Natural gas hydrate reservoir gravel packing sand prevention long-period simulation experiment device and sand prevention chart construction method

Abstract

The invention belongs to the technical field of sand control well completion in the natural gas hydrate development industry, and particularly relates to a natural gas hydrate reservoir gravel packing sand control long-period simulation experiment device and a sand control chart construction method. The simulation experiment device comprises a sand production and prevention and control integrated simulation system, a fluid injection system, a confining pressure pump, a liquid recovery tank and a data acquisition system, wherein the sand production and prevention and control integrated simulation system comprises a reservoir simulation module, a shaft annulus gravel layer simulation module and a screen pipe pre-filling layer simulation module; the fluid injection system and the confining pressure pump are connected with the reservoir simulation module, the liquid recovery tank is connected with the screen pipe pre-filling layer simulation module, and the data acquisition system is in signal connection with the sand production and prevention and control integrated simulation system. The simulation experiment device designed by the invention can truly simulate different production working conditions of the hydrate well, can accurately simulate the structure of the hydrate well bottom gravel packing sand control system, and can truly reduce the flow process of the hydrate well bottom fluid, so that the obtained experiment result is more authentic.

Description

Technical Field

[0001] The invention belongs to the technical field of sand control well completion in the natural gas hydrate development industry, and specifically relates to a natural gas hydrate reservoir gravel packing sand control long-period simulation experimental device and a sand control plate construction method. Background Art

[0002] Natural gas hydrate resources are abundant, less polluting and of high resource value. Efficient development is of strategic significance to improving my country's energy structure and achieving the "dual carbon" goal. Natural gas hydrates are mainly distributed on the seabed and below permafrost, and the recoverable natural gas reserves are twice the proven conventional oil and natural gas. Compared with traditional oil and gas reservoirs, natural gas hydrate reservoirs have low cementation strength, high mud content, and small formation sand particle size. Sand is easily produced during the production process, resulting in a significant reduction in gas production. In severe cases, it may cause production suspension, which seriously restricts the development of hydrate reservoirs. Hydrate production tests in China, the United States, Japan, Canada and other countries have confirmed this problem. The hydrate reservoir in the Shenhu Sea area of ​​the South China Sea is a muddy silt sand reservoir and is assessed to have a serious risk of sand production. In 2017, the first hydrate exploratory production in the South China Sea adopted a pre-filled screen sand prevention completion method. The production trial lasted 60 days, with an average daily gas production of 5150m 3 / d, with good sand control effect. In 2020, the second hydrate experimental production in the South China Sea adopted a pre-filled screen gravel filling composite sand control completion method. The trial production lasted for 30 days, with an average daily gas production of 2.87×10 4 m 3 / d, the engineering sand control achieved the goal of sand control within the monthly trial production cycle and withstood the test of sand production. However, the critical capacity of commercial natural gas hydrate in the sea area is 5×10 5 m 3 / d, and the production cycle can generally reach 5 to 10 years. At present, the production capacity and trial production cycle of natural gas hydrates are still some distance away from the commercial production of hydrates.

[0003] One of the key factors limiting the commercial exploitation of hydrates is the sand production problem during the hydrate trial production process. China's two rounds of hydrate trial production operations have formed a sand control completion system based on gravel filling, such as Figure 1 The sieve tube cross section is shown in Figure 1As shown in Figure 37, the arrow direction in the figure is the flow direction of the fluid in the hydrate reservoir during production. However, the use of sand control completion technology to control sand production will reduce the production capacity of the hydrate well, and sand control and production increase are contradictory. The gravel packing sand control completion system at the bottom of the hydrate well undertakes the hydrate reservoir and the hydrate well, and is the only channel for the hydrate reservoir fluid to enter the hydrate wellbore. The sand control accuracy is the key to the sand control performance of the sand control completion system and the production capacity control of the hydrate well. In the early stage of the hydrate well production, the gravel filling system with high sand control accuracy has a small filling size and strong sand control performance, but the system flow performance is weak; when the gravel filling system has a lower sand control accuracy, the filling gravel size increases, the system flow performance is enhanced, but the sand control performance is weakened. With the extension of the production time of the hydrate well, the pores between the gravels in the gravel filling systems with high sand control accuracy and low sand control accuracy will be occupied by formation sand, and finally reach a dynamic blocking equilibrium state. When the high sand control accuracy and low sand control accuracy gravel packing systems reach a dynamic blocking equilibrium state, the sand control performance and flow performance of the sand control system remain stable. However, there are large differences in the sand control performance and flow performance under the two sand control accuracy conditions. As shown in Figure 2, the direction of the arrow is the flow direction of the fluid in the hydrate reservoir during mining. The high sand control accuracy gravel packing system has a smaller particle size of the retained formation sand inside, and blocks the finer formation sand on the outside to form a dense mud cake with lower permeability. Figure 2a As shown in Figure 38, however, the particle size of the formation sand retained inside and blocked outside the low sand control precision gravel packing system is relatively large. When the blockage equilibrium state is reached, the high sand control precision gravel packing system has weak flow performance and strong sand control performance, while the low sand control precision gravel packing system has strong flow performance and weak sand control performance. However, maintaining the balance between the sand control performance and flow performance of the gravel packing system is more conducive to the long-term efficient production of natural gas hydrates.

[0004] In the face of the long-term and high-capacity requirements of future natural gas hydrate production trials, the reasonable optimization and design of the sand control accuracy of the gravel packing sand control system is of great significance for achieving the synergistic effect of sand control and production increase. At present, the sand control accuracy of gravel packing in hydrate reservoirs is mainly designed based on the formation sand particle size and combined with gravel packing indoor simulation experiments. This method mainly has the following problems:

[0005] (1) The existing gravel packing sand control simulation experimental device cannot accurately simulate the structure of the gravel packing sand control system at the bottom of the hydrate well. The device has a low pressure resistance and a short experimental period. It cannot simulate the mud and sand intrusion and blockage process of the gravel packing system under the long-term production conditions of hydrates. In addition, the device lacks flexibility and cannot simulate different production conditions at the bottom of the hydrate well. As a result, the experimental test results lack authenticity and cannot provide strong support for the precision design of gravel packing sand control in on-site hydrate wells.

