RU2522366C1 - Method of hydraulic fracturing of well formation - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method includes perforation in the formation interval, running in of a pipe string with a packer, setting of the packer, injection of a gelled fracturing fluid to the below-packer zone, filling of the pipe string with a process fluid, determination of the total volume of the gelled fracturing fluid, creation of a hydraulic fracturing pressure in the below-packer zone and flushing of the gelled fracturing fluid with a proppant to the formed fracturing, withhold during the time required for the pressure drop per 70%, the packer releasing and the packer removal with the pipe string from the well. Upon determination of its total volume the gelled fracturing fluid (linear gel) is injected to the well until hydraulic fracturing is formed in the formation, while the remaining volume of the gelled fracturing fluid upon hydraulic fracturing is divided into two parts - a cross-linked gel and a linear gel, cyclic injection of the linear gel at first and then of the cross-linked gel is made with addition of the proppant during 3-5 cycles. At that the linear gel is injected by equal portions with a flow rate of 4-6 m³/min and the proppant concentration of 400 kg/m³, while the cross-linked gel is injected with increasing volume from 3 up to 7 m³ with a flow rate of 1-2 m³/min and the proppant concentration of 1200 kg/m³. At that fibreglass in a quantity of 1.5% of the proppant weight is added to the last portions of the linear and cross-linked gel with the proppant.

EFFECT: improving efficiency of hydraulic fracturing.

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Description

The invention relates to the oil and gas industry and can be used to increase the productivity of production and injection wells.

A known method of hydraulic fracturing in a well (patent RU No. 2358100, IPC ЕВВ 43/26, published on June 10, 2009), which includes perforation of the walls of the well with channels of at least a depth of the stress concentration zone in the rocks from the wellbore of an existing well and injection into the well gel-like fracturing fluid "Himeko" in portions: the first - in the amount of 3-8 m ³ ; the second - in a volume of 10-12 m ³ and with a crack crack fastener; the third - in a volume of 2-3 m ³ , after which the portions of gel-like liquid are forced into the reservoir with a flow rate of 0.5-1 m ³ / min.

The disadvantages of this method are:

- firstly, a small radius of well drainage, since in the first portion only 3-8 m ^{3 of} gel-like fracturing fluid is pumped, therefore, when pumping further portions of gel-like fracturing fluid with proppant, it is impossible to push the proppant deeper than the already formed reservoir fracture (develop a fracture), except in addition, a gel-like Himeko fracture liquid with one dynamic viscosity and crack fixer of one fraction is used;

- secondly, the uneven distribution of proppant in the formation fracture, which occurs due to the fact that the crack propagator is added only when a second portion of the gel-like fracturing fluid is injected in a volume of 10-12 m ³ , which is then pressed into the formation, therefore, the proppant is concentrated mainly only in a certain zone of the reservoir fracture, i.e. in the zone of the fracture of the formation where proppant was sold;

- thirdly, the low efficiency of hydraulic fracturing (Fracturing) due to uneven consolidation of the cracks in the reservoir, i.e. a crack during subsequent operation of a production or injection well closes in a short period of time, which leads to a decrease in the productivity of production and injection wells.

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, lowering the pipe string with the packer, packing the packer over the roof of the perforated reservoir, injecting the gelled fracturing fluid into the sub-packer zone, creating hydraulic fracturing pressure in the sub-packer zone and pushing into the resulting I crack the reservoir of gelled fracturing fluid with proppant, and before hydraulic fracturing - hydraulic fracturing, the pipe string is filled with process fluid and the total volume of gelled fracturing fluid is determined 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 of 150-200 cPa 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 crosslinked gel is pumped in equal portions in 3-5 cycles with the addition of a proppant fraction of 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 increasing 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 up to 2.5-3 m ³ / min, pumped in equal portions in 3-5 cycles, the fracturing fluid is a linear gel with a dynamic viscosity of 30-50 cPa with the addition of a proppant fraction of 20-40 mesh. 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 injected into the pipe string, they are pumped into the formation with process fluid, while during the process of pumping they reduce the flow of process fluid to 0.5 -1 m ³ / min for 1-3 minutes and resume pumping again with a flow rate of 2.5-3 m ³ / min until the linear gel with proppant is fully injected into the formation, after which exposure is performed for the time required for the injection pressure to drop 70-80%, unpack the packer and remove him with a string of pipes from the well.

