An experimental testing method for simulating a temporary plugging fracturing process

Abstract

The embodiment of the specification provides an experimental test method for simulating a temporary plugging fracturing process, which comprises: preparing a visual multi-fracture temporary plugging fracturing simulation sample; loading the visual multi-fracture temporary plugging fracturing simulation sample using a true triaxial large physical simulation experiment device to simulate a stress environment; simulating a crack propagation process before temporary plugging; the true triaxial large physical simulation experiment device controls a liquid injection pump to inject fracturing fluid into a stainless steel pipe based on temporary plugging fracturing parameters, the fracturing fluid exerts force on the visual multi-fracture temporary plugging fracturing simulation sample from a perforating hole, and the visual multi-fracture temporary plugging fracturing simulation sample forms a crack; simulating a crack propagation process during temporary plugging; pumping temporary plugging particles into the stainless steel pipe; the temporary plugging particles are configured to temporarily plug an inlet of the crack; determining whether the temporary plugging is effective, and in response to the temporary plugging being effective, simulating a crack propagation process after temporary plugging; and in response to the temporary plugging being effective, optimizing the temporary plugging fracturing parameters.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of fracturing test, in particular to an experimental test method for simulating temporary plugging fracturing process. BACKGROUND

[0002] Unconventional oil and gas such as shale oil and gas, tight sandstone oil and gas, coal bed methane and hot dry rock reservoirs all have very low seepage rate. Hydraulic fracturing technology must be used to form hydraulic fractures or even fracture networks around the wellbore to form a large number of high-permeability channels in the surrounding formation and ensure single-well oil and gas production. Hydraulic fracture propagation is a process of seepage-stress-damage coupling. The fracture propagation process will generate stress shadow around the fracture. The stress shadow between fractures will limit the expansion of some fractures and even prevent them from cracking. The main means to solve this phenomenon is temporary plugging fracturing, that is, during the construction process, according to the fracture propagation situation, a fluid containing solid particles (temporary plugging particles) is injected into the well, which is pumped to reach the preferentially expanding fracture and form temporary plugging at the fracture mouth, so that the subsequent fracturing fluid preferentially enters the unfractured or limitedly expanded fractures, restores the expansion of the fractures, and finally achieves the purpose of balanced reconstruction. Temporary plugging is a fluid-structure 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 design and optimization of temporary plugging parameters can be accurately realized, and the reconstruction effect can be improved.

[0003] Therefore, an experimental test method for simulating temporary plugging fracturing process is invented, that is, by making a visual multi-fracture temporary plugging fracturing simulation sample, the stress environment of the research object is restored under laboratory conditions, and the temporary plugging fracturing construction process is simulated and observed through pump injection curve, fracture propagation, migration of temporary plugging particles in the simulated wellbore, distribution between fractures and temporary plugging formation process, etc. The effectiveness of temporary plugging is evaluated and its construction parameters are optimized. SUMMARY

[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 comprises: making a visual multi-fracture temporary plugging fracturing simulation sample; the visual multi-fracture temporary plugging fracturing simulation sample is configured to simulate a fractured formation; the visual multi-fracture temporary plugging fracturing simulation sample is transparent; loading the visual multi-fracture temporary plugging fracturing simulation sample using a true triaxial large-scale physical simulation experimental device to simulate a stress environment; simulating a crack propagation process before temporary plugging; the true triaxial large-scale physical simulation experimental device controls a liquid injection pump to inject fracturing fluid into the stainless steel pipe based on temporary plugging fracturing parameters, the fracturing fluid exerts force on the visual multi-fracture temporary plugging fracturing simulation sample from the perforation to make the visual multi-fracture temporary plugging fracturing simulation sample form a crack; simulating a crack propagation process during temporary plugging; pumping temporary plugging particles into the stainless steel pipe; the temporary plugging particles are configured to temporarily plug the inlet of the crack; determining whether the temporary plugging is effective, and in response to the temporary plugging being effective, simulating a crack propagation process after temporary plugging; in response to the temporary plugging being effective, optimizing the temporary plugging fracturing parameters.

