RU2564312C1 - Method of deposit hydraulic fracturing in well - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes perforation of the well walls in the deposit interval by channels with depth at least equal to length of zone of stresses concentration in rocks from the well hole, run of the string with packer such that the bottom end of the string will be at level of the deposit top, packer seating above the perforated deposit top, determination of total volume of gel fracturing liquid prior to the deposit hydraulic fracturing, the gel fracturing liquid injection in the underpacker zone, creation in the under packer zone of the deposit hydraulic fracturing pressure, and the cracks creation in the deposit with further their casing in the deposit by injection of the carrying liquid with proppant, well holding for the pressure bleeding-off, packer releasing and removal with the string from the well. At the wellhead the pipes string above the packer at distance 10 m outside is equipped with jet pump, then string is run in the well, and packer is seated above the perforated deposit top. Then in the string the flexible tubes string is rum such that bottom end of the flexible tubes string will be below the pipes string end and at the middle of the deposit, at the wellhead the space between the pipes string and the flexible tubes string is sealed, total volume of the gel fracturing liquid is determined, this volume is divided to two equal parts. The first part is the fracturing liquid, the second part is carrying liquid. Via the flexible tubes string the first part, i.e. fracturing liquid is injected in the under packer zone, and in the under packer zone the pressure of the deposit hydraulic fracturing is created with the cracks creation in the deposit. Then the cracks in the deposit are cased by the injection of the second part, i.e. carrying liquid with the proppant. At that the proppant of lower and larger fractions is used as the proppant. The carrying liquids with smaller fraction proppant 20/40 mesh and larger fraction proppant 16/40 mesh are injected simultaneously in ratio 4:1. At that via the flexible tubes string the carrying liquid with the larger fraction proppant is injected, and via the pipes string the carrying liquid with the smaller fraction proppant is injected with gradual increasing of concentration of smaller and larger fractions of proppant in the carrying liquid. The well is held for pressure bleeding-off, at the wellhead the space between the pipes string and flexible tubes string is unsealed. At the wellhead between the pipes string and flexible tubes string a sealing ring insert is installed and press through the pipes string under overpressure to the hydraulic connection of the pipes string and jet pump. The deposit completion is performed via the jet pump. Upon the deposit completion the flexible tubes string is removed from the pipes casing, the packer is released and removed with the pipes string from the well.

EFFECT: increased efficiency of the deposit hydraulic fracturing.

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Description

The invention relates to the oil industry and may find application in hydraulic fracturing to enhance oil production.

A known method of hydraulic fracturing of a carbonate formation (patent RU No. 2460875, IPC ЕВВ 43/26, published on 09/10/2012), including the descent of the tubing string into the well - tubing with a packer and its subsequent landing, the descent of the tubing string into the string flexible pipes - HT below the lower end of the tubing, injection of water-insulating cement through a flexible pipe, hydraulic fracturing of the carbonate formation with bottom water, while the lower end of the HT is lowered to the level of oil-water contact - VNK, the space between the tubing and HT columns is sealed, and the pump is waterproofed bottomhole cement in the carbonate formation, the well is filled from the bottom to the bottom hole level, after which the space between the tubing strings and the hot well is sealed and the HT string is lifted so that its lower end is 1-2 m below the roof of the carbonate stratum, then determine the total volume of the fluid gap by the formula:

V _g = k · h _p ,

where V _g is the volume of the fracture fluid, m ³ ;

k = 1.4-1.6 - conversion factor, m ³ / m;

h _p - the thickness of the productive part of the reservoir, m,

they seal the space between the tubing and GT columns and pump the first portion of the fracturing fluid into the GT in the amount of 60-70% of the total volume V _g under a pressure of not more than 25 MPa and at a speed of not more than 2 m ³ / min, after which the remaining volume of the fracturing fluid they are pumped into the GT in 3-5 cycles, alternating with the proppant injection, which is used as 25% hydrochloric inhibited acid, and the volume of acid is determined depending on the thickness of the productive part of the carbonate formation, based on the volume of 0.2 m ^{3 of} acid 1 m of formation thickness per each injection cycle, at the end of the last injection cycle, acid is pumped with an aqueous solution of a surfactant in the volume of the GT column, followed by 1-2 hours, after which the GT column is removed from the tubing string and the well is put into operation.

