Simulated sample of compression-shear salt tectonics with recordable deformation history and test method

Abstract

The present application relates to salt structure compression torsion test technical field, specifically and it is the compression torsion salt structure simulation sample of recordable deformation history and test method, it includes: from bottom to top is stacked in turn with the salt under layer of simulation salt under sedimentary rock layer, the salt layer and the salt upper layer of salt layer, the salt layer includes simulation brittle stratum, simulation soft mudstone layer and simulation plastic salt rock layer, several parallel strain sensing layer, the strain sensing layer is located respectively in the interface layer of salt under layer inside, salt under layer and salt layer interface, salt layer and salt upper layer interface at salt layer inside, the present application is activated in stages to the early, middle and late stage of deformation by three kinds of microcapsules sensitive to different wavelengths, and the area of high strain in different time window is marked with different colors or fluorescence spectrum, so that the time stage information of deformation occurrence can be directly read from the inside of the sample after the experiment.

Description

Technical Field

[0001] This invention relates to the field of salt structure compression-torsion testing technology, and more specifically to a compression-torsion salt structure simulation specimen and testing method that can record deformation history. Background Technology

[0002] Salt structures refer to various geological formations created by the plastic flow of underground salt layers during crustal movement, such as salt domes, salt pillows, and salt diapirs. Due to the compactness and plastic flow characteristics of salt layers, salt structures are of great significance for oil and gas reservoir sealing, underground energy storage, and geological carbon dioxide sequestration. In salt structure research, compressional-torsional salt structures are a special type, characterized by complex deformation of the salt layer under simultaneous compression and shear torsion (compressional-torsional action), forming structural patterns such as folds and faults.

[0003] Currently, the main method for studying the deformation mechanism of compressional-shear salt structures is indoor physical simulation experiments. Based on the principle of similarity, researchers use quartz sand to simulate brittle sedimentary rock layers, microglass beads to simulate weak mudstone layers, and silica gel to simulate plastic gypsum-salt layers. Compression and shear loads are applied to the sand box model, and the deformation morphology of the model is observed, thereby inverting the deformation law of salt structures under real geological conditions. During the experiment, the deformation profile of the model is usually observed through the top surface, sides, or a pre-set transparent window. After the experiment, the final internal deformation morphology is often obtained by dissecting the model.

[0004] Because the simulation materials (such as quartz sand, silica gel, etc.) are not transparent, existing physical simulation experimental methods cannot directly obtain the strain distribution of each layer inside the model in the entire planar area, nor can they obtain dynamic process information such as the folding sequence, the expansion path of the shear band, and the order of deformation initiation of different layers during the deformation process.

[0005] Therefore, how to obtain the spatiotemporal evolution information of strain in multiple layers inside the sample during the physical simulation experiment of salt structure without interfering with the deformation of the model is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the technical problems existing in the compressive-torsional salt structure in the prior art, the first aspect of the present invention proposes a technical solution: a compressive-torsional salt structure simulation specimen capable of recording deformation history, comprising: The layers are stacked sequentially from bottom to top, including a pre-salt layer, a gypsum-salt layer, and an over-salt layer, which simulate pre-salt sedimentary rock layers. The gypsum-salt layer includes simulated brittle strata, simulated weak mudstone layers, and simulated plastic gypsum-salt rock layers. Several parallel strain sensing layers are respectively located inside the pre-salt layer, at the interface between the pre-salt layer and the gypsum layer, at the interface layer inside the gypsum layer, and at the interface between the gypsum layer and the pre-salt layer. The strain-sensing layer includes a high-transmittance base layer and photosensitive color-changing units uniformly dispersed in the high-transmittance base layer; The photosensitive color-changing unit contains at least two types of microcapsules that are sensitive to ultraviolet light of different wavelengths and are encapsulated with color-developing labeling core materials. The color-developing labeling core materials are monochromatic color-developing agents or single-emission spectral fluorescent agents. The color-developing labeling core materials in different types of photosensitive color-changing units have different monochromatic color-developing agents or multiple single-emission spectral fluorescent agents. The wall material of the microcapsule has photosensitive softening mechanical properties, maintaining a preset mechanical strength when there is no ultraviolet light of a specific wavelength, and softening after being irradiated with ultraviolet light of a specific wavelength, so as to significantly reduce its mechanical fracture threshold. The strain-sensing layer is made to fracture when exposed to ultraviolet light of a specific wavelength and when the stress exceeds the fracture threshold. The location of the high-stress region and the time window in which the high stress occurs are characterized by a monochromatic colorimetric agent or a single-emission spectral fluorescent agent after fracture.

[0007] Preferably, the high-transmittance substrate of the strain sensing layer is transparent silicone or transparent micro glass beads, so as to form a horizontal light guide channel that can conduct external ultraviolet light beams along the planar direction of the strain sensing layer.

[0008] Preferably, the photosensitive color-changing unit includes a first microcapsule, a second microcapsule, and a third microcapsule, with corresponding photosensitive trigger wavelengths of 365nm, 385nm, and 405nm, respectively, and the color or fluorescence spectrum of the color developer encapsulated inside is independent of each other. When not exposed to light, the mechanical fracture threshold of the wall material of the microcapsule is greater than 0.5 MPa. After being irradiated with ultraviolet light of the corresponding wavelength, the mechanical fracture threshold is reduced to below 0.1 MPa.

[0009] Preferably, the pre-salt layer and the over-salt layer are formed by laying dry quartz sand with a particle size of 100-400 μm; the simulated brittle strata are formed by laying dry quartz sand with a particle size of 100-400 μm; the simulated weak mudstone layer is formed by laying micro glass beads with a particle size of 100-400 μm; and the simulated plastic gypsum-salt rock layer is formed by laying polymeric silicone resin material.

