Experimental test method for simulating temporary plugging fracturing process

Abstract

The embodiment of the invention provides an experimental test method for simulating a temporary plugging fracturing process. The method comprises the following steps: manufacturing a visual multi-crack temporary plugging fracturing simulation sample; loading the visual multi-crack temporary plugging fracturing simulation sample by using a true triaxial large-scale physical simulation experiment device, and simulating a stress environment; simulating a crack expansion process before temporary plugging; the true triaxial large-scale physical simulation experiment device controls a liquid injection pump to inject fracturing fluid into the stainless steel pipe based on the temporary plugging fracturing parameters, and the fracturing fluid applies acting force to the visual multi-crack temporary plugging fracturing simulation sample from the perforation, so that the visual multi-crack temporary plugging fracturing simulation sample forms cracks; simulating a crack expansion process during temporary plugging; temporary plugging particles are pumped into the stainless steel pipe; the temporary plugging particles are configured to be used for temporarily plugging an inlet of the crack; whether temporary plugging is effective or not is judged, and in response to the fact that temporary plugging is effective, the crack expansion process after temporary plugging is simulated; and in response to temporary plugging effectiveness, optimizing temporary plugging fracturing parameters.

Description

Technical Field

[0001] The present invention relates to the technical field of fracturing testing, and in particular to an experimental testing method for simulating a temporary plugging fracturing process. Background Art

[0002] Unconventional oil and gas and hot dry rock reservoirs such as shale oil and gas, tight sandstone oil and gas, and coalbed methane all show extremely low permeability. Businesses must use hydraulic fracturing technology to form hydraulic fractures or even fracture networks around the wellbore, so that a large number of high-permeability channels are formed in the formations around the well to ensure the oil and gas production of a single well. The expansion of hydraulic fractures is a process of seepage-stress-damage coupling. The fracture expansion process will produce stress shadows in the formations around the fractures. The stress shadows between the fractures will limit the expansion of some fractures or even prevent them from fracturing. The main means to solve this phenomenon is temporary plugging fracturing, that is, during the construction process, according to the expansion of the fractures, a fluid containing solid particles (temporary plugging particles) is injected into the well, pumped to reach the fractures with the advantage of expansion and form a temporary plug at the fracture mouth, so that the subsequent fracturing fluid will preferentially enter the fractures that are not cracked or have limited expansion, so that they can resume expansion and ultimately achieve the purpose of balanced transformation. Temporary plugging is a fluid-solid coupling process in the wellbore-fracture linkage space. If the migration of temporary plugging particles in the wellbore, the distribution between fractures and the temporary plugging formation process can be accurately described, the temporary plugging parameters can be accurately designed and optimized, thereby improving the transformation effect.

[0003] Therefore, the present invention provides an experimental testing method for simulating the temporary plugging fracturing process, that is, by making a visualized multi-crack temporary plugging fracturing simulation specimen, restoring the stress environment of the research object under laboratory conditions, and simulating and observing the temporary plugging fracturing construction process through pumping curves, crack expansion, migration of temporary plugging particles in a simulated wellbore, distribution between cracks and temporary plugging formation process, so as to evaluate the effectiveness of temporary plugging and optimize its construction parameters. Summary of the invention

[0004] One or more embodiments of the present specification provide an experimental test method for simulating a temporary plugging fracturing process, characterized in that the method includes: making a visualized multi-fracture temporary plugging fracturing simulation sample; the visualized multi-fracture temporary plugging fracturing simulation sample is configured to simulate a fractured formation; the visualized multi-fracture temporary plugging fracturing simulation sample is transparent; using a true triaxial large-scale physical simulation experimental device to load the visualized multi-fracture temporary plugging fracturing simulation sample to simulate a stress environment; simulating the crack expansion process before temporary plugging; the true triaxial large-scale physical simulation experimental device controls the injection pump to inject fracturing fluid into the stainless steel pipe based on temporary plugging fracturing parameters, and the fracturing fluid applies a force to the visualized multi-fracture temporary plugging fracturing simulation sample from the perforation to form cracks in the visualized multi-fracture temporary plugging fracturing simulation sample; simulating the crack expansion process during temporary plugging; pumping temporary plugging particles into the stainless steel pipe; the temporary plugging particles are configured to temporarily plug the entrance of the crack; judging whether the temporary plugging is effective, and simulating the crack expansion process after the temporary plugging in response to the temporary plugging being effective; optimizing the temporary plugging fracturing parameters in response to the temporary plugging being effective.

[0005] In some embodiments, the preparation of a visualized multi-crack temporary plugging and fracturing simulation sample includes: determining the rock equivalent mechanical characteristics of the casting material; the rock equivalent mechanical characteristics include at least one of Young's modulus, Poisson's ratio, compressive strength, tensile strength, fracture toughness, etc.; arranging the stainless steel pipe in a casting mold; casting the casting material in the casting mold to obtain the visualized multi-crack temporary plugging and fracturing simulation sample; opening at least one light source window on at least one surface of the visualized multi-crack temporary plugging and fracturing simulation sample; opening at least one observation window on at least one surface of the visualized multi-crack temporary plugging and fracturing simulation sample.