The disadvantages of this method are:

- firstly, a limited scope, since this method is implemented only with hydraulic fracturing of a carbonate formation;

- secondly, a complex and lengthy hydraulic fracturing process associated with cyclic alternating injection of fracturing fluid and proppant;

- thirdly, the short-term effect of hydraulic fracturing, since fractures in the formation are not fixed by proppant, but are processed by a proppant.

The closest in technical essence is the method of hydraulic fracturing in the well (patent RU No. 2473798, IPC ЕВВ 43/26, published on January 27, 2013), including perforation of the walls of the well in the interval of the formation by channels with depth not less than the length of the stress concentration zone in the rocks from the wellbore, descent of the pipe string with the packer so that the lower end of the pipe string is at the level of the formation roof, the packer landing above the perforated formation roof, injection of a gelled fracturing fluid into the sub-packer zone, creation of a sub-packer zone ION prodavku fracturing and crack formation in the resulting gelled fracturing fluid with proppant, wherein prior to fracturing - fracturing the pipe string is filled with a process fluid and determine the total amount of gelled fracturing fluid by the formula:

V _g = K · H _p

where V _g - the total volume of the fluid gap, m ³ ;

K - transfer coefficient (K = 11-12), m ³ / m;

N _p - the height of the interval of perforation of the reservoir, m,

the total volume of the gelled fracturing fluid is divided into two parts, of which 2/3 V _g is the volume of the crosslinked gel, and 1/3 V _g is the linear gel, the hydraulic fracturing process begins by pumping the gelled fracture fluid - crosslinked gel with dynamic viscosity 150-200 Pass until a fracture in the formation is formed, after creating a fracture in the formation, the remaining 2/3 V _{g of the} volume of cross-linked gel is pumped in equal portions in 3-5 cycles with the addition of a proppant fraction 12/18 mesh with a flow rate of 1.5- 2 m ³ / min, and the proppant is introduced into the crosslinked gel stepwise with an increase m concentrations from 200 kg / m ³ to 1000 kg / m ³ , then, without stopping the hydraulic fracturing process, into the well along the pipe string, increasing the flow rate to 2.5-3 m ³ / min, pump liquid in equal portions in 3-5 cycles fracture - a linear gel with a dynamic viscosity of 30-50 Pass with the addition of a 20/40 mesh proppant fraction with a stepwise increase in concentration from 200 kg / m ³ to 1000 kg / m ³ , after the last portion of the linear gel with proppant is pumped into the pipe string of the well, they are sold into the reservoir with process fluid, while in the process of selling reduce the flow of process fluid awn 0.5-1 m ³ / min for 3.1 minutes and re-injection is resumed at a rate of 2.5-3 ^m3 / min to complete prodavki linear gel with proppant into the formation, whereupon the shutter speed for a time, 70-80% required for the pressure drop in the injection, unpack the packer and remove it from the pipe string from the well. The disadvantages of this method are:

- firstly, the low permeability of the formed cracks due to the cyclic injection of proppant of various fractions of 12/18 mesh and 20/40 mesh. As a result, the fracture is fixed at intervals by the proppant of various fractions of 12/18 mesh and 20/40 mesh one after another (without mixing), which worsens both the removal from the bottom of the formation of the spent gelled fracturing fluid during the development of the well and the flow of formation fluid to the bottom of the well;

- secondly, the low efficiency of hydraulic fracturing due to the cyclic injection of proppant of various fractions of 12/18 mesh and 20-40 mesh. This is due to the destruction of the proppant of a large fraction (12/18 mesh) in the fracture after it is fixed, which leads to the closure of the crack in the intervals fixed by the proppant of the large fraction (12/18 mesh), which leads to a decrease in oil recovery during its subsequent operation;

- thirdly, the destruction and removal of the injected proppant from the fracture in the bottomhole formation zone to the bottom of the well during the development of the formation by swabbing;

- fourthly, a complex and lengthy hydraulic fracturing process associated with the injection of two types of gelled fracturing fluid with different dynamic viscosity, proppant of various fractions and concentrations, etc.

