RU2660683C1 - Method of developing low-permeability oil fields based on the use of horizontal wells with longitudinal fractures of hydraulic fracturing - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention relates to oil industry and can be applied to development of purely oil fields with low permeability of the petroleum rock. Method includes drilling of horizontal production wells in a row layout and completion with the use of multi-stage hydraulic fracturing of the MSGRP layer, creation of a system for maintaining reservoir pressure of PPD by flooding method. In parallel to the rows of horizontal production wells, alternating through one row, rows of horizontal injection wells are drilled. Orientation of all horizontal parts of the well bores is carried out in the direction of the maximum horizontal stresses of the formation, which makes it possible in the MSGRP process to obtain longitudinal fracture fractures. Moreover, the MSGRP on all wells is performed using Newtonian fracturing fluid of viscosity less than 35 mPa×from, length of the horizontal part of the wellbore is 1,600 m and more, the number of ports of the MSGRP is 12 units and more, the specific amount of proppant up to 20 tons per port. As a proppant lightweight proppants with a bulk density of less than 1,400 kg/m³ are used, and injection of the displacing agent to maintain formation pressure is carried out at a bottomhole pressure not exceeding the fracture pressure of the formation, which allows to control development of cracks in conditions of easily tearing tire with the purpose of excluding the connection of the main formation with the overlying aquifer.

EFFECT: technical result is to increase oil recovery.

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Description

The invention relates to the oil industry and can be used to develop purely oil deposits with low permeability of oil rock up to 1-2 mD (10 ^-3 μm ² ) and less and with a tire composed of brittle rocks.

There is a method of developing low-permeability reservoirs based on areal five-, seven-, nine-point systems for locating production and injection wells (Fazlyev R.T. Areal flooding of oil fields. - M .: Nedra, 1979, p. 7, 47-49).

The disadvantage of this technical solution is the use of directional wells (NNS). Oil wells are wells with vertical primary development, the use of which on low-permeability reservoirs is unprofitable due to low initial oil production rates and low oil recovery coefficient. The low technological efficiency of this development method is due to the extremely low permeability of the reservoir and the high lithological heterogeneity of such formations both laterally and in section. In such conditions, the initial opening of the oil reservoir by the vertical wellbore does not allow for acceptable development coverage of the facility. In conditions of extremely low reservoir permeability, the area of contact between the well and the formation is of decisive importance for development efficiency.

There is a method of developing low-permeability formations using horizontal technologies, according to which, on horizontal wells drilled in the direction of minimum horizontal stress of the formation, multistage hydraulic fracturing (MSHF) is performed - several hydraulic fracturing fractures (hydraulic fracturing) performed in different sections of the horizontal wellbore (E. Sayapov, IR Diyashev and AV Brovchuk "Application of Horizontal Wells with Multiple Hydraulic Fractures for the Development of Low Permeability Oil Reservoir in Western Siberia", paper IPTC 13395 presented at the International Petroleum Technology Conference held in Doha, Qatar, December 7-9, 2009).

The disadvantage of this technical solution is the low technical and economic efficiency, which is associated with a high rate of decline in oil production and a low value of the final oil recovery coefficient due to the lack of maintaining reservoir pressure and the process of oil displacement.

Closest to the proposed invention is a method for developing low permeability reservoirs, including drilling horizontal production wells and organizing a system for maintaining reservoir pressure (Patent No. 2515628 RU). The specified method is adopted by us as a prototype.

The method involves drilling horizontal production wells with in-line placement and orientation of horizontal shafts in the direction of minimum horizontal formation stresses and performing multistage hydraulic fracturing on horizontal production wells. In parallel with the rows of producing horizontal wells with alternating through one row, rows of directional injection wells are drilled with hydraulic fracturing at all wells, while on injection wells located opposite the middle of the horizontal length of the horizontal well of producing wells, hydraulic fracturing and commissioning are carried out at the stage when neighboring wells have already been put into operation: the closest producing horizontal wells in neighboring rows are for production, the closest injection wells in a row are for injection, and the liquid is directional injection wells are at bottomhole pressure in excess of the fracture pressure.

The known method has several disadvantages:

- the use of directional wells with vertical opening of the formation as injection wells predetermines high pressure gradients during injection of the displacing agent into the formation, which, together with high natural heterogeneity and hydraulic fracturing, determines the high probability of water breakthrough from injection wells into production wells, and, therefore, low coverage and low waterflooding efficiency in general;

- to ensure the required injectivity of injection wells, injection pressures exceeding hydraulic fracturing pressures are used, which does not allow reaching an acceptable coefficient of formation coverage by water flooding and often leads to premature flooding of horizontal production wells with multi-stage fracturing;

- lack of universality of use. This method is not applicable to objects with easily breaking tires, composed of rocks that are fragile by the geomechanical characteristics and separating the oil object from the overlying aquifer, because of the high probability of fracture fracturing in the aquifer.