The disadvantages of this method are:

- firstly, the insufficient efficiency of hydraulic fracturing due to the fact that a gradual increase in proppant concentration with various fractions leads to the fact that “proppant fractions are pressed in” as between themselves, which worsens the conductivity of the fracture and in the fractures adjacent to the surface, those. proppant grains are introduced into the rock, thereby reducing the effective opening of cracks, this is especially manifested in loose rocks;

- secondly, poor-quality crack attachment in the formation, due to the fact that the creation of long fracture cracks in the formation with their subsequent successive attachment by proppant of various fractions leads to a long duration of the process of closing cracks filled with proppant, due to compaction of proppant grains and sedimentation of small fractions in the lower parts of the cracks, which increases the likelihood of the formation of local channels, or "pockets", in proppant packing with low stress compressing the crack, which facilitates the proppant removal and mining;

- thirdly, during the operation of the well in the borehole zone, shear movements of proppant fractions occur with each other with their destruction, which reduces the conductivity of the fracture in the borehole zone;

- fourthly, the use of a crosslinked gel as a hydraulic fracturing fluid increases the hydraulic resistance, while the cracks are short and wide, which limits their use in highly permeable formations, especially when located near aquifers and interlayers;

fifthly, according to the method, the hydraulic fracturing of the formation is performed cyclically first, and then the formed cracks are cyclically fixed with proppant, while the final sections of the cracks have time to close by the time the proppant fills them, which reduces the throughput of fracture cracks.

The technical objectives of the invention are to increase the efficiency of hydraulic fracturing and the quality of the attachment of proppant by creating a structure that immobilizes proppant grains in the bottomhole formation zone, and, as a result, minimizing the proppant output into the wellbore, as well as eliminating proppant fracture in the borehole formation zone with the possibility the implementation of the method in highly permeable formations.

The stated technical problems are solved by the method of 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, the descent of the pipe string with the packer, the packer landing over the roof of the perforated reservoir, injection into the under-packer zone gelled fracturing fluid, filling the column with process fluid, determining the total volume of gelled fracturing fluid, creating in the under-packer zone hydraulic fracturing pressure and pushing the gelled fracturing fluid with proppant into the formed fracture of the formation, holding for the time required for pressure drop by 70%, unpacking and removing the packer from the pipe string from the well.

What is new is that after determining the total volume of the gelled fracture fluid, the gelled fracture fluid — a linear gel — is pumped into the well through the pipe string until fracture fractures form in the formation, the remaining volume of the fractured gel fluid after fracture formation in the reservoir is divided into two parts: crosslinked gel and a linear gel, then cyclically sequentially injected first a linear and then crosslinked gel with the addition of proppant in 3-5 cycles, the linear gel being pumped in equal portions with a flow rate of 4-6 m ³ / min and a proppant concentration of 400 kg / m ³ , and the cross-linked gel is pumped with a stepwise increase in injection volume from 3 to 7 m ³ with a flow rate of 1-2 m ³ / min and a proppant concentration of 1200 kg / m ³ , while in the last portions of the linear and crosslinked proppant gels add fiberglass in an amount of 1.5% by weight of proppant in each of the last portions of linear and crosslinked gels and pump them into the pipe string, then push them into the formation with process fluid and hold for the time required for the pressure to drop to 70%, unpack and heal packer with a pipe string from the well.

Figure 1 and 2 shows the process of implementing the method of hydraulic fracturing.

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

The method of hydraulic fracturing (Fracturing) in the well includes perforation of the walls of the well with channels of depth not less than the length of the zone of stress concentration in the rocks from the wellbore in any known manner, for example, as described in patent RU No. 2358100, IPC E21B 43/26, publ. 06/10/2009

Next, into the well, into the hydraulic fracturing zone, a pipe string is lowered, for example, tubing string 73 mm, with a packer so that the packer is 5-10 m above the top of formation 1 (see Fig. 1), which is subject to hydraulic fracturing, and the lower end of the pipe string is at the level of the formation 1 roof, after which the packer of any known design is planted, for example, a packer with an anchor with a mechanical rotary installation PRO-YaM2-YaG1 (F) or PRO-YaM3-YaG2 (F) (100 MPa ) production of the research and production company "Packer" (Oktyabrsky, Republic of Bashkortostan, Russian Federation Ia).

Thus, the annulus of the well is sealed in order to protect the walls of the well from the effects of high pressure that occurs during hydraulic fracturing.

