m ^3;

- a mixture of acids is pumped in portions:

1.0 m ³ / m m⋅9,0 / 3 = 9 m ^3/3 = 3 m ^3;

- the acidic emulsion is pumped in portions:

0.5 m ³ / m m⋅9,0 / 3 = 4.5 m ^3/3 = 1.5 m ^3.

Next, for the permeability of the rocks of the formation 6, equal to 70 MD, select the concentration:

- a mixture of acids: 10% aqueous HCl and 2% aqueous HF;

- acid emulsion: a mixture of a 15% aqueous HCl solution with a hydrocarbon solvent in a ratio of 8: 2.

Thus, in a container for a gel-like liquid 10, 13.5 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ are prepared.

In a container for a mixture of acids 11 prepare 9 m ^{3 a} mixture of acids with a concentration of: 10% aqueous solution of HCl and 2% aqueous solution of HF.

In a container for acid emulsion 12 prepare 4.5 m ³ acid emulsion with a concentration of: 15% aqueous HCl with a hydrocarbon solvent in a ratio of 8: 2.

Begin the hydraulic fracturing process.

First cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 4.5 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ . The initial fracture gap 16 'is formed in the formation 6 (see Fig. 1). Next, close the valve 13, open the valve 14 with the valve closed 15, start the pump unit 8 and from the tank 11 for the mixture of acids using the pump unit 8 through the tubing string 3 injected into the reservoir 3.0 m ^{3 of a} mixture of acids with a concentration of 10% aqueous HCl solution and a 2% aqueous solution of HF, etch and open the crack 16 '. Then close the valve 14, open the valve 15 with the valve closed 13, start the pump unit 9 and from the tank 12 for the acidic emulsion using the pump unit 9 through the tubing string 3 pump 1.5 m ^{3 of the} acidic emulsion into the reservoir with a concentration of 15% - aqueous solution of HCl with a hydrocarbon solvent at a ratio of 8: 2. As a result of exposure to the acidic emulsion from the fracture 16 ', new branched cracks 17' are formed, directed into the less permeable interlayers of the formation 6.

Second cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 4.5 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ . An initial 16 ″ fracture crack is formed in the formation 6 (see FIG. 2). Next, close the valve 13, open the valve 14 with the valve closed 15, start the pump unit 8 and from the tank 11 for the mixture of acids using the pump unit 8 through the tubing string 3 injected into the reservoir 3.0 m ^{3 of a} mixture of acids with a concentration of 10% aqueous solution and HCl and a 2% aqueous HF solution, etch and open a 16 '' crack. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started and from the tank 12 for the acidic emulsion, with the help of the pump unit 9, 6 1.5 m ^{3 of an} acidic emulsion are pumped into the formation 6 through a tubing string 3 with a concentration of 15% aqueous solution of HCl with a hydrocarbon solvent in a ratio of 8: 2. As a result of the action of the acidic emulsion from the 16 "fracture, new branched 17" fractures are formed, directed into the less permeable interlayers of the formation 6.

Third cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 4.5 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ . An initial 16 ину ’fracture crack is formed in the formation 6 (see FIG. 3). Next, the valve 13 is closed, valve 14 is opened at a closed valve 15, the pump unit 8 is started from the vessel 11 and for a mixture of acids with the pump unit 8, the tubing string is injected into the reservoir 3 3.0 m ³ mixture of acids at a concentration of 10% aqueous HCl solution and 2% aqueous HF solution, etch and open a 16 '' crack. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started and from the tank 12 for the acidic emulsion, with the help of the pump unit 9, 6 1.5 m ^{3 of an} acidic emulsion are pumped into the formation 6 through a tubing string 3 with a concentration of 15% solution of HCl with a hydrocarbon solvent in a ratio of 8: 2. As a result of exposure to the acidic emulsion from the 16 ″ ″ fracture, new 17 ″ ″ branched cracks are formed, directed into the less permeable layers of the formation 6.