The objective of the proposed method is to provide high oil recovery for conditions of low permeability and undersaturated reservoirs and to prevent fracturing of hydraulic fractures in the overlying aquifer due to the increased fragility of the tire rocks.

This problem is achieved by the fact that in the method of developing low-permeability oil deposits, based on the use of horizontal wells with longitudinal fractures of hydraulic fracturing, including drilling horizontal production wells according to the in-line layout, completing them using multi-stage hydraulic fracturing (MSHF) and creating a reservoir pressure maintenance system (PPD), according to the invention, parallel to the rows of producing horizontal wells, alternating through one row, drill rows of horizontal wells non-producing wells, while the orientation of all horizontal parts of the wellbores is carried out in the direction of the maximum horizontal stresses of the formation, which allows the fracturing to obtain longitudinal hydraulic fractures in the multi-fracturing process, and the multi-fracturing for all wells is performed using a Newton hydraulic fracturing fluid with a viscosity of less than 35 MPa × s, the length of the horizontal the borehole is 1600 m or more, the number of MSGRP ports is 12 units. and more, the specific amount of proppant material is up to 20 tons per port, lightweight proppants with a bulk density of less than 1400 kg / m ³ are used as proppant, and the displacing agent is injected into the reservoir through injection wells at a bottomhole pressure not exceeding the re-fracturing pressure formation, which together allows you to control the development of cracks in the conditions of easily torn tires in order to exclude the connection of the main layer with an overlying aquifer.

The proposed method involves drilling only horizontal production and injection wells, conducting multi-stage hydraulic fracturing, pumping water into injection wells and taking oil from production wells. Production and injection horizontal wells are placed in a straight line opposite each other with alternating through one row. This arrangement of wells allows to achieve a more stable front of oil displacement by injected water due to the action of the linear filtration factor. Completion of all wells is performed using MSHF. A feature of the proposed method is the fact that one production well accounts for one injection well, which improves the technical and economic efficiency of the proposed method, even taking into account the fact that horizontal wells are usually 1.5-2 times more expensive than deviated directed.

Orientation of horizontal wellbores is carried out in the direction of the maximum horizontal stresses of the reservoir, which allows for longitudinal fracturing in the fracturing process.

This approach makes it possible to minimize the distance between the rows of production and injection wells up to 300 m, the distance between the rows depends primarily on the average permeability of the formation, thereby creating an active development system using water flooding at facilities with extremely low permeability and at the same time ensure a long anhydrous period of operation producing wells. The horizontal parts of the wells are drilled with an increased length of 1600 m or more, with the number of MSGRP ports increased to 12 units. and more. The implementation of this complex of technological solutions allows providing coverage of the reservoir with the development of fewer wells.

According to the proposed method, the efficiency of producing oil deposits with low permeability reservoirs is increased, the oil production rate and the specific recoverable oil reserves per well are increased, and the life of producing reserves and well construction costs is reduced.

The presence of new technological methods in the proposed development method and their combination with the known ones create favorable conditions for the development of low-permeability oil deposits, complicated by a tire composed of rocks of increased brittleness and separating the oil reservoir from the aquifer, based on the use of horizontal production and injection wells with longitudinal fractures .

In FIG. 1 shows a layout of production and injection wells according to the proposed method.

The diagram shows horizontal production wells - 1; horizontal injection wells - 2, multi-stage hydraulic fracturing cracks - 3, oil reservoir - 4.

In FIG. 2 and FIG. Figure 3 presents an example of a part of the geological section of the field and the copy from the correlation scheme: oil reservoir (oil reservoir) - 4; a tire made of impermeable brittle clay rocks, for example, a mixture of mudstones and siltstones - 5; aquifer - 6.

The method is as follows.

On the oil deposits in low-permeability reservoirs 4, complicated by a cover of brittle clay rocks 5 and an overlying aquifer 6, alternating rows of horizontal producing 1 and horizontal injection 2 wells are drilled alternating in the direction of the maximum horizontal stress of the formation. The length of the horizontal part of the wellbores is 1600 m or more. The length is determined by the degree of discontinuity of the productive formation, the presence of disjunctive disturbances in the formation, specific reserves per well, and ultimately the maximum extreme value of the economic efficiency of the entire field development project.

