Device for testing rock hardness

Abstract

FIELD: mining.SUBSTANCE: invention can be used to determine the hardness of rocks drilled with diamond bits equipped with PDC cutters (Polycrystalline Diamond Compact, which in Russian means polycrystalline diamond composite). The device comprises a table for placing a sample, a mechanism for moving the table in the horizontal direction, a vertical stand on which a console configured for vertical movements is mounted, a mechanism for pressing an indenter under the action of a load, a microscope, a micrometre eyepiece, and a video camera. A polycrystalline diamond plate of a PDC cutter is used as an indenter; in addition, there is a mandrel for fixing the PDC cutter, connected to the indenter pressing mechanism. The device additionally comprises a mechanism for rotating and fixing the indenter in the horizontal plane by 180° and in the vertical plane by 90°.EFFECT: assessing the hardness of rocks by scratching them with a polycrystalline diamond plate of a PDC cutter under a given load at different temperatures; in addition, the claimed device makes it possible to assess the energy density of destruction of rocks in units of energy consumption per volume of displaced rock [J / mm3].3 cl, 2 dwg

Description

[0001] Technical field

[0002] The invention relates to mining and can be used to determine the hardness of rocks drilled with diamond bits equipped with PDC cutters (Polycrystalline Diamond Compact, which in Russian means polycrystalline diamond composite).

[0003] Technology Level

[0004] A similar device is known for the standard assessment of the hardness of materials according to Brinell [GOST 23677-79. Metal hardness testers. General technical requirements - M.: Publishing house of standards, 1979.-13 p.], consisting of a table (or stand) on which the sample is placed, a steel ball, which is used as an indenter, and a mechanism for pressing the ball into the sample under a given load.

[0005] The disadvantage of this device is the low reliability of the indenter in assessing the hardness of rocks due to insufficient strength, wear resistance and non-repairability, in addition, the device is not functional enough, since it cannot be used to determine the energy density of rock destruction when scratching with a PDC cutter, as well as to determine the energy density of rock destruction when scratching with a PDC cutter, and also does not allow for hardness assessment at different temperatures.

[0006] Another analogue is the device for assessing the microhardness of materials using the Vickers method PMT-3M [Vickers microhardness testers Vostok-7 models PMT-3 and PMT-3M SI number in the state register of the Russian Federation: 86208-22 Operation manual with a passport and verification method (PM-PS, PM-RE and PM-MP) 2023.-50c.] (SI number in the state register of the Russian Federation: 86208-22). This device includes a table for placing a sample, a mechanism for moving the table in the horizontal direction, a vertical stand on which a console with the possibility of vertical movements is installed, a mechanism for pressing an indenter under the action of a load (a Vickers diamond pyramid with an interface angle at the apex of 136° is used as an indenter) and a microscope with a digital video camera, specialized software for controlling the testing process, performing functional tasks, storing, statistical processing and displaying measurement results on a personal computer.

[0007] The disadvantage of this device is the low reliability of the indenter when assessing the hardness of rocks due to its fragility and non-repairability. In addition, the device is not functional enough, since it cannot be used to determine the energy density of rock destruction when scratching with a PDC cutter, as well as to determine the energy density of rock destruction when scratching with a PDC cutter, and also does not allow for hardness assessment at different temperatures.

[0008] The PMT-3M microhardness tester was selected as a prototype. It can be used as a device for measuring microhardness by scratching with diamond tips [GOST 21318-75. Measuring microhardness by scratching with diamond tips. - M .: Publishing house of standards, 1976.- 30 p.]. The device includes a table for placing a sample, a mechanism for moving the table in the horizontal direction, a vertical stand on which a console with the possibility of vertical movement is mounted, a mechanism for pressing an indenter under the action of a load, a microscope, a micrometer eyepiece, a video camera, and specialized software.

