Method of developing multi-layered oil deposit using hydraulic fracturing

Abstract

FIELD: oil industry.SUBSTANCE: invention relates to the field of development and operation of oil fields, in particular to methods of increasing oil recovery by hydraulic fracturing (HF) of injection wells. The method of developing an oil deposit using HF includes extracting reservoir fluid through production wells, injecting a working agent through an injection well, and performing HF in the injection well. A section is selected with a decrease in compensation for reservoir fluid extraction by injecting a working agent, or with an injection well that has a recorded lack of injectivity, or with a decrease in the volume of working agent injection. Based on microseismic and cross-dipole data, the direction of maximum horizontal stress, the direction of hydraulic oscillations, and their length are determined. At least one responsive production well is identified. Using specialized fracturing simulators, the parameters of the fracturing crack are calculated. The design length of the hydraulic oscillation propagation is calculated. A test fracturing is performed in the injection well by injecting a mixture of cross-linked gel with proppant, and if there are deviations, the parameters of the main fracturing are adjusted. The main fracturing is performed by injecting a mixture of cross-linked gel with proppant, followed by flushing the injection well with a surfactant solution. After that, the injection well is kept closed until the cross-linked gel mixture with proppant is completely destroyed. The fracturing equipment is removed, the tubing is lowered, and the working agent is re-injected.EFFECT: invention ensures an increase in the injection well's capacity, a more complete displacement of the reservoir product by the working agent, and, as a result, a significant increase in the production well's flow rate.1 cl, 2 dwg, 1 tbl, 1 ex

Description

[0001] The invention relates to the field of development and operation of oil fields, in particular to methods for increasing oil recovery by hydraulic fracturing (HF) of injection wells.

[0002] A method of hydraulic fracturing of a formation in a well is known (RU patent No. 2522366, IPC E21B 43 / 267, IPC C09K 8 / 80, published on 10.07.2014, Bulletin No. 19), including perforation of the well walls in the formation interval with channels of a depth not less than the length of the stress concentration zone in the rocks from the wellbore, lowering a string of pipes with a packer, setting the packer above the roof of the perforated productive formation, pumping gelled fracturing fluid into the sub-packer zone, filling the string with process fluid, determining the total volume of gelled fracturing fluid, creating hydraulic fracturing pressure in the sub-packer zone and squeezing gelled fracturing fluid with proppant into the resulting fracture of the formation, holding in the time required for the pressure to drop by 70%, unpacking and removing the packer with the pipe string from the well,Also, after determining the total volume of gelled fracturing fluid, gelled fracturing fluid - linear gel - is pumped into the well through the pipe string until fractures are formed in the formation, the remaining volume of gelled fracturing fluid after the formation of fractures in the formation is divided into two parts: cross-linked gel and linear gel, then cyclically alternately pumping first the linear and then the cross-linked gel with the addition of proppant in 3-5 cycles, with the linear gel being pumped in equal portions at a flow rate of 4-6 m, 3 / min and proppant concentration of 400 kg / m3 3 , and the cross-linked gel is injected with a stepwise increase in injection volume from 3 to 7 m 3 with a flow rate of 1-2 m 3 / min and proppant concentration of 1200 kg / m3 3, while glass fiber is added to the last portions of the linear and cross-linked gels with proppant in an amount of 1.5% of the proppant weight in each of the last portions of the linear and cross-linked gels and they are pumped into the pipe column, then they are forced into the formation with process fluid and held for the time required for the pressure to drop by 70%, unpacking is performed and the packer with the pipe column is removed from the well.

[0003] The disadvantage of this method is that

[0004] - there is a risk of a “stop” occurring, which prevents further advancement of portions of linear and cross-linked gel, due to the formation of a hydraulic fracturing crack (HF) along the length and width, in which further expansion becomes impossible due to the specific geological conditions;

[0005] - a decrease in injectivity occurs in the area of ​​the well perforations due to the penetration of fracturing fluid into the central part of the crack and the subsequent settling of fiberglass particles immediately after the perforation zones.

