Simulation calculation method for residual reserves of water-containing gas reservoir

Abstract

The invention discloses a simulation calculation method for residual reserves of a water-containing gas reservoir, which is implemented according to the following steps: S1, manufacturing a gas reservoir mold with a plurality of simulation layers, dividing each simulation layer in the gas reservoir mold into characterization unit bodies, and calculating the number Ni and pore volume of the characterization unit bodies in the gas reservoir mold; s2, the gas reservoir mold is pressed, then a cover plate with holes and a probe are installed on the gas reservoir mold, then the gas reservoir mold is pressed for the second time, epoxy resin is poured on the surface of the gas reservoir mold after the second time of pressing, and after the epoxy resin is cured, confining pressure is applied to the gas reservoir mold, and water is added; s3, inflating the gas reservoir mold after confining pressure, and calculating the initial gas storage capacity of the characterization unit body; s4, exhausting the gas reservoir mold after inflation is finished, and calculating the water volume of each characterization unit body; s5, calculating the residual pore volume of each characterization unit body after water invasion; and S6, calculating the remaining reserves of the mold. The problem that the remaining reserves at different positions of the mold cannot be calculated in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of research on the distribution of remaining reserves of water-containing gas reservoirs, and in particular relates to a simulation calculation method for the remaining reserves of water-containing gas reservoirs. Background Art

[0002] During the development of water-bearing gas reservoirs, as the energy of the gas reservoir decreases, formation water invades the gas reservoir, causing water to appear in the gas well prematurely, resulting in a significant reduction in production. In severe cases, it may even cause the gas well to shut down. Indoor physical simulation experiments can well simulate the water invasion process of gas reservoirs. On the one hand, the mold used in the experiment can retain the heterogeneous characteristics of the original reservoir to the greatest extent 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 during the development of water-bearing gas reservoirs, providing guidance for the formulation of water control measures for gas reservoirs. In addition to the pressure and water saturation at each position in the mold, the reserve utilization is also an important indicator for studying the water invasion dynamics of water-bearing gas reservoirs. Therefore, there is an urgent need for a method to calculate the remaining reserves at each position of the multi-layer combined production physical mold for water-bearing gas reservoirs.

[0003] At present, there are many studies on the physical simulation of water invasion process in water-bearing gas reservoirs, but few scholars have explored in depth the calculation method of remaining reserves in the physical simulation experiment. In the past, the calculation of remaining reserves in the physical mold was based on the entire physical mold. The calculation result was single, and only the total remaining reserves of the mold could be calculated, but the remaining reserves at different positions of the mold could not be calculated. In summary, establishing a calculation method for the remaining reserves distribution of the physical mold of water-bearing gas reservoirs is of great significance for gas reservoir water control, production capacity prediction and other work. Summary of the invention

[0004] The purpose of the present invention is to provide a simulation calculation method for the remaining reserves of a water-containing gas reservoir, which solves the problem in the prior art that the remaining reserves at different positions of a mold cannot be calculated.

[0005] The technical solution adopted by the present invention is a simulation calculation method for the remaining reserves of water-containing gas reservoirs, which is specifically implemented according to the following steps:

[0006] S1, make a gas reservoir mold with multiple simulation layers, and divide each simulation layer in the gas reservoir mold into multiple characterization units with equal volume, and calculate the number N of all characterization units in the gas reservoir mold i and pore volume V ijk ;

[0007] S2, pressing the gas reservoir mold, installing a cover plate with holes and a probe on the gas reservoir mold, and then pressing the gas reservoir mold for the second time. After the second pressing, pouring epoxy resin on the surface of the gas reservoir mold, and applying confining pressure to the gas reservoir mold and adding water after the epoxy resin is cured;

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

[0009] S4, after the inflation is completed, the gas reservoir mold is vented and the water content of each characterization unit is calculated

[0010] S5, using V ijk , Calculate the remaining pore volume V of each characterization unit after water invasion i ' jk ;

[0011] S6, using V i ' jk Calculate the remaining mold reserve n i ' jk .