[0009] The disadvantage of this device is the low reliability of the indenter when assessing the hardness of rocks due to insufficient brittleness and non-repairability, in addition, the device is not functional enough, since it cannot be used to determine the energy density of rock destruction when scratching with a PDC cutter, as well as to determine the energy density of rock destruction when scratching with a PDC cutter, and also does not allow for hardness assessment at different temperatures.

[0010] Disclosure of the essence of the invention

[0011] The technical result of the present invention is to increase the reliability of the indenter in assessing the hardness of rocks and to increase the functionality of the device by providing the ability to assess the energy density of rock destruction in units of energy consumption per volume of displaced rock [J / mm 3 ], as well as providing the ability to assess the hardness of rocks at different temperatures.

[0012] The technical result is achieved in that in the claimed device for testing rock hardness with software, including a table for placing a sample, having the ability to move in the horizontal direction, a vertical stand on which a console is mounted with the ability to move vertically, equipped with a rod holding a load in the upper part and with a mandrel for an indenter in its lower part, a mechanism for pressing the indenter under the action of a load, a microscope, a micrometer eyepiece, a video camera, a feature is that it is additionally equipped with a tangential force sensor that records the force load on the sample, a mechanism for rotating and fixing the indenter mandrel in the horizontal and vertical plane, while the table is equipped with a heater for heating the sample and has the ability to move at a given speed, the mandrel for fixing the indenter is equipped with a hinge connected to the pressing mechanism,A polycrystalline diamond plate (PDC) is used as the indenter. The mandrel rotation and locking mechanism can rotate 180° horizontally and 90° vertically. The table can move at speeds of up to 6.7 m / s.

[0013] Brief description of drawings

[0014] Figure 1 shows the design of the claimed device, where the following is shown: table 1; stand 2; sleeve 3; sleeve lock 4; rotary bracket 5; bracket lock 6; digital microscope 7; digital microscope focusing screw 8; guide sleeve 9; rod 10; support bar 11; weight 12; rod tip 13; PDC cutter mandrel 14; PDC cutter 15; ball joint lock 16; tangential force sensor 17; guide screw 18; carriage 19; rock sample 20; guide pin 21; pusher screw 22; pusher nut 23; handle 24; heater 25.

[0015] Fig. 2 shows a diagram relating the groove width, groove depth and hardness value.

[0016] The device for testing the hardness of rocks comprises a table 1 with a built-in stand 2, on which a rotary bracket 5 is fixed with the help of a sleeve 3 and a sleeve lock 4. On one side of the rotary bracket, a digital microscope 7 with a digital microscope focusing screw 8 is fixed, and on the other side, the bracket has a vertical hole into which a guide sleeve 9 is pressed, into which a rod 10 is inserted with the possibility of vertical movement along the guide sleeve 9 along the guide groove, into which a guide screw 18 enters. In the upper part of the rod 10, above the bracket, a load 12 is located, resting on a support bar 11 and limited from above by the tip of the rod 13.In the lower part of the rod 10, under the rotary bracket 5, there is a tangential force sensor 17, and the lower part of the rod 10 is made in the form of a fork, which, with the help of the ball joint lock 16, holds in a given position the ball joint connected with the mandrel of the PDC cutter 14, in which the PDC cutter 15 is fixed with the possibility of rotation relative to the axis of the PDC cutter 15. Under the PDC cutter 15 there is a rock sample 20, which is installed on the heater 25, located on the carriage 19. In the lower part of the carriage there are two guide pins 21, inserted into the groove of the table 1. On the carriage 19 there is a ledge for the stop of the screw-pusher 22, connected with the nut of the pusher 23, fixed on the table 1. At the other end of the screw-pusher 22 there is a handle 24.

[0017] Since rock drilling is carried out in high-temperature conditions determined by geothermal conditions and drilling modes, a heater has been added to the device, allowing samples to be heated to 90°C. Ceramic heaters operating from a 220V network, equipped with power controllers calibrated in degrees Celsius, can be used for this purpose.

