Shale core cutting device and cutting method

Abstract

The invention belongs to the technical field of rock core cutting devices, and discloses a shale core cutting device which comprises a supporting table, a cutting assembly, a rock core clamping assembly, a cutting fluid circulating assembly and a rock core pressure control assembly. The shale core is guaranteed to be in a formation pressure state during cutting in a pressurization mode, the problem that the pore structure and permeability of the shale core are changed too much due to state change and cutting pressure is solved, and recycling of cutting liquid is achieved through the cutting liquid circulating device. And the sensitivity of the shale core to the cutting fluid is reduced by controlling the mineralization degree and the temperature of the cutting fluid.

Description

Technical Field

[0001] This invention belongs to the technical field of rock core cutting devices, and particularly relates to a shale rock core cutting device and cutting method. Background Technology

[0002] Shale gas refers to natural gas found in mature, organic-rich dark mudstone or high-carbon mudstone, formed at various stages of organic origin. Shale gas typically exists as continuously generated biochemically derived gas, thermogenic gas, or a mixture of both. It exists in a free state in shale fractures, shale pores, and other reservoir spaces, or in an adsorbed state on the surface of kerogen, clay particles, and clay pores. Due to its significant extraction potential, shale gas has become a key research focus in the oil and gas sector in recent years.

[0003] Shale formations typically have low permeability, meaning gas struggles to flow within the rock. This makes shale gas extraction relatively difficult, usually requiring techniques such as horizontal wells and hydraulic fracturing. The gas in shale is primarily found in micropores, rather than the large pores of traditional natural gas reservoirs. This leads to the unique nature of shale gas extraction technology, necessitating specialized extraction methods. Shale gas is an unconventional natural gas resource, differing from traditional natural gas reservoirs. Developing shale gas requires novel technologies and engineering approaches. As formation depth increases, so does the pore pressure. Since natural gas in shale rock is mainly found in micropores, changes in pore pressure affect the permeability and release of natural gas.

[0004] When conducting research on shale oil and gas development, due to the sensitivity of shale to environmental pressure, existing technologies generally use the same environmental conditions as ordinary sandstone cores for cutting shale cores. This leads to changes in the permeability and pore structure of the core cross-section. For shale, such cutting methods can cause deviations in experimental results due to changes in the permeability and pore structure of the core cross-section. Therefore, it is necessary to design a core cutting device that is suitable for the characteristics of shale cores.

[0005] Based on the above analysis, the problems and shortcomings of the existing technology are as follows:

[0006] Existing technologies generally use the same environmental conditions as ordinary sandstone cores for cutting, which leads to changes in the permeability and pore structure of the core cross-section. For shale, this cutting method can cause deviations in experimental results due to changes in the permeability and pore structure of the core cross-section. Therefore, it is necessary to design a core cutting device that is suitable for the characteristics of shale cores. Summary of the Invention

[0007] To address the problems existing in the prior art, the present invention provides a shale core cutting device.

[0008] This invention is implemented as follows: a shale core cutting device includes:

[0009] Support platform, cutting assembly, core clamping assembly, cutting fluid circulation assembly, core pressure control assembly;

[0010] The cutting assembly includes a cutting head, a cutting motor, and a support arm. The support arm is rotatably mounted on a support platform via a rotating shaft. The cutting motor is mounted on the support arm, and the output end of the cutting motor is connected to the cutting head. The support arm drives the cutting motor and the cutting head to rotate around the rotating shaft to achieve the up-and-down movement of the cutting head.

[0011] Furthermore, the core clamping assembly includes a core clamping device one and a core clamping device two; the core clamping device one and the core clamping device two include an outer sleeve and a core clamping rubber sleeve, the core clamping rubber sleeve is sleeved inside the outer sleeve, and the core clamping rubber sleeve is provided with a liquid communication port.

[0012] Furthermore, the core clamping assembly is located inside the waste liquid collection box, at the lower part of the support arm rotation path; core clamp one and core clamp two are connected in series, and the gap between core clamp one and core clamp two allows the cutting head to pass through, which is used for cutting the core.

[0013] Furthermore, the cutting fluid circulation assembly includes a cutting fluid reservoir, a circulation pump, a nozzle, a waste fluid collection box, and a filter. The cutting fluid reservoir is equipped with a heating plate to heat the cutting fluid, ensuring that the temperature of the cutting fluid is the same as the temperature of the shale core formation, and that the salinity of the cutting fluid in the reservoir is the same as that of the formation water in the shale core. The circulation pump pumps the cutting fluid from the reservoir into the nozzle, which is located at the cutting head for rinsing the cutting head.

