Heating pressure control type crustal stress measuring device and method

Abstract

The invention provides a heating pressure control type ground stress measuring device and method, and the device comprises a derrick arranged right above a hole, the derrick is connected with a central connecting rod through a traction cable, a pulley block and a winch, the tail end of the bottom of the central connecting rod is provided with a unit testing barrel, and the middle part of the central connecting rod is provided with a miniature vibration motor; and the stress sheet in the unit test barrel is connected with the sensor, the dynamic strain acquisition instrument and the computer controller through the three-core shielding wire. According to the device, the stress can be adjusted through temperature control, the mode that the linear expansion coefficient of heated aluminum metal particles is high is innovatively adopted as a power source instead of external large pressurization equipment, the measurement cost is effectively saved, the problem of pressure leakage of a fracturing section is avoided, the measurement scale is reduced, and the measurement accuracy is improved. And the measurement efficiency of the ground stress is improved.

Description

Technical Field

[0001] The present invention is applicable to the technical field of ground stress measurement, and in particular relates to a heating pressure-controlled ground stress measurement device and method. Background Art

[0002] Geostress refers to a natural force that objectively exists in the crust and rock mass and is not disturbed by engineering, also known as original rock stress. It is the fundamental force that causes deformation, fracture, folding and even earthquakes in the crust and rock mass. Geostress measurement provides a basis for scientific and reasonable excavation design and construction of various rock mass projects. At the same time, the geostress state is also of great significance to earthquake prediction, regional crust stability evaluation, stability of oil fields and wells, nuclear waste storage, rock bursts, coal and gas outbursts, and geodynamics research.

[0003] At present, the main method used to measure geostress in my country is the hydraulic fracturing method introduced from the United States after the 1980s. The hydraulic fracturing method refers to selecting two packers that match the diameter of the measured borehole. The packers are made of aluminum alloy plates and can expand after water injection and pressurization. The packers are sent to the selected borehole section to be measured with a drill pipe and pressurized and sealed. After that, the sealed section to be measured is pressurized to fracture the borehole wall. The geostress value of the measured depth area is calculated based on the data collected in this process and the fracturing curve. The main stress direction can be determined based on the cracking direction of the borehole wall measured by the impression device or ultrasonic drilling borehole wall detector. However, the hydraulic fracturing method not only has high requirements for equipment and relatively high measurement costs, but also has high requirements for the measurement environment. In addition, the waste liquid produced by the hydraulic fracturing method cannot be recycled and easily causes water pollution problems. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a heating and pressure-controlled ground stress measurement device and method. This device can adjust the magnitude of stress by temperature control, and the present invention innovatively adopts the method of heating aluminum metal particles with a high linear expansion coefficient as a power source, rather than external large-scale pressurizing equipment, which effectively saves measurement costs, avoids the problem of pressure leakage in the fracturing section, reduces the measurement scale, and improves the measurement efficiency of ground stress. Secondly, aluminum metal particles with a high linear expansion coefficient are used as the power source for rock fracture. Compared with traditional fracturing fluids, it can be recycled and effectively avoids environmental pollution. Secondly, the traditional hydraulic fracturing method can only measure the magnitude and direction of the minimum principal stress perpendicular to the borehole plane, while the present device can measure stress data values ​​in all directions.

[0005] In order to realize the above-mentioned technical features, the purpose of the present invention is achieved as follows: a heating and pressure-controlled ground stress measuring device, comprising a derrick arranged directly above a hole, the derrick being connected to a central connecting rod through a traction rope, a pulley block and a winch, a unit test barrel being installed at the bottom end of the central connecting rod, and a micro vibration motor being installed at the middle part of the central connecting rod; the stress sheet inside the unit test barrel is connected to a sensor, a dynamic strain collector and a computer controller through a three-core shielded cable.

[0006] The unit test tube has three layers from inside to outside, the inner layer is placed with a stainless steel electric heating tube, the middle layer is placed with aluminum metal particles and wrapped by an aluminum metal bag, and the outer layer of the aluminum metal bag is arranged with ceramic fiber cloth and stress sheets.

[0007] The winch is fixed on the foundation at the top of the hole through a winch base; The winch is connected to the electric control box and controls the lifting and lowering action of the central connecting rod.

[0008] The unit test barrel and the micro vibration motor are both extended into the interior of the fracturing section to be tested.

[0009] The outer layer of the ceramic fiber cloth is provided with an aluminum alloy plate, the inner side of the aluminum alloy plate is coated with heat insulation paint, the outer side is covered with steel nails, and the unit test tube is wrapped with a metal mesh as a whole.

