RU2537719C1 - Method of multiple hydrofracturing of formation in open hole of horizontal well - Google Patents

Abstract

FIELD: mining.SUBSTANCE: method comprises the drilling of a horizontal well bore in oil saturated part of the productive formation of the well, tripping of the pipe string into the well, the forming of perforations and fractures using the a hydrofracturing of formation in the hole of horizontal well, successively, starting from the end of far from the vertical borehole axis. During the next hydrofracturing the section, through which hydrofracturing is performed, is insulated from another part of the string with a packer. During drilling of the horizontal well bore the permeability and porosity of rocks are determined and the intervals of the productive formation with low permeability and porosity of rocks are identified, and on completing of drilling the rock hydrofracturing pressure is determined in each interval of the horizontal borehole. Then the volumes of fracturing fluid and acid for each interval of the oil saturated part of the formation with low permeability and porosity are determined, then the pipe string is moved to the interval of the productive formation nearest to the borehole bottom, with low permeability and porosity, the mechanical packer is seated, from hole mouth using the pumping unit the gelled fracturing fluid is injected into the pipe string through nozzles of the water jet tool and reshape perforations, then, not stopping injection gelled of fracturing fluid on a pipe string, construct fracture pressure applicable to the given interval of the oil saturated part of the productive formation. After 30% drop of pressure of injection of gelled fracturing fluid in the pipe string the hydrofracturing fractures are formed, for this purpose into the annular space of the well an acid is injected at the variable flow rate ensuring maintaining of pressure of injection of gelled fracturing fluid in the pipe string 10% less than the fracture pressure for the given interval of the oil saturated part of the productive formation. The packer releasing is performed and the pipe string is removed from bottomhole to the mouth into the following interval of the oil saturated part of the formation with low permeability and porosity of rocks for forming perforations and conducting of a hydrofracturing of the formation with forming and progressing of fractures.EFFECT: shortening time for formation hydrofracturing, improvement of performance and reliability of formation hydrofracturing.3 dwg

Description

The invention relates to the oil and gas industry, in particular to methods of hydraulic fracturing in open trunks of horizontal wells that have opened productive formations with low filtration-capacitive properties.

A known method of hydraulic fracturing (RU No. 2311528, E21B 43/26, publ. 11/27/2007, bull. No. 33), including opening the formation of a vertical or inclined well, placing in it a predetermined interval of the formation of a hydraulic monitoring tool with a series of jet nozzles, injection working fluid through the jet nozzles of a hydraulic monitoring tool for the formation of caverns in the formation, the subsequent fracture of the reservoir from the caverns due to the braking pressure of the jet in them, using a hydraulic monitoring tool with a series of jet nozzles located along the tool in two lines with a phasing of 180 ° and a distance between the nozzles in a line of no more than two casing diameters, the hydromonitor tool is rotated by a predetermined angle to change the direction of development of each subsequent crack, while cracks form at a pressure in the casing below the side rock pressure, and as a working fluid, a fluid related to the formation fluid is used.

The disadvantages of the method:

- firstly, the use as a direction of cracks before hydraulic fracturing (hydraulic fracturing) of sandblasting perforation, which makes an opening of the casing string and productive formation working fluid (a mixture of sand and water). In the process of opening a terrigenous type reservoir containing clay interlayers and clay cement (carbonate cement), they interact with water, which leads to clay swelling and salt precipitation, and subsequently to a decrease in rock permeability, which negatively affects the formation of cracks (caverns) and for hydraulic fracturing for injection of fracturing fluid and sand carrier;

- secondly, the deposition of sand along the entire length of the horizontal wellbore during the sandblasting perforation to guide hydraulic fracturing, which requires additional washing of the well before hydraulic fracturing.

Also known is a method of multiple hydraulic fracturing in a horizontal wellbore (patent RU No. 2472926, IPC E21B 43/267, publ. 01/20/2013, bull. No. 2), including the descent of the packer into the well on a pipe string with its subsequent landing in the well, the formation of cracks opposite the filters in series at different intervals of the reservoir, opened by a horizontal bore by supplying hydraulic fracturing fluid through a filter installed in each of the parts of the horizontal bore corresponding to each of these intervals with isolation of the rest its 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 well 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 well is parallel to the direction of the minimum principal stress, the hydraulic fracturing is performed by injection of a fracturing fluid with the formation of transverse cracks relative to the horizontal trunk, followed by the fastening of transverse cracks by pumping a fluid with aluminosilicate proppant, with a gradual increase in its fraction from 20/40 mesh. up to 16/30 mesh, if the direction of the horizontal wellbore is perpendicular to the direction of the minimum principal stress, then hydraulic fracturing is carried out by injection of a fracturing fluid with the formation of horizontal cracks relative to the horizontal wellbore, followed by horizontal cracking by pumping fluid with a lightweight proppant with a 20/40 mesh fraction. 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 removal of proppant grains, leading to the closure of cracks and a sharp decrease in the throughput of the formation cracks in the near-wellbore zone, which reduces the efficiency of the method;

