Dynamic and static synchronous test method for rock with variable confining pressure and pore pressure
The problem of limited amount of rock in the well was solved by the synchronous dynamic and static testing method of variable confining pressure and pore pressure, and multiple sets of mechanical parameters were obtained simultaneously on the same core sample, which improved the accuracy of the experiment and the utilization rate of the core.
Patent Information
- Application Number
- CN202410313927.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-19
- Publication Date
- 2025-09-19
AI Technical Summary
Existing technologies make it difficult to accurately obtain rock mechanical parameters under different pressure conditions when the amount of rock downhole is limited, and core samples are difficult to preserve and obtain, resulting in the experimental results being unable to fully reflect the true mechanical response of the formation.
A dynamic and static synchronous testing method of rock with variable confining pressure and pore pressure is adopted. The same core sample is tested synchronously under different confining pressure and pore pressure conditions. The stress-strain curve is recorded using a rock mechanics instrument to calculate the rock mechanics parameters.
It is possible to obtain multiple sets of rock mechanical parameters under different pressure conditions under limited core resources, improve the utilization rate of downhole cores, overcome the limitation of core quantity, and ensure the accuracy and comprehensiveness of experimental results.
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Figure CN120668477A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of rock mechanics testing in oilfield development research, and in particular to a method for synchronous dynamic and static testing of rocks with variable confining pressure and pore pressure. Background Art
[0002] Rock mechanics testing plays a crucial role in oil and gas field exploration and development. By studying the physical, mechanical, and seepage properties of rock, we can better understand the characteristics of underground rocks and oilfield reservoirs, providing a scientific basis for oil and gas field exploration, development, and production.
[0003] Today's oil and gas field development faces increasingly complex underground environments, making it difficult to accurately predict the mechanical response of rocks under varying pressures. The rock mechanical parameters directly measured in the laboratory using standard-sized cores under a single pressure condition cannot meet actual requirements, necessitating testing under varying pressures. However, obtaining downhole cores from shale and mudstone is challenging, as they are easily broken during coring and prone to drying and cracking, making them difficult to preserve. Given the difficulty in obtaining large quantities of core samples and the limited availability of experimental cores, obtaining multiple sets of mechanical parameters at multiple pressure points is often challenging. Furthermore, a single set of data often struggles to fully reflect the true mechanical response of the formation. Summary of the Invention
[0004] The present invention provides a method for dynamic and static synchronous testing of rocks under variable confining pressure and pore pressure. The purpose is to use the same core sample to test the dynamic and static synchronous control device and testing method of rock mechanical characteristics under different confining pressure and pore pressure conditions, overcome the limitation of the amount of downhole rock, maximize the utilization of existing core resources, and improve the utilization rate of downhole cores.
[0005] The present invention is achieved through the following technical solution: a method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure, comprising the following steps:
[0006] Step 1: Mount a core sample that meets the experimental standards on a rock mechanics instrument, and raise the temperature in the test chamber of the rock mechanics instrument to a temperature corresponding to the formation depth of the core sample;
[0007] Step 2: increasing the confining pressure in the confining pressure chamber to a first confining pressure value, which is the lowest confining pressure among multiple confining pressure values to be tested; and increasing the pore pressure value to a first pore pressure value, which is the lowest pore pressure among multiple pore pressure values to be tested;
[0008] Step 3: applying axial pressure at a preset loading rate, and recording the stress-strain curve of the core sample using a rock mechanics instrument to obtain rock mechanics characteristics of the core sample under the first confining pressure and the first pore pressure;
[0009] Step 4: sequentially increasing the confining pressure values and the pore pressure values to confining pressure values and pore pressure values other than the first confining pressure value and the first pore pressure value, respectively, in ascending order of the plurality of confining pressure values and the plurality of pore pressure values; applying axial pressure to the core sample at a preset loading rate under the conditions of each confining pressure value and pore pressure value, and obtaining stress-strain curves of the core sample under the conditions of each confining pressure value and pore pressure value;
[0010] Step 5: Calculate the rock mechanical parameters of the core sample according to the stress-strain curve of the core sample under various confining pressure values and pore pressure values.