[0010] A second aspect of this invention provides a technical solution: a method for testing compressive-torsional salt structures capable of recording deformation history. Using the aforementioned compressive-torsional salt structure simulation specimen capable of recording deformation history, the method includes the following steps: Step S1: Using a layer-by-layer laying process, lay the lower salt layer, the gypsum salt layer, and the upper salt layer sequentially from bottom to top; During the laying process, the strain sensing layer is laid at a preset layer, which includes: the interior of the pre-salt layer, the interface between the pre-salt layer and the gypsum-salt layer, the interfaces of each sub-layer inside the gypsum-salt layer, and the interface between the gypsum-salt layer and the salt overlayer. After each strain-sensing layer is laid, the overlying simulated geological material is laid until the entire simulated sample is completed. Step S2: Place the laid-up simulated sample between the fixed plate and the push plate of the compression-torsion test device, and apply compression and shear loads to the simulated sample by pushing the movable seat through the drive component. Step S3: During the continuous application of load, when the displacement reaches the preset threshold, ultraviolet light of the corresponding wavelength is simultaneously irradiated to soften the corresponding type of microcapsule wall material, which then breaks and reveals color when subjected to subsequent deformation and stress. Step S4: After the experiment, the sample material is removed layer by layer from top to bottom. Whenever a strain sensing layer is exposed, a color image or fluorescence image of that layer is acquired using an image acquisition device. The location, color type, and color depth of the colored area in each strain sensing layer are recorded. Step S5: Based on the color types of the color markers in the images of different strain sensing layers, distinguish the time stages in which deformation occurs; Based on the color intensity or fluorescence intensity of the chromogenic marker, the strain magnitude at that location during that time period is semi-quantitatively assessed.

[0011] Preferably, in step S3, during the application of the compressive-torsional load, ultraviolet light of a specific wavelength is continuously driven and irradiated in stages to activate the corresponding type of microcapsules: First marking stage: When the displacement of the active seat reaches the preset first displacement threshold, the side of the sample is irradiated with ultraviolet light of the first wavelength corresponding to the height position of each strain sensing layer 200, so that the wall material of the first microcapsule softens. In the area where the stress in the deformation inside the sample is higher than the rupture threshold after softening, the first microcapsule ruptures and releases the first color marker. Second marking stage: When the displacement of the active seat reaches the preset second displacement threshold, the side of the sample is irradiated with ultraviolet light of the second wavelength corresponding to the height position of each strain sensing layer 200, so as to soften the wall material of the second microcapsule; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation, the second microcapsule ruptures and releases the second color marker. Third marking stage: When the displacement of the active seat reaches the preset third displacement threshold, the side of the sample is irradiated with ultraviolet light of the third wavelength corresponding to the height position of each strain sensing layer 200, so that the wall material of the third microcapsule softens; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation, the third microcapsule ruptures and releases the third color marker.

[0012] Preferably, the first displacement threshold is 25% to 35% of the total planned displacement, the second displacement threshold is 55% to 65% of the total planned displacement, and the third displacement threshold is 75% to 85% of the total planned displacement.

[0013] Preferably, in step S3, ultraviolet light is introduced into the sample from the side along the horizontal cross-section of the strain sensing layer; and high-energy pulsed ultraviolet laser is used for instantaneous irradiation for 1 to 5 seconds, during which the load driving component of the test device continues to operate continuously.

[0014] Preferably, in step S4, the layer-by-layer peeling is performed by brushing or vacuuming to remove the loose quartz sand and peelable silica gel layer layer by layer from the top surface of the sample.

[0015] Preferably, in step S5, deformation history analysis includes RGB channel separation or fluorescence spectrum separation of each strain sensing layer image, and obtaining the relative strain distribution map of each time stage through grayscale analysis.

[0016] Compared with the prior art, the advantages of the present invention are as follows: This invention achieves in-situ self-recording of the internal deformation history in physical simulation experiments of compressive-torsional salt structures by pre-placing microcapsules with photosensitive softening mechanical properties in key layers of simulated samples and combining this with a staged ultraviolet irradiation strategy. Specifically, three types of microcapsules sensitive to different wavelengths are activated in stages corresponding to the early, middle, and late stages of deformation, respectively. Different colors or fluorescence spectra are used to identify regions of high strain within different time windows, allowing the time stage information of deformation to be directly read from inside the sample after the experiment.

[0017] By setting strain-sensing layers at key locations such as the interior of the pre-salt layer, the interface between the pre-salt layer and the gypsum-salt layer, the interfaces of each sub-layer of the gypsum-salt layer, and the interface between the gypsum-salt layer and the upper salt layer, and by using layer-by-layer peeling and image acquisition, it is possible to obtain the spatiotemporal distribution data of strain at multiple key structural interfaces along the entire height of the sample, providing a direct basis for analyzing the layered differential deformation and coupling-decoupling relationship of the salt structure.

