Simulation method for remaining reserves in water-bearing gas reservoirs

Abstract

The application discloses a simulation calculation method of remaining reserves of a water-containing gas reservoir, and is implemented according to the following steps: S1, a gas reservoir mold with multiple simulation layers is prepared, and each simulation layer in the gas reservoir mold is divided into a characterization unit, and the number N of the characterization units in the gas reservoir mold is calculated i S2, the gas reservoir mold is pressed, a cover plate with holes and a probe are installed on the gas reservoir mold, the gas reservoir mold is pressed for the second time, after the second time of pressing, epoxy resin is poured on the surface of the gas reservoir mold, after the epoxy resin is solidified, the gas reservoir mold is subjected to a confining pressure and water is added; S3, after the confining pressure, the gas reservoir mold is inflated, and the initial gas storage capacity of the characterization unit is calculated; S4, after the inflation is completed, the gas reservoir mold is exhausted, and the water-containing volume of each characterization unit is calculated; S5, the remaining pore volume of each characterization unit after water invasion is calculated; and S6, the remaining reserves of the mold are calculated. The method solves the problem that the remaining reserves at different positions of the mold cannot be calculated in the prior art.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of remaining reserves distribution research of water-bearing gas reservoirs, and particularly relates to a simulation calculation method of remaining reserves of water-bearing gas reservoirs. BACKGROUND

[0002] In the development process of water-bearing gas reservoirs, with the decrease of the energy of the gas storage layer, the formation water invades the gas reservoir, which leads to early water breakthrough in the gas well, a substantial reduction in the production, and even the shutdown of the gas well in serious cases. The indoor physical simulation experiment can well simulate the water invasion process of the gas reservoir. On the one hand, the mold used in the experiment can maximize the preservation of the original reservoir heterogeneity through the combination of different simulation layers. On the other hand, the physical simulation experiment can monitor the pressure and water saturation of the mold in real time, and completely record the water invasion dynamics of the development process of the water-bearing gas reservoir, thereby providing guidance for the water control measures of the gas reservoir. In addition to the pressure and water saturation at each position in the mold, the reserve production condition is also an important indicator for studying the water invasion dynamics of the water-bearing gas reservoir. Therefore, there is an urgent need for a method to calculate the remaining reserves of each position in the multi-layer commingling physical mold of the water-bearing gas reservoir.

[0003] At present, there are many studies on the physical simulation of the water invasion process of the water-bearing gas reservoir, but few scholars have deeply explored the calculation method of the remaining reserves in the process of the physical simulation experiment. The calculation of the remaining reserves in the previous physical mold is to take the entire physical mold as the research object, and the calculation result is single, which can only calculate the total remaining reserves of the mold and cannot calculate the remaining reserves at different positions of the mold. In summary, it is of great significance to establish a calculation method of the remaining reserves distribution of the water-bearing gas reservoir physical mold for the water control, production capacity prediction and other work of the gas reservoir. SUMMARY

[0004] The purpose of the present application is to provide a simulation calculation method of the remaining reserves of the water-bearing gas reservoir, which solves the problem of being unable to calculate the remaining reserves at different positions of the mold in the prior art.

[0005] The technical solution adopted by the present application is that the simulation calculation method of the remaining reserves of the water-bearing gas reservoir is implemented according to the following steps:

[0006] S1, a gas reservoir mold with multiple simulation layers is made, and each simulation layer in the gas reservoir mold is divided into multiple volume-equal characterization unit bodies, and the number N of all the characterization unit bodies in the gas reservoir mold is calculated i and the pore volume V ijk .

[0007] S2, the gas reservoir mold is pressed, a cover plate with holes and a probe are installed on the gas reservoir mold, and the gas reservoir mold is pressed for the second time. After the second pressing, epoxy resin is poured on the surface of the gas reservoir mold, and after the epoxy resin is cured, the gas reservoir mold is subjected to confining pressure and water is added;

[0008] S3, after confining pressure, the gas reservoir mold is inflated, and the initial storage capacity n of the unit is calculated ijk ;

[0009] S4, after inflation, the gas reservoir mold is exhausted, and the water-containing volume of each unit is calculated

[0010] S5, using V ijk 、 calculate the residual pore volume V of each unit after water invasion i ′ jk ;

[0011] S6, using V i ′ jk calculate the remaining storage capacity n of the mold i ′ jk .

