A method and system for testing the performance of gas energized repeated fracturing of old wells

Abstract

The application discloses a kind of old well gas energy increasing repeated fracturing performance test method and system, belong to low permeability reservoir development field.Due to oil well production after a period of time, formation energy deficit, production declines, so before repeated fracturing, first inject liquid carbon dioxide to supplement energy;Through injection liquid carbon dioxide, under formation conditions, carbon dioxide and crude oil component form miscible phase front, supercritical fluid is extracted from crude oil heavier hydrocarbon, and constantly make displacement front gas concentration.Carbon dioxide and crude oil become miscible phase liquid, form single liquid phase, so that formation crude oil can be effectively displaced to production well, improve recovery factor.In fracturing, use liquid carbon dioxide to supplement formation energy, according to field construction, optimize carbon dioxide liquid energy increasing injection timing, injection mode, according to the formation pressure of target well and old fracture area calculate carbon dioxide energy increasing optimal dosage, provide theoretical basis for repeated fracturing to improve single well production research.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of low-permeability reservoir development and relates to an old well gas energy supplementing and repeated fracturing performance testing method and system. BACKGROUND

[0002] With the development of oil and gas field development, low-permeability reservoirs have become the main strategic resources. Due to the low permeability of the reservoir, it is difficult to establish an effective displacement pressure system under the economic limit well pattern, which leads to a significant decrease in production after a period of production. At present, repeated fracturing is carried out on the oil well with low degree of exploitation to restore the single well production. Energy is supplemented to the production layer before repeated fracturing to restore the formation pressure and maintain the level, so as to maintain high and stable production of the oil well and prolong the effective period of the measures.

[0003] At present, the main way to supplement the formation energy before repeated fracturing is to inject oil displacement fracturing fluid into the old perforated section of the oil well by mechanical isolation. The displacement fracturing fluid required for repeated fracturing energy supplement is obtained by calculating the energy loss of the formation according to the amount of produced liquid during the development period of the oil well. Due to the lack of water resources in some areas at present, the effect of repeated fracturing energy supplement on production increase is limited, which leads to low recovery rate and difficulty in meeting the fracturing demand. SUMMARY

[0004] The purpose of the present application is to solve the problem of low recovery rate caused by the limited contribution of the repeated fracturing energy supplement method to the production increase effect in the prior art, and to provide an old well gas energy supplementing and repeated fracturing performance testing method and system.

[0005] To achieve the above-mentioned purpose, the following technical solutions are adopted in the present application:

[0006] The old well gas energy supplementing and repeated fracturing performance testing method provided by the present application comprises the following steps:

[0007] Injecting liquid carbon dioxide into the old perforated section of the gas well, injecting liquid carbon dioxide into the preflush liquid stage of the repeated fracturing of the selected perforated section, and obtaining the oil well production fracture area and the oil well production fracture volume;

[0008] According to the oil well production fracture area and the oil well production fracture volume, the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore the formation pressure are obtained;

[0009] According to the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore the formation pressure, the amount of carbon dioxide channeling and the amount of carbon dioxide injection are obtained, and the repeated fracturing test is realized.

[0010] Preferably, liquid carbon dioxide is injected into each old perforated section, odd old perforated section or even old perforated section.

[0011] Preferably, when liquid carbon dioxide is injected into the first perforated section, a drawdown friction test is performed.

[0012] Preferably, the method for obtaining the amount of carbon dioxide adsorbed in the matrix is as follows:

[0013]

[0014] wherein, is the equilibrium pressure after injecting carbon dioxide, is the fracture area of the oil well production.

[0015] Preferably, the method for obtaining the amount of carbon dioxide used for restoring the formation pressure is as follows:

[0016]

[0017] wherein, is the initial fracture volume after fracturing.

[0018] Preferably, the method for obtaining the amount of carbon dioxide gas channeling and the amount of carbon dioxide injection is as follows:

[0019]

[0020]

[0021] wherein, is the amount of carbon dioxide adsorbed in the matrix, is the amount of carbon dioxide used for restoring the formation pressure.