[0006] In some embodiments, the use of a true triaxial large-scale physical simulation experimental device to load the visualized multi-crack temporary plugging and fracturing simulation specimen, the simulated stress environment also includes: installing a light source in the light source window, and installing a camera in the observation window; installing the visualized multi-crack temporary plugging and fracturing simulation specimen in the triaxial chamber of the true triaxial large-scale physical simulation experimental device; connecting the stainless steel pipe with the injection pump; using the true triaxial large-scale physical simulation experimental device to control the loading plate to load the visualized multi-crack temporary plugging and fracturing simulation specimen until the stress borne by the visualized multi-crack temporary plugging and fracturing simulation specimen reaches a preset value.

[0007] In some embodiments, the simulation of the crack expansion process before temporary plugging further includes: recording the crack changes before temporary plugging in the visualized multi-crack temporary plugging fracturing simulation sample.

[0008] In some embodiments, the fracture expansion process during the simulation of temporary plugging also includes: determining whether non-equilibrium changes occur in the fractures before temporary plugging; in response to non-equilibrium changes in the fractures before temporary plugging, replacing the fracturing fluid with guar gum while maintaining the injection displacement unchanged, and simultaneously pumping temporary plugging particles into the stainless steel pipe; observing the movement of the temporary plugging particles in the stainless steel pipe and their aggregation at the entrance of the fracture to determine whether temporary plugging is effective.

[0009] In some embodiments, in response to the temporary plugging being effective, simulating the crack expansion process after temporary plugging includes: determining whether non-equilibrium changes occur in the cracks after temporary plugging; in response to equilibrium changes in the cracks after temporary plugging, stopping pumping the temporary plugging particles; and replacing the guar gum with the fracturing fluid while keeping the injection displacement unchanged until at least one of the temporarily plugged cracks expands to the edge of the visualized multi-crack temporary plugging fracturing simulation specimen.

[0010] In some embodiments, the optimization of the temporary plugging fracturing parameters includes: in response to the temporary plugging being invalid, determining whether the temporary plugging meets preset requirements; in response to the temporary plugging not meeting the preset requirements, adjusting the temporary plugging fracturing parameters; based on the adjusted temporary plugging fracturing parameters, continuing to pump the guar gum to determine whether non-equilibrium changes occur in the cracks after temporary plugging; in response to non-equilibrium changes occur in the cracks after temporary plugging, adjusting the temporary plugging material parameters.

[0011] In some embodiments, the temporary plugging material parameter includes at least one of the quantity, size, type, etc. of the temporary plugging material.

[0012] In some embodiments, the determining whether the temporary plugging is effective includes: determining the accumulation of the temporary plugging material at the opening of the crack.

[0013] In some embodiments, the perforations are arranged in a plurality of rows along the axial direction of the stainless steel tube; and the perforations in each row are distributed in a ring shape in the circumferential direction of the stainless steel tube.

[0014] The present invention has the following advantages:

[0015] (1) The present invention uses transparent high-strength PMMA material and cooperates with reasonable light source and camera settings to accurately observe the crack expansion at different stages, the migration of temporary plugging particles in the simulated wellbore, the distribution between cracks and the temporary plugging formation process, etc., under the premise of ensuring that the sample is close to the rock mechanical characteristics of the studied formation, thus overcoming the problem that traditional artificial cement samples or natural samples cannot be accurately observed;

[0016] (2) The transparent observable feature of the present invention, combined with the pumping curve, can completely restore the temporary plugging and fracturing construction process, including the pump pressure changes and crack expansion before, during and after temporary plugging;

[0017] (3) The transparent sample of the present invention can accurately record the crack expansion process by means of a light source + wide-angle camera. Compared with the traditional large-scale physical simulation experiment of fracturing, which requires acoustic emission, optical fiber and other methods (currently the materials cost tens of thousands or even hundreds of thousands of RMB) to restore the dynamic expansion process of the crack, the cost is much lower (the cost of the monitoring and recording materials of the present invention is less than RMB 10,000), which greatly saves experimental expenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein:

[0019] Figure 1 is an exemplary flow chart of an experimental test method for simulating a temporary plugging and fracturing process according to some embodiments of this specification;

[0020] Figure 2 is a schematic structural diagram of a visualized multi-fracture temporary plugging and fracturing simulation specimen according to some embodiments of this specification;

[0021] Figure 3A This is one of the structural schematic diagrams of a crack before temporary plugging shown in some embodiments of this specification;

[0022] Figure 3B This is the second structural schematic diagram of a crack before temporary plugging according to some embodiments of this specification;

[0023] Figure 3C This is a third structural schematic diagram of a crack before temporary plugging according to some embodiments of this specification;

[0024] Figure 4 is a schematic diagram of the structure of a crack during temporary plugging according to some embodiments of this specification;

[0025] Figure 5 It is a schematic diagram of the structure of cracks formed after temporary plugging is effective according to some embodiments of this specification;

[0026] Figure 6 It is a schematic diagram of the structure of cracks formed after temporary plugging fails according to some embodiments of this specification. DETAILED DESCRIPTION

[0027] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0028] Flowcharts are used in this specification to illustrate the operations performed by the system according to the embodiments of this specification. It should be understood that the preceding or following operations are not necessarily performed precisely in order. Instead, the steps may be processed in reverse order or simultaneously. At the same time, other operations may also be added to these processes, or one or more operations may be removed from these processes.