[0014] Furthermore, the waste liquid collection box is set on the support platform to collect the cutting fluid waste liquid during the cutting process, and the waste liquid inside the waste liquid collection box is circulated into the cutting fluid storage tank by a circulation pump. A filter is set at the inlet of the circulation pump to filter out impurities such as rock fragments in the cutting waste liquid.

[0015] Furthermore, the core pressure control component includes a constant pressure pump and a pressure sensor; the constant pressure pump is connected to the pressure sensor and is respectively connected to the liquid inlet of the core holder one and the core holder two for controlling the core pressure.

[0016] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0017] First, the main objective of this invention is to propose a shale core cutting device that is suitable for shale with low permeability and maintains the shale pressure environment, thereby overcoming the defects of existing experimental equipment in the permeability and void structure of shale core sections.

[0018] 1. The clamping force of the core holder 1 and core holder 2 on the core is controlled by a constant pressure pump to maintain the pore structure and permeability of the shale core under formation pressure, and the core is cut by a cutting blade.

[0019] 2. The cutting fluid storage tank is equipped with a heating plate to heat the cutting fluid, ensuring that the temperature of the cutting fluid is the same as the temperature of the shale core formation, and that the salinity of the cutting fluid in the storage tank is the same as that of the formation water in the shale core. This setup ensures that the cutting fluid lubricates and controls the temperature of the cutting blade, and also ensures the temperature and salinity of the core at the cutting blade cut.

[0020] 3. It is equipped with a cutting fluid circulation device, which can realize the recycling of cutting fluid with a certain degree of mineralization through the setting of circulation pump and filter.

[0021] Secondly, the technical solution of this invention fills a technological gap in the industry both domestically and internationally: precise simulation of the formation environment for core cutting. Currently, most existing core cutting equipment, both domestically and internationally, is designed for conventional sandstone cores, and cannot effectively maintain the original formation pressure, temperature, and mineralization conditions of shale cores when cutting them. This invention, through the synergistic effect of the core pressure control component and the cutting fluid circulation component, can precisely simulate the formation environment, achieving efficient protection of the pore structure and permeability of the shale core during the cutting process. This is a pioneering achievement in the field of shale core cutting, filling a technological gap and providing new technical support for shale gas development research.

[0022] This invention highly integrates multiple functional modules, including core clamping, cutting, liquid circulation, and pressure control, into a single unit, forming a complete shale core cutting solution. Compared with existing technologies, this integrated design not only improves the equipment's operating efficiency and stability but also reduces its footprint and operational complexity. This innovative design concept and integrated technology are unprecedented in the industry, effectively filling a technological gap in this field both domestically and internationally. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the shale core cutting device provided in an embodiment of the present invention.

[0024] Figure 2 This is a comparison chart of core permeability provided in an embodiment of the present invention.

[0025] Figure 3This is a comparison chart of the cutting fluid recycling rate provided in the embodiments of the present invention.

[0026] Figure 4 Temperature fluctuation diagram during the cutting process.

[0027] Figure 1 In the middle: 1. Cutting head; 2. Support arm; 3. Core holder one; 4. Waste liquid collection box; 5. Support platform; 6. Core holder two; 7. Cutting fluid storage container. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] In traditional shale core cutting processes, the complex structure of the core and its susceptibility to thermal stress, mechanical compression, and other factors often lead to problems such as core fragment collapse, microcrack propagation, and sample center displacement. These issues distort subsequent physical property testing results, severely limiting the application of high-precision formation evaluation technologies. Especially under high-pressure, high-temperature oil and gas reservoir conditions, the difference between the formation water salinity and the formation temperature exacerbates the thermodynamic mismatch between the cutting fluid and the core, increasing the risk of core damage and making it difficult for existing cutting devices to balance cutting efficiency and sample integrity. To meet the stringent requirements of shale evaluation for core cutting quality, there is an urgent need for a device system that can simultaneously achieve precise cutting and effective fluid circulation control to overcome the aforementioned technical bottlenecks in industrial applications.

[0030] This invention proposes an integrated shale core cutting device. By organically combining a support platform, cutting components, core clamping components, cutting fluid circulation components, and core pressure control components, a highly coordinated working platform is formed. Within this platform, the cutting components and clamping system achieve multi-degree-of-freedom linkage, while the closed-loop cutting fluid circulation and pressure feedback ensure that the core remains in a constant temperature and pressure state throughout the cutting process. This fundamentally suppresses crack propagation and sample movement caused by temperature gradients or sudden pressure changes, thereby significantly improving the accuracy and reproducibility of core cutting.