[0022] The present application provides an old well gas energy enhancement repeated fracturing performance test system, comprising:

[0023] a carbon dioxide injection module, the carbon dioxide injection module is used for injecting liquid carbon dioxide in the old perforation section of the gas well, injecting liquid carbon dioxide in the preflush stage of the repeated fracturing in the selected perforation section, obtaining the fracture area of the oil well production and the fracture volume of the oil well production;

[0024] a parameter acquisition module, the carbon dioxide parameter acquisition module is used for obtaining the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used for restoring the formation pressure according to the fracture area of the oil well production and the fracture volume of the oil well production;

[0025] a parameter processing module, the parameter processing module is used for obtaining the amount of carbon dioxide gas channeling and the amount of carbon dioxide injection according to the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used for restoring the formation pressure, and realizing the repeated fracturing test.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The old well gas energy supplementing and repeated fracturing performance testing method provided by the application, because the formation energy is depleted and the production is decreased after the oil well produces for a period of time, liquid carbon dioxide is injected to supplement the energy before repeated fracturing; through the injection of liquid carbon dioxide, the carbon dioxide and the oil components form a miscible phase front under the formation condition, the supercritical fluid extracts heavier hydrocarbons from the oil, and the gas concentration of the displacement front is continuously increased. The carbon dioxide and the oil become a miscible liquid, forming a single liquid phase, so that the formation oil can be effectively displaced to the production well to improve the recovery efficiency. The formation energy is supplemented by liquid carbon dioxide before fracturing, the liquid carbon dioxide energy supplementing injection time and the injection mode are optimized according to the field construction condition, and the optimal amount of carbon dioxide energy supplementing is calculated according to the formation pressure of the target well and the area of the old fracture. Therefore, the method provided by the application overcomes the shortcomings that the water resources are scarce in some areas and the existing repeated fracturing energy supplementing mode has limited contribution to the production improvement effect, and provides a theoretical basis for the research on the repeated fracturing and the single well production improvement.

[0028] The old well gas energy supplementing and repeated fracturing performance testing system provided by the application, by dividing the system into a carbon dioxide injection module, a parameter acquisition module and a parameter processing module, the repeated fracturing test is realized. The modularization idea is adopted to make each module independent of each other, and the unified management of each module is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments, and it should be understood that the following drawings only show some embodiments of the application, and should not be regarded as a limitation to the scope, and other related drawings can be obtained by the drawings without paying creative labor.

[0030] Figure 1 The old well gas energy supplementing and repeated fracturing performance testing method flow chart of the application.

[0031] Figure 2 The old well gas energy supplementing and repeated fracturing performance testing system chart of the application. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the following will combine the drawings in the embodiments of the application to clearly and completely describe the technical solutions in the embodiments of the application, and obviously, the described embodiments are some embodiments of the application, but not all the embodiments. The components of the embodiments of the application described and shown in the drawings can be arranged and designed in various different configurations.

[0033] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the application.

[0034] It should be noted that similar reference numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0035] In the description of the embodiments of the application, it should be noted that if the terms "upper", "lower", "horizontal", "inner" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, it is only for the convenience of describing the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second", etc. are only used for differentiation and cannot be understood as indicating or implying relative importance.

[0036] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0037] In the description of the embodiments of the application, it should also be noted that unless otherwise explicitly specified and limited, if the terms "arrangement", "installation", "connection", "connection" appear, they should be understood in a broad sense, for example, they can be fixedly connected, or detachably connected, or integrally connected; can be mechanically connected, or electrically connected; can be directly connected, or indirectly connected through an intermediate medium; can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0038] The application will be further described in detail below in combination with the drawings:

[0039] The application provides a kind of old well gas energy enhancement repeated fracturing performance test method, as shown in figure Figure 1 It includes the following steps:

[0040] S1, injecting liquid carbon dioxide in the old perforation section of gas well, injecting liquid carbon dioxide in the preflush stage of repeated fracturing in the selected perforation section, obtaining oil well production fracture area and oil well production fracture volume;

[0041] Injecting liquid carbon dioxide in each old perforation section, odd old perforation section or even section old perforation section.

