A visual full-range gravel packing construction and production full-stage experiment simulation system and method

Abstract

The present application belongs to the field of oil and gas and natural gas hydrate exploitation engineering, and particularly relates to a visual full-series gravel packing construction and production full-stage experimental simulation system and method. The present application sets a visual window on the side wall of a pressure-bearing bin, and forms an observation port by cutting the side wall of a composite sand prevention unit along an axial direction, the observation port being in sealing connection with the visual window, thereby forming a high-pressure transparent visual cavity structure; the composite sand prevention unit integrates a replaceable screen pipe unit and a well wall simulation unit, simulates different well types and sand prevention structures, and continuously observes processes such as sand particle shedding, migration, accumulation and sand prevention layer blockage under controllable flow conditions. During the experiment, multi-source data such as pressure, pressure difference, flow and images at different positions of the reservoir and the sand prevention layer can be synchronously collected, so as to further study the dynamic change law of the permeability with the sand production and blockage processes, and deeply reveal the percolation coupling relationship between the reservoir and the sand prevention layer.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas and natural gas hydrate extraction engineering, specifically involving a visualized full-series gravel backfilling construction and production full-stage experimental simulation system and method. Background Technology

[0002] Loose sandstone reservoirs are widely distributed in continental basins in my country. These reservoirs have high porosity and permeability, but are generally poorly cemented, loosely structured, and highly stress-sensitive. During development, the formation near the wellbore is prone to particle detachment and migration under pressure differentials, leading to sand production. Sand production not only affects wellbore stability but also causes the failure of sand control structures and wear on the production system. Therefore, establishing an effective sand control technology system is crucial for the efficient development of loose sandstone reservoirs.

[0003] Currently, various technologies are widely used in the field, including gravel packing, screen completion, resin sand fixation, and composite sand control. With the application of horizontal wells, multi-branch wells, and stratified development technologies, wellbore structures are becoming increasingly complex, reservoir formation combinations vary significantly, and the adaptability of different sand control methods differs significantly under different well types and formation conditions. The stability of sand control structures, the blockage evolution process, and long-term effectiveness have become key factors affecting development results.

[0004] Current indoor sand control evaluation experiments mostly employ artificial sand filling methods, evaluating sand-blocking capacity through fluid scouring within a metal pressure-bearing cavity. While this type of experiment plays a certain role in basic screening, many problems still exist.

[0005] (1) Distortion of formation sand source. Most experiments use the incoming flow sand-carrying method to simulate the sand production process. The sand particles are not generated by the natural destruction of reservoir rock samples under formation stress conditions. They fail to reflect the real process of reservoir stress destruction, particle stripping, and migration, and are difficult to accurately characterize the reservoir's sand supply capacity.

[0006] (2) Lack of visual monitoring methods. Most existing experimental devices are opaque metal cavities, which can only collect sand volume through the outlet for statistical analysis. They cannot observe the migration path, intrusion morphology and sand bridge formation process of formation sand in the porous medium in real time, and it is difficult to obtain the spatial distribution characteristics of sand migration.

[0007] (3) Insufficient simulation capability of well type and stratigraphic structure. Traditional experimental devices have fixed structures and are mostly single vertical well models, which are difficult to simulate complex well types such as horizontal wells and branch wells. They are also unable to construct heterogeneous reservoir models with multiple layers, different permeability or different particle size gradation combinations, which limits the study of sand production behavior and the selection of sand control methods under complex reservoir conditions.

[0008] To address the aforementioned issues, it is necessary to construct a sand control evaluation experimental system that can simulate the actual sand supply environment under formation stress conditions, possess visual monitoring capabilities, and flexibly simulate different well structures and multi-level combinations, in order to improve the pertinence and reliability of sand control design. Summary of the Invention

[0009] To address the shortcomings of existing technologies, such as insufficient visualization methods, difficulty in conducting multi-condition simulations based on actual reservoir conditions and completion methods, and lack of overall evaluation capabilities for near-wellbore reservoir and sand control layer composite systems, this invention proposes a visualized full-series gravel packing construction and production full-stage experimental simulation system and method. This invention establishes a viewing window on the sidewall of the pressure chamber and forms an observation port by axially cutting one side of the sidewall of the composite sand control unit. The observation port and the viewing window are sealed together, forming a high-pressure transparent viewing cavity structure. The composite sand control unit integrates a replaceable screen unit and a wellbore simulation unit to simulate different well types and sand control structures. Under controlled flow conditions, it continuously observes processes such as sand particle stripping, migration, accumulation, and sand control layer blockage. Simultaneously, the system possesses good adjustability and combinability, allowing for flexible configuration based on different reservoir properties and sand control completion methods. It also features simultaneous acquisition of multiple parameters such as pressure, differential pressure, flow rate, and images, providing a unified platform for comparative sand control experiments under different conditions.

[0010] Based on the above structure, this invention can not only conduct visual research on the dynamic response of sand control layers under reservoir sand supply conditions, but also construct multi-layer composite systems to comprehensively evaluate interlayer pressure differential distribution, sand particle invasion depth, and plugging coupling effects. By switching different well structures and sand control methods, and conducting experiments under production regimes such as constant flow, constant pressure differential, or periodic well switching, the impact of different operating conditions on sand control performance and stability can be systematically analyzed, providing visual and quantifiable experimental evidence for optimizing sand control schemes under complex reservoir conditions.

[0011] The technical problem to be solved by the present invention is achieved by the following technical solution: a full-stage experimental simulation system for the construction and production of gravel backfilling, including a high-pressure resistant visual reservoir simulation unit, a simulated multi-layer separation device, a composite sand control unit, a fluid displacement unit, a squeeze backfilling pumping unit, a wellbore external backfilling simulation unit, a production collection and separation unit, an image acquisition unit, and a data measurement and acquisition unit. The high-pressure-resistant visual reservoir simulation unit includes a pressure chamber and a simulated reservoir medium placed inside the pressure chamber for simulating the reservoir. The pressure chamber has inlets on its sidewalls and bottom to simulate multi-directional formation flow, and an outlet at the top. The simulated reservoir medium is used to simulate the near-wellbore reservoir area and can be artificial sand or equivalent core material. The pressure chamber can withstand a maximum pressure of 10 MPa. The inlet is connected to the fluid displacement unit via a pipeline, and a control valve and a flow meter are installed on the pipeline corresponding to each inlet. The lower end of the outlet is connected to a composite sand control unit installed in the pressure chamber to simulate the wellbore production process; the composite sand control unit is used to simulate the well completion structure and sand control system in actual engineering, and to visualize the sand movement and blockage behavior inside the sand control layer. The sidewall of the composite sand control unit is axially cut open to form an observation port, which is sealed to the viewing window. During the experiment, the sand movement and clogging behavior on the surface of the screen tube unit and in the area near the screen tube unit can be visually monitored in conjunction with the image acquisition unit. The composite sand control unit includes a screen pipe unit and a wellbore simulation unit. The screen pipe unit is coaxially arranged inside the wellbore simulation unit, and an annulus is provided between the screen pipe unit and the wellbore simulation unit. The annulus is filled with sand control medium. The screen pipe unit and the wellbore simulation unit are detachably connected. The wellbore simulation unit has a threaded nut that mates with the thread of the screen pipe unit. The combination of the two is the same as the combination of a screw and a nut. The wellbore simulation unit is used to simulate the wellbore or casing structure. Its inner diameter can be set to different specifications to form different sand control filling radii. A sand control filling space is formed between the screen pipe unit and the wellbore simulation unit. The sand control filling space can be filled with gravel, ceramsite, or other sand control media to construct a multi-layer composite sand control system of near-wellbore reservoir and sand control layer, thereby realizing the visualization simulation and comprehensive evaluation of the coupling behavior of near-wellbore reservoir and sand control structure. The wellbore simulation unit is used to simulate different well completion structures. The screen unit includes a base pipe and a detachable screen set on the outside of the base pipe. The type, precision and structure of the screen medium can be changed according to experimental requirements. The outer wall of the base pipe is provided with multiple uniformly distributed through holes to simulate the flow conditions of the screen unit. The wellbore external filling layer simulation unit includes a semi-enclosed filling mold formed of a metal filter screen. The opening side of the filling mold is connected to the side wall of the composite sand control unit. The filling mold is used to fill the sand control medium. The screen pipe unit and the sand control medium form a sand control layer. The simulated multi-layer partitioning device includes a detachable partition plate installed inside the pressure chamber. Multiple keyways are provided on the side wall of the pressure chamber, which cooperate with the layer partitioning device, i.e., the partition plate, to simulate reservoirs with different properties in different partitions, so as to simulate different layer combinations and the working conditions of simultaneous production of multiple layers. The fluid displacement unit is used to provide displacement medium to the high-pressure-resistant visual reservoir simulation unit through the inlet. The extrusion filling pump unit is used to provide filling medium to the high-pressure visual reservoir simulation unit through the outlet to simulate the high-pressure filling process. The output collection and separation unit is connected to the composite sand control unit through the outlet, and is used to collect the solid and liquid produced by the composite sand control unit during the experiment and perform solid-liquid separation. A control valve and a flow meter are installed on the pipeline between the outlet and the output collection and separation unit. The image acquisition unit includes a microscopic image acquisition device set in the viewing window, used to record in real time the processes of reservoir sand body exfoliation, migration, sand-proof layer blockage, and the evolution of the mixing zone; The data measurement and acquisition unit includes a pressure sensor installed in the simulated reservoir medium through a sensor mounting hole, a flow meter on the pipeline, and a data acquisition module connected to the pressure sensor and flow meter. It is used to simultaneously acquire pressure, differential pressure, and flow information inside the reservoir, wellbore, and sand control structure, and realize the corresponding analysis of macroscopic parameters and microscopic images.