[0012] The present application is also characterized by:

[0013] Step 1 is implemented according to the following steps:

[0014] S1.1 According to the actual sequence and thickness of each producing layer of the gas reservoir, determine the gas reservoir mold with multiple simulation layers, the size of each simulation layer and the basic material of each simulation layer required for the artificial core;

[0015] S1.2 According to the thickness of the i-th layer of the simulation layer mold, divide the i-th simulation layer into multiple units;

[0016] S1.3 The number of each unit is calculated according to formula (1), and the pore volume of each unit is calculated according to formula (2):

[0017]

[0018]

[0019] L i - The length of the physical mold i-th layer, m; W i - The width of the physical mold i-th layer, m; H i - The height of the physical mold i-th layer, m; N i - The number of units in the i-th layer, units; V ijk - The pore volume of the physical mold i-th layer j row k unit, m 3 ; - The porosity of the physical mold i-th layer, dimensionless.

[0020] The size of the simulation layer includes thickness, porosity φ i , permeability.

[0021] Step 2 is implemented according to the following steps:

[0022] S2.1 The artificial core base material described in S1.1 is sequentially laid in the mold, the mold loaded with the base material is pressed once, taken out, and installed with a hole cover plate and a probe, the characterization unit probe is put along the hole on the corresponding cover plate, and is slowly extruded to be flush with the upper end of the probe and the upper surface of the cover plate;

[0023] S2.2 The mold with all the probes assembled is sent into the pressurizing equipment again, and after being pressed and formed, it is taken out, and the hole cover plate on the mold is removed. After the mold is solidified, an epoxy resin with a thickness of 0.5-1.0 cm is cast on the surface. After the epoxy resin is solidified, the mold is moved into a high-pressure container;

[0024] S2.3 The probe is connected to the monitoring hole inside the high-pressure container by a pipeline. Each monitoring hole leads to the outside of the high-pressure container and is connected with a valve. After the high-pressure container is sealed, the data acquisition system is opened;

[0025] S2.4 Liquid fluid is injected into the high-pressure container to apply confining pressure to the mold. When the confining pressure slowly rises to the set value, the injection is stopped.

[0026] Step 3 is implemented according to the following steps:

[0027] S3.1 An optional probe connection channel outside the high-pressure container is connected as a gas injection port, and a gas flow meter and a high-pressure gas source are sequentially connected. After the high-pressure gas source is opened, the mold is slowly filled with gas. When the monitoring pressure value of each probe is not greater than 1-1.5 MPa of the confining pressure, the gas injection is stopped;

[0028] S3.2 The cumulative gas injection amount V 总 , the pressure P ijk of each characterization unit, and the ambient temperature T are recorded.

[0029] S3.3 The initial gas storage amount of the characterization unit is calculated using formula (3):

[0030]

[0031] In the formula, n ijk is the initial gas storage amount of the i-th layer, j-th row, and k-th characterization unit, mol; P ijk is the initial pressure of the i-th layer, j-th row, and k-th characterization unit, MPa; Z ijk is the gas compression factor when the pressure of the i-th layer, j-th row, and k-th characterization unit is P ijk , dimensionless; R is the ideal gas constant, 8.314 J / (mol·K); and T is the initial absolute temperature of the mold, K.

[0032] Step 4 is implemented according to the following steps:

[0033] S4.1 Adjust the valve of the gas injection port probe channel to extract gas from inside the mold, and record the cumulative gas output V through the flow meter. 产 Convert it into the cumulative mass of gas produced, n' 总 Simultaneously, the pressure P'ijk and water saturation S of each characterization unit were recorded. Wijk Mold temperature T';

[0034] S4.2 Calculate the water volume of each characterization unit using formula (6):

[0035]

[0036]

[0037]

[0038] In the formula: n′ 总 —Cumulative mass of gas produced, in mol; V 产 —Cumulative gas production volume, m3; S Wijk —Water saturation of the unit cell in row k of layer i, dimensionless; Rinitial—Resistance value measured at the initial probe position, Ω; Rend—Resistance value measured at the end probe position, Ω; V 水ijk —The volume of intrusive water in the unit cell of the i-th layer, row j, k, is represented in m3; S Wijk —The water saturation of the unit cell in row k of the i-th layer is dimensionless;

[0039] The formulas for calculating the remaining pore volume of each characterization unit after water intrusion are as follows:

[0040]

[0041] In the formula: V i ′ jk —The remaining pore volume of the unit cell after water intrusion in row j of the i-th layer, m3;

[0042] Mold remaining reserves n' ijk The calculation formula is as follows:

[0043]

[0044] In the formula: Z i ′ jk —The pressure of the unit cell in row j of the i-th layer is P. i ′ jk Gas compressibility factor at time; V i ′ jk —The remaining pore volume of the unit cell after water immersion in the i-th layer, row j, k, m3; T'—Absolute temperature of the mold after water immersion, K; R—Ideal gas constant.

