CN205103092U - A pressure head system for indoor triaxial hydraulic fracturing is experimental - Google Patents

Abstract

An indenter system used for indoor triaxial hydraulic fracturing tests relates to a test system to overcome the disadvantages of time-consuming sample preparation, complicated operation and complicated post-test treatment of the indenter used in triaxial fracturing tests in the prior art. Including the pressure head unit, rubber sealing ring and nut, the pressure head unit is an integrated structure, which in turn includes the top joint, the main body pressure head, the lower pipe and the bottom taper sealing joint, the top joint, the main body pressure head, the lower pipe and the bottom The taper sealing joints are all arranged coaxially and the central axis is provided with a through hole along its axial direction. The outer surface of the top joint is provided with a groove, and the groove is provided with a matching rubber sealing ring; the outer surface of the bottom taper sealing joint is provided with a There are external threads, and the nut matches the external threads. The utility model can quickly and efficiently complete indoor triaxial hydraulic fracturing tests, has good sealing effect, can effectively prevent pressurized fluid from leaking, and is suitable for indoor uniaxial or triaxial hydraulic fracturing tests.

Description

Indenter system for indoor triaxial hydraulic fracturing tests

technical field

The utility model relates to a test system, in particular to a pressure head system for realizing indoor triaxial hydraulic fracturing tests of brittle materials.

Background technique

With the increasingly tense energy situation, unconventional energy sources such as tight gas, coal bed methane and shale gas have attracted worldwide attention. Since unconventional oil and gas reservoirs have low production characteristics of "low porosity and low permeability", fracturing technology represented by hydraulic fracturing has become the main means to achieve unconventional oil and gas recovery. Although very few countries have the capacity to commercially produce unconventional oil and gas, the unknown mechanism and high cost of hydraulic fracturing are still a worldwide problem. In particular, fracturing production under complex stress and geological conditions is difficult to predict and control. At this time, indoor triaxial hydraulic fracturing becomes the key basis for exploring fracturing mechanism, and it is necessary to design simple and efficient indoor fracturing equipment.

At present, the triaxial fracturing test is limited to the true triaxial fracturing test. However, the cost of the true triaxial test equipment is too high and the related technology is immature. Rock samples are time-consuming and labor-intensive, and the fracturing mechanism obtained is not clear. Therefore, there is a need for an indoor pseudo-triaxial fracturing test system for small-sized fracturing specimens (ie, rock samples), such as a standard specimen with a diameter×height of 50mm×100mm recommended by the International Society of Rock Mechanics (ISRM). Compared with uniaxial fracturing, limited by the test equipment and its high-pressure sealing performance, there are few relevant data on indoor pseudo-triaxial hydraulic fracturing of brittle materials. At the same time, the common test sealing method is to use superglue to seal the connection between the fracturing specimen and the indenter to prevent fluid leakage, but this method results in time-consuming sample preparation, complicated operation, and the need for high temperature or sharps after the test. glue. It can be seen that there is an urgent need for an indenter for indoor triaxial fracturing tests with simple operation, good sealing performance and strong adaptability. At this time, the principles of lateral sealing and taper sealing used in the mechanical field have become a breakthrough point.

Utility model content

The technical problem to be solved by the utility model is to fill the blank of the indoor false triaxial fracturing test, and overcome the shortcomings of time-consuming sample preparation, complicated operation and complicated post-test treatment caused by the superglue sealing method in the prior art, and provide a An indenter system used for indoor triaxial hydraulic fracturing tests of brittle materials, the indenter has a simple structure and is easy to operate.

The technical solution adopted by the utility model to solve the technical problem is: the pressure head system for indoor three-axis hydraulic fracturing test, including the pressure head unit, rubber sealing ring and nut, the pressure head unit is an integrated structure, followed by Including the top joint, the main body pressure head, the lower pipe and the bottom taper sealing joint. The outer surface is provided with a groove, and the groove is provided with a matching rubber sealing ring; the outer surface of the bottom taper sealing joint is provided with an external thread, and the nut is matched with the external thread.

Specifically, the top joint, the main body pressure head, the lower pipe and the bottom taper sealing joint are all cylindrical structures.

Specifically, there are several grooves, which are arranged at intervals on the outer surface of the top joint.

Further, the outer diameter of the top connector is 5-10 mm, and the outer diameter of the main body indenter is 50 mm or 100 mm.

Preferably, the groove is a semicircular groove.

Specifically, the inner surface of the bottom taper sealing joint is provided with an internal thread, and the internal thread is in contact with the internal tapered surface.

The beneficial effects of the utility model are: simple structure, easy to process, can quickly and efficiently complete the indoor three-axis hydraulic fracturing test, good sealing effect, can effectively prevent the leakage of pressurized fluid, greatly improve the speed of loading and unloading, Reduce the loss of manpower, material resources and time. The utility model is suitable for indoor uniaxial or triaxial fracturing tests of different fluid fracturing and different brittle materials.