[0011] Furthermore, in step 2, the pore pressure value is lower than the confining pressure value in each test, and the difference between the pore pressure value and the confining pressure value is 5 MPa.
[0012] Furthermore, in step 4, cyclic loading is completed under all the confining pressure values and the pore pressure values, the confining pressure value and the pore pressure value in the confining pressure chamber are adjusted to values consistent with the original formation, and then axial pressure is loaded at a preset loading rate until the core sample is broken, and the corresponding stress-strain curve is recorded to obtain the compressive strength data under the confining pressure value and pore pressure value conditions.
[0013] Furthermore, the axial pressure is applied by controlling the loading rate using pressure.
[0014] Furthermore, the core sample is unloaded according to a preset pressure relief rate.
[0015] Furthermore, after installing the core sample, the liquid supply system is turned on, and the pore pressure is loaded into the core sample to the first pore pressure value. After completing the axial pressure loading and unloading procedures, the pore pressure value is sequentially increased to multiple pore pressure values other than the first pore pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches the preset target value, the axial pressure loading under the current pore pressure value is stopped and the pressure relief is completed, and the pore pressure value is increased to the next pore pressure.
[0016] Furthermore, after installing the core sample, the oil supply system is opened and hydraulic oil is filled into the confining pressure chamber until the confining pressure value reaches the first confining pressure value. After completing the axial pressure loading and unloading procedures, the confining pressure value is sequentially increased to multiple confining pressure values other than the first confining pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches the preset target value, the axial pressure loading under the current confining pressure value is stopped and the pressure relief is completed, and the confining pressure value in the confining pressure chamber is increased to the next confining pressure value.
[0017] Furthermore, the maximum axial pressure applied is less than the minimum axial pressure causing the rock sample to fracture.
[0018] Furthermore, the plurality of confining pressure values and the plurality of pore pressure values are evenly distributed within the confining pressure value and pore pressure value range that need to be tested.
[0019] Furthermore, the rock mechanics parameters of the core sample obtained include at least one of the three parameters: elastic modulus, Poisson's ratio and compressive strength.
[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0021] The present invention uses a rock mechanics instrument to first apply a low confining pressure and pore pressure to the core sample under preset temperature conditions, then applies axial pressure to obtain the stress-strain curve under the confining pressure and pore pressure conditions. Then, while maintaining a constant temperature, the pore pressure and confining pressure are sequentially varied to obtain the stress-strain curve of the core sample under different pore pressure and confining pressure conditions. This is equivalent to obtaining the rock mechanics parameters of the core sample under different confining pressure and pore pressure conditions under constant temperature. This overcomes the limitation of the amount of downhole rock and the difficulty of existing methods in conducting a large number of repetitive comparative experiments on cores at the same depth and layer. By obtaining rock mechanics characteristics under multiple sets of pressure conditions, the limitation of the amount of downhole rock can be overcome, the utilization of existing core resources can be maximized, and the utilization rate of downhole cores can be improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:
[0023] Figure 1 This is a flow chart of an embodiment of a method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to the present invention;
[0024] Figure 2 Schematic diagram of stress-strain curve of a core sample under certain conditions in an embodiment of a method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to the present invention;
[0025] Figure 3 Schematic diagram of stress and strain of a core sample subjected to cyclic loading under conditions of multiple confining pressure and pore pressure values in an embodiment of a method for synchronous dynamic and static testing of rocks with variable confining pressure and pore pressure according to the present invention;
[0026] Figure 4 The present invention is a flowchart of the specific implementation steps of a method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure. DETAILED DESCRIPTION
[0027] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.
[0028] Example 1
[0029] like Figure 1-Figure 3 As shown, this embodiment 1 provides a method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure, including the following steps:
[0030] Step 1: Mount a core sample that meets the experimental standards on a rock mechanics instrument. In this embodiment, a recommended aspect ratio of the core sample is 2:1. Raise the temperature in the test chamber of the rock mechanics instrument to a temperature corresponding to the formation depth of the core sample.