After drilling at all wells, MSHF is performed using Newtonian fluid with a viscosity of less than 35 MPa × s. The use of a fluid with a low viscosity and lack of structural properties eliminates an excessive increase in the height of the hydraulic fracture and its penetration into the overlying aquifer. The number of MSGRP ports is 12 units / well. and more depends on the length of the horizontal part of the well and on the optimal distance between hydraulic fractures. The approximation of hydraulic fracturing ports is advisable until the saturation point is reached (Karpov V.B., Parshin N.V., Sleptsov D.I., Moiseenko A.A., Ryazanov A.A., Golovatsky Yu., Petrashov O., Zhirov A. , Kurelenkova Yu., Ishimov I., Im P. Improving the development efficiency of a large TRIZ field in Western Siberia based on the experience of Canadian counterparts // SPE-182572-MS. 2016. p. 47). The specific amount of proppant material is up to 20 t / port. The restriction is associated with the need to prevent fracture fracturing in the overlying water-saturated formation, as well as the technical and economic indicators of hydraulic fracturing. As proppant material use lightweight proppants with a bulk density of less than 1400 kg / m ³ . According to the calculations, this bulk density corresponds to the conditions when the Newtonian hydraulic fracturing fluid provides the bearing and holding ability with respect to the proppant, which is important for successful hydraulic fracturing.

A working agent, water, is pumped through injection wells 2, and products are taken through production wells 1.

With such a development system (Fig. 1), the maximum involvement in the development of oil reserves of a low-permeability reservoir by section and area is ensured. The arrangement of wells in the direction of the maximum horizontal reservoir stress and the conduct of hydraulic fracturing contribute to the creation of longitudinal cracks relative to the horizontal wellbores, which significantly expands the possibilities of creating a further system for maintaining reservoir pressure by significantly reducing the risks of premature flooding of production wells and creating an active reservoir stimulation system as a result minimizing the distance between the rows of producing and injection horizontal wells in. The special technology of small-scale MSGRFs allows controlling the development of cracks in conditions of easily tearing tires in order to exclude the connection of the oil reservoir with the overlying aquifer.

In addition to increasing production rates and specific oil reserves per well, such a development system (Fig. 1) can significantly reduce the cost of production drilling by reducing the total number of wells due to the increase in the length of their horizontal part; ensure the effective operation of the RPM system; to exclude the breakthrough of injected water into the overlying horizon and to control the process of preventing the development of auto-fracturing cracks in overlying aquifers.

The method allows you to control the development of hydraulic fractures in conditions of easily tearing tires in order to exclude the connection of the main reservoir with an overlying aquifer. For this, a special approach is used to minimize the specific amount of proppant material per hydraulic fracturing port to 20 tons, use Newtonian fracturing fluid and use lightweight proppants with a bulk density of less than 1400 kg / m ³ as proppant.

In addition, the method provides for the preliminary conduct of a complex of studies of micro-hydraulic fracturing in one of the drilled vertical wells in seven intervals: one in a nearby aquifer, two in an impermeable bridge, two in a reservoir and two in a dense interval and adjustment based on its results of the technology and design of hydraulic fracturing, as well as operating modes of injection wells, refinement of the geometry of the generated fractures, changing the design of hydraulic fracturing, so as to obtain fractures of a greater half-length and eliminate read breakthrough cracks into an overlying aquifer.

An example of the application of the method.

Consider the object of development - an oil reservoir in low-permeability reservoirs with the following geological and physical characteristics.

The oil reservoir is composed of sandstones and siltstones. The type of collector is porous. The deposit is confined to a lithologically shielded trap. The dimensions of the deposit in all directions exceed 5 km. VNK reservoir exploration wells are not opened. The depth of the formation is 2300 m, the effective oil-saturated thickness is 5.4 m, the sandiness coefficient is 0.72 parts, the dissection is 3.2 units, the permeability coefficient is 0.87 μm ² × 10 ^-3 , and the porosity coefficient is 0.18 fractions of unit, oil saturation coefficient - 0.38 fractions of unit, initial reservoir pressure - 22 MPa. The oil is light in density, with insignificant viscosity, paraffinous, low-sulfur, slightly resinous. Oil viscosity in reservoir conditions is 0.8 MPa × s, oil density in reservoir conditions is 738 kg / m ³ , gas saturation pressure is 12.1 MPa, gas factor is 101 m ³ / t, oil volume factor is 1.244 units.

For the reservoir under consideration, regional directions of the maximum and minimum horizontal stresses of the formation are determined using the results of cross-dipole acoustic logging carried out in at least three wells and confirmed (refined) by microseismic monitoring data performed during the first hydraulic fracturing of exploratory wells (Kazbulatov I .G., Rubtsova A.V., Yunusov PP, Veremko N.A., Volyanskaya V.V. Multistage hydraulic fracturing in horizontal wells in combination with microseismic nitoring and cross-dipole acoustic logging // Oil industry. - 2014. - No. 9. - S. 93-95).

Having specified the directions of these stresses, the oil reservoir is drilled according to the development scheme shown in Fig. 1: horizontal parts of the shafts of production and injection wells are placed in the direction of maximum horizontal formation stresses.