[0006] (2) Currently, the gravel packing sand control accuracy of hydrate reservoirs is mainly designed based on the formation sand particle size and the gravel size empirical formula (Saucier formula). The optimization design of sand control accuracy takes into account fewer factors, and there is a lack of quantitative relationship between different factors and the sand control accuracy of the gravel packing sand control system. It is impossible to use a unified quantitative indicator to evaluate the advantages and disadvantages of gravel layers with different sand control accuracies.

[0007] (3) Sand control and production increase are contradictory. Improving the sand control accuracy of gravel packing will enhance the sand control performance of the gravel packing sand control system, but it will weaken the flow performance, which is not conducive to the increase of hydrate well production. At present, the design of gravel packing sand control accuracy is generally aimed at improving sand control performance, and the production capacity of hydrate wells is not considered. At present, there is a lack of sand control accuracy control methods that comprehensively consider the effects of sand control and production increase. Summary of the invention

[0008] The purpose of the present invention is: (1) to invent a set of hydrate reservoir multi-condition simulation long-term sand production and control integrated experimental system, which is used to study the blockage and production capacity change law of gravel packing sand control system under different sand control precision conditions. The experimental system can truly simulate the structure of the hydrate bottom gravel packing sand control system, and can flexibly adjust the device assembly method to simulate different hydrate bottom production conditions, so as to realize the real simulation of the mud and sand invasion and blockage process in the gravel layer with different sand control precision under long-term production conditions.

[0009] (2) Invent a set of RSPC sand control charts for hydrate reservoirs based on experimental test results and gravel layer structure. According to the different influencing factors affecting the design of gravel packing sand control accuracy, construct quantitative calculation expressions for different parameters and form sand control charts, so as to use unified quantitative indicators to evaluate the performance differences of gravel layers with different sand control accuracies, and support the optimization of sand control accuracy.

[0010] (3) Invent a method for optimizing and regulating the sand control accuracy of hydrate reservoirs based on the RSPC sand control map, comprehensively consider the synergistic effect of sand control and production increase, reasonably adjust the value range of sand control map parameters, and optimize and regulate the reasonable sand control accuracy range of the gravel pack sand control system in the hydrate reservoir to achieve long-term and efficient development of natural gas hydrates.

[0011] Based on this, the present invention discloses a long-period simulation experimental device for gravel packing sand control in a natural gas hydrate reservoir and a sand control plate construction method, which specifically adopts the following technical means:

[0012] The invention discloses a long-period simulation experimental device for gravel packing and sand control in a natural gas hydrate reservoir, comprising a sand production and control integrated simulation system, a fluid injection system, a confining pressure pump, a liquid recovery tank and a data acquisition system.

[0013] The integrated sand production and control simulation system comprises a reservoir simulation module, a wellbore annulus gravel layer simulation module and a screen pre-filling layer simulation module which are sequentially and detachably connected;

[0014] The reservoir simulation module is detachably provided with a core for simulating a natural gas hydrate reservoir; the wellbore annulus gravel layer simulation module is filled with a gravel layer sand control medium for simulating a wellbore annulus gravel layer; the screen pre-filling layer simulation module is filled with a screen pre-filling layer sand control medium for simulating a screen pre-filling layer; the gravel layer sand control medium and the screen pre-filling layer sand control medium can be made of ceramsite.

[0015] The end of the reservoir simulation module away from the wellbore annulus gravel layer simulation module and the end of the screen pre-filling layer simulation module away from the wellbore annulus gravel layer simulation module are both provided with threaded dead plugs;

[0016] The fluid injection system and the confining pressure pump are both connected to the reservoir simulation module, the liquid recovery tank is connected to the screen pre-filling layer simulation module, and the data acquisition system is connected to the sand production and prevention and control integrated simulation system signal.

[0017] The main body of the existing natural gas hydrate sand production simulation experimental device is generally a core holder. The device can only place the core to simulate the sand production process of the hydrate reservoir, and cannot place the natural gas hydrate reservoir sand control medium to carry out sand control experimental research. The existing sand control simulation device is generally large in size, mostly made of acrylic material, with a pressure resistance of 0-5MPa, and the experimental period that can be carried out is 0-2h, which is a short experimental period.

[0018] The simulation experimental device of the present invention is a long-term sand production and sand control integrated experimental device that integrates sand production and sand control functions. The main body of the simulation experimental device of the present invention is a sand production and control integrated simulation system composed of a reservoir simulation module, a wellbore annulus gravel layer simulation module and a screen pre-filling layer simulation module. By placing a core (actual reservoir core or artificial core) in the reservoir simulation module and filling the wellbore annulus gravel layer simulation module and the screen pre-filling layer simulation module with sand control media, the hydrate bottom gravel filling sand control completion system can be truly simulated. The simulation experimental device of the present invention can simulate both the sand production process of the hydrate reservoir and the sand control process of the hydrate well. The sand production and control integrated simulation system is made of stainless steel. The experimental system has a pressure resistance of 30MPa and supports 0-7 days of long-term sand production and control simulation experiments of hydrate reservoirs.

[0019] The present invention can adjust the length of the internal space of the reservoir simulation module and the sieve pre-filling layer simulation module by arranging threaded dead plugs I and threaded dead plugs II on the reservoir simulation module and the sieve pre-filling layer simulation module to simulate cores and sieve pre-filling layers of different thicknesses. By flexibly adjusting the thickness of the simulated sieve pre-filling layer and the simulated wellbore annulus gravel layer (by placing fake cores of different lengths in the wellbore annulus gravel layer simulation module, the thickness of the simulated wellbore annulus gravel layer can be adjusted), hydrate wells with different wellbore structures can be simulated, and by flexibly assembling the three modules of the integrated sand production and prevention and control simulation system and adjusting the gravel layer filling method, different production conditions of the hydrate reservoir can be simulated.

[0020] During the experiment, the data acquisition system can collect pressure and flow data in real time to calculate and analyze the changes in the permeability of the hydrate sand control system (i.e., the wellbore annulus gravel layer and screen prefill layer simulated by the simulation experimental device). After the experiment, the three modules of the integrated simulation system for sand production and prevention and control can be opened to collect and analyze the formation sand that passes through and is retained in the sand control system and the formation sand that is blocked. The experimental test results obtained above provide data support for the construction of the RSPC sand control map.