The technical objectives of the proposal are to increase the permeability of a fixed fracture and increase the efficiency of hydraulic fracturing, as well as simplifying and shortening the duration of the hydraulic fracturing process and eliminating the destruction and removal of injected proppant from the fracture in the bottomhole formation zone to the bottom of the well during development.

The stated technical problems are solved by the method of hydraulic fracturing - hydraulic fracturing in the well, including perforation of the walls of the well in the reservoir interval with channels at least the length of the stress concentration zone in the rocks from the well bore, lowering the pipe string with a packer so that the lower end of the pipe string is at the roof level formation, packer landing over the top of the reservoir, determination of the total volume of the gelled fracturing fluid before hydraulic fracturing, injection of the fractured fracture into the sub-packer zone of the gelled fluid the formation, in the sub-packer zone of hydraulic fracturing pressure and the formation of cracks in the formation with their subsequent fixing in the formation by injection of a carrier fluid with proppant, holding the well for pressure relief, unpacking and removing the packer from the pipe string from the well.

What is new is that at the wellhead, the pipe string above the packer at a distance of 10 m is equipped with a jet pump from the outside, then the pipe string is lowered into the well and the packer is planted above the roof of the perforated formation, then the pipe string is lowered into the pipe string - GT so that the lower the end of the GT string was located below the end of the pipe string and in the middle of the formation; at the wellhead, the space between the pipe string and the GT string is sealed, the total volume of the gelled fracturing fluid is determined, and the total volume of the gelled fluid is divided the fracture into two equal parts: the first part is the fracturing fluid, the second part is the carrier fluid, the first part, the fracturing fluid, is injected into the sub-packer zone through the GT column and the fracturing pressure is created in the sub-packer zone with formation of cracks in the reservoir, then fastened fractures in the reservoir by injection of the second part - carrier fluid with proppant, and proppant of smaller and larger fractions is used as proppant, injection of carrier fluid with proppant of a fine fraction of 20/40 mesh and a large fraction of 16/40 mesh is carried out at the same time in a ratio of 4: 1, moreover, a carrier fluid with a large fraction proppant is pumped through a GT column, and a carrier fluid with a small fraction proppant is pumped through a pipe string, with a stepwise increase in the concentration of fine and large fraction proppant in a carrier fluid, the well is maintained at pressure relief, depressurization is made at the wellhead of the space between the pipe string and the GT string, a sealing ring insert is installed at the wellhead between the pipe string and the HT and push it along Onne pipes under excess pressure to the hydraulic pipe string communication with a jet pump, make the development of the formation through the jet pump, after development of the reservoir is removed from the column pipe string HT produce packer releasing and retrieving the packer to the tubing string from the well.

In FIG. 1 schematically shows the proposed method of hydraulic fracturing in the well.

In FIG. 2 schematically depicts a remote element A of a jet pump during hydraulic fracturing.

In FIG. 3 schematically shows the remote element A of the jet pump during the development of the formation.

The proposed method of hydraulic fracturing in a well is implemented as follows.

The hydraulic fracturing method in well 1 includes perforation of the walls of the well 1 by channels 2 with a depth not less than the extent of the stress concentration zone in the rocks from the wellbore 1 by any known method, for example, as described in patent RU No. 2358100, IPC ЕВВ 43/26, publ. in bull. No.16 of 06/10/2009

At the wellhead 1, a pipe string 3, for example a tubing string, with an outer diameter of 73 mm, above the packer 4 at a distance of 10 m, is equipped with a jet pump 5 from the outside.

The pipe string 3 is lowered with the packer 4 and the jet pump 5 so that the packer is 5-10 m above the roof 6 'of the formation 6 to be fractured, and the lower end of the pipe string 3 is located at the level of the roof 6' of the formation 6.