[0012] The present invention is also characterized in that:

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

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

[0015] S1.2 dividing the i-th simulation layer into a plurality of characterization units according to the thickness of the i-th layer of the simulation layer mold;

[0016] S1.3 The calculation formula for the number of each characterization unit body is shown in formula (1), and the calculation formula for the pore volume of each characterization unit body is shown in formula (2):

[0017]

[0018]

[0019] Where: L i ——The length of the physical mold layer i, m; W i ——Width of the physical mold layer i, m; H i ——Height of the physical mold layer i, m; N i ——Number of units representing the i-th layer, V ijk ——The pore volume of the characteristic unit cell in the i-th layer, j-th row, and k-th column of the physical mold, m 3 ; ——Porosity of the i-th layer of the physical mold, dimensionless.

[0020] The simulated layer dimensions include thickness, porosity φ i , permeability.

[0021] Step 2 is implemented as follows:

[0022] S2.1 Place the artificial core base materials described in S1.1 into the mold in sequence, press the mold containing the base materials once, take it out and install the perforated cover plate and probe, put the characterization unit probe along the hole on the corresponding cover plate, and slowly squeeze it until the upper end of the probe is flush with the upper surface of the cover plate;

[0023] S2.2 Send the mold with all the probes assembled into the pressurizing device again, take it out after pressing and forming, and remove the cover plate with holes on the mold. After the mold is solidified, pour epoxy resin with a thickness of 0.5 to 1.0 cm on the surface. After the epoxy resin is solidified, move the mold into the high-pressure container;

[0024] S2.3 Use pipelines to connect the probes to the monitoring holes inside the high-pressure container. Each monitoring hole leads to the outside of the high-pressure container and is connected to a valve. After sealing the high-pressure container, turn on the data acquisition system;

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

[0026] Step 3 is implemented as follows:

[0027] S3.1 Select a probe connection channel outside the high-pressure container as the gas injection port, connect the gas flow meter and high-pressure gas source in sequence, open the high-pressure gas source to slowly fill the mold with gas, and stop gas injection when the pressure values ​​monitored by each probe are no more than 1-1.5MPa of the confining pressure;

[0028] S3.2 Record the cumulative intake volume V of saturated gas 总 , each characterization unit body pressure P ijk , ambient temperature T;

[0029] S3.3 Use formula (3) to calculate the initial gas storage capacity of the characterization unit:

[0030]

[0031] Where: n ijk —initial gas storage capacity of the characteristic unit cell in the i-th layer, j-th row, and k-th column, mol; P ijk —initial pressure of the characteristic unit cell in the i-th layer, j-th row, and k-th column, MPa; Z ijk —The pressure of the characteristic unit cell in the i-th layer, j-th row and k-th column is P ijk Gas compressibility factor at , dimensionless; R—ideal gas constant, 8.314 J / (mol·K); T—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 the gas inside the mold and record the cumulative gas output V through the flow meter 产 , which is converted into the cumulative mass of gas produced n' 总 , and simultaneously record the pressure P'ijk of each characterization unit, the water saturation S of each characterization unit Wijk , mold temperature T';

[0034] S4.2 Use formula (6) to calculate the water content of each characterization unit:

[0035]

[0036]

[0037]

[0038] Where: n′ 总 —The total amount of gas produced, mol; V 产 —Cumulative gas output volume, m3; S Wijk —Water saturation of the characteristic unit cell in the i-th layer, j-th row, and k-th column, dimensionless; Rinitial—The resistance value monitored at the initial moment of the probe, Ω; Rend—The resistance value monitored at the end moment of the probe, Ω; V 水ijk —The volume of water intrusion of the characteristic unit body in the i-th layer, j-th row and k-th column, m3; S Wijk —water saturation of the characteristic unit volume in the i-th layer, j-th row, and k-th column, dimensionless;

[0039] The calculation formula of the remaining pore volume of each characterization unit after water invasion is as follows:

[0040]

[0041] Where: V i ' jk —The residual pore volume of the characteristic unit in the i-th layer, j-th row and k-th column after water invasion, m3;

[0042] Remaining reserve of mold n' ijk The calculation formula is as follows:

[0043]

[0044] Where: Z i ' jk —The pressure of the characteristic unit cell in the i-th layer, j-th row and k-th column is P i ' jk Gas compressibility factor at ; V i ' jk —Residual pore volume of the characteristic unit cell in the i-th layer, j-th row and k-th column after water invasion, m3; T'—absolute temperature of the mold after water invasion, K; R——ideal gas constant.