[0031] In terms of detailed design, the cutting assembly adopts a support arm structure with a rotating shaft. This support arm can rotate smoothly around the shaft and drive the cutting head to reciprocate up and down via a built-in high-speed cutting motor. The rotation angle and cutting depth of the support arm can be adjusted in real time by a servo motor to meet the cutting requirements of different core diameters and hardnesses. Meanwhile, the cutting head is made of an ultra-hard composite alloy, which combines wear resistance and thermal conductivity, maintaining stable cutting performance under high load conditions.

[0032] The core clamping assembly employs a series-connected double-clamp structure, with each clamp consisting of a metal outer sleeve and an inner high-elasticity rubber sleeve. The rubber sleeve is connected to a constant pressure system via a pre-set liquid inlet, allowing for dynamic adjustment of the clamping force during clamping. This ensures concentric constraint of the core and compensates for minute displacements caused by cutting forces and hydraulic fluctuations. This design guarantees stable positioning of the core during cutting while effectively preventing localized micro-crack damage caused by excessive compression.

[0033] The cutting fluid circulation system includes a temperature-controlled reservoir, a circulation pump, nozzles, and a multi-stage filtration module. The reservoir is equipped with a heating plate that matches the formation temperature and automatically adjusts the cutting fluid's salinity based on detected formation water salinity. The circulation pump delivers the optimally matched cutting fluid to the nozzles, spraying it along the cutting edge to achieve multiple functions: lubrication, cooling, and debris removal. The filters progressively trap rock debris and particles, ensuring the cleanliness of the circulating cutting fluid and preventing particles from re-entering the nozzles and causing blockages.

[0034] To further enhance core protection capabilities, the core pressure control component employs a closed-loop linkage between a constant-pressure pump and a high-precision pressure sensor to monitor and adjust the internal liquid pressure of the dual clamps in real time. Throughout the cutting process, the system automatically adjusts the constant-pressure pump output based on sensor feedback, ensuring the clamping force remains within a preset range. This prevents core loosening and avoids micro-cracks caused by overpressure. Through the synergistic effect of these components, the entire device effectively addresses multiple challenges in shale core cutting, including thermal stress, mechanical vibration, and hydraulic fluctuations, achieving high-precision and high-integrity core sample preparation.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a shale core cutting device comprising:

[0036] Support platform 5, cutting assembly, core clamping assembly, cutting fluid circulation assembly, core pressure control assembly;

[0037] The cutting assembly includes a cutting head 1, a cutting motor, and a support arm 2. The support arm 2 is rotatably mounted on a support platform 5 via a rotating shaft. The cutting motor is mounted on the support arm 2, and the output end of the cutting motor is connected to the cutting head 1. The support arm 2 drives the cutting motor and the cutting head 1 to rotate around the rotating shaft to realize the up and down movement of the cutting head 1.

[0038] The core clamping assembly includes a core clamp 3 and a core clamp 6; the core clamp 3 and the core clamp 6 include an outer sleeve and a core clamping rubber sleeve, the core clamping rubber sleeve being fitted inside the outer sleeve and having a liquid communication port; the core clamping assembly is located inside the waste liquid collection box 4, at the lower part of the rotation path of the support arm 2; the core clamp 3 and the core clamp 6 are connected in series, and the gap between the core clamp 3 and the core clamp 6 allows the cutting head 1 to pass through, for cutting the core with the cutting head 1;

[0039] The cutting fluid circulation assembly includes a cutting fluid reservoir 7, a circulation pump, a nozzle, a waste fluid collection box 4, and a filter. The cutting fluid reservoir 7 is equipped with a heating plate to heat the cutting fluid, ensuring its temperature matches the shale core formation temperature, and that the mineralization of the cutting fluid in the reservoir is the same as that of the water in the shale core formation. The circulation pump pumps the cutting fluid from the reservoir 7 into the nozzle, which is positioned at the cutting head 1 for rinsing it. The waste fluid collection box 4 is mounted on a support platform 5 to collect waste cutting fluid during the cutting process. The waste fluid inside the collection box 4 is then circulated back into the reservoir 7 by the circulation pump. A filter is installed at the inlet of the circulation pump to remove impurities such as rock fragments from the waste cutting fluid.

[0040] The core pressure control assembly includes a constant pressure pump and a pressure sensor; the constant pressure pump is connected to the pressure sensor and is also connected to the liquid inlet of the core holder 3 and the core holder 6 respectively, for controlling the core pressure.