[0045] The beneficial effects of the present application are:

[0046] (1) The present application can calculate the remaining reserves at each position in the experimental mold, fully reflecting the influence of intra-layer and inter-layer heterogeneity on gas reservoir development during multi-layer combined production; (2) According to the real-time pressure, water saturation, temperature and other collection results, the gas production characteristics of any position in the flat large physical mold at any time can be calculated; (3) The present application considers the influence of water invasion volume on the remaining reserves calculation process, making the calculation result more accurate; (4) Compared with the conventional reserves calculation method, the core of the present application is the mass of gas, and the conversion of gas volume under different pressures can be ignored. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a large physical mold schematic diagram of multi-layer combined production of water-bearing gas reservoirs;

[0048] Figure 2 is a probe plane distribution schematic diagram;

[0049] Figure 3 is a single probe structure schematic diagram;

[0050] Figure 4 is a single probe structure cross-sectional view.

[0051] In the figure: 1. First simulation layer, 2. Second simulation layer, 3. Third simulation layer, 4. First layer probe, 5. Second layer probe, 6. Third layer probe, 7. Internal electrode interface, 8. Pressure sensor, 9. External electrode interface, 10. External electrode, 11. Insulating layer, 12. Internal electrode. DETAILED DESCRIPTION

[0052] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0053] (1) According to the actual order and thickness of each production layer of the gas reservoir, the number of layers of the multi-layer combined production physical gas reservoir mold, the size of each simulation layer, including thickness, porosity φ i , permeability, and then determine the type and quality of the basic material of the artificial core required for each simulation layer, according to the thickness H i of the i-th layer, divide the i-th layer into a characteristic unit body with a side length of H i , and use formula (1) to calculate the number of probes required for the i-th layer as the number of characteristic unit bodies N i , and use formula (2) to calculate the pore volume V ijk of the characteristic unit body, and mix the basic materials of the same layer uniformly for later use:

[0054]

[0055]

[0056] In the formula: L i —Length of the i-th layer of the physical mold, m; W i — Width of the i-th layer of the physical mold, m; H i — Height of the i-th layer of the physical mold, m; N i —Number of character units in the i-th layer; V ijk —The pore volume of the unit cell in row k of the i-th layer of the physical mold, in m 3 ; —Porosity of the i-th layer of the physical mold, dimensionless.

[0057] (2) According to the actual sequence of each producing layer in the gas reservoir, the mixed artificial core base material is sequentially laid into the mold. The mold containing the base material is placed in a pressurizing device and pressed once with low pressure. After that, it is taken out and covered with a 1.5cm thick perforated cover plate. The probe length l of the i-th layer of the mold is selected. i The probe is the sum of the thickness of all simulated layers in the upper part of the i-th layer and half the thickness of the i-th simulated layer. The diameter of the hole on the cover plate is slightly larger than the diameter of the probe used. The number of holes is Ni, which is the number of probes in each layer. The hole is located at the geometric center of the horizontal plane of the j-row k-list characterization unit of the i-th layer. The probe of the j-row k-list characterization unit of the i-th layer is inserted along the corresponding hole on the cover plate and slowly squeezed until the upper end of the probe is flush with the upper surface of the cover plate.

[0058] (3) After all the probes are assembled, the mold is sent back into the pressurizing equipment, pressed and formed, and the mold is taken out. The perforated cover plate on the top of the mold is removed. After it is cured, epoxy resin with a thickness of 0.5 to 1.0 cm is poured on its surface. After the epoxy resin is cured, the mold is moved into the high-pressure container.

[0059] (4) Connect the probe to the monitoring hole inside the high pressure container with a pipeline. Each monitoring hole leads to the outside of the high pressure container and is connected to a valve. After sealing the high pressure container, open the data acquisition system and inject a stable liquid fluid into the high pressure container to apply confining pressure to the mold. Stop the injection when the confining pressure slowly rises to the experimental requirement value.