Next, the pipe string is filled with process fluid, for example, waste water with a density of 1180 kg / m ³ , and the total volume of the gelled fracturing fluid is determined by the following formula:

V _g = k · N _p

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

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

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

In this formula, the conversion coefficient is obtained empirically and depends on the physicochemical properties of formation 1 in which hydraulic fracturing is performed.

For example, the height of the formation perforation interval is 6 m. Substituting V _g = k · N _p in the formula, we obtain the total volume of the gelled fracturing fluid:

V _g = 11 (m ³ / m) · 6 (m) = 66 m ³ .

Prepare a gelled fracturing liquid - a linear gel - in any known manner, for example, as described in patent RU No. 2381252, IPC S09K 8/68, publ. 02/10/2010

A gelled fracturing fluid — a linear gel — with a dynamic viscosity of, for example, 30 cP is pumped into the well through a string of pipes until fracture fractures form in the formation.

Linear gel is injected through perforation channels 2 with a flow rate of, for example, 4.0 m ³ / min until a rock is broken in formation 1 and a crack is formed in gap 3, which will be indicated by a drop in injection pressure and an increase in injectivity of formation 1. For example, when injecting a linear gel reached a pressure of 33 MPa, due to the formation of rupture crack 3, the injection pressure of the linear gel dropped by 30%, i.e. up to 23 MPa, while the injectivity of formation 1 increased by 15%, for example, from 4.5 to 5.2 m ³ / min.

The use of a linear gel (30 cP) as a rupture fluid in comparison with a crosslinked gel (150 cP) creates less resistance due to the relatively low viscosity. As a result of injecting a linear gel having a low dynamic viscosity (30 cP) with a high flow rate, long but narrow fracture cracks 3 are obtained, for example, 25 m long and 30 mm wide, which is effective in highly permeable formations when aquifers and interlayers are located near them.

In the process of the formation of a crack 3, a gel-like fracturing fluid was pumped into the formation 1 through a pipe string — a linear gel in a volume of, for example, 26 m ³ .

As a result, a gel-like liquid of discontinuity remains in the volume of 40 m ³ (V _g2 = V _g -V _g1 = 66-26 = 40 m ³ ). The remaining volume of the gelled fracturing fluid (40 m ³ ) is divided into two equal parts: a crosslinked gel and a linear gel.

Cyclicly, in 3-5 cycles, the portions of the linear gel are alternately pumped with the addition of proppant and the crosslinked gel with the addition of proppant. For example, proppant fractions of 20-40 mesh are used. in four cycles.

A gelled fracturing liquid — a crosslinked gel — is prepared in a volume of 20 m ³ with the addition of a borate crosslinker, for example, in a linear gel, or any known crosslinked gel is used, for example, see Chapter 3 of S. A. Monograph. Ryabokonya "Technological fluids for completion and repair of wells (OAO NPO Bureniye, 2006. P.153).

Use proppant fractions of 20-40 mesh., Which is manufactured according to GOST R 51761-2005 "Aluminosilicate proppants. Specifications ”and produced at the Borovichi Refractories Plant (Borovichi, Republic of Belarus).

The entire volume of a linear gel (20 m ³⁾ is injected in equal portions as indicated above, four cycles (4 ', 4 ", 4'", 4 '") (20 m ^3/4 = 5 m ^3), ie . 5 m ³ per serving with a flow rate of at least 4 m ³ / min, for example 4.5 m ³ / min and with a proppant concentration of 400 kg / m ³ .

When cyclic injection of a linear gel occurs, proppant fills the fracture of fracture 1 (see FIG. 1).

The volume of the crosslinked gel (20 m ³ ) is also pumped in four cycles (5 ', 5 ", 5'", 5 ""), but with a stepwise increase in the injection volume, for example, by 1 m ³ with a flow rate of 1.5-2 m ³ / min, for example with a flow rate of 1.7 m ³ / min and a proppant concentration of 1200 kg / m ³ .

The injection of a crosslinked gel is started, for example, from a volume of 3.5 m ³ , increasing the injection volume in each portion by 1.0 m ³ , i.e. 3.5 m ³ , 4.5 m ³ , 5.5 m ³ , 6.5 m ³ with a proppant concentration of 1200 kg / m ³ . For each cyclic injection of a crosslinked gel with proppant in the final section of a long and narrow fracture gap filled and sealed with proppant, when the latter is injected with linear gel, vertical cracks form (6 ', 6 ", 6'", 6 "") (see Fig. .2).