[0018] Furthermore, since the number of microcapsules ruptured is positively correlated with the magnitude of the mechanical stress, the amount of dye released after rupture determines the color density or fluorescence intensity of the color development area. By pre-calibrating the relationship between color density / fluorescence intensity and strain, the magnitude of strain at each time stage can be semi-quantitatively assessed. Attached Figure Description

[0019] The accompanying drawings are not strictly to scale. In the drawings, each identical or nearly identical component shown in the various figures can be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of the compression-torsion salt structure simulation sample that can record deformation history, as shown in this invention. Figure 2This is a schematic diagram of the strain sensing layer shown in this invention; Figure 3 This is a schematic diagram of a simulated sample of a compression-torsion salt structure as shown in this invention being placed in a compression-torsion experimental apparatus. Figure 4 This is a schematic diagram of the microcapsule rupture state shown in this invention; Figure 5 This is a schematic diagram of the strain sensing layer shown in this invention under the dual action of first wavelength ultraviolet light irradiation and pressure; Figure 6 This is a schematic diagram of the rupture of the first microcapsule in the strain sensing layer of the present invention under the action of first wavelength ultraviolet light irradiation and pressure. Figure 7 This is a schematic diagram of the strain sensing layer shown in this invention under the dual action of second-wavelength ultraviolet light irradiation and pressure; Figure 8 This is a schematic diagram of the second microcapsule rupture of the strain sensing layer shown in this invention under the action of second wavelength ultraviolet light irradiation and pressure. Figure 9 This is a schematic diagram of the strain sensing layer shown in this invention under the dual action of third-wavelength ultraviolet light irradiation and pressure; Figure 10 This is a schematic diagram of the rupture of the third microcapsule in the strain sensing layer of the present invention under the action of third wavelength ultraviolet light irradiation and pressure. Detailed Implementation

[0020] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0021] {Example 1} Combination Figure 1 As shown, the first aspect of the present invention proposes a technical solution, a simulated sample of compressive-torsional salt structure capable of recording deformation history, comprising a subsalt layer 101, a gypsum-salt layer 102, and an oversalt layer 103, which are stacked sequentially from bottom to top to simulate subsalt sedimentary rock layers 100. The gypsum-salt layer 102 includes a simulated brittle stratum 102a, a simulated weak mudstone layer 102b, and a simulated plastic gypsum-salt rock layer 102c.

[0022] Specifically, in preparing the pre-salt layer 101, dry quartz sand with a particle size of 100~400μm is used and laid layer by layer through flat laying and vibration compaction to simulate the brittle deformation behavior of natural pre-salt sedimentary rock layers. The upper salt layer 103 is also made using the same quartz sand material and laying process.

[0023] In an optional embodiment, the preparation of the gypsum-salt layer 102 is based on the rheological differences of its internal lithologies, and the selection of materials is differentiated accordingly: Among them, the simulated brittle stratum 102a is laid with dry quartz sand with a particle size of 100~400μm, with an internal friction angle of about 25~30° and cohesion close to zero. It follows the Mohr-Coulomb failure criterion to simulate the relatively brittle interlayers (such as anhydrite layers or carbonate rock interlayers) in the gypsum-salt layer 102.

[0024] Among them, the simulated weak mudstone layer 102b is laid with micro glass beads with a particle size of 100~400μm. The micro glass beads have a smooth surface and extremely low cohesion between particles. Their plasticity is between that of quartz sand and silica gel, which can better simulate the ductile shear deformation behavior of the low-strength mudstone interlayer in the natural gypsum salt layer 102 under compression and torsion.

[0025] Among them, the simulated plastic gypsum-salt rock layer 102c uses polymeric silicone resin (silicone). During the laying process, uncured liquid silicone can be injected into the mold and leveled, and then cured at room temperature or by heating to form a plastic layer with a preset thickness; or a pre-formed silicone plate can be directly embedded.

[0026] Because silicone exhibits Newtonian fluid properties, its dynamic viscosity at low strain rates is approximately 5 × 10⁻⁶. 4 Pa·s, which closely approximates the rheological characteristics of gypsum-salt rocks under in-situ temperature and pressure conditions underground, makes it an ideal material for simulating the plastic flow of salt layers.

[0027] As mentioned above, by combining materials with different mechanical properties, the simulated sample can realistically reproduce the delamination and differential deformation characteristics of thin interlayered gypsum salt layers in nature under compressive and torsional stress fields.

[0028] Furthermore, in combination Figure 1 As shown, several parallel strain sensing layers 200 are located inside the pre-salt layer 101, at the interface between the pre-salt layer 101 and the gypsum layer 102, at the interface layer inside the gypsum layer 102, and at the interface between the gypsum layer 102 and the salt overlayer 103.

[0029] By placing the strain sensing layer 200 at the aforementioned specific layer, a three-dimensional monitoring array capable of comprehensively capturing the spatiotemporal evolution information of compression-torsional salt structures can be constructed.

[0030] Specifically, the pre-salt layer 101 usually serves as a relatively stable substrate under compression and torsion, but its upper part may still participate in deformation, especially when the gypsum layer 102 undergoes large-scale plastic flow. The top of the pre-salt layer 101 may be dragged and entangled in deformation. A strain sensing layer 200 is set at the upper part of this layer, which can be used to monitor whether and when the substrate undergoes entangled shear deformation.

[0031] Specifically, the interface between the pre-salt layer 101 and the gypsum salt layer 102 is one of the most important slip surfaces in the deformation of salt structures. The plastic flow of the gypsum salt layer 102 is very likely to decouple from the rigid substrate at this interface, forming large-scale shear slip. Setting a strain sensing layer 200 here can accurately record the initiation time, spatial range, and magnitude of shear slip, which is a key observation window for studying the decoupling mechanism of salt structures.

[0032] Specifically, since the gypsum-salt layer 102 itself is a thin interlayered structure composed of simulated brittle strata 102a, simulated weak mudstone layer 102b and simulated plastic gypsum-salt rock layer 102c, the mechanical properties of each sublayer are significantly different. Under compression and torsion, interlayer sliding, stress concentration and strain localization are very likely to occur at the interface of each sublayer.