[0029] Figure 1 is an exemplary flow chart of an experimental test method for simulating a temporary plugging and fracturing process according to some embodiments of the present specification. Figure 2 Schematic diagram of the structure of a visualized multi-fracture temporary plugging and fracturing simulation sample according to some embodiments of this specification. Figure 1 As shown, process 100 includes the following steps.

[0030] Step 110, making a visualized multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, step 110 may be performed by an operator.

[0031] The visualized multi-fracture temporary plugging and fracturing simulation specimen 200 refers to a specimen used for experimental testing of a simulated temporary plugging and fracturing process.

[0032] In some embodiments, the visualized multi-fracture temporary plugging and fracturing simulation sample 200 can be configured to simulate a fracturing formation. For example, the mechanical characteristics of the visualized multi-fracture temporary plugging and fracturing simulation sample 200 can be the same as the mechanical characteristics of the formation. The mechanical characteristics can include at least one of Young's modulus, Poisson's ratio, compressive strength, tensile strength, fracture toughness, etc.

[0033] In some embodiments, the visualized multiple fractures temporary plugging and fracturing simulation sample 200 is transparent, so that the inside of the visualized multiple fractures temporary plugging and fracturing simulation sample 200 can be observed from the outside. In some embodiments, the visualized multiple fractures temporary plugging and fracturing simulation sample 200 can be made of a transparent material, such as polymethyl methacrylate (PMMA).

[0034] In some embodiments, the visualized multi-fracture temporary plugging fracturing simulation specimen 200 may include a variety of shapes. For example, at least one of a cylindrical shape, a prism shape, etc. In some embodiments, as Figure 2As shown, the visualized multi-fracture temporary plugging and fracturing simulation sample 200 may be in the shape of a cube. In some embodiments, the side length of the visualized multi-fracture temporary plugging and fracturing simulation sample 200 may range from 300 to 500 mm. For example, 300 mm, 400 mm, 500 mm, etc. In some embodiments, the side length of the visualized multi-fracture temporary plugging and fracturing simulation sample 200 may also be other values.

[0035] In some embodiments, Figure 2 As shown, a stainless steel pipe 300 can be set in the visualized multi-fracture temporary plugging fracturing simulation sample 200. The stainless steel pipe 300 can be used to simulate a wellbore buried in a formation. In some embodiments, at least a portion of the stainless steel pipe 300 can extend into the visualized multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, when the visualized multi-fracture temporary plugging fracturing simulation sample 200 is in a cubic shape, the stainless steel pipe 300 can be perpendicular to one of the surfaces of the visualized multi-fracture temporary plugging fracturing simulation sample 200. For example, it is perpendicular to the upper surface of the visualized multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, the axis of the stainless steel pipe 300 can be collinear with the center of the visualized multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, the bottom of the stainless steel pipe 300 is spaced from the lower surface of the visualized multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, the spacing between the bottom of the stainless steel pipe 300 and the lower surface support of the visualized multi-fracture temporary plugging fracturing simulation sample 200 can range from 45-55 mm. For example, 45 mm, 50 mm, 55 mm, etc. In some embodiments, the distance between the bottom of the stainless steel pipe 300 and the lower surface support of the visualized multi-crack temporary plugging and fracturing simulation specimen 200 may also range from other values.

[0036] In some embodiments, at least a portion of the stainless steel pipe 300 may extend out of the visualization multi-fracture temporary plugging and fracturing simulation specimen 200 .

[0037] In some embodiments, the stainless steel tube 300 is provided with a plurality of perforations (not shown in the figure). The perforations can connect the inner and outer sides of the stainless steel tube 300.

[0038] In some embodiments, the perforations may be arranged in multiple rows along the axis of the stainless steel tube 300. In some embodiments, each row of perforations may be distributed in a circular shape around the axis of the stainless steel tube 300 in the circumference of the stainless steel tube 300. In some embodiments, each row of perforations may be evenly distributed at equal intervals.

[0039] In some embodiments, making a visualized multi-fracture temporary plugging and fracturing simulation sample 200 may include determining the mechanical characteristics of a casting material, setting a stainless steel pipe 200 in a casting mold, casting the casting material in the casting mold, and obtaining a visualized multi-fracture temporary plugging and fracturing simulation sample 200.

[0040] The casting material refers to the material used to cast the visualized multi-crack temporary plugging and fracturing simulation sample 200, for example, polymethyl methacrylate (PMMA) and the like.

[0041] In some embodiments, an operator may cast a standard specimen based on the casting material.

[0042] A standard sample refers to a sample used to verify mechanical characteristics. In some embodiments, after the operator casts the standard sample, the operator can test the mechanical characteristics of the standard sample. In some embodiments, the operator can change at least one of the formula and ratio of the casting material, thereby changing the mechanical characteristics corresponding to the standard sample. In some embodiments, the operator can make the mechanical characteristics of the cast sample the same as the mechanical characteristics of the simulated fracturing formation based on at least one of the formula and ratio of the confirmed casting material. In some embodiments, the operator can cast based on the confirmed casting material, and by casting the hot-melt casting material in the casting mold, a visualized multi-crack temporary plugging fracturing simulation sample 200 can be obtained after the casting material cools. In some embodiments, during casting, the operator can install the stainless steel pipe 300 at a preset position in the casting mold, and cast the stainless steel pipe 300 in the visualized multi-crack temporary plugging fracturing simulation sample 200. The preset position can be set according to actual needs.