Before downloading the last, fourth, servings of a linear gel with proppant in a volume of 5 m ³ and cross-linked gel with a proppant in a volume of 6.5 m ³ they add fiberglass in an amount of 1.5% by weight of proppant in each of the last servings of a linear and crosslinked gel .

Fiberglass is used according to GOST 8325-93 "Fiberglass. Complex twisted threads. Specifications "or according to GOST 17139-2000" Fiberglass ".

Determine the amount of fiberglass that must be added to the last portion of a linear gel with a volume of 5 m ³ with a proppant concentration of 400 kg / m ³ :

400 kg / m ³ · 5 m ³ = 2000 kg, 2000 kg · 1.5% / 100% = 30 kg.

Thus, 30 kg of fiberglass is added to the last portion of the linear proppant gel before injection.

Determine the amount of fiberglass that must be added to the last portion of a cross-linked gel with a volume of 6.5 m ³ with a proppant concentration of 1200 kg / m ³ :

1200 kg / m ³ · 6.5 m ³ = 7800 kg, 7800 kg · 1.5% / 100% = 117 kg.

Thus, 117 kg of glass fiber is added to the last portion of the linear gel before injection.

After injecting the last portion of the crosslinked gel with a proppant of a concentration of 1200 kg / m ³ with the addition of fiberglass, it is forced into the formation with a process fluid with a density of, for example, 1180 kg / m ³ .

Glass fibers added in the last portions of proppant create a structure in the bottom-hole zone of the formation that immobilizes proppant grains and excludes their movement relative to each other and destruction, therefore, the throughput of a crack fixed by a proppant with the addition of fiberglass is much higher compared to conventional proppant, which is especially important in the near-wellbore zone of formation 1, this minimizes the proppant output into the wellbore during subsequent pressure relief and development of the well.

The volume of the process fluid, sufficient to fully sell the last portion of the crosslinked gel with proppant and fiberglass to the formation, corresponds to one and a half times the internal volume of the pipe string lowered into the well, for example 3.5 m ³ .

At the end of the process of selling the linear gel with the addition of proppant and crosslinked gel with the addition of proppant and fiberglass to the formation, the shutter speed is maintained for the time required for the injection pressure to drop by 70% for 30-60 minutes. For example, when selling the last portion of a crosslinked gel with proppant and fiberglass, the pressure value was 33 MPa.

33 MPa (33 · 70% / 100%) = 33 MPa-23 MPa = 10 MPa.

For 30 minutes, technological exposure is made until the pressure drops to 10.0 MPa, unpacking is performed and the packer with the pipe string is removed from the well.

Example 1

A 73 mm tubing string with a packer is lowered into the well, into the hydraulic fracturing zone, and the packer is planted 7 m above the formation roof.

The tubing string is filled with sewage with a density of 1180 kg / m ³ and the total volume of gelled fluid is determined at a height of the formation perforation interval of 5 m.

Substituting V _g = k · N _p in the formula, we obtain the total volume of the gelled fracturing fluid:

V _g = 11 (m ³ / m) · 5 (m) = 55 m ³ .

A gelled fracturing fluid — a linear gel — is pumped into the well through a pipe string until fracture fractures form in the formation.

The linear gel is injected through perforation channels 2 with a flow rate of 4.5 m ³ / min until a formation rock is fractured and a fracture crack is formed, which will be indicated by a drop in injection pressure and an increase in injectivity of the formation. When the linear gel was injected, the pressure reached 35 MPa, due to the formation of a rupture crack, the linear gel injection pressure decreased by 35%, i.e. up to 23 MPa, while the injectivity of the formation 1 increased by 25%, for example, from 4.5 to 5.4 m ³ / min.

In the process of crack 3 formation, a gel-like fracturing fluid — a linear gel in the volume of 25 m ³ — was pumped into the pipe 1 into the formation 1.

As a result, a gel-like rupture fluid remains in a volume of 30 m ³ (V _g2 = V _g -V _g1 = 55-25 = 30 m ³ ). The remaining volume of the gelled fracturing fluid (30 m ³ ) is divided into two equal parts: a crosslinked gel and a linear gel.

Cyclically (in 3 cycles), portions of a linear gel are sequentially injected with the addition of proppant and a cross-linked gel with the addition of a proppant fraction of 20-40 mesh in three cycles.

