Experimental device and experimental method for simulating development of strongly heterogeneous multilayer series water-bearing gas reservoirs

Abstract

The application discloses a kind of experimental device and experimental method for simulating the development of strong heterogeneous multilayer series water-containing gas reservoir, and relates to the technical field of gas field development, including edge water simulation unit, bottom water simulation unit, multilayer series reservoir simulation unit, longitudinal crack-containing reservoir simulation unit, back pressure control unit, gas and water monitoring unit and original fluid saturation unit;The multilayer series reservoir simulation unit is a horizontal multiple-parallel structure, one side of the multiple-parallel structure is connected to the edge water simulation unit, and the other side is connected to the back pressure control unit;The back pressure control unit is connected to the gas and water monitoring unit through a gas and water separation meter;The longitudinal crack-containing reservoir simulation unit includes multiple full-diameter core holders connected in series vertically, and the bottom full-diameter core holder is connected to the bottom water simulation unit at the bottom;The application realizes the simulation of strong heterogeneous longitudinal high-angle crack development in the hydrochloride rock multilayer series water-containing gas reservoir through the effective combination of full-diameter core holders and long core holders.

Description

Technical Field

[0001] This invention relates to the field of gas field development technology, and more specifically to the field of experimental apparatus and methods for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs. Background Technology

[0002] The developed carbonate gas reservoirs in the Sichuan Basin are mostly complex multi-layered water-bearing gas reservoirs with both edge and bottom water. During the development of these gas reservoirs, they face the risks of edge water advance and bottom water coning. At the same time, high-angle fractures are generally developed inside these gas reservoirs, which further intensifies the water intrusion and makes prediction more difficult.

[0003] Currently, simulation experiments for the development of water-bearing gas reservoirs in carbonate rocks mainly employ microscopic visualization devices, three-dimensional sand-filled models, and full-diameter core samples to simulate the development process. For example, CN201720791169.2 discloses an experimental device for the development of heterogeneous multi-layered gas reservoirs, published on 2017-12-29. However, these experimental devices are insufficient to simulate the dynamic development process of strongly heterogeneous multi-layered water-bearing gas reservoirs in the Sichuan Basin. Microscopic visualization and full-diameter devices are inadequate to reflect reservoir heterogeneity, and large three-dimensional sand-filled models are primarily used in the development of sandstone gas reservoirs.

[0004] However, there are very few simulation devices for multi-layered hydrochloric acid rock formations with edge and bottom water in the Sichuan Basin, characterized by strong heterogeneity and high-angle vertical fractures, which greatly limits the efficient development of this type of gas reservoir. Solving the above-mentioned technical problems has become the focus of efforts in the field. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned technical problems by providing an experimental device and method for simulating the development of highly heterogeneous multi-layered hydrochloric gas reservoirs. This invention achieves the simulation of highly heterogeneous multi-layered hydrochloric acid rock reservoirs with high-angle vertical fractures through the effective combination of full-diameter core holders and long core holders.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0007] The experimental setup for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs includes a side water simulation unit, a bottom water simulation unit, a multi-layered reservoir simulation unit, a vertically fractured reservoir simulation unit, a back pressure control unit, a gas-water monitoring unit, and a raw fluid saturation unit.

[0008] The multi-layer reservoir simulation unit is a horizontally arranged multi-layer parallel structure. One side of the multi-layer parallel structure is connected to the edge water simulation unit, and the other side is connected to the back pressure control unit. The back pressure control unit is connected to the gas-water monitoring unit through the gas-water separation meter. Each layer of the parallel structure includes two long core holders arranged in series and horizontally.

[0009] The vertical fractured reservoir simulation unit includes multiple full-diameter core holders connected in series vertically. The number of full-diameter core holders is the same as the number of layers in the multi-layer parallel structure. Except for the bottom full-diameter core holder, all full-diameter core holders are connected sequentially between adjacent layers in the multi-layer parallel structure. The bottom full-diameter core holder is connected to the bottom water simulation unit.

[0010] The original fluid saturation unit is compatible with all saturated long core holders and full-diameter core holders.

[0011] Furthermore, the multi-layer reservoir simulation unit has a three-layer parallel structure, with each layer consisting of two long core holders connected in series and horizontally arranged. The vertical fractured reservoir simulation unit includes three full-diameter core holders connected in series vertically.

