A method for preparing test samples of a fractured rock

Abstract

This application provides a method for preparing test samples of fractured rock, relating to the field of petroleum geological exploration technology. The method includes: preparing a predetermined number of test samples based on different water-cement-sand-gravel ratios, and identifying target test samples; scanning the fracture profiles of the fractured rock and printing fracture surface molds for each fracture profile; printing cement casting molds corresponding to the fractured rock according to its external dimensions and the distribution of fracture profiles within it; placing the fracture surface molds into the cement casting molds and positioning plates into corresponding groove groups to limit the position of the fracture surface molds; and pouring target cement, prepared according to the water-cement-sand-gravel ratio corresponding to the target test sample, into the positioned cement casting mold to obtain the test sample corresponding to the fractured rock. This application uses this method to produce test samples that more closely approximate the mechanical properties and fracture structure of fractured rock.

Description

Technical Field

[0001] This application relates to the field of petroleum geological exploration technology, and more specifically, to a method for preparing test samples of fractured rock. Background Technology

[0002] With the expansion of drilling projects in deep and ultra-deep oil and gas reservoirs, wellbore collapse and lost circulation caused by fractured formations have become more prominent, posing a serious obstacle to the efficient and economical exploration and development of deep and ultra-deep oil and gas. To reveal the mechanical properties of deep and ultra-deep fractured rocks, the mechanism of wellbore collapse, and the main influencing factors, it is of great research significance and engineering application value to collect and prepare rock samples that can accurately and effectively represent layered fractured formations and conduct experimental research on the mechanical properties and fracture failure of layered fractured rocks.

[0003] In existing technologies, rock mechanics test samples are typically prepared by pre-positioning smooth steel sheets at specific locations in a mold and then pouring cement. These samples are then used for rock mechanics experiments to obtain rock mechanics performance parameters. However, this method produces rock mechanics test samples with straight cracks, which cannot accurately represent the crack density of fractured strata and results in a significant discrepancy between the samples and the actual mechanical properties of fractured rocks. Summary of the Invention

[0004] This application provides a method for preparing test samples of fractured rock, aiming to produce test samples that more closely resemble the mechanical properties and fracture structure of fractured rock.

[0005] The first aspect of this application provides a method for preparing test samples of fractured rock, the method comprising: A predetermined number of test samples were prepared based on different configuration ratios of water, lime, sand, and gravel. Based on the mechanical properties of each test sample and the fractured rock, the target test sample is determined; Scan the fracture profile of the fractured rock and print the fracture surface mold of each fracture profile. Based on the external dimensions of the fractured rock and the distribution of crack profiles in the fractured rock, a cement casting mold corresponding to the fractured rock is printed. The cement casting mold includes a groove group for fixing a limiting plate, which is used to limit the mold on the crack surface. The crack surface mold is placed into the cement casting mold, and the limiting plate is placed into the corresponding groove group to limit the crack surface mold; The target cement, prepared according to the water-cement-sand-gravel ratio corresponding to the target test sample, is poured into the cement casting mold after being limited, and the test sample corresponding to the fractured rock is obtained.

[0006] Optionally, target test samples are determined based on the mechanical properties of each test sample and the fractured rock, including: Mechanical experiments were conducted on fractured rocks to obtain their mechanical properties. Mechanical experiments were conducted on each test sample to obtain the mechanical properties of each test sample. The mechanical properties of the fractured rock were compared with those of each test sample to obtain the comparison results for each test sample. The target test sample is determined based on the comparison results of each test sample.

[0007] Optionally, the target test sample is determined based on the comparison results corresponding to each test sample, including: Based on the comparison results of each test sample, all test samples are sorted to obtain the sorting results. The comparison results are the similarity between the mechanical properties of each test sample and the mechanical properties of the fractured rock. The test sample ranked first in the sorting results is determined as the target test sample.

[0008] Optionally, the method further includes: Based on the water-cement-sand-gravel configuration ratio and mechanical performance of each test sample, the linear relationship between mechanical performance and the water-cement ratio and sand-cement ratio in the water-cement-sand-gravel configuration ratio is determined. Based on the linear relationship and the mechanical properties of the fractured rock, the water-cement sand-gravel configuration ratio of the target test sample is determined. The mechanical properties include compressive strength and elastic modulus; When the mechanical property is expressed as compressive strength, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows:

[0009] in, This refers to compressive strength; This refers to the sand-to-ash ratio; This refers to the water-cement ratio; When the mechanical property is expressed as elastic modulus, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows:

[0010] Here, E refers to the elastic modulus.