A gelled fracturing liquid is prepared — a crosslinked gel in a volume of 15 m ³ .

The entire volume of a linear gel (15 m ³⁾ is injected in equal portions, as outlined above, three cycles (15 m ³ / m 3 = 5, ^3), i.e. 5 m ³ per serving with a flow rate of 5 m ³ / min and a proppant concentration of 400 kg / m ³ .

The volume of cross-linked gel (15 m ³ ) is also pumped in three cycles with a stepwise increase in the injection volume, for example, by 2 m ³ , with a flow rate of 1.8 m ³ / min and a proppant concentration of 1200 kg / m ³ . The injection of crosslinked gel begins with a volume of 3.0 m ³ , increasing the volume of injection in each portion by 1 m ³ , i.e. 3.0 m ³ , 5.0 m ³ , 7.0 m ³ with a proppant concentration of 1200 kg / m ³ .

Before downloading the last, third, portion of a linear gel with proppant in a volume of 5 m ³ and a cross-linked gel with proppant in a volume of 7.0 m ³ they add fiberglass in an amount of 1.5% by weight of proppant in each of the last portions of linear and crosslinked gels .

Determine the amount of fiberglass that must be added to the last portion of a linear gel with a volume of 5 m ³ with a proppant concentration of 400 kg / m ³ :

400 kg / m ³ · 5 m ³ = 2000 kg, 2000 kg · 1.5% / 100% = 30 kg.

Thus, 30 kg of fiberglass is added to the last portion of the linear proppant gel before injection.

Determine the amount of fiberglass that must be added to the last portion of a cross-linked gel with a volume of 6.5 m ³ with a proppant concentration of 1200 kg / m ³ :

1200 kg / m ³ · 7.0 m ³ = 8400 kg, 8400 kg · 1.5% / 100% = 126 kg.

Thus, before the injection into the last portion of the linear gel, add 126 kg of fiberglass. After injecting the last portion of a cross-linked gel with a proppant of a concentration of 1200 kg / m ³ with the addition of fiberglass, it is forced into the reservoir with a process fluid with a density of 1180 kg / m ³ in a volume of 3.0 m ³ .

Excerpt for the time required for the drop in injection pressure by 70%. When selling the last portion of a crosslinked gel with proppant and fiberglass, the pressure value is 30 MPa.

30 MPa (30 MPa · 70% / 100%) = 30 MPa-21 MPa = 9 MPa.

Within 50 minutes produce technological exposure until the pressure drops to 9.0 MPa, perform unpacking and remove the packer from the pipe string from the well.

Example 2

A 73 mm tubing string with a packer is lowered into the well, into the hydraulic fracturing zone, and the packer is planted 7 m above the formation roof.

The tubing string is filled with sewage with a density of 1180 kg / m ³ and the total volume of gelled fluid is determined at a height of the formation perforation interval of 4 m.

Substituting V _g = k · N _p in the formula, we obtain the total volume of the gelled fracturing fluid:

V _g = 11 (m ³ / m) 7 (m) = 77 m ³ .

A gelled fracturing fluid — a linear gel — is pumped into the well through a pipe string until fracture fractures form in the formation.

The linear gel is injected through perforation channels 2 with a flow rate of 4.5 m ³ / min until a formation rock is fractured and a fracture crack is formed, which will be indicated by a drop in injection pressure and an increase in injectivity of the formation. When the linear gel was injected, the pressure reached 35 MPa, due to the formation of a rupture crack, the linear gel injection pressure decreased by 35%, i.e. up to 23 MPa, while the injectivity of the formation 1 increased by 25%, for example, from 4.5 to 5.4 m ³ / min.

In the process of crack 3 formation, a gel-like fracturing fluid — a linear gel in the volume of 25 m ³ — was pumped into the pipe 1 into the formation 1.

As a result, a gel-like rupture fluid remains in a volume of 50 m ³ (V _g2 = V _g -V _g1 = 77-27 = 50 m ³ ). The remaining volume of the gelled fracturing fluid (50 m ³ ) is divided into two equal parts: a crosslinked gel and a linear gel.

Cyclic (in 5 cycles), alternately pumping portions of a linear gel with the addition of proppant and cross-linked gel with the addition of proppant fractions of 20-40 mesh. in five cycles.