Then, packer 4 of any known design is planted, for example, a packer with anchor with mechanical rotary installation PRO-YaM2-YaG1 (F) or PRO-YaM3-YaG2 (F) (per 100 MPa).

Thus, annular space 7 of the well 1 is sealed in order to protect the walls of the well from the effects of high pressures arising during hydraulic fracturing.

A string of flexible pipes — GT 8 — is lowered into the pipe string 3 so that the lower end of the GT string 8 is lower than the end of the pipe string 3 and in the middle of the formation 6.

For example, at the height of the perforation interval N = 5 m, the middle of the formation 6 is the value N / 2 = 5/2 = 2.5 m.

Thus, the lower end of the GT 8 column is 2.5 m below the end of the pipe string 3.

At the wellhead 1, using the wellhead stuffing box 9, the space is sealed between the pipe string 3 and the GT string 8. At the wellhead 1, the discharge lines of the pipe string 3 and the GT string 8 are equipped with valves 10 and 11, respectively.

Next, determine the total volume of the gelled fracturing fluid according to the following formula:

V = k

where V is the total volume of the gelled fracturing fluid, m ³ ;

k = 11-12 - transfer coefficient, m ³ / m, we take k = 12;

N - height of the interval of perforation of the formation 6, m

Substituting in the formula the values: V = k · H = 12 · 5 = 60 m ³ , the total volume of the gelled fracturing fluid is obtained.

As the gelled fracturing liquid, any known liquid is used, for example, a cross-linked gel, which is prepared by any known method, for example, as described in the application RU No. 2008136865, IPC S09K 8/512, publ. in bull. No. 8 dated March 20, 2010, with a density of 1100 kg / m ³ or a water-based gel, which is prepared on water-soluble polymers of various nature of any known composition, for example, see Process fluids for completion and repair of wells. OAO NPO Burenie. - Krasnodar, 2006. - C.118 Ryabokon S.A.).

Separate the total gelled fracturing fluid (V = 60 m ³⁾ into two equal parts (60m ^3/2) to 30 m ^3: the first part - a liquid gap volume V _g = 30 m ³ intended for the formation and development of cracks 12 in the reservoir 6, and the second part is a carrier fluid V _n = 30 m ³ intended for delivery of proppant to the crack 12 in order to fix the crack 12.

With the closed valve 10 and open valve 11, the first part is injected into the sub-packer zone in the GT 8 column — fracturing fluid in a volume of V _g = 30 m ³ and hydraulic fracturing pressure is created in the sub-packer zone, for example, pressure 28.0 MPa with a crack formation of 12 reservoir 6.

Next, fasten the cracks 12 in the formation 6 by injection of the second part - the carrier fluid in a volume of V _n = 30 m ³ with proppant. To do this, open valve 10, while a carrier fluid with a large fraction 16/40 mesh proppant is pumped through a GT 8 column, and a carrier fluid with a small fraction 20/40 mesh proppant is pumped through a pipe string 3, while pumping a carrier fluid with proppant smaller and larger fractions are produced simultaneously in a ratio of 1: 4.

In the process of hydraulic fracturing in the pipe string 3, the sleeve 13 (see Fig. 1 and 2) hydraulically hermetically seals the jet pump 5 from the flow of carrier fluid with proppant. As proppant use proppant shallow 20/40 mesh and large 16/40 mesh fractions manufactured in accordance with GOST R 51761-2005 “Aluminosilicate proppants. Technical conditions. "

Thus, taking into account a 1: 4 ratio, 30/5 · 4 = 24 m ³ carrier fluid with a proppant of a fine fraction of 20/40 mesh with a gradual stepwise increase in concentration is pumped into the pipe string 3 (see Fig. 1) with the valve 10 open starting from 600 to 900 kg / m ³ , for example, in three stages, i.e. 8 m ³ carrier fluid with proppant fine 20/40 mesh fraction with a concentration of 600 kg / m, 8 m ³ carrier fluid with proppant fine 20/40 mesh with a concentration of 750 kg / m ³ and 8 m ³ carrier fluid with proppant fine fraction 20/40 mesh with a concentration of 900 kg / m ³ .