[0005] In some embodiments, the making of the visual multi-fracture temporary plugging fracturing simulation sample comprises: determining rock equivalent mechanical properties of the casting material; the rock equivalent mechanical properties comprise 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 visual multi-fracture temporary plugging fracturing simulation sample; opening at least one light source window on at least one surface of the visual multi-fracture temporary plugging fracturing simulation sample; opening at least one observation window on at least one surface of the visual multi-fracture temporary plugging fracturing simulation sample.

[0006] In some embodiments, the loading of the visual multi-fracture temporary plugging fracturing simulation sample using a true triaxial large-scale physical simulation experimental device to simulate a stress environment further comprises: installing a light source in the light source window and a camera in the observation window; installing the visual multi-fracture temporary plugging fracturing simulation sample in a triaxial chamber of the true triaxial large-scale physical simulation experimental device; connecting the stainless steel pipe and the liquid injection pump; using the true triaxial large-scale physical simulation experimental device to control a loading plate to load the visual multi-fracture temporary plugging fracturing simulation sample until the stress borne by the visual multi-fracture temporary plugging fracturing simulation sample reaches a preset value.

[0007] In some embodiments, the simulating of the crack propagation process before temporary plugging further comprises: recording the crack change before temporary plugging in the visual multi-fracture temporary plugging fracturing simulation sample.

[0008] In some embodiments, the simulating the fracture propagation process during the temporary plugging further comprises: judging whether the fracture before the temporary plugging has an uneven change; in response to the fracture before the temporary plugging having an uneven change, replacing the fracturing fluid with the guanidium gum while pumping the temporary plugging particles into the stainless steel tube under the condition that the injection and discharge rate remains unchanged; observing the movement of the temporary plugging particles in the stainless steel tube and the accumulation of the temporary plugging particles at the entrance of the fracture, and judging whether the temporary plugging is effective.

[0009] In some embodiments, the simulating the fracture propagation process after the temporary plugging in response to the temporary plugging being effective comprises: judging whether the fracture after the temporary plugging has an uneven change; in response to the fracture after the temporary plugging having an even change, stopping pumping the temporary plugging particles; replacing the guanidium gum with the fracturing fluid under the condition that the injection and discharge rate remains unchanged until at least one of the fractures after the temporary plugging extends to the edge of the visualized multi-fracture temporary plugging and fracturing simulation sample.

[0010] In some embodiments, the optimizing the temporary plugging and fracturing parameters comprises: in response to the temporary plugging being ineffective, judging whether the temporary plugging meets preset requirements; in response to the temporary plugging not meeting the preset requirements, adjusting the temporary plugging and fracturing parameters; based on the adjusted temporary plugging and fracturing parameters, continuing to pump the guanidium gum, judging whether the fracture after the temporary plugging has an uneven change; in response to the fracture after the temporary plugging having an uneven change, adjusting the temporary plugging material parameters.

[0011] In some embodiments, the temporary plugging material parameters comprise at least one of the number, size, type, etc. of the temporary plugging material.

[0012] In some embodiments, the judging whether the temporary plugging is effective comprises judging the accumulation of the temporary plugging material at the opening of the fracture.

[0013] In some embodiments, the perforations are arranged in multiple rows along the axial direction of the stainless steel tube; and each row of the perforations is annularly distributed in the circumferential direction of the stainless steel tube.

[0014] The present application has the following advantages:

[0015] (1) The present application uses transparent high-strength PMMA material and cooperates with reasonable light source and camera setting, which can accurately observe the fracture propagation at different stages, the migration of temporary plugging particles in the simulated wellbore, the distribution between fractures and the temporary plugging formation process, etc. under the premise of ensuring that the sample is close to the mechanical characteristics of the formation rock being studied, and overcomes the problem that the traditional artificial cement sample or natural sample cannot be accurately observed.

[0016] (2) The transparent observation feature of the present application cooperates with the pumping curve to completely restore the temporary plugging and fracturing construction process, including the changes of pumping pressure and fracture propagation before, during and after the temporary plugging.

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

[0018] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not limiting; in these embodiments, the same reference numerals denote the same structures, wherein:

[0019] Figure 1 This is an exemplary flowchart of an experimental testing method for simulating a temporary plugging fracturing process, as shown in some embodiments of this specification.

