RU2541693C1 - Method for formation hydraulic fracturing in horizontal open well shaft - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: method involves drilling of a horizontal well, lowering to a vertical part of the well of a casing string and its cementing, lowering of a pipe string with a packer to a well, seating of the packer, formation of fractures of formation hydraulic fracturing (FHF) in the horizontal well shaft by pumping via the pipe string of fracturing fluid, and fixation of fractures by pumping of carrier fluid with proppant. The horizontal shaft is drilled perpendicular to direction of minimum main stress. FHF is performed by pumping of fracturing fluid with flow rate of 2-3 m³/min with formation of a longitudinal fracture in the formation relative to the open horizontal part of the well; crosslinked gel is used as fracturing fluid; then, fixation of a longitudinal fracture is performed by pumping via the pipe string of proppant of large fraction with carrier fluid - crosslinked gel. Then, FHF is performed by pumping of fracturing fluid with flow rate of 7-9 m³/min; line gel is used as fracturing fluid; after that, fixation of branched FHF fractures is performed by pumping of proppant of small fraction with carrier fluid - line gel.

EFFECT: improving FHF efficiency and reliability.

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Description

The invention relates to the oil and gas industry, in particular to a method for hydraulic fracturing in an open horizontal wellbore that has opened productive formations with low reservoir-filtering capacitive properties.

A known method of multiple hydraulic fracturing in a horizontal wellbore (patent RU No. 2472926, IPC EV 43/267, publ. 01.20.2013, bull. No. 2), including the descent of the packer into the well on the pipe string, followed by its landing in the well, the formation of cracks in front of the filters sequentially at different intervals of the reservoir, opened by a horizontal well by supplying hydraulic fracturing fluid through a filter installed in each of the parts of the horizontal well corresponding to each of these intervals with isolation of the rest of it parts, in this case, determine the direction of the horizontal trunk relative to the direction of the minimum main stress, then isolate the interval subject to hydraulic fracturing - hydraulic fracturing - from the remaining sections of the horizontal trunk by planting twin packers, then open the valve located inside the pipe string between the twin packers opposite the filter, if the direction horizontal trunk parallel to the direction of the minimum principal stress, the hydraulic fracturing is performed by pumping a burst bones with the formation of transverse cracks relative to the horizontal wellbore, followed by the fastening of transverse cracks by injection of fluid with aluminosilicate proppant, with a gradual increase in its fraction from 20/40 to 16/30 mesh, if the direction of the horizontal trunk is perpendicular to the direction of the minimum principal stress, then hydraulic fracturing is performed injection of explosive fluid with the formation of horizontal cracks relative to the horizontal trunk, followed by fastening of horizontal cracks by injection of fluid with a lightweight proppant with a fraction of 20/40 mesh, at the end of the hydraulic fracturing, the well is closed for a technological pause for 0.5 h, after which an adjustable nozzle is installed on the wellhead at the wellhead and the spent proppant fluid is poured from the formation along the wellhead pipe string wells before closing the valve, while during the spout by adjusting the nozzle, they ensure that the pressure in the pipe string is 2-3 MPa less than the pressure when opening the well after a technological pause, after which the packer is unpacked and they move the pipe string to another part of the horizontal wellbore, and the above hydraulic fracturing process in the horizontal wellbore is repeated depending on the number of horizontal wellbore intervals equipped with filters in its various parts.

The disadvantages of the method are:

- firstly, the low efficiency of the implementation of the method in a reservoir with low reservoir filtration and reservoir properties, which is due to the weak attachment of proppant in longitudinal and transverse fractures formed from a horizontal wellbore, therefore, during subsequent production from transverse and especially longitudinal fractures formed in in a productive formation with low reservoir-filtration-reservoir properties, proppant grains will enter the horizontal wellbore, which will lead to the closure of fractures and To reduce the bandwidth of the formation of cracks in the near-wellbore zone;

- secondly, the long duration of the hydraulic fracturing associated with the need to fasten the casing (liner) in the horizontal wellbore, as well as hydromechanical slotted perforation of the casing (liner) and subsequent hydraulic fracturing in the horizontal wellbore with each packer cutting off interval during hydraulic fracturing;

- thirdly, high material and financial costs for the implementation of the method associated with the casing of a horizontal trunk by a casing string (liner) followed by its cementing;

- fourthly, low reliability due to the high likelihood of mudding of the reservoir during cementing of the casing (liner) in the horizontal wellbore, as well as the high probability of failure of dual packers in operation, due to possible complications when planting packers and unpacking in each interval of the horizontal wellbore wells. In addition, with a dual packer design, it is almost impossible to ensure the tightness of both packers at high pressures (up to 40 MPa) during hydraulic fracturing.