[0012] The top full-diameter core holder is located between the first layer of long core holders and the second layer of long core holders. One end of the top full-diameter core holder is connected to the pipeline between the two long core holders in the first layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the second layer through a pipeline.

[0013] The central full-diameter core holder is located between the second-layer long core holder and the third-layer long core holder. One end of the central full-diameter core holder is connected to the pipeline between the two long core holders in the second layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the third layer through a pipeline.

[0014] One end of the bottom full-diameter core holder is connected to the pipeline between the two long core holders in the third layer, and the other end is connected to the bottom water simulation unit.

[0015] Furthermore, the original fluid saturation unit includes a formation CH4 intermediate container, a tracer intermediate container, a gas mixing and sample preparation device, a formation water intermediate container, a vacuum pump, and a high-pressure injection pump. The CH4 intermediate container, tracer intermediate container, gas mixing and sample preparation device, and formation water intermediate container are connected in parallel. The high-pressure injection pump is connected to the parallel connection pipeline, and after being connected in parallel, it is connected to a long core holder or a full-diameter core holder through a pipeline. The vacuum pump is connected to the long core holder or the full-diameter core holder through a pipeline.

[0016] Furthermore, the edge water simulation unit includes an edge water injection pump and an intermediate edge water container for storing high-pressure saturated sodium bromide solution, with the edge water injection pump connected to one side of the multi-layer parallel structure via the intermediate edge water container; the bottom water simulation unit includes a bottom water injection pump and an intermediate bottom water container for storing high-pressure saturated potassium chloride solution, with the bottom water injection pump connected to the bottom full-diameter core holder via the intermediate bottom water container.

[0017] Furthermore, the core in the long core holder is composed of 10 small cores with a diameter of 2.5 cm and a length of 5 cm. The combined long core after the small cores are connected in series has a length of 0.5 m. The combined long core is placed in a rubber tube. There is an annular space between the outside of the rubber tube and the long core holder. Hydraulic oil is injected into the annular space.

[0018] The core in the full-diameter core holder consists of two longitudinally fractured reservoir cores obtained directly after drilling. The longitudinally fractured reservoir cores are 10cm in diameter and 25cm in length. The cores are connected in series and are 0.5m long. The connected cores are placed in rubber sleeve A. There is an annular space between the outside of rubber sleeve A and the full-diameter core holder. Hydraulic oil is injected into the annular space.

[0019] Furthermore, both the outlet and inlet ends of the long core holder or the full-diameter core holder are equipped with pipeline valves and pressure monitors. The long core holder or the full-diameter core holder is also connected to a confining pressure pump for controlling the confining pressure of the core.

[0020] Furthermore, the back pressure control unit includes a back pressure valve, a gas intermediate container, and a back pressure pump. The back pressure pump is connected to the gas intermediate container, and the gas intermediate container is connected to the back pressure valve. The back pressure valve is located on the pipeline between the other side of the multi-layer parallel structure and the gas-water separator meter.

[0021] Furthermore, the gas-water monitoring unit includes a GC / MS gas chromatography-mass spectrometer and an online ion chromatograph, which are connected in parallel and then connected to the gas-water separation meter.

[0022] The experimental method for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs includes the following steps:

[0023] Step 1, Simulation of gas reservoir development: The original fluid saturation of the long core holder and the full-diameter core holder is completed through the original fluid saturation unit, so that the fluid in each holder contains different gas tracer components with a concentration of 20%.

[0024] Step 2: Connect the saturated long core holder and the full-diameter core holder to the experimental pipeline, open the outlet and inlet valves of all holders, control the pressure drop rate at the total outlet, release the saturated fluid inside the core at the set pressure drop rate, and simultaneously input the gas and liquid obtained from the gas-liquid separator into the gas chromatograph / mass spectrometer and the online ion chromatograph, respectively, and record the various parameter data online in real time until the pressure at the outlet reaches the waste pressure and stop the experiment.

[0025] Step 3: By analyzing the changes in pressure data from the pressure sensors at the inlet and outlet of the gripper, combined with the changes in the concentration and composition of the gas tracer in the gas chromatograph and the changes in the concentration of liquid ions in the online ion chromatograph, we can assess the degree of utilization of the original gas in different grippers during the development of highly heterogeneous multilayer water-bearing fractured gas reservoirs, as well as the mechanism of edge and bottom water intrusion in the fractured reservoir.

