RU2526062C1 - Multiple hydraulic fracturing of formation in well horizontal shaft - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: proposed method comprises formation of fractures in different intervals of productive bed exposed by the well horizontal shaft by lowering the packer on pipe string. Packer is fitted in the well to feed hydraulic fracturing fluid in the filter mounted at every part of horizontal shaft corresponding to every said interval. Other parts are isolated to make fractures to be lined by forcing carrier fluid with proppant therein. Interval hydraulic fracturing is performed in direction from the face to head by pipe string lowering. Pipe string represents a string of flexible pipes with drillable packer at the end. Drillable packer seating is performed ahead of every section of the well horizontal shaft filter, fractures are produced and lined by forcing carrier fluid with proppant therein. To fix proppant in well zone, fixing solution is forced in pipe string at the rate of 0.5 m³ per 1 metre of filter length and into said zone in one and a half volume of pipe string. Thereafter, wellhead is sealed by wellhead gland. Well tubular space is lined out with hydraulic accumulator. Then, without decreasing hydraulic pressure in pipe string, it is lifted by 1 metre. Hydraulic accumulator takes up hydraulic pressure surge in well annulus while drillable packer tightly shuts off the filter section whereat hydraulic fracturing occurs. The, pipe string is withdrawn from the well to make interval hydraulic fracturing in other filter sections of the well horizontal shafts. At termination of hydraulic fracturing, pipe string at wellhead if equipped with drillable toll and jet head. Pipe string is lowered in the well to remove packers by drilling-out from wellhead to face. Then, drillable tool is cut out to force fluid in pipe string along with its rotation and displacement from face to head to jet processing of inner surface of filters via jet head.

EFFECT: higher efficiency and reliability, accelerated tripping processes.

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Description

The invention relates to the oil and gas industry, in particular to methods of hydraulic fracturing in horizontal boreholes of productive formations in weakly cemented rocks.

A known method of multiple hydraulic fracturing of a horizontal wellbore (Study of factors and the implementation of measures for the long-term operation of oil and gas wells. Treatment of the bottom-hole formation zone by chemical methods and physical methods / Basarygin Yu.N. [et al.] - Krasnodar: Education-South, 2004. - book 1 - p. 173), in which, to break the formation, they lower it into the well on tubing - tubing - a packer that isolates the filter installed in the wellbore, including horizontal, of the well, at the required hydraulic fracturing location, n Farthest from the vertical wellbore, from the rest of the well, hydraulic fracturing is carried out, forming a crack in this interval, then a packer is installed in the same wellbore in front of the filter located closer to the vertical wellbore than the above filter, and hydraulic fracturing is performed, forming the next crack, while the filter is blocked by a proppant plug, the above operations are repeated even if the interval is broken through the filter, successively approaching the vertical trunk.

The disadvantages of the method:

- firstly, in the process of conducting multiple interval hydraulic fracturing, the packer is reinstalled at various filter intervals of the horizontal wellbore, and there are difficulties in unpacking the packer anchor unit, since hydraulic fracturing is performed under high pressure;

- secondly, when the packer moves along the horizontal wellbore, the packer’s sealing element may be damaged and, as a result, the packer will lose its tightness during subsequent planting, which leads to additional tripping and revision of the packer.

A known method of multiple hydraulic fracturing in a horizontal wellbore (patent RU No. 2472926, IPC ЕВВ 43/267, published on January 20, 2013, Bull. No. 2), including the descent of the packer into the well on a pipe string, followed by its landing in 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 remaining of parts. In this case, the direction of the horizontal trunk relative to the direction of the minimum main stress is determined, then the interval subject to hydraulic fracturing — the hydraulic fracturing — is isolated from the remaining sections of the horizontal wellbore by landing of twin packers, then the valve located inside the pipe string between the twin packers opposite the filter is opened if the direction of the horizontal trunk parallel to the direction of the minimum principal stress, the hydraulic fracturing is carried out by injection of a fracturing fluid with the formation of transverse cracks relative to the horizontal wellbore, followed by the fastening of transverse cracks by pumping fluid with aluminosilicate proppant, with a gradual increase in its fraction from 20/40 mesh 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 by injection explosive fluid with the formation of horizontal cracks relative to the horizontal trunk, followed by fastening of horizontal cracks by pumping fluid with lightweight proppant with a fraction of 20/40 mesh. At the end of hydraulic fracturing, the well is closed for a technological pause for 0.5 h, after which an adjustable nozzle is installed on the pipe mouth at the wellhead and the spent proppant fluid is poured from the formation along the pipe string at the wellhead until the valve is closed, while during the outflow nipples make sure that the pressure in the pipe string becomes 2-3 MPa less than the pressure when opening the well after a technological break, after which the packer is unpacked and the pipe string is moved to another part of the horizontal the onshore well, and the above-described process for conducting hydraulic fracturing in a horizontal wellbore is repeated depending on the number of horizontal well intervals equipped with filters in its various parts.