A known method of hydraulic fracturing in a horizontal wellbore (patent RU No. 2401942, IPC ЕВВ 43/26, publ. 10/20/2010, bull. No. 29), including drilling a well, cementing a horizontal wellbore, lowering a pipe string with a packer into the well, perforation and the formation of hydraulic fractures by injection of fracturing fluid in the horizontal wellbore sequentially, starting from the end farthest from the axis of the vertical wellbore, communicating the horizontal wellbore with the productive formation, while of hydraulic fracturing, each perforated section through which hydraulic fracturing is performed is isolated from the rest of the string by packers, while drilling the horizontal wellbore is carried out in the oil-saturated part of the producing formation by cementing the annulus between the casing and rock of the horizontal wellbore, and the perforation azimuthally oriented intervals, produced using a hydromechanical slotted perforator for one trip then the packers are lowered, cutting off each interval equal to the length of the formed gap from the rest of the column, and hydraulic fracturing in the horizontal part of the wellbore is carried out sequentially, starting from the far from the axis of the vertical wellbore of the perforated section of the horizontal wellbore, with hydromechanical slotted perforation perform bilateral on the formation of slots, which are located relative to each other 180 ° in a vertical plane opposite each other, relative to the axis of the horizon of the borehole in one interval, or perform one-sided hydromechanical slotted perforation with a rotation of 180 ° in the vertical plane relative to the axis of the horizontal wellbore, alternately through each subsequent interval in a checkerboard pattern equal to the length of the formed gap, or with a small thickness of the reservoir and the presence of active plantar water produce one-way hydromechanical slotted perforation in the direction of the formation roof.

The disadvantages of this method are:

- firstly, the low efficiency of the implementation of the method in a reservoir with low reservoir filtration and reservoir properties due to the absence of crack attachment, which leads to the closure of the cracks and a sharp decrease in the throughput of the formation cracks in the near-wellbore zone;

- secondly, low reliability due to the high likelihood of mudding of the reservoir during cementing of the casing (liner) in the horizontal wellbore, as well as problems with cutting off hydraulic fracturing intervals with the use of packers, namely: emergencies in the well associated with the risk of leakage packer landing, packer sliding along the horizontal wellbore, possible loss of packer tightness at high pressures (up to 40 MPa);

- thirdly, the long duration of hydraulic fracturing associated with the need to fasten the casing (liner) in the horizontal wellbore, as well as hydromechanical slotted perforation of the casing (liner) and subsequent hydraulic interval fracturing in the horizontal wellbore with each packer cutting off interval during hydraulic fracturing;

- fourthly, the high material and financial costs of implementing the method associated with planting a horizontal shaft with a liner and its subsequent cementing.

The closest in technical essence is the way to create a network of cracks in the rock formation for the extraction of hydrocarbons from the formation (patent WO 2012083463 A1, IPC ЕВВ 43/267 of 12/22/2011), including drilling a horizontal well, lowering the casing into the vertical part of the well and cementing it , descent of the pipe string with the packer into the well, interval packer landing and the formation of a network of natural and emerging cracks in the formation (formation) by injecting an aqueous solution without sludge (fracturing fluid) into the well through the pipe string and and conditions suitable for the expansion, displacement and (or) hydraulic connection of natural cracks, with the formation of a large network of cracks, which is in hydraulic communication with an enlarged network of natural cracks, injection of many suspensions containing a carrier fluid (carrier fluid) and large granular proppants (proppant) into the well with a series of injections (interval).

The disadvantages of this method are:

- firstly, the low efficiency of the implementation of the method in a reservoir with low reservoir filtration and reservoir properties, due to the attachment of cracks by a large proppant, which leads to their rapid removal into the horizontal well almost immediately after the start of operation of the well and, as a result, to the closure of the cracks and a sharp decrease in the permeability (throughput) of formation cracks in the near-wellbore zone;

- secondly, low reliability due to problems when cutting fracturing intervals by packers, namely: the occurrence of emergency situations in the well associated with the risk of leaky packer landing, a possible loss of tightness of the packer at high pressures (up to 40 MPa);

- thirdly, the long duration of hydraulic fracturing associated with conducting interval hydraulic fracturing in an open horizontal wellbore with a packer cutting off each interval during hydraulic fracturing;

- fourthly, high material and financial costs for the implementation of the method associated with the long duration of the implementation of the method.