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

- thirdly, low reliability associated with the possibility of loss of tightness of one of the twin 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 hydraulic fracturing in a horizontal wellbore (patent No. 2401942, IPC E21B 43/267, publ. 10/20/2010, bull. No. 29), including drilling a well, cementing a horizontal wellbore, perforating and forming cracks with using hydraulic fracturing in a horizontal wellbore sequentially, starting from the end farthest from the axis of the vertical wellbore, communicating the horizontal wellbore with the productive formation, while during the next hydraulic fracturing each perforated section through which hydraulic fracturing is performed is isolated from the rest of the column 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 is azimuthally oriented at intervals produced using a hydromechanical slotted puncher in one round trip operation, after which the packers are lowered, compartments 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 perforated section of the horizontal wellbore farthest from the axis of the vertical wellbore, moreover, the hydromechanical slotted perforation performs two-sided formation of cracks that are located 180 ° relative to each other in a vertical plane opposite each other, relative to the axis of the horizontal wellbore in one interval They either perform one-sided hydromechanical slotted perforation with a rotation of 180 ° in a vertical plane relative to the axis of the horizontal wellbore, alternately after each subsequent interval - in a checkerboard pattern equal to the length of the formed gap, or with a small thickness of the reservoir and in the presence of active bottom water produce unilateral hydromechanical slotted perforation in the direction of the formation roof.

The disadvantages of the method:

- firstly, the complex and lengthy process of implementing the method associated with the descent of the casing string into the horizontal wellbore and its subsequent cementing, performing hydromechanical slotted perforation in each interval of the cased horizontal well before hydraulic fracturing;

- secondly, the low efficiency of hydraulic fracturing, due to the fact that hydraulic fracturing is performed at intervals of hydromechanical slotted perforation performed in cased and cemented casing, so the perforation channels in the rock are extremely small;

- thirdly, the low accuracy of creating cracks in the reservoir in the desired interval and the inability to control the pressure of hydraulic fracturing;

- fourthly, low reliability associated with the landing and unpacking of two packers during isolation of each interval, while there may be a loss of tightness of one or two packers at once, as well as the pipe string, which leads to the impossibility of hydraulic fracturing in a given interval.

The technical objectives of the proposal are to increase the efficiency and reliability of hydraulic fracturing by creating cracks in the reservoir in the desired interval with high accuracy, as well as simplifying and reducing the duration of the method.

The stated technical problems are solved by the method of multiple hydraulic fracturing in an open borehole of a horizontal well, including drilling a horizontal wellbore in the oil-saturated part of the reservoir, lowering the pipe string into the well, forming perforation channels and cracks using hydraulic fracturing in the horizontal wellbore sequentially, starting from the end farthest from the axis of the vertical wellbore, communicating the horizontal wellbore with the reservoir, while The behavior of another hydraulic fracture portion through which produce fracturing, isolated from the rest of the column packer.

New is that in the process of drilling a horizontal wellbore, the reservoir properties of rocks are determined and intervals of the reservoir with low reservoir properties of rocks are identified, after drilling at the wellhead, a plug with a mechanical packer is installed at the lower end of the pipe string, and higher hydraulic nozzle with nozzles, lower the pipe string into the well so that the nozzle of the nozzle is opposite the interval of the oil-saturated part of the reservoir to the bottom of the well, with low filtration and capacitive properties, the mechanical packer is planted in the horizontal well, the process fluid is pumped from the wellhead with the pump unit and the fracture pressure is determined in the specified horizontal well interval, the unpacking is performed, the pipe string is moved from the bottom to the well in the next interval of the oil-saturated part of the reservoir with low reservoir properties, similarly determine the fracture pressure of rocks in other interactions the shafts of the oil-saturated part of the formation with low reservoir properties, then determine the volumes of gelled fracturing fluid and acid for each interval of the oil-saturated part of the reservoir with low reservoir properties, then move the pipe string to the interval of the reservoir closest to the bottom of the well, with low filtration and capacitive properties, the mechanical packer is planted, the gelled fracturing fluid is pumped from the wellhead using a pumping unit along the pipe string through hydraulic nozzles and form perforation channels, after which, without stopping the injection of the gelled fracture fluid through the pipe string, create a hydraulic fracturing pressure corresponding to this interval of the oil-saturated part of the reservoir, after a 30% drop in the injection pressure of the gelled fracture fluid in the pipe string, fracture form , for this, acid is pumped into the annular space of the well with a variable flow rate, which ensures the maintenance of the injection pressure of the gelled fracturing fluid along the pipe string is 10% less than the hydraulic fracturing pressure for a given interval of the oil-saturated part of the reservoir, unpack and move the pipe string from the bottom to the mouth to the next interval of the oil-saturated part of the formation with low reservoir properties of the rocks to form perforation channels and conduct hydraulic fracturing with formation and crack development.