The disadvantages of the method:

- firstly, the impossibility of implementing the method in weakly cemented formation rocks, since the proppant grains filling the fracture in the near-wellbore zone are not fixed to each other, therefore, after the proppant cracks are fixed in the weakly cemented formation rocks, subsequent graining of pressure from the well to the horizontal wellbore will take place proppant, which will lead to the closure of cracks and a sharp decrease in the throughput capacity of fractures in the wellbore zone, which will reduce the effectiveness of the implementation of the method but:

- secondly, the complex design of dual packers, as well as the difficulties in landing and unpacking these packers in the well;

- thirdly, low reliability associated with the possibility of loss of tightness of one of the dual packers, since at high pressures (up to 40 MPa) it is almost impossible to ensure the tightness of both packers during hydraulic fracturing.

The closest in technical essence is the method of multiple hydraulic fracturing of a horizontal wellbore (patent RU No. 2362010, IPC ЕВВ 43/267, publ. 07/20/2009, Bull. No. 20), including the formation of cracks in series at different intervals of the reservoir, opened horizontal wellbore, by installing a packer, supplying hydraulic fracturing fluid through a filter installed in each of the parts of the horizontal wellbore corresponding to each of these intervals with isolation of its remaining parts, installing the os packer implemented at the vertical wellbore. Initially, hydraulic fracturing is carried out in the interval of the formation with the highest permeability by supplying a proppant carrier fluid with the installation of a “head” proppant plug blocking the corresponding section of the horizontal wellbore between the filters, with the indicated insulation by forming a polymer crust on the corresponding filters, repeat this operation on each of the others intervals sequentially by the degree of reduction of their permeability with preliminary removal of the crust from the filter corresponding to this interval. Moreover, the polymer crust is formed by supplying a chemical composition to the well, and its removal is carried out by a solvent liquid with a content of a gel breaker of 0.6-1.2 kg / m ^{3 of} water.

The disadvantages of this method:

- firstly, it is impossible to implement the method in weakly cemented formation rocks, since proppant grains filling the fracture in the near-wellbore zone are not fixed to each other, therefore, after the proppant cracks are fixed in weakly cemented formation rocks, subsequent graining of pressure from the well to the horizontal wellbore will take place proppant, which will lead to the closure of cracks and a sharp decrease in the throughput capacity of the fractures in the wellbore zone, which will reduce the efficiency of the method;

- secondly, when washing out the polymer crust, the fluid will “go” into the washout interval, while in other filter intervals the polymer crust will be washed only partially, possibly clogging the filter openings, or not at all, which will prevent the flow of oil into the horizontal wellbore in the process of subsequent operation and reduce the effectiveness of the hydraulic fracturing (hydraulic fracturing);

- thirdly, the long duration of hydraulic fracturing, due to the fact that the packer is installed in the vertical wellbore, and hydraulic fracturing is carried out at intervals depending on the permeability of the formation, so if it is necessary to conduct hydraulic fracturing through the filter in the middle of the horizontal wellbore, it is necessary to isolate the filter parts in " heel ”and“ toe ”by injection of the chemical composition with the formation of a polymer crust, hydraulic fracturing in the middle part of the filter, followed by leaching of the polymer composition from the filter part to the“ heel ” and "toe" of the horizontal wellbore. Subsequently, this process is repeated for the filter section of a horizontal wellbore having a high permeability;

- fourthly, the proppant plug, which is used to fill the horizontal wellbore, does not provide complete tightness during hydraulic fracturing at other intervals of the horizontal well, as it absorbs liquid during hydraulic fracturing;

- fifth, the low efficiency of the installation of the polymer crust, since after hydraulic fracturing, the pressure is released, during which the polymer crust is extruded into the horizontal wellbore.