[0026] The beneficial effects of this invention are as follows:

[0027] 1. This invention achieves the simulation of multi-layered hydrochloric acid rocks with highly heterogeneous vertical high-angle fractures through the effective combination of full-diameter core holders and long core holders. The full-diameter core is directly selected from a complete vertical core segment containing high-angle fractures (10cm diameter, 20cm length). The small cores in the long core holders are obtained by drilling along the bedding direction of the full-diameter cores and then piecing them together (small core diameter 2.5cm, 5cm length, combined with a 50cm long core). This combination can better reflect the horizontal migration mechanism of fluid reservoirs. Different rows and columns of long core holders are selected at different stratigraphic levels to achieve multi-layered simulation.

[0028] 2. This invention uses CH4 gas containing gas tracers, saturated in different core holders, combined with GC / MS gas chromatography-mass spectrometry / chromatograph, to evaluate the availability of reservoir reserves due to water intrusion during gas reservoir development.

[0029] 3. This invention evaluates the intrusion intensity of edge and bottom water during gas reservoir development by adding chemical tracers to different water-bearing containers and using online ion chromatography.

[0030] 4. This invention achieves the saturation of the original fluid in each clamp of the experimental system through the method of "individual saturation and overall assembly".

[0031] 5. This invention uses pressure sensors in each core holder to observe and simulate pressure drop during the entire gas reservoir development process.

[0032] 6. The experimental apparatus in this invention can be adjusted according to the reservoir characteristics and water body characteristics of the actual gas reservoir to realize the simulation and dynamic evaluation of the development process of multi-layered water-bearing gas reservoirs. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the present invention;

[0034] Figure 2 This is a schematic diagram of the original fluid saturation unit structure in the invention;

[0035] Figure reference numerals: 1-Side water injection pump, 2-Side water intermediate container, 3-Bottom water injection pump, 4-Bottom water intermediate container, 5-Top layer right-side long core holder, 6-Top layer left-side long core holder, 7-Middle layer right-side long core holder, 8-Middle layer left-side long core holder, 9-Bottom layer right-side long core holder, 10-Bottom layer left-side long core holder, 11-Top full-diameter core holder, 12-Middle full-diameter core holder, 13-Bottom full-diameter core holder, 14-Pressure monitor 15-Pipeline valve, 16-Containing pressure pump, 17-Back pressure pump, 18-Gas intermediate container, 19-Back pressure valve, 20-Gas-water separator metering device, 21-GC / MS gas chromatograph / mass spectrometer, 22-Online ion chromatograph, 23-Four-way valve, 24-Three-way valve, 25-Vacuum pump, 26-CH4 intermediate container, 27-Tracer intermediate container, 28-Gas mixing sampler, 29-Formation water intermediate container, 30-High-pressure injection pump, 31-Reservoir core, 32-Rubber sleeve. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0038] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0039] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0040] Example 1

[0041] like Figures 1 to 2 As shown, this embodiment provides an experimental apparatus for simulating the development of a strongly heterogeneous multi-layered water-bearing gas reservoir, including a side water simulation unit, a bottom water simulation unit, a multi-layered reservoir simulation unit, a vertically fractured reservoir simulation unit, a back pressure control unit, a gas-water monitoring unit, and an original fluid saturation unit.

[0042] The multi-layer reservoir simulation unit is a horizontally arranged multi-layer parallel structure. One side of the multi-layer parallel structure is connected to the edge water simulation unit, and the other side is connected to the back pressure control unit. The back pressure control unit is connected to the gas-water monitoring unit through the gas-water separation meter 20. Each layer of the parallel structure includes two long core holders arranged in series and horizontally.

[0043] The vertical fractured reservoir simulation unit includes multiple full-diameter core holders connected in series vertically. The number of full-diameter core holders is the same as the number of layers in the multi-layer parallel structure. Except for the bottom full-diameter core holder, all full-diameter core holders are connected sequentially between adjacent layers in the multi-layer parallel structure. The bottom full-diameter core holder is connected to the bottom water simulation unit.

[0044] The original fluid saturation unit is compatible with all saturated long core holders and full-diameter core holders.