[0010] The stress sheets are evenly arranged in multiple layers between the ceramic fiber cloth and the aluminum alloy plate.

[0011] The method for measuring ground stress using the heating pressure-controlled ground stress measuring device comprises the following steps: Step 1: Assembly of the unit test tube: The unit test cylinder and the micro vibration motor are connected in series from bottom to top through the central connecting rod, and a stainless steel electric heating tube, an aluminum metal bag, and a ceramic fiber cloth are placed in the unit test cylinder. A stress sheet is arranged inside the aluminum alloy plate and the stress sheet is led out through a three-core shielded wire. Step 2: Overall installation of the entire test device: The central connecting rod of the installed unit test tube and the micro vibration motor is supported by the ground derrick, and the unit test tube is placed in the fracturing section for measurement by the winch; Step 3: Burst pressure P b Measurements: During the measurement, the stainless steel electric heating tube is heated, and the aluminum metal particles expand due to the heat, generating an expansion force. The expansion pressure acts on the aluminum alloy plate. Since the aluminum alloy plate is covered with dense steel nails, the load of the steel nails on the fracturing section is approximately a uniformly distributed load. As the temperature increases to T0, the fracturing section ruptures. At this time, the peak pressure is recorded as the rupture pressure P b, and the rupture direction is the direction of the maximum horizontal principal stress; Step 4: Turn off the pressure P s Measurements: After the hole wall rock breaks, the pressure drops. At this time, the temperature remains at T0. When the temperature stops rising, the pressure will have a downward fracturing cycle curve. The inflection point of this curve is the instantaneous closing pressure P. s If the inflection point is difficult to judge, the tangent method or the double tangent method can be used to obtain it; Step 5: Repeated measurement of burst pressure and closing pressure: Turn off the stainless steel electric heating tube until the temperature drops to room temperature, the rock on the hole wall of the fracturing section loses the uniform load effect, and the cracks on the hole wall are completely closed; repeat steps three and four several times to obtain reasonable fracturing parameters; Step 6: Recycling of the device: After the test is completed, the stainless steel electric heating tube is turned off, and the micro vibration motor is turned on to shake off the broken rock particles that have fallen into the unit test tube, so as to facilitate the removal of the measuring device. After the measuring device is successfully removed, the micro vibration motor and the unit test tube are recycled; Step 7: Determination of the azimuth of the horizontal maximum principal stress: Lower the ultrasonic borehole wall detector to the fracturing section to determine the direction of the fracture, which is also the direction of the maximum horizontal principal stress; Step 8: Measurement of rock tensile strength T: The cores are retrieved on site and brought back to the laboratory to directly measure the rock tensile strength T using a rock tensile and compression testing machine; Step 9, measurement of initial pore pressure P0: It is found from a large number of measured results that the pore water pressure in the rock mass is basically equivalent to the hydrostatic pressure. Based on this, in actual measurement, when the pore water pressure is not measured, the hydrostatic pressure value at the measuring section can be used instead. The calculation formula for hydrostatic pressure is: P0=γ 水 H, γ 水 is the gravity of water, H is the depth at the measuring point; Step 10: Horizontal maximum principal stress σ max Measurements: According to the formula: max =T+3P s -P b -P0, find the maximum horizontal principal stress.

[0012] The present invention has the following beneficial effects: 1. The present invention innovatively adopts the method of heating aluminum metal particles with a high linear expansion coefficient as a power source instead of external large-scale pressurizing equipment, which effectively saves measurement costs, reduces measurement scale, and improves the measurement efficiency of ground stress.

[0013] 2. The present invention uses aluminum metal particles with a higher linear expansion coefficient as a power source for rock fracturing. Compared with traditional fracturing fluids, it can be recycled and effectively avoids environmental pollution.

[0014] 3. The present invention can measure stress data values ​​in various directions, while the traditional hydraulic fracturing method can only measure the magnitude and direction of the minimum principal stress perpendicular to the borehole plane.

[0015] 4. Compared with the traditional hydraulic fracturing drill pipe, the present invention adds a micro vibration motor at the central connecting rod, which can reduce the problem of the device getting stuck in the drill hole and unable to be removed.

[0016] 5. The aluminum alloy plate outside the unit test tube of the present invention is covered with iron nails, which can be approximated to a uniformly distributed load when acting on the fracturing section.