All production and injection wells are drilled with a horizontal part of the bore of 1600 m, with a distance between rows and horizontal wells in a row of 390 m. A multi-stage longitudinal hydraulic fracturing is performed at these wells, which includes a special completion scheme: launching an uncemented liner assembly equipped with 12 annular packers (ZP), which serve to separate the 12 stages of hydraulic fracturing and mechanical isolation (if necessary) of the intervals of fluid inflow or injection during the subsequent operation of the well of water, the number of filling zones corresponds to the length of the horizontal part of the wells - 1600 m and corresponds to the average geological and physical characteristics of the object.

Isolation of the previous hydraulic fracturing stage from the current one is carried out through controlled couplings installed in the liner by means of lowering flexible tubing with a special clutch control device - a hydromechanical key using the Auto J-Slot mechanism.

This approach reduces the construction and development of a horizontal well. A distinctive feature of the technology used in comparison with other systems is the use of mechanically controlled couplings and a packer, which is activated by a coiled tubing string. Such equipment allows for an almost unlimited number of hydraulic fracturing stages in one round-trip operation according to the bottom-up principle. After hydraulic fracturing in the first zone, the packer is deactivated using a hydromechanical key. Further, the whole layout of downhole equipment moves up to the next port, where it opens. Then the packer is activated below the newly opened port to cut off previously processed intervals.

The advantage of the technology used in comparison with others lies in the use of mechanically controlled couplings, which allow disconnecting individual ports without the use of grouting materials. These ports can be reopened. Such equipment makes it possible to carry out other technological operations at individual intervals, including during the further operation of the well, subsequent work on opening or blocking ports, for example, to stimulate flow, including repeated hydraulic fracturing. In addition, restrictions on the size of the outer diameter of geophysical instruments are removed, which greatly simplifies research and increases their information content (Kovalev S.A., Knyazev M.A., Sharipov R.F., Parshin N.V. An integrated approach to conducting multi-stage hydraulic fracturing Coiled tubing // Coiled tubing time, hydraulic fracturing time. 2016. - No. 1. - P. 32-35).

According to this technological scheme, 12 longitudinally hydraulic fracturing are produced. In FIG. Figure 1 schematically shows the relative directions and geometry of the development of fractures of the MSHF obtained from the results of three-dimensional geological, geomechanical and hydrodynamic modeling of the MSHF process in the wells of this reservoir. Fracturing MSGRP will occur in the direction of the maximum horizontal stress of the reservoir, and therefore in the direction of the horizontal wellbores. In the conditions of fragile clayey rocks overlapping the oil reservoir, the hydraulic fracture opens this tire, which separates the oil reservoir from the aquifer. A small proppant volume and the Newtonian type of hydraulic fracturing fluid, characterized primarily by low viscosity, contribute to the fact that proppant fixes the crack only in the oil-saturated part of the reservoir. Technically, the operation of such MSGRP is possible only with the use of light proppants with a density of less than 1400 kg / m ³ . Thus, MSHF is carried out at production and injection horizontal wells.

Prior to the industrial introduction of MSHF technology, at the initial stage of selecting its parameters in one of the drilled vertical wells, a set of micro-hydraulic fracturing studies is carried out in seven intervals: one in a nearby aquifer, two in an impenetrable bridge, two in a reservoir and two - in the dense underlying interval. These studies allow us to clarify the technology and design of hydraulic fracturing to obtain cracks of greater half-length and exclude their breakthrough into the overlying aquifer. The results of micro-hydraulic fracturing are subsequently used to justify the operating modes of injection wells.

After development, horizontal production wells are launched into production. Designed injection horizontal wells (HW) are also processed for oil and transferred for injection one year after the start of operation.

Claims (1)

A method of developing low-permeability oil deposits based on the use of horizontal wells with longitudinal hydraulic fractures, including drilling horizontal production wells according to an in-line arrangement, completing them using multi-stage hydraulic fracturing of the MSGRP and creating a pressure maintenance method for reservoir pressure maintenance by the waterflooding method, characterized in that the rows of producing horizontal wells alternating through one row drill rows of horizontal injection wells, at In this case, the orientation of all horizontal parts of the wellbores is carried out in the direction of the maximum horizontal stresses of the formation, which makes it possible to obtain longitudinal hydraulic fractures during the hydraulic fracturing process, and the hydraulic fracturing for all wells is performed using a Newtonian hydraulic fracturing fluid with a viscosity of less than 35 MPa × s, the horizontal part of the wellbore m and more, the number of MSGRP ports is 12 units. and more, the specific amount of proppant material is up to 20 tons per port, lightweight proppants with a bulk density of less than 1400 kg / m ³ are used as proppant, and the displacing agent is injected to maintain reservoir pressure at a bottomhole pressure not exceeding the pressure of repeated fracturing , which allows you to control the development of cracks in conditions of easily tearing tires in order to exclude the connection of the main layer with an overlying aquifer.

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