[0006] A method is known for developing an oil reservoir using hydraulic fracturing (RU patent no. 2459938, IPC E21B 43 / 20, published on 27.08.2012, Bulletin no. 24) including oil extraction through production wells, pumping a working agent through injection wells and carrying out hydraulic fracturing in the wells, while for carrying out hydraulic fracturing in the wells, reservoir zones with high reservoir pressure, with large oil reserves and a grid density of at least 1.5 hectares / well are selected, in the selected zones, production wells are selected with a skin factor that has changed during the development from "-" to "+", with a water cut of no more than 40%, an injection well is determined with which the selected production wells react, hydraulic fracturing is carried out in a certain injection well, after which hydraulic fracturing is carried out in the selected production wells.

[0007] The disadvantage of this method is that without considering the length of the planned fracture, there is a risk of it significantly exceeding the collateralized zone. This will lead to the fracture penetrating into the immediate filtration area of ​​the production wells, causing a so-called "dagger" breakthrough of the injected fluid, and a sharp increase in the water cut of the latter. If the fracture is insufficient in length, it will not be able to penetrate the barrier of the collateralized zone in the injection well, resulting in ineffective injection of the working fluid, accompanied by an increase in pressure and a possible breakthrough through high-permeability zones.

[0008] The closest in technical essence is the method of hydraulic fracturing of a formation at a late stage of production (patent RU No. 2733561 C2, IPC E21B 43 / 26, published 05.10.2020, Bull.No. 28), including the extraction of reservoir products through production wells with control of the volumes of extraction of reservoir products, the injection of a working agent through injection wells with an excess of injection volumes over extractions, the implementation of, when the water cut of the extracted products in injection wells increases, the isolation of absorption zones and the most permeable sections of the formation with a colmatation composition and the implementation of hydraulic fracturing of the formation - HF in the well, also determining the average length of the fracture during HF in the formation by geophysical studies, after isolation with a colmatation composition, a material stable in time is pumped into the injection well to form a screen with a radius of no more than 1 / 4 and no less than 1 / 8 of the average length of the fracture during HF, and HF is carried out in the injection well after the hardening of the cement slurry.

[0009] A disadvantage of this method is the lack of control over the fracture growth trajectory. Without specialized technologies to manage this process, a newly created fracture, under the influence of maximum horizontal stress, will likely develop parallel to this stress, deviating from the optimal direction. This can lead to the fracture being directed into unproductive or isolated hydrodynamic zones, or developing through existing, highly flushed sections of the formation. Both options preclude the desired increase in injectivity in the injection well and, consequently, a significant increase in flow rate in the production well.

[0010] The technical objective of the proposed invention is to increase the injectivity in an injection well, more completely displace the reservoir product with a working agent and, as a consequence, significantly increase the flow rate in a production well in an oil reservoir area.

[0011] The technical problem is solved by a method for developing a multi-layer oil reservoir using hydraulic fracturing, which includes the extraction of formation fluid through production wells with controlled extraction volumes, the injection of a working agent through an injection well, and hydraulic fracturing (HF) in the injection well.

[0012] What is new is that an area of ​​an oil reservoir is selected with a decrease in the compensation of formation fluid extraction by injection of the working agent to a level of less than 100%, or the presence of at least one injection well with a recorded lack of injectivity or a decrease in the volume of injection of the working agent into the injection well by 30-50% over the past 12 months, based on the data of microseismic and cross-dipole studies, the predominant direction of the maximum horizontal stress in the area of ​​the oil reservoir is established, the direction of hydraulic oscillations and their length, coinciding with the length of the propagation front of microseismic activity caused by the formation of a hydraulic fracture, are determined, while at least one reacting production well with a decrease in flow rate due to low values ​​​​of formation and bottomhole pressures over a long period is identified,located in the zone of reduced reservoir pressures around the bottomhole zone of the well and, if possible, oriented parallel to the direction of maximum horizontal stress, using specialized hydraulic fracturing simulators, the parameters of the hydraulic fracturing fracture for the injection well are calculated so that the length of the fracture exceeds the size of the colmatated zone by at least 30%, but does not exceed half the distance between the injection and the reacting production wells, the design length of propagation of hydraulic oscillations is calculated as the product of the half-length of the hydraulic fracturing fracture by the hydraulic oscillation coefficient, using the isobar map it is checked that the calculated design length of propagation of hydraulic oscillations emanating from the injection well intersects the zone of reduced reservoir pressure of the reacting production well,which is 15% lower than the reservoir pressure of the injection well itself and intersects the specified zone with reduced reservoir pressure of at least 5% of the proper propagation length of hydraulic oscillations, a test hydraulic fracturing is performed in the injection well with the injection of a mixture of cross-linked gel with proppant of a fraction no larger than 20 / 40 in a volume of at least one ton and, in case of significant deviations, changes are made to the parameters of the main hydraulic fracturing, the main hydraulic fracturing is performed with the injection of a mixture of cross-linked gel with proppant of a fraction of at least 16 / 30 at a concentration of the said mixture of at least 800 kg / m3, 3 After completion of the main hydraulic fracturing, the injection well is flushed with a surfactant solution, while the injection well is kept closed for the time required for the complete destruction of the mixture of cross-linked gel with proppant, the hydraulic fracturing equipment is removed, the tubing is lowered, and then the injection of the working agent is resumed.