[0060] (5) Select any probe connection channel outside the high-pressure vessel as the gas injection port, and then connect a gas flow meter and a high-pressure gas source in sequence. Turn on the high-pressure gas source to slowly fill the mold with gas. Stop the gas injection when the pressure value monitored by each probe is less than the confining pressure of 1 to 1.5 MPa, remove the high-pressure gas source, and record the cumulative gas intake volume V of saturated gas. 总 Pressure P of each characterizing unit ijk 1. Ambient temperature T, and the initial gas storage capacity of the characteristic unit cell in row k of the i-th layer is calculated according to (3):

[0061]

[0062] wherein: n ijk — initial gas storage of the i th layer j th row k th characterization unit, mol; P ijk — initial pressure of the i th layer j th row k th characterization unit, MPa; Z ijk — gas compression factor of the i th layer j th row k th characterization unit when the pressure is P ijk , dimensionless; R— ideal gas constant, 8.314 J / (mol·K); T— initial absolute temperature of the mold, K.

[0063] (6) Adjust the probe channel valve of the gas injection port, and extract the gas in the mold. Record the cumulative gas production V 产 , and convert it into the mass n' of the cumulative gas production 总 , and record the pressure P' of each characterization unit ijk , the water saturation S Wijk of each characterization unit, and the mold temperature T'. Calculate the water volume of each characterization unit according to formula (6):

[0064]

[0065]

[0066]

[0067] wherein: n' 总 — mass of the cumulative gas production, mol; V 产 — volume of the cumulative gas production, m3; S Wijk — water saturation of the i th layer j th row k th characterization unit, dimensionless; R 初始 — resistance value obtained by monitoring at the initial time of the probe, Ω; R 结束 — resistance value obtained by monitoring at the end time of the probe, Ω; V 水ijk — water invasion volume of the i th layer j th row k th characterization unit, m3; S Wijk — water saturation of the i th layer j th row k th characterization unit, dimensionless:

[0068] (7) Calculate the residual pore volume of each characterization unit after water invasion by formula (7):

[0069]

[0070] wherein: V' ijk — residual pore volume of the i th layer j th row k th characterization unit after water invasion, m3.

[0071] (8) Calculate the residual storage of each characterization unit according to formula (8), and the residual storage distribution of the multi-layer combined large physical mold can be obtained:

[0072]

[0073] wherein: Z' is the gas compressibility factor at the temperature of T' and the pressure of P' ; V' is the gas compressibility factor at the temperature of T' and the pressure of P' ; T' is the absolute temperature of the mold after water invasion, K; R is the ideal gas constant. ijk — the pressure of the i-th layer j-th row k-th characterization unit body is P' ijk — the gas compressibility factor at the temperature of T' and the pressure of P' ; V' ijk — the residual pore volume of the i-th layer j-th row k-th characterization unit body after water invasion, m3; T' is the absolute temperature of the mold after water invasion, K; R is the ideal gas constant.

[0074] Example 1

[0075] To verify the reliability of the present application, a large-scale physical mold for multi-layer combined production of gas reservoirs was actually made in combination with Figure 1 , and the remaining reserves were calculated by monitoring the changes of pressure and water saturation at a certain position in the mold before and after simulated gas production. The specific implementation manner of the present application adopts the following technical scheme:

[0076] (1) According to the porosity and permeability K i of each layer, three formulations (Table 1) were designed, and three layers of 60cm×60cm×5cm simulated reservoirs were successively pressed in the same mold; Table 1: Porosity and permeability requirements of each simulated layer

[0077]

[0078]

[0079] (2) According to the experimental requirements, each layer was divided into 5cm×5cm×5cm characterization unit bodies, and there were 12×12×3 characterization unit bodies in total;

[0080] (3) A group of monitoring probes was arranged in each characterization unit body, and 12×12 probe groups were arranged on the plane, each probe group including four probes, which were a common probe 13.5cm, a first layer probe 4 with a length of 3.5cm, a second layer probe 5 with a length of 8.5cm and a third layer probe 6 with a length of 13.5cm;

[0081] (4) After standing for 24h, the physical mold was wrapped with a layer of guanidine gum after the cement in the physical mold was cured, and then it was stood for another 24h to dry;

[0082] (5) Holes were drilled at the designed positions, and pipeline joints were installed to simulate injection and production wells;

[0083] (6) Epoxy resin was used to cast the physical mold, and a packaging layer with a thickness of about 0.5cm was formed on the surface of the physical mold;

[0084] (7) After standing for 48h, the epoxy resin was fully cured;

[0085] ​(8) Put the physical model into the pressurizing device, and connect the pipeline;

[0086] (9) Seal the pressurizing device, and fill the pressurizing device with liquid until the liquid pressure in the chamber reaches 10.0 MPa;

[0087] (10) Start the detection equipment, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical model with air until the pressure of each point in the model is balanced, then close the gas cylinder, and the cumulative air intake is 13.88 mol (310.96 L);