1 and 2 depict the process of implementing the multiple hydraulic fracturing method in the open hole of a horizontal well.

Figure 3 shows the process of forming a perforation channel.

A method of multiple hydraulic fracturing in an open wellbore of a horizontal well involves drilling a horizontal wellbore 1 (see FIG. 1) in an oil-saturated part of a productive wellbore.

In the process of drilling a horizontal wellbore 1, the reservoir properties of the rocks are determined and intervals in the oil-saturated part of the reservoir with low reservoir properties of the rocks are identified, for example, three intervals - 2 ′, 2 ″, 2 ″ ″ (see FIG. 2).

After drilling at the wellhead (not shown in FIGS. 1, 2, 3), a plug 4 (see FIG. 1) with a mechanical packer 5 is installed on the lower end of the pipe string 3, and a nozzle 6 with nozzles 7 is placed above (for example , in the amount of 3 nozzles located around the perimeter of the jet nozzle at an angle of 120 ° between the nozzles). The string of pipes 3 is lowered into the well so that the nozzles 7 of the jet nozzle 6 are located opposite the interval 2 ′ of the oil-saturated part of the reservoir next to the bottom 8 of the well with low filtration and capacitive properties. As a mechanical packer 5, a packer of any known design is used, for example, a packer with an anchor with a mechanical rotary installation PRO-YaM2-YaG1 (F) or PRO-YaM3-YaG2 (F) (per 100 MPa) manufactured by the Packer research and production company (October city, Republic of Bashkortostan, Russian Federation).

Produce a landing mechanical packer 5 in the horizontal barrel 1.

From the wellhead using a pumping unit (not shown in FIGS. 1, 2, 3), for example, CA-320, the process fluid is pumped into the interval 2 ′ (see FIG. 1) of the horizontal wellbore 1 and the rock fracturing pressure is determined in the interval 2 ′ Horizontal barrel 1. The fracturing pressure of the rocks is determined by increasing the injection pressure to a certain value and its drop, for example, by 30%. For example, the fracturing pressure of rocks (P _Tr ) in the interval 2 ′ of the horizontal wellbore 1 is 20 MPa.

As a process liquid, for example, a 2% aqueous KCl solution is used, and waste water with a density of 1180 kg / m ³ is used as water.

Unpack the mechanical packer 5. Move the pipe string 3 from the bottom 8 to the mouth to the next 2 ″ interval (see FIG. 2) of the oil-saturated part of the formation with low reservoir properties of the rocks so that the nozzles 7 of the nozzle 6 are opposite the interval 2 ″ oil-saturated parts.

Similarly, as described above, starting with the planting of a mechanical packer and its unpacking, the fracture pressure of the rocks is determined in the intervals 2 ″ and 2 ″ ″ of the oil-saturated part of the formation with low filtration-capacitive properties.

For example, the fracturing pressure of the rocks in the interval 2 ″ horizontal bore 1 is 18 MPa, and the fracturing pressure of the rocks in the interval 2 ″ ″ horizontal bore is 1-24 MPa.

Preliminary determination of the hydraulic fracturing pressure in all intervals 2 ′, 2 ″, 2 ″ ″ of the oil-saturated part of the formation with low filtration and capacitive properties eliminates possible leakage of the packer and / or pipe string during subsequent hydraulic fracturing in these intervals and controls the hydraulic fracturing pressure since the fracture pressure in each of the intervals 2 ′, 2 ″, 2 ″ ′ is known. After determining the hydraulic fracturing pressure for each oil saturated interval 2 ′, 2 ″, 2 ″ ″ (see FIG. 2), the formation with low filtration-capacitive properties determines the required injection volumes of the gelled fracturing fluid and acid to create perforation channels 9 ′, 9 ″, 9 ″ ′ fracture cracks 10 ′, 10 ″, 10 ″ ″ and their development in each corresponding interval 2 ′, 2 ″, 2 ″ ″, for example, according to the formula given in patent RU No. 2455478, IPC E21B 43/26, publ. . in bull. No. 19 dated July 10, 2012.

