Reducing centering device for non-vertical hole hydraulic fracturing ground stress test and use method

Abstract

The invention discloses a variable-diameter centering device for a non-vertical hole hydraulic fracturing ground stress test and a use method, and belongs to the technical field of ground stress measurement. The self-tightening centering device is composed of a sleeve assembly and a self-tightening centering assembly. The sleeve assembly comprises an upper sleeve, a pulley and the like; the self-tightening centering assembly comprises a lower sleeve, an axial telescopic spring, a radial telescopic spring, a clamping piece and a rear cover. The device is simple in structure, high in automation degree and capable of being repeatedly used, reducing centering of non-vertical hole hydraulic fracturing ground stress testing can be completed, the problem that the testing method is large in measurement difficulty is solved, and the device has important significance on non-vertical hole hydraulic fracturing ground stress measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of rock mass mechanics tests, and in particular relates to a variable diameter centering device for non-vertical hydraulic fracturing in-situ stress testing and a use method thereof. Background Art

[0002] Geostress refers to the initial stress that exists naturally in the stratum and is not disturbed by any human or engineering disturbance. The stability of underground openings such as mines, shafts, tunnels, and caverns in civil engineering and mining engineering depends to a large extent on the distribution and size of geostress. During the construction process, the destruction or disturbance of the rock mass will cause the naturally formed stress of the rock mass to deform, resulting in the rearrangement and distribution of the internal stress of the rock mass. The rock mass that was originally in an elastic state may change to a plastic state, and even cause it to break. Therefore, the measurement and research of geostress has always been one of the hot topics of concern for scientific researchers in the engineering community.

[0003] Conventional hydraulic fracturing geostress tests mainly include vertical hole hydraulic fracturing geostress tests and non-vertical hole hydraulic fracturing geostress tests. When hydraulic fracturing geostress tests are performed in vertical holes, variable diameter centering can generally be achieved through drilling rig centering and leveling, and the operation is relatively simple. When hydraulic fracturing geostress tests are performed in non-vertical holes, it is often not convenient for the drilling rig to perform variable diameter centering. Lowering the equipment without centering will cause the geostress measurement equipment to deviate and get stuck. This makes the geostress test time-consuming and labor-intensive, and the test efficiency is low.

[0004] The current solution mainly adopts the following measures: when testing the lowering of the equipment, the angle is measured by a compass, and each lowering of the equipment to the drill rod is at a specific angle. This method will greatly slow down the drilling speed and also consume more physical strength for the drilling rig operator. Therefore, the study of a variable diameter centering device for non-vertical hole hydraulic fracturing ground stress testing can help reduce the installation difficulty of non-vertical hole hydraulic fracturing method, which is of great significance to improving the accuracy of ground stress measurement results and ensuring production progress. Summary of the invention

[0005] In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a variable diameter centering device for non-vertical hole hydraulic fracturing ground stress testing, which has low installation difficulty, high precision and is reusable, and a method of use.

[0006] The technical solution adopted to solve the above problems is a variable diameter centering device for non-vertical hole hydraulic fracturing ground stress testing, including a sleeve assembly and a self-tightening centering assembly, the sleeve assembly including an upper sleeve and multiple groups of pulleys, the pulleys are semi-embedded in the outer wall of the upper sleeve through axles; the self-tightening centering assembly includes a lower sleeve, multiple axial telescopic springs, multiple radial telescopic springs, multiple clips, and a back cover, the upper sleeve is connected to the lower sleeve as a whole, the inner diameter of the upper sleeve is smaller than the inner diameter of the lower sleeve, so that a step is formed at the connection between the upper sleeve and the lower sleeve, and multiple clips are radially distributed inside the lower sleeve, one end of the axial telescopic spring is connected to the step at the bottom of the upper sleeve, and the other end is connected to a top end of the clip, one end of the radial telescopic spring is fixed to the inner wall of the lower sleeve, and the other end is connected to the side wall of the clip, so that the clip is elastically suspended inside the lower sleeve, and the back cover with a through hole is located at the bottom of the lower sleeve.