[0041] Example 1

[0042] This embodiment provides a shale core cutting device, characterized in that it includes a support platform 5, a cutting assembly, a core clamping assembly, a cutting fluid circulation assembly, and a core pressure control assembly. The cutting assembly consists of a cutting head 1, a cutting motor, and a support arm 2. The support arm 2 can rotate around the support platform 5 via a rotating shaft. The cutting motor is mounted on the support arm 2 and drives the cutting head 1 to rotate at high speed. During rotation, the cutting head 1 moves up and down along the direction of the rotating shaft.

[0043] The core clamping assembly includes a core clamp 3 and a core clamp 6, which are arranged in a beam-like manner. Both consist of an outer sleeve and a core clamping rubber sleeve fitted inside it. The rubber sleeve is provided with a liquid communication port. The clamping assembly is placed inside the waste liquid collection box 4, located below the rotation path of the support arm 2. A gap is formed between the core clamp 3 and the core clamp 6 to allow the cutting head 1 to pass through.

[0044] The cutting fluid circulation assembly consists of a cutting fluid reservoir 7, a heating plate, a circulation pump, a nozzle, a filter, and a waste fluid collection box 4. The heating plate is located at the bottom of the reservoir 7 and is used to heat the cutting fluid to the same temperature as the formation. The circulation pump delivers the cutting fluid with the same salinity as the formation from the reservoir 7 to the nozzle to lubricate and control the temperature of the cutting head 1. The waste fluid collection box 4 collects the waste fluid after cutting, and after the filter removes rock cuttings, it is returned to the reservoir 7 by the circulation pump, realizing the recycling of the cutting fluid.

[0045] The core pressure control assembly includes a constant pressure pump and a pressure sensor, which are respectively connected to the liquid ports of core holder 3 and core holder 6. Through closed-loop feedback, fluid is continuously injected into the rubber sleeve, and the pressure inside the clamping cavity is maintained at the same level as the original formation pressure, ensuring the stability of the core throughout the cutting process.

[0046] The working principle of this embodiment is as follows: First, the shale core to be cut is inserted between the core holder 3 and the core holder 6. Liquid is injected into the rubber sleeve by a constant pressure pump and monitored and fed back by a pressure sensor to maintain the formation pressure. At the same time, cutting fluid with the same temperature and mineralization as the formation is injected into the cutting fluid storage tank 7. The temperature is controlled by a heating plate and delivered to the nozzle by a circulation pump to continuously rinse and cool the rotating cutting head 1. Then, the cutting assembly is started. The support arm 2 drives the cutting head 1 to move down along the rotation axis. The cutting head 1 cuts the core through the gap between the holders. The waste liquid generated during the cutting process flows into the waste liquid collection box 4 by gravity. After the rock cutting is filtered out by the filter, it flows back to the storage tank 7 to realize the closed-loop circulation of the cutting fluid.

[0047] Example 2

[0048] This embodiment further improves upon Embodiment 1 by adding an integrated linear guide rail and servo drive assembly to the support arm 2, enabling precise vertical positioning and constant-speed descent of the cutting head 1. Additionally, a manual fine-tuning device is added to one side of the support platform 5 base for quick adaptation to cores of different diameters.

[0049] The improved cutting fluid circulation assembly adds an online mineralization and temperature sensor after the filter. The collected parameters are compared with the formation calibration value in real time by the controller, and the heating plate power and fluid replenishment rate are automatically adjusted. At the same time, the circulation pump adopts frequency conversion control to ensure that the cutting fluid flow rate matches the cutting head speed, so as to achieve the best lubrication and cutting effect.

[0050] like Figure 4The working principle of this embodiment is as follows: the core clamping and pressure control process is the same as in Embodiment 1; before cutting, the controller reads the online sensor data, automatically adjusts the temperature and salinity of the cutting fluid, and moves the cutter head 1 to the starting cutting position through the servo drive component; when starting, the cutter head 1 moves down and rotates at a preset constant speed to cut, and the circulating pump and nozzle work in sync to control the flow rate and temperature of the cutting fluid online; during the cutting process, the sensor continuously monitors the liquid parameters, and the controller adjusts the heating plate and replenishes the fluid in a timely manner to ensure the stability of the cutting interface; after cutting, the system automatically recovers the waste liquid and returns it to the storage tank after filtration, realizing efficient reuse of the cutting fluid.

[0051] I. Evidence related to the technical effects obtained by the embodiments of the present invention.

[0052] (1) Core properties are preserved

[0053] like Figure 2 Theoretically, this invention, through a core pressure control component, can precisely regulate the pressure within the core holder, making it comparable to the formation pressure of the shale core. This helps maintain stress balance within the core, preventing changes in pore structure and permeability caused by sudden pressure changes. In experiments, the permeability of the cut shale core was tested, and the variation was controlled within a very small range compared to the original core, effectively ensuring the accuracy of the experimental results.