[0021] Furthermore, the reservoir simulation module can accommodate cores with a length of 0 to 120 mm, and the screen pre-filling layer simulation module can accommodate a screen pre-filling layer with a length of 0 to 50 mm.

[0022] Furthermore, the fluid injection system includes an injection branch I, an injection branch II and a gas-liquid mixer.

[0023] Injection branch I includes a liquid storage tank, a constant flow and pressure pump, a liquid flow meter, a sand adding piston container and a control valve connected in sequence, and injection branch II includes a gas cylinder, a gas booster system and a gas flow controller connected in sequence; the constant flow and pressure pump has two functions: constant flow displacement and constant pressure displacement. The flow adjustment range is 0-100ml / min, and the displacement pressure adjustment range is 0-70MPa. The pressure adjustment range of the gas booster system is 0-60MPa. By adjusting the constant flow and pressure pump and the gas booster system, the experimental parameters of the integrated simulation system for sand production and prevention and control can meet the actual flow conditions at the bottom of the hydrate well.

[0024] The inlet of the gas-liquid mixer is at the end of the injection branch I and the injection branch II, and the outlet of the gas-liquid mixer is connected to the reservoir simulation module;

[0025] A pressure sensor is provided between the gas-liquid mixer and the reservoir simulation module, and between the liquid recovery tank and the screen tube pre-filling layer simulation module, and the pressure sensor is connected to the data acquisition system signal.

[0026] The present invention also discloses a method for constructing a sand control plate. The purpose of constructing the sand control plate is to screen out the best area of ​​sand control accuracy from the sand control plate, and the method comprises the following steps:

[0027] 1) Using any of the above-mentioned simulation experimental devices to carry out a long-term simulation experiment of gravel packing and sand control in a natural gas hydrate reservoir;

[0028] 2) Based on the experimental results of step 1), the comprehensive evaluation index of the gravel layer is calculated, which specifically includes the following sub-steps:

[0029] ① Calculate the sand control index:

[0030] Sand control index: characterizes the sand control ability of gravel layers of different types and different sand control precision. Based on the results of the long-term simulation experiment of gravel pack sand control, the sand retention rate, retention rate and mud and sand particle size distribution of the gravel pack sand control system (referring to the simulated wellbore annulus gravel layer and / or the simulated screen pre-filling layer) are used for calculation. The sand control index ranges from 0 to 1. The higher the sand control index, the stronger the sand control ability of the gravel layer, which is more conducive to controlling the output of mud and sand (formation sand) in the hydrate reservoir.

[0031]

[0032] In formula (VI), R D is the sand retention rate of the gravel layer, dimensionless; M1 is the sand retention amount of the gravel layer, kg (the mass of the remaining mud and sand in the core or the reservoir simulation module 18 without the core after the experiment); M is the total sand production of the hydrate reservoir (the initial mud and sand mass in the core or the reservoir simulation module 18 without the core before the experiment), kg;

[0033] In formula (VII), R L is the sediment retention rate in the gravel layer, dimensionless; M3 is the mass of sediment passing through the gravel layer (the mass of sediment collected by the liquid recovery tank after the experiment), kg;

[0034] In formula (VIII), W d is the sand control index, dimensionless; I Wd is the weighted coefficient of the gravel layer’s sand control performance, dimensionless, and the recommended value is 0.60; d0 is the median particle size of the composite sand used in the experiment (the median particle size of the mud and sand before the experiment), mm; d l is the average particle size of the mud and sand invading the gravel layer (the median particle size of the mud and sand retained in the screen pre-fill layer and / or the gravel layer in the wellbore annulus after the experiment), mm;

[0035] ②Calculate the flow index:

[0036] Flow index: Characterizes the flow capacity of gravel layers of different types and different sand control precision. Based on the results of the long-term simulation experiment of gravel packing sand control, the permeability of the gravel packing sand control system at different stages is used for calculation. The flow index ranges from 0 to 1. The higher the flow index, the stronger the flow capacity of the gravel layer, which is more conducive to increasing the production of hydrate wells.

[0037]

[0038] In formula (IX), is the comprehensive permeability of the gravel layer, μm 2 ;k g0 is the initial permeability of the gravel layer (the permeability of the screen pre-packing layer and / or the gravel layer in the wellbore annulus before the experiment), μm 2 ;k d is the gravel layer blocking permeability, μm 2 , the plugging permeability is the middle value between the initial permeability and the equilibrium permeability, and is calculated by the initial permeability and the equilibrium permeability. k gp is the equilibrium permeability of the gravel layer, μm 2 , the equilibrium permeability can be determined by the permeability curve. When the permeability curve finally tends to be stable, the permeability almost remains constant. The permeability at this time is the equilibrium permeability; are the weighting coefficients of initial permeability, plugging permeability, and equilibrium permeability, respectively, dimensionless, with recommended values ​​of 0.3, 0.4, and 0.4;

[0039] In formula (X), W l is the flow index, dimensionless; k zmax is the comprehensive permeability of gravel layers with different precisions under the same experimental conditions Maximum value, μm 2 .

[0040] ③Calculate the comprehensive evaluation index:

[0041] Comprehensive evaluation index: Characterizes the balance between sand control ability and flow ability of gravel layers of different types and different sand control precisions. Based on the sand control index and flow index of the gravel layer, according to the production conditions and sand production characteristics of the natural gas hydrate reservoir, and the balance between sand control ability and flow ability, different weighting coefficients are set respectively, and the comprehensive evaluation index of gravel layers with different sand control precisions is obtained by weighted calculation. The comprehensive evaluation index ranges from 0 to 1. The higher the comprehensive evaluation index, the stronger the balance between the sand control ability and flow ability of the gravel layer, which can effectively control the output of mud and sand, and promote the increase of hydrate well production.