[0007] The upper sleeve is a hollow cylinder, which is connected to the self-tightening centering component through threads, and has an inner diameter larger than the outer diameter of the hydraulic fracturing equipment and an outer diameter smaller than the borehole diameter.

[0008] The outer wall of the upper sleeve is provided with a groove, and the pulley is embedded in the outer wall of the upper sleeve through the wheel shaft. Half of the pulley is located in the groove of the outer wall of the upper sleeve, and the other half is exposed and can be tangent to the inner wall of the drill hole.

[0009] The pulleys are axially distributed into three groups, and each group of pulleys (2) has four pulleys evenly distributed in the radial direction.

[0010] The axial spring is evenly distributed along the groove on the bottom step of the upper sleeve in the circumferential direction, and the other end of the axial spring is connected to the groove at the top end of the clip.

[0011] The clip is wedge-shaped and is distributed circumferentially along the interior of the centering device. The clip is thinner on the side facing the upper sleeve and gradually becomes thicker on the side facing the self-tightening centering component.

[0012] The top end of the clip is provided with an axial groove, the radial side wall is provided with a radial groove, the axial groove is connected to the axial telescopic spring, and the radial groove is connected to the radial telescopic spring.

[0013] One side of the radial telescopic spring is connected to the radial groove of the clip, and the other side is connected to the groove on the inner wall of the lower sleeve.

[0014] The rear cover has one axial side connected to the lower sleeve through a thread, and its inner diameter is larger than the outer diameter of the hydraulic fracturing equipment, and its outer diameter is smaller than the borehole diameter.

[0015] The method for using the variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing as described above comprises the following steps:

[0016] Step 1: In a non-vertical hydraulic fracturing borehole to be measured, a non-vertical borehole hydraulic fracturing ground stress test variable diameter centering device is placed in the borehole, with the end slightly protruding out of the borehole;

[0017] Step 2: Place the hydraulic fracturing device into the variable diameter centering device for hydraulic fracturing in-situ stress testing of non-vertical holes, push the device into the junction of the upper sleeve and the lower sleeve in the hole, and then continue to push the hydraulic fracturing device forward, the clamp forms a conical channel to clamp the hydraulic fracturing device, the device just enters the hole in the center, and then reaches the predetermined position of the test;

[0018] Step 3: After the installation device reaches the predetermined position, the test is completed and the hydraulic fracturing equipment is extracted upward. When the equipment reaches the variable diameter centering device for hydraulic fracturing stress test in non-vertical holes at the junction of the variable diameters, the hydraulic fracturing equipment reaches the outside of the conical small opening formed by the clamp and exits the hole together with the centering device.

[0019] The beneficial effects of the present invention are: avoiding the jamming of the drill caused by angle deviation, which affects the test results, and ensuring the installation efficiency. The sleeve with a pulley is used to conveniently, quickly and labor-savingly advance the drill hole, thereby improving the test efficiency. The self-tightening centering assembly of the present invention can be taken out of the hole together with the equipment after the test is completed, and can be reused. The structure is simple, easy to transport and assemble, and can be directly slid into the hole during the test to complete the installation, thereby reducing the production cost and improving the production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing provided by an embodiment of the present invention;

[0021] Figure 2 A schematic structural diagram of an AA cross-sectional view of a variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing provided by an embodiment of the present invention;

[0022] Figure 3 A schematic structural diagram of a BB cross-sectional view of a variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing provided by an embodiment of the present invention;

[0023] Figure 4 A CC cross-sectional structural diagram of a variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing provided by an embodiment of the present invention;