[0020] Figure 2 This is a schematic diagram of the structure of a simulated multi-fracture temporary plugging fracturing specimen, as shown in some embodiments of this specification.

[0021] Figure 3A This is one of the structural schematic diagrams of the crack before temporary plugging, according to some embodiments of this specification;

[0022] Figure 3B This is the second schematic diagram of the crack structure before temporary plugging, based on some embodiments of this specification;

[0023] Figure 3C This is the third schematic diagram of the crack structure before temporary plugging, based on some embodiments of this specification;

[0024] Figure 4 This is a schematic diagram of the crack structure during temporary plugging, as shown in some embodiments of this specification;

[0025] Figure 5 This is a schematic diagram of the crack structure formed after temporary plugging is effective, as shown in some embodiments of this specification;

[0026] Figure 6 This is a schematic diagram of the structure of the crack formed after temporary plugging fails, as shown in some embodiments of this specification. Detailed Implementation

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present specification, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some examples or embodiments of the present specification, and for those skilled in the art, the present specification can also be applied to other similar scenarios without creative labor on the basis of these drawings. Unless it is obvious from the language environment or otherwise stated, the same reference numbers in the drawings represent the same structure or operation.

[0028] Flowcharts are used in the present specification to illustrate the operations performed by the system according to the embodiments of the present specification. It should be understood that the preceding or subsequent operations are not necessarily performed in sequence. On the contrary, each step can be processed in reverse order or simultaneously. Meanwhile, other operations can also be added to these processes, or one or more steps of operations can be removed from these processes.

[0029] Figure 1 is an exemplary flowchart of an experimental testing method for simulating a temporary plugging fracturing process according to some embodiments of the present specification. Figure 2 is a structural schematic diagram of a visualized multi-fracture temporary plugging fracturing simulation sample according to some embodiments of the present specification. As shown in Figure 1 The flow 100 includes the following steps.

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

[0031] The visualized multi-fracture temporary plugging fracturing simulation sample 200 refers to a sample for experimental testing of simulating a temporary plugging fracturing process.

[0032] In some embodiments, the visualized multi-fracture temporary plugging fracturing simulation sample 200 can be configured to simulate a fractured formation. For example, the mechanical characteristics of the visualized multi-fracture temporary plugging 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 multi-fracture temporary plugging fracturing simulation sample 200 is transparent so that the inside can be observed from the outside. In some embodiments, the visualized multi-fracture temporary plugging fracturing simulation sample 200 can be made of a transparent material. For example, polymethyl methacrylate (PMMA) or the like.

[0034] In some embodiments, the visualized multi-fracture temporary plugging fracturing simulation sample 200 can include a plurality of shapes. For example, at least one of a cylindrical shape, a prismatic shape, etc. In some embodiments, as shown in Figure 2As shown, the visualized multi-fracture temporary plugging fracturing simulation specimen 200 can be cubic in shape. In some embodiments, the side length of the visualized multi-fracture temporary plugging fracturing simulation specimen 200 can 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 fracturing simulation specimen 200 can also be other values.

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

[0036] In some embodiments, at least a portion of the stainless steel tube 300 may extend out of the visualized multi-crack temporary plugging 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 ring 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, fabricating a visual multi-fracture temporary plugging fracturing simulation specimen 200 may include determining the mechanical characteristics of the casting material, setting a stainless steel tube 200 inside a casting mold, casting the casting material inside the casting mold, and obtaining the visual multi-fracture temporary plugging fracturing simulation specimen 200.

[0040] The casting material refers to a material used for casting the visual multi-fracture temporary plugging fracturing simulation sample 200. For example, polymethyl methacrylate (PMMA) or the like.

[0041] In some embodiments, the operator can cast a standard sample based on the casting material.

