Visual fracturing filling sand prevention particle migration simulation experiment system and method

Abstract

The invention belongs to the technical field of petroleum engineering, and discloses a visual fracturing filling sand prevention particle migration simulation experiment system and method capable of truly simulating and visually observing the dynamic particle migration process. The system comprises a liquid storage stirring tank; the liquid injection system comprises a plurality of plunger pumps which are arranged in parallel with the liquid storage stirring tank and are respectively connected with the particle migration main body module; a gas injection system; the gas-liquid mixer is connected in series to the downstream of the liquid injection system and the gas injection system and is used for uniformly mixing gas-liquid two-phase fluid and then injecting the mixed fluid into the particle migration main body module; the visual particle migration main body module comprises a transparent circular particle migration model and / or a conical particle migration model, and a plurality of pressure measuring points are arranged in the transparent circular particle migration model and / or the conical particle migration model in the axial direction; the sand collecting and filtering system is arranged at the downstream of the particle migration main body module, realizes solid-liquid-gas three-phase separation through a pipeline and circulates a liquid phase to the liquid storage stirring tank; and the data acquisition and control system is used for monitoring pressure, flow and differential pressure data in real time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of petroleum engineering, and particularly relates to a visual fracturing and packing sand particle migration simulation experiment system and method. BACKGROUND

[0002] Loose sandstone reservoirs are widely developed in Bohai and other offshore oilfields, and have characteristics such as good permeability and poor cementation. During the production process, sand production in the reservoir becomes one of the problems hindering the development process, so carrying out sand control for oil and gas wells is an important response. Fracturing and packing technology combines hydraulic fracturing and gravel packing technology, penetrates the near-well area through fracturing cracks, improves the permeation area and permeability of the near-well area, and realizes the dual purposes of yield increase and sand control.

[0003] However, during production, particle migration is one of the important factors causing reservoir damage. After adopting the fracturing and packing sand control completion method, accompanied by the high-speed fluid carrying effect during production, the particles within a certain range around the well are gradually activated and migrate to the near-well area, causing the permeation channel to be blocked, resulting in a decrease in the permeability of the near-well area and a decrease in production. Especially for offshore loose sandstone fracturing and packing wells, the production is usually high, the fluid flow rate is fast, and the particle migration of the reservoir is more likely to be induced, forming serious blockage.

[0004] At present, for the fracturing and packing sand control method, the research on the particle migration in the near-well area and the reservoir still has the following problems:

[0005] (1) The influence law of oil and gas well production allocation, downhole fluid properties and reservoir properties on particle migration is not clear;

[0006] (2) The one-way flow displacement simulation of the particle migration dynamic process in the reservoir and the near-well area has not been fully visualized;

[0007] (3) The pressure and permeability change law in different particle migration areas is not clear, and the support ability for the optimization of sand control parameters is insufficient.

[0008] Therefore, an experimental system and method capable of truly simulating field conditions and realizing full-process visualization are urgently needed to provide accurate data for sand control process parameter optimization. SUMMARY

[0009] In order to truly simulate the particle migration dynamic process, intuitively observe the formation sand particle migration dynamic process, and characterize the dynamic change of permeability, the present application provides a visual fracturing and packing sand particle migration simulation experiment system and method.

[0010] The visualized fracturing packing sand particle migration simulation experiment system according to the present application comprises: a liquid storage stirring tank for preparing and temporarily storing experimental fluid; a liquid injection system comprising a plurality of plunger pumps arranged in parallel with the liquid storage stirring tank, each plunger pump being connected with a particle migration main module; a gas injection system connected with the particle migration main module; a gas-liquid mixer connected downstream of the liquid injection system and the gas injection system, for uniformly mixing gas-liquid two-phase fluid and then injecting the mixed fluid into the particle migration main module; the particle migration main module comprising a transparent circular particle migration model and / or a conical particle migration model, a plurality of pressure measuring points being arranged in the circular particle migration model and the conical particle migration model along the axial direction; a sand collection filter system arranged downstream of the particle migration main module, achieving solid-liquid-gas three-phase separation through a pipeline and recycling the liquid phase to the liquid storage stirring tank; and a data acquisition and control system for real-time monitoring of pressure, flow rate and pressure difference data.

[0011] Further, the circular particle migration model has a length of 50-100 cm, and the circular inner cavity has an inner diameter of 5-10 cm; the conical particle migration model has a length of 50-100 cm, and the ratio of the inner diameters of the inlet and the outlet of the conical inner cavity is 3:1 to 5:1, and the inner diameter of the inlet is 200-250 mm.