[0031] Step 2: Raise the confining pressure in the confining pressure chamber to a first confining pressure value, which is the lowest confining pressure among multiple confining pressure values to be tested; and raise the pore pressure value to the first pore pressure value, which is the lowest pore pressure among multiple pore pressure values to be tested, wherein the pore pressure value is always lower than the confining pressure value during each test, and the difference between the pore pressure value and the confining pressure value is 5 MPa;
[0032] Step 3: Applying axial pressure at a preset loading rate. In this embodiment, the core sample is initially subjected to axial pressure at the preset loading rate until it reaches a preset target high axial pressure value. A rock mechanics instrument is used to record the stress-strain curve of the core sample to obtain rock mechanics characteristics of the core sample under a first confining pressure and a first pore pressure.
[0033] Step 4, sequentially increasing the confining pressure values and the pore pressure values to confining pressure values and pore pressure values other than the first confining pressure value and the first pore pressure value, respectively, in descending order of the plurality of confining pressure values and the plurality of pore pressure values, wherein the quantitative relationship between the pore pressure value and the confining pressure value remains unchanged;
[0034] Under various confining pressure and pore pressure conditions, axial pressure is applied to the core sample at a preset loading rate to obtain stress-strain curves of the core sample under various confining pressure and pore pressure conditions, cyclic loading is completed under all confining pressure and pore pressure conditions, the confining pressure and pore pressure values in the confining pressure chamber are adjusted to values consistent with the original formation, and then axial pressure is applied at a preset loading rate until the core sample breaks, the corresponding stress-strain curve is recorded, and compressive strength data under the confining pressure and pore pressure conditions are obtained;
[0035] In this embodiment, an axial pressure is applied to the core sample at a preset rate. In this embodiment, a rock mechanics instrument is used. The rock mechanics instrument is controlled by a computer to apply the axial pressure at the preset loading rate and to unload the axial pressure from the core sample at a preset pressure relief rate. Specifically, in this embodiment, the axial pressure is applied at a pressure-controlled loading rate.
[0036] In this embodiment, after the core sample is installed, the fluid supply system is turned on, and the pore pressure is applied to the inside of the core sample to a first pore pressure value. After the axial pressure loading and unloading procedures are completed, the pore pressure value is sequentially increased to multiple pore pressure values other than the first pore pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches a preset target value, the axial pressure loading at the current pore pressure value is stopped and the pressure is released, and the pore pressure value is increased to the next pore pressure value.
[0037] After the core sample is installed, the oil supply system is turned on and hydraulic oil is filled into the confining pressure chamber until the confining pressure value reaches the first confining pressure value. After the axial pressure loading and unloading procedures are completed, the confining pressure value is sequentially increased to multiple confining pressure values other than the first confining pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches the preset target value, the axial pressure loading under the current confining pressure value is stopped and the pressure is released, and the confining pressure value in the confining pressure chamber is increased to the next confining pressure value.
[0038] In this embodiment, the maximum axial pressure applied is less than the minimum axial pressure that causes the rock sample to fracture, and the multiple confining pressure values and the multiple pore pressure values are evenly distributed within the confining pressure value and pore pressure value range required for testing;
[0039] Step 5: Calculate the rock mechanical parameters of the core sample based on the stress-strain curve of the core sample under various confining pressure and pore pressure conditions.
[0040] Depend on Figure 1 As can be seen from the process shown, in an embodiment of the present invention, by fixing a single core sample on a rock mechanics instrument and applying a temperature corresponding to the original formation to the single core sample, the confining pressure is first increased to the minimum confining pressure value required for the test (the measurement method of the rock mechanics parameters of the formation can meet the measurement under high confining pressure conditions, for example, rock mechanics parameter measurement below 200 MPa), axial pressure is applied to the core sample under the minimum confining pressure value and pore pressure value, and a stress-strain curve diagram under the conditions of the minimum confining pressure value and pore pressure value is obtained. By unloading the axial pressure and adjusting the confining pressure, axial pressure is applied to the single core sample under various confining pressure values and pore pressure values to obtain stress-strain curve diagrams under various confining pressure and pore pressure conditions, and then the mechanical parameters of the core sample can be calculated based on the stress-strain curve diagram.