[0042] The standard sample refers to a sample used for verifying mechanical characteristics. In some embodiments, after casting 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, the ratio, and the like of the casting material, so as to change the mechanical characteristics corresponding to the standard sample. In some embodiments, the operator can make the mechanical characteristics of the casting sample the same as the mechanical characteristics of the simulated fractured formation based on the confirmed at least one of the formula, the ratio, and the like of the 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, the visual multi-fracture temporary plugging fracturing simulation sample 200 can be obtained after the casting material is cooled. 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 visual multi-fracture 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 visual multi-fracture temporary plugging fracturing simulation sample 200 is provided with at least one light source window (not shown in the figure).

[0044] The light source window refers to a slot-shaped structure that can be used to install a light source. In some embodiments, the light source window can be formed in various ways. For example, at least one of using a casting mold, mechanical processing, and the like.

[0045] In some embodiments, the light source window can be arranged on the upper surface of the visual multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, the upper surface of the visual multi-fracture temporary plugging fracturing simulation sample 200 can be provided with a plurality of light source windows. For example, three, four, or other quantities. The plurality of light source windows can be arranged in an array on the upper surface of the visual multi-fracture temporary plugging fracturing simulation sample 200.

[0046] In some embodiments, at least one surface of the visual multi-fracture temporary plugging fracturing simulation sample 200 is provided with at least one observation window (not shown in the figure).

[0047] The observation window refers to a window that can be used to observe the inside of the visual multi-fracture temporary plugging fracturing simulation sample 200. In some embodiments, the observation window can be formed in various ways. For example, at least one of using a casting mold, mechanical processing, and the like.

[0048] In some embodiments, an observation window can be provided on the side of the visualized multi-fracture temporary plugging fracturing simulation sample 200.

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

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

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

[0052] The liquid injection pump can be used to pump liquid. For example, pumping fracturing fluid, guar gum, and the like. In some embodiments, the liquid injection pump can be in communication with the stainless steel pipe 300 and pump liquid into the stainless steel pipe 300.

[0053] The loading plate can be used to apply pressure to the visualized multi-fracture temporary plugging fracturing simulation sample 200 to simulate a stress environment. In some embodiments, the loading plate can apply pressure to the visualized multi-fracture temporary plugging fracturing simulation sample 200 from multiple directions. For example, the loading plate can apply pressure to the visualized multi-fracture temporary plugging fracturing simulation sample 200 from three directions. One of the three directions is perpendicular to the upper surface of the visualized multi-fracture temporary plugging fracturing simulation sample 200, and the other two directions are perpendicular to two adjacent measurement surfaces of the visualized multi-fracture temporary plugging fracturing simulation sample 200, respectively. 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 for controlling other mechanisms to perform corresponding actions or functions. In some embodiments, the liquid injection pump and the loading plate can be in communication with the controller, respectively. The controller can control the liquid injection pump and the loading plate, respectively.

[0055] In some embodiments, the true triaxial large physical simulation experimental device can further include a display. The display can be in communication with the controller. The controller can control the display to display data. The data can include at least one of text, images, animations, and the like.

[0056] In some embodiments, the operator can install the light source 400 in the light source window. The light source 400 can emit light rays to the inside of the visualized multi-fracture temporary plugging fracturing simulation sample 200, thereby increasing the brightness of the inside of the visualized multi-fracture temporary plugging fracturing simulation sample 200, and making the inside of the visualized multi-fracture temporary plugging fracturing simulation sample 200 easier to be viewed.

[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 with a size of 150mm*150mm*10mm. In some embodiments, the light source 400 can be communicatively connected with the controller. The controller can control the light source 400 to at least one of start, stop, 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 can be connected in various ways. For example, at least one of bonding, clamping, etc.

[0059] In some embodiments, the operator can install the camera 500 in the observation window. The camera 500 can be used to take pictures of the inside of the visualized multi-fracture temporary plugging fracturing simulation sample 200 and its changes. In some embodiments, two cameras 500 can be arranged on one side of the visualized multi-fracture temporary plugging 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 can be connected in various ways. For example, at least one of bonding, clamping, etc.

[0061] In some embodiments, the camera 500 can be communicatively connected with the controller, and the controller can control the camera 500 to at least one of start, stop, take pictures of the inside of the visualized multi-fracture temporary plugging fracturing simulation sample 200, etc. In some embodiments, the data taken by the camera 500 can be transmitted to the controller.