[0012] The pressure sensor's installation location is adjustable, and it is used to obtain pressure change information inside the reservoir and in the near-wellbore area.

[0013] The aforementioned system is used for visual observation and quantitative analysis of the reservoir sand production process and the working status of sand control structures.

[0014] Preferably, in this invention, both the screen tube unit and the well wall simulation unit are half-sectioned from the center of the axis, so that the area around the screen tube unit and the sand control filling space are observable during the experiment, thereby enabling real-time observation of the sand particle intrusion, accumulation and blockage evolution process in the sand control medium (the cut-out parts of the screen tube unit and the well wall simulation unit need to be tightly attached to the viewing window, and a sealing ring needs to be added between the two to ensure a seal).

[0015] Preferably, the wellbore simulation unit of the present invention includes a vertical wellbore, a horizontal wellbore, an inclined wellbore, and a branch well.

[0016] Preferably, the wellbore external filling layer simulation unit of the present invention includes a void mold, a compression filling mold, and a fracturing filling mold; The extrusion filling mold and fracturing filling mold are filled with sand-control medium. The extrusion filling mold is a quarter-circular mold made of 15-mesh metal filter screen. The inner ring radius matches the composite sand-control unit. The side that matches the composite sand-control unit does not have a filter screen, while the side that contacts the simulated formation has a filter screen. The fracturing filling mold is a semi-pyramidal mold to simulate fracturing fractures. Different molds are provided for horizontal and vertical fractures.

[0017] Preferably, the pressure chamber is provided with uniform inflow channels connected to the inlet on its side wall and bottom, and the uniform inflow channels are provided with screens that are parallel to and spaced apart from the inner wall of the pressure chamber.

[0018] Preferably, the fluid displacement unit of the present invention includes a horizontal flow pump and an intermediate container; The advection pump is connected to the inlet via an intermediate container. A piston is installed inside the intermediate container, dividing its interior into a fluid chamber and a drive chamber. The advection pump is connected to the drive chamber, and the fluid chamber is connected to the inlet. This provides a stable and controllable displacement fluid to the reservoir simulation unit. The displacement method can be constant flow displacement or constant pressure differential displacement to simulate reservoir flow conditions under different production regimes. The intermediate container is used to displace viscous water. The advection pump cannot displace high-viscosity fluids, therefore an intermediate container is needed. The intermediate container is a piston-like container similar to a syringe, and the advection pump provides the driving pressure. The production collection and separation unit includes a production collection tank and a solid-liquid separation device connected in sequence to the outlet, which are used to collect the produced fluid and separate the formation sand carried therein, so as to realize the quantitative statistics and analysis of the sand output. The extrusion filling pump unit includes a filling medium supply container and a simulated filling pump unit connected in sequence to the outlet.

[0019] This invention also discloses a method for visualizing the entire process of gravel backfilling construction and production, which is prepared using the above method and includes the following steps: S1. Reservoir Media Preparation and Loading The simulated reservoir medium is configured according to the target reservoir type. The simulated reservoir medium is artificial formation sand or equivalent reservoir filling material. The particle size, cementation strength and water content parameters of the filling medium are controlled to meet the experimental requirements. The simulated reservoir medium is loaded into the pressure chamber, and the layers are set according to the experimental purpose to simulate different layer combinations or caprock conditions. S2, Composite Sand Control Unit Configuration Select the composite sand control unit according to the experimental requirements, and determine the well type and corresponding screen structure parameters, including screen type, screen accuracy and inlet distribution form; Subsequently, sand-controlling medium is filled into the annular space between the screen tube unit and the well wall simulation unit. The sand-controlling medium is gravel, ceramsite or other equivalent materials. Different forms of sand-controlling filling structures are constructed by adjusting the inner diameter of the well wall simulation unit, selecting different filling mold combinations, filling medium types and filling thicknesses. S3. Setting Displacement Conditions and Starting the Experiment Displacement medium is injected into the pressure chamber through the fluid displacement unit; The displacement method is set to constant current displacement or constant pressure difference displacement to simulate reservoir flow conditions under different production regimes. During the experiment, the data measurement and acquisition unit simultaneously recorded the pressure, pressure difference, and flow rate changes inside the reservoir, in the wellbore, and at the sand control structure. By recording the pressure at different locations, the pressure difference of each measurement area can be calculated separately, and then the permeability can be calculated according to Darcy's law of radial flow. This allows the determination of which part is most severely blocked, and guides the implementation of corresponding construction measures on site to solve the blockage problem. S4. Visual observation and data acquisition of the sand production process The image acquisition unit, located outside the viewing window, records in real time the process of reservoir sand body exfoliation, migration path, mixing zone formation, sand-prevention layer blockage, and evolution. By combining data collected by pressure sensors placed at different locations in the reservoir and sand control layer, the pressure response and differential pressure changes at various locations in the reservoir, wellbore-screen structure and sand control filling layer are analyzed simultaneously to achieve the correspondence between microscopic images and macroscopic seepage parameters. S5. Evaluation of Output Collection and Sand Control Performance By using the production collection and separation unit set at one end of the outlet, the produced fluid is subjected to solid-liquid separation and the carried formation sand is collected, and the sand output at different experimental stages is statistically analyzed. By combining pressure, differential pressure, flow rate, and image data, a comprehensive evaluation is conducted on the degree of blockage of the sand control structure, sand particle penetration behavior, thickness variation of the mixed zone (the mixed zone of formation sand, i.e., the simulated reservoir medium, and gravel, i.e., the sand control medium), and the evolution of the seepage capacity of the composite system. In sand control operations, "sand particle penetration behavior" refers to the process by which formation sand (i.e., sand particles detached from the reservoir rock) passes through, intrudes into, or passes through sand control barriers (such as gravel-filled layers, screens, etc.) under the influence of fluid.