[0013] Figure 1 shows the results of microseismic studies at an injection well during the creation of a hydraulic fracture in rock formations during hydraulic fracturing (HF). The propagation of the microseismic activity front (green field) is used to determine the direction and propagation length of the hydraulic vibrations that resulted from the fracture creation during HF.

[0014] Fig. 2 shows an isobar map of an oil reservoir area.

[0015] The method is carried out in the following sequence.

[0016] Select an area of ​​the oil reservoir (Fig. 1, 2) where formation fluid is extracted through production wells with controlled withdrawal volumes and a working fluid (e.g., bottomhole, fresh water, etc.) is injected through an injection well. In the selected area, a decrease in the compensation of formation fluid (e.g., oil) withdrawal by injecting the working fluid to a level of less than 100% is detected, or at least one injection well is identified with a recorded lack of injectivity or a decrease in the volume of working fluid injected into injection well 1 by 30–50% over the past 12 months, which indicates a high probability of the formation of colmatated zones in the bottomhole formation zone (BFZ).Based on data from previously conducted microseismic and cross-dipole studies, the predominant direction of maximum horizontal stress in the oil field is established (for example, for the Minnibaevskaya area of ​​the Romashkinskoye field, it is a southwest / northeast direction (strike azimuth 50° / 230°). The direction of hydraulic oscillations and their length L are determined. напр. , which coincides with the length of the propagation front of microseismic activity 2 caused by the formation of a hydraulic fracturing crack (HF) (Fig. 1). Length L напр. is calculated as the length of the hypotenuse of a right triangle, where the hypotenuse is the line of microseismic activity 3, and the legs of the triangle (for example, 340 m and 306 m) (not shown in the figure) are formed by the projections of the lower and upper boundaries 4 of the line of microseismic activity 3 onto the horizontal and vertical coordinate axes. The coefficient of hydraulic oscillations K is calculated гк, which is the ratio of the length L напр. hydraulic fluctuations (for example, 457 m) to the crack length L трещ. GRP (for example, 140 m) and is K гк= 3.3. At least one reacting production well 5 is identified in the same area (Fig. 2), characterized by a decrease in flow rate due to low values ​​of formation and bottomhole pressures over an extended period (e.g. 5 months), with the formation of zones with reduced formation pressure around the near-wellbore zone (BWZ) and, if possible, oriented parallel to the direction of maximum horizontal stress. Using specialized hydraulic fracturing simulators (e.g. RN-GRID, FracCADE, etc.), the parameters of the hydraulic fracture for injection well 1 are calculated such that the length of the hydraulic fracture exceeds the size of the colmatated zone by at least 30%, but does not exceed half the distance between injection well 1 and the reacting production well 5. This will minimize the risk of premature breakthrough of the injected working agent into the reacting production well 5 and increase the efficiency of formation fluid (e.g. oil) production.The direction of propagation of hydraulic vibrations is determined and its design length L is calculated. напр.(пр.) 6 equal to the product of the half-length of the hydraulic fracture by the hydraulic oscillation coefficient K гк . Using the isobar map of the oil reservoir section where hydraulic fracturing is planned, they check that the calculated design length L напр.(пр.)6 The propagation length of hydraulic oscillations emanating from injection well 1 intersects the zone of reduced reservoir pressure of the reacting production well 5, which is 15% lower than the reservoir pressure of injection well 1 itself, and intersects said zone of reduced reservoir pressure by at least 5% of the proper propagation length of hydraulic oscillations, ensuring the effective redistribution of the flow of the injected working agent and the involvement of previously undrained sections of the productive formation in the development, increasing the production of formation fluid. A test hydraulic fracturing is performed in injection well 1 in accordance with the instructions for conducting hydraulic fracturing established by the oil producing company, with the injection of a mixture of cross-linked gel with proppant of a fraction no larger than 20 / 40 in a volume of at least one ton, to confirm the conformity of the designed parameters of the hydraulic fracture with the actual results obtained during the test hydraulic fracturing.If significant deviations are detected, appropriate adjustments are made to the main hydraulic fracturing parameters. The main hydraulic fracturing is performed in injection well 1 in accordance with the oil company's hydraulic fracturing instructions, injecting a cross-linked gel / proppant mixture with a minimum fraction of 16 / 30. The concentration of the injected cross-linked gel / proppant mixture reaches at least 800 kg / m3. 3After completion of the primary hydraulic fracturing process, injection well 1 is flushed with a surfactant solution (e.g., ML-81B, ML-80B, etc.) to remove residual gel, proppant, and other contaminants, improve permeability, and restore well injectivity. The process concludes with shutting down the hydraulic fracturing fleet's pumping equipment and recording the wellhead pressure drop in the hydraulic fracturing fleet's control room. Injection well 1 is kept shut in for the time required for complete destruction of the cross-linked gel-proppant mixture (e.g., at least 4 hours), the hydraulic fracturing equipment is removed, the tubing is lowered, and hydraulic fluid injection is resumed.