[0012] Further, the circular inner cavity and the conical inner cavity are respectively filled with compounded formation sand or compounded formation sand and proppant particles, for forming a reservoir section and / or a packing section; and a metal filter screen is arranged at the outlet of the circular inner cavity and the conical inner cavity.

[0013] Further, the liquid injection system comprises at least one large-displacement plunger pump and one small-displacement high-precision plunger pump arranged in parallel.

[0014] Further, the pressure measuring points are connected with pressure sensors through annular fastening mechanisms, for real-time monitoring of axial pressure difference.

[0015] Further, the sand collection filter system comprises a sand collection filter and a liquid collection tank, the liquid collection tank being connected with the liquid storage stirring tank through a reflux pipeline, to achieve closed-loop circulation of experimental fluid.

[0016] The visual fracturing packing sand particle migration simulation experiment method according to the application adopts the visual fracturing packing sand particle migration simulation experiment system, and comprises the following steps: step one: detecting the air tightness of the system with clean water and calibrating the empty pipe friction; step two: preparing the simulation reservoir fluid with specific viscosity and salinity in the liquid storage stirring tank; step three: according to the actual sand production condition and the formation sand property of the reservoir, configuring the simulation formation sand for experiment in the visual particle migration main module; step four: setting the gas and liquid flow, mixing through the gas-liquid mixer, and then injecting into the visual particle migration main module, collecting the pressure / differential pressure and flow data in real time, and recording the particle migration mode; step five: terminating the experiment when the injection pressure is stable, collecting and analyzing the formation sand in the sand collecting filter, so as to obtain the sand production characteristics and the permeability.

[0017] Further, the particle size median, uniformity coefficient, shale content and composition of the formation sand configured in step three are consistent with the target reservoir with a consistency of ≥ 90%, and a cementing agent can be selectively added to simulate the cementing strength of the reservoir.

[0018] Further, the whole process of particle migration is recorded by microphotography or video recording in step four.

[0019] Further, in step five, the permeability calculation formula of the circular particle migration model is:

[0020]

[0021] In the formula, k represents the permeability, μm 2 ; Q represents the flow, cm 3 / s; μ represents the fluid viscosity, mPa·s; ΔL represents the distance between two seepage sections, cm; and A represents the average seepage section area, cm 2 ; ΔP represents the pressure difference between two seepage sections, 10 -1 MPa.

[0022] The permeability calculation formula of the conical particle migration model is:

[0023]

[0024] In the formula, k represents the permeability, μm 2 ; Q represents the flow, cm 3 / s; μ represents the fluid viscosity, mPa·s; h represents the model thickness, cm; R represents the distance from the fluid starting point to the center point, cm; r represents the distance from the fluid outlet to the center point, cm; and ΔP represents the pressure difference between two seepage sections, 10 -1 MPa.

[0025] Compared with existing technologies, this invention constructs a fully visualized, multifunctional integrated, and highly accurate simulation experimental system and method for simulating particle migration in fracturing and filling sand control. It fundamentally solves the problem that traditional methods cannot dynamically observe particle migration processes under complex flow fields around the well. Through the unique design of the particle migration main module 5, it can simulate the dynamic process of particle migration around the well and within the reservoir, clarify the permeability changes in each region before and after particle migration, and guide the formulation of oil and gas well production and production allocation parameters. In particular, the design of the conical particle migration model 52 can realistically reproduce the velocity concentration effect in the near-wellbore zone indoors, filling the gap in physical simulation in this field. Combined with a fluid circulation and high-precision data acquisition system, it not only covers the entire low-to-high flow velocity range, but also allows for precise matching of experimental fluid, proppant, and reservoir sand parameters according to field requirements. This enables synchronous quantitative output of permeability damage, sand retention rate, and sand production characteristics, achieving long-term, quantitative analysis of the influence of multiple factors such as production parameters, fluid properties, and proppant type. This provides strong theoretical and data support for accurately optimizing sand control design and effectively managing particle migration damage. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of a visualization simulation experimental system for sand control particle transport in fracturing and filling according to an embodiment of the present invention;

[0027] Figure 2 for Figure 1 A schematic diagram of the structure of the first embodiment of the particle transport module shown;

[0028] Figure 3 for Figure 1 The diagram shows a structural schematic of a second embodiment of the particle transport module. Detailed Implementation