[0024] In the figure: 1-upper sleeve; 2-pulley; 3-lower sleeve; 4-axial telescopic spring; 5-radial telescopic spring; 6-clamp; 7-back cover. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0027] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0028] like Figure 1-4 As shown, the variable diameter centering device for non-vertical hole hydraulic fracturing ground stress testing of the present invention comprises a sleeve assembly and a self-tightening centering assembly, the sleeve assembly comprises an upper sleeve 1 and multiple groups of pulleys 2, the pulleys 2 are semi-embedded on the outer wall of the upper sleeve 1 through the wheel axle; the self-tightening centering assembly comprises a lower sleeve 3, multiple axial telescopic springs 4, multiple radial telescopic springs 5, multiple clips 6, and a back cover 7, the upper sleeve 1 is connected to the lower sleeve 3 as a whole, the inner diameter of the upper sleeve 1 is smaller than the inner diameter of the lower sleeve 3, so that a step is formed at the connection between the upper sleeve 1 and the lower sleeve 3, and multiple clips 6 are radially distributed inside the lower sleeve 3, one end of the axial telescopic spring 4 is connected to the step at the bottom of the upper sleeve 1, and the other end is connected to a top end of the clip 6, one end of the radial telescopic spring 5 is fixed to the inner wall of the lower sleeve 3, and the other end is connected to the side wall of the clip 6, so that the clip 6 is elastically suspended inside the lower sleeve 3, and the back cover 7 with a through hole is located at the bottom of the lower sleeve 3.

[0029] The upper sleeve 1 is a hollow cylinder, which is connected to the self-tightening centering component through threads, and has an inner diameter larger than the outer diameter of the hydraulic fracturing equipment and an outer diameter smaller than the borehole diameter.

[0030] The outer wall of the upper sleeve 1 is provided with a groove, and the pulley 2 is embedded in the outer wall of the upper sleeve through the wheel axle, half of the pulley is located in the groove of the outer wall of the upper sleeve, and the other half is exposed and can be tangent to the inner wall of the drill hole.

[0031] The pulleys 2 are axially distributed into three groups, and each group of pulleys (2) has four pulleys evenly distributed in the radial direction.

[0032] The axial spring 4 is evenly distributed along the groove on the bottom step of the upper sleeve, and the other end of the axial spring 4 is connected to the groove at the top end of the clamp 6.

[0033] The clip 6 is wedge-shaped and distributed circumferentially along the inner part of the centering device. The clip 6 is thinner on the side facing the upper sleeve and gradually becomes thicker on the side facing the self-tightening centering component.

[0034] The top of the clip 6 is provided with an axial groove, and the radial side wall is provided with a radial groove. The axial groove is connected to the axial telescopic spring, and the radial groove is connected to the radial telescopic spring 5 .

[0035] One side of the radial telescopic spring 5 is connected to the radial groove of the clamping piece 6 , and the other side is connected to the groove of the inner wall of the lower sleeve 3 .

[0036] The rear cover 7 is connected to the lower sleeve 3 via a thread on one axial side, and its inner diameter is larger than the outer diameter of the hydraulic fracturing equipment, and its outer diameter is smaller than the borehole diameter.

[0037] The method for using the above-mentioned variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing is characterized by comprising the following steps:

[0038] Step 1: In a non-vertical hydraulic fracturing borehole to be measured, a non-vertical borehole hydraulic fracturing ground stress test variable diameter centering device is placed in the borehole, with the end slightly protruding out of the borehole;

[0039] Step 2: Place the hydraulic fracturing device into the variable diameter centering device for hydraulic fracturing in-situ stress testing of non-vertical holes, push the device into the junction of the upper sleeve and the lower sleeve in the hole, and then continue to push the hydraulic fracturing device forward, the clamp forms a conical channel to clamp the hydraulic fracturing device, the device just enters the hole in the center, and then reaches the predetermined position of the test;

[0040] Step 3: After the installation device reaches the predetermined position, the test is completed and the hydraulic fracturing equipment is extracted upward. When the equipment reaches the variable diameter centering device for hydraulic fracturing stress test in non-vertical holes at the junction of the variable diameters, the hydraulic fracturing equipment reaches the outside of the conical small opening formed by the clamp and exits the hole together with the centering device.

