Device for evaluating flow conductivity of micro-nano support crack

Abstract

The utility model discloses a device for evaluating the flow conductivity of a micro-nano support fracture, which comprises a core to be tested and a core holder, the core to be tested is divided into two parts, and a gap between the two parts is a simulated fracture; the rock core holder comprises an upper plug and a lower plug, a first flow guide part and a second flow guide part are arranged in the upper plug and the lower plug respectively, a rock core to be measured is arranged between the first flow guide part and the second flow guide part, and the first flow guide part and / or the second flow guide part comprises a flow guide part body and a sliding part. The part, close to the end part of the rock core to be measured, of the flow guide piece body is replaced by the sliding piece. The sliding piece is arranged on the flow guide piece, so that the device can simulate the crack displacement process in the fracturing process, the self-supporting phenomenon in the micro-nano supporting process is further simulated, and the test result is more accurate.

Description

Technical Field

[0001] The utility model relates to the technical field of oil and gas field development, in particular to a device for evaluating the conductivity of micro-nano supported fractures. Background Art

[0002] During the development of low-permeability oil and gas reservoirs and unconventional oil and gas reservoirs, fracturing is usually required due to the low permeability of the reservoir and the small number of natural fractures. There are many ways of fracturing at present, such as common hydraulic fracturing, among which micro-fracturing is a fracturing method specifically for low-permeability oil and gas reservoirs. It mainly increases the permeability of the reservoir by creating tiny cracks in the reservoir. In the micro-fracturing process, micro-proppants are one of the key materials. After fracturing the micro-cracks, the cracks are often made by micro-proppants. Micro-proppants are usually nano-scale or micro-scale. Due to their small size, they are also quite different from conventional proppants in performance and usage.

[0003] After fracturing, the fracture conductivity is key to evaluating the fracturing effect. Stronger conductivity leads to higher oil / gas production rates. Conductivity is typically related to fracture type, the shape and formulation of the microproppant, and, when subjected to external forces, the fracture undergoes a certain degree of displacement, resulting in a degree of self-support, which also increases the fracture conductivity. While existing devices for evaluating fracture conductivity exist, their simple structures make it difficult to assess the overall fracture conductivity. Utility Model Content

[0004] In order to solve at least one of the above problems, the present invention proposes a device for evaluating the conductivity of micro-nano supported cracks.

[0005] The technical solution of the present utility model is: a device for evaluating the conductivity of micro-nano supported fractures, comprising a core to be tested and a core holder, wherein the core to be tested is divided into two parts, and the gap between the two parts is a simulated fracture; the core holder comprises an upper plug and a lower plug, wherein a first flow guide member and a second flow guide member are respectively provided in the upper plug and the lower plug, and the core to be tested is provided between the first flow guide member and the second flow guide member, and the first flow guide member and / or the second flow guide member comprise a flow guide member body and a sliding member, and a portion of at least one of the flow guide member bodies close to the end of the core to be tested is replaced by the sliding member, a cross-section of a portion of the core to be tested is completely fitted with a cross-section of the sliding member, and the sliding member will slide under certain pressure conditions.

[0006] One implementation manner of the present invention is that the device further comprises a high-pressure gas cylinder, one end of the high-pressure gas cylinder is connected to the core holder, and an outlet of the core holder is sequentially connected to a back pressure valve and a gas flow meter.

[0007] One implementation manner of the present utility model is that the device further comprises a displacement pump, which is sequentially connected to an intermediate container, a core holder, a back pressure valve, and a meter.

[0008] An implementation manner of the present invention is that two core clamps are provided.

[0009] One implementation manner of the present invention is that a differential pressure sensor is further provided, and both ends of the differential pressure sensor are respectively provided at both ends of the core holder.

[0010] One embodiment of the present utility model is that the core clamp also includes a shell, a lining is provided inside the shell, a rubber tube is provided outside the core to be tested, both ends of the rubber tube are detachably arranged on the first guide member and the second guide member, and a confining pressure chamber is between the rubber tube and the lining, and the confining pressure chamber is connected to a confining pressure pump.

[0011] An implementation manner of the present invention is that the rock core to be tested is produced by 3D printing.

[0012] In one embodiment of the present invention, a sealed chamber is provided between the sliding member and the guide member body, and an elastic member is provided in the sealed chamber.

[0013] Beneficial effect: By arranging a sliding part on the guide part, the utility model enables the device to simulate the crack displacement process during the fracturing process, and then simulate the self-supporting phenomenon in the micro-nano support process, so that the test results are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the utility model;

[0015] Figure 2 Schematic diagram of the core holder structure.