[0029] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0030] Figure 1 The structure of a visualized simulation experimental system 100 for preventing sand particle transport in fracturing and filling, according to an embodiment of the present invention, is shown. Figure 1 As shown, the visualized fracturing and backfilling sand control particle transport simulation experimental system 100 may include: a liquid storage and stirring tank 1 for preparing and temporarily storing experimental fluids; a liquid injection system 2, which includes multiple plunger pumps arranged in parallel with the liquid storage and stirring tank 1, each plunger pump being connected to the particle transport main module 5 via pipelines; and a gas injection system 3, which may include an air compressor 31 (preferably a high-pressure oil-free piston air compressor, with a working pressure of 0–10 MPa and a gas displacement of 0–0.8 m³ / s). 3a gas tank 32, connected to the micro-particle migration main module 5; a gas-liquid mixer 4, connected downstream of the liquid injection system 2 and the gas injection system 3, for uniformly mixing the gas-liquid two-phase fluid before injecting into the micro-particle migration main module 5; the micro-particle migration main module 5, including a full-transparent (preferably with a pressure-bearing capacity of ≥5MPa) circular micro-particle migration model 51 and / or a conical micro-particle migration model 52, and a plurality of pressure measuring points arranged axially inside the circular micro-particle migration model 51 and the conical micro-particle migration model 52; a sand collection and filtration system 6, arranged downstream of the micro-particle migration main module 5, for realizing solid-liquid-gas three-phase separation through a pipeline and recycling the liquid phase to the liquid storage and stirring tank 1; and a data acquisition and control system, for real-time monitoring of pressure, flow rate and pressure difference data.

[0031] In operation, the visual fracturing packing sand prevention micro-particle migration simulation experiment system 100 of the embodiment of the present application prepares or temporarily stores the fluid (such as clean water, simulated formation fluid, etc.) required for the experiment in the liquid storage and stirring tank 1; the liquid injection system (a plurality of plunger pumps) pumps out the fluid, the gas injection system 3 provides high-pressure gas, and the gas-liquid two-phase fluid is uniformly mixed in the gas-liquid mixer 4 to simulate the downhole multiphase flow state; the mixed fluid is injected into the transparent circular micro-particle migration model 51 and / or the conical micro-particle migration model 52, which are used to fill the formation sand and / or the proppant to simulate the wellbore environment; the process of micro-particle migration carried by the fluid can be directly observed, and the pressure change can be monitored in real time through the axially distributed pressure measuring points; the effluent enters the sand collection and filtration system 6 to realize solid-liquid-gas three-phase separation; the separated sand particles are analyzed, and the liquid phase can be returned to the liquid storage and stirring tank 1 through the return pipeline for recycling; and the data acquisition and control system monitors and records the key parameters such as pressure, pressure difference and flow rate in real time.

[0032] The visual fracturing packing sand prevention micro-particle migration simulation experiment system 100 of the embodiment of the present application uses compound sand highly consistent with the physical properties of the formation sand, simulates the formation fluid, and constructs the wellbore geometric model (especially the conical micro-particle migration model 52) in proportion, so that the experimental conditions are similar to the real downhole conditions, and the reference value of the experimental results is ensured. The flow rate and pressure of the fluid are controlled through the injection system to form a seepage field in the packing medium, and when the fluid shear force is greater than the starting resistance of the micro-particles, the micro-particles start to migrate. The conical micro-particle migration model 52 simulates the velocity concentration effect around the wellbore by changing the cross section to accelerate the migration of the micro-particles and reproduce the physical process that the near-wellbore zone is most prone to plugging. The transparent model is used to directly observe the migration path and plugging point. The differential pressure change monitored by the pressure measuring points, combined with the permeability calculation formula, can quantitatively calculate the permeability damage caused by the migration and plugging of the micro-particles, so as to convert the microcosmic phenomenon into a macroscopic quantifiable damage index.