At the same time, in GT 8 with open valve 11, 30/5 · 1 = 6 m ³ of carrier fluid with a proppant of a large fraction of 16/40 mesh is pumped with a gradual stepwise increase in concentration, starting from 600 to 900 kg / m ³ , for example, three steps, i.e. 2 m ³ carrier fluid with large proppant 20/40 mesh with a concentration of 600 kg / m ³ , 2 m ³ carrier fluid with large proppant 20/40 mesh with a concentration of 750 kg / m ³ and 2 m ³ carrier liquid with proppant coarse fraction 20/40 mesh with a concentration of 900 kg / m ³ .

The carrier fluid is injected with a large 16/40 mesh proppant and a fine 20/40 mesh fraction from the wellhead 1 at the same time through the pipe string 3 and GT 8 column, while mixing the carrier fluid with a large 16/40 mesh proppant and a small 20 / 40 mesh fraction occurs both at the bottom of well 1 and in fracture 12, which allows evenly distributed mixed proppant of small 20/40 mesh and large 16/40 mesh fractions along the entire length of fracture 12, which allows to increase the permeability of the formed fracture 12 , provides removal of decomposed as a result Tate fracturing waste gelled fracturing fluids and the influx of formation fluid downhole.

Due to the uniform distribution of the mixed proppant of large 16/40 mesh and small 20/40 mesh fractions in the fracture 12, in case of destruction of the proppant of the large fraction, the closure of the fracture 12 is excluded due to the presence of the fine proppant 20/40 mesh, which allows to increase the efficiency of hydraulic fracturing and maintain oil recovery 6 during its subsequent operation.

The use of the same type of gelled fracturing fluid as a fracturing fluid and a carrier fluid can reduce the duration of the hydraulic fracturing process.

After completion of the injection of the carrier fluid with the proppant, the well 1 is kept for pressure relief, for example, for 40 minutes. Depressurization is made at the wellhead 1 of the space between the pipe string 3 and the GT string 8 (the wellhead stuffing box 9 is dismantled).

At the wellhead 1, between the pipe columns 3 and GT 8, a sealing ring insert 14 is installed (see Figs. 2 and 3) and is pressed through the pipe string 3, creating an overpressure in the pipe string 3 above the sealing ring insert 14 using a pump unit while the sealing ring insert 14 in the pipe string 3 destroys the shear element 15 and pushes the sleeve 13 down to the stop 15 '. Thus, the sealing ring insert 14 seals the inner space of the pipe string 3 (see FIG. 3) into a high pressure chamber 16 hydraulically connected to the jet pump 5 by means of a radial hole 17 of the pipe string 3 and a low pressure chamber 18 hydraulically connected to the jet the pump 5 through the through hole 19, the pipe string 3 and the through grooves 20 of the sleeve 13.

Next, a technological fluid is pumped into the pipe string 3 using a pump unit, for example, wastewater with a density of 1100 kg / m ³ , which through the radial hole 17 of the pipe string 3 enters the nozzle 21 of the jet pump 5, where the potential energy is converted into kinetic energy. The jet of process fluid flowing out of the nozzle 21 reduces the pressure in the low-pressure chamber 18. As a result, from the bottom-hole zone of the formation, liquid decomposed flows from the bottom-hole pump 5 from the low-pressure chamber 18 through the through hole 19 of the pipe string 3 and the through slots 20 of the sleeve 13 hydraulic fracturing spent gel, which is mixed with a stream of process fluid and enters the mixing chamber 22 of the jet pump 5.

In turn, the fluid with the spent gel decomposed during hydraulic fracturing enters the low-pressure chamber 18 (see Figs. 1 and 3) from the bottom-hole formation zone through channels 2 of well 1. Thus, the decomposition of the decomposed gel from the bottom-hole zone of the formation occurs continuously .

In the mixing chamber 22 (see Fig. 3) of the jet pump 5, the liquid with the decomposed gel and the process liquid are mixed, their speed and pressure are equalized, and the mixed stream enters the diffuser 23 of the jet pump 5.