[0088] (11) Take the 7th characterization unit in the 6th row of the 2nd layer as an example, the pressure is 8.0 MPa, the temperature is 293.15 K, and the porosity is 7.8%. According to formula (1), the pore space of the 7th characterization unit in the 6th row of the 2nd layer is 10 cm 3 ;

[0089]

[0090] (12) According to the table, the compression coefficient of air at this time is 0.9874. According to formula (2), the initial gas storage capacity of the 7th characterization unit in the 6th row of the 2nd layer is 0.0324 mol (0.726 L);

[0091]

[0092] (13) Connect the gas cylinder to the intermediate container filled with formation water, and connect the outlet end of the intermediate container to the injection inlet of the model, and set the pressure to 8.0 MPa;

[0093] (14) Open the production control valve, simulate the gas reservoir development process, and when the experiment is finished, close the valve, and record the measured pressure, water saturation, and temperature of each point at this time. For example, the pressure of the 7th characterization unit in the 6th row of the 2nd layer is 7.3 MPa, the water saturation is 31.4%, and the temperature is 290 K;

[0094] (15) According to formula (3), the water intrusion volume of the characterization unit is calculated to be 3.14 cm 3 ;

[0095]

[0096] (16) According to formula (4), the remaining gas storage space of the characterization unit is calculated to be 6.86 cm 3 ;

[0097] V′ 2,6,7 = 10 x 10 -6 - 3.14 x 10 -6 = 6.86 x 10 -6 m 3 .

[0098] (17) look up the air compression coefficient at this time, which is 0.9812, and calculate the residual storage of the characterization unit according to formula (5), which is 0.0211 mol (0.474 L), and the recovery rate is 35%;

[0099]

[0100] (18) calculate the residual storage of each characterization unit according to steps (10)-(16).

[0101] Example 2

[0102] To verify the reliability of the present application, a large-scale physical mold for multi-layer combined production of gas reservoirs is actually made, and the residual storage is calculated by monitoring the changes of pressure and water saturation at a certain position in the mold before and after gas production. The specific embodiment of the present application adopts the following technical scheme:

[0103] (1) According to the porosity of each layer and permeability K i Two formulations (Table 2) are required to be designed, and two layers of 60 cm x 60 cm x 5 cm simulated reservoirs are successively pressed in the same mold;

[0104] Table 2: Porosity and permeability requirements of each simulated layer

[0105]

[0106] (2) According to the experimental requirements, each layer is divided into 5 cm x 5 cm x 5 cm characterization units, and there are 12 x 12 x 2 characterization units in total;

[0107] (3) A group of monitoring probes is arranged in each characterization unit, and 12 x 12 probe groups are arranged on the plane, each probe group contains 4 probes, which are common probe 7, length is 8.5 cm, first layer probe 4, length is 3.5 cm and second layer probe 5, length is 8.5 cm;

[0108] (4) After standing for 24 h, the physical mold is wrapped with a layer of guanidine after the cementation is cured, and then it is stood for another 24 h to dry;

[0109] (5) Drill holes at the designed position, install pipeline joints, and simulate injection and production wells;

[0110] (6) Use epoxy resin to cast the physical mold, and form a packaging layer of about 0.5 cm on the surface;

[0111] (7) Stand for 48 h to allow the epoxy resin to fully cure;

[0112] (8) Transfer the physical mold into the pressurizing device and connect the pipelines;

[0113] (9) Close the pressurizing device and fill it with liquid until the liquid pressure in the chamber reaches 10.0 MPa;

[0114] (10) Start the detection device, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air, and close the gas cylinder after the pressure at each point in the mold balances, with a cumulative air intake of 9.45 mol (211.75 L);

[0115] (11) Take the 2nd layer, 6th row, and 7th column characterization unit as an example, with a pressure of 8.0 MPa, a temperature of 293.15 K, and a porosity of 6.0%, the pore space of the 2nd layer, 6th row, and 7th column characterization unit is calculated to be 10 cm 3 according to formula (1);

[0116]

[0117] (12) According to the table, the compression coefficient of air at this time is 0.9874, and the initial gas storage capacity of the 2nd layer, 6th row, and 7th column characterization unit is calculated to be 0.0249 mol (0.558 L) according to formula (2);

[0118]

[0119] (13) Connect the gas cylinder to the intermediate container filled with formation water, and connect the outlet end of the intermediate container to the injection inlet of the mold, and set the pressure to 8.0 MPa;

[0120] (14) Open the production control valve to simulate the gas reservoir development process, and close the valve when the experiment is completed, and record the measured pressure, water saturation, and temperature at this time, such as the pressure of the 2nd layer, 6th row, and 7th column characterization unit being 6.0 MPa, the water saturation being 40.2%, and the temperature being 290 K;

[0121] (15) According to formula (3), the water intrusion volume of the characterization unit is calculated to be 3.02 cm 3 ;

[0122]

[0123] (16) According to formula (4), the remaining gas storage space of the characterization unit is calculated to be 4.48 cm 3 ;

[0124] V′ 2,6,7 = 7.5 x 10 -6 - 3.02 x 10 -6 = 4.48 x 10 -6 m 3 .