[0020] The present invention preferably includes simulation experiments on the evaluation of the sand control effect and parameter optimization of different sand control methods in loose sandstone reservoirs: (1) Evaluation experiment of independent sieve tube sand control method Select the appropriate well structure according to the experimental requirements, install the screen to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, and then install it as a whole in the designated position of the high pressure resistant visual reservoir simulation unit. Pressure sensors were installed around the composite sand control unit and near the pressure chamber wall. Formation sand was filled and consolidated according to experimental requirements to complete the experimental model construction. Pressure sensors near the pressure chamber wall were used to calculate the pressure difference in the near-wellbore reservoir section, i.e., the pressure difference in the near-wellbore reservoir section = pressure at the wellbore wall - pressure at the pressure chamber wall. This data can be used to analyze pressure changes in the near-wellbore reservoir section and thus reflect whether formation sand has migrated or become blocked. After the experiment began, the pressure changes at different locations of the reservoir and sand control layer were monitored in real time through the data measurement and acquisition unit. At the same time, the image acquisition unit was used to continuously record the reservoir morphology evolution process, focusing on observing and recording the formation and development of various depletion patterns. When the pressure increase at the sand control layer is less than the set threshold, it indicates that the sand control layer blockage process tends to be in equilibrium. At this time, the permeability change and seepage capacity evolution law of the reservoir and sand control layer are analyzed by combining the inlet pressure, the pressure outside the sand control layer and the outlet pressure, and the flow performance of the screen is evaluated. In addition, the produced fluid is separated into solid and liquid components by the production collection and separation unit, and the proportion of formation sand penetrating the sand control structure is calculated to comprehensively evaluate the sand-blocking capacity of the screen. While keeping other experimental conditions consistent, the above experiment was repeated with different types or precision sieves to compare and analyze the performance of different sieves in terms of seepage capacity and sand passage rate. (2) Evaluation experiment of annular circulating gravel filling sand control method Select the appropriate well structure according to the experimental requirements, install the screen to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, then fill the annulus of the two with the filling gravel to be evaluated, and then install it as a whole in the designated position of the high pressure resistant visual reservoir simulation unit. Pressure sensors were arranged around the composite sand control unit and near the wall of the pressure chamber. Formation sand was filled and consolidated according to the experimental requirements to complete the construction of the experimental model. Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand passing rate. Then, we conducted parallel experiments with gravel of different precision and types to compare and analyze the performance of different screens and gravel in terms of seepage capacity changes and sand passing rate. (3) Evaluation experiment of uniform extrusion filling method for sand prevention Select the appropriate well structure according to the experimental requirements, install the screen to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, and then fill the annulus between the two with the gravel to be evaluated. Based on the proportional relationship between the well to be simulated and the wellbore simulation unit, a suitable extrusion filling mold is selected and placed in the simulated reservoir after conversion. Gravel of the same precision and type as that in the annulus is filled into the mold. Then, the whole thing is installed in the designated position of the high-pressure resistant visual reservoir simulation unit. Pressure sensors are placed around the composite sand control unit and near the pressure chamber wall. Formation sand is filled in according to the experimental requirements and consolidation treatment is carried out to complete the construction of the experimental model. Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand passing rate. Then, we conducted parallel experiments with different precision and types of gravel to compare and analyze the performance of different gravels in terms of seepage capacity changes and sand passing rate. Finally, by comprehensively comparing the changes in seepage capacity and sand passage of screen pipe units, filling layers, and the overall reservoir and sand control layer under different sand control methods and parameters, the most suitable sand control method and parameters for the field conditions can be obtained.

[0021] The present invention preferably includes simulation experiments of the compression and filling process of loose sandstone depleted reservoirs and the production process after filling: Based on the stratigraphic combination characteristics of the target reservoir, different stratigraphic layers are separated using partition plates. Pressure sensors are placed near the composite sand control unit and on the pressure chamber wall of each sub-layer to monitor the pressure difference changes of each layer. According to the experimental requirements, the appropriate well structure is selected, and the screens to be evaluated in each sub-layer are assembled into the screen tube unit and assembled with the well wall simulation unit. Then, the filling medium to be evaluated is filled in the annular space between the screen tube unit and the well wall simulation unit to construct the composite sand control unit, and the whole unit is installed in the designated position of the high-pressure resistant visual reservoir simulation unit. Based on the specific data of different stratigraphic sands on site, corresponding simulated stratigraphic sands were filled into each layer, and the stratigraphic sands were consolidated to complete the overall construction of the experimental model. During the experiment, the inlet flow rate of each small layer was set according to the production allocation of each small layer on site. When the pressure increase at the sand control layer of each layer was less than the set threshold, that is, when the pressure change tended to stabilize and the blockage process reached a relatively balanced state, the permeability change and seepage capacity evolution law of each small layer reservoir and sand control layer were analyzed by combining the inlet pressure, the pressure outside the sand control layer and the outlet pressure data, so as to evaluate the flow performance of the gravel layer. Simultaneously, by collecting formation sand from inside screen units at different strata, the sand throughput of each layer is obtained; finally, the sand-blocking capacity of the gravel layer is comprehensively evaluated according to the evaluation method. The specific evaluation criteria for the evaluation method can be set independently or refer to existing technologies, and will not be elaborated here.

[0022] The present invention preferably includes a simulation experiment on the evolution of seepage capacity during the injection and production process at the scale of loose sandstone reservoirs: According to the experimental requirements, select the appropriate well structure, install the screen to be evaluated into the screen tube unit, and assemble it with the well wall simulation unit. Fill the annular space between the screen tube unit and the well wall simulation unit with the filling medium to be evaluated to form the basic configuration of the composite sand control structure. According to the pre-designed scheme, pressure sensors are arranged on the pressure chamber wall, the composite sand control unit, and the boundary area between the reservoir and the squeezed filling layer to monitor the pressure in different areas. Subsequently, the formation sand required for the experiment was filled into the pressure chamber, and different filling molds were selected according to the simulated filling pattern, or the required gaps were artificially created according to the experimental requirements. The assembled composite sand control unit was then installed into the high-pressure resistant visual reservoir simulation unit. After the formation sand was fully consolidated, the device was sealed as a whole and the experiment was started. During the experiment, a simulated filling pump set was first connected to simulate the gravel filling process, squeezing the filling medium into the void. The gravel filling situation was observed and recorded in real time through the image acquisition unit. Then, the displacement pump set was replaced, and displacement fluid with tracer was used for displacement. The occurrence and development of formation sand intrusion into the filling layer at the interface between the reservoir and the squeezed filling layer were observed and recorded in real time through the image acquisition unit. By combining pressure data collected by pressure sensors placed at different locations, the evolution of seepage capacity in the reservoir, squeezed filling layer and wellbore is further analyzed, providing experimental basis for evaluating the effect of squeezed filling and its impact on sand production behavior.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention constructs a high-pressure resistant, transparent, and visual reservoir simulation device by setting a viewing window on the side wall of the pressure chamber and forming an observation port by axially cutting one side of the side wall of the composite sand control unit. The observation port is sealed to the viewing window, thus realizing real-time visual observation of key processes such as reservoir sand production, sand migration, sand control layer blockage, and mixed zone formation. This overcomes the limitations of traditional experimental devices that rely on indirect inference from macroscopic parameters. At the same time, it can flexibly construct a near-wellbore composite sand control system of reservoir and sand control layer, and supports switching between multiple well structures such as vertical wells, horizontal wells, and deviated wells. It can realistically simulate sand production and sand control behavior under complex wellbore conditions. In addition, it can simulate the construction process of gravel filling and observe and record the filling morphology in real time. During the experiment, multi-source data such as pressure, differential pressure, flow rate, and images can be simultaneously collected at different locations in the reservoir and sand control layer. This not only allows for the determination of critical sand production conditions and the evolution of sand control layer blockage, but also enables the monitoring of differential pressure changes in different sections of the reservoir, sand control layer, and their composite system. This further allows for the study of the dynamic changes in permeability during sand production and blockage processes, revealing the seepage coupling relationship between the reservoir and sand control layer. Through these experimental methods, quantitative evaluation of sand production and sand control behavior can be achieved, significantly improving the precision and reliability of related research. This invention has a wide range of applications and strong controllability of experimental conditions, providing intuitive and quantifiable experimental evidence for sand control process selection, parameter optimization, and production system control, and has good engineering application value. Attached Figure Description

[0024] Figure 1 A schematic diagram of a high-pressure-resistant, visualized reservoir simulation unit structure; Figure 2 This is a schematic diagram of the composite sand control unit. Figure 3 Schematic diagrams of different filling methods for the simulation unit of the outer filling layer of the wellbore; Figure 4 A schematic diagram of the structure of an experimental simulation system for the entire series of gravel backfilling construction and production stages, for visualization purposes; Figure 5 Schematic diagram of different filling forms to simulate gravel backfilling for sand control; Figure 6 This is a schematic diagram simulating reservoir filling under multi-level combination conditions; Figure 7 A schematic diagram of the experimental simulation system for simulating the extrusion filling process; Figure 8 A schematic diagram showing the location of the uniform inflow channel; Figure 9 This is a schematic diagram of the screen holder. Figure 10 This is a schematic diagram of the uniform inflow channel. Figure 11 This is a schematic diagram showing the arrangement of the pressure sensors; The diagram shows a 1000 fluid displacement unit, a 2000 extrusion filling pump unit, and a 3000 data measurement and acquisition unit. 100 viewing windows, 200 observation ports, 300 screen tube units, 400 wellbore simulation units; 1. Pressure chamber; 101. Inlet; 102. Outlet; 103. Sensor mounting hole; 2 Control valve, 3 Flow meter, 4 Base pipe, 5 Screen, 6 Filling mold, 7 Divider plate, 8 Microscopic image acquisition device, 9 Pressure sensor, 10 Vertical wellbore, 11 Horizontal wellbore, 12 Inclined wellbore, 13 Branch well, 14 Depletion mold, 15 Extrusion filling mold, 16 Fracturing filling mold, 17 Uniform inflow channel, 171 Mesh plate, 18 Production collection tank, 19 Solid-liquid separation device, 20 Filling medium supply container, 21 Simulated filling pump unit. Detailed Implementation

[0025] The invention will be described in more detail below with reference to examples.