[0016] In the figure, 1 is a core holder, 2 is a differential pressure sensor, 3 is a confining pressure pump, 4 is a back pressure valve, 5 is a gas flow meter, 6 is a meter, 7 is a high-pressure gas cylinder, 8 is a displacement pump, 9 is an intermediate container, 10 is a fluid tank, and 11 is a four-way valve;

[0017] 101 is the shell, 102 is the liner, 103 is the confining pressure chamber, 104 is the upper plug, 105 is the first flow guide, 106 is the rubber sleeve, 107 is the second flow guide, 108 is the lower plug, 109 is the core to be tested, 110 is the sliding part, and 111 is the elastic part. DETAILED DESCRIPTION

[0018] The specific implementation methods of the present invention will be clearly and completely described below with reference to examples and drawings. Obviously, the described examples are only some embodiments of the present invention, rather than all embodiments.

[0019] like Figures 1 and 2 As shown, a device for evaluating the conductivity of micro-nano supported fractures includes a core 109 to be tested and a core holder 1, wherein the core 109 to be tested is divided into two parts, and the gap between the two parts is a simulated fracture; the core holder 1 includes an upper plug 104 and a lower plug 108, wherein a first flow guide 105 and a second flow guide 107 are respectively provided in the upper plug 104 and the lower plug 108, and the core 109 to be tested is provided between the first flow guide 105 and the second flow guide 107, and the first flow guide 105 and / or the second flow guide 107 include a flow guide body and a sliding member 110, wherein a portion of the flow guide body close to the end of the core 109 to be tested is replaced by the sliding member 110, and a cross section of a portion of the core 109 to be tested is completely fitted with a cross section of the sliding member 110, and the sliding member 110 will slide under certain pressure conditions.

[0020] Specifically, in this device, the core to be tested 109 can be a core extracted from the stratum, which is divided into two parts by a splitting method, and then the two parts are combined, with the middle of the two parts being a crack; an artificial core can also be used, such as a core prepared by 3D printing. When preparing a core by 3D printing, the following steps can be taken: the cracks in the core are scanned and modeled, and then two core parts are printed out by a 3D printer based on the model. The two core parts are combined to form a core to be tested. At the same time, the two parts referred to here refer to the core being divided into two parts along its radial direction, preferably divided into two parts along the surface where the center line of the core is located; this technology belongs to the existing technology, so its structure will not be described in detail here. Since 3D printing technology can be used to prepare a large number of identical cores, in this embodiment, the core prepared by 3D printing technology is used as the core to be tested 109.

[0021] The core holder 1 differs from conventional core holders in that, in this device, a portion of at least one of the first flow guide 105 and / or the second flow guide 107 of the core holder 1 is replaced by a sliding member 110. This sliding member 110 will slide under certain pressure conditions, but the sliding distance is small, typically ranging from hundreds of microns to several millimeters. Furthermore, under no-stress conditions, the end of the sliding member 110 is flush with the end surface of the flow guide body. To allow the core to slide under stress, the areas of the two surfaces of the sliding core portion and the sliding member must meet the following requirements: the contact surface of the sliding core portion must be no larger than the contact surface of the sliding member, and preferably, the areas of the two contact surfaces are equal. This is common knowledge in the art. In addition, the cross section of a portion of the core 109 to be tested completely fits the cross section of the sliding member 110. Therefore, when the sliding member 110 slides, a portion of the core 109 to be tested may slide along with it, thereby making the core 109 to be tested self-supporting, which is consistent with the actual working conditions. The portion where the sliding member is provided is the cross section of the core 109 to be tested. This makes the test results closer to the final results.

[0022] At the same time, for the sliding member 110, since the core 109 to be tested is divided into two parts, with a total of 4 end faces, theoretically 4 sliding members 110 can be set, but considering the actual situation, 1 to 2 sliding members 110 are usually set. In this embodiment, one sliding member 110 is set.

[0023] Although relative sliding between the sliding member 110 and the guide body is a conventional arrangement, to facilitate understanding of the present device by those skilled in the art, in this embodiment, a sealed chamber is provided between the sliding member 110 and the guide body, and an elastic member 111 is disposed within the sealed chamber. The elastic member 111 may be a spring or compressed gas, and under the action of an external force, the elastic member 111 contracts, thereby causing the sliding member 110 to slide.