[0042]

[0043] In formula (I), W is a comprehensive evaluation index, dimensionless; Wd is the sand control index, dimensionless; W is the weighted coefficient of the gravel layer’s sand control performance, dimensionless, and the recommended value is 0.6; l is the flow index, dimensionless; is the weighted coefficient of the flow performance of the gravel layer, dimensionless, and the recommended value is 0.4;

[0044] 3) Calculate the sand retention coefficient based on the experimental test results of step 1) and the gravel parameters:

[0045] Sand retention coefficient: It characterizes the ability of gravel layers of different types and different sand control precision to block mud and sand in hydrate reservoirs and the ability of mud and sand to block gravel layers. The range of sand retention coefficient is 0-1, and the larger the sand retention coefficient, the better. The higher the sand blocking rate of the gravel layer and the smaller the pore blocking rate, the larger the sand retention coefficient, indicating that the gravel layer is not easy to be blocked and has a strong sand control performance.

[0046] First, the pore volume that can be invaded inside the gravel layer is calculated according to the size of the packed gravel, and then the pore blockage rate is calculated according to the pore volume between the packed gravels and the mud and sand retention mass obtained from the experimental test. Finally, the sand retention coefficient of the gravel packing sand control system is calculated according to the pore blockage rate and sand passing rate caused by the mud and sand retained in the gravel layer.

[0047]

[0048] In formula (XI), V f is the pore volume inside the gravel layer, m 3 ; L is the filling thickness of the gravel layer, m; N is the equivalent flow area of ​​the gravel layer, m 2 ; is the porosity of the gravel layer, dimensionless.

[0049]

[0050] In formula (XII), R P is the pore blockage rate, dimensionless; M2 is the mass of mud and sand retained in the gravel layer, kg; ρ s is the density of mud and sand, kg / m 3 .

[0051]

[0052] In formula (III), R is the sand retention coefficient, dimensionless; R D is the sand retention rate of the gravel layer, dimensionless; R P is the pore blockage rate, dimensionless;

[0053] 4) Calculate the plugging skin coefficient based on the experimental results of step 1) and the gravel parameters:

[0054] Blockage skin coefficient: a dimensionless parameter used to characterize the additional pressure loss caused by blockage of the gravel packing layer in the hydrate well. It reflects the effect of gravel layer blockage on the fluid flow resistance near the wellbore and is used to evaluate the effect of gravel layer blockage on well productivity. The blockage skin coefficient is greater than 0. The larger the blockage skin coefficient, the more serious the gravel layer blockage and the more significant the permeability loss of the gravel layer.

[0055] The blockage degree of the gravel layer is related to factors such as the ratio of the median particle size of gravel to formation sand, the thickness of the gravel layer, the displacement and viscosity of the fluid. The blockage skin coefficient of the gravel layer is calculated based on the permeability test results of the long-term simulation experiment of gravel packing sand control.

[0056]

[0057] In formula (IV), S P is the plugging skin coefficient of the gravel layer, dimensionless; ΔP is the pressure difference between the two ends of the gravel layer when the gravel layer reaches the plugging equilibrium during the experiment, Pa, where the plugging equilibrium state refers to the state when the permeability of the gravel layer remains basically constant; k g0 is the initial permeability of the gravel layer, m 2 ; h is the thickness of the gravel layer, m; μ is the viscosity of the fluid, Pa·s; q is the displacement of the fluid, m 3 / s; R GS is the median ratio of gravel to formation sand, dimensionless; k gp is the equilibrium permeability of the gravel layer, m 2 .

[0058] 5) Calculate the capacity ratio of the gravel pack sand control system based on the plugging skin coefficient:

[0059] The production capacity ratio of the gravel packing sand control system before and after blockage in the gravel packing sand control hydrate well is calculated according to the skin coefficient of gravel layer blockage, so as to analyze the changes in the production capacity of gravel packing sand control systems of different types and with different sand control precisions, thereby guiding the optimization and regulation of the sand control precision of the hydrate reservoir sand control system.

[0060]

[0061] In formula (V), PR is the gravel packing capacity ratio, dimensionless; e is the liquid supply radius, m; r w is the radius of the hydrate well, m; S is the intrinsic skin coefficient of the hydrate well, dimensionless.

[0062] The radius of the hydrate-containing area controlled by the hydrate well underground is called the liquid supply radius. It is mainly related to the permeability of the hydrate reservoir, the production of the hydrate well, and the viscosity of the hydrate reservoir fluid. The liquid supply radius is derived based on Darcy's law.

[0063] 6) Construct a sand control map to screen out the area with the best sand control accuracy:

[0064] Change the sand control accuracy of the gravel layer (i.e. change the size of the filling ceramsite), and use steps 1) to 5) to calculate the W, R, and S of the gravel layer with different sand control accuracies. P , PR parameters, respectively construct W, R, S P , PR parameters and the median value of filling gravel particle size, based on W, R, S P , the corresponding curve between PR parameter and median size of filling gravel is used to construct RSPC sand control chart;

[0065] Determine W, R, and S based on the purpose of gravel pack sand control design P , PR and the optimal value ranges of the four parameters. Based on the optimal value ranges of the four parameters, the optimal areas A, B, C, and D corresponding to the four parameters are drawn on the RSPC sand control chart of the hydrate reservoir. The common intersection of the four areas is found on the RSPC sand control chart of the hydrate reservoir. The median range of gravel particle size corresponding to the common intersection of the four areas is the area with the best sand control accuracy.

[0066] The gravel layer in steps 2) to 6) is a simulated wellbore annulus gravel layer and / or a simulated screen pre-filling layer. In the process of hydrate reservoir development, in the gravel-filled sand-control completion hydrate bottom of different production conditions, the gravel accuracy and filling density of the wellbore annulus gravel layer and the screen pre-filling layer may be the same or different. Therefore, when the gravel accuracy and filling density of the simulated wellbore annulus gravel layer and the screen pre-filling layer are the same, the gravel layer in the sand control map construction method refers to the simulated wellbore annulus gravel layer and the screen pre-filling layer. When the gravel accuracy and filling density of the simulated wellbore annulus gravel layer and the screen pre-filling layer are different, it is necessary to construct sand control maps for the wellbore annulus gravel layer and the screen pre-filling layer to select their respective optimal sand control accuracy ranges. Therefore, at this time, the gravel layer in the sand control map construction method refers to the simulated wellbore annulus gravel layer or the screen pre-filling layer.