In the diffuser 23 of the jet pump 5 there is a gradual decrease in the kinetic energy of the mixed stream and an increase in its potential energy.

At the exit from the jet pump 5 to the annular space 7 of the well 1, the mixed stream has the potential energy sufficient to rise along the pipe string 3 at the wellhead 1, from where the mixed liquid flow is directed into the grooved tank (not shown in Figs. 1, 2, 3) . The development of the well 1 (see Fig. 1 and 3) by forcing the bottom-hole zone of the formation 6 by means of a jet pump 5 after hydraulic fracturing is continued until the influx of oil. At the end of reservoir development, the GT 8 column is removed from the pipe string 3, the packer 4 with the pipe string 3 is unpacked and removed from the well 1. Simultaneous descent of the packer 4 and the jet pump 5 on the pipe string 3 before hydraulic fracturing allows development wells, which eliminates additional technological operations for raising and lowering the pipe string in order to develop the well, which simplifies the implementation of the method. Gentle development of the formation 6 using the jet pump 5 eliminates the destruction and removal of the injected proppant from the fracture in the bottom-hole zone of the formation to the bottom of the well 1.

The proposed method of hydraulic fracturing in a well allows to increase the permeability of a fixed fracture, as well as to increase the efficiency of hydraulic fracturing due to the uniform distribution (fastening) of large and small fractions of proppant mixed directly on the bottom of the well and in the fracture, to simplify and reduce the duration of the process the implementation of hydraulic fracturing through the use of the same type of gelled fluid and the combination of technological operations for hydraulic fracturing and reservoir development, and that also exclude the destruction and removal of the injected proppant from the fracture in the bottomhole formation zone to the bottom of the well by developing the formation using a jet pump.

Claims (1)

A method of hydraulic fracturing in a well, including perforation of the walls of the well in the interval of the channels with channels of depth not less than the length of the stress concentration zone in the rocks from the wellbore, lowering the pipe string with a packer so that the lower end of the pipe string is at the level of the roof of the formation, landing the packer over the roof perforated formation, determination of the total volume of the gelled fracturing fluid before hydraulic fracturing - hydraulic fracturing, injection into the sub-packer zone of the gelled fracturing fluid, creation in the sub-packer hydraulic fracturing pressure zone and formation of cracks in the formation with their subsequent fixing in the formation by injection of carrier fluid with proppant, holding the well for pressure relief, unpacking and removing the packer with the pipe string from the well, characterized in that the pipe string is higher at the wellhead packers at a distance of 10 m from the outside are equipped with a jet pump, then the pipe string is lowered into the well and the packer is planted over the roof of the perforated formation, then the flexible pipe string is lowered into the pipe string - GT t so that the lower end of the HT string is located below the end of the pipe string and in the middle of the formation, the space between the pipe string and the HT string is sealed at the wellhead, the total volume of the gelled fracturing fluid is determined, the total volume of the gelled fracturing fluid is divided into two equal parts: the first part is the fluid the fracture, the second part is the carrier fluid, the first part, the fracture fluid, is injected into the sub-packer zone through the GT column and the fracture pressure is generated in the sub-packer zone with formation of cracks in the reservoir, then The cracks in the formation are fixed by injection of the second part of the carrier fluid with proppant, and proppant of smaller and larger fractions is used as proppant, the carrier fluid with proppant of the fine fraction of 20/40 mesh and large fraction of 16/40 mesh are injected simultaneously in a ratio of 4: 1, whereby a carrier fluid with a large fraction proppant is pumped through a GT column, and a carrier fluid with a small fraction proppant is pumped through a pipe string, with a stepwise increase in the concentration of fine and large fraction proppant in a nose fluid the body, withstand the pressure relief hole, depressurizes the space between the pipe string and the GT string at the wellhead, a sealing ring insert is installed between the pipe columns and the GT and presses it through the pipe string under excessive pressure until the pipe string is hydraulically connected to the jet pump, make the development of the formation through the jet pump, at the end of the development of the formation remove the GT column from the pipe string, unpack and extract the packer from the columns second tubes from the borehole.

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