[0045] The multi-layer reservoir simulation unit has a three-layer parallel structure, with each layer consisting of two long core holders connected in series and horizontally arranged. The vertical fractured reservoir simulation unit includes three full-diameter core holders connected in series vertically.

[0046] The top full-diameter core holder is located between the first layer of long core holders and the second layer of long core holders. One end of the top full-diameter core holder is connected to the pipeline between the two long core holders in the first layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the second layer through a pipeline.

[0047] The central full-diameter core holder is located between the second-layer long core holder and the third-layer long core holder. One end of the central full-diameter core holder is connected to the pipeline between the two long core holders in the second layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the third layer through a pipeline.

[0048] One end of the bottom full-diameter core holder is connected to the pipeline between the two long core holders in the third layer, and the other end is connected to the bottom water simulation unit.

[0049] The original fluid saturation unit includes a formation CH4 intermediate container 26, a tracer intermediate container 27, a gas mixing and sample preparation device 28, a formation water intermediate container 29, a vacuum pump 25, and a high-pressure injection pump 30. The CH4 intermediate container 26, the tracer intermediate container 27, the gas mixing and sample preparation device 28, and the formation water intermediate container 29 are connected in parallel. The high-pressure injection pump 30 is connected to the parallel connection pipeline, and after the parallel connection, it is connected to the long core holder or the full-diameter core holder through the pipeline. The vacuum pump 25 is connected to the long core holder or the full-diameter core holder through the pipeline.

[0050] The edge water simulation unit includes an edge water injection pump 1 and an edge water intermediate container 2 for storing high-pressure saturated sodium bromide solution. The edge water injection pump 1 is connected to one side of the multi-layer parallel structure through the edge water intermediate container 2. The bottom water simulation unit includes a bottom water injection pump 3 and a bottom water intermediate container 4 for storing high-pressure saturated potassium chloride solution. The bottom water injection pump 3 is connected to the bottom full-diameter core holder 13 through the bottom water intermediate container 4.

[0051] The core in the long core holder consists of 10 small cores with a diameter of 2.5 cm and a length of 5 cm. The combined long core after the small cores are connected in series has a length of 0.5 m. The combined long core is placed in the rubber tube 32. There is an annular space between the outside of the rubber tube 32 and the long core holder. Hydraulic oil is injected into the annular space.

[0052] The core in the full-diameter core holder consists of two longitudinally fractured reservoir cores obtained directly after drilling. The longitudinally fractured reservoir cores are 10cm in diameter and 25cm in length. The cores are connected in series and are 0.5m long. The connected cores are placed in rubber sleeve A. There is an annular space between the outside of rubber sleeve A and the full-diameter core holder. Hydraulic oil is injected into the annular space.

[0053] The long core holder or full-diameter core holder is equipped with a pipeline valve 15 and a pressure monitor 14 at both the outlet and inlet ends. The long core holder or full-diameter core holder is also connected to a confining pressure pump 16 for controlling the confining pressure of the core.

[0054] The back pressure control unit includes a back pressure valve 19, a gas intermediate container 18, and a back pressure pump 17. The back pressure pump 17 is connected to the gas intermediate container 18, and the gas intermediate container 18 is connected to the back pressure valve 19. The back pressure valve 19 is located on the pipeline between the other side of the multi-layer parallel structure and the gas-water separator meter 20.

[0055] The gas-water monitoring unit includes a GC / MS gas chromatography-mass spectrometer 21 and an online ion chromatograph 22, which are connected in parallel to the gas-water separation meter 20.

[0056] The experimental method for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs includes the following steps:

[0057] Step 1, Simulation of gas reservoir development: The original fluid saturation of the long core holder and the full-diameter core holder is completed through the original fluid saturation unit, so that the fluid in each holder contains different gas tracer components with a concentration of 20%.

[0058] Step 2: Connect the saturated long core holder and the full-diameter core holder to the experimental pipeline, open the outlet and inlet valves of all holders, control the pressure drop rate at the total outlet, release the saturated fluid inside the core at the set pressure drop rate, and simultaneously input the gas and liquid obtained from the gas-liquid separator into the gas chromatograph / mass spectrometer and the online ion chromatograph, respectively, and record the various parameter data online in real time until the pressure at the outlet reaches the waste pressure and stop the experiment.