[0125] (17) The compressibility coefficient of air at this time is 0.9901. According to formula (5), the remaining reserves of the characterization unit are 0.0113 mol (0.253 L) and the recovery rate is 55%.

[0126]

[0127] (18) Calculate the remaining reserves of each characterization unit according to steps (10) to (16).

[0128] Example 3

[0129] To verify the reliability of this invention, a large-scale physical model of multi-layered gas reservoir production was actually fabricated. The remaining reserves were calculated by monitoring changes in pressure and water saturation at a specific location within the model before and after simulated gas production. The specific implementation of this invention employs the following technical solution:

[0130] (1) Based on the porosity of each layer and penetration rate K i Design one formulation (Table 3) and press one 60cm×60cm×5cm simulated reservoir layer sequentially in the same mold;

[0131] Table 3 Pore permeability requirements for each simulated layer

[0132]

[0133] (2) According to the experimental requirements, each layer was divided into a 5cm×5cm×5cm characterization unit, with a total of 12×12×1 characterization units;

[0134] (3) A set of monitoring probes is arranged in each characterization unit. 12×12 probe groups are arranged on the plane. Each probe group contains 2 probes, namely the common probe 7 with a length of 3.5cm and the first layer probe 4 with a length of 3.5cm.

[0135] (4) Let stand for 24 hours. After the adhesive in the physical mold has solidified, wrap a layer of guar gum on the surface and let stand for another 24 hours to dry.

[0136] (5) Drill holes at the designed location, install pipeline joints, and simulate injection-production wells;

[0137] (6) Use epoxy resin to cast a physical mold and form an encapsulation layer of about 0.5 cm on its surface;

[0138] (7) Let stand for 48 hours to allow the epoxy resin to fully cure;

[0139] (8) Transfer the physical mold into the pressurization device and connect the pipeline;

[0140] (9) Close the pressurizing device and fill it with liquid until the liquid pressure in the chamber reaches 10.0 MPa;

[0141] (10) Start the detection device, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air, and close the gas cylinder after the pressure at each point in the mold balances, with a cumulative air intake of 5.908 mol (132.35 L);

[0142] (11) Take the 1st layer, 6th row, and 7th column characterization unit as an example, with a pressure of 8.0 MPa, a temperature of 293.15 K, and a porosity of 10.0%, the pore space of the 1st layer, 6th row, and 7th column characterization unit is calculated to be 10 cm 3 according to formula (1);

[0143]

[0144] (12) According to the table, the compression coefficient of air at this time is 0.9874, and the initial gas storage capacity of the 1st layer, 6th row, and 7th column characterization unit is calculated to be 0.0416 mol (0.932 L) according to formula (2);

[0145]

[0146] (13) Connect the gas cylinder to the intermediate container filled with formation water, and connect the outlet end of the intermediate container to the injection inlet of the mold, and set the pressure to 8.0 MPa;

[0147] (14) Open the production control valve to simulate the gas reservoir development process, and close the valve when the experiment is finished, and record the measured pressure, water saturation, and temperature at this time, such as the pressure of the 2nd layer, 6th row, and 7th column characterization unit being 2.0 MPa, the water saturation being 68.2%, and the temperature being 290 K;

[0148] (15) According to formula (3), the water intrusion volume of the characterization unit is calculated to be 3.02 cm 3 ;

[0149]

[0150] (16) According to formula (4), the remaining gas storage space of the characterization unit is calculated to be 3.97 cm 3 ;

[0151] V′ 2,6,7 = 12.5 x 10 -6 - 8.53 x 10 -6 = 3.97 x 10 -6 m 3

[0152] (17) look up the table to get the air compression coefficient at this time, which is 0.9950, and calculate the residual storage of the characterization unit according to formula (5) as 0.0033 mol (0.0739 L), and the recovery rate is 92%;

[0153]

[0154] (18) calculate the residual storage of each characterization unit according to steps (10)-(16).