[0017] Example of the method implementation.

[0018] We selected an area of ​​the Romashkinskoye oil reservoir with productive formations D0 and D1 (Fig. 2). We identified injection well No. 111*, in which a decrease in daily injection from 127 m was recorded over the past three months. 3 / day up to 81 m 3 / day. Based on the results of previously conducted microseismic and cross-dipole studies, the predominant direction of maximum horizontal stress in the oil reservoir section of the Minnibaevskaya area of ​​the Romashkinskoye field was determined to be southwest / northeast. In the same area, two reacting production wells, No. 2222* and No. 3333*, were identified, in which over the course of 5 months, at well No. 2222*, the bottomhole pressure decreased from 6.6 MPa to 4.9 MPa and the reservoir pressure from 16.6 MPa to 10.3 MPa, and at well No. 3333*, the bottomhole pressure decreased from 7 MPa to 5.2 MPa and the reservoir pressure from 16.2 MPa to 10.4 MPa, and, accordingly, the flow rate of reservoir products decreased, while the distance between the bottomholes of injection well No. 111* and the nearest reacting production well No. 2222* is 380 meters, and to No. 3333* it is 560 meters.Using the RN-GRID simulator, we calculated the half-length of a hydraulic fracture in injection well No. 111*, which is 74 meters long and does not reach the drainage zone of the responding production well. With a half-length of 74 meters, the hydraulic oscillation direction length is L. напр. equal to 244 m, partly intersecting a zone of reduced pressure. A test hydraulic fracturing was performed in injection well No. 111* in accordance with the hydraulic fracturing instructions established by the oil producing company. A mixture of cross-linked gel with 20 / 40 mesh proppant was injected in a volume of 1 ton. The fracture parameters planned in the design were compared with the actual fracture parameters obtained during the test hydraulic fracturing, where the planned fracture half-length was only 66 m. To achieve the planned fracture half-length of 74 m, the fracturing fluid volume of the main hydraulic fracturing process was increased from 15 m 3 up to 20 m 3 (buffer stage) and reduced the rate of injection of fracturing fluid for the main hydraulic fracturing from 3 m 3 / min up to 2.8 m 3 / min. Next, the main hydraulic fracturing was performed in injection well #111* in accordance with the hydraulic fracturing instructions established by the oil producing company, injecting 10 tons of a cross-linked gel mixture with 16 / 30 mesh proppant, with a half-length of 74 m for the fracture being formed in injection well #111*. After completion of the main hydraulic fracturing, injection well #111* was flushed with ML-81B surfactant solution. The hydraulic fracturing fleet's pumping equipment was then stopped, and the wellhead pressure drop was recorded in the fracturing fleet's control room. Injection well No. 111* was shut down for 6 hours to destroy the fracturing fluid, the hydraulic fracturing equipment was raised, the tubing was lowered, and then water injection was resumed.