[0059] Step 3: By analyzing the changes in pressure data from the pressure sensors at the inlet and outlet of the gripper, combined with the changes in the concentration and composition of the gas tracer in the gas chromatograph and the changes in the concentration of liquid ions in the online ion chromatograph, we can assess the degree of utilization of the original gas in different grippers during the development of highly heterogeneous multilayer water-bearing fractured gas reservoirs, as well as the mechanism of edge and bottom water intrusion in the fractured reservoir.

[0060] Example 2

[0061] An experimental apparatus for simulating the development of a strongly heterogeneous multi-layered water-bearing gas reservoir includes a side water simulation unit, a bottom water simulation unit, a multi-layered reservoir simulation unit, a vertically fractured reservoir simulation unit, a backpressure control unit, a gas-water monitoring unit, and a raw fluid saturation unit.

[0062] The edge water simulation unit includes an edge water injection pump 1 and an edge water intermediate container 2. The edge water intermediate container stores a high-pressure saturated sodium bromide solution, which, when combined with an online ion chromatograph, can be used as an edge water tracer.

[0063] The bottom water simulation unit includes a bottom water injection pump 3 and a bottom water intermediate container 4. The bottom water intermediate container stores a high-pressure saturated potassium chloride solution, which, when combined with an online ion chromatograph, can be used as a bottom water tracer.

[0064] The multi-layer reservoir simulation system consists of 6 long core holders and 3 full-diameter core holders, with pipelines between the core holders connected by a three-way valve 24 and a four-way valve 23.

[0065] The long core holder is placed horizontally. The core in the long core holder consists of 10 small cores (2.5 cm in diameter and 5 cm in length). The combined long core after the small cores are connected in series has a length of 0.5 m. The small cores are drilled along the horizontal bedding direction of the full-diameter cores drilled downhole. The combined long core is placed in a rubber tube. There is an annular space between the outside of the rubber tube and the holder. Hydraulic oil is injected into the annular space.

[0066] The multi-layer reservoir simulation unit composed of long core holders includes a top right long core holder 5, a top left long core holder 6, a middle right long core holder 7, a middle left long core holder 8, a bottom right long core holder 9, and a bottom left long core holder 10, used to simulate different development reservoir systems.

[0067] The long core holder has pipeline valves 15 and pressure monitors 14 at its outlet and inlet ends. The long core holder is also connected to a confining pressure pump 16, which is used to control the confining pressure of the core and to seal the rubber sleeve and the core.

[0068] The long core holder has an external self-heating temperature control system, which enables rapid and efficient temperature control. The long core holder can withstand a maximum pressure of 150 MPa and a maximum temperature of 200°C.

[0069] The full-diameter clamp is placed vertically. The core in the clamp consists of two longitudinally fractured reservoir cores (10cm in diameter and 25cm in length) obtained directly after drilling. The cores are connected in series and are 0.5m long. The combined long core is placed in a rubber tube. There is an annular space between the outside of the rubber tube and the clamp, and hydraulic oil is injected into the annular space.

[0070] The longitudinal fractured reservoir simulation unit composed of full-diameter core holders includes a top full-diameter core holder 11, a middle full-diameter core holder 12, and a bottom full-diameter core holder 13, which are used to simulate the longitudinal migration law of fluids in high-angle fractured reservoirs between different strata.

[0071] The full-diameter core holder has pipeline valves and pressure monitoring and recording sensors at its outlet and inlet ends. The full-diameter core holder is also connected to a confining pressure pump to control the confining pressure of the core, thereby sealing the rubber sleeve and the core.

[0072] The full-diameter core holder has an external self-heating temperature control system, enabling rapid and efficient temperature control. The full-diameter core holder can withstand a maximum pressure of 150 MPa and a maximum temperature of 200°C.

[0073] The back pressure control unit includes a back pressure valve 19, a high-pressure gas intermediate container 18, and a back pressure pump 17; the gas-water monitoring unit includes a GC / MS gas chromatograph / mass spectrometer 21 and an online ion chromatograph 22. Through pressure reduction simulation development process, the unit monitors the produced gas and water ions in real time to evaluate the degree of reserve utilization of different layers under the action of edge and bottom water, and analyzes the intensity of edge and bottom water action.