[0017] 6. Compared with the traditional hydraulic fracturing device, the present invention has a simple structure, light weight, and is reusable, and has extensive practical significance and application value in engineering.

[0018] 7. Compared with the traditional hydraulic fracturing method, the present invention can control the pressure by increasing or decreasing the temperature, while the traditional hydraulic fracturing method cannot control the pressure, and the fracturing section often causes pressure leakage due to sealing problems of the packer, and the present invention can avoid the above problems.

[0019] 8. Compared with the traditional hydraulic fracturing method, the present invention can also measure the state of the annular stress field in the fracturing section through the stress plate on the unit test tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0021] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0022] Figure 2 This is a cross-sectional view of the unit test tube.

[0023] Figure 3 Schematic diagram of the layout of the unit test cylinder.

[0024] In the figure: winch 1, electric control box 2, winch base 3, derrick 4, central connecting rod 5, unit test tube 6, micro vibration motor 7, sensor 8, dynamic strain collector 9, computer controller 10, fracturing section 11, metal mesh 12, stainless steel electric heating tube 13, aluminum metal bag 14, aluminum metal particles 15, aluminum alloy plate 16, stress sheet 17, ceramic fiber cloth 18, three-core shielded wire 19. DETAILED DESCRIPTION

[0025] The embodiments of the present invention are further described below in conjunction with the accompanying drawings.

[0026] Embodiment 1: See also Figure 1-3 , a heating and pressure-controlled ground stress measuring device, including a derrick 4 arranged just above the hole, the derrick 4 is connected to a central connecting rod 5 through a traction rope, a pulley block and a winch 1, a unit test barrel 6 is installed at the bottom end of the central connecting rod 5, and a micro vibration motor 7 is installed in the middle part of the central connecting rod 5; the stress sheet 17 inside the unit test barrel 6 is connected to the sensor 8, the dynamic strain collector 9 and the computer controller 10 through a three-core shielded wire 19. Specifically, the data line connected to the stress sheet 17 is connected to the data collection and computer in turn, and the computer has built-in data conversion software that can save and process data. By adopting this device and method, the problem of cumbersome traditional ground stress measurement is well solved, the measurement cost is effectively saved, the measurement scale is reduced, and the measurement efficiency of ground stress is improved; in addition, the device and method provided by the present invention are simple and convenient to operate, can be recycled and reused, and have broad engineering practice significance and application prospects.

[0027] Furthermore, the rock tensile strength T needs to be sampled on site and brought back to the laboratory for rock tensile and compression testing. After sampling, the debris in the in-situ stress measurement hole should be cleaned up.

[0028] Furthermore, the stress gauge 17 is generally welded with twisted pair wires, but the resistance of wires longer than 2 meters has a significant impact on the measurement results, so the stress gauge is connected to the sensor using a three-core shielded wire. The strain gauge is connected to the sensor using a three-core shielded wire 19 to reduce the impact of resistance on the data.

[0029] Furthermore, the unit test tube 6 has three layers from inside to outside, the inner layer is placed with a stainless steel electric heating tube 13, the middle layer is placed with aluminum metal particles 15 and is wrapped by an aluminum metal bag 14, and the outer layer of the aluminum metal bag 14 is arranged with ceramic fiber cloth 18 and stress sheets 17.

[0030] Furthermore, the unit test tube 6 is composed of a splicing structure and can be disassembled; the ceramic fiber cloth can achieve a good heat insulation effect.

[0031] Furthermore, the hoist 1 is fixed on the foundation at the top of the hole through the hoist base 3. Through the above fixing method, the reliability of the fixed installation of the hoist 1 is guaranteed.

[0032] Furthermore, the hoist 1 is connected to the electric control box 2, and controls the lifting and lowering of the central connecting rod 5. The electric control box 2 is convenient for controlling the movement of the hoist 1, and further controlling the lifting and lowering of the central connecting rod 5.

[0033] Furthermore, the holes of the fracturing section 11 are drilled by a drilling machine, and the size of the holes is determined according to the actual ground stress measurement hole size.

[0034] Furthermore, the unit test barrel 6 and the micro vibration motor 7 are both extended into the interior of the fracturing section 11 to be tested.

[0035] Furthermore, the outer layer of the ceramic fiber cloth 18 is provided with an aluminum alloy plate 16, the inner side of the aluminum alloy plate 16 is coated with heat-insulating paint, the outer side is covered with steel nails, and the unit test tube 6 is entirely wrapped by the metal mesh 12. The aluminum metal particles 15 can cover the aluminum metal bag 14, and the ceramic fiber cloth 18 has a good high temperature resistant heat insulation effect.