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

[0063] In some embodiments, the operator can install the visual multi-fracture temporary plugging and fracturing simulation sample 200 in the triaxial chamber of the true triaxial large-scale physical simulation experiment device. For example, on the working plane in the triaxial chamber. In some embodiments, the working plane can be provided with a positioning structure and a fixing structure. 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 mechanical hand, etc.

[0064] In some embodiments, the operator can connect the stainless steel pipe 300 with the liquid injection pump. For example, the operator can connect the stainless steel pipe 300 with the liquid injection pump through the pipeline. The controller can control the liquid 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 experiment device controls the loading plate to load the visual multi-fracture temporary plugging and fracturing simulation sample 200. For example, the controller can control the loading plate to move towards the visual multi-fracture temporary plugging and fracturing simulation sample 200 until contact. In some embodiments, after the loading plate contacts the visual multi-fracture temporary plugging and fracturing simulation sample 200, the controller can control the loading plate to continue to move towards the visual multi-fracture temporary plugging and 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 visual multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, the controller can control the loading plate to load the visual multi-fracture temporary plugging and fracturing simulation sample 200 with a pressure of 1-2 MPa until the pressure feedback of the loading plate is stable. The pressure feedback refers to the pressure detected by the loading plate after the loading plate loads the visual multi-fracture temporary plugging and fracturing simulation sample 200. In some embodiments, the loading plate can be provided with a pressure sensor for detecting pressure. The pressure sensor can be in communication connection with the controller. The controller can receive the data detected by the pressure sensor. In some embodiments, when the pressure feedback of the loading plate is stable, the controller can control the loading plate to continue to apply pressure to the visual multi-fracture temporary plugging and fracturing simulation sample 200 until the pressure reaches a preset value. The preset value can be set according to actual needs.

[0066] Step 130, simulate the fracture propagation process before temporary plugging. In some embodiments, step 130 can be performed by the true triaxial large-scale physical simulation experiment device.

[0067] In some embodiments, the true triaxial large-scale physical simulation experiment device can control the liquid 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 a fracture 600. In some embodiments, the fracturing fluid that exits the stainless steel pipe 300 from the perforations located in the same row can form fractures 600 located in the same plane. In some embodiments, the perforations located in the same row can correspond to the formation of circular or similar circular fractures.

[0068] The temporary plugging fracturing parameters refer to parameters related to the fracturing fluid. In some embodiments, the temporary plugging fracturing parameters can 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 as needed.

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

[0070] In some embodiments, the controller of the true triaxial large-scale physical simulation experiment device can control the camera 500 to record the change of the fracture 600 in the visualized multi-fracture temporary plugging fracturing simulation sample 200 before temporary plugging. For example, record the forming process of the fracture 600, etc. Before temporary plugging refers to the period of time when the perforations have not been temporarily plugged.

[0071] Figure 3A is one of the structure schematic diagrams of the fracture before temporary plugging according to some embodiments of the present specification. Figure 3B is the second structure schematic diagram of the fracture before temporary plugging according to some embodiments of the present specification. Figure 3C is the third structure schematic diagram of the fracture before temporary plugging according to some embodiments of the present specification.

[0072] Step 140, simulate the fracture propagation process during temporary plugging. In some embodiments, step 140 can be performed by the true triaxial large-scale physical simulation experiment device.

[0073] During temporary plugging refers to the period of time when the perforations are temporarily plugged.

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

[0075] The temporary plugging particles 700 refer to granular solid substances. In some embodiments, the temporary plugging particles 700 can adopt plastic particles. In some embodiments, the temporary plugging particles 700 can be configured to temporarily plug the entrance of the fracture 600. That is, temporarily plug the perforations.

[0076] In some embodiments, the operator can determine whether the fracture 600 before the temporary plugging appears non-equilibrium change. For example, the operator can determine whether the fracture 600 appears non-equilibrium change based on the change of the fracture 600 before the temporary plugging captured by the camera 500.

[0077] The non-equilibrium change refers to the abnormality of the formation of the fracture 600. In some embodiments, the non-equilibrium change can include at least one of the abnormal initiation, the non-equilibrium propagation, and the like. The non-equilibrium change can form a non-equilibrium fracture 610.