[0018] The practicality of using PDC cutters as diamond indenters is due to the fact that the device simulates the process of rock cutting at the bottomhole during well drilling. The resistance of the rock (hardness) to the penetration of this type of indenter determines the drilling speed. Furthermore, PDC cutters, equipped with a polycrystalline diamond plate, are more resistant to dynamic loads than single-crystal diamond indenters and are less expensive and readily available. In the event of breakage, a PDC cutter can be easily restored by rotating it in a holder, placing an unworn cutting edge in the working area. This allows the device to use cutters that have been used at the bottomhole and still have some intact cutting edges.

[0019] The claimed device is equipped with a rotary mechanism that allows, using a ball joint lock 16, which holds the ball joint in a given position, connected to the PDC cutter mandrel 14, in which the PDC cutter 15 is fixed, to adjust the angle of inclination of the cutter relative to the rock sample in the horizontal plane by 180° and in the vertical plane by 90°.

[0020] Since the design of the bits provides for the installation of PDC cutters at different angles relative to the rock at the bottomhole, the claimed device makes it possible to study the influence of the position of the cutter relative to the rock sample on the resistance of the sample to the penetration of the PDC cutter into the sample at the above angles when determining the hardness of the sample.

[0021] Implementation of the invention

[0022] The device operates as follows.

[0023] To evaluate the hardness of a rock, a specimen is taken that has two parallel surfaces, formed, for example, by cutting or grinding. The upper surface is used for hardness testing, while the lower surface ensures good contact with the surface of heater 25 for rapid and uniform heating of the specimen.

[0024] The rock sample 20 is mounted on the heater 25, which is secured to the carriage 19. The carriage 19 can be moved in the horizontal direction using the pusher screw 22, which is rotated by the handle 24. The guide pins 21 ensure smooth and precise movement of the carriage 19 relative to the table 1.

[0025] Instead of manually moving the rock sample, an electric drive rotating the pusher screw 22 can be used. This allows the rock sample to be scratched at a speed close to the cutting speed of a diamond bit at the face, bringing the rock breaking conditions of a diamond cutter in the laboratory closer to the operating conditions of a diamond bit at the face. For example, in a 215.9 mm diameter diamond bit rotating at 600 rpm, the peripheral row of PDC cutters moves along the face at a speed of 6.7 m / s. Therefore, an electric drive capable of moving the sample at a speed of up to 6.7 m / s is selected.

[0026] Before testing, the polycrystalline diamond plate of the PDC cutter – PDC cutter 15 is fixed in the PDC cutter holder 14, setting it at the required angle using the ball joint lock 16. The angle of inclination of the cutter can be adjusted in the horizontal plane (180°) and the vertical plane (90°), which allows simulating various conditions of contact of the indenter with the rock, corresponding to real drilling conditions.

[0027] After installing the rock sample 20 and the PDC cutter 15, loading can be carried out by placing the load 12 on the support bar 11 of the rod 10. Under the action of the weight of the load, the rod 10 moves downward, transmitting the force through the tangential force sensor 17 to the mandrel of the PDC cutter 14 with the PDC cutter 15, which is pressed into the rock sample 20.

[0028] The device allows recording the furrow width obtained during the experiment using a digital microscope 7. The obtained data allows calculating the geometric parameters of the furrow and the volume of displaced rock.

[0029] The ability to set different temperature conditions using heater 25 allows testing at temperatures up to 90°C, simulating the conditions of the well bottom.

[0030] The force characteristics of the cutting process are recorded by the tangential force sensor 17, which makes it possible to evaluate the work of rock destruction in units of energy per unit volume (J / mm³).

[0031] Based on the measurements of the groove depth and width, a diagram is constructed (Fig. 2) linking the geometric parameters of the indenter penetration with the rock hardness. This allows us to determine:

[0032] - hardness of rock at a given temperature;

[0033] - density of rock destruction energy (work of destruction per unit volume);

[0034] - the influence of the cutter installation angle on the hardness and energy density of rock destruction.