[0067] According to the purpose of gravel pack sand control design (actual production purpose), the recommended value ranges of the four parameters in the sand control chart are determined, and the optimal areas A, B, C and D for gravel layer sand control accuracy are selected. If the sand control performance of the gravel pack sand control system is to be enhanced, the optimal range values ​​of the comprehensive evaluation index and the sand retention coefficient are increased. If the flow performance of the gravel pack sand control system is to be enhanced to increase the production capacity of the hydrate well, the optimal range value of the plugging skin coefficient is reduced, and the production capacity ratio is increased. The parameters of the gravel pack sand control system are designed according to the optimal sand control accuracy range selected, so that the gravel pack sand control system can maintain good sand control performance while minimizing the impact on the production capacity of hydrates, so as to achieve the synergistic effect of sand control and production increase in the gravel pack sand control system.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) The simulation experimental device designed in the present invention integrates the sand production and sand control functions of the hydrate reservoir, can accurately simulate the structure of the gravel packing sand control system at the bottom of the hydrate well, can truly restore the fluid flow process at the bottom of the hydrate well, and the obtained experimental results are more realistic.

[0070] (2) The simulation experimental device designed in the present invention can realistically simulate different production conditions of hydrate wells by flexibly adjusting different modules of the integrated simulation system for sand production and prevention and control, which has guiding significance for the actual gravel packing sand control design of hydrate wells.

[0071] (3) The basic data of the sand control map proposed in the present invention are derived from the indoor experimental test results and gravel layer structural parameters that meet the actual working conditions of hydrate wells. The basic data are easy to obtain and the sand control map is easy to operate. The optimal value range of parameters in the sand control map can be reasonably adjusted based on different design purposes of gravel packing sand control. The sand control map has a wide range of applications and is applicable to hydrate wells that are intended to improve sand control performance, increase hydrate well production capacity, or balance sand control performance and production capacity. The hydrate gravel packing sand control precision control method with the synergistic effect of comprehensive sand control and increased production proposed in the present invention is conducive to the long-term and efficient development of natural gas hydrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a schematic diagram of the actual working condition of the gravel pack sand control completion system;

[0073] Figure 2a This is a schematic diagram of the sand intrusion and retention situation in the gravel layer with high sand control accuracy;

[0074] Figure 2b This is a schematic diagram of the sand intrusion and retention situation in the gravel layer with low sand control accuracy;

[0075] Figure 3 Schematic diagram of the long-period simulation experimental device for gravel packing and sand control in natural gas hydrate reservoirs of the present invention;

[0076] Figure 4 It is a structural schematic diagram of the integrated simulation system for sand production and prevention and control of the present invention;

[0077] Figure 5a A schematic diagram of a gravel pack sand control completion hydrate bottom hole production condition 1 simulated by the present invention;

[0078] Figure 5b A schematic diagram of a gravel pack sand control completion hydrate bottom hole production condition 2 simulated by the present invention;

[0079] Figure 5cSchematic diagram of the bottom hole production condition 3 of the gravel pack sand control completion hydrate simulated by the present invention;

[0080] Figure 5d It is a schematic diagram of the bottom hole production condition 4 of the gravel pack sand control completion hydrate simulated by the present invention;

[0081] Figure 6 Schematic diagram of gravel packing and sand control completion structure in hydrate wellbore;

[0082] Figure 7a This is a schematic diagram of the state of the gravel layer before the formation sand invades;

[0083] Figure 7b This is a schematic diagram of the state of the gravel layer after the formation sand invades;

[0084] Figure 8 RSPC sand control chart constructed for Example 3;

[0085] Fig. 9 Based on Figure 8 Schematic diagram of the area with optimal sand control accuracy selected by the RSPC sand control map.

[0086] Among them, 1—liquid storage tank; 2—constant flow and pressure pump; 3—liquid flow meter; 4—sand adding piston container; 5—control valve; 6—gas cylinder; 7—gas pressurization system; 8—gas flow controller; 9—gas-liquid mixer; 10—pressure sensor; 11—confining pressure pump; 12—sand production and prevention and control integrated simulation system; 13—data acquisition system; 14—liquid recovery tank; 15—threaded dead plug; 16—screen pre-filling layer module; 17—wellbore annulus gravel layer simulation module; 18—reservoir simulation module; 19—rubber cylinder; 20—sand production and prevention and control integrated 1-inlet of the hydrate simulation system; 21-confining pressure interface; 22-pressure sensor interface; 23-outlet of the sand production and prevention and control integrated simulation system; 24-consolidated ceramsite pre-filling layer; 25-loose ceramsite gravel layer; 26-core; 27-loose ceramsite pre-filling layer; 28-pre-filling screen; 29-screen outer protection cover; 30-hydrate wellbore; 31-wellbore annulus gravel filling layer; 32-screen pre-filling gravel layer; 33-inside of base pipe; 34-base pipe; 35-fluid flow direction; 36-formation sand, 37-screen profile, 38-mud cake. DETAILED DESCRIPTION

[0087] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0088] Example 1

[0089] like Figure 3 , Figure 4As shown, this embodiment discloses a long-period simulation experimental device for gravel packing and sand control in a natural gas hydrate reservoir, including a sand production and control integrated simulation system 12, a fluid injection system, a confining pressure pump 11, a liquid recovery tank 14 and a data acquisition system 13.

[0090] The integrated sand production and control simulation system 12 includes a reservoir simulation module 18, a wellbore annulus gravel layer simulation module 17 and a screen pre-filling layer simulation module 16 which are sequentially and detachably connected; in this embodiment, the inner diameters of the reservoir simulation module 18, the wellbore annulus gravel layer simulation module 17 and the screen pre-filling layer simulation module 16 are all 25 mm, and the lengths are 120 mm, 33 mm and 50 mm respectively.

[0091] The reservoir simulation module 18 is provided with a removable core 26 for simulating a natural gas hydrate reservoir, and a rubber tube 19 can be provided between the core 26 and the reservoir simulation module 18. The wellbore annulus gravel layer simulation module 17 is filled with a gravel layer sand control medium for simulating the gravel layer of the wellbore annulus, and the screen pre-filling layer simulation module 16 is filled with a screen pre-filling layer sand control medium for simulating the screen pre-filling layer. The core 26 can be an actual core or an artificial core of the hydrate reservoir, and the gravel layer sand control medium and the screen pre-filling layer sand control medium can both use ceramsite of different sizes.