[0041] Under the condition that core samples are difficult to obtain in large quantities and only a small number of cores are available for testing, by cyclically loading a single core sample with different confining pressure values and pore pressure values, multiple sets of mechanical parameters of the core sample under multiple confining pressure and pore pressure conditions can be obtained for a single core sample, thereby avoiding the influence of heterogeneity of the core mechanical properties to the greatest extent and maximizing the utilization of existing core resources.
[0042] During specific implementation, in order to obtain stress-strain curves at various confining pressure values and pore pressure values while ensuring the accuracy of the stress-strain curves without damaging the core sample, in this embodiment, the confining pressure and pore pressure are loaded sequentially to the other confining pressures and pore pressures among the multiple confining pressure values and pore pressure values except the first confining pressure value and pore pressure value by cyclically loading the confining pressure and pore pressure values from low to high, until the loaded confining pressure and pore pressure values are loaded to the preset maximum confining pressure value and pore pressure value.
[0043] Then, axial stress loading is started until the axial pressure reaches a preset maximum axial pressure, and axial pressure loading on the core sample under the current confining pressure and pore pressure conditions is stopped. The axial pressure is unloaded at a certain rate to a preset value, and the confining pressure and pore pressure are increased to the next confining pressure and pore pressure values.
[0044] The maximum axial pressure should be slightly less than the axial pressure that causes the rock sample to break. Specifically, in order to ensure that the core sample is not damaged, the test method can be to use parallel samples to test the axial pressure that causes the rock sample to break; or it can be through the initial loading, observing the shape of the stress-strain curve, and when the slope of the stress-strain curve stabilizes for a period of time, stopping the axial stress loading and intercepting the integer axial pressure as the preset maximum axial pressure.
[0045] The maximum confining pressure value is generally determined by the model of the rock mechanics instrument used. For example, the maximum confining pressure value in this example is 200MPa, and the corresponding maximum pore pressure value in this example is 195MPa. Similarly, through preloading, it can be determined that the maximum axial pressure in this example is 150MPa. Furthermore, after each confining pressure and pore pressure value are loaded, the axial pressure is loaded to 150MPa. After stabilization for 10 seconds, the axial pressure is unloaded until the axial pressure is unloaded to 10MPa, and the axial pressure loading is stopped. During this process, the rock mechanics instrument automatically records the stress-strain curve of the core sample.
[0046] In actual operation, after confirming that the core sample is not broken, the confining pressure and pore pressure in the high-pressure chamber are reduced to the next confining pressure value and pore pressure value, and the core sample is continuously loaded with axial pressure at the next confining pressure value and pore pressure value to obtain the stress-strain curve diagram at the next confining pressure value and pore pressure value, and then the stress-strain curves at the above multiple confining pressure values and pore pressure values are obtained, for example, Figure 2 .
[0047] In a specific implementation, during the axial compression of the core sample, in order to obtain accurate stress-strain curve data while ensuring that the core sample is not damaged, in this embodiment, the core sample is subjected to axial compression at a preset loading rate, including: using an axial pressure control system to apply axial compression to the core sample at a preset loading rate. Specifically, the preset loading rate may be 0.2 MPa / s.
[0048] Furthermore, to prevent damage to the core sample due to excessive stress release, the core sample is unloaded from the axial pressure at a preset pressure relief rate. Specifically, the preset pressure relief loading rate is 0.3 MPa / s.
[0049] In specific implementation, in order to improve the accuracy of the measured stress-strain curve data, in this embodiment, multiple confining pressure values and pore pressure values are evenly distributed within the confining pressure value and pore pressure value range to be tested. That is, when conducting a measurement test, the confining pressure value and pore pressure value range to be tested can be evenly divided into multiple confining pressure and pore pressure segments, and the end point confining pressure and pore pressure of each confining pressure and pore pressure segment are determined as the multiple confining pressure values and pore pressure segment values to be tested. For example, if the confining pressure and pore pressure range to be tested is 10MPa to 200MPa, it can be evenly divided into multiple pressure segments of 10MPa-20MPa, 20MPa-30MPa, 30MPa-40MPa, 40MPa-50MPa...190MPa-200MPa, that is, multiple pressure values of 10MPa, 20MPa, 30MPa, 40MPa, 50MPa...200MPa are determined as the confining pressure and pore pressure values to be tested.