[0043] In some embodiments, at least one surface of the visualized multi-fracture temporary plugging and fracturing simulation specimen 200 is provided with at least one light source window (not shown in the figure).

[0044] The light source window refers to a groove-shaped structure that can be used to install a light source. In some embodiments, the light source window can be formed in a variety of ways. For example, at least one of forming using a casting mold, machining, etc.

[0045] In some embodiments, a light source window may be provided on the upper surface of the visualized multiple fractures temporary plugging and fracturing simulation sample 200. In some embodiments, a plurality of light source windows may be provided on the upper surface of the visualized multiple fractures temporary plugging and fracturing simulation sample 200. For example, three, four, or other numbers. The plurality of light source windows may be distributed in an array on the upper surface of the visualized multiple fractures temporary plugging and fracturing simulation sample 200.

[0046] In some embodiments, at least one observation window (not shown in the figure) is opened on at least one surface of the visualized multi-fracture temporary plugging and fracturing simulation specimen 200 .

[0047] The observation window refers to a window that can be used to observe the interior of the visualized multi-fracture temporary plugging and fracturing simulation specimen 200. In some embodiments, the observation window can be formed in a variety of ways, such as by using at least one of a casting mold, machining, and the like.

[0048] In some embodiments, an observation window may be provided on a side of the visualization multi-fracture temporary plugging and fracturing simulation specimen 200 .

[0049] Step 120, using a true triaxial large-scale physical simulation experimental device to load the visualized multi-fracture temporary plugging and fracturing simulation specimen to simulate a stress environment. In some embodiments, step 120 can be performed by an operator and a true triaxial large-scale physical simulation experimental device.

[0050] The true triaxial large-scale physical simulation experimental device refers to a device capable of conducting experiments simulating the temporary plugging and fracturing process. In some embodiments, the true triaxial large-scale physical simulation experimental device may include a triaxial chamber, a liquid injection pump, a loading plate, a controller, and the like.

[0051] The triaxial chamber may be used to install the visualized multi-fracture temporary plugging and fracturing simulation specimen 200. In some embodiments, the triaxial chamber may include at least one working plane for installing the visualized multi-fracture temporary plugging and fracturing simulation specimen 200.

[0052] The injection pump can be used to pump liquids, for example, to pump fracturing fluids, guar gum, etc. In some embodiments, the injection pump can be connected to the stainless steel pipe 300 and pump liquids into the stainless steel pipe 300 .

[0053] The loading plate can be used to apply pressure to the visualized multi-fracture temporary plugging and fracturing simulation sample 200, thereby simulating a stress environment. In some embodiments, the loading plate can apply pressure to the visualized multi-fracture temporary plugging and fracturing simulation sample 200 from multiple directions. For example, the loading plate can apply pressure to the visualized multi-fracture temporary plugging and fracturing simulation sample 200 from three directions. One direction is perpendicular to the upper surface of the visualized multi-fracture temporary plugging and fracturing simulation sample 200, and the other two directions are respectively perpendicular to two adjacent measurements of the visualized multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, the three directions can be perpendicular to each other.

[0054] The controller can collect, analyze, process, and store data, and can generate control instructions, which can be used to control other mechanisms to perform corresponding actions or functions. In some embodiments, the injection pump and the loading plate can be respectively connected to the controller for communication. The controller can control the injection pump and the loading plate respectively.

[0055] In some embodiments, the true triaxial large-scale physical simulation experiment device may further include a display. The display may be communicatively connected to the controller. The controller may control the display to display data. The data may include at least one of text, images, animations, etc.

[0056] In some embodiments, the operator can install a light source 400 in the light source window. The light source 400 can emit light to the interior of the visualized multiple fractures temporary plugging and fracturing simulation sample 200, thereby increasing the brightness of the interior of the visualized multiple fractures temporary plugging and fracturing simulation sample 200 and making the interior of the visualized multiple fractures temporary plugging and fracturing simulation sample 200 easier to view.

[0057] In some embodiments, the light source 400 can be at least one of a point light source, a line light source, a surface light source, etc. In some embodiments, the light source 400 can be adapted to the shape of the light source window. In some embodiments, the light source 400 can be a surface light source of 150mm* width 150mm* thickness 10mm. In some embodiments, the light source 400 can be connected to the controller for communication. The controller can control the light source 400 to start, turn off, adjust the brightness, etc. In some embodiments, the brightness of the light source 400 can be adjusted in a range of 0-200 lumens.

[0058] In some embodiments, the light source 400 and the light source window may be connected in a variety of ways, such as at least one of bonding and clamping.

[0059] In some embodiments, the operator can install a camera 500 in the observation window. The camera 500 can be used to shoot the interior and changes of the visualized multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, two cameras 500 can be set on one side of the visualized multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, the camera 500 can be a wireless wide-angle camera with a viewing angle of 155° and automatic distortion correction.