The technical objectives of the proposal are to increase the efficiency of hydraulic fracturing by first creating longitudinal fractures from a horizontal wellbore and then from a network of branched fractures from the longitudinal cracks, followed by filling the proppant with different fractions in the fractures, which minimizes proppant transfer to the horizontal wellbore during subsequent well operation, thereby eliminating closure of cracks and maintain permeability in the near-wellbore zone, as well as increased reliability by eliminating clipping of each inte tore hydraulic fracturing by packers, reducing the duration of hydraulic fracturing and reducing material and financial costs for implementing the method.

The stated technical problems are solved by the method of hydraulic fracturing in an open horizontal wellbore, including drilling a horizontal well, lowering the casing into the vertical part of the well and cementing it, lowering the pipe string with the packer into the well, packing the packer, forming hydraulic fracturing in the horizontal wellbore pumping fracture fluid over a string of pipes; fixing cracks by pumping a carrier fluid with proppant.

What is new is that the horizontal wellbore is drilled in the formation perpendicular to the direction of the minimum principal stress, the pipe string with the packer is lowered into the well and the packer is planted in the vertical part of the well, hydraulic fracturing is performed in the open horizontal wellbore by injection of fracturing fluid along the pipe string with a flow rate of 2 -3 m ³ / min to form a longitudinal crack formation in a relatively open horizontal portion of the well, wherein the fracturing fluid as used crosslinked gel, after which produ ny fastening injection longitudinal cracks along the pipe string proppant coarse fraction with a carrier fluid - a crosslinked gel, then produce a hydraulic fluid reservoir injection gap discontinuity through the pipe string through the horizontal wellbore and longitudinal crack fracture at a rate of 9.7 m ³ / min, and As a fracturing fluid, a linear gel is used, after which branched fractures of the hydraulic fracturing are fixed by injection of a proppant of a fine fraction with a carrier fluid - a linear gel.

The essence of the invention lies in the fact that after creating a longitudinal vertical crack, proppant is clogged with a crack perimeter, therefore, with a further increase in the injection rate, the crack is "inflated" and its length increases, which leads to a bending of the surface of the longitudinal crack. If the bending stress is exceeded above the tensile strength of the formation rock, cracks occur transverse to the plane of the longitudinal crack. With further movement of transverse cracks in the formation rock, they inevitably propagate in the direction of the minimum principal stress, which leads to the formation of branched cracks (see figure 2).

In figures 1 and 2 schematically and sequentially depicted the proposed method.

The method is implemented as follows.

The horizontal wellbore 1 (see Fig. 1) of the well 2 is drilled in the formation 3 perpendicular to the direction of the minimum principal stress - σ _min .

The casing 4 is lowered into the vertical part 5 of the well 2 and cemented.

In the proposed method, hydraulic fracturing in an open hole is carried out by a common filter, and not intervally, unlike the prototype, which allows to reduce the duration of hydraulic fracturing and reduce material and financial costs for implementing the method.

Next, a pipe string 6 is lowered into the casing 4 of the well 2, for example a tubing string 89 mm in diameter according to GOST 633-88 with a packer 7. The packer 7 is planted in the casing 4 of the vertical part 5 of the well 2.

As a packer 7, for example, a through packer with an anchor of a mechanical rotary installation PRO-YaM2-YaG1 (F) or PRO-YaM3-YaG2 (F) (per 100 MPa) manufactured by the Packer research and production company (Oktyabrsky, Republic of Bashkortostan, Russian Federation).

The proposed method allows to increase the reliability of hydraulic fracturing in the horizontal wellbore 1 by eliminating the interval packer landing in the horizontal wellbore 2 when hydraulic fracture intervals are cut off by packers, which eliminates the occurrence of emergency situations in the well associated with packer planting in the horizontal wellbore 1 2.

Then proceed to hydraulic fracturing of the reservoir 3 in the open horizontal wellbore 1 of the well 2. The total volume of the fracturing fluid for hydraulic fracturing is determined. The volume of the fracturing fluid depends on the viscosity of the fracturing fluid and filterability, the length of the horizontal wellbore and the height of the formation, as well as the permeability of the rocks of the bottom hole zone, the rate of fluid injection and the fracture pressure.