[0054] (2) Cutting precision and integrity

[0055] The cutting assembly of this invention features an ingenious design where the rotation angle and cutting depth of the support arm can be adjusted in real time. Combined with a cutting head made of ultra-hard composite alloy, it can adapt to the cutting needs of rock cores with different diameters and hardnesses. Theoretically, this design can achieve millimeter-level cutting precision, ensuring the flatness and regularity of the cut surface. The double-clamp structure of the rock core clamping assembly works synergistically with the liquid connection port to dynamically adjust the clamping force, effectively preventing displacement and vibration of the rock core during the cutting process. Experimental results show that the cut rock core has a smooth cross-section, with no obvious debris collapse or microcrack propagation, ensuring good core integrity.

[0056] (3) Cutting fluid recycling

[0057] like Figure 3 The cutting fluid circulation system, through the cooperation of a circulation pump, nozzle, waste fluid collection box, and filter, achieves efficient recycling of the cutting fluid. Theoretically, this closed-loop circulation system can increase the utilization rate of the cutting fluid to over []%, reducing the amount of cutting fluid used and the frequency of replacement, thus lowering experimental costs.

[0058] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A shale core cutting device, comprising a support platform, a cutting assembly, a core clamping assembly, a cutting fluid circulation assembly, and a core pressure control assembly; the cutting assembly includes a cutting head, a cutting motor, and a support arm, the support arm being rotatably mounted on the support platform via a rotating shaft, the cutting motor being mounted on the support arm and connected to the cutting head, the support arm driving the cutting motor and the cutting head to rotate around the rotating shaft to achieve the up-and-down movement of the cutting head; the core clamping assembly is disposed inside a waste fluid collection box and located below the rotation path of the support arm, the clamping assembly including a first core clamp and a second core clamp, the clamp consisting of an outer sleeve and an inner sleeve. The core holder is composed of a core clamping rubber sleeve assembly, with a liquid communication port on the sleeve. The cutting fluid circulation assembly includes a cutting fluid reservoir, a circulation pump, a nozzle, a waste fluid collection box, and a filter. The reservoir is equipped with a heating plate to heat the cutting fluid to the formation temperature and adjust its salinity to match that of the formation water. The circulation pump delivers the cutting fluid to the nozzle to rinse the cutting head. The waste fluid collection box collects waste fluid, and after the filter removes rock cuttings, it is circulated back to the reservoir. The core pressure control assembly includes a constant pressure pump and a pressure sensor. The constant pressure pump and the pressure sensor are connected to the liquid communication port of the core holder for real-time adjustment of the clamping pressure.

2. The shale core cutting device according to claim 1, characterized in that, The support arm's rotation angle and vertical movement speed are adjusted by a servo motor.

3. The shale core cutting device according to claim 1, characterized in that, The filter has a multi-stage screening structure, with the mesh size of each stage decreasing sequentially to trap rock fragments of different sizes.

4. The shale core cutting device according to claim 1, characterized in that, The heating plate maintains a constant cutting fluid temperature through a closed-loop linkage between a temperature sensor and a temperature controller.

5. The shale core cutting device according to claim 1, characterized in that, The constant pressure pump automatically adjusts the output pressure based on feedback from the pressure sensor to maintain a stable clamping force.

6. The shale core cutting device according to claim 1, characterized in that, The core clamping rubber sleeve expands under liquid pressure to generate a concentric clamping force on the core.

7. A method for cutting shale cores, characterized in that, The steps include: loading the rock core into the rock core clamping assembly and setting the initial clamping pressure; heating the cutting fluid to the formation temperature and circulating it to the nozzle to rinse the cutting head; driving the cutting head to rotate around the shaft and perform reciprocating cutting; monitoring and adjusting the clamping pressure and cutting fluid temperature in real time; and collecting and removing the cut rock core.

8. The shale core cutting method according to claim 7, characterized in that, The clamping pressure and cutting fluid temperature are acquired in real time by high-precision pressure and temperature sensors and fed back to the control unit for automatic adjustment.

9. A shale core cutting system, comprising the shale core cutting device of claim 1 and a core separation module, wherein the separation module is located downstream of the waste liquid collection box and is used to automatically separate the cut core and transfer it to subsequent testing equipment.

10. The shale core cutting system according to claim 9, characterized in that, The core separation module is a mechanical pushing structure used to push the core along the axial direction to detach it from the clamping assembly and position it in the sampling tray.

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