[0033] Thus, by setting strain sensing layers 200 between the simulated brittle strata 102a and the simulated weak mudstone layer 102b, and between the simulated weak mudstone layer 102b and the simulated plastic gypsum-salt rock layer 102c, the relative motion sequence and strain distribution relationship of different sublayers during the deformation process can be observed, revealing the deformation coordination and differentiation laws within the thin interlayers.

[0034] Specifically, the interface between the gypsum-salt layer 102 and the overlying salt layer 103 is a key location for the upward transmission of stress and deformation in the salt structure. The uplift, puncture, or lateral flow of the gypsum-salt layer will directly act on the overlying salt layer, forming forced folds or fractures. Setting a strain sensing layer 200 here can be used to record when the overlying salt layer 103 begins to respond to the deformation of the gypsum-salt layer 102, the folding sequence, and the range of structural uplift. It is the core observation location for studying the coupling mechanism of salt structures.

[0035] As mentioned above, by systematically arranging the strain sensing layer 200, the strain history of the entire salt structure system during the compression-torsion deformation process can be completely obtained from the substrate to the caprock and from the slip surface to the internal layer interface.

[0036] Furthermore, in combination Figure 2 As shown, the strain sensing layer 200 includes a high-transmittance base layer 201 and photosensitive color-changing units 202 uniformly dispersed in the high-transmittance base layer 201.

[0037] Optionally, the high-transmittance base layer 201 can be made of transparent silicone or transparent microglass beads. This provides a light-guiding medium for the horizontal transmission of ultraviolet light within the layer, ensuring that light can cover the entire layer plane.

[0038] Since the simulated specimens of the compression-torsion salt structure usually have large planar dimensions (e.g., length and width of several hundred millimeters) and a certain thickness, and the covering material (quartz sand, silica gel, etc.) has a strong scattering and absorption effect on ultraviolet light, when irradiated only from the top surface of the specimen, ultraviolet light is difficult to penetrate the thick covering layer to reach the strain sensing layer 200 located deep inside, especially the sensing layer located inside the pre-salt layer 101 or at the bottom of the paste salt layer 102.

[0039] By constructing the high-transmittance substrate 201 as a transparent material and exposing its edges to the side of the sample, the ultraviolet light source can be directly directed at the edge of the strain-sensing layer 200 from the side of the sample. The transparent substrate 201 acts as a horizontal light guide channel, utilizing the principle of partial total internal reflection or low-loss transmission of light to efficiently transmit the ultraviolet beam to the entire layer plane. This ensures that microcapsules 210 at different locations within the layer receive sufficiently intense and uniform ultraviolet light irradiation, thereby guaranteeing the synchronicity and uniformity of rupture color development across the entire layer and improving the accuracy and reliability of strain marking.

[0040] Specifically, the fabrication method of the strain sensing layer 200 is as follows: If transparent silicone is selected, liquid transparent silicone (such as Dow Corning Sylgard 184) and photosensitive color-changing unit 202 are mixed evenly at a predetermined mass ratio (such as 100:1 to 100:5). After vacuum degassing, it is injected into the mold, leveled, and cured into a thin layer with a thickness of 1 to 3 mm. If transparent micro glass beads are selected, colorless transparent glass beads with a particle size of 100~400μm are uniformly mixed with the photosensitive color-changing unit 202 and directly spread into a thin layer of predetermined thickness during the laying process.

[0041] Furthermore, the photosensitive color-changing unit 202 can be prepared using conventional interfacial polymerization or in-situ polymerization methods.

[0042] Taking interfacial polymerization as an example, the selected photoresponsive polymer monomer (such as azobenzene-modified polyurethane prepolymer) is first dissolved in an oil phase solvent and mixed with a solution containing a colorimetric core material 212 (dye or fluorescent agent) to form an oil phase. This oil phase is then subjected to high-speed shear emulsification in an aqueous phase containing an emulsifier to form a stable oil-in-water emulsion. Subsequently, an aqueous reactive monomer (such as a polyamine) is slowly added to the emulsion, and a polymerization reaction occurs at the oil-water interface to form a polymer wall material 211 coated with the core material. After the reaction is complete, the mixture is filtered, washed, and dried to obtain powdered photosensitive color-changing unit 202. The microcapsule particle size can be controlled within the range of 10–50 μm by adjusting the emulsification shear rate, and its mechanical fracture threshold can be adjusted by controlling the degree of crosslinking of the wall material.

[0043] The photosensitive color-changing unit 202 includes at least two types of microcapsules 210 that are sensitive to ultraviolet light of different wavelengths and are internally coated with a color-developing labeling core material 212. The color-developing labeling core material 212 is a monochromatic color developer or a single-emission spectrum fluorescent agent. The color-developing labeling core material 212 in different types of photosensitive color-changing units 202 has different monochromatic color developers or multiple single-emission spectrum fluorescent agents.

[0044] Thus, combined Figure 4 As shown, when the microcapsule 210 ruptures under the dual action of ultraviolet light irradiation and mechanical force, the colorimetric core material 212 is released and adheres to the rupture area, forming a mark that is significantly different from the surrounding material in color or fluorescence properties. Since different types of microcapsules correspond to different deformation time stages (activated in stages by ultraviolet light of different wavelengths) and each has an independent color or fluorescence spectrum, after the experiment, by observing or detecting the color type of the rupture area, it is possible to directly determine which time window the deformation of the area mainly occurred in (e.g., early, middle or late stage).