[0026] like Figures 1-11 As shown, a full-stage experimental simulation system for the construction and production of gravel backfilling includes a high-pressure resistant visual reservoir simulation unit, a simulated multi-layer separation device, a composite sand control unit, a fluid displacement unit 1000, a squeeze backfilling pump injection unit 2000, a wellbore external backfilling simulation unit, a production collection and separation unit, an image acquisition unit, and a data measurement and acquisition unit 3000.

[0027] like Figure 1As shown, the high-pressure resistant visual reservoir simulation unit includes a pressure chamber 1 and a simulated reservoir medium disposed within the pressure chamber 1 for simulating the reservoir. The pressure chamber 1 has inlets 101 on its side walls and bottom, and an outlet 102 on its top. The high-pressure resistant visual reservoir simulation unit is used to simulate the reservoir.

[0028] The inlet 101 is connected to the fluid displacement unit through a pipeline, and a control valve 2 and a flow meter 3 are installed on the pipeline corresponding to each inlet 101.

[0029] The lower end of the outlet 102 is connected to the composite sand control unit installed in the pressure chamber 1.

[0030] The pressure chamber 1 is provided with sensor mounting holes 103, which are located at the bottom and on the left and right side walls of the pressure chamber 1, respectively. A viewing window 100 is provided on the front side wall of the pressure chamber 1. The viewing window 100 is arranged along the longitudinal section of the pressure chamber 1.

[0031] like Figure 1 As shown, the pressure chamber 1 has a rectangular parallelepiped structure with dimensions of 60cm × 40cm × 15cm. The chamber employs a sealed, pressure-resistant design with a maximum pressure resistance of 10MPa. Three inlet holes are provided on each of the left and right sides and the lower end of the pressure chamber 1. These inlet holes are connected to the fluid displacement unit via pipelines to simulate multi-directional flow conditions in the formation. Simultaneously, a uniform inlet groove is provided 1cm from the inner wall of the chamber. The specific structure is shown in the attached figure. Figure 8 As shown, to reduce the local high-speed jet effect, a more uniform flow field distribution is formed before the fluid enters the reservoir simulation medium. Three outlets are set on the upper end face of the cavity, and are connected to the composite sand control unit through corresponding interfaces to simulate the wellbore production process.

[0032] To monitor pressure changes at different locations within the reservoir and sand control layer, two pressure sensor mounting positions are installed on each of the left and right end faces of the chamber, and four pressure sensor mounting positions are installed on the upper end face. The embedment position of each pressure sensor 9 can be adjusted according to experimental requirements, thereby enabling segmented monitoring of pressure and differential pressure changes within the reservoir, before and after the sand control layer, and in different sections of the composite system. The outlet end of the chamber is connected to a collection tank via a pipeline for collecting produced fluids and subsequent solid-liquid separation.

[0033] One sidewall of the composite sand control unit is axially cut to form an observation port 200, which is sealed to a viewing window 100. This is used for real-time visual observation and recording of formation sand intrusion, migration of the sand control layer front, and the formation of the mixing zone. The composite sand control unit is placed in a simulated reservoir, and different sand control completion methods can be simulated by changing different components. Figure 5As shown, simulations can be performed for annular gravel filling (with only composite sand control units), non-uniform extrusion filling (with non-uniform radial length distribution of the extrusion filling mold), uniform extrusion filling (with uniform radial length distribution of the extrusion filling mold), high-strength uniform extrusion filling (with uniform radial length distribution of the extrusion filling mold and radial length greater than the threshold), horizontal fracture fracturing filling (with a split conical structure for the fracturing filling mold), and vertical fracture fracturing filling (with an integrated conical structure for the fracturing filling mold). For different working conditions, only the corresponding wellbore external filling mold needs to be replaced, and the filling method and shape can be changed.

[0034] like Figure 2 As shown, the composite sand control unit includes a screen pipe unit 300 and a well wall simulation unit 400. The screen pipe unit 300 is coaxially arranged inside the well wall simulation unit 400, and an annulus is provided between the screen pipe unit and the well wall simulation unit, which is filled with sand control medium. The well wall simulation unit 400 is used to simulate a wellbore.

[0035] The wellbore simulation unit is used to simulate different well completion structures, and the screen unit includes a base pipe 4 and a detachable screen 5 set on the outside of the base pipe 4.

[0036] The wellbore external filling layer simulation unit includes a semi-enclosed filling mold 6 formed of a metal filter screen. The opening side of the filling mold 6 is connected to the side wall of the composite sand control unit. The filling mold 6 is used to fill the sand control medium to simulate the sand control layer.

[0037] like Figure 6 As shown, the simulated multi-layer separation device includes a detachable partition plate 7 installed inside the pressure chamber 1. Specifically, partition plates 7 of different sizes and positions can be configured inside the cavity of the pressure chamber 1. The partition plates 7 are detachable and can be designed in conjunction with different well types to simulate caprock or multi-layer reservoir combination conditions, thereby realizing experimental simulation of reservoir conditions with different layer combinations.

[0038] The fluid displacement unit 1000 is used to provide a stable displacement medium to the high-pressure resistant visualization reservoir simulation unit through the inlet 101. The displacement method can be set to constant flow displacement or constant pressure difference displacement.

[0039] like Figure 7As shown, the squeeze-fill pumping unit 2000 is used to provide filling medium to the high-pressure visual reservoir simulation unit through the outlet 102 to simulate the high-pressure filling process. Specifically, the squeeze-fill pumping unit 2000 includes a filling medium supply container 20 and a simulation filling pump group unit 21 connected in sequence to the outlet 102. The simulation filling pump group unit 21 is connected to the outlet 102 through a filling medium injection pipeline. The filling medium supply container 20 is installed on the filling medium injection pipeline, and a valve group control structure is installed on the filling medium injection pipeline. The simulation filling pump group unit and the filling medium supply container pump the filling medium from the pipeline to the simulated reservoir medium to simulate the high-pressure filling process. A control valve 2 and a flow meter 3 are installed on the pipeline between the squeeze-fill pumping unit 2000 and the outlet 102.

[0040] The output collection and separation unit is connected to the composite sand control unit through the outlet 102. It is used to collect the solid and liquid produced by the composite sand control unit during the experiment and to perform solid-liquid separation. A control valve 2 and a flow meter 3 are installed on the pipeline between the outlet 102 and the output collection and separation unit.

[0041] The image acquisition unit includes a microscopic image acquisition device 8 set at the viewing window 100, which is used to synchronously record the migration of reservoir sand bodies, sand layer blockage, and the evolution of the mixing zone.

[0042] The data measurement and acquisition unit 3000 includes a pressure sensor 9 installed in the simulated reservoir medium through a sensor mounting hole 103 and a flow meter 3 on the pipeline, used to collect pressure, differential pressure, and flow information at different locations in the reservoir and sand control structure in real time. In this embodiment, the pressure sensor 9 is a probe structure. The data acquisition module is located in a computer for data acquisition and processing.

[0043] Both the screen tube unit and the well wall simulation unit are half-sectioned from the axis center.

[0044] As attached Figure 4 and Figure 8 As shown, the wellbore simulation unit includes a vertical wellbore 10, a horizontal wellbore 11, an inclined wellbore 12, and a branch well 13, which can be replaced according to experimental requirements.

[0045] The composite sand control unit includes a screen pipe unit and a well wall simulation unit, both of which are detachable structures, making it easy to change different sand control methods and structural parameters according to experimental requirements.

[0046] The screen tube unit is located in the inner layer, with an outer diameter of 6 cm and a length of 30 cm. It is closed at the bottom and its outlet mates with the reservoir simulation unit. Six screen holders are evenly arranged on the outer wall of the base tube 4. These screen holders have a spring-loaded clamp structure, fixed at the top and open at the bottom. The specific structure is shown in the attached figure. Figure 9As shown, the screen medium is used to fix the screen medium. The type and precision of the screen medium can be changed according to experimental requirements. The base tube 4 has inlets evenly spaced 1 cm apart along the axial direction between adjacent clamps. The inlet diameter is preferably 1 cm, used to simulate the flow conditions of the screen tube unit. The specific structure is shown in the attached figure. Figure 2 As shown.