[0155] Example 4

[0156] To verify the reliability of the present application, a large-scale physical mold for multi-layer combined production of gas reservoirs is actually made, and the residual storage is calculated by monitoring the changes of pressure and water saturation at a certain position in the mold before and after gas production. The specific embodiment of the present application adopts the following technical scheme:

[0157] (1) According to the porosity of each layer and permeability K i , a formula is designed (Table 3), and a layer of 60cm×60cm×5cm simulated reservoir is pressed in the same mold;

[0158] Table 3 Porosity and permeability requirements of each simulated layer

[0159]

[0160] (2) According to the experimental requirements, each layer is divided into 5cm×5cm×5cm characterization units, and there are 12×12×1 characterization units in total;

[0161] (3) A group of monitoring probes is arranged in each characterization unit, and 12×12 probe groups are arranged on the plane, each probe group contains 2 probes, which are common probe 7 with a length of 3.5cm and first layer probe 4 with a length of 3.5cm;

[0162] (4) After standing for 24h, the physical mold is wrapped with a layer of guanidine after the cementation is cured, and then it is stood for 24h to dry;

[0163] (5) Drill holes at the designed position, install pipeline joints, and simulate injection and production wells;

[0164] (6) Use epoxy resin to cast the physical mold, and form a packaging layer of about 0.5cm on the surface;

[0165] (7) Stand for 48h to make the epoxy resin fully cured;

[0166] (8) Put the physical mold into the pressurizing device and connect the pipeline;

[0167] (9) Close the pressurizing device and fill it with liquid until the liquid pressure in the chamber reaches 10.0 MPa;

[0168] (10) Start the detection device, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air, and close the gas cylinder after the pressure at each point in the mold balances, with a cumulative air intake of 5.908 mol (132.35 L);

[0169] (11) Take the 1st layer, 6th row, and 7th column characterization unit as an example, with a pressure of 8.0 MPa, a temperature of 293.15 K, and a porosity of 10.0%, the pore space of the 1st layer, 6th row, and 7th column characterization unit is calculated to be 10 cm 3 according to formula (1);

[0170]

[0171] (12) According to the table, the compression coefficient of air at this time is 0.9874, and the initial gas storage capacity of the 1st layer, 6th row, and 7th column characterization unit is calculated to be 0.0416 mol (0.932 L) according to formula (2);

[0172]

[0173] (13) Connect the gas cylinder to the intermediate container filled with formation water, and connect the outlet end of the intermediate container to the injection inlet of the mold, and set the pressure to 8.0 MPa;

[0174] (14) Open the production control valve to simulate the gas reservoir development process, and close the valve when the experiment is finished, and record the measured pressure, water saturation, and temperature at this time, such as the pressure of the 2nd layer, 6th row, and 7th column characterization unit being 2.0 MPa, the water saturation being 68.2%, and the temperature being 290 K;

[0175] (15) According to formula (3), the water invasion volume of the characterization unit is calculated to be 3.02 cm 3 ;

[0176]

[0177] (16) According to formula (4), the remaining gas storage space of the characterization unit is calculated to be 3.97 cm 3 ;

[0178] V′ 2,6,7 = 12.5 x 10 -6 - 8.53 x 10 -6 = 3.97 x 10 -6 m 3 .

[0179] (17) The table is checked to obtain the air compression coefficient at this time, which is 0.9950. According to formula (5), the residual storage of the characterization unit is calculated as 0.0033 mol (0.0739 L), and the recovery rate is 92%;

[0180]

[0181] (18) The residual storage of each characterization unit is calculated according to steps (10) to (16).