[0033] According to the present application, in the like Figure 2In the preferred embodiment shown, the length of the circular micro-particle transport model 51 can preferably be 50-100 cm, the inner diameter of the circular inner cavity 12 can preferably be 5-10 cm, and the A direction is the flow direction of the fluid. In the preferred embodiment shown, Figure 3 In the preferred embodiment shown, the length of the conical micro-particle transport model 52 can preferably be 50-100 cm, the ratio of the inner diameters of the inlet 13 and the outlet 15 of the conical inner cavity 11 can preferably be 3:1 to 5:1, more preferably 8:3, the inner diameter of the inlet 13 can preferably be 200-250 mm, and the fluid flows from the inlet 13 to the outlet 15. This embodiment quantifies the simulation scale of the micro-particle transport main module 5, ensuring the scientificity and repeatability of the experiment; the inner diameter ratio of the conical micro-particle transport model 52 can accurately simulate the converging and accelerating effect of the fluid around the well, which cannot be achieved by a straight pipe model.

[0034] In the preferred embodiment shown, Figure 2 and Figure 3 In the preferred embodiment shown, the circular inner cavity 12 and the conical inner cavity 11 can be filled with compounded formation sand 7, or compounded formation sand 7 and proppant particles 8 (preferably a gravel pack layer), respectively, for forming a reservoir section and / or a packing section. For example, Figure 2 The filling of the circular inner cavity 12 with compounded sand 7 can simulate a reservoir, and the filling of the compounded sand and the gravel pack layer can simulate the near-wellbore area, Figure 3 The conical inner cavity 11 shown has a wide inlet and a narrow outlet, forcing the fluid to accelerate and simulate the converging effect of the flow rate around the well; the outlets of the circular inner cavity 12 and the conical inner cavity 11 can also be provided with metal screens 9. The arrangement of this embodiment can flexibly and realistically simulate various downhole environments from pure reservoirs to "reservoir-packing layer" composite structures and the converging of the flow rate around the well, and the arrangement of the metal screens 9 ensures the safety (prevents particle loss) and accuracy (simulates downhole screens) of the experiment.

[0035] According to the present application, in the preferred embodiment shown, Figure 1 The liquid injection system 2 can include at least one large-displacement plunger pump 21 and one small-displacement high-precision plunger pump 22 arranged in parallel. This arrangement expands the flow simulation range of the system, which can simulate both the high flow rate conditions of high-yield wells and the low flow rate conditions of low-permeability reservoirs, and has wider applicability.

[0036] Preferably, in the preferred embodiment shown, Figure 1 The liquid injection system 2 includes three plunger pumps, two large-displacement plunger pumps 21 and one small-displacement high-precision plunger pump 22 arranged in parallel, and further preferably, the maximum pressure of the large-displacement plunger pump 21 can be 10 MPa, and the maximum pressure of the small-displacement high-precision plunger pump 22 can be 70 MPa, so that the double pumps can deliver fluids with a viscosity of 0-1000 mPa·s, achieving continuous adjustable injection of 0-5 L / min and 0-90 mL / min.

[0037] In a preferred embodiment as shown in Figure 1 and Figure 2 In a preferred embodiment as shown in

[0038] In a preferred embodiment as shown in Figure 2 and Figure 3 In a preferred embodiment as shown in

[0039] In a preferred embodiment as shown in Figure 1 and

[0040] According to the present application, in a preferred embodiment, the gas-liquid mixer 4 can be a small-sized tubular static mixer, which can preferably achieve uniform gas-liquid mixing at a gas displacement range of 0-0.8 m 3 / min.

[0041] In a preferred embodiment as shown in Figure 1 and

[0042] According to the present application, in a preferred embodiment, the gas-liquid mixer 4 can be a small-sized tubular static mixer, which can preferably achieve uniform gas-liquid mixing at a gas displacement range of 0-0.8 m 3 / min.

[0043] Step one: system air tightness test with clean water and calibration of empty pipe friction; Step two: preparation of simulated reservoir fluid with specific viscosity and salinity in the liquid stirring tank 1; Step three: according to the actual sand production conditions and the properties of formation sand, configure the experimental simulated formation sand in the particle migration main module 5; Step four: set the gas and liquid flow, after mixing by the gas-liquid mixer 4, inject into the particle migration main module 5, real-time collection of pressure / differential pressure and flow data, record the particle migration pattern; Step five: terminate the experiment when the injection pressure is stable, collect and analyze the formation sand in the sand filter to obtain the sand production characteristics and permeability.