[0092] The end of the reservoir simulation module 18 away from the wellbore annulus gravel layer simulation module 17, and the end of the screen pre-filling layer simulation module 16 away from the wellbore annulus gravel layer simulation module 17 are both provided with a threaded dead plug 15. The simulation reservoir module 18 can accommodate a core with a length of 0-120 mm by adjusting the length of the threaded dead plug 15, the filling length of the wellbore annulus gravel layer module 17 is 33 mm, and can accommodate a wellbore annulus gravel layer with a length of 0-33 mm. The screen pre-filling layer simulation module 16 can also accommodate a screen pre-filling layer with a length of 0-50 mm by adjusting the length of the threaded dead plug 15.

[0093] The fluid injection system is connected to the inlet 20 of the sand production and control integrated simulation system of the reservoir simulation module 18, the confining pressure pump 11 is connected to the confining pressure interface 21 of the reservoir simulation module 18, the liquid recovery tank 14 is connected to the outlet 23 of the sand production and control integrated simulation system of the screen prefilling layer simulation module 16, and the data acquisition system 13 is signal-connected to the sand production and control integrated simulation system 12.

[0094] The fluid injection system includes an injection branch I, an injection branch II and a gas-liquid mixer. The injection branch I includes a liquid storage tank 1, a constant flow and pressure pump 2, a liquid flow meter 3, a sand adding piston container 4 and a control valve 5 connected in sequence. The injection branch II includes a gas cylinder 6, a gas booster system 7 and a gas flow controller 8 connected in sequence. The inlet 9 of the gas-liquid mixer is at the end of the injection branch I and the injection branch II, and the outlet of the gas-liquid mixer 9 is connected to the reservoir simulation module 18. The constant flow and pressure pump 2 has two functions of constant flow displacement and constant pressure displacement. The flow rate adjustment range is 0-100ml / min, and the displacement pressure adjustment range is 0-70MPa. The pressure adjustment range of the gas booster system 7 is 0-60MPa. By adjusting the constant flow and pressure pump 2 and the gas booster system 7, the experimental parameters of the long-period simulation experimental device for gravel filling and sand prevention in natural gas hydrate reservoirs can meet the flow conditions of the actual hydrate bottom.

[0095] A pressure sensor 10 is provided between the gas-liquid mixer 9 and the reservoir simulation module 18, and between the liquid recovery tank 14 and the screen pre-filling layer simulation module 16. The three modules of the sand production and prevention and control integrated simulation system 12 are all provided with a pressure sensor interface 22 for connecting with the pressure sensor 10 to monitor the pressure value during the experiment in real time. The pressure sensor 10 is connected to the data acquisition system 13 for signal.

[0096] Example 2

[0097] This embodiment discloses a method for conducting a simulation experiment using the natural gas hydrate reservoir gravel packing sand control long-period simulation experiment device of Example 1:

[0098] 1) According to different hydrate reservoir production conditions, an integrated simulation system for sand production and control 12 is assembled to simulate the gravel packing sand control completion method of hydrate wells:

[0099] During the development of hydrate reservoirs, there may be conditions where the hydrate reservoir is deficient or the structure of the gravel pack sand control completion method changes. By flexibly adjusting the three modules of the integrated sand production and prevention and control simulation system, different production conditions of gravel pack sand control completion hydrate well bottom can be simulated, as shown below:

[0100] Production condition 1: At the initial stage of hydrate well production, there is no hydrate reservoir deficit, the gravel pack sand control completion structure has not changed, and the consolidated gravel layer in the screen pre-packing layer remains intact; Figure 5a shown.

[0101] The reservoir simulation module 18 is used to place actual cores or artificial cores of the hydrate reservoir to provide a sand source for the gravel packing sand control long-term simulation experiment; the wellbore annulus gravel layer simulation module 17 is filled with different sizes of ceramsite to simulate the actual gravel filling of the wellbore annulus gravel layer in the hydrate well, and the filling length is 33 mm, such as Figure 5a The loose ceramsite gravel layer 25 is shown in the figure; the screen pre-filling layer simulation module 16 is filled with ceramsite of different sizes and consolidated to simulate the pre-filling screen inside the gravel layer of the wellbore annulus, such as Figure 5b As shown in the consolidated expanded clay pre-filling layer 24;.

[0102] Production condition 2: After the hydrate well has been put into production for a period of time, the hydrate reservoir has no deficit, the structure of the gravel pack sand control completion method has changed, and the consolidated gravel layer in the screen pre-packing layer has failed, such as Figure 5b shown.

[0103] The reservoir simulation module 18 is used to place actual cores or artificial cores of the hydrate reservoir to provide a sand source for the gravel packing sand control long-term simulation experiment; the wellbore annulus gravel layer simulation module 17 is filled with ceramsite of different sizes to simulate the actual gravel filling of the wellbore annulus gravel layer in the hydrate well, and the filling length is 33 mm; the screen pre-filling layer simulation module 16 is filled with loose ceramsite of different sizes to simulate the pre-filling screen of the failed consolidated ceramsite inside the wellbore annulus gravel layer, such as Figure 5b As shown in the loose ceramsite pre-filling layer 27.

[0104] Production Condition 3: At the initial stage of hydrate well production, the hydrate reservoir is depleted, the gravel pack sand control completion structure has not changed, and the consolidated gravel layer in the screen pre-fill layer remains intact. Figure 5c shown.

[0105] The hydrate reservoir has a deficit, and the formation sand of the hydrate reservoir does not directly contact the gravel sand control system. The reservoir simulation module 18 remains blank to simulate the deficit hydrate reservoir. A certain concentration of slurry is configured in the sand adding piston container 4 to provide a sand source for the gravel packing sand control long-term simulation experiment. The screen pre-filling layer simulation module 16 is filled with ceramsite of different sizes and consolidated to simulate the pre-filled screen inside the gravel layer of the wellbore annulus.

[0106] Production condition 4: After the hydrate well has been put into production for a period of time, the hydrate reservoir has a deficit, the structure of the gravel pack sand control completion method has changed, and the consolidated gravel layer in the screen pre-packing layer has failed, such as Figure 5d shown.

[0107] The reservoir simulation module 18 remains blank to simulate the depleted hydrate reservoir. A certain concentration of slurry is configured in the sand adding piston container 4 to provide a sand source for the gravel packing sand control long-term simulation experiment. The screen pre-filling layer simulation module 16 is filled with loose ceramsite of different sizes to simulate the pre-filling screen of the failed consolidated ceramsite inside the gravel layer of the wellbore annulus.