[0047] The wellbore simulation unit is located outside the screen tube unit and is used to simulate the wellbore or casing structure. Its inner diameter can be selected from different specifications such as 8cm, 10cm, 12cm, or 14cm, with a length of 30cm. It is closed at the bottom, with an assembly female connector at the top opening, which mates with the assembly male connector on the screen tube unit (the assembly male and female connectors have a screw and nut-like structure for easy assembly and fixation). The wellbore simulation unit has three rows of evenly arranged through holes along the axial direction on its wall surface. The through hole diameter is 2cm, and the spacing between adjacent through holes is 1cm. This is used to simulate the flow inflow into the wellbore and the fluid distribution characteristics under different filling conditions. The specific structure is shown in the attached figure. Figure 2 As shown, a sand-controlling and filling space is formed between the screen unit and the wellbore simulation unit. This sand-controlling and filling space can be filled with gravel, ceramsite, or other sand-controlling media, simulating annular filling.

[0048] like Figure 3 As shown, the wellbore external filling layer simulation unit includes a void mold 14, a compression filling mold 15, and a fracturing filling mold 16.

[0049] The extrusion filling mold 15 and the fracturing filling mold 16 are filled with sand-proof medium.

[0050] The wellbore external filling simulation unit is equipped with a series of annular filling molds of different thicknesses and radii, including extrusion filling molds and fracturing filling molds, the specific structures of which are shown in the attached figure. Figure 3As shown. The extrusion filling mold is a 1 / 4-circular mold made of 15-mesh metal filter. The inner ring radius matches the wellbore simulation unit. The side matching the wellbore simulation unit does not have a filter (the main function of this mold is to ensure the filling shape; omitting the filter reduces flow resistance; it does not need to be connected to the wellbore simulation unit, as long as the dimensions match and a space for gravel filling is formed between them). The filter is placed on the side in contact with the simulated formation, i.e., the simulated reservoir medium. The fracturing filling mold is a semi-pyramidal mold equipped with a series of different sizes to simulate fracturing fractures of different sizes, and can simulate both horizontal and vertical fractures. By combining extrusion filling molds of different radii and filling them with gravel, the effects of different filling methods and filling intensities on sand control can be studied. (The sand control filling space formed between the screen unit and the wellbore simulation unit is mainly filled with two types of media: one is screen media, which is fixed by a screen holder and closely attached to the base pipe; the other is filling media, which is filled in the annulus, i.e., between the screen and the wellbore simulation unit, with sand control media such as quartz sand and ceramsite. The two together simulate the annulus circulation filling sand control method. The wellbore external filling simulation unit fills the formation with quartz sand and ceramsite for sand control. Extrusion filling is when sand production creates an approximately annular void area in the formation, squeezing the filling medium into the formation. Fracturing filling is when fractures are created in the formation, and the filling medium is squeezed into the fractures to prevent fracture closure, thus playing a role in sand control and improving conductivity.)

[0051] By selecting different wellbore inner diameters, different filling media and filling thicknesses, the effects of different filling radii, different filling intensities and different combinations of sand control parameters on sand production and sand control behavior can be simulated, thereby constructing a multi-layer composite sand control system of "reservoir-mixed zone-sand control layer".

[0052] like Figure 4 and Figure 10 As shown, the pressure chamber 1 has uniform inflow channels 17 connected to the inflow port 101 on its side wall and bottom. The uniform inflow channels 17 are provided with mesh plates 171 that are parallel to and spaced apart from the inner wall of the pressure chamber 1.

[0053] The fluid displacement unit 1000 includes a horizontal flow pump and an intermediate container.

[0054] The advection pump is connected to the inlet 101 through an intermediate container. A piston is installed inside the intermediate container, which divides the inner cavity of the intermediate container into a fluid cavity and a drive cavity. The advection pump is connected to the drive cavity, and the fluid cavity is connected to the inlet 101.

[0055] The output collection and separation unit includes an output collection tank 18 and a solid-liquid separation device 19 connected in sequence to the outlet 102. It is used to collect the solid and liquid produced during the experiment and separate them to obtain the sand passing rate.

[0056] In practice, based on the physical properties of the target reservoir and the simulated well completion method, the appropriate composite sand control unit and its supporting devices are selected. A screen medium matching the experimental requirements is installed in the screen unit and combined with the wellbore simulation unit. Then, gravel of the target particle size is filled between the screen unit and the wellbore simulation unit to simulate the screen-gravel filling sand control completion method. As needed for the experiment, pressure sensors are placed at corresponding locations in the simulated reservoir medium and sand control structure (composite sand control unit and wellbore external filling layer simulation unit) to monitor the pressure in different areas. Simultaneously, based on the target reservoir structural characteristics and the simulated wellbore location, a simulated caprock, i.e., a partition plate, is arranged inside the pressure chamber 1 and filled with formation sand to complete the reservoir model construction.

[0057] During the experiment, fluid was injected into the simulated reservoir medium through inlets evenly distributed around the cavity to simulate seepage conditions from different directions in the formation. Pressure sensors placed at different locations in the reservoir and sand control layer were used to monitor pressure changes in each area in real time and calculate the pressure difference characteristics of different sections. If necessary, the positions of pressure sensors could be added or adjusted using preset sensor orifice locations to achieve refined monitoring of pressure changes in various parts of the simulated reservoir medium and sand control layer.

[0058] The core advantage of this invention lies in its ability to intuitively observe and quantitatively analyze reservoir sand production, sand control layer blockage, and the evolution of mixed zones by constructing a transparent, high-pressure, and visualized reservoir simulation device and a composite sand control structure. The system employs a modular design, allowing for flexible combinations of different reservoir conditions, well types, and sand control completion methods. It also simultaneously monitors changes in pressure and permeability at each stage, providing reliable and visualized experimental data for sand control structure optimization and process parameter selection.

[0059] A visualized full-series gravel backfilling construction and production full-stage experimental simulation method, using the visualized full-series gravel backfilling construction and production full-stage experimental simulation system of this embodiment, includes the following steps: S1. Reservoir Media Preparation and Loading The simulated reservoir medium is configured according to the target reservoir type. The simulated reservoir medium is artificial formation sand or equivalent reservoir filling material. The particle size, cementation strength and water content parameters of the filling medium are controlled to meet the experimental requirements.

[0060] The simulated reservoir medium was filled into pressure chamber 1.

[0061] The simulated reservoir medium is uniformly arranged in the pressure chamber 1, or layered according to the experimental purpose, to simulate different layer combinations or caprock conditions.

[0062] S2, Composite Sand Control Unit Configuration Select the composite sand control unit according to the experimental requirements, and determine the well type and corresponding screen structure parameters, including screen type, screen accuracy and inlet distribution.

[0063] Subsequently, sand-controlling medium is filled into the annular space between the screen tube unit and the well wall simulation unit. The sand-controlling medium is gravel, ceramsite, or other equivalent materials. Different forms of sand-controlling filling structures are constructed by adjusting the inner diameter of the well wall simulation unit, selecting different filling mold combinations, filling medium types, and filling thicknesses.

[0064] The annular structure is a space between the wellbore (wellwall simulation unit) and the screen unit, to... Figure 4 For example, the annular layer is the brown part in the middle, which is used to fill sand control media such as ceramic particles; the radius of the internal screen tube unit remains unchanged because a series of well wall simulation units with different radii will be configured. By expanding and shrinking the radius of the well wall simulation units, the radius of the annulus will also change accordingly, thereby achieving different filling thicknesses.

[0065] S3. Setting Displacement Conditions and Starting the Experiment Displacement medium is injected into pressure chamber 1 through the fluid displacement unit.

[0066] The displacement method was set to constant flow displacement or constant pressure difference displacement to simulate reservoir flow conditions under different production regimes.

[0067] During the experiment, the data acquisition unit 3000 simultaneously recorded changes in pressure, differential pressure, and flow rate within the reservoir, wellbore, and sand control structure. For example... Figure 11 Taking the measuring point at the wellbore and the measuring point at the interface as an example, the pressure difference between the two is the pressure difference of the squeezed filling layer. Each section is arranged in different ways according to different experimental requirements to test the pressure difference of the squeezed filling layer, the annular filling layer, and different locations in the reservoir.

[0068] S4. Visual observation and data acquisition of the sand production process The image acquisition unit, located outside the viewing window 100, records in real time the process of reservoir sand body exfoliation, migration path, mixing zone formation, sand-prevention layer blockage, and evolution.

[0069] By combining data collected by pressure sensors placed at different locations in the reservoir and sand control layer, the pressure response and differential pressure changes at various locations in the reservoir, wellbore-screen structure, and sand control filling layer are analyzed simultaneously, thus achieving the correspondence between microscopic images and macroscopic seepage parameters.

[0070] S5. Evaluation of Output Collection and Sand Control Performance By using the production collection and separation unit located at one end of the outlet 102, the produced fluid is subjected to solid-liquid separation and the carried formation sand is collected, and the sand output at different experimental stages is statistically analyzed.