[0074] The long core holders on the right and left sides of the top fracture are connected to the full-diameter core holder containing the fracture at the top via three-way valves, and the long core holders on the right and left sides of the top fracture are located on either side of the full-diameter core holder containing the fracture at the top; the long core holders on the right and left sides of the middle layer are connected to the full-diameter core holder (including the fracture) at the top and the full-diameter core holder (including the fracture) in the middle via four-way valves, and... The right-side and left-side long core holders of the middle layer are located on either side of the top and middle full-diameter core holders. The right-side and left-side long core holders of the bottom layer are connected to the middle and bottom full-diameter core holders (including fractures) via four-way valves, and the right-side and left-side long core holders of the bottom layer are located on either side of the middle and bottom full-diameter core holders. The bottom full-diameter core holder is connected to the bottom water intermediate container and the bottom water injection pump. The right-side long core holders of the top, middle, and bottom layers are connected to the edge water intermediate container and the edge water injection pump via four-way valves. The top-layer left-side long core holder, the middle-layer left-side long core holder, and the bottom-layer left-side long core holder are connected to the outlet backpressure valve via a four-way valve. A high-pressure gas cylinder and a backpressure pump are connected to the backpressure valve to control the pressure drop rate at the outlet during the development of a depleted gas reservoir. A gas-liquid flow separator / meter is connected to the other side of the backpressure valve. After gas and water separation and metering, the gas is input into a gas chromatograph / mass spectrometer, while the liquid is input into an online ion chromatograph.

[0075] The original fluid saturation unit comprises a formation CH4 high-pressure intermediate container 26, a gas tracer cylinder 27, a high-temperature and high-pressure gas mixing and sampling device 28, a formation water intermediate container 29, a full-diameter core holder or a long core holder, and a vacuum pump 25.

[0076] The initial fluid saturation of the entire system was achieved using a "separate saturation, overall assembly" method. This involved saturating the long core holders and the full-diameter core holders separately before assembling them. First, high-purity CH4 and a gas tracer were injected into the gas mixing sampler 28 using a high-pressure injection pump 30 and thoroughly mixed (gas tracer concentration of 20%). Simultaneously, a vacuum pump was used to evacuate either the long core holder or the full-diameter core holder. Then, formation water was injected into either the long core holder or the full-diameter core holder using a high-pressure injection pump. After saturation, the mixed CH4 / tracer gas was injected into the core using a high-pressure injection pump until no more water was emitted from the holder outlet. GC / MS gas chromatography / mass spectrometry was used to record the gas composition characteristics in each core holder. Once the initial fluid saturation was complete, the different long core holders and the full-diameter core holders were assembled together. The gas tracers include sulfur hexafluoride, octafluorocyclobutane, argon, nitrogen, oxygen, helium, carbon monoxide, nitric oxide, and carbon dioxide, a total of nine types, which are mixed with CH4 and injected into nine different long core holders or full-diameter core holders.

[0077] The method for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs using the above-mentioned experimental setup includes the following steps:

[0078] Rock sample selection. Two types of core samples were selected. The first type was a full-diameter core containing fractures, stored in a full-diameter holder. This full-diameter core was a downhole reservoir core with a diameter of 10 cm and a length of 25 cm. The full-diameter core was selected from the vertical section of the reservoir cored during drilling, containing naturally fractured rock samples, to better reflect the characteristics of longitudinal fracture development in the reservoir. The second type of core sample was a small core, stored in a long-diameter holder. This small core was a downhole core with a diameter of 2.5 cm and a length of 5 cm. The small core was drilled in the horizontal bedding direction from the full-diameter downhole core, which can reflect the seepage characteristics of the sedimentary reservoir.

[0079] Assembly of the experimental system. Selected small cores and full-diameter cores were loaded into the long core holder and full-diameter core holder, respectively. The long core holder contained 10 small cores, each 5cm long and 2.5cm in diameter. The full-diameter core holder contained 2 full-diameter cores, each 25cm long and 10cm in diameter with well-developed fractures. The combined long cores and full-diameter cores were then inserted into rubber sleeves and placed into the holders. All long core holders were placed horizontally. Pressure monitoring and recording sensors were installed at the inlet and outlet of the holders. Each long core holder was also connected to a confining pressure pump, which injected hydraulic oil into the annular space between the rubber sleeve and the holder, maintaining the confining pressure 5–7 MPa higher than the internal pressure of the core. All full-diameter clamps are placed vertically, and pressure monitoring and recording sensors are installed at the inlet and outlet of the clamps. The full-diameter clamps are also connected to a confining pressure pump, which injects hydraulic oil into the annular space between the rubber sleeve and the clamp to maintain the confining pressure 5-7 MPa higher than the core pressure.