Determine the volume of gelled fracturing fluid injected into each of the intervals 2 ′, 2 ″, 2 ″ ″, according to the formula

V _g = k · H _p

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

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

H _p - the average thickness of the reservoir, m

Take k = 1.6 m ³ / m. For example, the average thickness of the reservoir is H _p = 5 m. Then, substituting the values in the formula, we obtain the total volume of the injected gel-like fracturing fluid

V _g = 1.6 · 5 = 8 m ³ .

The volume of 2 ′, 2 ″, 2 ″ ″ gelled fracturing fluid injected into each interval is 8 m ³ .

As a gel-like fracturing liquid, known compositions are used, for example, those developed by Khimekogang CJSC with the trade names Himeko-N (TU2481-053-17197708), Himeko-T (TU2481-077-17197708-03), Himeko -B "(TU2499-038-17197708-98).

The procedure for the preparation of gelled liquid and its injection using the pump unit CA-320 is described in patent RU No. 2358100, IPC E21B 43/26, publ. in bull. No. 16 dated 06/10/2009. As an additional example of the use of a gel-like fracturing fluid, a structured hydrocarbon gel-like composition for hydraulic fracturing, described in RU patent No. 2043491, IPC E21B 43/26, publ. 09/10/1995.

Next, determine the amount of acid injected into each of the intervals 2 ′, 2 ″, 2 ″ ′. The volume of acid is taken equal to 0.7-0.75 of the volume of the gel-like rupture fluid, i.e. V _to = (0.7-0.75) · 8 m ³ = 5.6-6 m ³ . Let us take the volume of injected into each interval 2 ′, 2 ″, 2 ″ ″ acid equal to 6 m ³ .

Any acid known as hydrochloric, hydrofluoric or others used in hydraulic fracturing to wedge a crack is used as the acid that acts as a proppant in cracks formed as a result of fracturing of a reservoir by a gel-like fluid. For example, 15% hydrochloric acid inhibited according to TU2122-205-00203312-2000 (manufactured by OJSC Kaustik, Sterlitamak, Republic of Bashkortostan, Russia) is used as the acid.

The pipe string is moved to the interval of the productive formation closest to the bottom of the well with low filtration-capacitive properties and the mechanical packer 5 is planted (see Fig. 1) in the horizontal wellbore 1.

Using a pumping unit CA-320, a gelled fracture fluid is pumped through a pipe string 3 through nozzles 7 of a hydromonitor nozzle 6 and perforation channels 9 ′ are formed (see FIGS. 1 and 3) in the interval 2 ′ of the reservoir with low reservoir properties of the rocks.

Without stopping the injection of the gelled fracturing fluid into the pipe string 3, the injection pressure of the gelled fracturing fluid is brought to a pressure corresponding to the hydraulic fracturing pressure, i.e. to R _Tr = 20 MPa. In this case, the injection pressure of the gelled fracturing fluid (P _Tr = 20 MPa) drops by 30% on the pressure gauge of the pumping unit, i.e. up to 20 MPa - (20 MPa × 30%) / 100% = 14 MPa, which indicates hydraulic fracturing in the interval 2 ′. Further, without stopping the injection of the gelled fracturing fluid into the pipe string 3 to develop a crack 10 ′, into the annular space 11 of the well using a second pumping unit, for example, CA-320 (not shown in FIGS. 1, 2, 3), from the wellhead acid is injected with a variable flow rate - Q _k = 3-5 m ³ / min (see FIGS. 1 and 3), which maintains the pressure P _Tr (crack formation) for the development of a 10 ′ crack (see FIG. 1), while the gel-like fracturing fluid along the pipe string 3 is carried out under pressure (P _tr ) 10% less than the fracturing pressure in the inte vale 2 ′ of the oil-saturated part of the reservoir, i.e. under pressure P _Tr = 20 MPa (20 MPa × 10%) / 100% = 18 MPa.

The hydromonitor nozzle 6 initially forms several (depending on the number of nozzles 7 of the hydromonitor nozzle) perforation channels 9 ′ (see FIG. 3) of limited depth (15-30 cm) in the interval 2 ′ of the reservoir with low reservoir properties of the rocks.

The flow rate of the fracture fluid flowing into the perforation channel 9 ′ is high and decreases sharply at the end of the perforation channel 9 ′, therefore, the pressure p _n (see FIG. 3) at the outlet of the nozzle 7 of the hydraulic nozzle 6 at the beginning of the perforation channel 9 ′ is less, than the pressure p _at the end of the perforation channel 9 ′, i.e. p _n <p _in .