[0011] Optionally, based on the external dimensions and the distribution of crack profiles within the fractured rock, a cement casting mold corresponding to the fractured rock is printed, including: Based on the shape and dimensions of the fractured rock, the first cement casting model was determined; Based on the scanned crack profile, a plane tangent to the convex surface of the crack profile is determined; Based on the distribution of the plane and the scanned crack profile in the fractured rock, the position of the groove group corresponding to the crack profile in the first cement casting model is determined. The cement casting model is determined based on the position of the first cement casting model and the groove group corresponding to each crack profile in the first cement casting model. The cement casting model is printed to obtain a cement casting mold.

[0012] Optionally, determining the position of the groove group corresponding to the crack profile in the first cement casting model based on the distribution of the plane and the scanned crack profile in the fractured rock includes: The plane tangent to the convex surface of the crack profile is extended to obtain two line segments that intersect the extended plane with the two sides of the first cement casting model. Based on two intersecting line segments, the position of the groove group corresponding to the crack profile in the first cement casting model is determined.

[0013] Optionally, the crack surface mold is placed into the cement casting mold, and a limiting plate is placed into the corresponding groove group to limit the crack surface mold, including: Apply lubricating oil to the inner wall and cracked surface of the cement casting mold; The first section in the cement casting mold that has not been filled with cement along the casting direction is defined as the section to be cast. The casting section is divided by the groove group corresponding to the crack profile. Place the limiting plate corresponding to the layer to be poured into the groove group of the layer to be poured; The crack surface mold corresponding to the layer to be poured is placed into the layer with its convex surface tightly against the limiting plate.

[0014] Optionally, the target cement, prepared according to the water-cement-sand-gravel configuration ratio corresponding to the target test sample, is poured into a cement casting mold after being limited to a certain position to obtain a test sample corresponding to the fractured rock, including: Based on the water-cement-sand-gravel configuration ratio corresponding to the target test sample, the target cement is prepared to obtain the target cement. The target cement is poured into the cement casting mold into the layer to be cast, thereby obtaining the casting layer; When the target cement in the pouring section is in a state between the initial setting time and the final setting time, remove the mold and limiting plate corresponding to the crack surface of the pouring section. Along the cement pouring direction, the target cement is poured into the new pouring section in the cement pouring mold to obtain a new pouring section. When the target cement in the new pouring section is in a state between the initial setting time and the final setting time, the crack surface mold and the limiting plate corresponding to the new pouring section are removed. This process continues until all sections in the cement pouring mold are poured, at which point a test sample corresponding to the fractured rock is obtained.

[0015] Optionally, the method further includes: The test sample corresponding to the obtained fractured rock is cured for a preset time to obtain the first test sample; The first test sample is polished based on a preset size to obtain a target test sample of the preset size.

[0016] Optionally, the dimensions of the test sample are: length 50mm, width 50mm, and height 100mm. Beneficial effects: This application provides a method for preparing test samples of fractured rock. The method includes: preparing a preset number of test samples based on different water-cement-sand-gravel ratios; determining a target test sample based on the mechanical properties of each test sample and the fractured rock; scanning the crack profile of the fractured rock and printing crack surface molds for each crack profile; printing a cement casting mold corresponding to the fractured rock based on the external dimensions of the fractured rock and the distribution of crack profiles in the fractured rock, wherein the cement casting mold includes a groove group for fixing a limiting plate, the limiting plate being used to limit the crack surface mold; placing the crack surface mold into the cement casting mold and placing the limiting plate into the corresponding groove group to limit the crack surface mold; pouring target cement prepared according to the water-cement-sand-gravel ratio corresponding to the target test sample into the cement casting mold after limiting, thereby obtaining the test sample corresponding to the fractured rock.

[0017] By configuring several test samples with different water-cement-sand-aggregate ratios, a target test sample that more closely resembles the mechanical properties of fractured rock was selected. Then, by scanning the fractured rock, a crack surface mold and a cement casting mold were printed. The crack surface mold and a limiting plate were placed inside the cement casting mold, and target cement made with the water-cement-sand-aggregate ratio corresponding to the target test sample was poured into the cement casting mold, finally obtaining the test sample. Simulating cracks using the crack surface mold to create test samples more closely resembles the crack shape of real fractured rock. Simultaneously, by testing the mechanical properties of multiple test samples, a better water-cement-sand-aggregate ratio corresponding to the target test sample was selected. The test sample made with this water-cement-sand-aggregate ratio exhibits mechanical properties that more closely resemble those of real fractured rock. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a method for preparing test samples of fractured rock according to an embodiment of this application; Figure 2 This is a schematic diagram of a test sample provided in one embodiment of this application; Figure 3 This is a schematic diagram of a crack surface mold provided in one embodiment of this application; Figure 4 This is a schematic diagram of a cement casting mold provided in one embodiment of this application; Figure 5 This is a schematic diagram of a layer-by-layer casting method provided in an embodiment of this application; Figure 6 This is a schematic diagram of a test sample provided in one embodiment of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] This application provides an excitation timing control method and a method for preparing test samples of fractured rock, such as... Figure 1The flowchart illustrates a method for preparing test samples of fractured rock. Specifically, the method for preparing test samples of fractured rock provided in this application includes: S11: Prepare a preset number of test samples based on different configuration ratios of water-cement sand and gravel.