[0078] The abnormal initiation refers to that when the fracturing fluid applied by the perforating pair to the visualized multi-fracture temporary plugging fracturing simulation sample 200, the radius of the fracture 600 formed is less than or equal to a first threshold value. The first threshold value can include various values. For example, at least one of 0, one-fifth of the predicted radius, one-tenth of the predicted radius, and the like. The predicted radius refers to the predicted radius of the fracture 600 formed. In some embodiments, the predicted radius can be a preset value. The abnormal initiation can form an abnormal fracture 620.

[0079] The non-equilibrium propagation refers to that when the fracturing fluid applied by the perforating pair to the visualized multi-fracture temporary plugging fracturing simulation sample 200, the radius of the fracture 600 formed is less than or equal to a second threshold value. The first threshold value can include various values. For example, at least one of four-fifths of the measured radius, four-fifths of the actual maximum radius, and the like. 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, the controller, in response to the non-equilibrium change of the fracture 600 before the temporary plugging, replaces the fracturing fluid with the guar gum while pumping the temporary plugging particles 700 into the stainless steel pipe 300 under the condition that the injection and discharge rate remains unchanged.

[0081] In some embodiments, the diameter of the temporary plugging particles 700 can be less than or equal to 40 mesh. In some embodiments, the total apparent volume of the temporary plugging particles 700 is not 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 experiment device can control the camera 500 to record the change of the fracture during the temporary plugging in the visualized multi-fracture temporary plugging fracturing simulation sample 200.

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

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

[0085] In some embodiments, such as Figure 4 As shown, the operator can observe the movement of the temporary plugging particles 700 within the stainless steel tube 300 and their aggregation at the entrance of the crack to determine the effectiveness of the temporary plugging. For example, the operator can observe the movement of the temporary plugging particles 700 within the stainless steel tube 300 and their aggregation at the entrances of different cracks, and combine this with the changes in the pump pressure of the injection pump or the hydraulic pressure within the stainless steel tube 300 over time to determine the effectiveness of the temporary plugging. In some embodiments, when the temporary plugging particles 700 flow toward the perforation corresponding to the unevenly changing crack 600 and aggregate at the corresponding perforation, accompanied by a continuous increase in the pump pressure of the injection pump or the hydraulic pressure within the stainless steel tube 300, the operator and / or the controller can determine that the temporary plugging is effective.

[0086] Figure 5 This is a schematic diagram of the crack structure formed after temporary plugging is effective, as shown in some embodiments of this specification.

[0087] Step 161, in response to the effective temporary plugging, simulates the crack 600 propagation process after 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 exhibits an uneven change after temporary plugging. In some embodiments, the operator and / or controller can determine whether the crack 600 exhibits an uneven change based on video captured by the camera 500. For example, observing whether the crack 600, which was determined to have an uneven change before plugging, has changed again.

[0089] In some embodiments, the operator and / or controller stops pumping in temporary plugging particles 700 in response to a uniform change in the crack 600 after temporary plugging.

[0090] A balanced change occurs when a crack 600, initially identified as having a non-balanced change, forms a new crack 600 after the temporary closure is effective. The radius of the new crack 600 is greater than or equal to the second threshold. For more information on the second threshold, please refer to the relevant description in step 140.

[0091] In some embodiments, the operator and / or controller can replace the guar gum with fracturing fluid while maintaining the same injection rate, and control the injection pump to continuously pump fracturing fluid into the stainless steel tube 300 until at least one temporarily plugged fracture 600 extends to the edge of the visualized multi-fracture temporarily plugged 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 FIG. 7 is a structural diagram of a fracture formed after the temporary plugging is invalid according to some embodiments of the present specification.

[0093] In step 162, the temporary plugging and fracturing parameters are optimized in response to the temporary plugging being invalid. In some embodiments, step 162 can be performed by the operator and / or the controller.

[0094] The temporary plugging being invalid means that the temporary plugging particles 700 do not accumulate at the perforation, or the pump pressure of the liquid injection pump or the hydraulic pressure in the stainless steel pipe 300 does not change over time.