[0044] The visual fracturing packing sand prevention particle migration simulation experiment method in the embodiment of the application reproduces the fracturing fracture and the packing layer porous medium by using the transparent pressure-resistant particle migration main module 5, simulates the real "fluid-solid particle-porous medium" three-phase interaction by adjusting the flow rate, fluid properties and sand body properties, realizes the quantitative evaluation of the particle migration damage to the reservoir and the sand prevention effect by real-time measurement of the differential pressure and flow rate and the permeability analysis model. The visual fracturing packing sand prevention particle migration simulation experiment method in the embodiment of the application can realize the influence law analysis of different production allocation, fluid and reservoir properties and other conditions on the particle migration, and can also clearly determine the migration / plugging law of the particles in the gravel particles of different types, functions and packing parameters.

[0045] In the visual fracturing packing sand particle migration simulation experiment method of the embodiment of the present application, in step one, the visual fracturing packing sand particle migration simulation experiment system 100 can be connected according to the experimental system process, clean water is added to the liquid storage stirring tank 1, the clean water is pumped into the particle migration main module 5 using a large / small displacement injection pump, and the overall air tightness of the device is checked; the injection pump flow is gradually increased to test the empty pipe line pressure loss, and the influence of the pressure loss caused by fluid friction with the pipe column in subsequent permeability analysis and pressure drop calculation is eliminated. In step two, clean water and corresponding reagents can be added to the liquid storage stirring tank 1 respectively, and the liquid required for the simulation experiment of the particle migration main module 5 is prepared by stirring, dissolving and mixing uniformly; the air compressor 31 is turned on, the rated pressure is designed, and high-pressure gas is injected into the gas storage tank 32. In step three, according to the actual sand production conditions and the properties of the formation sand of the reservoir, the experimental simulation formation sand is configured, the compound sand 7 is filled into the circular particle migration model 51 and the conical particle migration model 52, or the compound sand 7 and the proppant particles 8 are filled respectively to simulate the near-wellbore reservoir section and the packing section, and the pressure / differential pressure sensor is connected to collect the pressure / differential pressure data of the reservoir section and the packing section. In step four, the gas and liquid two-phase fluid flow is set respectively, and after being mixed uniformly by the mixer 4, the fluid enters the particle migration main module 5 to start displacement, realizes the dynamic process simulation of the particle migration, and the dynamic process of the particle migration in the fracture can be observed in real time during the displacement process; after the fluid flows out of the particle migration model, the gas-liquid-solid three-phase is separated by the sand collection filter 61, and the liquid returns to the stirring tank 1 after passing through the liquid collection tank 62 to form a cycle. The pressure / differential pressure, flow and other parameter data are collected in real time during the experiment, and the particle migration morphology in the model is recorded. In step five, the experimental end determination standard is that the fluid injection pressure reaches 5 MPa or the pressure tends to be stable for a long time, and the formation sand particles in the sand collection filter 61 are collected after the experiment for subsequent analysis.

[0046] Further preferably, in step two, chemical reagents can be added to the clean water to simulate the viscosity, salinity and other physical and chemical properties of the reservoir production fluid. In addition, the reservoir production fluid can be directly added to the liquid storage stirring tank 1 to further improve the consistency between the simulation experiment conditions and the formation conditions, and to simulate the influence of the downhole fluid properties on the dynamic process of the particle migration.

[0047] It is also preferred that in step three, the properties of the compound sand used in the experiment simulation should be consistent with the properties of the reservoir production sand, and the compound sand should be prepared to ensure that the parameters such as the median particle size, the uniformity coefficient, the shale content and the shale composition of the compound sand meet the rate of ≥90%. In addition, when the compound sand is used to fill the particle migration main module 5, a suitable amount of cementing agent can be added according to the original core strength of different reservoirs to simulate the reservoir cementing strength, which is used to simulate the influence of the reservoir properties on the particle migration process.

[0048] Further preferably, in step three, for the circular particle migration model 51, the entire pipe can be filled with compounded formation sand, and a high-low precision two-layer filter screen 9 can be added at the outlet end of the model to simulate the reservoir environment to prevent the collapse production of the particles, for simulating the dynamic process and morphology of the particle migration in the reservoir, supporting the proposed particle migration mechanism; for the circular particle migration model 51, compounded formation sand and proppant particles can also be filled in the pipe at the same time to simulate the migration of formation sand particles in the near-well zone reservoir during production, as well as the dynamic process and quantitative law of the plugging of the formation sand in the packed layer. After filling the gravel particles, only one layer of filter screen 9 can be placed at the end of the device to prevent gravel particles from leaking, and the precision of the filter screen is slightly smaller than the minimum gravel size. The filling thickness of the proppant particles 8 can be changed to analyze the influence law of the filling thickness on the particle migration and plugging process.