[0041] Specifically, the device of the present invention mainly consists of two parts: a sleeve assembly and a self-tightening centering assembly; the sleeve assembly consists of a sleeve 1, a pulley 2 and other parts, the upper sleeve 1 is located at the top of the device, the pulley 2 is located on the side of the groove on the outer wall of the upper sleeve 1, the self-tightening centering assembly includes a lower sleeve 3, an axial telescopic spring 4, a radial telescopic spring 5, a clamp 6, and a back cover 7, one end of the axial telescopic spring 3 is welded to the bottom groove of the upper sleeve 1, the other end of the axial telescopic spring 3 is welded to the axial bottom of the clamp 6, one end of the radial telescopic spring 5 is welded to the inner wall groove of the lower sleeve 3, and the other end of the radial telescopic spring 5 is welded to the outer wall groove of the clamp 5; the clamp 6 is evenly distributed in the self-tightening centering assembly along the radial direction, and the back cover 6 is located at the bottom of the self-tightening centering assembly and is connected to the lower sleeve 3 through threads.

[0042] The upper sleeve 1 and the lower sleeve 3 are hollow cylinders. The upper sleeve 1 has an outer diameter of 120 mm and an inner diameter of 72 mm, and the lower sleeve 3 has an outer diameter of 130 mm and an inner diameter of 110 mm. The upper sleeve 1 and the lower sleeve 3 are connected by threads.

[0043] The pulleys are axially distributed in three groups, each with four pulleys distributed circumferentially and located in the groove on the outer wall of the upper sleeve 1, so that the device can enter the 130mm opening more smoothly.

[0044] The axial telescopic spring 4 will be extended when the hydraulic fracturing equipment enters, playing the role of fixing the clip. The radial telescopic spring 5 will be compressed when the hydraulic fracturing equipment enters, and its resilience will keep the equipment in the center without deviation.

[0045] The clamp 6 is thinner at the entrance, so the hydraulic fracturing equipment can enter easily. During the entry process, the clamp gradually thickens, thereby fixing the position of the hydraulic fracturing equipment. When the hydraulic fracturing equipment is lifted up after the test, the diameter of the equipment is slightly larger than the diameter circle formed by the clamp at the exit. At this time, the hydraulic fracturing equipment will come out with the variable diameter centering device.

[0046] The present invention also provides a method for using the above-mentioned variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing, comprising the following steps:

[0047] Step 1: After the hole is drilled, the above-mentioned variable diameter centering device for non-vertical hole hydraulic fracturing ground stress test is placed into the hole mouth of the large borehole with a diameter of 130 mm.

[0048] Step 2: Place the hydraulic fracturing equipment into the variable diameter centering device for non-vertical hole hydraulic fracturing stress testing, push the device into the hole to the junction of the upper sleeve and the lower sleeve, then continue to push the hydraulic fracturing equipment forward, the hydraulic fracturing equipment just enters the hole in the center, and then reaches the predetermined position of the test.

[0049] Step 3: After the test is completed, start to extract the hydraulic fracturing equipment upwards. When the equipment reaches the variable diameter centering device for non-vertical hole hydraulic fracturing stress test at the junction of the variable diameter, the hydraulic fracturing equipment will come out of the hole together with the device.