[0095] Optimizing the temporary plugging and fracturing parameters means adjusting at least one of the temporary plugging and fracturing parameters. The adjustment can include at least one of increasing, deleting, increasing, decreasing, etc.

[0096] For more information about the temporary plugging and fracturing parameters, see the related description of step 130.

[0097] In some embodiments, the operator and / or the controller can also optimize the temporary plugging and fracturing parameters when all the fractures 600 appear to be unequally expanded.

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

[0099] In some embodiments, when all the fractures 600 appear to be unequally expanded, the operator and / or the controller can control the pump-in time to be advanced, so that the temporary plugging fractures can be expanded evenly.

[0100] The pump-in time refers to the time point at which the temporary plugging particles 700 are pumped in. The pump-in time can be the time point after step 120 or step 130 lasts for a preset time.

[0101] For example only, after step 130 lasts for 10 minutes, the true triaxial large-scale physical simulation experimental device performs the fracture expansion process during the simulated temporary plugging. The time point after step 130 lasts for 10 minutes is the pump-in time. The operator and / or the controller can control the pump-in time to be advanced, for example, by 2 minutes. That is, after step 130 lasts for 8 minutes, the true triaxial large-scale physical simulation experimental device performs the fracture expansion process during the simulated temporary plugging, and the controller can control the liquid injection pump to pump the temporary plugging particles 700 into the stainless steel pipe 300. In this way, the length of time during the temporary plugging can be extended, and the temporary plugging particles 700 can more easily plug the entrances of the fractures 600.

[0102] In some embodiments, based on the adjusted temporary plugging fracturing parameters, guar gum is continuously pumped in, and it is determined whether the fracture 600 after the adjustment of the temporary plugging fracturing parameters shows an unbalanced change.

[0103] In some embodiments, the parameters of the temporary plugging material are adjusted in response to an uneven change in the crack 600 after temporary plugging.

[0104] Temporary plugging material parameters refer to parameters related to the temporary plugging particles 700. In some embodiments, the temporary plugging material parameters include at least one of the following: quantity, size, type, stiffness, etc. of the temporary plugging material.

[0105] In some embodiments, adjusting the parameters of the temporary plugging material may include at least one of the following: 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 the temporary plugging particles 700, or introducing flexible temporary plugging materials such as knots.

[0106] The experimental testing method simulating the temporary plugging fracturing process utilizes transparent, high-strength PMMA material and a suitable light source and camera setup. This ensures that the sample closely approximates the rock mechanics characteristics of the studied formation, accurately observing different stages of fracture propagation, the migration of plugging particles (700) within the simulated wellbore's stainless steel casing, fracture distribution, and the plugging formation process. Combined with pump injection curves, it can completely reconstruct the entire temporary plugging fracturing construction process, including before, during, and after plugging. Furthermore, by using transparent samples and a cost-effective, readily available light source and wide-angle camera for monitoring, the overall experimental costs are reduced by tens of thousands of yuan while accurately recording the fracture propagation process. This facilitates its widespread application in various institutions and better serves the design of temporary plugging fracturing construction parameters.

[0107] The basic concepts have been described above. Obviously, for those skilled in the art, the detailed disclosure above is merely illustrative and does not constitute a limitation of this specification. Although not explicitly stated herein, 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 and therefore remain within the spirit and scope of the exemplary embodiments described herein.

[0108] Furthermore, this specification uses specific terms to describe embodiments thereof. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of this specification. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Moreover, certain features, structures, or characteristics in one or more embodiments of this specification can be appropriately combined.

[0109] Finally, it should be understood that the embodiments described herein are only given by way of example and that other modifications can occur to persons skilled in the art. Therefore, the scope of the present description is not intended to be limited to the embodiments described herein but is only limited by the claims.