The technical objectives of the proposal are to increase the reliability and efficiency of the implementation of the method in poorly cemented formation rocks, reduce the duration of tripping operations during hydraulic fracturing with the possibility of hermetically cutting off intervals from each other.

The stated technical problems are solved by the method of multiple hydraulic fracturing in a horizontal wellbore, including the formation of cracks sequentially at different intervals of the productive formation, opened by a horizontal wellbore, by lowering the packer pipes on the string, installing it in the well, and supplying the hydraulic fracturing fluid through a filter installed in each from the parts of the horizontal trunk corresponding to each of these intervals, with isolation of its remaining parts with the formation of cracks, cracks pumping carrier fluid with proppant.

What is new is that hydraulic fracturing in the horizontal wellbore is performed at intervals from the bottom to the mouth by lowering the pipe string, while the pipe string is a flexible pipe string with a drillable packer at the end, and the drillable packer is planted in front of each section of the horizontal filter the borehole, form cracks, fix them by pumping the carrier fluid with proppant, and to fix the proppant in the near-well zone, at the end of pumping the carrier fluid with as an adversary, the fixing composition is pumped into the pipe string at the rate of 0.5 m ^{3 of} fixing composition per 1 m of the filter length and pressed into the borehole zone of the formation in the one and a half volume of the pipe string, after which the wellhead is sealed with a wellhead seal and the annular space of the well is tied up with a hydraulic accumulator then, without reducing the hydraulic pressure in the pipe string, the pipe string is raised by 1 m, while the hydraulic accumulator perceives a hydraulic pressure jump occurring in the annulus of the well, and the packer being sealed shut off the filter section in which the hydraulic fracturing was performed, after which the pipe string was removed from the well, the interval hydraulic fracturing in the following filter sections of the horizontal wellbore was similarly performed; at the end of the hydraulic fracturing, the drill pipe string at the wellhead was first equipped with a drillable with a tool and then with a hydraulic nozzle, lower the drill pipe string into the well and remove packers from the mouth to the bottom by drilling, yes then, the drillable tool is cut off and, by supplying fluid to the drill pipe string with its simultaneous rotation and movement from the bottom to the mouth, a hydromonitor processing of the inner surface of the filters is performed through the hydromonitor nozzle.

In figures 1, 2, 3 schematically and sequentially depicted the proposed method of multiple hydraulic fracturing in a horizontal wellbore.

The method is implemented as follows.

Hydraulic fracturing in the horizontal wellbore 1 (see Fig. 1) of the well 2 is carried out at intervals in the direction from the bottom 3 to the wellhead 4 by sequential descent on the pipe string 5 through-drilled packers 6 ', 6 "... 6 ⁿ and planting them in front of each filter section 7 ', 7 "... 7 ⁿ in the horizontal wellbore 1 of the well 2.

The formation of cracks 8 is carried out by injection of hydraulic fracturing fluid, followed by fastening of cracks 8 by injection of carrier fluid with proppant 9.

As the string of pipes 5, a string of flexible pipes is used, for example, 60 mm in diameter with a drillable packer at the end. The use of a string of flexible pipes reduces the duration of tripping operations during hydraulic fracturing.

As the fracturing fluid, a gelled fracturing fluid is used — a linear gel, which is prepared by any known method, for example, as described in RU patent No. 2381252, IPC C09K 8/68, publ. 02/20/2010

As proppant 9 use, for example, proppant fractions 20-40 mesh, which is manufactured according to GOST P 51761-2005 - "Aluminosilicate proppants. Specifications ”and produced at the Borovichi Refractories Plant (Borovichi, Republic of Belarus).