[0080] Gas injection. The initial fluid saturation of the entire system was achieved using a "separate saturation, overall assembly" method. This involved saturating each long core holder and the full-diameter core holder separately before assembling them. First, high-purity CH4 and a gas tracer were injected into a gas mixing and sampler using a high-pressure injection pump and thoroughly mixed (the gas tracer concentration was set to 20%). Simultaneously, a vacuum pump was used to evacuate either the long core holder or the full-diameter core holder for 24 hours. Then, high-pressure formation water was injected into the reservoir core 31 within the holders using a high-pressure injection pump to saturate the formation water under reservoir temperature and pressure conditions. Preferably, the experimental setup for this study was a pressure of 50 MPa and a temperature of 120°C. After saturation, the mixed CH4 / tracer gas mixture is injected into the core using a high-pressure injection pump until no more water comes out of the holder outlet. At the same time, the gas composition characteristics in the core holder are recorded using GC / MS gas chromatography-mass spectrometry / chromatograph. When the concentration of tracer gas at the outlet reaches 20%, the high temperature and high pressure saturation of the gas is considered complete, and the outlet and inlet valves of the holder are closed.

[0081] The gaseous tracers include sulfur hexafluoride, octafluorocyclobutane, argon, nitrogen, oxygen, helium, carbon monoxide, nitric oxide, and carbon dioxide, a total of nine types, which are mixed with CH4 and injected into six long core holders and three full-diameter core holders.

[0082] Assembly of the experimental system: After the original fluid is saturated, close the valves at the outlet and inlet of the clamp, and assemble the entire system through pipelines, three-way valves, and four-way valves. The long core holders on the right and left sides of the top fracture are connected to the full-diameter core holder at the top via three-way valves, and are located on either side of the full-diameter core holder at the top. The long core holders on the right and left sides of the top fracture are connected to the full-diameter core holder at the top via four-way valves, and are located on either side of the full-diameter core holder at the top and the full-diameter core holder at the middle. The long core holders on the right and left sides of the middle fracture are connected to the full-diameter core holder at the top and the full-diameter core holder at the middle via four-way valves, and are located on either side of the full-diameter core holder at the top and the full-diameter core holder at the middle. The long core holders on the right and left sides of the bottom fracture are connected to the full-diameter core holder at the middle and the full-diameter core holder at the bottom via four-way valves, and are located on either side of the full-diameter core holder at the middle and the full-diameter core holder at the bottom. The bottom full-diameter core holder is connected to the bottom water intermediate container and the bottom water injection pump. The bottom water intermediate container stores a saturated potassium chloride solution as a tracer for the bottom water solution.

[0083] The top-right long core holder, the middle-right long core holder, and the bottom-right long core holder are connected to the edge water intermediate container and the edge water injection pump via four-way valves. The edge water intermediate container stores a saturated sodium bromide solution as a tracer for the edge water solution. The top-left long core holder, the middle-left long core holder, and the bottom-left long core holder are connected to the outlet backpressure valve via four-way valves. A high-pressure gas cylinder and a backpressure pump are connected to the backpressure valve to control the pressure drop rate at the outlet during the development of a depleted gas reservoir. A gas-water flow separator / meter is connected to the other side of the backpressure valve. After gas and water separation and metering, the gas is input into a gas chromatograph / mass spectrometer, while the liquid is input into an online ion chromatograph. It should be noted that this patent allows for the addition or reduction of the number of long core holders and full-diameter core holders according to the actual reservoir requirements, but the combination method remains the same.