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

[0046] (1) The present invention can calculate the remaining reserves at various positions in the experimental mold, fully reflecting the impact of intra-layer and inter-layer heterogeneity on gas reservoir development during multi-layer production; (2) Based on the real-time pressure, water saturation, temperature and other acquisition results, the gas production characteristics of any position of the flat large mold at any time can be calculated; (3) The present invention takes into account the impact of the volume of intruded water on the remaining reserves calculation process, making the calculation result more accurate; (4) Compared with the conventional reserve calculation method, the calculation core of the present invention is the mass of gas, and the conversion of gas volume under different pressures can be ignored. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0050] Figure 4 It is a cross-sectional diagram of a single probe structure.

[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 interface, 9. External electrode interface, 10. External electrode, 11. Insulation layer, 12. Internal electrode. DETAILED DESCRIPTION

[0052] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0053] (1) According to the actual sequence and thickness of each production layer in the gas reservoir, determine the number of layers of the multi-layer commingled production physical gas reservoir mold and the size of each simulated layer, including thickness, porosity φ i , permeability, and then determine the type and quality of artificial core base materials required for each simulation layer. i Divide the i-th layer into two layers with side length H i The number of characterization units is calculated using formula (1) to obtain the number of probes required for the i-th layer as the number of characterization units N. i , use formula (2) to calculate the pore volume V of the unit cell ijk , mix the base materials of the same layer evenly and keep them for later use:

[0054]

[0055]

[0056] Where: L i ——The length of the physical mold layer i, m; W i ——Width of the physical mold layer i, m; H i ——Height of the physical mold layer i, m; N i ——Number of units representing the i-th layer, V ijk ——The pore volume of the characteristic unit cell in the i-th layer, j-th row, and k-th column of the physical mold, m 3 ; ——Porosity of the i-th layer of the physical mold, dimensionless.

[0057] (2) Place the mixed artificial core base materials into the mold in the actual order of the production layers of the gas reservoir, put the mold with the base materials into the pressurizing equipment, press it once with a low pressure, and then take it out. Cover it with a 1.5 cm thick perforated cover plate, and select the length of the probe l in the i-th layer of the mold. i The probe is the sum of the thickness of all simulation layers on the i-th layer and half of the thickness of the i-th simulation layer. The diameter of the hole on the cover is slightly larger than the diameter of the probe used. The number of holes is the number of probes Ni in each layer. The hole position is arranged at the geometric center of the horizontal plane of the i-th layer, j-row, k-column characterization unit. Place the i-th layer, j-row, k-column characterization unit probe along the corresponding hole on the cover and slowly squeeze it until the upper end of the probe is flush with the upper surface of the cover.

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

[0059] (4) Use pipelines to connect the probe to the monitoring holes inside the high-pressure container. 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. When the confining pressure slowly rises to the experimental required value, stop the injection.

[0060] (5) Select a probe connection channel outside the high-pressure container as the gas injection port, connect the gas flow meter and high-pressure gas source in sequence, turn on the high-pressure gas source to slowly fill the mold with gas, and stop the gas injection when the pressure values ​​monitored by each probe are all less than 1-1.5 MPa of the surrounding pressure, remove the high-pressure gas source, and record the cumulative intake volume V of the saturated gas 总 , each characterization unit body pressure P ijk , ambient temperature T, calculate the initial gas storage capacity of the characteristic unit in the i-th layer, j-th row, and k-th column according to (3):

[0061]

[0062] Where: n ijk ——initial gas storage capacity of the characteristic unit cell in the i-th layer, j-th row, and k-th column, mol; P ijk ——initial pressure of the characteristic unit cell in the i-th layer, j-th row, k-th column, MPa; Z ijk ——The pressure of the characteristic unit cell in the i-th layer, j-th row, and k-th column is P ijk Gas compressibility factor at , dimensionless; R——ideal gas constant, 8.314 J / (mol·K); T——initial absolute temperature of the mold, K.

[0063] (6) Adjust the valve of the gas injection port probe channel to extract the gas inside the mold and record the cumulative gas output V through the flow meter 产 , which is converted into the cumulative mass of gas produced n' 总 , and record the pressure P' of each characterization unit at the same time ijk , water saturation S of each characterization unit Wijk , mold temperature T', calculate the water volume of each characterization unit according to formula (6):

[0064]

[0065]

[0066]

[0067] Where: n′ 总 —The total amount of gas produced, mol; V 产 —Cumulative gas output volume, m3; S Wijk —water saturation of the characteristic unit volume in the i-th layer, j-th row, and k-th column, dimensionless; R 初始 —The resistance value monitored at the initial moment of the probe, Ω; R 结束 —The resistance value monitored at the end of the probe, Ω; V 水ijk —The volume of water intrusion of the characteristic unit body in the i-th layer, j-th row and k-th column, m3; S Wijk —Water saturation of the characteristic unit volume in the i-th layer, j-th row, and k-th column, dimensionless:

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

[0069]

[0070] Where: V′ ijk —Remaining pore volume of the characteristic unit after water invasion in the i-th layer, j-th row and k-th column, m3.