[0071] By combining pressure, differential pressure, flow rate, and image data, a comprehensive evaluation is conducted on the degree of blockage of the sand control structure, sand particle penetration behavior, changes in the thickness of the mixed zone, and the evolution of the seepage capacity of the composite system.

[0072] The visualization-based full-series gravel backfilling construction and production full-stage experimental simulation system of this embodiment can be used to conduct sand control effect evaluation and parameter optimization simulation experiments of different sand control methods in loose sandstone reservoirs, simulation experiments of the squeezing backfilling process and post-backfilling production process of loose sandstone depleted reservoirs, and simulation experiments of the evolution of seepage capacity in the injection and production process of loose sandstone reservoirs at the scale.

[0073] Experimental Procedure (The following are the main representative experiments that can be performed): (1) Evaluation of sand control effect of different sand control methods in loose sandstone reservoirs and simulation experiment of parameter optimization Simulated sand control methods are shown in the attached figure. Figure 5 As shown, this example uses annular circulating gravel filling and uniform compression filling.

[0074] First, an evaluation experiment of the independent screen pipe sand control method was conducted. Based on the experimental requirements, a suitable well structure was selected, and the screen to be evaluated was installed in the screen pipe unit, combined with the wellbore simulation unit to form a complete composite sand control unit (the independent screen pipe sand control method is a sand control method that does not fill the annulus with gravel. The wellbore and screen pipe combination mentioned here simulates the perforation completion method; if open-hole completion is used, the wellbore simulation unit does not need to be assembled). Then, it was installed as a whole in the designated position of the high-pressure visual reservoir simulation unit. Pressure sensors (a bendable iron pipe that transmits pressure through water) were placed around the composite sand control unit and near the wall of the pressure chamber 1. The placement method and main purpose depend on the experimental objective; if the goal is to monitor the permeability change of the sand control layer, the pressure sensors are placed at the beginning and end points of the sand control layer; if the goal is to monitor the permeability change of a specific reservoir section, they are placed at the corresponding positions). Formation sand was filled according to the experimental requirements and consolidated (a consolidating agent was added to the experimental formation sand to bind it together, simulating the strength of the reservoir rock), thus completing the experimental model construction. The sand control layer will vary depending on the simulated sand control method, such as... Figure 5 As shown, for the annular gravel packing mode, the sand control layer refers to the gravel and screen unit filled in the annulus; for the compression packing mode, the sand control layer refers to the compression gravel packing layer outside the wellbore, the gravel packing layer and screen unit filled in the annulus, and so on.

[0075] After the experiment began, the pressure changes at different locations in the reservoir and sand control layer were monitored in real time using the data measurement and acquisition unit. Simultaneously, the image acquisition unit continuously recorded the reservoir morphology evolution process, focusing on observing and recording the formation and development of various depletion patterns. When the pressure increase at the sand control layer was less than a set threshold, i.e., significantly reduced or even stabilized (the recorded pressure change rate over time was less than 0.3, considered a significant reduction or even stabilization), it indicated that the sand control layer blockage process was approaching equilibrium. At this point, the inlet pressure, the pressure outside the sand control layer, and the outlet pressure were combined to analyze the permeability changes and seepage capacity evolution of the reservoir and sand control layer. (Based on the recorded pressure and flow rate, the permeability of a certain segment was calculated using Darcy's formula for radial flow (currently available technology). The permeability changes were analyzed to assess the seepage capacity changes in that segment.) The flow performance of screen 5 was evaluated. The inlet pressure was the reading of a pressure sensor placed near the "pressure chamber wall" mentioned above; the pressure outside the sand control layer was... Figure 11 The pressure of the sensors placed at the interface.

[0076] In addition, solid-liquid separation was performed on the produced fluid through the production collection and separation unit, and the proportion of formation sand penetrating the sand control structure, i.e., the composite sand control unit (sand passage rate), was calculated to comprehensively evaluate the sand-blocking capacity of screen 5. While maintaining other experimental conditions, the above experiments were repeated with screens of different types or precision to compare and analyze the performance of different screens in terms of seepage capacity changes and sand passage rates.

[0077] The second step involves conducting an evaluation experiment on the annular circulation gravel filling sand control method. Based on the experimental requirements, a suitable well configuration is selected, and the screen 5 to be evaluated is installed in the screen tube unit, combined with the wellbore simulation unit to form a complete composite sand control unit. Then, the annulus between the two units is filled with the gravel to be evaluated, and subsequently, the entire unit is installed at the designated location in the high-pressure resistant visual reservoir simulation unit.

[0078] Pressure sensors were arranged around the composite sand control unit and near the wall of the pressure chamber 1. The formation sand was filled and consolidated according to the experimental requirements to complete the construction of the experimental model.

[0079] Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand passing rate. Then, we conducted parallel experiments with gravel of different precision and types to compare and analyze the performance of different screens and gravel in terms of seepage capacity changes and sand passing rate.

[0080] The third step involves conducting an evaluation experiment on the uniform compression filling sand control method. Based on the experimental requirements, a suitable well structure is selected, and the screen 5 to be evaluated is installed in the screen tube unit, combined with the well wall simulation unit to form a complete composite sand control unit. Then, the annulus between the two units is filled with the gravel to be evaluated.

[0081] Based on the proportional relationship between the simulated well and the wellbore simulation unit, a suitable extrusion filling mold is selected and placed in the simulated reservoir after conversion (the conversion here refers to the extrusion radius of the extrusion filling, which is calculated using the similarity criterion. By ensuring the similarity in scale between the wellbore mold and the field well, the experimental extrusion filling radius can be calculated, and the appropriate mold is selected accordingly). The mold is then filled with gravel of the same precision and type from the annulus (during field construction, expanded clay is pressed from the annulus into the reservoir's voids (the extrusion process), therefore the annulus and the extrusion layer outside the wellbore are a type of filling medium). The entire model is then installed at the designated location within the high-pressure resistant visual reservoir simulation unit. Pressure sensors are placed around the composite sand control unit and near the pressure chamber wall, and formation sand is filled and consolidated according to experimental requirements, completing the experimental model construction.

[0082] Based on the dimensional relationship between the field well and the simulated well wall unit, the compression filling range is recalculated. Specifically, both the field well and the experimental model are approximated as radial inflow along a cylindrical sidewall. The equivalent linear scaling factor λ is determined by the ratio of the inflow area of ​​the field well to that of the experimental model. L =(A f / A m ) 1 / 2 A f A is the inflow side area of ​​the field well (calculated using the cylindrical side area formula based on the wellbore radius and production section length). m The inflow lateral area of ​​the experimental well model (that is, the lateral area of ​​the wellbore mold, in this embodiment, the lateral area of ​​a semi-cylinder) is given by the on-site design extrusion filling radius R. pf The corresponding radius R in the experimental model pm According to R pm =R pf / λ L The conversion is performed to determine the size of the extrusion filling mold.

[0083] Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand flow rate. Then, we conducted parallel experiments with gravel of different precision and types to compare and analyze the performance of different gravel in terms of seepage capacity changes and sand flow rate.

[0084] Finally, by comprehensively comparing different sand control methods (these are the independent screen units, annular filling, and squeeze filling mentioned above) and different sand control parameters, the changes in seepage capacity and sand flow of the screen units, filling layers, and the overall reservoir and sand control layer can be determined, thus identifying the most suitable sand control method and parameters for the site conditions. The sand control layer includes screen units and gravel filling layers; monitoring changes in seepage capacity is to identify where blockage mainly occurs.

[0085] (2) Simulation experiment to evaluate the sand control effect of different filling media types and precision under multi-layer combination conditions like Figure 6 As shown, based on the stratigraphic combination characteristics of the target reservoir, different stratigraphic layers are separated using partition plate 7. Pressure sensors are placed near the composite sand control unit of each sub-layer and on the wall of the pressure chamber 1 to monitor the pressure difference changes of each layer. According to the experimental requirements, the appropriate well structure is selected, and the screens 5 to be evaluated in each sub-layer are assembled into the screen tube unit and then assembled with the wellbore simulation unit. Subsequently, the annular space between the screen tube unit and the wellbore simulation unit is filled with the filling medium to be evaluated to construct the composite sand control unit, which is then installed as a whole at the designated position of the high-pressure resistant visual reservoir simulation unit.

[0086] Based on the specific data of different stratigraphic sand layers on site, corresponding simulated stratigraphic sands were filled into four sub-layers, as shown in the attached diagram. Figure 6 As shown, the formation sand was consolidated to complete the overall construction of the experimental model.