[0045] In an optional embodiment, the color-developing marking core material 212 is a single-color color developer, which can be dyes of different colors such as blue, green, and red. The marking results released after the material breaks are directly visible to the naked eye and do not require special testing equipment. They can be clearly recorded with a regular digital camera after being peeled off layer by layer.

[0046] However, dyes of different colors may have spectral overlap in an image. When multiple colors are superimposed, image processing techniques such as RGB channel separation are required for demixing.

[0047] In other embodiments, the colorimetric labeling core material 212 is a single-emission fluorescent agent, such as a fluorescent dye with emission peaks of 450nm, 520nm, and 610nm. In this way, even if the number of microcapsules ruptures is small and the released fluorescence dose is extremely small, a strong fluorescence signal can still be generated under excitation light of a specific wavelength. Moreover, the emission spectra of different fluorescent agents are independent of each other. By selecting corresponding narrowband filters for imaging, spectral crosstalk between the labeling signals at different time stages can be completely avoided, achieving higher precision quantitative analysis.

[0048] Furthermore, the wall material 211 of the microcapsule 210 has photosensitive softening mechanical properties, maintaining a preset mechanical strength when there is no specific wavelength of ultraviolet light irradiation, and softening after being irradiated with specific wavelength of ultraviolet light to significantly reduce its mechanical fracture threshold, so that the strain sensing layer 200 fractures when irradiated with specific wavelength of ultraviolet light and the stress is higher than the fracture threshold, so as to characterize the location of the high stress area and the time window of high stress by the monochromatic colorimetric agent or single emission spectrum fluorescent agent after fracture.

[0049] Therefore, the rupture of the wall material 211 requires the simultaneous fulfillment of two conditions: first, irradiation with ultraviolet light of a specific wavelength (softening condition), and second, sufficiently large mechanical stress (mechanical condition) to ensure that the microcapsules 210 will not rupture prematurely due to simple mechanical loads during storage, sample laying, and the early deformation stage when they are not exposed to light, thus ensuring the accuracy of the marking. At the same time, it also avoids mismarking in areas that are only exposed to light but do not deform.

[0050] In addition, by irradiating different wavelengths of ultraviolet light in stages, different time windows are set for different types of microcapsules 210. Before reaching a certain preset displacement threshold, even if strong deformation has occurred inside the sample, the wall material 211 will remain in a high-strength state and will not break because the corresponding wavelength of light has not been applied. Only when the experiment reaches the predetermined stage and the corresponding wavelength of light is applied will the wall material 211 soften, and the deformation that occurs within the time window and thereafter will trigger the rupture of this type of microcapsule. Therefore, it is possible to record the time stage of deformation by color type.

[0051] In an optional embodiment, the photosensitive color-changing unit 202 includes a first microcapsule 202a, a second microcapsule 202b and a third microcapsule 202c, with corresponding photosensitive trigger wavelengths of 365nm, 385nm and 405nm, respectively, and the color or fluorescence spectrum of the color developer encapsulated inside is independent of each other. When not exposed to light, the mechanical fracture threshold of the wall material 211 of the microcapsule 210 is greater than 0.5 MPa. After being irradiated with ultraviolet light of the corresponding wavelength, the mechanical fracture threshold is reduced to below 0.1 MPa.

[0052] Optionally, the wall material 211 of the first microcapsule 202a, the second microcapsule 202b, and the third microcapsule 202c is a functional polymer material with photoisomerization response characteristics.

[0053] Preferably, the matrix of wall material 211 is a photoresponsive modified polyurethane or polyurea resin, in which azobenzene derivative groups with photo-switching function are introduced into the molecular backbone or cross-linking network. In this molecular system, the mechanical state of wall material 211 is determined by the configuration of the azobenzene groups: Steady state (unexposed to light): The azophenyl groups are in a thermodynamically stable trans configuration, with tightly packed molecular chains and strong intermolecular hydrogen bonding, giving wall material 211 a high-modulus glassy state, with its macroscopic mechanical fracture threshold remaining above 0.5 MPa. In this state, normal compressive-torsional mechanical loads are insufficient to damage wall material 211, and the colorimetric core material 212 will not be released.

[0054] Activated state (irradiated by corresponding wavelength): Upon irradiation with ultraviolet light of a specific wavelength, the azophenyl groups rapidly undergo isomerization to the cis configuration. Due to the larger space occupancy and altered dipole moment of the cis configuration, the polymer chain spacing increases, and the hydrogen bond network partially dissociates. The wall material 211 undergoes an instantaneous phase transition from a glassy state to a highly elastic or viscous flow state, manifested as softening of the wall material 211. At this point, its mechanical fracture threshold significantly decreases to below 0.1 MPa. In this state, shear or compressive stress during experiments can easily cause the wall material 211 to fracture, releasing the internal colorimetric core material 212.

[0055] Furthermore, to achieve selective response to wavelengths of 365nm, 385nm, and 405nm, this invention modulates the electronic energy levels of the substituents on the azobenzene ring, enabling different types of microcapsules to possess independent spectral sensitivity windows. The first microcapsule 202a (365nm sensitive): its wall material 211 is preferably unsubstituted azobenzene modified polyurethane.

[0056] Its electron transition center is located in the range of 350~370nm, which can maximize the response to 365nm ultraviolet light, while producing almost no configurational change for light with wavelengths above 385nm.

[0057] The second microcapsule 202b (385nm sensitive): its wall material 211 is preferably an ortho-monofluorosubstituted azobenzene polymer.