According to experimental data, the volume of the fracturing fluid for the horizontal wellbore 1, which opened the formation 3 with a height of 5 m to a length of 200 m, varies from 90 to 100 m ³ .

We will accept for our well the total volume of fracturing fluid:

V _p = 100 m ^{3 the} fracturing fluid, from which the volume of the fracturing fluid V _p1 = 50 m ³ - to create a longitudinal fracture 8 (see figure 1) hydraulic fracturing, and the remaining volume of the fracturing fluid V _p2 = 100 m ³ - 50 m ³ = 50 m ³ - to create branched cracks 9 ′, 9 ″ ... 9 ⁿ (see figure 2) relative to the horizontal wellbore from a longitudinal hydraulic fracture.

To create a longitudinal fracture 8 (see Fig. 1) of hydraulic fracturing, a fracturing fluid is used, which is used as a crosslinked gel with a dynamic viscosity of 150 cP. For example, a cross-linked hydrocarbon-based gel is used (see Chapter 3 of the monograph by S. A. Ryabokonya “Technological fluids for completion and repair of wells (OJSC NPO Bureniye, 2006, p. 153)), which includes a polymer solution (MO-NT ), crosslinking in hydrocarbon, and a temporary destructor (MO-NT hydrophobic modification of PAA) My-T-Oil (Halliburton).

A fracture fluid (crosslinked gel) is pumped through a pipe string 6 into an open horizontal wellbore 1 of a well 2 with a flow rate of 3 m ³ / min and a longitudinal fracture 8 of hydraulic fracturing relative to an open horizontal wellbore 1 is formed 2. A decrease in the injection pressure indicates the formation of a longitudinal crack 8 and an increase in injectivity of the formation 1. For example, when the crosslinked gel was injected into the reservoir 3, a pressure of 30 MPa was reached, due to the formation of a longitudinal crack 8 in the reservoir 3, the injection pressure of the crosslinked gel dropped by 25%, i.e. up to 22.5 MPa, while the injectivity of formation 3 increased by 50%, i.e. up to 4.5 m ³ / min.

In the process of the formation of a longitudinal crack 8 along the pipe string 6, a fracture fluid was pumped into reservoir 1 — a crosslinked gel in a volume of, for example, 20 m ³ . A longitudinal crack 8 is fastened by pumping 6 large proppant 10 through a pipe string 6, for example, a 12/18 mesh fraction (grain size 0.8-1.0 mm) with a carrier fluid (cross-linked gel) in the remaining volume of cross-linked gel 50 m ³ - 20 m ³ = 30 m ³ .

The proppant of fractions 12-18 mesh with a grain size of 0.8-1.0 mm is made in accordance with GOST R 51761-2005 - “Aluminosilicate proppants. Technical conditions ”- and is produced by the Borovichi Refractories Plant (Borovichi, Republic of Belarus).

A cross-linked hydrocarbon-based gel has a high viscosity in the formation, which, when injected into the formation with a flow rate of 3 m ³ / min, provides the creation of wide, deeply penetrating cracks with good filling by proppant material. When destruction does not form a sediment, does not damage the formation and proppant packing.

Continue hydraulic fracturing 3.

To create branched fractures 9 ′, 9 ″ ... 9 ⁿ (see FIG. 2) hydraulic fracturing relative to the horizontal wellbore 1 of a longitudinal fracture 8 hydraulic fracturing, a linear gel with a dynamic viscosity of 30 cP in the remaining hydraulic fracturing volume V _{p2 is used} = 50 m ³ .

For example, a linear water-based gel is used, which is prepared on water-soluble polymers of various nature of any known composition, for example, see S.A. Ryabokonya "Technological fluids for completion and repair of wells" (OAO NPO Bureniye, 2006, p.118).

A fractured fluid (linear gel) is pumped through a pipe string 6 (see FIG. 2) into an open horizontal wellbore 1 of a well 2 with a flow rate of 8 m ³ / min, and branched cracks 9 ′, 9 ″ are formed from the longitudinal fracture 8 of the hydraulic fracturing ... 9 ⁿ hydraulic fracturing relative to the horizontal wellbore 1 of the well 2 from a longitudinal fracture 9 hydraulic fracturing.