[0060] In some embodiments, the camera 500 and the observation window may be connected in a variety of ways, such as at least one of bonding and clamping.

[0061] In some embodiments, the camera 500 may be connected to the controller for communication, and the controller may control the camera 500 to start, shut down, and shoot the internal conditions of the visualized multi-fracture temporary plugging and fracturing simulation specimen 200. In some embodiments, the data captured by the camera 500 may be transmitted to the controller.

[0062] In some embodiments, the brightness of the light emitted by the light source 400 can be adjusted based on the clarity of the picture captured by the camera 500. For example, when the clarity of the picture captured by the camera 500 is poor, the brightness of the light emitted by the light source 400 can be increased.

[0063] In some embodiments, the operator can install the visualized multi-crack temporary plugging fracturing simulation specimen 200 in the triaxial chamber of the true triaxial large-scale physical simulation experimental device. For example, it can be installed on the working plane in the triaxial chamber. In some embodiments, a positioning structure and a fixing structure can be set on the working plane. Among them, the positioning structure can include at least one of a positioning block, a positioning plate, a positioning pin, etc. The fixing structure can include at least one of a chuck, a manipulator, etc.

[0064] In some embodiments, the operator can connect the stainless steel pipe 300 to the injection pump. For example, the operator can connect the stainless steel pipe 300 to the injection pump through a pipeline. The controller can control the injection pump to pump liquid into the stainless steel pipe 300 through the pipeline.

[0065] In some embodiments, the true triaxial large-scale physical simulation experimental device controls the loading plate to load the visualized multi-crack temporary plugging fracturing simulation sample 200. For example, the controller can control the loading plate to move toward the visualized multi-crack temporary plugging fracturing simulation sample 200 until it contacts. In some embodiments, after the loading plate contacts the visualized multi-crack temporary plugging fracturing simulation sample 200, the controller can control the loading plate to continue to move in the direction close to the visualized multi-crack temporary plugging fracturing simulation sample 200. In some embodiments, the controller can control the loading plate to maintain the relative position of the loading plate and the visualized multi-crack temporary plugging fracturing simulation sample 200. In some embodiments, the controller can control the loading plate to load the visualized multi-crack temporary plugging fracturing simulation sample 200 with a pressure of 1-2Mpa until the pressure feedback of the loading plate is stable. Pressure feedback refers to the pressure detected by the loading plate after the loading plate loads the visualized multi-crack temporary plugging fracturing simulation sample 200. In some embodiments, a pressure sensor for detecting pressure can be provided on the loading plate. The pressure sensor can be connected to the controller for communication. The controller can receive data detected by the pressure sensor. In some embodiments, the pressure feedback stabilization controller of the loading plate can control the loading plate to continue applying pressure to the visualized multi-fracture temporary plugging fracturing simulation specimen 200 until the pressure reaches a preset value. The preset value can be set according to actual needs.

[0066] Step 130, simulating the crack expansion process before temporary plugging. In some embodiments, step 130 can be performed by a true triaxial large-scale physical simulation experimental device.

[0067] In some embodiments, the true triaxial large-scale physical simulation experimental device can control the injection pump to inject fracturing fluid into the stainless steel pipe 300 based on the temporary plugging fracturing parameters. The fracturing fluid can apply force to the visualized multi-fracture temporary plugging fracturing simulation sample 200 from the perforations, so that the visualized multi-fracture temporary plugging fracturing simulation sample forms cracks 600. In some embodiments, the fracturing fluid leaving the stainless steel pipe 300 from the perforations in the same row can form cracks 600 in the same plane. In some embodiments, the perforations in the same row can form circular or quasi-circular cracks.

[0068] Temporary plugging fracturing parameters refer to parameters related to the fracturing fluid. In some embodiments, the temporary plugging fracturing parameters may include at least one of the material, concentration, flow rate, hydraulic pressure, flow rate, etc. of the fracturing fluid. In some embodiments, the temporary plugging fracturing parameters can be set according to actual needs.

[0069] Temporary plugging refers to temporarily plugging at least part of the perforation, thereby changing the forming effect of the fracture 600. For example, at least one of the size and forming speed of the fracture 600 is changed.

[0070] In some embodiments, the controller of the true triaxial large-scale physical simulation experimental device can control the camera 500 to record the changes of the cracks 600 before temporary plugging in the visualized multi-crack temporary plugging fracturing simulation sample 200. For example, the formation process of the cracks 600 can be recorded. Before temporary plugging refers to the time period before the perforation is temporarily plugged.

[0071] Figure 3A This is one of the structural schematic diagrams of a crack before temporary plugging shown in some embodiments of this specification. Figure 3B This is the second structural schematic diagram of the crack before temporary plugging shown in some embodiments of this specification. Figure 3C This is the third structural schematic diagram of a crack before temporary plugging shown in some embodiments of the present specification.

[0072] Step 140, simulating the crack expansion process during temporary plugging. In some embodiments, step 140 can be performed by a true triaxial large-scale physical simulation experimental device.

[0073] Temporary plugging time refers to the time period during which the perforations are temporarily plugged.