Claims

1. A method of modeling the remaining reserves of a water-bearing gas reservoir, characterized in that, Specifically, the following steps are followed: S1, construct a gas reservoir mold with multiple simulation layers, and divide each simulation layer in the gas reservoir mold into multiple characterization units of equal volume, and calculate the number of all characterization units in the gas reservoir mold. N i With pore volume S2, Press the gas reservoir mold, then install a perforated cover plate and probes on the gas reservoir mold, and then press the gas reservoir mold a second time. After the second pressing, pour epoxy resin onto the surface of the gas reservoir mold. After the epoxy resin cures, apply confining pressure to the gas reservoir mold and add water; S3, After confining pressure, inflate the gas reservoir mold and calculate the initial gas storage capacity of the unit cell. S4, After inflation, the gas reservoir mold is vented and the water volume of each characterization unit is calculated. S5, used , Calculate the remaining pore volume of each characterization unit after water intrusion. S6, use Calculate the remaining mold reserves ; The step 1 is implemented according to the following steps: S1.1 According to the actual sequence and thickness of each producing layer of the gas reservoir, a gas reservoir mold with multiple simulation layers, the size of each simulation layer and the basic material of the artificial core required by each simulation layer are determined; S1.2 The i-th simulation layer is divided into multiple characterization unit bodies according to the thickness of the i-th layer of the simulation layer mold; The number of each characterization unit body is calculated according to formula (1), and the pore volume of each characterization unit body is calculated according to formula (2): （1） （2） In the formula: — Length of the i-th layer of the physical mold, m; — Width of the i-th layer of the physical mold, m; — Height of the i-th layer of the physical mold, m; — Number of the i-th layer of the physical mold, pieces; i — Number of the i-th layer of the physical mold, pieces; — Number of the i-th layer of the physical mold, pieces; i — Void volume of the i-th layer of the physical mold, m 3 ; — Porosity of the i-th layer of the physical mold, dimensionless; i — Porosity of the i-th layer of the physical mold, dimensionless; The step 2 is implemented according to the following steps: S2.1 The artificial core base material in S1.1 is placed in the mold in turn, and the mold with the base material is pressed once and taken out and installed with a hole cover plate and a probe, the characterization unit probe is placed along the hole on the corresponding cover plate, and slowly extruded to the upper end of the probe and the upper surface of the cover plate is flush; S2.2 The mold with all the probes assembled is sent into the pressurizing equipment again, and after being pressed and formed, it is taken out, and the hole cover plate on the mold is removed, and after the mold is solidified, epoxy resin with a thickness of 0.5-1.0 cm is poured on the surface, and after the epoxy resin is solidified, the mold is moved into the pressure container; S2.3 Connect the probe to the monitoring hole inside the pressure container with a pipeline, each monitoring hole leads to the outside of the pressure container and is connected with a valve, and after sealing the pressure container, open the data acquisition system; S2.4 Inject liquid fluid into the pressure container to apply confining pressure to the mold, and stop injecting when the confining pressure slowly rises to the set value; The step 3 is implemented according to the following steps: S3.1 Connect the gas injection port to the optional probe connection channel outside the pressure container, and then connect the gas flow meter and the pressure gas source, open the pressure gas source to slowly fill the mold with gas, and stop injecting when the monitoring pressure value of each probe is not greater than 1-1.5 MPa of the confining pressure; S3.2 Record the total gas injection amount Vtotal, the pressure Pijk of each characterization unit body and the ambient temperature T; S3.3 Calculate the initial gas storage capacity of the characterization unit body using formula (3): （3） wherein: n ijk — initial gas storage of the i-th layer j-th row k-th characterization unit, mol; P ijk — initial pressure of the i-th layer j-th row k-th characterization unit, MPa; Z ijk — gas compressibility factor of the i-th layer j-th row k-th characterization unit when the pressure is P ijk — ideal gas constant, 8.314 J / (mol•K); T— initial absolute temperature of the mold, K; The step 4 is implemented according to the following steps: S4.1 Adjust the gas injection port probe channel valve, exploit the gas inside the mold, record the cumulative gas output V through the flow meter 产 , and convert it into the total mass n' of the cumulative gas output, while recording the pressure P'ijk of each representative unit cell, the water saturation S of each representative unit cell Wijk , and the mold temperature T'. S4.2 Calculate the water-containing volume of each characterization unit body using formula (6): （4） （5） （6） wherein: n' = cumulative gas production, mol; V = cumulative gas volume, m3 总' — cumulative gas production, mol; V 产 — cumulative gas volume, m3 3 ; R 初始 - the resistance value, Ω, obtained by the probe at the initial instant; R 结束 — probe end time monitoring resistance value, Ω; V 水ijk — the i-th layer j-th row k-th list of characteristic unit intrusion water volume, m 3 ; S Wijk — the ith layer jth row kth characterization unit cell water saturation, dimensionless; The residual pore volume of each characterization unit body after water invasion is calculated according to the following formula: （7） In the formula: - the residual pore volume of the i-th layer j-th row k-th representative elementary volume after water invasion, m 3 ; The mold residual amount n' ijk The calculation formula is as follows: （8） where: — the pressure of the i-th layer j-th row k-th representative elementary volume, Pa — the gas compressibility factor at the time t; — the residual pore volume of the i-th layer j-th row k-th representative elementary volume after water invasion, m 3 ; T'— the absolute temperature of the mold after water invasion, K; R— the ideal gas constant.

2. The method for modeling remaining reserves of a water-bearing gas reservoir according to claim 1, wherein, The simulated layer dimensions include thickness, porosity , permeability.

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