At the end of the third cycle, chemicals are pumped into the NTK 3 column through the tubing string 3 into reservoir 6 with fresh water, for example, with a density of 1000 kg / m ³ in a 1.5 times volume of the tubing string 3, for example, in a volume of 6 m ³ , from auto capacity 18 using pump unit 7 (see Fig. 3) through an open valve 13 with closed valves 14 and 15. After that, well 1 remains exposed to acid reaction with the formation rock for 1-2 hours. Next, the reaction products of the acid with the rock are removed by any known method, for example swabbing (not shown in FIGS. 1, 2 and 3), along the tubing string 3 (see Fig. 3) in a double volume of the wellbore 1, for example, in the volume of 30.0 m ³ . Then tear the packer 4 and remove it with the tubing string 3 from the well 1. The hydraulic fracturing process is completed.

2. An example of a specific application for the permeability of formation rocks below 20 mD.

The permeability of the formation rocks is 10 mD, the thickness of the formation 6 is 4 m

The proposed hydraulic fracturing process is implemented in three cycles.

Then in each cycle:

- a linear gel with a concentration of 3.0 kg / m ³ is injected in portions: 1.5 m ³ ⋅4 / 3 = 6m ^3/3 = 2.0 m ^3;

- acid mixture injected portionwise: 1.0 m ³ ⋅4 / 3 = 4 m ^3/3 = 1.33 m ^3;

- an acid emulsion was pumped portionwise: 0.5 m ³ ⋅4 / 3 = 2.0 m ^3/3 = 0.67 m ^3.

Next, for the permeability of the rocks of the formation 6, equal to 10 MD, select the concentration:

- a mixture of acids: 6% aqueous HCl and 1.0% aqueous HF;

- acid emulsion: a mixture of a 15% HCl solution with a hydrocarbon solvent in a ratio of 7: 3.

Thus, in a container for a gel-like liquid 10, 6 m ^{3 of a} linear gel with a concentration of 3.0 kg / m ³ are prepared.

In a container for a mixture of acids 11 prepare 4 m ^{3 a} mixture of acids with a concentration of: 6% aqueous solution of HCl and 1% aqueous solution of HF.

In a container for an acidic emulsion, 2 m ^{3 of an} acidic emulsion is prepared with a concentration of: a mixture of a 15% HCl solution with a hydrocarbon solvent in a ratio of 7: 3.

Begin the hydraulic fracturing process.

First cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 2.0 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ into the reservoir . The initial fracture gap 16 'is formed in the formation 6 (see Fig. 1). Then the valve 13 is closed, the valve 14 is opened with the valve 15 closed, the pump unit 8 is started, and from the tank 11 for the acid mixture, using the pump unit 8 through the tubing string 3, 1.33 m ³ of the acid mixture are pumped into the formation with a concentration of 6% aqueous HCl solution and a 1.0% aqueous solution of HF, etch and open a crack 16 '. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started, and from the tank 12 for the acidic emulsion, with the help of the pump unit 9, 0.67 m ^{3 of the} acidic emulsion are pumped into the formation through the tubing string 3 with a concentration of 15% - HCl solution with a hydrocarbon solvent at a ratio of 7: 3. As a result of exposure to the acid emulsion of the fracture 16 ', new branched cracks 17' are formed, directed into the less permeable interlayers of the formation 6.

Second cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 2.0 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ into the reservoir . An initial 16 ″ fracture crack is formed in the formation 6 (see FIG. 2). Then the valve 13 is closed, the valve 14 is opened with the valve 15 closed, the pump unit 8 is started, and from the tank 11 for the acid mixture, using the pump unit 8 through the tubing string 3, 1.33 m ³ of the acid mixture are pumped into the formation with a concentration of 6% aqueous HCl solution and 1% aqueous HF solution, etch and open a 16 '' crack. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started, and from the tank 12 for the acidic emulsion, using the pump unit 9, 6 0.67 m ^{3 of} acidic emulsion are pumped into the formation through a tubing string 3 with a concentration of 15% solution of HCl with a hydrocarbon solvent in a ratio of 7: 3. As a result of the action of the acidic emulsion from the 16 "fracture, new branched 17" fractures are formed, directed into the less permeable interlayers of the formation 6.