[0050] The difference between Example 2 and Example 1 is that: Figure 2 and Figure 4 As shown, this embodiment discloses a specific method for obtaining rock mechanical parameters of a core sample. The obtained rock mechanical parameters of the core sample include at least one of the three parameters: elastic modulus, Poisson's ratio, and compressive strength.
[0051] After obtaining the stress-strain curve at each temperature value, various mechanical parameters can be calculated based on the stress-strain curve according to the existing definition method. For example, the slope of the stress-strain curve is the elastic modulus.
[0052] The following describes in detail the method for measuring formation rock mechanical parameters with specific examples. Taking shale core as an example, the core sample mainly measures the rock mechanical parameters under 9 confining pressure values of 10MPa, 20MPa, 30MPa, 40MPa, 50MPa, 60MPa, 70MPa, 80MPa, and 90MPa (the corresponding pore pressure values are 5MPa, 15MPa, 25MPa, 35MPa, 45MPa, 55MPa, 65MPa, 75MPa, and 85MPa). The experimental process mainly includes the installation, heating, loading, and unloading records of the core specimens. During the experiment, the loading and unloading rates of each core remain unchanged. Specifically, the specific method for obtaining the rock mechanical parameters of the core sample includes the following steps:
[0053] Step 401: Using an existing triaxial rock mechanics instrument, a standard core sample is mounted and fixed, a strain gauge is clamped, and the temperature is raised to a temperature value corresponding to the depth of the formation where the core sample is located;
[0054] Step 402: Raise the confining pressure in the confining pressure chamber to 10 MPa, continue to load the pore pressure to 5 MPa, and apply axial pressure to the core sample using the axial pressure control system, controlling the pressure loading rate to 0.2 MPa / s;
[0055] Step 403: During the process of applying axial pressure to the core sample using the axial pressure control system, observe the volume strain curve in the stress-strain curve diagram, record the stress and deformation data and related curve diagrams during the loading process, and measure and calculate the slope change of the volume strain curve in real time to determine whether the core sample is broken. When the axial pressure reaches 150 MPa, stop applying axial pressure to the core sample, and record the stress and deformation data and related curve diagrams during the process of applying axial pressure to the core sample under the conditions of 10 MPa confining pressure and 5 MPa pore pressure. Figure 2 As shown in the figure, the obtained test curves were processed to obtain rock mechanical parameters such as elastic modulus and Poisson's ratio under the conditions of 10 MPa confining pressure and 5 MPa pore pressure. For example, the slope of the volume stress-strain curve segment is the elastic modulus.
[0056] Step 404: Apply the axial pressure control system to unload the axial pressure from 150 MPa to 10 MPa, controlling the axial pressure unloading rate to 0.3 MPa / s. Increase the confining pressure in the confining pressure chamber to 20 MPa and the pore pressure to 15 MPa. Apply the axial pressure control system to load the core sample with the axial pressure, controlling the pressure loading rate to 0.2 MPa / s.
[0057] Step 405: During the process of applying axial pressure to the core sample using the axial pressure control system, observe the volume strain curve in the stress-strain curve diagram, record the stress and deformation data and related curve diagrams during the loading process, and measure and calculate the slope change of the volume strain curve in real time to determine whether the core sample is broken. When the axial pressure reaches 150 MPa, stop applying axial pressure to the core sample, and record the stress and deformation data and related curve diagrams during the process of applying axial pressure to the core sample under the conditions of 20 MPa confining pressure and 15 MPa pore pressure. Figure 2 As shown in the figure, the obtained test curves were processed to obtain rock mechanical parameters such as elastic modulus and Poisson's ratio under the conditions of 20 MPa confining pressure and 15 MPa pore pressure. For example, the slope of the volume stress-strain curve segment is the elastic modulus.