[0074] In some embodiments, the controller may control the injection pump to pump temporary plugging particles 700 into the stainless steel pipe 300 .

[0075] The temporary plugging particles 700 refer to granular solid matter. In some embodiments, the temporary plugging particles 700 may be plastic particles. In some embodiments, the temporary plugging particles 700 may be configured to temporarily plug the entrance of the fracture 600, that is, temporarily plugging the perforation.

[0076] In some embodiments, the operator can determine whether the crack 600 before temporary plugging has undergone non-balanced changes. For example, the operator can determine whether the crack 600 has undergone non-balanced changes based on the changes in the crack 600 captured by the camera 500 before temporary plugging.

[0077] The non-balanced change refers to abnormal formation of the crack 600. In some embodiments, the non-balanced change may include at least one of abnormal crack initiation, unbalanced expansion, etc. The non-balanced change may form a non-balanced crack 610.

[0078] Failure to initiate fracturing normally means that when the fracturing fluid applies pressure from the perforation to the visualized multi-fracture temporary plugging fracturing simulation specimen 200, the radius of the fracture 600 formed is less than or equal to the first threshold value. The first threshold value may include multiple types. For example, at least one of 0, one fifth of the predicted radius, one tenth of the predicted radius, etc. The predicted radius refers to the predicted radius of the fracture 600 formed. In some embodiments, the predicted radius may be a preset value. Failure to initiate fracturing normally may form an abnormal fracture 620.

[0079] Unbalanced expansion means that when the fracturing fluid applies pressure from the perforation to the visualized multi-fracture temporary plugging fracturing simulation sample 200, the radius of the fracture 600 formed is less than or equal to the second threshold value. The first threshold value may include multiple values. For example, at least one of four-fifths of the measured radius and four-fifths of the actual maximum radius. The actual maximum radius refers to the radius corresponding to the fracture 600 with the largest radius actually generated in the current experiment.

[0080] In some embodiments, in response to the non-equilibrium change of the fracture 600 before temporary plugging, the controller replaces the fracturing fluid with guar gum while keeping the injection displacement unchanged, and simultaneously pumps temporary plugging particles 700 into the stainless steel pipe 300 .

[0081] In some embodiments, the diameter of the temporary plugging particles 700 may be less than or equal to 40 mesh. In some embodiments, the total apparent volume of the temporary plugging particles 700 is no greater than 1 / 100 of the total volume of the liquid pumped into the stainless steel pipe 300. The total apparent volume refers to the volume occupied by the temporary plugging particles 700 in the liquid pumped into the stainless steel pipe 300.

[0082] In some embodiments, the controller of the true triaxial large-scale physical simulation experimental device can control the camera 500 to record and visualize the changes in the cracks during temporary plugging in the multi-crack temporary plugging fracturing simulation specimen 200 .

[0083] Figure 4 It is a schematic diagram of the structure of a crack during temporary plugging according to some embodiments of the present specification.

[0084] Step 150, determining whether the temporary blocking is effective. In some embodiments, step 150 may be performed by an operator and / or a controller.

[0085] In some embodiments, Figure 4 As shown, the operator can observe the movement of the temporary plugging particles 700 in the stainless steel pipe 300 and the aggregation at the entrance of the crack to determine whether the temporary plugging is effective. For example, the operator can observe the movement of the temporary plugging particles 700 in the stainless steel pipe 300 and the aggregation at the entrance of different cracks, and determine whether the temporary plugging is effective in combination with the change of the pump pressure of the injection pump or the hydraulic pressure in the stainless steel pipe 300 over time. In some embodiments, when the temporary plugging particles 700 flow toward the perforations corresponding to the non-equilibrium-changing cracks 600 and gather at the corresponding perforations, and the pump pressure of the injection pump or the hydraulic pressure in the stainless steel pipe 300 continues to rise, the operator and / or the controller can determine that the temporary plugging is effective.

[0086] Figure 5 It is a schematic diagram of the structure of cracks formed after temporary plugging is effective according to some embodiments of this specification.

[0087] Step 161, in response to the temporary plugging being effective, simulating the expansion process of the crack 600 after the temporary plugging. In some embodiments, step 161 may be performed by an operator and / or a controller.

[0088] In some embodiments, the operator and / or controller determines whether the crack 600 after temporary plugging has undergone non-balanced changes. In some embodiments, the operator and / or controller can determine whether the crack 600 after temporary plugging has undergone non-balanced changes based on the video captured by the camera 500. For example, observe whether the crack 600 determined to have undergone non-balanced changes before temporary plugging has undergone changes again.

[0089] In some embodiments, the operator and / or the controller stops pumping the temporary plugging particles 700 in response to a balance change in the temporarily plugged fracture 600 .

[0090] The occurrence of balanced change means that the crack 600 that was determined to be unbalanced before temporary plugging forms a new crack 600 after temporary plugging is effective, and the radius of the new crack 600 is greater than or equal to the second threshold. For more information about the second threshold, please refer to the relevant description of step 140.