Description of drawings

Fig. 1 is the structural representation when the utility model is matched with the fracturing test piece;

Fig. 2 is the structural representation of the pressure head unit in the utility model;

Fig. 3 is a schematic diagram of the structure of the utility model when the bottom taper sealing joint is connected with an external pipeline and a nut;

Fig. 4 is the structural representation of rubber sealing ring in the utility model;

Fig. 5 is the structural representation of hex nut in the utility model;

Among them, 1 is the pressure head unit, 2 is the rubber sealing ring, 3 is the nut, 4 is the top joint, 41 is the semicircular groove, 5 is the main body pressure head, 6 is the lower pipe, 7 is the bottom taper sealing joint, 71 72 is an internal thread, 73 is an external thread, 8 is a through hole, 9 is a fracturing test piece, and 10 is an external pipeline.

detailed description

Below in conjunction with accompanying drawing, describe the technical solution of the utility model in detail.

As shown in Figures 1 and 2, the indenter system used for indoor triaxial hydraulic fracturing tests includes an indenter unit 1, a rubber sealing ring 2, and a nut 3. Connected top joint 4, main body pressure head 5, lower pipe 6 and bottom taper sealing joint 7. That is, the top joint 4, the main body pressure head 5, the lower pipe 6 and the bottom taper sealing joint 7 are designed in an integrated manner and processed as a whole to ensure good sealing performance. The top joint 4, the main body pressure head 5, the lower pipe 6 and the bottom taper sealing joint 7 are all coaxially arranged, that is, arranged with the central axis, and the central axis is provided with a through hole along its axial direction, so that the pressure head unit 1 Inject fluid into the bottom. The center of the indenter unit is the central axis, indicating that the through holes are arranged along the central axes of the top joint 4, the main body indenter 5, the lower pipe 6 and the bottom taper sealing joint 7, and these parts are all penetrated by the through holes. Since the rock mechanics test indenters are generally cylindrical, the above-mentioned top joint 4, main body indenter 5, lower pipe 6 and bottom taper sealing joint 7 are preferably all cylindrical structures, that is, the central axis has a through hole. cylinder.

The top joint 4 is used to connect and fix the fracturing test piece, the outer surface of the top joint 4 is provided with a groove, and the rubber sealing ring 2 matching it is arranged on the groove. In order to ensure the sealing effect, there are several grooves, which are arranged at intervals on the outer surface of the top joint 4, and the rubber sealing rings 2 are placed at intervals to form a lateral sealing joint, which is used to connect and fix the fracturing test piece in Fig. 1 . Due to the limited height of the top joint 4, the number of grooves is preferably 2 or 3. The fracturing test piece can adopt the fracturing test piece in the prior art, and the fracturing test piece is provided with a central borehole. In the specific use process, the fracturing test piece is placed in the pressure head system designed by the utility model The upper part can be directly sleeved on the top of the indenter unit. Preferably, the groove is a semicircular groove 41 because the matching rubber sealing ring is in the shape of a ring. The structure of the matching rubber sealing ring 2 is shown in FIG. 4 , and the hollow part can just fit into the semicircular groove 41 , and the two fully fit together. The outer diameter of the rubber sealing ring 2 should be slightly larger than the diameter of the central borehole of the fracturing test piece, so as to closely fit to achieve the purpose of lateral sealing. The number of rubber sealing rings 2 is determined according to the pressure of the fracturing fluid injected in the test and the sealing effect. For example, two rubber sealing rings made of fluorine rubber are arranged at intervals, the quantity is small, the cost is saved and the sealing effect can be enhanced.

The lower pipe 6 is used to connect the main body pressure head 5 and the bottom tapered sealing joint 7, and the bottom tapered sealing joint 7 is connected to the external pipe 10 for injecting fluid into the through hole 8, and the external pipe 10 is provided with a tapered sealing nut external pipes.

As shown in Figure 3, the function of the required part of the utility model can be realized by using the existing taper sealing joint at the bottom of the taper sealing joint 7, and its inner surface is provided with an internal thread 72, and the internal thread 72 and the inner tapered surface 71 Connected, through the taper sealing connection external pipeline injection fluid injection, the outer surface of the bottom taper sealing joint 7 is provided with external threads, the nut matches the external thread, in the specific test operation, the pressure head unit 1 can be installed by installing the nut 3 Fixed on the testing machine table, the size of the nut 3 is determined by the testing machine structure.