[0058] Step 406: Apply the axial pressure control system to unload the axial pressure from 150 MPa to 10 MPa, controlling the axial pressure unloading rate to 0.3 MPa / s. Increase the confining pressure in the confining pressure chamber to 30 MPa and the pore pressure to 25 MPa. Apply the axial pressure control system to apply axial pressure to the core sample, controlling the pressure loading rate to 0.2 MPa / s. This allows the stress-strain curves to be obtained under the conditions of 30 MPa confining pressure and 25 MPa pore pressure, and the relevant rock mechanical parameters to be calculated. Repeat steps 403 to 405 as needed to obtain experimental data under other temperature conditions, such as 40 MPa, 50 MPa, and 200 MPa.
[0059] Step 407: Finally, the confining pressure and pore pressure are adjusted to the specified values, and the axial pressure control system is used to load the core sample with axial pressure. The pressure loading rate is controlled to 0.2 MPa / s until the core sample fracture experiment is completed. The volume strain curve in the stress-strain curve diagram is observed, and the stress and deformation data and related curves during the loading process are recorded to obtain rock mechanical parameters such as elastic modulus, Poisson's ratio, and compressive strength under these conditions.
[0060] In an embodiment of the present invention, a single core sample is fixed in a triaxial rock mechanics instrument, the temperature is first raised to a temperature value corresponding to the original formation, and then a certain confining pressure and pore pressure value are applied to the core sample. Under the conditions of the lowest confining pressure and pore pressure value, axial pressure is applied to the core sample to obtain a stress-strain curve diagram under the lowest confining pressure and pore pressure value. After the single axial pressure loading is completed, the axial pressure is released, and the confining pressure and pore pressure are adjusted in sequence to the various confining pressure and pore pressure value conditions required for testing. Under each confining pressure and pore pressure value, axial pressure is applied to the core sample to obtain a stress-strain curve diagram under each confining pressure and pore pressure value, and then the mechanical parameters of the core sample can be calculated based on the stress-strain curve diagram. Under the condition that core samples are difficult to obtain in large quantities and only a small number of cores are available for testing, by gradually increasing the confining pressure and pore pressure on a single core sample, multiple sets of mechanical parameters of the core sample at multiple confining pressure and pore pressure values can be obtained, while maximizing the utilization of existing core resources.
[0061] Obviously, those skilled in the art should understand that the various modules or steps of the above-mentioned embodiments of the present invention can be implemented using a general-purpose computing device, they can be concentrated on a single computing device, or distributed across a network composed of multiple computing devices. Alternatively, they can be implemented using program code executable by the computing device, so that they can be stored in a storage device and executed by the computing device. In some cases, the steps shown or described can be performed in a different order than herein, or they can be made into separate integrated circuit modules, or multiple modules or steps can be made into a single integrated circuit module for implementation. Thus, the embodiments of the present invention are not limited to any specific combination of hardware and software.
[0062] It should be noted that the above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present application. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.
[0063] In the description of the present invention, it should be noted that the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.
[0064] In the description of this document, the terms "up", "down", "left", "right", "front", "back", "top", "bottom", "inside", "outside", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only used to illustrate the relative position relationship between the various components or components, and do not particularly limit the specific installation orientation of the various components or components.
[0065] In the descriptions of this document, some terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.
[0066] In this document, the terms "installed," "disposed," "provided with," "connected," and "connected" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections, indirect connections through an intermediary, or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.
[0067] The structures, proportions, sizes, etc. drawn in the drawings in this application are only used to match the contents disclosed in this technical briefing document for those skilled in the art to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the efficacy and purpose that can be achieved by this application.
[0068] The terms used in this document are those commonly used in the art currently in consideration of the functions of the present disclosure, but these terms may vary according to the intentions of those skilled in the art, precedents, or new technologies in the art. In addition, specific terms may be selected by the applicant, and in such cases, their detailed meanings will be described in the detailed description of the present disclosure. Therefore, the terms used in the document should not be understood as simple names, but rather as a general description based on the meaning of the terms and the present disclosure.