[0087] During the experiment, the inlet flow rate of each sub-layer was set according to the production allocation of each sub-layer. When the pressure changes at the sand control layer of each layer tended to stabilize and the blockage process reached a relatively balanced state, the permeability changes and seepage capacity evolution of each sub-layer reservoir and sand control layer were analyzed by combining the inlet pressure, the pressure outside the sand control layer, and the outlet pressure data to evaluate the flow performance of the gravel layer. At the same time, the sand flow rate of each layer was obtained by collecting formation sand inside the screen tube units of different layers. Finally, the sand-blocking capacity of the gravel layer was comprehensively evaluated according to the evaluation method (the permeability loss of the sand control layer was calculated based on the pressure difference change, and the sand-blocking rate of the gravel layer was calculated based on the sand flow rate; these two indicators were used as the main reference basis to compare the sand-blocking effect of the gravel layer on the simulated formation sand).

[0088] (3) Simulation experiment on the evolution of seepage capacity of the composite system in the injection and production process at the scale of loose sandstone reservoir According to the experimental requirements, a suitable well structure was selected. The screen 5 to be evaluated was installed into the screen tube unit and assembled with the well wall simulation unit. The annular space between the screen tube unit and the well wall simulation unit was filled with the filling medium to be evaluated, forming the basic configuration of the composite sand control structure. According to the pre-designed scheme, pressure sensors were arranged on the wall of the pressure chamber 1, at the location of the composite sand control unit, and at the boundary between the reservoir and the squeezed filling layer (see...). Figure 11 The boundary area between the reservoir and the extrusion-filled layer (the blank area in the diagram and the yellow simulated formation area outside) is used to monitor the pressure in different areas.

[0089] Subsequently, the required formation sand is filled into the pressure chamber 1, and different filling molds 6 are selected according to the simulated filling pattern, or the required gaps are artificially created according to the experimental requirements (such as...). Figure 11 As shown in the diagram, the assembled composite sand control unit is installed into the high-pressure-resistant visual reservoir simulation unit. After the formation sand has fully solidified, the device is sealed and the experiment is started.

[0090] As attached Figure 7 As shown, during the experiment, the simulated filling pump unit 21 was first connected to simulate the gravel filling process. The filling medium was squeezed into the void (the medium was not filled into the filling mold or void; the equipment was assembled directly to start the experiment, and the filling medium was directly squeezed into the mold or void by the filling pump unit). The gravel filling situation was observed and recorded in real time through the image acquisition unit. Then, the displacement pump unit was replaced, and displacement fluid with tracer was used for displacement. The occurrence and development of formation sand intrusion into the filling layer at the interface between the reservoir and the squeezed filling layer were observed and recorded in real time through the image acquisition unit. Combined with the pressure data collected by pressure sensors placed at different locations, the reservoir, squeezed filling layer and wellbore interior (wellbore interior refers to...) can be further analyzed. Figure 2 The evolution law of seepage capacity of the device after the right side is completed and the gravel is filled in the annular filling layer (including the annular filling gravel layer, the screen tube unit, and the inside of the screen tube unit) provides experimental basis for evaluating the squeezing filling effect and its impact on sand discharge behavior.

Claims

1. A visualized experimental simulation system for the entire process of gravel backfilling construction and production, characterized in that: It includes a high-pressure resistant visualization reservoir simulation unit, a simulated multi-layer separation device, a composite sand control unit, a fluid displacement unit (1000), a squeeze filling pump injection unit (2000), a wellbore external filling layer simulation unit, a production collection and separation unit, an image acquisition unit, and a data measurement and acquisition unit (3000). The high-pressure resistant visualization reservoir simulation unit includes a pressure chamber (1) and a simulated reservoir medium set in the pressure chamber (1) for simulating the reservoir. The pressure chamber (1) is provided with an inlet (101) on its side wall and bottom, and an outlet (102) is provided on its top. The inlet (101) is connected to the fluid displacement unit (1000) through a pipeline, and a control valve (2) and a flow meter (3) are provided on the pipeline corresponding to each inlet (101). The lower end of the outlet (102) is connected to the composite sand control unit installed in the pressure chamber (1); The pressure chamber (1) is provided with a sensor mounting hole (103), and the side wall of the pressure chamber (1) is provided with a viewing window (100). The sidewall of the composite sand control unit is cut open along the axial direction to form an observation port (200), and the observation port (200) is sealed to the viewing window (100). The composite sand control unit includes a screen pipe unit (300) and a well wall simulation unit (400). The screen pipe unit (300) is coaxially arranged inside the well wall simulation unit (400). An annular space is provided between the screen pipe unit (300) and the well wall simulation unit (400), and the annular space is filled with sand control medium. The wellbore simulation unit (400) is used to simulate different well completion structures. The screen pipe unit (300) includes a base pipe (4) and a detachable screen (5) set on the outside of the base pipe (4). The wellbore external filling layer simulation unit includes a semi-enclosed filling mold (6) formed by a metal filter screen. The opening side of the filling mold (6) is connected to the side wall of the composite sand control unit. The filling mold (6) is used to fill the sand control medium. The simulated multi-layer partition device includes a detachable partition plate (7) installed inside the pressure chamber (1). The fluid displacement unit (1000) is used to provide displacement medium to the high-pressure-resistant visualization reservoir simulation unit through the inlet (101); The extrusion filling pump unit (2000) is used to provide filling medium to the high-pressure visual reservoir simulation unit through the outlet (102); The output collection and separation unit is connected to the composite sand control unit through the outlet (102) and is used to collect the solid and liquid produced by the composite sand control unit during the experiment and perform solid-liquid separation. A control valve (2) and a flow meter (3) are installed on the pipeline between the outlet (102) and the output collection and separation unit. The image acquisition unit includes a microscopic image acquisition device (8) disposed at the viewing window (100); The data measurement and acquisition unit (3000) includes a pressure sensor (9) installed in the simulated reservoir medium through a sensor mounting hole (103) and a flow meter (3) on the pipeline.

2. The visualized full-series gravel backfilling construction and production full-stage experimental simulation system according to claim 1, characterized in that: Both the screen tube unit (300) and the well wall simulation unit (400) are half-sectioned from the axis center.

3. The visualized full-series gravel backfilling construction and production full-stage experimental simulation system according to claim 1, characterized in that: The wellbore simulation unit includes a vertical wellbore (10), a horizontal wellbore (11), an inclined wellbore (12), and a branch well (13).

4. The visualized full-series gravel backfilling construction and production full-stage experimental simulation system according to claim 1, characterized in that: The wellbore external filling layer simulation unit includes a void mold (14), a compression filling mold (15), and a fracturing filling mold (16). The extrusion filling mold (15) and fracturing filling mold (16) are filled with sand-proof medium.

5. The visualized full-series gravel backfilling construction and production full-stage experimental simulation system according to claim 1, characterized in that: The pressure chamber (1) is provided with uniform inflow channels (17) connected to the inflow port (101) on its side wall and bottom. The uniform inflow channels (17) are provided with mesh plates (171) that are parallel to and spaced apart from the inner wall of the pressure chamber (1).

6. The visualized full-series gravel backfilling construction and production full-stage experimental simulation system according to claim 1, characterized in that: The fluid displacement unit (1000) includes a horizontal flow pump and an intermediate container; The advection pump is connected to the inlet (101) through an intermediate container. A piston is provided inside the intermediate container, which divides the inner cavity of the intermediate container into a fluid cavity and a drive cavity. The advection pump is connected to the drive cavity, and the fluid cavity is connected to the inlet (101). The output collection and separation unit includes an output collection tank (18) and a solid-liquid separation device (19) connected in sequence to the outlet (102). The extrusion filling pump unit (2000) includes a filling medium supply container (20) and a simulated filling pump unit (21) connected in sequence to the outlet (102).