[0019] As a result of applying the method, the performance indicators of wells #111*, #2222*, and #3333* improved (table). The injectivity of injection well #111* increased. Additional oil production as a result of hydraulic fracturing at injection well #111* from reacting production wells #2222* and #3333* amounted to 1,210 tons.

[0020] Table. Results of the implementation of the method for developing a multi-layer oil reservoir using hydraulic fracturing

[0021] Indicators Injection well No. 111* Reactive production well No. 2222* Reactive production well No. 3333* it was before using the method it became after using the method it was before using the method it became after using the method it was before using the method it became after using the method Daily injection, m3 / day 81 197 Bottomhole pressure, MPa 4,9 8,5 5,2 6,1 Water content, % 83 76 75 80 Liquid flow rate, tons / day 18 26 85 106

[0022] The method of developing a multi-layer oil reservoir using hydraulic fracturing will increase the injectivity in the injection well, more complete displacement of the reservoir product by the working agent and, as a result, a significant increase in the flow rate in the production well.

Claims

A method for developing a multi-layer oil reservoir using hydraulic fracturing, including the extraction of formation fluid through production wells with controlled extraction volumes, injection of a working agent through an injection well and hydraulic fracturing of the formation (HF) in the injection well, characterized in that an area of ​​the oil reservoir is selected with a decrease in the compensation of formation fluid extraction by injection of a working agent to a level of less than 100%, or the presence of at least one injection well with a recorded lack of injectivity, or a decrease in the volume of injection of a working agent into an injection well by 30-50% over the past 12 months, based on data from microseismic and cross-dipole studies, the predominant direction of the maximum horizontal stress in the area of ​​the oil reservoir is established, the direction of hydraulic oscillations and their length, coinciding with the length of the propagation front of microseismic activity, are determined,caused by the formation of a hydraulic fracture, wherein at least one reacting production well is identified with a decrease in flow rate due to low values ​​of reservoir and bottomhole pressures over a long period, located in a zone of reduced reservoir pressures around the bottomhole zone of the well and, if possible, oriented parallel to the direction of the maximum horizontal stress, using specialized hydraulic fracture simulators, the parameters of the hydraulic fracture for the injection well are calculated so that the length of the fracture exceeds the size of the colmatated zone by at least 30%, but does not exceed half the distance between the injection and the reacting production wells, the design length of propagation of hydraulic oscillations is calculated as the product of the half-length of the hydraulic fracture by the hydraulic oscillation coefficient, using the isobar map it is checked that the calculated design length of propagation of hydraulic oscillations emanating from the injection well,intersects a zone with reduced reservoir pressure of the reacting production well, which is 15% lower than the reservoir pressure of the injection well itself, and intersects the said zone with reduced reservoir pressure of at least 5% of its own propagation length of hydraulic oscillations, perform a test hydraulic fracturing in the injection well with the injection of a mixture of cross-linked gel with proppant of a fraction no larger than 20 / 40 in a volume of at least one ton and, in case of significant deviations, make changes to the parameters of the main hydraulic fracturing, perform the main hydraulic fracturing with the injection of a mixture of cross-linked gel with proppant of a fraction of at least 16 / 30 at a concentration of the said mixture of at least 800 kg / m, 3After completion of the main hydraulic fracturing, the injection well is flushed with a surfactant solution, while the injection well is kept closed for the time required for the complete destruction of the mixture of cross-linked gel with proppant, the hydraulic fracturing equipment is removed, the tubing is lowered, and then the injection of the working agent is resumed.

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