As a drill-through packer used, for example, a PRK-NM packer manufactured by Neftyanik LLC (Bugulma, Republic of Tatarstan) is used.

The use of drillable packers provides a tight cut-off of the filter intervals after hydraulic fracturing, so that the excess pressure that occurs during hydraulic fracturing is etched off into the formation, and not into the wellbore, and this eliminates the proppant outflow into the horizontal wellbore.

At the end of the injection of the carrier fluid with proppant through the pipe string 5 of the well 2, the fixing composition 10 is injected at the rate of 0.5 m ³ per 1 m. To fix the proppant 9 in the near-well zone of the well 2, any known fixing composition 10 is used, for example, described in RU patent No. 2172814, ЕВВ 33/138, publ. August 27, 2001). The composition contains the following components, wt.%:

- grouting cement - 50;

- sand (fraction 0.3-1.5 mm) - 10;

- shell rock (fraction 0.7-1.5 mm) - 10;

- salt (sodium chloride, fraction of 2-3 mm) - 10;

- nonionic surfactant (disolvan 4411) - 0.5-1;

- water - the rest (until the fluidity of the solution is 18-20 cm along the cone of the AZNII).

The volume of the fixing composition is determined from the calculation of 0.5 m ³ per 1 m of the length of one of the filters 7 ', 7 "... 7 ⁿ . For example, with a filter length of 7' equal to 10 m, 5 m ^{3 of} fixing composition 10 is prepared, which is pumped into pipe string 5 of well 2.

The use of this fixing composition provides the creation of a filter permeable to reservoir fluids by leaching from salt proplat and the formation of communicating permeable channels.

The permeability of the proppant with the fixing composition can be further increased by conducting an acid treatment to dissolve the shell rock.

Next, the fastening composition 10 is pushed from the pipe string 5 using the squeezing fluid through the holes 11 of the nipple 12 of the drillable packer 6 ′ and the filter 7 ′ into the borehole zone of the well 2 in the one and a half volume of the pipe string 5, for example, the volume of the pipe string 6 is 5 m ³ , then one and a half the volume of the pipe string 5 will be: 5 m ³ · 1.5 = 7.5 m ³ .

As a squeezing liquid, for example, fresh water with a density of 1180 kg / m ^{3 is used} .

The use of fixing composition allows to increase the reliability and efficiency of the method in weakly cemented rocks and eliminates proppant removal into the horizontal wellbore during hydraulic fracturing and during subsequent operation of the well.

The wellhead 2 is sealed with a wellhead seal 13, and the annular space 14 of the well 2 is in fluid communication with the accumulator 15.

Then, without reducing the hydraulic pressure that has arisen in the pipe string 5 during the delivery process, for example 30 MPa, the pipe string is lifted by 1 m, while the nipple 12 with holes 11 rises above the drilled packer 6 '(see Fig. 1). As a result, the holes 11 of the nipple 12 are in communication with the annular space 14 of the well 2, while the accumulator 15 perceives a hydraulic pressure jump occurring in the annular space 14 of the well 2, and the nipple 12 hermetically closes the passage opening of the drillable packer 6 '(see Fig. 2), as a result, the drillable packer 6 'hermetically cuts off a section of the filter 7', in which the hydraulic fracturing of the formation from the horizontal wellbore 1 is carried out 2. The pipe string 5 is removed from the well 2.

Similarly, the interval hydraulic fracturing is successively performed in the following sections of the 7 "... 7 ⁿ filters (see Fig. 2) of the horizontal wellbore 1 of the well 2. To do this, run 5 drillable packers 6" ... 6 ⁿ on the pipe string and fit them respectively in front of the filter sections 7 "... 7 ⁿ .

The formation of cracks 8 '... 8 ^{n is} carried out by injection of hydraulic fracturing fluid followed by the fastening of cracks 8' ... 8 ^{n by} injection of carrier fluid with proppant 9 and the proppant 9 is fixed in the near-bore zone with the fixing composition 10, as described above.