[0071] (8) According to formula (8), the remaining reserves of each characterization unit can be calculated to obtain the remaining reserves distribution of multi-layer combined mining large physical mold:

[0072]

[0073] Where: Z′ ijk —The pressure of the characteristic unit cell in the i-th layer, j-th row and k-th column is P′ ijk Gas compressibility factor at ; V′ ijk —Residual pore volume of the characteristic unit cell in the i-th layer, j-th row and k-th column after water invasion, m3; T'—absolute temperature of the mold after water invasion, K; R——ideal gas constant.

[0074] Example 1

[0075] In order to verify the reliability of the present invention, Figure 1 , a large-scale physical mold for multi-layer combined production of gas reservoirs was actually made, and the remaining reserves were calculated by monitoring the changes in pressure and water saturation before and after gas production at a certain position in the mold. The specific implementation of the present invention is implemented by the following technical solutions:

[0076] (1) According to the porosity of each layer and permeability K i It is required to design three formulations (Table 1) and press three layers of 60cm×60cm×5cm simulated reservoirs in the same mold in sequence;

[0077] Table 1 Porosity and permeability requirements for each simulated layer

[0078]

[0079] (2) According to the experimental requirements, each layer is divided into 5 cm × 5 cm × 5 cm characterization units, with a total of 12 × 12 × 3 characterization units;

[0080] (3) Arrange a set of monitoring probes in each characterization unit body, and arrange 12×12 probe groups on the plane, each probe group contains 4 probes, namely, a common probe 13.5 cm long, a first layer probe 4, a length of 3.5 cm, a second layer probe 5, a length of 8.5 cm and a third layer probe 6, a length of 13.5 cm;

[0081] (4) Standing for 24 hours, after the cement in the physical mold solidifies, wrap a layer of guar gum on the surface, and standing for another 24 hours to dry;

[0082] (5) Drill holes at the designed locations, install pipeline joints, and simulate injection and production wells;

[0083] (6) using epoxy resin to cast a physical mold to form an encapsulation layer of about 0.5 cm on its surface;

[0084] (7) Leave it to stand for 48 hours to allow the epoxy resin to fully cure;

[0085] (8) Transfer the physical mold into the pressurizing device and connect the pipeline;

[0086] (9) Close 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 testing equipment, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air until the pressure at each point of the mold is balanced, then close the gas cylinder. The cumulative air intake is 13.88 mol (310.96 L);

[0088] (11) Taking the characteristic unit of the 2nd layer, 6th row, 7th column 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 characteristic unit of the 2nd layer, 6th row, 7th column is 10 cm 3 ;

[0089]

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

[0091]

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

[0093] (14) Open the production control valve to simulate the gas reservoir development process. When the experiment is over, close the valve and record the pressure, water saturation and temperature at each point. For example, the pressure of the characteristic unit in the 7th column of 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 volume of water intrusion into 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 =10×10 -6 -3.14×10 -6 =6.86×10 -6 m 3 .

[0098] (17) The air compression coefficient at this time is 0.9812. According to formula (5), the remaining reserves of the characterization unit are calculated to be 0.0211 mol (0.474 L), and the recovery rate is 35%;

[0099]

[0100] (18) Calculate the remaining reserves of each characterization unit according to steps (10) to (16).

[0101] Example 2

[0102] In order to verify the reliability of the present invention, a large-scale physical mold for multi-layer combined production of gas reservoirs was actually made, and the remaining reserves were calculated by monitoring the changes in pressure and water saturation before and after gas production at a certain position in the mold. The specific implementation of the present invention is implemented by the following technical solutions:

[0103] (1) According to the porosity of each layer and permeability K i It is required to design two formulations (Table 2) and press two layers of 60cm×60cm×5cm simulated reservoirs in the same mold in sequence;

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

[0105]

[0106] (2) According to the experimental requirements, each layer is divided into 5 cm × 5 cm × 5 cm characterization units, with a total of 12 × 12 × 2 characterization units;