[0022] In oil and gas drilling projects, fractured formations are a common geological condition. To better help engineers understand the degree of formation fracture and mechanical properties, this application uses real fractured rock as a basis to create a test sample that closely resembles real fractured rock. This allows staff to develop reasonable drilling plans based on the test sample, thereby reducing the occurrence of problems such as wellbore instability.

[0023] Specifically, based on the geological conditions of the fractured rock, a predetermined quantity of suitable water-cement sand and gravel mixtures is selected. This mixture includes cement, sand, and water; the water-cement sand and gravel mixture ratio refers to the proportion of cement, sand, and water. Based on these different mixture ratios, different water-cement sand and gravel slurries are prepared. These slurries are then poured into rectangular molds to obtain a predetermined quantity of rectangular test samples, such as... Figure 2 The diagram shows a test sample.

[0024] In addition, the preferred water-cement sand and gravel mixing ratio can be cement:sand:water = 2.5:1.5:1, cement:sand:water = 2.5:2:1, cement:sand:water = 2.5:2.5:1; the types of cement include but are not limited to silicate 42.5 cement, sulfoaluminate 62.5 cement, and aluminate 72.5 cement; the types of sand include but are not limited to quartz sand and river sand.

[0025] S12: Determine the target test sample based on the mechanical properties of each test sample and the fractured rock.

[0026] Specifically, the obtained test samples undergo mechanical experiments to obtain their mechanical properties, such as elasticity and compressive strength. Simultaneously, fractured rock is also subjected to the same mechanical experiments to obtain its mechanical properties. The mechanical properties of all test samples are compared with those of the fractured rock to determine the test sample whose mechanical properties are closest to those of the fractured rock, and this sample is then designated as the target test sample.

[0027] S13: Scan the fracture profile of the fractured rock and print the fracture surface mold of each fracture profile.

[0028] To better simulate the direction of cracks in fractured rock, this embodiment chooses to construct the morphology of cracks in fractured rock through 3D scanning and printing. Specifically, 3D printing technology can be used to scan the cross-section of fractured rock, and the scanned cross-section containing cracks can be identified as crack profiles. Then, multiple scanned crack profiles are printed to obtain crack surface molds corresponding to each crack profile. Figure 3 The diagram shows a mold for a fractured surface. If the fractured rock drilled from the fractured rock layer is in a broken or fragmented state, it is adhered together before scanning. Furthermore, the materials used for printing include, but are not limited to, nylon, rigid photosensitive resin, and ABS-like photosensitive resin.

[0029] S14: Based on the external dimensions of the fractured rock and the distribution of the crack profile in the fractured rock, print the cement casting mold corresponding to the fractured rock. The cement casting mold includes a groove group for fixing a limiting plate, and the limiting plate is used to limit the mold of the crack surface.

[0030] To better simulate the actual structure of fractured rock, this application also fabricated a cement casting mold with the same external dimensions as the fractured rock, serving as an outer shell to constrain the shape of the test sample. Specifically, the external dimensions of the fractured rock were scanned using 3D scanning technology, and a cement casting mold with the same external dimensions as the fractured rock was printed. Since this cement casting mold is used for casting and shaping the test sample, it is a rectangular shell with no top or bottom cover, and its internal dimensions are equal to the external dimensions of the fractured rock. Figure 4 The diagram shows a cement casting mold.

[0031] Furthermore, the crack surface mold is placed in the cement casting mold, and then the target cement is poured into the cement casting mold. After the target cement solidifies, the crack surface mold and the cement casting mold are removed to obtain the final test sample. The gap left in the test sample after removing the crack surface mold is the simulated crack. However, considering that the crack surface mold may shift under the pouring of the target cement, causing changes in the position and shape of the crack, in order to avoid this, that is, to accurately simulate the cracks of fractured rock using the crack surface mold, this application sets multiple groove groups in the cement casting mold according to the distribution of crack profiles in fractured rock. The groove group is used to place a limiting plate, which is mainly used to restrict the position of the crack surface mold and prevent the crack surface mold from being moved by the impact of the target cement when the target cement is poured into the cement casting mold, causing the simulated crack to differ from the real crack.

[0032] S15: Place the crack surface mold into the cement casting mold, and place the limiting plate into the corresponding groove group to limit the crack surface mold.

[0033] Since the groove assembly is used to place the limiting plate, and the limiting plate is used to limit the position of the crack surface mold, and since each crack surface mold is constructed based on a real crack, each crack surface mold is different. Therefore, in order to achieve precise positioning of different crack surface molds, different limiting plates are set for different crack surface molds, and the groove assemblies used to place different limiting plates are also different. Therefore, when the crack surface mold is placed in the cement casting mold to simulate a crack, the corresponding limiting plate of the crack surface mold is placed in the corresponding groove assembly so that the limiting plate can limit the position of the corresponding crack surface mold.