The outer diameter of the top joint 4 is slightly smaller than the diameter of the central borehole of the fracturing test piece, so that the upper part can be installed smoothly on the fracturing test piece; the size of the semicircular groove 41 on the surface depends on the size of the rubber sealing ring 2, and the two should be fully fitted The outer diameter of the main body indenter 5 is the same as that of the fracturing test piece, and the outer diameter and length of the lower pipe 6 are determined by the size of the through hole in the center of the testing machine table for placing the indenter; the bottom taper sealing joint 7 has internal threads and internal cones The surface 71 is matched with the tapered joint of the external pipe, and the tapered surface must be sufficiently smooth and complete to realize the tapered sealing function in the high-pressure environment. The outer diameters of the top joint 4 and the main body indenter 5 should match the actual fracturing test piece. When used, the outer diameter of the top joint must match the central borehole diameter of the fracturing test piece. Although the specification requires a standard fracturing The test piece has a diameter×height of 50mm×100mm, but it can also be 100mm×200mm in diameter×height, and the diameter of the central borehole of the fracturing test piece is 5mm. Therefore, the outer diameter of the top joint 4 The range is 5-10mm, but the outer diameter is usually 5mm. The outer diameter of the main body indenter 5 is generally 50 mm or 100 mm, which matches the size of the standard triaxial test piece required by the Rock Mechanics Code.

As shown in FIG. 5 , the internal thread of the nut 3 is matched with the external thread 73 of the bottom taper sealing joint 7 to fix the indenter unit 1 on the table of the testing machine. Described nut 3 adopts hexagonal nut, and its outer diameter should be determined by the size of the through hole in the center of the testing machine table top.

In the implementation process of the specific indoor triaxial hydraulic fracturing test, the specific process of using this pressure head system is as follows:

A. According to the size of the central borehole of the fracturing test piece, place the rubber sealing ring with matching outer diameter in the groove of the top joint of the indenter unit, and check the tightness of the fit between the two;

B. According to the structure of the three-axis compression testing machine, pass the lower pipe of the indenter system through the indenter installation through hole in the center of the testing machine table to ensure that the main indenter is closely attached to the testing machine table, and then install it on the tail taper sealing joint. Put on the nut and tighten it, and fix the indenter system on the testing machine by clamping force between the nut and the indenter of the main body;

C. Connect the tail taper sealing joint to the external pipeline used for fluid injection, tighten the joint to fully ensure the full fit of the tapered surface and ensure the effective sealing of the joint, so far the installation of the pressure head system has been completed;

D. According to the test requirements, align the fracturing test piece with the triaxial membrane on the upper joint, and slowly rotate until the upper joint completely enters the center hole of the fracturing test piece. The integrity of the rubber sealing ring should be ensured when loading the sample. tightness;

E. Start to apply a certain axial force to fix the fracturing specimen, lower the triaxial chamber of the testing machine and apply confining pressure to a predetermined level according to the test requirements, then slowly inject water and apply water pressure through the external pipeline until the fracturing test is completed;

F. After the test is completed, remove the fracturing test piece, repeat step D and step E, and complete the triaxial hydraulic fracturing test of this group of fracturing test pieces.

The above method can make it possible to directly remove the fracturing test piece from the upper part after the first fracturing test, and continue to install the fracturing test piece with a central drilling hole for testing, effectively avoiding repeated disassembly of the indenter and high temperature or The sharp tool handles the complexity and inefficiency of viscose, and at the same time, it can ensure the tightness of the injected high-pressure fluid, which greatly improves the efficiency of the test operation.

When the triaxial confining pressure becomes 0, it is the uniaxial case, that is, the uniaxial is a special case of the triaxial. Therefore, the pressure head system of the technical solution is also suitable for single-axis situations. Although the current engineering is dominated by hydraulic fracturing, this technical solution can also be applied to other fracturing media, such as other liquids or gases.

Claims (6)

1. for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, comprise presser unit (1), rubber seal (2) and nut (3), described presser unit (1) is integral type structure, comprise top contact (4), main body pressure head (5), lower pipeline (6) and bottom taper sealing joint (7) successively, top contact (4), main body pressure head (5), lower pipeline (6) and bottom taper sealing joint (7) are all coaxial setting and central axis is axially arranged with through hole along it; Top contact (4) outside surface is provided with groove, groove is provided with the rubber seal (2) matched with it; Bottom taper sealing joint (7) outside surface is provided with external thread, and described nut and external thread match.

2. as claimed in claim 1 for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, described top contact (4), main body pressure head (5), lower pipeline (6) and bottom taper sealing joint (7) are all cylindrical structure.

3., as claimed in claim 1 for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, described groove is several, is disposed on top contact (4) outside surface.

4., as claimed in claim 1 for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, the external diametrical extent of described top contact is 5 ~ 10mm, and described main body pressure head (5) external diameter is 50mm or 100mm.

5., as claimed in claim 1 for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, described groove is semi-circular recesses (41).

6., as claimed in claim 1 for the pressurized head systems of indoor three axle waterfrac treatment tests, it is characterized in that, the inside surface of described bottom taper sealing joint (7) is provided with internal thread, and internal thread connects with inner conical surface.