[0107] (3) Arrange a set of monitoring probes in each characterization unit body, and arrange 12×12 probe groups on the plane, each probe group contains 4 probes, namely, a common probe 7 with a length of 8.5 cm, a first layer probe 4 with a length of 3.5 cm, and a second layer probe 5 with a length of 8.5 cm;

[0108] (4) Standing for 24 hours, after the cement in the physical mold solidifies, wrap a layer of guar gum on the surface, and standing for another 24 hours to dry;

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

[0110] (6) using epoxy resin to cast a physical mold to form an encapsulation layer of about 0.5 cm on its surface;

[0111] (7) Leave it to stand for 48 hours to allow the epoxy resin to fully cure;

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

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

[0114] (10) Start the testing equipment, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air until the pressure at each point of the mold is balanced, then close the gas cylinder. The cumulative air intake is 9.45 mol (211.75 L);

[0115] (11) Taking the characteristic unit of the 2nd layer, 6th row, 7th column as an example, the pressure is 8.0 MPa, the temperature is 293.15 K, and the porosity is 6.0%. According to formula (1), the pore space of the characteristic unit of the 2nd layer, 6th row, 7th column is 10 cm 3 ;

[0116]

[0117] (12) The compression coefficient of air at this time is 0.9874. According to formula (2), the initial gas storage capacity of the characteristic unit cell in the 2nd layer, 6th row, and 7th column is 0.0249 mol (0.558 L);

[0118]

[0119] (13) Connect the gas cylinder to an intermediate container filled with formation water, connect the outlet of the intermediate container to the injection port 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. When the experiment is over, close the valve and record the pressure, water saturation and temperature at each point. For example, the pressure of the characteristic unit in the 7th column of the 6th row of the 2nd layer is 6.0 MPa, the water saturation is 40.2%, and the temperature is 290 K.

[0121] (15) According to formula (3), the volume of water intrusion into 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 =7.5×10 -6 -3.02×10 -6 =4.48×10 -6 m 3 .

[0125] (17) The air compression coefficient at this time is 0.9901. According to formula (5), the remaining reserves of the characterization unit are calculated to be 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] In order to verify the reliability of the present invention, a large-scale physical mold for multi-layer combined production of gas reservoirs was actually made, and the remaining reserves were calculated by monitoring the changes in pressure and water saturation before and after gas production at a certain position in the mold. The specific implementation of the present invention is implemented by the following technical solutions:

[0130] (1) According to the porosity of each layer and permeability K i It is required to design a formula (Table 3) and press one layer of 60cm×60cm×5cm simulated reservoir in the same mold;

[0131] Table 3 Porosity and permeability requirements for each simulated layer

[0132]

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

[0134] (3) Arrange a set of monitoring probes in each characterization unit body, and arrange 12×12 probe groups on the plane, each probe group contains 2 probes, namely, a common probe 7 with a length of 3.5 cm and a first layer probe 4 with a length of 3.5 cm;

[0135] (4) Standing for 24 hours, after the cement in the physical mold solidifies, wrap a layer of guar gum on the surface, and standing for another 24 hours to dry;

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

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

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

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

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

[0141] (10) Start the testing equipment, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air until the pressure at each point of the mold is balanced, then close the gas cylinder. The cumulative air intake is 5.908 mol (132.35 L);

[0142] (11) Taking the characteristic unit of the 1st layer, 6th row, 7th column as an example, the pressure is 8.0 MPa, the temperature is 293.15 K, and the porosity is 10.0%. According to formula (1), the pore space of the characteristic unit of the 1st layer, 6th row, 7th column is 10 cm 3 ;

[0143]

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

[0145]

[0146] (13) Connect the gas cylinder to an intermediate container filled with formation water, connect the outlet of the intermediate container to the injection port 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. When the experiment is over, close the valve and record the pressure, water saturation and temperature at each point. For example, the pressure of the characteristic unit in the 7th column of the 6th row of the 2nd layer is 2.0 MPa, the water saturation is 68.2%, and the temperature is 290 K.

[0148] (15) According to formula (3), the volume of water intrusion into 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 =12.5×10 -6 -8.53×10 -6 =3.97×10 -6 m 3

[0152] (17) The air compression coefficient at this time is 0.9950. According to formula (5), the remaining reserves of the characterization unit are calculated to be 0.0033 mol (0.0739 L), and the recovery rate is 92%;

[0153]

[0154] (18) Calculate the remaining reserves of each characterization unit according to steps (10) to (16).