[0091] In some embodiments, the operator and / or controller can replace guar gum with fracturing fluid while keeping the injection displacement unchanged, and control the injection pump to continuously pump fracturing fluid into the stainless steel pipe 300 until at least one temporarily plugged fracture 600 extends to the edge of the visualized multi-fracture temporary plugging fracturing simulation specimen 200. In some embodiments, the operator and / or controller can control the injection pump to stop pumping fracturing fluid.

[0092] Figure 6 It is a schematic diagram of the structure of cracks formed after temporary plugging fails according to some embodiments of this specification.

[0093] Step 162, in response to the temporary plugging being ineffective, optimizing the temporary plugging fracturing parameters. In some embodiments, step 162 may be performed by an operator and / or a controller.

[0094] Temporary plugging ineffectiveness means that the temporary plugging particles 700 do not accumulate at the perforations, or the pump pressure of the injection pump or the hydraulic pressure in the stainless steel pipe 300 does not change over time.

[0095] Optimizing temporary plugging and fracturing parameters refers to adjusting at least one of the temporary plugging and fracturing parameters, wherein the adjustment may include at least one of adding, deleting, increasing, decreasing, and the like.

[0096] For more information about temporary plugging and fracturing parameters, please refer to the relevant description of step 130.

[0097] In some embodiments, when all fractures 600 are not uniformly extended, the operator and / or the controller may also optimize the temporary plugging and fracturing parameters.

[0098] In some embodiments, when temporary plugging is ineffective, the operator and / or controller can increase or decrease the flow rate of the injection pump to pump the fracturing fluid, so that the temporary plugging particles 700 form an effective accumulation at the perforation and the pump pressure of the injection pump or the hydraulic pressure in the stainless steel pipe 300 increases significantly.

[0099] In some embodiments, when all fractures 600 are not expanding evenly, the operator and / or the controller may control the pumping time to be advanced so that the temporarily blocked fractures can achieve even expansion.

[0100] The pumping time refers to the time point when the temporary blocking particles 700 are pumped in. The pumping time may be a time point after step 120 or step 130 continues for a preset time.

[0101] Just as an example, after step 130 lasts for 10 minutes, the true triaxial large-scale physical simulation experimental device performs the crack expansion process during the simulation of temporary plugging. The time point after step 130 lasts for 10 minutes is the pumping time. The operator and / or the controller can control the pumping time to be advanced, for example, 2 minutes in advance. That is, after step 130 lasts for 8 minutes, the true triaxial large-scale physical simulation experimental device performs the crack expansion process during the simulation of temporary plugging, and the controller can control the injection pump to pump the temporary plugging particles 700 into the stainless steel pipe 300. In this way, the length of time during temporary plugging can be extended, making it easier for the temporary plugging particles 700 to temporarily plug the entrance of the crack 600.

[0102] In some embodiments, based on the adjusted temporary plugging and fracturing parameters, guar gum is continuously pumped in to determine whether non-equilibrium changes occur in the fracture 600 after the temporary plugging and fracturing parameters are adjusted.

[0103] In some embodiments, in response to a non-equilibrium change in the temporarily plugged fracture 600 , the temporary plugging material parameters are adjusted.

[0104] The temporary plugging material parameter refers to a parameter related to the temporary plugging particles 700. In some embodiments, the temporary plugging material parameter includes at least one of the quantity, size, type, and hardness of the temporary plugging material.

[0105] In some embodiments, adjusting the temporary plugging material parameters may include at least one of selecting a temporary plugging material with higher or lower stiffness, increasing or decreasing the number of temporary plugging particles 700, increasing or decreasing the size of temporary plugging particles 700, introducing flexible temporary plugging materials such as knots, etc.

[0106] The experimental test method for simulating the temporary plugging fracturing process uses transparent high-strength PMMA materials and reasonable light sources and camera settings to ensure that the sample is close to the rock mechanical characteristics of the studied formation, and accurately observe the crack expansion at different stages, the migration of temporary plugging particles 700 in the stainless steel pipe of the simulated wellbore, the distribution between cracks, and the temporary plugging formation process. In conjunction with the pumping curve, the complete process of temporary plugging fracturing construction, including before, during, and after temporary plugging, can be fully restored. At the same time, due to the use of transparent samples with low-cost and easily available light sources and wide-angle camera monitoring, under the premise of accurately recording the crack expansion process, the overall experimental expenses save more than tens of thousands of yuan, which is conducive to promotion and application in different institutions, and thus better serve the design of temporary plugging fracturing construction parameters.

[0107] The basic concepts have been described above. Obviously, for those skilled in the art, the above detailed disclosure is only for example and does not constitute a limitation of this specification. Although not explicitly stated here, those skilled in the art may make various modifications, improvements and corrections to this specification. Such modifications, improvements and corrections are suggested in this specification, so such modifications, improvements and corrections still belong to the spirit and scope of the exemplary embodiments of this specification.