[0034] S16: The target cement, prepared according to the water-cement-sand-gravel configuration ratio corresponding to the target test sample, is poured into the cement casting mold after the limit is set to obtain the test sample corresponding to the fractured rock.

[0035] Since the target test sample has been obtained through the above S12 step, and the mechanical performance of the target test sample is closer to the mechanical performance of real fractured rock, the test sample made by the water-cement sand-gravel configuration ratio corresponding to the target test sample is also closer to fractured rock.

[0036] Specifically, a target cement is prepared according to the water-cement-sand-gravel mixture ratio corresponding to the target test sample. This target cement is then poured into a cement casting mold so that, after solidification, it forms a test sample with mechanical properties similar to fractured rock. After obtaining the target cement, it is poured into a cement casting mold with a limiting plate and a crack surface mold already in place. After the target cement solidifies, it is demolded to obtain the test sample corresponding to the fractured rock. The voids left in the test sample after removing the crack surface mold represent the simulated cracks in the fractured rock.

[0037] The test samples obtained by this method are not only more similar to fractured rocks in terms of mechanical properties, but also have the same crack morphology and orientation. Therefore, the data obtained from subsequent fluid experiments using these test samples are the same as those obtained from real fractured rock formations, which is more conducive to engineers in formulating reasonable drilling plans.

[0038] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S12 includes steps S21 to S24: S21: Conduct mechanical experiments on the fractured rock to obtain the mechanical properties of the fractured rock.

[0039] S22: Conduct mechanical experiments on each test sample to obtain the mechanical performance of each test sample.

[0040] S23: Compare the mechanical properties of the fractured rock with the mechanical properties of each test sample to obtain the comparison results for each test sample.

[0041] S24: Determine the target test sample based on the comparison results of each test sample.

[0042] To select test samples that better reflect the mechanical properties of fractured rock, this embodiment conducted mechanical experiments on all test samples and fractured rock. Specifically, mechanical experiments were performed on the fractured rock, such as placing it on appropriate experimental instruments like testing machines, presses, and strain gauges, and then conducting uniaxial compression tests to obtain the rock's elastic modulus, Poisson's ratio, and mechanical strength. These mechanical properties, expressed as numerical parameters, better reflect the mechanical behavior of fractured rock. Simultaneously with the mechanical experiments on the fractured rock, a predetermined number of test samples were also subjected to mechanical experiments to obtain the corresponding mechanical properties of each test sample.

[0043] The mechanical properties of the fractured rock were compared with those of each test sample to obtain the comparison results for each test sample. These results demonstrate the similarity between the mechanical properties of the test sample and the fractured rock. Since mechanical properties can be represented by numerical parameters, the similarity between the mechanical properties of the test sample and the fractured rock can also be expressed numerically. Based on the comparison results for each test sample, i.e., the similarity between the mechanical properties of each test sample and the fractured rock, the test sample with the most similar mechanical properties to the fractured rock was selected and designated as the target test sample.

[0044] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S24 includes steps S31 to S32: S31: Based on the comparison results corresponding to each test sample, sort all the test samples to obtain the sorting results, wherein the comparison results are the similarity between the mechanical properties of each test sample and the mechanical properties of the fractured rock.

[0045] S32: The test sample ranked first in the sorting results is determined as the target test sample.

[0046] Specifically, since mechanical properties can be represented by parameter values, such as the elastic modulus of the test sample being 23 GPa and Poisson's ratio being 0.15, while the elastic modulus of fractured rock is 25 GPa and Poisson's ratio is 0.14, comparing the mechanical properties of the test sample with those of the fractured rock involves comparing the elastic modulus of the test sample with that of the fractured rock, and comparing the Poisson's ratio of the test sample with that of the fractured rock. The corresponding comparison result is the similarity between the mechanical properties of the test sample and those of the fractured rock. This similarity can be determined by subtracting the values ​​of various parameters of the test sample from the corresponding values ​​of the same type of parameters of the fractured rock, multiplying each difference by its corresponding weight, and then averaging the results. This average value reflects the degree of difference between the mechanical properties of the test sample and those of the fractured rock; therefore, the smaller the average value, the greater the similarity between the mechanical properties of the test sample and those of the fractured rock.

[0047] Based on the comparison results of all the test samples, all the test samples are sorted. Specifically, the sorting method is based on the similarity of the comparison results among the test samples, placing the test samples with the highest similarity at the top. That is, the test sample with the lowest average value is placed at the front of the sort. The test sample ranked first in the sorted results is selected because its mechanical properties are most similar to those of fractured rock among all the test samples; therefore, this test sample is determined as the target test sample.