[0155] Example 4

[0156] In order to verify the reliability of the present invention, a large-scale physical mold for multi-layer combined production of gas reservoirs was actually made, and the remaining reserves were calculated by monitoring the changes in pressure and water saturation before and after gas production at a certain position in the mold. The specific implementation of the present invention is implemented by the following technical solutions:

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

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

[0159]

[0160] (2) According to the experimental requirements, each layer is divided into 5 cm × 5 cm × 5 cm characterization units, with a total of 12 × 12 × 1 characterization units;

[0161] (3) Arrange a set of monitoring probes in each characterization unit body, and arrange 12×12 probe groups on the plane, each probe group contains 2 probes, namely, a common probe 7 with a length of 3.5 cm and a first layer probe 4 with a length of 3.5 cm;

[0162] (4) Standing for 24 hours, after the cement in the physical mold solidifies, wrap a layer of guar gum on the surface, and standing for another 24 hours to dry;

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

[0164] (6) using epoxy resin to cast a physical mold to form an encapsulation layer of about 0.5 cm on its surface;

[0165] (7) Leave it to stand for 48 hours to allow the epoxy resin to fully cure;

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

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

[0168] (10) Start the testing equipment, open the gas cylinder, set the inlet pressure to 8.0 MPa, fill the physical mold with air until the pressure at each point of the mold is balanced, then close the gas cylinder. The cumulative air intake is 5.908 mol (132.35 L);

[0169] (11) Taking the characteristic unit of the 1st layer, 6th row, 7th column as an example, the pressure is 8.0 MPa, the temperature is 293.15 K, and the porosity is 10.0%. According to formula (1), the pore space of the characteristic unit of the 1st layer, 6th row, 7th column is 10 cm 3 ;

[0170]

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

[0172]

[0173] (13) Connect the gas cylinder to an intermediate container filled with formation water, connect the outlet of the intermediate container to the injection port 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. When the experiment is over, close the valve and record the pressure, water saturation and temperature at each point. For example, the pressure of the characteristic unit in the 7th column of the 6th row of the 2nd layer is 2.0 MPa, the water saturation is 68.2%, and the temperature is 290 K.

[0175] (15) According to formula (3), the volume of water intrusion into 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 =12.5×10 -6 -8.53×10 -6 =3.97×10 -6 m 3 .

[0179] (17) The air compression coefficient at this time is 0.9950. According to formula (5), the remaining reserves of the characterization unit are calculated to be 0.0033 mol (0.0739 L), and the recovery rate is 92%;

[0180]

[0181] (18) Calculate the remaining reserves of each characterization unit according to steps (10) to (16).

Claims

1. A simulation method for calculating the remaining reserves of a water-bearing gas reservoir, characterized in that: The implementation is specifically carried out in 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 multiple characterization units with equal volumes, and the number N of all characterization units in the gas reservoir mold is calculated. i and pore volume V ijk ; S2, press the gas reservoir mold, then install the perforated cover plate and the probe on the gas reservoir mold, and then press the gas reservoir mold for the second time. After the second pressing, pour epoxy resin on the surface of the gas reservoir mold. After the epoxy resin is cured, apply confining pressure to the gas reservoir mold and add water; S3, inflate the gas reservoir mold after confining pressure, and calculate the initial gas storage capacity n of the characterization unit ijk ; S4, after the inflation is completed, the gas reservoir mold is vented and the water volume of each characterization unit is calculated Using V ijk , Calculate the remaining pore volume V′ of each characterization unit after water invasion ijk ; S6, use V′ ijk Calculate the remaining mold reserve n' ijk .

2. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 1 is characterized in that: The step 1 is specifically implemented according to the following steps: S1.1 According to the actual sequence and thickness of each production layer in the gas reservoir, determine the gas reservoir mold with multiple simulation layers, the size of each simulation layer and the artificial core base material required for each simulation layer; S1.2 dividing the i-th simulation layer into a plurality of characterization units according to the thickness of the i-th layer of the simulation layer mold; The calculation formula for the number of each characterization unit body described in S1.3 is shown in formula (1), and the calculation formula for the pore volume of each characterization unit body is shown in formula (2): Where: L i ——The length of the physical mold layer i, m; W i ——Width of the physical mold layer i, m; H i ——Height of the physical mold layer i, m; N i ——Number of units representing the i-th layer, V ijk - —Pore volume of characteristic unit cell in layer i, row j, column k of physical mold, m 3 ; ——Porosity of the i-th layer of the physical mold, dimensionless.

3. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 2 is characterized in that: The simulation layer dimensions include thickness, porosity φ i , permeability.

4. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 2 is characterized in that: The step 2 is specifically implemented according to the following steps: S2.1 Place the artificial core base materials described in S1.1 into the mold in sequence, press the mold containing the base materials once, take it out and install the perforated cover plate and probe, put the characterization unit probe along the hole on the corresponding cover plate, and slowly squeeze it until the upper end of the probe is flush with the upper surface of the cover plate; S2.2 Send the mold with all the probes assembled into the pressurizing device again, take it out after pressing and forming, and remove the cover plate with holes on the mold. After the mold is solidified, pour epoxy resin with a thickness of 0.5 to 1.0 cm on the surface. After the epoxy resin is solidified, move the mold into the pressure vessel; S2.3 Use pipelines to connect the probes to the monitoring holes inside the pressure vessel. Each monitoring hole leads to the outside of the pressure vessel and is connected to a valve. After sealing the pressure vessel, turn on the data acquisition system. S2.4 Liquid fluid is injected into the pressure vessel to apply confining pressure to the mold, and the injection is stopped when the confining pressure slowly rises to the set value.

5. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 4 is characterized in that: The step 3 is specifically implemented according to the following steps: S3.1 Select a probe connection channel outside the pressure vessel as the gas injection port, connect the gas flow meter and the pressure gas source in sequence, open the pressure gas source to slowly fill the mold with gas, and stop gas injection when the pressure values ​​monitored by each probe are no more than 1-1.5MPa of the confining pressure; S3.2 Record the cumulative intake volume V of saturated gas 总 , each characterization unit body pressure P ijk , ambient temperature T; S3.3 Use formula (3) to calculate the initial gas storage capacity of the characterization unit: Where: n ijk —initial gas storage capacity of the characteristic unit cell in the i-th layer, j-th row, and k-th column, mol; P ijk —initial pressure of the characteristic unit cell in the i-th layer, j-th row, k-th column, MPa; Z ijk —The pressure of the characteristic unit cell in the i-th layer, j-th row and k-th column is P ijk Gas compressibility factor at , dimensionless; R—ideal gas constant, 8.314 J / (mol·K); T—initial absolute temperature of the mold, K.

6. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 5 is characterized in that: The step 4 is specifically implemented according to the following steps: S4.1 Adjust the valve of the gas injection port probe channel to extract the gas inside the mold and record the cumulative gas output V through the flow meter 产 , which is converted into the cumulative mass of gas produced n' 总 , and simultaneously record the pressure P'ijk of each characterization unit, the water saturation S of each characterization unit Wijk , mold temperature T'; S4.2 Use formula (6) to calculate the water content of each characterization unit: Where: n' 总' —The total amount of gas produced, mol; V 产 —Cumulative gas volume produced, m3; SWijk—water saturation of the characteristic unit volume in the i-th layer, j-th row, and k-th column, dimensionless; R 初始 —The resistance value monitored at the initial moment of the probe, Ω; R 结束 —The resistance value monitored at the end of the probe, Ω; V 水ijk —Volume of water intrusion of the characteristic unit volume in the i-th layer, j-th row, and k-th column, m3; SWijk—Water saturation of the characteristic unit volume in the i-th layer, j-th row, and k-th column, dimensionless.

7. The simulation calculation method of remaining reserves of water-containing gas reservoirs according to claim 6 is characterized in that: The calculation formula for the remaining pore volume of each characterization unit after water invasion is as follows: Where: V i ' jk —Remaining pore volume of the characteristic unit after water invasion in the i-th layer, j-th row and k-th column, m3.

8. The simulation calculation method for remaining reserves of water-containing gas reservoirs according to claim 7 is characterized in that: The remaining reserve of the mold is n' ijk The calculation formula is as follows: Where: Z i ' jk —The pressure of the characteristic unit cell in the i-th layer, j-th row and k-th column is P i ' jk Gas compressibility factor at ; V i ' jk —Residual pore volume of the characteristic unit cell in the i-th layer, j-th row and k-th column after water invasion, m3; T'—absolute temperature of the mold after water invasion, K; R——ideal gas constant.

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