[0108] At the same time, this specification uses specific words to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" refer to a certain feature, structure or characteristic related to at least one embodiment of this specification. Therefore, it should be emphasized and noted that "one embodiment" or "an embodiment" or "an alternative embodiment" mentioned twice or more in different positions in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures or characteristics in one or more embodiments of this specification can be appropriately combined. Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. An experimental test method for simulating a temporary plugging and fracturing process, characterized in that: include: Make a visualized multi-fracture temporary plugging and fracturing simulation specimen; The visualized multi-fracture temporary plugging fracturing simulation sample is configured to simulate a fractured formation; The visualized multi-crack temporary plugging and fracturing simulation sample is transparent; Using a true triaxial large-scale physical simulation experimental device to load the visualized multi-crack temporary plugging and fracturing simulation specimen to simulate a stress environment; Simulate the crack expansion process before temporary plugging; The true triaxial large-scale physical simulation experimental device controls the injection pump to inject fracturing fluid into the stainless steel pipe based on the temporary plugging fracturing parameters, and the fracturing fluid applies force to the visualized multi-fracture temporary plugging fracturing simulation sample from the perforation, so that cracks are formed in the visualized multi-fracture temporary plugging fracturing simulation sample; and the crack expansion process during temporary plugging is simulated; Pumping temporary plugging particles into the stainless steel pipe; The temporary plugging particles are configured to temporarily plug the entrance of the crack; Determine whether temporary blocking is effective, and In response to the temporary plugging being effective, simulating a crack expansion process after the temporary plugging; In response to the temporary plugging being ineffective, optimizing the temporary plugging fracturing parameters.

2. The experimental test method for simulating temporary plugging and fracturing process according to claim 1, characterized in that: The method of preparing a visualized multi-crack temporary plugging fracturing simulation sample comprises: Determine the rock equivalent mechanical characteristics of the cast material; The rock equivalent mechanical characteristics include at least one of Young's modulus, Poisson's ratio, compressive strength, tensile strength, fracture toughness, etc.; Arranging the stainless steel pipe in a casting mold; The casting material is cast in the casting mold to obtain the visualized multi-crack temporary plugging and fracturing simulation sample.

3. The experimental test method for simulating temporary plugging and fracturing process according to claim 1, characterized in that: The use of a true triaxial large-scale physical simulation experimental device to load the visualized multi-crack temporary plugging and fracturing simulation sample, and the simulated stress environment also includes: A light source is installed in the light source window, and a camera is installed in the observation window; The visualized multi-crack temporary plugging and fracturing simulation specimen is installed in the triaxial chamber of the true triaxial large-scale physical simulation experimental device; Connecting the stainless steel pipe to the injection pump; The true triaxial large-scale physical simulation experimental device is used to control the loading plate to load the visualized multi-crack temporary plugging and fracturing simulation sample until the stress borne by the visualized multi-crack temporary plugging and fracturing simulation sample reaches a preset value.

4. The experimental test method for simulating temporary plugging and fracturing process according to claim 1, characterized in that: The simulation of the crack expansion process before temporary plugging also includes: Record the changes of the cracks before temporary plugging in the visualized multi-crack temporary plugging fracturing simulation sample.

5. The experimental test method for simulating temporary plugging and fracturing process according to claim 4, characterized in that: The crack expansion process during the simulation of temporary plugging also includes: Determining whether the cracks before temporary plugging have undergone non-equilibrium changes; In response to the occurrence of non-equilibrium changes in the cracks before temporary plugging, the fracturing fluid is replaced with guar gum while maintaining the injection displacement unchanged, and temporary plugging particles are pumped into the stainless steel pipe; The movement of the temporary plugging particles in the stainless steel pipe and the aggregation at the entrance of the crack are observed to determine whether the temporary plugging is effective.

6. The experimental test method for simulating temporary plugging and fracturing process according to claim 5, characterized in that: In response to the temporary plugging being effective, simulating the crack expansion process after the temporary plugging comprises: Determine whether the cracks after temporary plugging have undergone non-equilibrium changes; In response to the occurrence of an equilibrium change in the temporarily plugged fracture, stopping pumping the temporarily plugging particles; Under the premise of keeping the injection displacement unchanged, the guar gum is replaced with the fracturing fluid until at least one of the temporarily plugged fractures extends to the edge of the visualized multi-fracture temporary plugging fracturing simulation specimen.

7. The experimental test method for simulating temporary plugging and fracturing process according to claim 5, characterized in that: In response to the temporary plugging being ineffective, optimizing the temporary plugging fracturing parameters includes: adjusting the temporary plugging and fracturing parameters; Based on the adjusted temporary plugging fracturing parameters, continue to pump the guar gum to determine whether the cracks after temporary plugging have non-equilibrium changes; In response to non-equilibrium changes in the cracks after temporary plugging, the parameters of the temporary plugging material are adjusted.

8. The experimental test method for simulating temporary plugging and fracturing process according to claim 7, characterized in that: The temporary plugging material parameters include at least one of the quantity, size, type, etc. of the temporary plugging material.

9. The experimental test method for simulating temporary plugging and fracturing process according to claim 1, characterized in that: At least one surface of the visualized multi-crack temporary plugging and fracturing simulation sample is provided with at least one light source window; At least one observation window is provided on at least one surface of the visualized multi-crack temporary plugging and fracturing simulation sample.

10. The experimental test method for simulating temporary plugging and fracturing process according to claim 1, characterized in that: The perforations are arranged in multiple rows along the axial direction of the stainless steel tube; Each row of perforations is distributed in a ring shape around the circumference of the stainless steel pipe.

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