[0048] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, the method further includes steps S41 to S45: S41: Based on the water-cement sand and gravel configuration ratio and mechanical performance of each test sample, determine the linear relationship between the mechanical performance and the water-cement ratio and sand-cement ratio in the water-cement sand and gravel configuration ratio. S42: Based on the linear relationship and the mechanical properties of the fractured rock, determine the water-cement sand-gravel configuration ratio of the target test sample; S43: The mechanical properties include compressive strength and elastic modulus; S44: When the mechanical property is expressed as compressive strength, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows:

[0049] in, This refers to compressive strength; This refers to the sand-to-ash ratio; This refers to the water-cement ratio; S45: When the mechanical property is expressed as elastic modulus, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows:

[0050] Here, E refers to the elastic modulus.

[0051] Specifically, in this embodiment, the water-cement-sand-gravel configuration includes the water-cement ratio and the sand-cement ratio. By acquiring the mechanical properties of multiple test samples and fitting these properties to the corresponding water-cement ratio and sand-cement ratio in the water-cement-sand-gravel configuration, a linear relationship is obtained between the mechanical properties and the water-cement ratio and sand-cement ratio. Given the known mechanical properties, the water-cement ratio and sand-cement ratio in the water-cement-sand-gravel configuration can be determined through this linear relationship. Therefore, when the mechanical properties of existing test samples differ significantly from those of fractured rocks, or when preparing test samples of fractured rocks from another stratum, the corresponding water-cement-sand-gravel configuration can be obtained through the linear relationship and the mechanical properties of the fractured rocks in this embodiment. Test samples with mechanical properties similar to those of the fractured rocks can then be prepared using this water-cement-sand-gravel configuration.

[0052] When the mechanical property is expressed as compressive strength, the compressive strength of multiple test samples is obtained through experiments. Then, by linearly fitting the compressive strength of the test samples with the water-cement ratio and sand-cement ratio in the water-cement-sand-cement mixture, the corresponding linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio is obtained. This linear relationship is as follows: ,in, This refers to compressive strength; This refers to the sand-to-ash ratio; This refers to the water-cement ratio. When the mechanical properties are expressed as the elastic modulus, the elastic modulus of multiple test samples is obtained experimentally. Then, by linearly fitting the elastic modulus of the test samples with the water-cement ratio and sand-cement ratio in the water-cement-sand-cement mixture, the corresponding linear relationship between the elastic modulus and the water-cement ratio and sand-cement ratio is obtained. This linear relationship is: Where E refers to the modulus of elasticity. Given the compressive strength and modulus of elasticity of fractured rock, test samples with compressive strength and modulus of elasticity similar to those of fractured rock can be produced by using the linear relationships between compressive strength and water-cement ratio and sand-cement ratio, and between the modulus of elasticity and water-cement ratio and sand-cement ratio.

[0053] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S14 includes steps S51 to S55: S51: Determine the first cement casting model based on the external dimensions of the fractured rock.

[0054] Specifically, 3D technology is used to scan the external dimensions of the fractured rock, and the obtained data is imported into modeling software. The modeling software processes the data to create a corresponding first cement casting model. The constructed first cement casting model is a rectangular shell with no obstructions on the top and bottom, and its internal dimensions are the same as the external dimensions of the fractured rock.

[0055] S52: Based on the scanned crack profile, determine a plane tangent to the convex surface of the crack profile.

[0056] Specifically, to simulate the cracks in fractured rock, the crack profile constructed during the scanning modeling of the fractured rock contains many protrusions, which simulate the cracks in the fractured rock. Since the crack surface mold is printed based on the crack profile, it is also uneven. To ensure the limiting plate makes tight contact with the crack surface mold and effectively limits its position, this embodiment also determines a plane tangent to the convex surface of the crack profile. Because this plane is tangent to the crack profile, if a limiting plate is placed at this plane, it will be tangent to the crack surface mold. During the pouring of the target cement, the limiting plate can effectively prevent the crack surface mold from shifting under the pressure of the target cement, thus achieving precise positioning of the crack surface mold.

[0057] S53: Based on the distribution of the plane and the scanned crack profile in the fractured rock, determine the position of the groove group corresponding to the crack profile in the first cement casting model.

[0058] Specifically, since different crack profiles are located at different positions in the fractured rock, the distribution position of the crack profiles in the first cement casting model is determined based on their location within the fractured rock. Simultaneously, the distribution position of the planes tangent to the crack profiles in the first cement casting model can also be determined. To better secure the limiting plate, this embodiment also intends to construct a set of grooves in the first cement casting model. This set of grooves is used to place the limiting plate, and since the location of the plane is the location of the limiting plate, the position of the groove set corresponding to each crack profile in the first cement casting model can be determined by the distribution positions of the crack profiles and the planes.