[0058] By introducing a highly electronegative fluorine atom at the ortho position of the benzene ring, the electron cloud distribution of the azo group is altered by its sensing effect, causing a red shift of approximately 20 nm in its absorption peak. This achieves precise sensitivity to the 385 nm wavelength and frequency decoupling from 365 nm.

[0059] The third microcapsule 202c (405nm sensitive): its wall material is preferably an ortho-tetrafluorosubstituted azobenzene polymer or an azobenzene polymer with an amino / alkoxy push-pull electron system.

[0060] This structure significantly reduces the energy required for electronic transitions, shifting its effective response wavelength to the 400–410 nm range (visible violet region). The material exhibits extremely high isomerization efficiency under 405 nm irradiation, ensuring sensitivity during late-stage labeling in experiments.

[0061] Furthermore, by adjusting the crosslinking density of the wall material 211, its mechanical fracture threshold can be finely adjusted to ensure that it has a reliable fracture rate under compressive load after being irradiated by a laser pulse of the corresponding wavelength for a preset duration of seconds.

[0062] {Example 2} The second aspect of this invention provides a technical solution: a method for testing compressive-torsional salt structures capable of recording deformation history, using the compressive-torsional salt structure simulation specimen with recordable deformation history described in Example 1 above, comprising the following steps: Step S1: Laying the simulated sample The process of laying the salt layer 101, the gypsum salt layer 102 and the salt upper layer 103 are laid sequentially from bottom to top. During the laying process, a strain sensing layer 200 is laid at a preset layer location. The preset layer locations include: the interior of the pre-salt layer 101, the interface between the pre-salt layer 101 and the gypsum layer 102, the interfaces of each sub-layer inside the gypsum layer 102, and the interface between the gypsum layer 102 and the salt overlayer 103. After each strain-sensing layer of 200 mm is laid, the overlying simulated geological material is continued to be laid until the entire simulated sample is completed.

[0063] Step S2: Apply compressive and torsional loads The laid-up simulated sample is placed between the fixed plate 21 and the push plate 22 of the compression-torsion test device. The moving seat 10 is pushed by the driving component 30 to apply compression and shear loads to the simulated sample.

[0064] Specifically, in combination Figure 3 As shown, the compression-torsion test device includes: a fixed seat 11, a movable seat 12, a fixed plate 21, a push plate 22, and a driving component 30. The first end of the fixed seat 11 is provided with a first inclined surface 13, the movable seat 12 has a second inclined surface that fits against the first inclined surface 13, the fixed plate 21 is connected to the upper end surface of the fixed seat 11, and the push plate 22 is fixed to the upper end surface of the movable seat 12.

[0065] The drive component 30 (such as an electric servo cylinder or a hydraulic cylinder) is connected to the movable seat 12 and is used to push the movable seat 12 to move towards the fixed seat 11. Through the action of the first inclined surface 13, a compressive and torsional load with both compressive and shear components is applied to the simulated sample placed between the fixed plate 21 and the push plate 22.

[0066] Furthermore, the side walls of the fixing plate 21 and the push plate 22 are provided with light-transmitting windows, through which an external ultraviolet light source 40 provides ultraviolet light of a predetermined wavelength to the strain sensing layer 200 in the sample.

[0067] Step S3: Staged ultraviolet irradiation and deformation marking During the continuous application of load, when the displacement reaches a preset threshold, ultraviolet light of the corresponding wavelength is simultaneously irradiated to soften the corresponding type of microcapsule wall material, which then breaks and reveals color when subjected to subsequent deformation and stress.

[0068] In this process, ultraviolet light is introduced into the sample from the side along the horizontal cross-section of the strain sensing layer 200; and high-energy pulsed ultraviolet laser is used for instantaneous irradiation for 1 to 5 seconds, during which the load driving component of the test device continues to operate continuously.

[0069] Specifically, during the application of compressive and torsional loads, ultraviolet light of a specific wavelength is continuously driven and irradiated in stages to activate the corresponding type of microcapsules: Combination Figure 5 and Figure 6 As shown, in the first marking stage: when the displacement of the movable seat 10 reaches the preset first displacement threshold, the side of the sample is irradiated with ultraviolet light of the first wavelength (365nm) corresponding to the height position of each strain sensing layer 200, so that the wall material of the first microcapsule 202a softens. In the area where the stress in the deformation inside the sample is higher than the rupture threshold after softening (such as shear bands and wrinkled cores), the first microcapsule 202a ruptures and releases the first color marker, releasing a blue color developer (or blue fluorescent agent). The blue marker adheres to the sand grains or silicone surface of the rupture area, forming a permanent early deformation mark. Combination Figure 7 and Figure 8 As shown, in the second marking stage: when the displacement of the movable seat 10 reaches the preset second displacement threshold, ultraviolet light of the second wavelength (385nm) is used to irradiate the side of the sample corresponding to the height position of each strain sensing layer 200, so as to soften the wall material of the second microcapsule 202b; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation (such as shear bands, wrinkled cores), the second microcapsule 202b ruptures and releases the second color marker, releasing a green colorant (or green fluorescent agent), and the mid-term deformation position is recorded; Combination Figure 9 and Figure 10 As shown, in the third marking stage: when the displacement of the movable seat 10 reaches the preset third displacement threshold, the side of the sample is irradiated with ultraviolet light of the third wavelength (405nm) corresponding to the height position of each strain sensing layer 200, so that the wall material of the third microcapsule 202c softens; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation (such as shear bands, folded cores), the third microcapsule 202c ruptures and releases the third color marker, releasing a red colorant (or red fluorescent agent), and the late deformation position is recorded.