[0042] When injecting liquid carbon dioxide in the first perforation section, do the drawdown IPR test.

[0043] S2, obtaining the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used for restoring formation pressure according to the oil well production fracture area and the oil well production fracture volume;

[0044] The method for obtaining the amount of carbon dioxide adsorbed in the matrix is as follows:

[0045]

[0046] Wherein, is the equilibrium pressure after injecting carbon dioxide, is the oil well production fracture area.

[0047] The method for obtaining the amount of carbon dioxide used for restoring formation pressure is as follows:

[0048]

[0049] Wherein, is the initial fracture volume after fracturing.

[0050] S3, obtaining the amount of carbon dioxide channeling and the amount of carbon dioxide injection according to the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used for restoring formation pressure, and realizing repeated fracturing test.

[0051] The method for obtaining the amount of carbon dioxide channeling and the amount of carbon dioxide injection is as follows:

[0052]

[0053]

[0054] Wherein, is the amount of carbon dioxide adsorbed in the matrix, is the amount of carbon dioxide used for restoring formation pressure.

[0055] The present application is that after the oil well production for a period of time, the formation energy is depleted, the production is decreased, and liquid carbon dioxide is injected before repeated fracturing to supplement energy; by injecting liquid gas, under the formation condition, carbon dioxide and oil components form a miscible phase front, supercritical fluid extracts heavier hydrocarbons from oil, and continuously concentrates the gas in the displacement front. Carbon dioxide and oil become miscible liquid, form a single liquid phase, so that the formation oil can be effectively displaced to the production well, and the recovery efficiency is improved. The specific process is as follows:

[0056] Step 1, gas liquid energy enhancement repeated fracturing section selection method:

[0057] Before repeated fracturing, liquid carbon dioxide is injected into each old perforation section; or only carbon dioxide is injected into odd old perforation sections; or only carbon dioxide is injected into even old perforation sections. The selection of injection sections is determined according to economic budget. If the economic budget is limited, only carbon dioxide is injected into some old perforation sections (with the same perforation section spacing).

[0058] Step 2, gas energy enhancement repeated fracturing injection mode:

[0059] Liquid carbon dioxide is injected in the preflush stage of repeated fracturing in the selected perforation section. The injection rate is 2 m3 / min. When injecting into the first perforation section, a reduced rate drag reduction test is required. The specific method is to reduce the injection rate to 1 m3 / min when there is 2 m3 of liquid carbon dioxide left.

[0060] Step 3, gas energy enhancement repeated fracturing injection amount calculation:

[0061] The gas energy enhancement repeated fracturing injection amount calculation includes: the volume of the fracture after the oil well has produced for a period of time, the area of the fracture after the oil well has produced for a period of time, the amount of carbon dioxide adsorbed in the matrix, the amount of carbon dioxide used to restore the formation pressure, the estimated amount of carbon dioxide channeling, and the carbon dioxide injection amount.

[0062] The present application provides an old well gas energy enhancement repeated fracturing performance test system, as shown in Figure 2 The system includes a carbon dioxide injection module, a parameter acquisition module, and a parameter processing module.

[0063] The carbon dioxide injection module is used to inject liquid carbon dioxide into the old perforation section of the gas well, inject liquid carbon dioxide in the preflush stage of repeated fracturing in the selected perforation section, and obtain the fracture area of the oil well and the fracture volume of the oil well.

[0064] The carbon dioxide parameter acquisition module is used to obtain the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore the formation pressure according to the fracture area of the oil well and the fracture volume of the oil well.