[0059] S54: Determine the cement casting model based on the position of the first cement casting model and the groove group corresponding to each crack profile in the first cement casting model.

[0060] S55: Print the cement casting model to obtain a cement casting mold.

[0061] Specifically, after determining the positions of the groove groups corresponding to each crack profile within the first cement casting model, multiple groove groups are constructed using modeling software based on the first cement casting mold. The new model obtained after constructing all the groove groups corresponding to all crack profiles is the cement casting model. The cement casting model is then printed using 3D printing technology to obtain the corresponding cement casting mold.

[0062] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S53 includes steps S61 to S62: S61: Extend the plane that is tangent to the convex surface of the crack profile to obtain two line segments that intersect the extended plane with the two sides of the first cement casting model.

[0063] Specifically, the crack profile contains multiple raised sections representing the crack. Since three raised sections connected together can define a plane, this plane is the plane tangent to the convex surface of the crack profile. Based on the position of the plane in the fractured rock, the plane is simulated at the corresponding position in the first cement casting model corresponding to the fractured rock. The simulated plane is then extended, and the two sides of the extended plane intersect with the two sides of the first casting model, with the two intersecting parts forming two line segments.

[0064] S62: Based on two intersecting line segments, determine the position of the groove group corresponding to the crack profile in the first cement casting model.

[0065] Specifically, since two line segments are left after the plane intersects with the first casting model, and since the function of the groove group is to fix the limiting plate, these two line segments are determined as the groove group corresponding to the crack profile. The position of the two line segments in the first cement casting model is the position of the groove group in the first cement casting model.

[0066] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S15 includes steps S71 to S74: S71: Apply lubricating oil to the inner wall and cracked surface of the cement casting mold.

[0067] S72: The first segment in the cement casting mold that has not been filled with cement along the casting direction is determined as the segment to be cast, wherein the casting segment is divided by the groove group corresponding to the crack profile.

[0068] S73: Place the limiting plate corresponding to the layer to be poured into the groove group of the layer to be poured.

[0069] S74: The crack surface mold corresponding to the layer to be poured is placed into the layer to be poured with its convex surface tightly against the limiting plate.

[0070] Specifically, in order to ensure that the solidified target cement can be easily demolded and the crack surface mold can be easily removed from the cement casting mold, in this embodiment, the inner wall of the cement casting mold and the crack surface mold are coated with lubricating oil before the crack surface mold is placed into the cement casting mold.

[0071] Since each crack profile has its own corresponding groove group, and in order to accurately simulate the crack morphology, this embodiment uses the groove group corresponding to each crack profile as a benchmark to divide the cement casting mold into layers. This allows for layer-by-layer pouring during the cement casting mold pouring process, with each layer simulating the crack corresponding to a crack profile. Specifically, a pouring direction is set before the actual pouring, and the first layer in the cement casting mold along the pouring direction that has not yet been filled with cement is determined as the layer to be poured. Then, the limiting plate corresponding to this layer to be poured is placed in the groove group of that layer. Furthermore, since the convex surfaces of the crack profiles are different, the inclination angles of the tangent planes corresponding to each crack profile are also different. Therefore, the inclination angles of the multiple limiting plates placed in the multiple groove groups relative to the cement casting mold are also different. Thus, in order to ensure that the limiting plates can make close contact with the cement casting mold and prevent the target cement from flowing out from the gap between the limiting plates and the cement casting mold, limiting plates of different lengths should be placed for different groove groups so that the limiting plates can fit the cement casting mold even if they are tilted.

[0072] While placing the limiting plate in the layer to be poured, a crack surface mold corresponding to the layer to be poured, coated with lubricating oil, is also placed in the layer to be poured. The crack surface mold should be placed with its convex side tightly against the limiting plate in the layer to be poured, so that the limiting plate can limit the movement of the crack surface mold.

[0073] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock. In this method for preparing test samples of fractured rock, step S16 includes steps S81 to S85: S81: Prepare the target cement according to the water-cement-sand-gravel configuration ratio corresponding to the target test sample.

[0074] S82: Pour the target cement into the cement casting mold into the section to be cast, and obtain the casting section.

[0075] S83: When the target cement in the pouring section is in a state between the initial setting time and the final setting time, remove the mold and limiting plate corresponding to the crack surface of the pouring section.

[0076] S84: Along the cement pouring direction, the target cement is poured into the new pouring section in the cement pouring mold to obtain a new pouring section.

[0077] S85: When the target cement in the new pouring section is in a state between the initial setting time and the final setting time, remove the crack surface mold and the limiting plate corresponding to the new pouring section until all sections of the cement pouring mold are poured, and obtain the test sample corresponding to the fractured rock.

[0078] To improve the quality of the pouring and the accuracy of crack simulation, this embodiment selects a layer-by-layer pouring method for the cement casting mold. For example... Figure 5 The diagram shows a layer-by-layer pouring method.