[0070] In an optional embodiment, the first displacement threshold is 25% to 35% of the total planned displacement, the second displacement threshold is 55% to 65% of the total planned displacement, and the third displacement threshold is 75% to 85% of the total planned displacement.

[0071] Step S4: Layer-by-layer peeling and image acquisition After the experiment, the sample material was removed layer by layer from top to bottom. Whenever a strain sensing layer 200 was exposed, a color image or fluorescence image of that layer was acquired using an image acquisition device. The location, color type, and color depth of the colored area in each strain sensing layer 200 were recorded.

[0072] Specifically, the stripping operation is carried out in a dark room or in a light-proof environment to avoid accidental activation of the undeveloped microcapsules by ambient ultraviolet light. Using a soft brush and a miniature vacuum cleaner, the loose quartz sand on the top layer 103 of the salt is carefully removed layer by layer, starting from the top surface of the sample. After removing about 5 to 10 mm of material, the surface of the strain-sensing layer 200 is carefully observed. When one strain-sensing layer 200 is completely exposed, the stripping is stopped. A high-resolution digital camera is used to vertically capture a color image or a fluorescent image of the layer under uniform white light or excitation light of the corresponding wavelength (for fluorescent agents).

[0073] After the filming is completed, record the layer information. If the strain sensing layer 200 is below a silicone layer that can be peeled off as a whole (such as simulated plastic gypsum-salt rock layer 102c), the edge of the silicone layer can be held with tweezers and peeled off as a whole to quickly expose the next strain sensing layer 200. For loose sand layers, continue to peel downwards using the brushing method.

[0074] Step S5: Deformation History Analysis Based on the color of the color markers in the images of different strain sensing layers 200, the time stages of deformation can be distinguished. Based on the color intensity or fluorescence intensity of the chromogenic marker, the strain magnitude at that location during that time period is semi-quantitatively assessed. By integrating the spatiotemporal marker information of each strain sensing layer 200, the spatiotemporal evolution history of strain inside the simulated specimen during the compressive-torsional deformation process is reconstructed.

[0075] In an optional embodiment, for samples using a single-color developer, the image is decomposed into three single-channel grayscale images—red (R), green (G), and blue (B)—using the RGB channel separation function. The B channel image primarily reflects the distribution of blue markings (early deformation), the G channel image primarily reflects the distribution of green markings (intermediate deformation), and the R channel image primarily reflects the distribution of red markings (late deformation).

[0076] For samples using a single emission spectrum fluorescent agent, three fluorescence images are acquired using narrowband filters of the corresponding wavelength, with no spectral crosstalk between the images.

[0077] Specifically, to obtain a strain distribution map, taking the blue channel image as an example, the grayscale value G (0~255) of each pixel is negatively correlated with the strain magnitude ε experienced at that location in the early deformation stage. Using the pre-calibrated formula ε=k×(255-G) / 255 (where k is a calibration coefficient related to the material and shooting conditions), the grayscale image can be converted into a relative strain distribution map for that time stage.

[0078] Similarly, by processing the green and red channel images, relative strain distribution maps of the intermediate and late deformation stages can be obtained.

[0079] Thus, by comprehensively comparing the analytical results of all strain-sensing layers 200, the method proposed in this application can reconstruct the three-dimensional spatiotemporal evolution history of strain inside the simulated specimen of the compressive-torsional salt structure from the early, middle to late stages, providing direct and quantitative experimental evidence for a deeper understanding of the layered differential deformation mechanism and coupling-decoupling relationship of thin interlayered paste salt layers under compressive-torsional action.

[0080] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A simulated specimen of compressive-torsional salt structure capable of recording deformation history, characterized in that, include: The following layers are stacked sequentially from bottom to top: a pre-salt layer (101), a gypsum-salt layer (102), and an over-salt layer (103) simulating a pre-salt sedimentary rock layer (100). The gypsum-salt layer (102) includes a simulated brittle stratum (102a), a simulated weak mudstone layer (102b), and a simulated plastic gypsum-salt rock layer (102c). Several parallel strain sensing layers (200) are respectively located inside the pre-salt layer (101), at the interface between the pre-salt layer (101) and the grease layer (102), at the interface layer inside the grease layer (102), and at the interface between the grease layer (102) and the salt layer (103); The strain sensing layer (200) includes a high light transmittance base layer (201) and photosensitive color-changing units (202) uniformly dispersed in the high light transmittance base layer (201). The photosensitive color-changing unit (202) contains at least two kinds of microcapsules (210) that are sensitive to ultraviolet light of different wavelengths and are internally coated with color-developing labeling core material (212). The color-developing labeling core material (212) is a monochromatic color developer or a single emission spectrum fluorescent agent. The color-developing labeling core material (212) in different kinds of photosensitive color-changing units (202) has different monochromatic color developers or multiple single emission spectrum fluorescent agents. The wall material (211) of the microcapsule (210) has photosensitive softening mechanical properties, maintaining a preset mechanical strength when there is no ultraviolet light of a specific wavelength, and softening after being irradiated with ultraviolet light of a specific wavelength to significantly reduce its mechanical fracture threshold. The strain-sensing layer (200) is made to break when exposed to ultraviolet light of a specific wavelength and when the stress is higher than the breakage threshold, so as to characterize the location of the high-stress region and the time window of high stress by a monochromatic colorimetric agent or a single emission spectrum fluorescent agent after the breakage.

2. The compression-torsion salt structure simulation specimen capable of recording deformation history according to claim 1, characterized in that, The high-transmittance base layer (201) of the strain sensing layer (200) is made of transparent silicone or transparent micro glass beads to form a horizontal light guide channel that can conduct external ultraviolet light beams along the planar direction of the strain sensing layer (200).