At the end of hydraulic fracturing, in all sections of the filters 7 ', 7 "... 7 ^{n of the} horizontal wellbore 1 of the well 2, a drill pipe string (not shown in Figs. 1, 2, 3) at the mouth 4 (see Fig. 2) is first equipped with a drillable tool, for example, with a chisel (not shown in FIGS. 1, 2, 3), and then with a hydraulic nozzle with holes (not shown in FIGS. 1, 2, 3), opposite which a sleeve with a seating saddle is sealed in the hydraulic nozzle (in FIG. 1 , 2, 3 not shown) under the ball discharged from the mouth, the sleeve is fixed with a shear screw.

The drill pipe string is lowered into the well 2 (see FIG. 2) and, by drilling, for example, with a chisel from the mouth to the bottom, packers 6 ', 6 "... 6 ⁿ and the fixing composition 10 are removed from the horizontal shaft 1 of the well 2, then the drillable tool is cut off. To do this, a ball is thrown into the drill pipe string (not shown in Figs. 1, 2, 3), which sits on the landing seat of the sleeve installed in the hydraulic nozzle, creating excessive pressure in the drill pipe string, which leads to the destruction of the shear element and the movement of the sleeve down by excessive of pressure. As a result, holes are opened in the jet nozzle.

Then, by supplying a liquid, for example fresh water with a density of 1000 kg / m ³ , to the drill pipe string with its simultaneous rotation, for example, at a speed of 10 rpm and moving from the bottom to the mouth, for example, at a speed of 0.05 m / s processing the inner surface of the filters 7 ', 7 "... 7 ⁿ (see figure 3).

Along the perimeter of the filters 7 ', 7 "... 7 ^{n the} directional flow (liquid stream) through the hydraulic nozzle is washed from the inner surface and the holes of the filters 7', 7" ... 7 ^{n the} remains of the chips, proppant, resin until they stop on the mouth washed out residues (visually determined by the exit of a transparent liquid at the mouth of 4 wells 2).

The proposed method of multiple hydraulic fracturing in a horizontal wellbore can improve the reliability and efficiency of the method in poorly cemented formation rocks, reduce the duration of tripping operations during hydraulic fracturing with the possibility of hermetically cutting off intervals from each other.

Claims (1)

The method of multiple hydraulic fracturing in a horizontal wellbore, including the formation of cracks successively at different intervals of the reservoir, opened by a horizontal wellbore, by lowering the packer pipes on the string, installing it in the well, supplying the hydraulic fracturing fluid through a filter installed in each of the respective of these intervals of the parts of the horizontal trunk, with the isolation of its remaining parts with the formation of cracks, fixing cracks by pumping a carrier fluid from propp characterized in that the hydraulic fracturing in the horizontal wellbore is carried out at intervals from the bottom to the mouth by lowering the pipe string, while the pipe string is a flexible pipe string with a drillable packer at the end, and the drillable packer is planted in front of each filter section horizontal wellbore, form cracks, fix them by pumping carrier fluid with proppant, and to fix proppant in the near-wellbore zone, at the end of pumping fluid with proppant, the fixing composition is pumped into the pipe column at the rate of 0.5 m ^{3 of} fixing composition per 1 m of filter length and pressed into the borehole formation zone in the one and a half volume of the pipe string, after which the wellhead is sealed with a wellhead seal and the annular space of the well is tied up with a hydraulic accumulator , then, without reducing the hydraulic pressure in the pipe string, raise the pipe string by 1 m, while the hydraulic accumulator perceives a jump in hydraulic pressure that occurs in the annulus of the well, and p the booster packer hermetically seals the filter section in which the hydraulic fracturing is performed, after which the pipe string is removed from the well, the interval hydraulic fracturing in the following filter sections of the horizontal wellbore is similarly performed; at the end of the hydraulic fracturing, the drill pipe string at the wellhead is first equipped with a drillable with a tool, and then with a hydraulic nozzle, lower the drill pipe string into the well and remove packers from the mouth to the bottom by drilling , then the drillable tool is cut off and fluid supply to the drill pipe string with its simultaneous rotation and movement from the bottom to the mouth produces a hydromonitor treatment of the inner surface of the filters through a hydromonitor nozzle.

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