[0035] Example.

[0036] The claimed device for assessing hardness by scratching was tested as follows. A PDC cutter with a diameter of 13.5 mm was used as an indenter. For rock testing, an inclination angle of 15° of the PDC cutter axis relative to the horizontal plane was selected, as this angle is typical for many PDC bits. The inclination angle of 15° of the PDC cutter axis relative to the horizontal plane was set by tilting the PDC cutter mandrel 14 and fixing it in position using the ball joint lock 16. The weight of the scratching loads was 2 kg. Rock samples belonging to the hard rock category – granite and quartzite (6-7 units on the Mohs scale), drilling of which causes rapid wear of PDC cutters – were prepared. The samples were alternately placed on a heater and heated to a temperature of 71°C (corresponding to a rock depth of 2 km).Scratches were made on the surface of the samples, and using a digital microscope connected to a computer, the scratch widths were determined from the images on the screen. The scratch widths were 595 µm for granite and 388 µm for quartzite. The hardness of the rocks was determined from the diagram (Fig. 2): 5050 MPa for granite and 15600 MPa for quartzite.

[0037] The fracture energy density W was determined as the ratio of the cutting work of the rock A р =F ц ⋅L by the scratch volume V ц =S⋅L, where L is the scratch length [m], F ц – scratching force [N], S – cross-sectional area of ​​the scratch [m 2 ]. Thus, W= (F ц ⋅L) / ( S⋅L)= F ц / S. The scratch force was determined using a tangential force sensor. For granite, the scratch force was 147 N, and for quartzite – 196 N. The cross-sectional area of ​​the scratch was estimated graphically. For this, a frontal projection of the cutter's PDC was constructed and, based on the scratch depth, which was determined from the diagram (Fig. 2) using previously determined scratch width values, the frontal projection of the cutter-rock contact area was estimated, which is equal to the cross-sectional area of ​​the groove S. These areas were 2.612⋅10 for granite. -9 m 2 , and for quartzite – 0.719⋅10 -9 m 2 Thus, the destruction energy density for granite was 0.56⋅10 -7 J / m 3 , and for quartzite – 2.72⋅10 -7 J / m 3 .

[0038] In the claimed invention, the reliability of the indenter is increased by using a stronger and more durable material - polycrystalline diamond, which is used in drilling wells, and repairability is achieved due to the ability to replace a worn section of the PDC cutter edge with an unworn section by rotating the PDC around its axis.

[0039] The claimed device has broader functional capabilities - it provides the ability to assess the energy density of rock destruction in units of energy consumption per volume of displaced rock [J / mm 3 ] thanks to the presence of a tangential force sensor and the ability to evaluate the geometric characteristics of a scratch.

Claims

1. A device for testing rock hardness with software, including a table for placing a sample, capable of movement in the horizontal direction, a vertical stand on which a console is mounted with the possibility of vertical movement, equipped with a rod holding a load in the upper part and with a mandrel for an indenter in its lower part, a mechanism for pressing the indenter under the action of the load, a microscope, a micrometer eyepiece, a video camera, characterized in that it is additionally equipped with a tangential force sensor that records the force load on the sample, a mechanism for rotating and fixing the indenter mandrel in the horizontal and vertical planes, wherein the table is equipped with a heater for heating the sample, the mandrel for fixing the indenter is equipped with a hinge connected to the pressing mechanism, and a polycrystalline diamond plate of a PDC cutter is used as an indenter.

2. The device according to paragraph 1, characterized in that the mechanism for rotating and fixing the mandrel has the ability to rotate in the horizontal plane by 180° and in the vertical plane by 90°.

3. The device according to paragraph 1, characterized in that the table has the ability to move at a speed of up to 6.7 m / s.

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