3. The compression-torsional salt structure simulation specimen capable of recording deformation history according to claim 1, characterized in that, The photosensitive color-changing unit (202) includes a first microcapsule (202a), a second microcapsule (202b) and a third microcapsule (202c), with corresponding photosensitive trigger wavelengths of 365nm, 385nm and 405nm, respectively, and the color or fluorescence spectrum of the color developer encapsulated inside is independent of each other; When not exposed to light, the mechanical fracture threshold of the wall material (211) of the microcapsule (210) is greater than 0.5 MPa. After being irradiated with ultraviolet light of the corresponding wavelength, the mechanical fracture threshold is reduced to below 0.1 MPa.

4. The compression-torsion salt structure simulation specimen capable of recording deformation history according to claim 1, characterized in that, The pre-salt layer (101) and the super-salt layer (103) are formed by laying dry quartz sand with a particle size of 100-400 μm; the simulated brittle stratum (102a) is formed by laying dry quartz sand with a particle size of 100-400 μm; the simulated weak mudstone layer (102b) is formed by laying micro glass beads with a particle size of 100-400 μm; and the simulated plastic gypsum-salt rock layer (102c) is formed by laying polymeric silicone resin material.

5. A method for testing compressive-torsional salt structures that can record deformation history, characterized in that, Using the compressive-torsional salt structure simulation specimen with recordable deformation history as described in any one of claims 1-4, the steps include: Step S1: Using a layer-by-layer laying process, the lower salt layer (101), the gypsum salt layer (102), and the upper salt layer (103) are laid sequentially from bottom to top. During the laying process, the strain sensing layer (200) is laid at a preset layer position, which includes: the interior of the pre-salt layer (101), the interface between the pre-salt layer (101) and the gypsum layer (102), the interfaces of each sub-layer inside the gypsum layer (102), and the interface between the gypsum layer (102) and the salt superlayer (103). After each layer of strain-sensing layer (200) is laid, the overlying simulated stratum material is laid until the entire simulated sample is completed; Step S2: Place the laid simulated sample between the fixed plate (21) and the push plate (22) of the compression and torsion test device, and push the movable seat (12) through the drive component (30) to apply compression and shear loads to the simulated sample; Step S3: During the continuous application of load, when the displacement reaches the preset threshold, ultraviolet light of the corresponding wavelength is simultaneously irradiated to soften the corresponding type of microcapsule wall material, which then breaks and reveals color when subjected to subsequent deformation and stress. Step S4: After the experiment, the sample material is removed layer by layer from top to bottom. Whenever a strain sensing layer (200) is exposed, a color image or fluorescence image of the strain sensing layer (200) is acquired using an image acquisition device, and the position, color type and color depth of the colored area in each strain sensing layer (200) are recorded. Step S5: Based on the color type of the color markers in the images of different strain sensing layers (200), distinguish the time stage of deformation; based on the color depth or fluorescence intensity of the color markers, semi-quantitatively assess the strain magnitude at that location within that time stage.

6. The method for testing the compressive-torsional salt structure according to claim 5, characterized in that, In step S3, during the application of compressive and torsional loads, ultraviolet light of a specific wavelength is continuously driven and irradiated in stages to activate the corresponding type of microcapsules: First marking stage: When the displacement of the movable seat (12) reaches the preset first displacement threshold, the side of the sample is irradiated with ultraviolet light of the first wavelength corresponding to the height position of each strain sensing layer 200, so that the wall material of the first microcapsule (202a) softens. In the area where the stress in the deformation inside the sample is higher than the rupture threshold after softening, the first microcapsule (202a) ruptures and releases the first color marker. Second marking stage: When the displacement of the movable seat (12) reaches the preset second displacement threshold, the side of the sample is irradiated with ultraviolet light of the second wavelength corresponding to the height position of each strain sensing layer 200, so that the wall material of the second microcapsule (202b) softens; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation, the second microcapsule (202b) ruptures and releases the second color marker. Third marking stage: When the displacement of the movable seat (12) reaches the preset third displacement threshold, the side of the sample is irradiated with ultraviolet light of the third wavelength corresponding to the height position of each strain sensing layer 200, so that the wall material of the third microcapsule (202c) softens; in the area inside the sample where the stress is higher than the rupture threshold after softening during subsequent deformation, the third microcapsule (202c) ruptures and releases the third color marker.

7. The method for testing the compressive-torsional salt structure according to claim 6, characterized in that, The first displacement threshold is 25% to 35% of the total planned displacement, the second displacement threshold is 55% to 65% of the total planned displacement, and the third displacement threshold is 75% to 85% of the total planned displacement.

8. The method for testing the compressive-torsional salt structure according to claim 5, characterized in that, In step S3, ultraviolet light is introduced into the sample from the side along the horizontal cross-section of the strain sensing layer (200); and a high-energy pulsed ultraviolet laser is used for instantaneous irradiation for 1-5 seconds, during which the load driving component of the test device continues to operate continuously.

9. The method for testing the structure of compressive-torsional salts according to claim 5, characterized in that, In step S4, the layer-by-layer peeling is performed by brushing or vacuuming to remove the loose quartz sand and peelable silica gel layer layer by layer from the top surface of the sample.

10. The method for testing the compressive-torsional salt structure according to claim 5, characterized in that, In step S5, deformation history analysis includes RGB channel separation or fluorescence spectrum separation of each strain sensing layer (200) image, and obtaining the relative strain distribution map of each time stage through grayscale analysis.

Images