The formation of branched (longitudinal and transverse) cracks 9 ′, 9 ″ ... 9 ⁿ hydraulic fracturing is indicated by a decrease in injection pressure and an increase in injectivity of formation 1. For example, when the linear gel was injected into the formation 3, a pressure of 33 MPa was reached due to the formation of longitudinal and transverse cracks 9 ′, 9 ″. ... 9 ⁿ hydraulic fracturing, the injection pressure of the crosslinked gel decreased by 25%, i.e. up to 24.75 MPa, while the injectivity of formation 3 increased by 30%, i.e. up to 10.4 m ³ / min.

In the process of the formation of branched cracks 9 ′, 9 ″. ... 9 ⁿ , a fracture fluid was pumped into the pipe 1 through a pipe string 6 — a linear gel in a volume of, for example, 25 m ³ . Fasten longitudinal and transverse cracks 9 ′, 9 ″.… 9 ^{n are} injected in a column of tubes 6 of proppant 11 of a fine fraction, for example quartz flour with a carrier fluid (linear gel), in the remaining linear gel volume of 50 m ³ - 25 m ³ = 25 m ³ .

As a small proppant, quartz flour with a grain size of 0.05-0.15 mm is used, which is produced according to TU5717-001-16767071-99, a supplier of Quartz Trading House LLC (Ekaterinburg, Russia).

The linear gel has small friction losses in the pipes, which, at a high injection rate of 8 m ³ / min, allows penetration deep into the reservoir and ensures uniform deposition of fine proppant in the longitudinal crack 8, as well as in branched cracks 9 ′, 9 ″ ... 9 ⁿ

The efficiency of the method implementation in a reservoir with low reservoir filtration and reservoir properties is increased by attaching a longitudinal crack 8 with a proppant of a large fraction, and branched cracks 9 ′, 9 ″. ... 9 ^{n with a} proppant of a small fraction. As a result, fine fraction proppant grains bind coarse fraction proppant grains in a longitudinal fracture 8, excluding the mobility of the latter, which excludes the closure of a longitudinal fracture 8 and proppant exit into an open horizontal wellbore 1 of well 2 in formation 3 and maintains its throughput.

The process of hydraulic fracturing of the horizontal wellbore is over. Unpack the packer 7 and remove from the well 1 a string of pipes 6 with a packer 7. Lower operational equipment (not shown in FIGS. 1 and 2) into the well 2 and put into operation.

The proposed method of hydraulic fracturing in an open horizontal wellbore can increase the efficiency of hydraulic fracturing by creating longitudinal fractures from the horizontal wellbore and then branched fractures from the longitudinal fractures, followed by filling the fractures with proppant of various fractions, which minimizes proppant outflow into the horizontal wellbore during the subsequent operation of the well, thereby eliminating the closure of cracks and maintaining permeability in the near-wellbore zone . Also, the proposed method can improve reliability by eliminating the cut-off of each fracturing interval by packers, reduce the duration of hydraulic fracturing and reduce the material and financial costs of implementing the method.

Claims (1)

A method of hydraulic fracturing in a horizontal wellbore, including drilling a horizontal well, lowering the casing into the vertical part of the well and cementing it, lowering the string of pipes with a packer into the well, planting the packer, forming cracks in hydraulic fracturing in the horizontal wellbore by pumping fluid through the string fracture, cracks fastening by injection of a carrier fluid with proppant, characterized in that the horizontal wellbore is drilled in the formation perpendicular to the minimum direction main stress, lower the pipe string with the packer into the well and put the packer in the vertical part of the well, produce hydraulic fracturing in the open horizontal wellbore by pumping the fracturing fluid along the pipe string with a flow rate of 2-3 m ³ / min with the formation of a longitudinal crack in the formation relative to open horizontal part of the well, moreover, a cross-linked gel is used as a fracturing fluid, after which a longitudinal crack is fixed by injection of a large fraction of proppant tubes with a carrier fluid through the pipe string m - the crosslinked gel, and then produce a hydraulic fracturing pumping fracturing fluid through the pipe string through the horizontal wellbore and longitudinal crack fracture at a rate of 9.7 m ³ / min, and as a fracturing fluid using a linear gel, whereupon fastening branched hydraulic fracture fracturing a proppant by injection of a fine fraction with a liquid - carrier - linear gel.

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