[0036] Furthermore, the stress sheets 17 are evenly arranged in multiple layers between the ceramic fiber cloth 18 and the aluminum alloy plate 16 .

[0037] Embodiment 2: The method for measuring ground stress using the heating pressure-controlled ground stress measuring device comprises the following steps: Step 1: Assembly of the unit test tube 6: The unit test tube 6 and the micro vibration motor 7 are connected in series from bottom to top through the central connecting rod 5, and a stainless steel electric heating tube 13, an aluminum metal bag 14, and a ceramic fiber cloth 18 are placed in the unit test tube 6, and a stress sheet 17 is arranged inside the aluminum alloy plate 16, and the stress sheet 17 is led out through a three-core shielded wire 19; Step 2: Overall installation of the entire test device: The central connecting rod 5 with the installed unit test tube 6 and the micro vibration motor 7 is supported by the ground derrick 4, and the unit test tube 6 is placed in the fracturing section 11 by the winch 1 for measurement; Step 3: Burst pressure P b Measurements: During the measurement, the stainless steel electric heating tube 13 is heated, and the aluminum metal particles 15 expand due to the heat to generate expansion force. The expansion pressure acts on the aluminum alloy plate 16. Since the aluminum alloy plate 16 is covered with dense steel nails, the load of the steel nails on the fracturing section 11 is approximately a uniformly distributed load. As the temperature increases to T0, the fracturing section ruptures. At this time, the pressure peak is recorded as the rupture pressure P b , and the rupture direction is the direction of the maximum horizontal principal stress; Step 4: Turn off the pressure P s Measurements: After the hole wall rock breaks, the pressure drops. At this time, the temperature remains at T0. When the temperature stops rising, the pressure will have a downward fracturing cycle curve. The inflection point of this curve is the instantaneous closing pressure P. sIf the inflection point is difficult to judge, the tangent method or the double tangent method can be used to obtain it; Step 5: Repeated measurement of burst pressure and closing pressure: Close the stainless steel electric heating tube 13 until the temperature drops to room temperature, the rock on the hole wall of the fracturing section loses the uniform load effect, and the cracks on the hole wall are completely closed; repeat steps 3-4 multiple times to obtain reasonable fracturing parameters; Step 6: Recycling of the device: After the test is completed, the stainless steel electric heating tube 13 is turned off, and the micro vibration motor 9 is turned on to shake off the broken rock particles that have fallen into the unit test tube 6, so as to facilitate the removal of the measuring device. After the measuring device is successfully removed, the micro vibration motor 7 and the unit test tube 6 are recycled; Step 7: Determination of the azimuth of the horizontal maximum principal stress: Lower the ultrasonic borehole wall detector to the fracturing section to determine the direction of the fracture, which is also the direction of the maximum horizontal principal stress; Step 8: Measurement of rock tensile strength T: The cores are retrieved on site and brought back to the laboratory to directly measure the rock tensile strength T using a rock tensile and compression testing machine; Step 9, measurement of initial pore pressure P0: It is found from a large number of measured results that the pore water pressure in the rock mass is basically equivalent to the hydrostatic pressure. Based on this, in actual measurement, when the pore water pressure is not measured, the hydrostatic pressure value at the measuring section can be used instead. The calculation formula for hydrostatic pressure is: P0=γ 水 H, γ 水 is the gravity of water, H is the depth at the measuring point; Step 10: Horizontal maximum principal stress σ max Measurements: According to the formula: max =T+3P s -P b -P0, find the maximum horizontal principal stress.

Claims

1. A heating and pressure-controlled ground stress measuring device, characterized in that: The invention comprises a derrick (4) arranged directly above the hole, the derrick (4) being connected to a central connecting rod (5) via a traction rope, a pulley block and a winch (1), a unit test barrel (6) being installed at the bottom end of the central connecting rod (5), and a micro vibration motor (7) being installed at the middle part of the central connecting rod (5); a stress sheet (17) inside the unit test barrel (6) being connected to a sensor (8), a dynamic strain collector (9) and a computer controller (10) via a three-core shielded wire (19).

2. A heating and pressure-controlled ground stress measuring device according to claim 1, characterized in that: The unit test tube (6) has three layers from the inside to the outside, the inner layer is provided with a stainless steel electric heating tube (13), the middle layer is provided with aluminum metal particles (15) and is wrapped by an aluminum metal bag (14), and the outer layer of the aluminum metal bag (14) is provided with a ceramic fiber cloth (18) and a stress sheet (17).