Third cycle

Open the valve 13, the valves 14 and 15 are closed, start the pump unit 7 and from the tank 10 for the gel-like fracturing fluid using the pump unit 7 through the tubing string 3 pump 2.0 m ^{3 of} linear gel with a concentration of 3.0 kg / m ³ into the reservoir . An initial 16 ину ’fracture crack is formed in the formation 6 (see FIG. 3). Then the valve 13 is closed, the valve 14 is opened with the valve 15 closed, the pump unit 8 is started, and from the tank 11 for the acid mixture, using the pump unit 8 through the tubing string 3, 1.33 m ³ of the acid mixture are pumped into the formation with a concentration of 6% aqueous HCl solution and 1% aqueous HF solution, etch and open a 16 '' crack. Then the valve 14 is closed, the valve 15 is opened with the valve 13 closed, the pump unit 9 is started, and from the tank 12 for the acidic emulsion, using the pump unit 9, 6 0.67 m ^{3 of} acidic emulsion are pumped into the formation through a tubing string 3 with a concentration of 15% solution of HCl with a hydrocarbon solvent in a ratio of 7: 3. As a result of exposure to the acidic emulsion from the 16 ″ ″ fracture, new 17 ″ ″ branched cracks are formed, directed into the less permeable layers of the formation 6.

At the end of the third cycle, chemicals are pumped from the tubing string 3 to reservoir 6 with fresh water, for example, with a density of 1000 kg / m ³ in a half-time volume of the tubing string 3, for example, in a volume of 6 m, from auto capacity 18 using a pump unit 7 (see Fig. 3) through the open valve 13 with the closed valves 14 and 15. After that, the well 1 remains at the reaction of the acid with the rock of the formation 6 for 1-2 hours. Next, the reaction products of the acid with the rock are removed by any known method, for example swabbing (in FIG. 1, 2 and 3 not shown), along the tubing string 3 (see Fig. 3) in twice the volume of the wellbore 1, for example, in the volume of 30.0 m ³ . Then tear the packer 4 and remove it with the tubing string 3 from the well 1. The hydraulic fracturing process is completed.

The proposed method of hydraulic fracturing in the well allows:

- maintain the conductivity of the cracks after hydraulic fracturing;

- increase the efficiency of hydraulic fracturing;

- increase well productivity after hydraulic fracturing;

- eliminate fire hazard during hydraulic fracturing and negative impact on the environment.

Claims (1)

The method of hydraulic fracturing of a carbonate formation — hydraulic fracturing in a well, including perforation of the walls of the well in the required interval of the well with channels of depth not less than the length of the stress concentration zone in the rocks from the wellbore, lowering the tubing string — tubing to the hydraulic fracturing zone with the packer above the interval perforation, cyclic injection and pushing into the well of a gel-like fracturing fluid and acid, characterized in that the permeability and thickness of the formation are previously determined, in as a gel-like fracturing fluid, a linear gel with a concentration of 3 kg / m ³ prepared at the rate of 1.5 m ³ per 1 m of the formation thickness is used, and as an acid, a mixture of hydrochloric and hydrofluoric acids prepared at the rate of 1 m ³ per 1 m of thickness formation, additionally inject a mixture of a 15% aqueous solution of hydrochloric acid with a hydrocarbon solvent prepared at the rate of 0.5 m ³ per 1 m of the thickness of the formation, the prepared solutions are divided into three equal portions and sequential injection is carried out in three cycles, and with permeability over 100 mD injected a mixture of 12% aqueous hydrochloric acid and 3% aqueous hydrofluoric acid solution, and a mixture of 15% aqueous hydrochloric acid with hydrocarbon solvent at a ratio of 9: 1, with a permeability of 20 to 100 mD injected a mixture 10% aqueous hydrochloric acid solution and 2% aqueous hydrofluoric acid solution, and a mixture of a 15% aqueous hydrochloric acid solution with a hydrocarbon solvent at a ratio of 8: 2, with a permeability below 20 mD, a mixture of a 6% aqueous hydrochloric solution is pumped and 1% aqueous solution hydrofluoric acids, and a mixture of a 15% aqueous solution of hydrochloric acid with a hydrocarbon solvent at a ratio of 7: 3, at the end of the last injection cycle, selling is carried out with fresh water.

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