7. A method for visualizing the entire process of gravel backfilling construction and production, employing the visualizing the entire process of gravel backfilling construction and production experimental simulation system as described in any one of claims 1 to 6, characterized in that... Includes the following steps: S1. Reservoir Media Preparation and Loading The simulated reservoir medium is configured according to the target reservoir type. The simulated reservoir medium is artificial formation sand or equivalent reservoir filling material. The particle size, cementation strength and water content parameters of the filling medium are controlled to meet the experimental requirements. The simulated reservoir medium was filled into the pressure chamber (1); The simulated reservoir medium is uniformly set in the pressure chamber (1), or layered according to the experimental purpose, in order to simulate different layer combinations or capping conditions. S2, Composite Sand Control Unit Configuration Select the composite sand control unit according to the experimental requirements, determine the well type and corresponding screen (5) structural parameters, including screen type, screen accuracy and inlet distribution form; Subsequently, sand-control medium is filled in the annular space between the screen tube unit (300) and the well wall simulation unit (400). The sand-control medium is gravel, ceramsite or other equivalent materials. Different forms of sand-control filling structures are constructed by adjusting the inner diameter of the well wall simulation unit, selecting different filling mold combinations, filling medium types and filling thicknesses. S3. Setting Displacement Conditions and Starting the Experiment Displacement medium is injected into the pressure chamber (1) through the fluid displacement unit; The displacement method is set to constant current displacement or constant pressure difference displacement to simulate reservoir flow conditions under different production regimes. During the experiment, the data measurement and acquisition unit (3000) simultaneously recorded the pressure, differential pressure, and flow rate changes inside the reservoir, in the wellbore, and at the sand control structure; S4. Visual observation and data acquisition of the sand production process The image acquisition unit located outside the viewing window (100) records in real time the process of reservoir sand body exfoliation, migration path, mixing zone formation, sand-proof layer blockage and evolution. By combining data collected by pressure sensors placed at different locations in the reservoir and sand control layer, the pressure response and differential pressure changes at various locations in the reservoir, wellbore-screen structure and sand control filling layer are analyzed simultaneously to achieve the correspondence between microscopic images and macroscopic seepage parameters. S5. Evaluation of Output Collection and Sand Control Performance By using the production collection and separation unit set at one end of the outlet (102), the produced fluid is separated into solid and liquid and the carried formation sand is collected, and the sand output at different experimental stages is statistically analyzed. By combining pressure, differential pressure, flow rate, and image data, a comprehensive evaluation is conducted on the degree of blockage of the sand control structure, sand particle penetration behavior, changes in the thickness of the mixed zone, and the evolution of the seepage capacity of the composite system.

8. The method for visualizing the entire process of gravel backfilling construction and production experimental simulation according to claim 7, characterized in that, This includes simulation experiments on the evaluation of sand control effectiveness and parameter optimization of different sand control methods in loose sandstone reservoirs. (1) Evaluation experiment of independent sieve tube sand control method Select the appropriate well structure according to the experimental requirements, and install the screen (5) to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, and then install it as a whole in the designated position of the high pressure resistant visual reservoir simulation unit; Pressure sensors were arranged around the composite sand control unit and near the wall of the pressure chamber (1), and the formation sand was filled and consolidated according to the experimental requirements to complete the construction of the experimental model. After the experiment began, the pressure changes at different locations of the reservoir and sand control layer were monitored in real time through the data measurement and acquisition unit. At the same time, the image acquisition unit was used to continuously record the reservoir morphology evolution process, focusing on observing and recording the formation and development of various depletion patterns. When the pressure increase at the sand control layer is less than the set threshold, it indicates that the sand control layer blockage process tends to be in equilibrium. At this time, the permeability change and seepage capacity evolution law of the reservoir and sand control layer are analyzed by combining the inlet pressure, the pressure outside the sand control layer and the outlet pressure, and the flow performance of the screen is evaluated. In addition, the produced fluid is separated into solid and liquid components by the production collection and separation unit, and the proportion of formation sand penetrating the sand control structure is calculated to comprehensively evaluate the sand-blocking capacity of the screen. While keeping other experimental conditions consistent, the above experiment was repeated with different types or precision sieves to compare and analyze the performance of different sieves in terms of seepage capacity and sand passage rate. (2) Evaluation experiment of annular circulating gravel filling sand control method Select the appropriate well structure according to the experimental requirements, and install the screen (5) to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, then fill the annulus between the two with the filling gravel to be evaluated, and then install it as a whole to the designated position of the high pressure-resistant visual reservoir simulation unit. Pressure sensors were arranged around the composite sand control unit and near the wall of the pressure chamber (1), and the formation sand was filled and consolidated according to the experimental requirements to complete the construction of the experimental model. Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand passing rate. Then, we conducted parallel experiments with gravel of different precision and types to compare and analyze the performance of different screens and gravel in terms of seepage capacity changes and sand passing rate. (3) Evaluation experiment of uniform extrusion filling method for sand prevention Select the appropriate well structure according to the experimental requirements, and install the screen (5) to be evaluated in the screen tube unit, combine it with the well wall simulation unit to form a complete composite sand control unit, and then fill the annulus between the two with the filling gravel to be evaluated. Based on the proportional relationship between the well to be simulated and the wellbore simulation unit, a suitable extrusion filling mold is selected and placed in the simulated reservoir after conversion. Gravel of the same precision and type as that in the annulus is filled into the mold. Then, the whole thing is installed in the designated position of the high-pressure resistant visual reservoir simulation unit. Pressure sensors are placed around the composite sand control unit and near the pressure chamber wall. Formation sand is filled in according to the experimental requirements and consolidation treatment is carried out to complete the construction of the experimental model. Following the same procedure, we recorded the pressure changes and sand control layer blockage of the composite system, analyzed the permeability changes of the reservoir and sand control layer and calculated the sand passing rate. Then, we conducted parallel experiments with different precision and types of gravel to compare and analyze the performance of different gravels in terms of seepage capacity changes and sand passing rate. Finally, by comprehensively comparing the changes in seepage capacity and sand passage of screen pipe units, filling layers, and the overall reservoir and sand control layer under different sand control methods and parameters, the most suitable sand control method and parameters for the field conditions can be obtained.

9. The method for visualizing the entire process of gravel backfilling construction and production in all stages, as described in claim 7, is characterized in that... This includes simulation experiments of the compression and filling process of loose sandstone depleted reservoirs and the production process after filling: Based on the stratigraphic combination characteristics of the target reservoir, the different stratigraphic layers are separated by a partition plate (7). Pressure sensors are placed near the composite sand control unit of each sub-layer and on the wall of the pressure chamber (1) to monitor the pressure difference changes of each layer. According to the experimental requirements, the appropriate well structure is selected, and the screens (5) to be evaluated in each sub-layer are assembled into the screen tube unit and assembled with the well wall simulation unit. Then, the filling medium to be evaluated is filled in the annular space between the screen tube unit and the well wall simulation unit to construct the composite sand control unit and install it as a whole into the designated position of the high-pressure visual reservoir simulation unit. Based on the specific data of different stratigraphic sands on site, corresponding simulated stratigraphic sands were filled into each layer, and the stratigraphic sands were consolidated to complete the overall construction of the experimental model. During the experiment, the inlet flow rate of each small layer was set according to the production of each small layer on site. When the pressure increase at the sand control layer of each layer was less than the set threshold, the permeability change and seepage capacity evolution of each small layer reservoir and sand control layer were analyzed by combining the inlet pressure, the pressure outside the sand control layer and the outlet pressure data to evaluate the flow performance of the gravel layer. Meanwhile, by collecting formation sand inside screen tube units at different strata, the sand throughput of each layer is obtained; finally, the sand-blocking capacity of the gravel layer is comprehensively evaluated.

10. The method for visualizing the entire process of gravel backfilling construction and production in all stages, as described in claim 7, is characterized in that... Including simulation experiments on the evolution of seepage capacity during injection and production at the scale of loose sandstone reservoirs: According to the experimental requirements, select the appropriate well structure, install the screen (5) to be evaluated into the screen tube unit, and complete the assembly with the well wall simulation unit. Fill the annular space between the screen tube unit and the well wall simulation unit with the filling medium to be evaluated to form the basic configuration of the composite sand control structure. According to the pre-designed scheme, pressure sensors are arranged on the wall of the pressure chamber (1), the position of the composite sand control unit, and the boundary area between the reservoir and the squeezed filling layer to monitor the pressure in different areas. Subsequently, the formation sand required for the experiment was filled into the pressure chamber (1), and according to the simulated filling pattern, different filling molds (6) were selected, or the required gaps were artificially created according to the experimental requirements. The assembled composite sand control unit was installed into the high-pressure visual reservoir simulation unit. After the formation sand was fully consolidated, the device was sealed as a whole and the experiment was started. During the experiment, a simulated filling pump set was first connected to simulate the gravel filling process, squeezing the filling medium into the void. The gravel filling situation was observed and recorded in real time through the image acquisition unit. Then, the displacement pump set was replaced, and displacement fluid with tracer was used for displacement. The occurrence and development of formation sand intrusion into the filling layer at the interface between the reservoir and the squeezed filling layer were observed and recorded in real time through the image acquisition unit. By combining pressure data collected by pressure sensors placed at different locations, the evolution of seepage capacity in the reservoir, squeezed filling layer and wellbore is further analyzed, providing experimental basis for evaluating the effect of squeezed filling and its impact on sand production behavior.

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