A gelled fracturing liquid is prepared — a crosslinked gel in a volume of 15 m ³ .

The entire volume of a linear gel (25 m ³⁾ is injected in equal portions, as outlined above, five cycles (25 m ^3/5 = 5 m ^3), i.e. 5 m ³ per serving with a flow rate of 6 m ³ / min and a proppant concentration of 400 kg / m ³ .

The volume of the crosslinked gel (25 m ³ ) is also pumped in five cycles with a stepwise increase in the injection volume with a flow rate of 2.0 m ³ / min and a proppant concentration of 1200 kg / m ³ . The injection of the crosslinked gel begins with a volume of 3.0 m ³ , increasing the volume of injection in each portion by 1.0 m ³ , i.e. 3.0 m ³ , 4.0 m ³ , 5.0 m ³ , 6.0 m ³ , 7.0 m ³ , with a proppant concentration of 1200 kg / m ³ .

Before downloading the last, fifth, servings of a linear gel with proppant in a volume of 5 m ³ and a cross-linked gel with proppant in a volume of 7.0 m ³ they add fiberglass in the amount of 1.5% by weight of proppant in each of the last servings of linear and crosslinked gels .

Determine the amount of fiberglass that must be added to the last portion of a linear gel with a volume of 5 m ³ with a proppant concentration of 400 kg / m ³ :

400 kg / m ³ · 5 m ³ = 2000 kg, 2000 kg · 1.5% / 100% = 30 kg.

Thus, 30 kg of fiberglass is added to the last portion of the linear proppant gel before injection.

Determine the amount of fiberglass that must be added to the last portion of a cross-linked gel with a volume of 6.5 m ³ with a proppant concentration of 1200 kg / m ³ :

1200 kg / m ³ · 7.0 m ³ = 8400 kg, 8400 kg · 1.5% / 100% = 126 kg.

Thus, before the injection into the last portion of the linear gel, add 126 kg of fiberglass.

After injecting the last portion of the cross-linked gel with a proppant of a concentration of 1200 kg / m ³ with the addition of fiberglass, it is forced into the reservoir with a process fluid with a density of 1180 kg / m ³ in a volume of 4.5 m ³ .

Excerpt for the time required for the drop in injection pressure by 70%. When selling the last portion of a crosslinked gel with proppant and fiberglass, the pressure value is 30 MPa.

30 MPa (30 MPa · 70% / 100%) = 30 MPa-21 MPa = 9 MPa.

For 50 min, technological exposure is made until the pressure drops to 9.0 MPa, unpacking is performed and the packer with the pipe string is removed from the well.

Example 3

A 73 mm tubing string with a packer is lowered into the well, into the hydraulic fracturing zone, and the packer is planted 7 m above the formation roof.

The tubing string is filled with sewage with a density of 1180 kg / m ³ and the total volume of gelled fluid is determined at a height of the formation perforation interval of 4 m.

Substituting V _g = k · N _p in the formula, we obtain the total volume of the gelled fracturing fluid:

V _g = 11 (m ³ / m) · 4 (m) = 44 m ³ .

A gelled fracturing fluid — a linear gel — is pumped into the well through a pipe string until fracture fractures form in the formation.

The linear gel is injected through perforation channels 2 with a flow rate of 4.5 m ³ / min until a formation rock is fractured and a fracture crack is formed, which will be indicated by a drop in injection pressure and an increase in injectivity of the formation. When the linear gel was injected, the pressure reached 35 MPa, due to the formation of a rupture crack, the linear gel injection pressure decreased by 35%, i.e. up to 23 MPa, while the injectivity of the formation 1 increased by 25%, for example, from 4.5 to 5.4 m ³ / min.

In the process of crack 3 formation, a gel-like fracturing fluid — a linear gel in the volume of 25 m ³ — was pumped into the pipe 1 into the formation 1. As a result, a gel-like rupture fluid remains in the volume of 32 m ³ (V _g2 = V _g -V _g1 = 44 m ³ -12 m ³ = 32 m ³ ). The remaining volume of the gelled fracturing fluid (32 m ³ ) is divided into two equal parts: a crosslinked gel and a linear gel.

Cyclicly, in 4 cycles, the portions of a linear gel are sequentially injected with the addition of proppant and a crosslinked gel with the addition of a proppant fraction, 20-40 mesh. in four cycles.

A gelled fracturing liquid is prepared — a crosslinked gel in a volume of 16 m ³ .