[0024] In this embodiment, the core holder 1 further includes a housing 101, an inner liner 102 disposed within the housing 101, and a rubber sleeve 106 disposed externally on the core 109 to be tested. The ends of the rubber sleeve 106 are detachably attached to the first and second flow guides 105 and 107. A confining pressure chamber 103 is located between the rubber sleeve 106 and the inner liner 102, and the confining pressure chamber 103 is connected to the confining pressure pump 3. This portion of the core holder 1 is conventional in the art.

[0025] In practice, reservoirs are divided into oil and gas reservoirs. Therefore, to fully simulate the conductivity under two different reservoir conditions, this embodiment employs two core holders 1, each equipped with two different pressurization systems: a liquid-phase pressurization system comprising a fluid tank 10, a displacement pump 8, and an intermediate container 9; and a gas-phase pressurization system powered by a high-pressure gas cylinder 7, used to evaluate fracture conductivity under both oil and gas reservoir conditions. To ensure the proper operation of the different pressurization systems, a four-way valve 11 is also provided, connecting the liquid-phase and gas-phase pressurization systems in parallel, with each corresponding to a core holder 1. To accommodate the liquid-phase pressurization system, a backpressure valve 4 and a meter 6 are installed at the outlet of the core holder 1. The meter 6 can be a liquid metering device such as a graduated cylinder. To accommodate the gas-phase pressurization system, a backpressure valve 4 and a gas flowmeter 5 are also installed at the outlet of the core holder 1.

[0026] In practice, it is often necessary to evaluate the performance of micro- and nano-proppants. Therefore, a comparison is often helpful in demonstrating the effectiveness of different micro- and nano-proppants. Therefore, in this embodiment, two core holders 1 are provided to compare the effectiveness of different micro- and nano-proppants. Furthermore, when comparing the effectiveness of different micro- and nano-proppants, experiments typically need to be conducted under the same conditions. Therefore, in this embodiment, a crossover line is provided on the four-way valve 11, connecting the two core holders 1. If necessary, the same pressurization system can be used to act on both core holders 1.

[0027] In order to facilitate the evaluation of the conductivity of the crack, a pressure differential sensor 2 is also provided. The two ends of the pressure differential sensor 2 are respectively provided at the two ends of the core clamp 1, and are used to measure the pressure difference between the inlet and outlet of the core clamp 1, so as to facilitate the evaluation of the conductivity of the core crack.

[0028] To use the device, the entire apparatus is connected, and the appropriate micro-nano proppant is placed within the fractures of the core being tested. The two halves of the core are then assembled and placed within the core holder. The core is then installed so that the end face of one core portion rests against the end face of the elastic member. Once the equipment is installed, the test begins. During the experiment, liquid or gas is used for testing, depending on actual needs. The changes in the values ​​of the differential pressure sensor, gas flow meter, and meter are recorded.

[0029] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A device for evaluating the conductivity of micro-nano supported cracks, characterized in that: The invention comprises a rock core to be tested and a rock core holder, wherein the rock core to be tested is divided into two parts, and the gap between the two parts is a simulated crack; the rock core holder comprises an upper plug and a lower plug, wherein a first flow guide and a second flow guide are respectively provided in the upper plug and the lower plug, and the rock core to be tested is provided between the first flow guide and the second flow guide, and the first flow guide and / or the second flow guide comprise a flow guide body and a sliding member, wherein a portion of the flow guide body close to the end of the rock core to be tested is replaced by the sliding member, a cross section of a portion of the rock core to be tested is completely fitted with a cross section of the sliding member, and the sliding member will slide under certain pressure conditions.

2. The device according to claim 1, characterized in that The device further comprises a high-pressure gas cylinder, one end of which is connected to the core holder, and an outlet of the core holder is sequentially connected to a back-pressure valve and a gas flow meter.

3. The device according to claim 1, characterized in that The device further comprises a displacement pump, which is sequentially connected to an intermediate container, a core holder, a back pressure valve and a meter.

4. The device according to any one of claims 1 to 3, characterized in that: There are two core holders.

5. The device according to claim 1, characterized in that A differential pressure sensor is also provided, and two ends of the differential pressure sensor are respectively provided at two ends of the core holder.

6. The device according to claim 1, characterized in that The core holder also includes a shell, a lining is provided inside the shell, and a rubber tube is provided outside the core to be tested. The two ends of the rubber tube are detachably arranged on the first guide member and the second guide member. There is a confining pressure chamber between the rubber tube and the lining, and the confining pressure chamber is connected to a confining pressure pump.

7. The device according to claim 1, characterized in that The rock core to be tested is produced by 3D printing.

8. The device according to claim 1, characterized in that A sealed chamber is provided between the sliding member and the guide member body, and an elastic member is provided in the sealed chamber.

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