3. The heating and pressure-controlled ground stress measuring device according to claim 1, characterized in that: The winch (1) is fixed on the foundation at the top of the hole via a winch base (3); The hoist (1) is connected to the electric control box (2) and controls the lifting and lowering movement of the central connecting rod (5).

4. A heating and pressure-controlled ground stress measuring device according to claim 1, characterized in that: The unit test barrel (6) and the micro vibration motor (7) are both inserted into the interior of the fracturing section (11) to be tested.

5. The heating and pressure-controlled ground stress measuring device according to claim 2, characterized in that: The outer layer of the ceramic fiber cloth (18) is provided with an aluminum alloy plate (16), the inner side of the aluminum alloy plate (16) is fully coated with heat-insulating paint, the outer side is fully covered with steel nails, and the unit test cylinder (6) is entirely wrapped with a metal mesh (12).

6. A heating and pressure-controlled ground stress measuring device according to claim 5, characterized in that: The stress sheets (17) are evenly arranged in multiple layers between the ceramic fiber cloth (18) and the aluminum alloy plate (16).

7. A method for measuring ground stress using a heating and pressure-controlled ground stress measuring device according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Assembly of the unit test tube (6): A unit test tube (6) and a micro vibration motor (7) are connected in series from bottom to top in sequence through a central connecting rod (5), and a stainless steel electric heating tube (13), an aluminum metal bag (14), and a ceramic fiber cloth (18) are placed in the unit test tube (6), and a stress sheet (17) is arranged inside the aluminum alloy plate (16), and the stress sheet (17) is led out through a three-core shielded wire (19); Step 2: Overall installation of the entire test device: The central connecting rod (5) on which the unit test tube (6) and the micro vibration motor (7) are installed is supported by a ground derrick (4), and the unit test tube (6) is placed in the fracturing section (11) by a winch (1) for measurement; Step 3: Burst pressure P b Measurements: During the measurement process, the stainless steel electric heating tube (13) is heated, and the aluminum metal particles (15) expand due to the heat, generating an expansion force. The expansion pressure acts on the aluminum alloy plate (16). Since the aluminum alloy plate (16) is densely covered with steel nails, the load of the steel nails on the fracturing section (11) is approximately a uniformly distributed load. As the temperature increases to T0, the fracturing section ruptures. At this time, the peak pressure is recorded as the rupture pressure P b , and the rupture direction is the direction of the maximum horizontal principal stress; Step 4: Turn off the pressure P s Measurements: After the hole wall rock breaks, the pressure drops. At this time, the temperature remains at T0. When the temperature stops rising, the pressure will have a downward fracturing cycle curve. The inflection point of this curve is the instantaneous closing pressure P. s If the inflection point is difficult to judge, the tangent method or the double tangent method can be used to obtain it; Step 5: Repeated measurement of burst pressure and closing pressure: The stainless steel electric heating tube (13) is turned off until the temperature drops to room temperature, the rock on the hole wall of the fracturing section loses the uniform load effect, and the cracks on the hole wall are completely closed; steps three and four are repeated multiple times to obtain reasonable fracturing parameters; Step 6: Recycling of the device: After the test is completed, the stainless steel electric heating tube (13) is turned off, and the micro vibration motor (9) is turned on to shake off the broken rock particles that have fallen into the unit test tube (6) to facilitate the removal of the measuring device. After the measuring device is successfully removed, the micro vibration motor (7) and the unit test tube (6) are recycled; Step 7: Determination of the azimuth of the horizontal maximum principal stress: Lower the ultrasonic borehole wall detector to the fracturing section to determine the direction of the fracture, which is also the direction of the maximum horizontal principal stress; Step 8: Measurement of rock tensile strength T: The cores are retrieved on site and brought back to the laboratory to directly measure the rock tensile strength T using a rock tensile and compression testing machine; Step 9, measurement of initial pore pressure P0: It is found from a large number of measured results that the pore water pressure in the rock mass is basically equivalent to the hydrostatic pressure. Based on this, in actual measurement, when the pore water pressure is not measured, the hydrostatic pressure value at the measuring section can be used instead. The calculation formula for hydrostatic pressure is: P0=γ 水 H, γ 水 is the gravity of water, H is the depth at the measuring point; Step 10: Horizontal maximum principal stress σ max Measurements: According to the formula: max =T+3P s -P b -P0, find the maximum horizontal principal stress.

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