The entire volume of a linear gel (16 m ³⁾ is injected in equal portions as indicated above, four cycles (16 m ^3/4 = 4 m ^3), i.e. 4 m ³ per serving with a flow rate of 4 m ³ / min and a proppant concentration of 400 kg / m ³ . The volume of crosslinked gel (16 m ³ ) is also pumped in four cycles with a stepwise increase in the volume of injection with a flow rate of 1.5 m ³ / min and a proppant concentration of 1200 kg / m ³ . The injection of crosslinked gel begins with a volume of 3.0 m ³ , increasing the volume of injection in each portion by 0.5 m ³ , i.e. 3.25 m ³ , 3.75 m ³ , 4.25 m ³ , 4.75 m ³ , with a proppant concentration of 1200 kg / m ³ .

Before downloading the last, fourth, servings of a linear gel with proppant in a volume of 4 m ³ and a cross-linked gel with proppant in a volume of 4.75 m ³ they add fiberglass in the amount of 1.5% by weight of proppant in each of the last servings of linear and cross-linked gels .

Determine the amount of fiberglass that must be added to the last portion of a linear gel with a volume of 4 m ³ with a proppant concentration of 400 kg / m ³ :

400 kg / m ³ · 4 m ³ = 1600 kg, 1600 kg · 1.5% / 100% = 24 kg.

Thus, prior to injection, 24 kg of glass fiber is added to the last portion of the proppant linear gel. Determine the amount of fiberglass that must be added to the last portion of the crosslinked gel with a volume of 4.75 m ³ with a proppant concentration of 1200 kg / m ³ :

1200 kg / m ³ · 4.75 m ³ = 5700 kg, 5700 kg · 1.5% / 100% = 85.5 kg.

Thus, 85.5 kg of fiberglass is added to the last portion of the linear gel before injection.

After injecting the last portion of the cross-linked gel with a proppant of a concentration of 1200 kg / m ³ with the addition of fiberglass, it is forced into the reservoir with a process fluid with a density of 1180 kg / m ³ in a volume of 4.5 m ³ .

Excerpt for the time required for the drop in injection pressure by 70%. When selling the last portion of a crosslinked gel with proppant and fiberglass, the pressure value is 30 MPa.

30 MPa (30 MPa · 70% / 100%) = 30 MPa-21 MPa = 9 MPa.

For 50 min, technological exposure is made until the pressure drops to 9.0 MPa, unpacking is performed and the packer with the pipe string is removed from the well.

The proposed method allows to increase the efficiency of hydraulic fracturing, the quality of the attachment of the proppant by creating a structure that immobilizes proppant grains in the bottomhole formation zone, and, as a result, minimizes the proppant output into the wellbore, and also eliminates proppant fracture in the borehole formation zone when implementing the method in highly permeable formations.

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 at least the length of the stress concentration zone in the rocks from the wellbore, lowering the pipe string with the packer, packing the packer over the roof of the perforated productive formation, injecting gelled fracturing fluid into the sub-packer zone, filling the column with process fluid, determining the total volume of the gelled fracturing fluid, creating a fracturing pressure in the sub-packer zone and squeezing a developed fracture of the gelled fracturing fluid bed with proppant, holding for the time required for the pressure to drop by 70%, unpacking and removing the packer from the pipe string from the well, characterized in that after determining the total volume of the gelated fracturing fluid, the gelled pipe is pumped into the well fracturing fluid — linear gel — before the formation of fracturing fractures in the formation, the remaining volume of the gelled fracturing fluid after the formation of fracturing fractures in the reservoir is divided into two parts: a crosslinked gel and a line gel, then cyclically make a sequential injection of first linear and then crosslinked gel with the addition of proppant in 3-5 cycles, and the linear gel is pumped in equal portions with a flow rate of 4-6 m ³ / min and a proppant concentration of 400 kg / m ³ , and crosslinked the gel is pumped with a stepwise increase in injection volume from 3 to 7 m ³ with a flow rate of 1-2 m ³ / min and a proppant concentration of 1200 kg / m ³ , while 1.5% glass fiber is added to the last portions of linear and crosslinked gels with proppant in an amount of 1.5% by proppant weight in each of the last servings of linear and s total gels and pump them into the pipe string, then push them into the formation with process fluid and hold for the time required to drop the pressure by 70%, unpack and extract the packer from the pipe string from the well.

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