[0079] Specifically, the water-cement-sand-gravel configuration ratio corresponding to the target test sample is determined as the configuration ratio of the test sample. A mixed slurry is prepared using this water-cement-sand-gravel configuration ratio. Then, an antifoaming agent is added to the mixed slurry and mixed evenly to obtain the uncured target cement.

[0080] The target cement is poured into the section to be poured in a cement casting mold that has been fitted with a limiting plate and a crack surface mold, thus obtaining the pouring section. To ensure that the target cement perfectly simulates the crack morphology according to the crack mold, the limiting plate and crack surface mold can only be removed after the target cement can replicate the crack; that is, at least after the target cement has reached its initial setting time. However, because it is difficult to remove the crack surface mold that adheres to the target cement after it has fully solidified, the limiting plate and crack surface mold must be removed before the target cement reaches its final setting time. Therefore, the optimal time to remove the limiting plate and crack surface mold is between the initial and final setting times of the target cement.

[0081] After removing the limiting plate and crack surface mold of the previous pouring section, the first section without cement pouring is designated as the new pouring section along the pouring direction. Target cement is poured into the new pouring section where the limiting plate and crack surface mold are placed, thus obtaining the corresponding pouring section. When the target cement in the new pouring section is between its initial and final setting times, the crack surface mold and limiting plate corresponding to the new pouring section are removed again. This process is repeated until all sections in the cement pouring mold are poured. The solidified target cement is then demolded to obtain a test sample corresponding to the fractured rock. The shape of this test sample is as follows... Figure 6 As shown, Figure 6 A schematic diagram of a test sample is provided.

[0082] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing test samples of fractured rock, the method further comprising steps S91 to S92: S91: Curing the test sample corresponding to the obtained fractured rock for a preset time to obtain the first test sample.

[0083] S92: The first test sample is polished based on the preset size to obtain the target test sample of the preset size.

[0084] In geological exploration, test samples made from fractured rocks can be used for fluid simulation experiments and mechanical experiments. In order to meet the specification requirements of the test samples for the experimental instruments used in fluid simulation experiments and mechanical experiments, the test samples obtained in this embodiment were further polished.

[0085] Specifically, to ensure the obtained test samples have a more stable shape and are easier to grind, the test samples obtained through cement casting molds were cured for a preset time, typically 28 days. After curing, the first test sample was obtained. Then, according to the specifications of the test instrument for the sample to be tested, a preset size was set, and the first test sample was then ground according to the preset size to obtain the target test sample corresponding to that preset size.

[0086] In conjunction with the above embodiments, in one implementation, this application also provides a method for preparing a test sample of fractured rock, wherein the dimensions of the test sample are: 50 mm in length, 50 mm in width, and 100 mm in height.

[0087] Specifically, in order to detect the mechanical properties of fractured rock, mechanical experiments need to be conducted on the fractured rock. The experimental instruments used in the mechanical experiments have specific requirements for the sample to be tested. The required dimensions of the sample to be tested are 50mm in length, 50mm in width, and 100mm in height. Therefore, in order to conduct the test smoothly, the fractured rock that has been drilled out is ground to meet these dimensions. Correspondingly, the size of the test sample made from the fractured rock should also meet the requirements of the sample to be tested, which also facilitates the mechanical experiment on the test sample.

[0088] The test sample preparation method for fractured rock provided in this application provides a test sample whose mechanical properties are closer to those of fractured rock. At the same time, the cracks in the test sample perfectly simulate the cracks in fractured rock, which makes it easier for subsequent experimental data obtained from the test sample to be more consistent with the data of real fractured rock strata, and also makes it easier for engineers to formulate more reasonable drilling plans.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0090] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0091] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0092] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes that element.

[0093] The above provides a detailed description of a method for preparing test samples of fractured rock provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method of preparing a test sample of a fractured rock, characterized by, The method includes: A predetermined number of test samples were prepared based on different configuration ratios of water, lime, sand, and gravel. Based on the mechanical properties of each test sample and the fractured rock, the target test sample is determined; Scan the fracture profile of the fractured rock and print the fracture surface mold of each fracture profile. Based on the external dimensions of the fractured rock and the distribution of crack profiles in the fractured rock, a cement casting mold corresponding to the fractured rock is printed. The cement casting mold includes a groove group for fixing a limiting plate, which is used to limit the mold on the crack surface. The crack surface mold is placed into the cement casting mold, and the limiting plate is placed into the corresponding groove group to limit the crack surface mold; The target cement, prepared according to the water-cement-sand-gravel configuration ratio corresponding to the target test sample, is poured into the cement casting mold after being limited, and the test sample corresponding to the fractured rock is obtained.