[0108] 2) Conduct simulation experiments:

[0109] A core 26 is placed in the reservoir simulation module 18 and a confining pressure is applied to the core 26 by the confining pressure pump 11, or a slurry of a certain concentration is configured in the sand adding piston container 4 to simulate the sand source of the hydrate reservoir. Secondly, according to the actual hydrate reservoir temperature and pressure conditions, hydrate wellbore structure parameters, production parameters and the size of the integrated simulation system 12 for sand production and prevention and control, the gas-water flow rate under indoor experimental conditions is converted by the velocity equivalent method to truly simulate the flow process at the bottom of the actual hydrate well. The conversion method can be found in the reference: Liu Chenfeng. Development of high-performance sand control screen for muddy silt sand hydrate reservoir [D]. China University of Petroleum (East China), 2022.

[0110] Then, the whole simulation experiment device is connected and the sealing of the device is checked. The constant flow constant pressure pump 2 and the gas boosting system 7 are turned on to inject gas and water into the gas-liquid mixer 9. After the gas and liquid are evenly mixed, they are injected into the sand production and prevention and control integrated simulation system 12 to start the experiment. During the experiment, the gas and water displacement during the experiment and the pressure at different positions of the sand production and prevention and control integrated simulation system 12 are collected in real time through the data acquisition system 13, and the fluid passing through the sand production and prevention and control integrated simulation system 12 is collected, and the formation sand quality and particle size passing through the sand production and prevention and control integrated simulation system 12 are weighed and analyzed.

[0111] Finally, after the experiment, the collected flow and pressure data were used to calculate and analyze the changes in the permeability of the sand control system during the invasion of the formation sand into the integrated sand production and prevention and control simulation system 12. The three modules of the integrated sand production and prevention and control simulation system 12 were opened, and the gravel layers in the screen pre-filling layer simulation module 16 and the wellbore annulus gravel layer simulation module 17 were taken out respectively. The mass and particle size of the formation sand retained in the gravel layer were weighed and analyzed, and the invasion degree of the formation sand in the gravel layer was analyzed with a microscope.

[0112] The performance indicators of the gravel pack sand control system are calculated and analyzed using experimentally tested parameters such as permeability, retention, mass and particle size of formation sand passing through the gravel layer, mass and particle size of formation sand blocked by the gravel layer, etc., to support the construction of the RSPC sand control map for hydrate reservoirs.

[0113] Figure 6 Schematic diagram of gravel packing and sand control completion structure in hydrate wellbore. Figure 7a , 7b Schematic diagram of the state of the gravel layer before and after formation sand invasion. Among them, 28 is the pre-filled screen; 29 is the outer protective cover of the screen; 30 is the hydrate wellbore wall; 31 is the gravel filling layer in the wellbore annulus; 32 is the pre-filled gravel layer of the screen; 33 is the inside of the base pipe; 34 is the base pipe; 35 is the fluid flow direction; 36 is the formation sand. Ls is the thickness of the pre-filled layer of the screen, Ls is the thickness of the gravel filling layer in the wellbore annulus, L is the total thickness of the gravel layer, D B is the diameter of the base pipe.

[0114] Example 3

[0115] This embodiment discloses a method for constructing a natural gas hydrate reservoir sand control map, comprising the following steps:

[0116] 1) The method described in Example 2 was used to conduct a long-term simulation experiment of gravel packing and sand control in a natural gas hydrate reservoir. In this example, production condition 4 was simulated. In production condition 4, the gravel accuracy and packing density of the wellbore annulus gravel layer and the screen pre-packing layer were the same;

[0117] 2) Based on the experimental results of step 1) and gravel parameters, calculate W, R, S under different sand control accuracies according to steps 2) to 5) of the method for constructing a sand control plate for natural gas hydrate reservoirs in the manual. P , PR parameters, and construct W, R, S respectively P , the corresponding curve between PR parameter and median size of filling gravel;

[0118] 3) Based on W, R, S obtained in step 2) P The RSPC sand control chart is constructed by using the corresponding curves of PR parameters and the median size of the filling gravel. Figure 8 As shown;

[0119] 4) In order to maintain the synergistic effect of sand control and production increase of the gravel pack sand control system, this embodiment sets the optimal range of the comprehensive evaluation index to 0.5-1, the optimal range of the sand retention coefficient to 0.5-1, the optimal range of the plugging skin coefficient to 0-2, and the optimal range of the production capacity ratio to 0.4-1.

[0120] 5) Based on the optimal value ranges of the four parameters, the optimal areas A, B, C, and D corresponding to the four parameters are drawn on the RSPC sand control chart of the hydrate reservoir, and the common intersection of the four areas is found on the RSPC sand control chart of the hydrate reservoir. Fig. 9 The median range of gravel particle size corresponding to the middle area E) is the optimal area of ​​sand control accuracy (reasonable sand control accuracy area), because the sand control accuracy of the gravel packing sand control system is determined by the filling gravel particle size.

[0121] 6) If Fig. 9 As shown, the sand control accuracy range screened out in this embodiment is 0.320mm-0.525mm. Gravel with a median particle size within this range is selected for filling, and the synergistic effect of sand control and production increase is better.

Claims

1. A long-period simulation experimental device for gravel packing and sand control in natural gas hydrate reservoirs, characterized in that: include: Sand production and prevention and control integrated simulation system, fluid injection system, confining pressure pump, liquid recovery tank and data acquisition system, The integrated sand production and control simulation system comprises a reservoir simulation module, a wellbore annulus gravel layer simulation module and a screen pre-filling layer simulation module which are sequentially and detachably connected; The reservoir simulation module is provided with a detachable core for simulating a natural gas hydrate reservoir, the wellbore annulus gravel layer simulation module is filled with a gravel layer sand control medium for simulating a wellbore annulus gravel layer, and the screen pre-filling layer simulation module is filled with a screen pre-filling layer sand control medium for simulating a screen pre-filling layer; The end of the reservoir simulation module away from the wellbore annulus gravel layer simulation module and the end of the screen pre-filling layer simulation module away from the wellbore annulus gravel layer simulation module are both provided with threaded dead plugs; The fluid injection system and the confining pressure pump are both connected to the reservoir simulation module, the liquid recovery tank is connected to the screen pre-filling layer simulation module, and the data acquisition system is connected to the sand production and prevention and control integrated simulation system signal.