Claims

1. An experimental testing method for simulating a temporary plugging fracturing process, characterized in that, include: Create a visual simulation specimen of multi-fracture temporary plugging fracturing; The preparation of the visualized multi-fracture temporary plugging fracturing simulation specimen 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, and fracture toughness; setting a stainless steel tube inside the casting mold; and casting the casting material inside the casting mold to obtain the visualized multi-fracture temporary plugging fracturing simulation specimen. The visualized multi-fracture temporary plugging fracturing simulation sample is configured to simulate a fracturing formation; The visualized multi-fracture temporary plugging fracturing simulation sample is transparent; The visualization multi-crack temporary plugging fracturing simulation specimen was loaded using a true triaxial large-scale physical simulation experimental device to simulate the stress environment; Simulates the crack propagation 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 tube based on the temporary plugging fracturing parameters. The fracturing fluid applies force to the visualized multi-fracture temporary plugging fracturing simulation sample through the perforation, causing the visualized multi-fracture temporary plugging fracturing simulation sample to form fractures. Simulates the crack propagation process during temporary plugging; Temporary plugging particles are pumped into the stainless steel pipe; The temporary plugging particles are configured to temporarily plug the entrance to the crack; The simulated fracture propagation process during temporary plugging also includes: determining whether the fracture exhibits uneven changes before temporary plugging; responding to uneven changes in the fracture before temporary plugging, replacing the fracturing fluid with guar gum while maintaining the injection rate unchanged, and simultaneously pumping temporary plugging particles into the stainless steel tube; observing the movement of the temporary plugging particles within the stainless steel tube and their aggregation at the fracture entrance to determine the effectiveness of the temporary plugging; Determining whether the temporary blockade is effective, and In response to the effectiveness of the temporary plugging, the fracture propagation process after temporary plugging is simulated; the simulation of the fracture propagation process after temporary plugging includes: determining whether the fracture after temporary plugging shows an uneven change; in response to the fracture after temporary plugging showing an even change, stopping the pumping of the temporary plugging particles; and replacing the guar gum with the fracturing fluid while keeping the injection rate constant, until at least one of the temporarily plugged fractures propagates to the edge of the visualized multi-fracture temporary plugging fracturing simulation specimen; In response to the failure of the temporary plugging, the temporary plugging fracturing parameters are optimized.

2. The experimental testing method for simulating temporary plugging fracturing process as described in claim 1, characterized in that, The loading of the visualized multi-crack temporary plugging fracturing simulation specimen using a true triaxial large-scale physical simulation experimental device, and the simulation of the stress environment, also include: Install a light source inside the light source window and a camera inside the observation window; The visualized multi-fracture temporary plugging fracturing simulation sample was installed in the triaxial chamber of the true triaxial large-scale physical simulation experimental device; Connect the stainless steel pipe to the injection pump; The loading plate of the true triaxial large-scale physical simulation experimental device is controlled to load the visualized multi-fracture temporary plugging fracturing simulation specimen until the stress borne by the visualized multi-fracture temporary plugging fracturing simulation specimen reaches the preset value.

3. The experimental testing method for simulating temporary plugging fracturing process as described in claim 1, characterized in that, The simulated crack propagation process before temporary plugging also includes: Record the changes in fractures before temporary plugging within the visualized multi-fracture temporary plugging fracturing simulation specimen.

4. The experimental testing method for simulating temporary plugging fracturing process as described in claim 1, characterized in that, In response to the ineffectiveness of the temporary plugging, optimizing the temporary plugging fracturing parameters includes: Adjust the temporary plugging fracturing parameters; Based on the adjusted temporary fracturing parameters, the guar gum is continued to be pumped in, and it is determined whether the fracture after temporary plugging shows an uneven change. In response to the non-equilibrium changes in the cracks after temporary plugging, the parameters of the temporary plugging material are adjusted.

5. The experimental testing method for simulating temporary plugging fracturing process as described in claim 4, characterized in that, The parameters of the temporary plugging material include at least one of the following: quantity, size, and type of the temporary plugging material.

6. The experimental testing method for simulating temporary plugging fracturing process as described in claim 1, characterized in that, At least one light source window is opened on at least one surface of the visualized multi-fracture temporary plugging fracturing simulation specimen; At least one observation window is opened on at least one surface of the visualization multi-fracture temporary plugging fracturing simulation specimen.

7. The experimental testing method for simulating temporary plugging fracturing process as described in 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 arranged in a ring around the circumference of the stainless steel tube.

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