2. The method of preparing a test sample of a fractured rock according to claim 2, characterized in that, Based on the mechanical properties of each test sample and fractured rock, the target test samples are determined, including: Mechanical experiments were conducted on fractured rocks to obtain their mechanical properties. Mechanical experiments were conducted on each test sample to obtain the mechanical properties of each test sample. The mechanical properties of the fractured rock were compared with those of each test sample to obtain the comparison results for each test sample. The target test sample is determined based on the comparison results of each test sample.

3. The method of preparing a test sample of fractured rock according to claim 2, wherein, Based on the comparison results of each test sample, the target test samples are determined, including: Based on the comparison results of each test sample, all test samples are sorted to obtain the sorting results. The comparison results are the similarity between the mechanical properties of each test sample and the mechanical properties of the fractured rock. The test sample ranked first in the sorting results is determined as the target test sample.

4. The method of preparing a test sample of fractured rock according to claim 2, wherein, The method further includes: Based on the water-cement-sand-gravel configuration ratio and mechanical performance of each test sample, the linear relationship between mechanical performance and the water-cement ratio and sand-cement ratio in the water-cement-sand-gravel configuration ratio is determined. Based on the linear relationship and the mechanical properties of the fractured rock, the water-cement sand-gravel configuration ratio of the target test sample is determined. The mechanical properties include compressive strength and elastic modulus; When the mechanical property is expressed as compressive strength, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows: in, This refers to compressive strength; This refers to the sand-to-cement ratio; This refers to the water-cement ratio; When the mechanical property is expressed as elastic modulus, the linear relationship between the compressive strength and the water-cement ratio and sand-cement ratio in the water-cement sand-aggregate mixture is as follows: Here, E refers to the elastic modulus.

5. The method for preparing test samples of fractured rock according to claim 3, characterized in that, Based on the external dimensions and crack profile distribution of the fractured rock, a cement casting mold corresponding to the fractured rock is printed, including: Based on the shape and dimensions of the fractured rock, the first cement casting model was determined; Based on the scanned crack profile, a plane tangent to the convex surface of the crack profile is determined; Based on the distribution of the plane and the scanned crack profile in the fractured rock, the position of the groove group corresponding to the crack profile in the first cement casting model is determined. The cement casting model is determined based on the position of the first cement casting model and the groove group corresponding to each crack profile in the first cement casting model. The cement casting model is printed to obtain a cement casting mold.

6. The method for preparing test samples of fractured rock according to claim 5, characterized in that, Based on the distribution of the plane and scanned crack profiles in the fractured rock, the position of the groove group corresponding to the crack profile in the first cement casting model is determined, including: The plane tangent to the convex surface of the crack profile is extended to obtain two line segments that intersect the extended plane with the two sides of the first cement casting model. Based on two intersecting line segments, the position of the groove group corresponding to the crack profile in the first cement casting model is determined.

7. The method for preparing test samples of fractured rock according to claim 6, characterized in that, The crack surface mold is placed into the cement casting mold, and the limiting plate is placed into the corresponding groove group to limit the crack surface mold, including: Apply lubricating oil to the inner wall and cracked surface of the cement casting mold; The first segment in the cement casting mold that has not been filled with cement along the casting direction is defined as the segment to be cast. The segment to be cast is divided by the groove group corresponding to the crack profile. Place the limiting plate corresponding to the layer to be poured into the groove group of the layer to be poured; The crack surface mold corresponding to the layer to be poured is placed into the layer with its convex surface tightly against the limiting plate.

8. The method for preparing test samples of fractured rock according to claim 7, characterized in that, The target cement, prepared according to the water-cement-sand-gravel ratio corresponding to the target test sample, is poured into a cement casting mold after being limited to a certain position to obtain a test sample corresponding to the fractured rock, including: Based on the water-cement-sand-gravel configuration ratio corresponding to the target test sample, the target cement is prepared to obtain the target cement. The target cement is poured into the cement casting mold into the layer to be cast, thereby obtaining the casting layer; When the target cement in the pouring section is in a state between the initial setting time and the final setting time, remove the mold and limiting plate corresponding to the crack surface of the pouring section. Along the cement pouring direction, the target cement is poured into the new pouring section in the cement pouring mold to obtain a new pouring section. When the target cement in the new pouring section is in a state between the initial setting time and the final setting time, the crack surface mold and the limiting plate corresponding to the new pouring section are removed. This process continues until all sections in the cement pouring mold are poured, at which point a test sample corresponding to the fractured rock is obtained.

9. The method for preparing test samples of fractured rock according to claim 1, characterized in that, The method further includes: The test sample corresponding to the obtained fractured rock is cured for a preset time to obtain the first test sample; The first test sample is polished based on a preset size to obtain a target test sample of the preset size.

10. The method for preparing test samples of fractured rock according to claim 1, characterized in that, The dimensions of the test sample are: 50mm in length, 50mm in width, and 100mm in height.

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