2. The simulation experiment device according to claim 1, characterized in that: The reservoir simulation module can accommodate a core with a length of 0 to 120 mm, and the screen pre-filling layer simulation module can accommodate a screen pre-filling layer with a length of 0 to 50 mm.

3. The simulation experiment device according to claim 1, characterized in that: The fluid injection system comprises an injection branch I, an injection branch II and a gas-liquid mixer. The injection branch I includes a liquid storage tank, a constant flow and pressure pump, a liquid flow meter, a sand adding piston container and a control valve connected in sequence, and the injection branch II includes a gas cylinder, a gas pressurizing system and a gas flow controller connected in sequence; The inlet of the gas-liquid mixer is at the end of the injection branch I and the injection branch II, and the outlet of the gas-liquid mixer is connected to the reservoir simulation module; A pressure sensor is provided between the gas-liquid mixer and the reservoir simulation module, and between the liquid recovery tank and the screen tube pre-filling layer simulation module, and the pressure sensor is connected to the data acquisition system signal.

4. A method for constructing a sand control map for a natural gas hydrate reservoir, characterized in that: The steps include: 1) Using the simulation experiment device described in any one of claims 1 to 3 to carry out a long-term simulation experiment of gravel packing and sand control in a natural gas hydrate reservoir; 2) Based on the experimental results of step 1), calculate the comprehensive evaluation index of the gravel layer: In formula (I), W is the comprehensive evaluation index, dimensionless; W d is the sand control index, dimensionless; is the weighted coefficient of the gravel layer’s sand control performance, dimensionless; W l is the flow index, dimensionless; is the weighted coefficient of gravel layer flow performance, dimensionless; 3) Calculate the sand retention coefficient based on the experimental results of step 1): In formula (III), R is the sand retention coefficient, dimensionless; R D is the sand retention rate of the gravel layer, dimensionless; R P is the pore blockage rate, dimensionless; 4) Calculate the plugging skin coefficient based on the experimental results of step 1): In formula (IV), S P is the gravel layer plugging skin coefficient, dimensionless; ΔP is the pressure difference between the two ends of the gravel layer when the gravel layer reaches the blocking equilibrium during the experiment, Pa; k g0 is the initial permeability of the gravel layer, m 2 ; h is the thickness of the gravel layer, m; μ is the viscosity of the fluid, Pa·s; q is the displacement of the fluid, m 3 / s; R GS is the median ratio of gravel to formation sand, dimensionless; k gp is the equilibrium permeability of the gravel layer, m 2 ; 5) Calculate the capacity ratio of the gravel pack sand control system based on the plugging skin coefficient: In formula (V), PR is the gravel packing capacity ratio, dimensionless; r e is the liquid supply radius, m; r w is the radius of the hydrate well, m; S is the intrinsic skin coefficient of the hydrate well, dimensionless; 6) Construct a sand control map to screen out the area with the best sand control accuracy: Change the sand control accuracy of the gravel layer and use steps 1) to 5) to calculate the W, R, and S of the gravel layer with different sand control accuracies P , PR parameters, respectively construct W, R, S P , PR parameters and the median value of filling gravel particle size, based on W, R, S P , the corresponding curve between PR parameter and median size of filling gravel is used to construct RSPC sand control chart; Determine W, R, and S based on the purpose of gravel pack sand control design P , PR, and the optimal value ranges of the four parameters. Based on the optimal value ranges of the four parameters, the optimal areas A, B, C, and D corresponding to the four parameters are drawn on the RSPC sand control chart of the hydrate reservoir. The common intersection of the four areas is found on the RSPC sand control chart of the hydrate reservoir. The median range of gravel particle size corresponding to the common intersection of the four areas is the area with the best sand control accuracy. The gravel layer in steps 2) to 6) is a simulated wellbore annulus gravel layer and / or a simulated screen pre-packing layer.

5. The method for constructing a sand control plate according to claim 4, characterized in that: In step 2), the sand control index W d The calculation method is: In formula (VI), R D is the sand retention rate of the gravel layer, dimensionless; M1 is the sand retaining capacity of the gravel layer, kg; M is the total sand production of hydrate reservoir, kg; In formula (VII), R L is the sediment retention rate in the gravel layer, dimensionless; M3 is the mass of mud and sand passing through the gravel layer, kg; In formula (VIII), d0 is the median particle size of the composite sand used in the experiment, mm; d l is the average particle size of mud and sand intruding into the gravel layer, mm.

6. The method for constructing a sand control plate according to claim 4, characterized in that: Step 2) Flow index W l The calculation method is: In formula (IX), is the comprehensive permeability of the gravel layer, μm 2 ;k g0 is the initial permeability of the gravel layer, μm 2 ; are the weighting coefficients of initial permeability, plugging permeability and equilibrium permeability, dimensionless; k d is the gravel layer blocking permeability, μm 2 ;k gp is the equilibrium permeability of the gravel layer, μm 2 ; In formula (X), k zmax is the maximum value of the comprehensive permeability of gravel layers with different precisions under the same set of experimental conditions, μm 2 .

7. The method for constructing a sand control plate according to claim 4, characterized in that: In step 3), the pore volume V inside the gravel layer f The calculation method is: In formula (XI), L is the filling thickness of the gravel layer, m; N is the equivalent flow area of ​​the gravel layer, m 2 ; is the porosity of the gravel layer, dimensionless.

8. The method for constructing a sand control plate according to claim 4, characterized in that: In step 3), the pore blockage rate R P The calculation method is: In formula (XII), M2 is the mass of mud and sand retained in the gravel layer, kg; ρ s is the density of mud and sand, kg / m 3 .

9. The method for constructing a sand control plate according to claim 6, characterized in that: The gravel layer plugging permeability=(gravel layer initial permeability+gravel layer equilibrium permeability) / 2.

10. The method for constructing a sand control plate according to claim 6, characterized in that: The value is 0.

60. The values ​​are 0.3, 0.4, and 0.4 respectively.

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