[0049] Further, the proppant particles can also be selected from one of ultra-lightweight, lightweight, medium-weight, heavy ceramic spheres, or water control coated ceramic spheres, pre-consolidated coated ceramic spheres, self-suspending proppants, in-situ formed proppants, and expanded proppants, with a particle size range preferably of 0.1-1.2mm, forming a sand-prevention layer with different sand-retention precision after filling, for analyzing the influence law of different types, densities, and functions of the proppant parameters on the particle migration and plugging.

[0050] In step three, similar to the circular particle migration model 51, the conical particle migration model 52 can also be filled with formation sand alone or compounded with proppant particles 8, and the filling materials are the same as those of the circular particle migration model 51. For the conical particle migration model 52, due to the narrowing of the seepage channel along the axial direction from the inlet, the flow velocity is concentrated, which is mainly used to simulate the dynamic process of the particle migration under the condition of flow velocity concentration near the well and in the near-well zone, and to clarify the influence law of the reservoir properties, proppant properties, and packing parameters on the particle migration and plugging process.

[0051] Further, in step four, by injecting liquid, gas-liquid, or gas-liquid mixed fluid into the particle migration main module 5, the particle migration processes in oil-water wells, gas wells, and hydrate wells can be simulated respectively, for analyzing the influence law of different reservoir types on the particle migration.

[0052] Further, in step four, the entire particle migration process can be recorded by microscopic photography or video recording to realize the intuitive capture and mechanism analysis of the microscopic dynamic behaviors such as particle initiation, migration, and plugging, and to directly correlate the macroscopic parameter changes (pressure, flow rate) with the microscopic phenomena. The pressure / flow rate data are recorded in real time during the experiment for subsequent analysis of the pressure curve and the damage degree of permeability before and after the formation sand particle migration, and to clarify the damage law of the particle migration on the permeability under different production and sand-prevention conditions.

[0053] According to the present application, in order to quantitatively evaluate the degree of reservoir damage caused by particle migration, to provide accurate data support and decision basis for optimizing sand control parameters (such as proppant particle size, packing thickness), in step five, the permeability calculation formula of the particle migration main module 5 is given. Among them, the permeability calculation formula of the circular particle migration model can be:

[0054]

[0055] In the formula, k—permeability, μm 2 ; Q—flow rate, cm 3 / s; μ—fluid viscosity, mPa·s; ΔL—distance between two seepage sections, cm; A—average seepage cross-sectional area, cm 2 ; ΔP—pressure difference between two seepage sections, 10 -1 MPa;

[0056] The permeability calculation formula of the conical particle migration model is:

[0057]

[0058] In the formula, k—permeability, μm 2 ; Q—flow rate, cm 3 / s; μ—fluid viscosity, mPa·s; h—model thickness, cm; R—distance from fluid starting point to center point, cm; r—distance from fluid outlet to center point, cm; ΔP—pressure difference between two seepage sections, 10 -1 MPa.

[0059] Based on the calculation results of permeability damage, sand retention rate and other parameters, the sand retention, anti-clogging and permeability performance of different packing parameters and packing particle properties after particle migration can be analyzed, and the sand control parameters can be optimized and selected.

[0060] Further, in step five, the filter element of the sand collection filter 61 can be replaced at a specific time during the experiment, and the sand production characteristics such as sand production rate and sand production particle size under different displacement time conditions can be collected.

[0061] The fracturing packing sand prevention particle migration simulation experiment system and method can highly simulate complex downhole conditions, such as multiphase flow, wellbore geometric effect, and real packing medium, and can clearly show the migration / plugging mechanism and rule of particles in different types, functions and packing parameters of gravel particles, optimize sand prevention parameters, and support sand prevention process design of oil and gas wells. The system and method can simulate the dynamic process of particle migration, directly observe the dynamic process of formation sand particle migration, and characterize the dynamic change of permeability. The visual design makes the black box process, which is difficult to observe, intuitive, and the circulation system and multi-pump design greatly improve the efficiency and application range of the experiment, and provide a more powerful tool and process for in-depth study of particle migration mechanism and optimization of sand prevention process.