[0050] The present invention pushes the hydraulic fracturing device and the sleeve together to the predetermined position. After the installation device reaches the predetermined position, the hydraulic fracturing device continues to be lowered. At this time, the hydraulic fracturing device passes through the centering device and is lowered into the drilling test section. After the test is completed, the hydraulic fracturing device begins to be lifted. At this time, the self-tightening centering device can be taken out of the hole with the device, and the lower part of the device will clamp the hydraulic fracturing device to ensure that it does not deviate.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A variable diameter centering device for non-vertical hole hydraulic fracturing ground stress testing, characterized in that: The invention comprises a sleeve assembly and a self-tightening centering assembly. The sleeve assembly comprises an upper sleeve (1) and a plurality of pulleys (2). The pulleys (2) are semi-embedded in the outer wall of the upper sleeve (1) through a wheel shaft. The self-tightening centering assembly comprises a lower sleeve (3), a plurality of axial telescopic springs (4), a plurality of radial telescopic springs (5), a plurality of clips (6), and a rear cover (7). The upper sleeve (1) and the lower sleeve (3) are connected as a whole. The inner diameter of the upper sleeve (1) is smaller than the inner diameter of the lower sleeve (3), so that the upper sleeve (1) and the lower sleeve (3) are connected as a whole. A step is formed at the connection of the lower sleeve (3), and a plurality of clips (6) are radially distributed inside the lower sleeve (3). One end of an axial telescopic spring (4) is connected to the step at the bottom of the upper sleeve (1), and the other end is connected to a top end of the clip (6). One end of a radial telescopic spring (5) is fixed to the inner wall of the lower sleeve (3), and the other end is connected to the side wall of the clip (6), so that the clip (6) is elastically suspended inside the lower sleeve (3). A rear cover (7) with a through hole is located at the bottom of the lower sleeve (3).

2. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1 is characterized in that: The upper sleeve (1) is a hollow cylinder, connected to the self-tightening centering component via a thread, with an inner diameter larger than the outer diameter of the hydraulic fracturing equipment and an outer diameter smaller than the borehole diameter.

3. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1 is characterized in that: The outer wall of the upper sleeve (1) is provided with a groove, and the pulley (2) is embedded in the outer wall of the upper sleeve through the wheel shaft, half of the pulley is located in the groove of the outer wall of the upper sleeve, and the other half is exposed and can be tangent to the inner wall of the drill hole.

4. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 3 is characterized in that: The pulleys (2) are axially distributed into three groups, and each group of pulleys (2) has four pulleys evenly distributed in the radial direction.

5. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1 is characterized in that: The axial spring (4) is evenly distributed in the circumferential direction along the groove on the bottom step of the upper sleeve, and the other end of the axial spring (4) is connected to the groove at the top end of the clip (6).

6. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1, characterized in that: The clip (6) is wedge-shaped and is distributed circumferentially inside the centering device. The clip (6) is thinner on the side facing the upper sleeve, and gradually becomes thicker on the side facing the self-tightening centering component.

7. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1, characterized in that: The top end of the clip (6) is provided with an axial groove, and the radial side wall is provided with a radial groove, the axial groove is connected to the axial telescopic spring, and the radial groove is connected to the radial telescopic spring (5).

8. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 7, characterized in that: One side of the radial telescopic spring (5) is connected to the radial groove of the clamping piece (6), and the other side is connected to the groove on the inner wall of the lower sleeve (3).

9. The variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to claim 1, characterized in that: The rear cover (7) is connected to the lower sleeve (3) on one axial side via a thread, and has an inner diameter greater than the outer diameter of the hydraulic fracturing device and an outer diameter smaller than the borehole diameter.

10. The method for using the variable diameter centering device for non-vertical hole hydraulic fracturing in-situ stress testing according to any one of claims 1 to 9, characterized in that: The steps include: Step 1: In a non-vertical hydraulic fracturing borehole to be measured, a non-vertical borehole hydraulic fracturing ground stress test variable diameter centering device is placed in the borehole, with the end slightly protruding out of the borehole; Step 2: Place the hydraulic fracturing device into the variable diameter centering device for hydraulic fracturing in-situ stress testing of non-vertical holes, push the device into the junction of the upper sleeve and the lower sleeve in the hole, and then continue to push the hydraulic fracturing device forward, the clamp forms a conical channel to clamp the hydraulic fracturing device, the device just enters the hole in the center, and then reaches the predetermined position of the test; Step 3: After the installation device reaches the predetermined position, the test is completed and the hydraulic fracturing equipment is extracted upward. When the equipment reaches the variable diameter centering device for hydraulic fracturing stress test in non-vertical holes at the junction of the variable diameters, the hydraulic fracturing equipment reaches the outside of the conical small opening formed by the clamp and exits the hole together with the centering device.

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