The injection pressure of the gelled fracturing fluid P _Tr (see Fig. 2) in the pipe string 3 is maintained at a level 10% lower than the fracturing pressure in the interval 2 ′ of the reservoir with low reservoir properties and corresponds to the cracking pressure (18 MPa), therefore in the interval 2 ″ a fracture 10 ′ of hydraulic fracturing develops.

Acid from the annular space 11 (see Fig. 3) due to the formation of a rarefaction region (low pressure p _n ) in the annular space 11 opposite the nozzle 7 of the nozzle 6 is entrained in the perforation channel 9 ′ together with the gelled fracturing fluid and then gets into the crack 10 ′ (see figures 1 and 2), where it wedges in the process of cracking. Unpack the mechanical packer 5 and move the pipe string 3 from the bottom 8 to the mouth to the next interval 2 ″ oil-saturated part of the reservoir with low filtration and capacitive properties to form perforation channels 9 ″ and hydraulic fracturing with formation and development of 10 ″ cracks (see Fig. 2), after which the technological operations, starting with the landing of the mechanical packer 5 and ending with its unpacking, are repeated.

In a similar way, 9 ″ ″ perforation channels are formed and hydraulic fracturing is carried out with formation and development of 10 ″ ″ cracks in the interval 2 ″ ″ of the productive formation with low reservoir properties of the rocks. In contrast to the prototype, the proposed method has high accuracy of creating cracks in the reservoir in the desired interval.

The proposed method of multiple hydraulic fracturing in an open borehole of a horizontal well is simple to use and allows to reduce the duration of hydraulic fracturing by eliminating technological operations for casing and cementing the casing in a horizontal wellbore, as well as hydromechanical perforation, allows to increase the efficiency of hydraulic fracturing by performing perforation channels with a length of 15-30 cm through the hydraulic nozzle in the open hole of a horizontal well with leduyuschim conducting hydraulic fracturing as well as increase the reliability of fracturing by applying a mechanical packer by clipping productive intervals of the formation.

Claims (1)

A method of multiple hydraulic fracturing in an open borehole of a horizontal well, comprising drilling a horizontal wellbore in the oil-saturated part of a producing wellbore, lowering a string of pipes into the well, forming perforation channels and cracks using hydraulic fracturing in a horizontal wellbore sequentially, starting from the end farthest from the axis of the vertical wellbore communicating the horizontal wellbore with the reservoir, while during the next hydraulic of the fracture, the section through which hydraulic fracturing is performed is isolated from the rest of the column by a packer, characterized in that during the drilling of the horizontal wellbore, the reservoir properties of the rocks are determined and intervals of the reservoir with low reservoir properties of the rocks are identified at the end of drilling a wellhead with a mechanical packer is installed at the wellhead at the lower end of the pipe string, and a water monitor nozzle with nozzles is placed above, the pipe string is lowered into the well so that Both nozzles of the hydraulic nozzle were located opposite the interval of the oil-saturated part of the formation closest to the bottom of the well, with low filtration and capacity properties, the mechanical packer was planted in the horizontal well, the process fluid was pumped from the wellhead and the fracturing pressure was determined in the specified horizontal horizontal interval the trunk, unpack, move the pipe string from the bottom to the mouth to the next interval of the oil-saturated part of the reservoir with low f reservoir properties, similarly determine the fracture pressure of rocks in other intervals of the oil-saturated part of the reservoir with low reservoir properties, then determine the volumes of gelled fracturing fluid and acids for each interval of the oil-saturated part of the reservoir with low reservoir properties, then move the pipe string into the interval of the reservoir closest to the bottom of the well, with low filtration-capacitive properties, produce a landing mechanical packer, with The wells of the well, using a pumping unit, pump the gelled fracturing fluid through the pipe string through nozzles of the hydraulic nozzle and form perforation channels, after which, without stopping the injection of the gelled fracturing fluid through the pipe string, they create hydraulic fracturing pressure corresponding to this interval of the oil-saturated part of the reservoir after falling the injection pressure of the gelled fracturing fluid in the pipe string forms hydraulic fractures by 30%; for this, they pump into the annular space of the well acid with a variable flow rate ensuring the injection pressure of the gelled fracturing fluid along the pipe string is 10% less than the hydraulic fracturing pressure for a given interval of the oil-saturated part of the reservoir, unpack and move the pipe string from the bottom to the mouth to the next interval of the oil-saturated part of the formation with low filtration capacitive properties of rocks for the formation of perforation channels and hydraulic fracturing with the formation and development of cracks.

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