[0062] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A visualized simulation experimental system for sand particle transport during fracturing and backfilling, characterized in that, include: A liquid storage and stirring tank is used to prepare and temporarily store experimental fluids; A liquid injection system, comprising multiple plunger pumps arranged in parallel with the liquid storage and stirring tank, each of the plunger pumps being connected to a particle transport main module; A gas injection system is connected to the particle transport module. A gas-liquid mixer is connected in series downstream of the liquid injection system and the gas injection system to uniformly mix the two-phase gas-liquid fluid before injecting it into the particle transport module. The particle transport main module includes a transparent circular particle transport model and / or a conical particle transport model, wherein multiple pressure measurement points are arranged along the axial direction inside both the circular particle transport model and the conical particle transport model; The sand collection and filtration system is located downstream of the main particle transport module. It achieves solid-liquid-gas three-phase separation via pipeline and circulates the liquid phase to the liquid storage and stirring tank. as well as Data acquisition and control system, used to monitor pressure, flow rate and differential pressure data in real time.

2. The visualized fracturing and backfilling sand particle transport simulation experimental system according to claim 1, characterized in that, The circular particle transport model has a length of 50-100cm and an inner diameter of 5-10cm. The conical particle transport model has a length of 50-100cm and an inner diameter ratio of 3:1 to 5:1 for the inlet and outlet of the conical cavity. The inner diameter of the inlet is 200-250mm.

3. The visualized fracturing and backfilling sand particle transport simulation experimental system according to claim 2, characterized in that, The circular inner cavity and the conical inner cavity are respectively filled with compound formation sand, or compound formation sand and proppant particles, to form reservoir sections and / or filling sections; metal filter screens are also provided at the outlets of the circular inner cavity and the conical inner cavity.

4. The visualized fracturing and backfilling sand particle transport simulation experimental system according to any one of claims 1 to 3, characterized in that, The liquid injection system includes at least one large-displacement plunger pump and a small-displacement high-precision plunger pump arranged in parallel.

5. The visualized fracturing and backfilling sand particle transport simulation experimental system according to any one of claims 1 to 3, characterized in that, The pressure measuring point is connected to a pressure sensor via a ring-shaped fastening mechanism for real-time monitoring of axial pressure difference.

6. The visualized fracturing and backfilling sand particle transport simulation experimental system according to any one of claims 1 to 3, characterized in that, The sand collection and filtration system includes a sand collection filter and a liquid collection tank. The liquid collection tank is connected to the liquid storage and stirring tank through a return pipeline to realize closed-loop circulation of the experimental fluid.

7. A visualized simulation method for sand particle migration during fracturing and filling, employing the visualized simulation system for sand particle migration during fracturing and filling according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step 1: Perform a system airtightness test and calibrate the empty pipe friction using clean water; Step 2: Prepare a simulated reservoir fluid with specific viscosity and salinity in the storage and stirring tank; Step 3: Based on the actual reservoir sand production conditions and formation sand properties, simulated formation sand for experiments is configured into the microparticle transport module; Step 4: Set the gas and liquid flow rates, mix them in the gas-liquid mixer and then inject them into the particle transport module. Collect pressure / differential pressure and flow data in real time and record the particle transport morphology. Step 5: When the injection pressure stabilizes, terminate the experiment, collect and analyze the formation sand in the sand collection filter to obtain the sand output characteristics and permeability.

8. The visualized simulation experiment method for sand particle migration during fracturing and backfilling according to claim 7, characterized in that, In step three, the median particle size, uniformity coefficient, clay content, and composition of the formation sand are ≥90% consistent with the target reservoir, and a cementing agent may be selectively added to simulate the reservoir cementing strength.

9. The visualized simulation experiment method for sand particle migration during fracturing and backfilling according to claim 7, characterized in that, In step four, the entire process of particle transport is recorded by microscopic imaging or video recording.

10. The visualized simulation experiment method for sand particle migration control in fracturing and backfilling according to claim 7, characterized in that, In step five, the permeability calculation formula for the circular particle transport model is as follows: In the formula, k—permeability, μm 2 Q—Flow rate, cm 3 / s; μ—fluid viscosity, mPa·s; ΔL—distance between two seepage sections, cm; A—average seepage cross-sectional area, cm² 2 ΔP—Pressure difference between two seepage sections, 10 -1 MPa; The permeability calculation formula for the cone-shaped particle transport model is as follows: In the formula, k—permeability, μm 2 Q—Flow rate, cm 3 / s; μ—fluid viscosity, mPa·s; h—model thickness, cm; R—distance from fluid inlet to center point, cm; r—distance from fluid outlet to center point, cm; ΔP—pressure difference between the two seepage sections, 10 - 1 MPa.

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