[0065] The parameter processing module is used to obtain the amount of carbon dioxide channeling and the carbon dioxide injection amount according to the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore the formation pressure, and realize repeated fracturing test.

[0066] Therefore, the application provides a gas energy supplementing and repeated fracturing performance testing method for old wells.

[0067] The gas energy supplementing and repeated fracturing performance testing method for old wells has the following advantages: 1) before repeated fracturing, oil displacement fracturing fluid is injected into the formation at a low discharge rate to supplement the formation energy, so that the formation energy can be restored to more than 100% of the formation energy before exploitation; the amount of oil displacement fracturing fluid required for energy supplementing before repeated fracturing is large, the liquid supply cycle is long, and there is a problem of insufficient liquid supply capacity; 2) the oil displacement fracturing fluid mainly acts to improve the formation pressure maintenance level; and 3) the method overcomes the problems of limited effect of energy supplementing and production increasing by using the oil displacement fracturing fluid in the existing repeated fracturing in some regions where water resources are scarce, and provides a theoretical basis for improving the single well production of repeated fracturing.

[0068] The above is only a preferred embodiment of the application and is not used to limit the application, and the application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application should be included in the protection scope of the application.

Claims

1. A method for testing the performance of gas-enhanced re-fracturing in old wells, characterized in that: The steps include: Liquid carbon dioxide is injected into the old perforated section of the gas well, and liquid carbon dioxide is injected into the pre-fracturing stage of the selected perforated section to obtain the production fracture area and production fracture volume of the oil well; Obtain the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore formation pressure based on the production fracture area and production fracture volume of the oil well; The CO2 gas crossflow rate and CO2 injection rate are obtained based on the amount of CO2 adsorbed in the matrix and the amount of CO2 used to restore formation pressure, thus enabling repeated fracturing tests. The method for obtaining the amount of carbon dioxide adsorbed on the matrix is ​​as follows: The method for obtaining the amount of carbon dioxide used to restore formation pressure is as follows: Obtaining CO2 gas cross-flow and CO2 injection rate The method is as follows: in, is the equilibrium pressure after carbon dioxide injection, is the production fracture area of ​​the oil well, is the initial fracture volume after fracturing, is the amount of carbon dioxide adsorbed on the matrix, is the amount of carbon dioxide used to restore formation pressure.

2. The method for testing the performance of old well gas energized refracturing according to claim 1, characterized in that: Liquid carbon dioxide is injected into each old perforation section, odd-numbered old perforation sections, or even-numbered old perforation sections.

3. The method for testing the performance of old well gas energized refracturing according to claim 1, characterized in that: When injecting liquid carbon dioxide in the first perforation section, a friction test with reduced displacement was performed.

4. A gas-enhanced refracturing performance testing system for old wells, characterized in that: include: A carbon dioxide injection module is used to inject liquid carbon dioxide into the old perforation section of the gas well and to inject liquid carbon dioxide into the pre-fracturing stage of the selected perforation section to obtain the production fracture area and production fracture volume of the oil well; A parameter acquisition module, wherein the carbon dioxide parameter acquisition module is used to acquire the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore formation pressure based on the production fracture area and the production fracture volume of the oil well; a parameter processing module, the parameter processing module being used to obtain the amount of carbon dioxide gas cross-flow and the amount of carbon dioxide injected based on the amount of carbon dioxide adsorbed in the matrix and the amount of carbon dioxide used to restore formation pressure, thereby implementing repeated fracturing tests; The method for obtaining the amount of carbon dioxide adsorbed on the matrix is ​​as follows: The method for obtaining the amount of carbon dioxide used to restore formation pressure is as follows: Obtaining CO2 gas cross-flow and CO2 injection rate The method is as follows: in, is the equilibrium pressure after carbon dioxide injection, is the production fracture area of ​​the oil well, is the initial fracture volume after fracturing, is the amount of carbon dioxide adsorbed on the matrix, is the amount of carbon dioxide used to restore formation pressure.

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