[0069] Flowcharts or text are used in this document to illustrate the operational steps performed according to the embodiments of the present application. It should be understood that the operational steps in the embodiments of the present application are not necessarily performed in the exact order in which they are described. Instead, the various steps may be processed in reverse order or simultaneously, as needed. Furthermore, other operations may be added to these processes, or one or more operations may be removed from these processes.
[0070] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.
Claims
1. A method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure, characterized in that: The following steps are involved: Step 1: Mount a core sample that meets the experimental standards on a rock mechanics instrument, and raise the temperature in the test chamber of the rock mechanics instrument to a temperature corresponding to the formation depth of the core sample; Step 2: increasing the confining pressure in the confining pressure chamber to a first confining pressure value, which is the lowest confining pressure among multiple confining pressure values to be tested; and increasing the pore pressure value to a first pore pressure value, which is the lowest pore pressure among multiple pore pressure values to be tested; Step 3: applying axial pressure at a preset loading rate, and recording the stress-strain curve of the core sample using a rock mechanics instrument to obtain rock mechanics characteristics of the core sample under the first confining pressure and the first pore pressure; Step 4: sequentially increasing the confining pressure values and the pore pressure values to confining pressure values and pore pressure values other than the first confining pressure value and the first pore pressure value, respectively, in ascending order of the plurality of confining pressure values and the plurality of pore pressure values; applying axial pressure to the core sample at a preset loading rate under the conditions of each confining pressure value and pore pressure value, and obtaining stress-strain curves of the core sample under the conditions of each confining pressure value and pore pressure value; Step 5: Calculate the rock mechanical parameters of the core sample according to the stress-strain curve of the core sample under various confining pressure values and pore pressure values.
2. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 1, characterized in that: In step 2, the pore pressure value is lower than the confining pressure value in each test, and the difference between the pore pressure value and the confining pressure value is 5 MPa.
3. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 1 is characterized in that: In step 4, cyclic loading is completed under all the confining pressure values and the pore pressure values, the confining pressure value and the pore pressure value in the confining pressure chamber are adjusted to values consistent with the original formation, and then axial pressure is loaded at a preset loading rate until the core sample is broken, and the corresponding stress-strain curve is recorded to obtain the compressive strength data under the confining pressure value and pore pressure value conditions.
4. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 3 is characterized in that: The axial pressure is applied using a pressure-controlled loading rate.
5. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 4 is characterized in that: The core sample is unloaded from the axial pressure according to a preset pressure relief rate.
6. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 5, characterized in that: After the core sample is installed, the fluid supply system is turned on, and the pore pressure is loaded into the core sample to the first pore pressure value. After the axial pressure loading and unloading procedures are completed, the pore pressure value is sequentially increased to multiple pore pressure values other than the first pore pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches the preset target value, the axial pressure loading under the current pore pressure value is stopped and the pressure relief is completed, and the pore pressure value is increased to the next pore pressure value.
7. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 5, characterized in that: After the core sample is installed, the oil supply system is opened and hydraulic oil is filled into the confining pressure chamber until the confining pressure value reaches the first confining pressure value. After the axial pressure loading and unloading procedures are completed, the confining pressure value is sequentially increased to multiple confining pressure values other than the first confining pressure value, and the axial pressure is recorded in real time. When the axial pressure reaches a preset target value, the axial pressure loading under the current confining pressure value is stopped and the pressure relief is completed, and the confining pressure value in the confining pressure chamber is increased to the next confining pressure value.
8. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 3 is characterized in that: The maximum axial pressure of the load is less than the minimum axial pressure that causes the rock sample to break.
9. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 1, characterized in that: The multiple confining pressure values and the multiple pore pressure values are evenly distributed within the confining pressure value and pore pressure value range that need to be tested.
10. The method for synchronous dynamic and static testing of rock with variable confining pressure and pore pressure according to claim 1, characterized in that: The rock mechanics parameters of the core sample obtained include at least one of the three parameters: elastic modulus, Poisson's ratio and compressive strength.