[0084] Simulation of gas reservoir development: The simulation method for the development of highly heterogeneous multi-layered water-bearing gas reservoirs uses the simulation device for highly heterogeneous multi-layered water-bearing gas reservoirs as described above. The method includes: selecting a suitable number and size of small cores and full-diameter cores; placing the assembled cores into rubber tubes and inserting them into corresponding holders; using a confining pressure pump to inject hydraulic oil into the space between the rubber tubes and holders; and adjusting the confining pressure pump to maintain the experimental confining pressure 5-7 MPa higher than the internal pressure of the cores; and using the original fluid saturation unit, employing the "individual saturation, overall assembly" method, to complete the original fluid saturation of 6 long core holders and 3 full-diameter holders under reservoir temperature of 120℃ and pressure of 50 MPa, so that the fluid in each holder contains different gas tracer components with a concentration of 20%. The entire system is assembled using pipelines, three-way valves, and four-way valves. The long core holders on the right and left sides of the top fracture are connected to the top full-diameter core holder via three-way valves, with these two holders located on either side of the top full-diameter core holder. The long core holders on the right and left sides of the middle layer are connected to the top and middle full-diameter core holders via four-way valves. The core holders are connected, with the right-side long core holder and the left-side long core holder located on either side of the top and middle full-diameter core holders. The right-side and left-side long core holders of the bottom layer are connected to the middle and bottom full-diameter core holders via four-way valves, with the right-side and left-side long core holders of the bottom layer located on either side of the middle and bottom full-diameter core holders. The bottom full-diameter core holder is connected to the bottom water intermediate container and the bottom water injection pump.

[0085] A bottom water intermediate container stores a saturated potassium chloride solution, which serves as a bottom water tracer. The solution pressure inside the bottom water intermediate container reaches 50 MPa, and the pressure in the bottom water intermediate container is maintained at 50 MPa during the experiment via a bottom water injection pump.

[0086] The long core holders on the right side of the top layer, the right side of the middle layer, and the right side of the bottom layer are connected to the intermediate container of the side water and the side water injection pump through a four-way valve.

[0087] A saturated sodium bromide solution is stored in the intermediate container of the edge water, serving as a tracer for the edge water solution. The solution pressure inside the intermediate container reaches 50 MPa, and this pressure is maintained at 50 MPa during the experiment via an edge water injection pump.

[0088] The long core holders on the left side of the top layer, the middle layer, and the bottom layer are connected to the outlet backpressure valve via four-way valves. A high-pressure gas cylinder and a backpressure pump are connected to the backpressure valve. A gas-water flow separator and meter are connected to the other side of the backpressure valve.

[0089] After connecting the entire system, open the outlet and inlet valves of all clamps. Control the pressure drop rate at the total outlet through the back pressure system to release the saturated fluid inside the core at a certain pressure drop rate. At the same time, input the gas and liquid obtained from the gas-liquid separation metering device into the gas chromatograph / mass spectrometer and the online ion chromatograph, respectively, and record various parameter data online in real time until the pressure at the outlet reaches the waste pressure and the experiment is stopped.

[0090] By analyzing the pressure data changes in the inlet and outlet pressure sensors of the gripper, combined with the changes in the concentration and composition of the gas tracer in the gas chromatograph and the changes in the concentration of liquid ions in the online ion chromatograph, we can evaluate the degree of mobilization of the original gas in different grippers during the development of highly heterogeneous multilayer water-bearing fractured gas reservoirs, as well as the mechanism of edge and bottom water intrusion in the fractured reservoir.

Claims

1. An experimental apparatus for simulating the development of highly heterogeneous multi-layered water-bearing gas reservoirs, characterized in that, It includes edge water simulation unit, bottom water simulation unit, multi-layer reservoir simulation unit, vertical fractured reservoir simulation unit, back pressure control unit, gas-water monitoring unit, and original fluid saturation unit; The multi-layer reservoir simulation unit is a horizontally arranged multi-layer parallel structure. One side of the multi-layer parallel structure is connected to the edge water simulation unit, and the other side is connected to the back pressure control unit. The back pressure control unit is connected to the gas-water monitoring unit through the gas-water separation meter (20). Each layer of the parallel structure includes two long core holders arranged in series and horizontally. The vertical fractured reservoir simulation unit includes multiple full-diameter core holders connected in series vertically. The number of full-diameter core holders is the same as the number of layers in the multi-layer parallel structure. Except for the bottom full-diameter core holder, all full-diameter core holders are connected sequentially between adjacent layers in the multi-layer parallel structure. The bottom full-diameter core holder is connected to the bottom water simulation unit. The original fluid saturation unit is compatible with all saturated long core holders and full-diameter core holders; The multi-layer reservoir simulation unit has a three-layer parallel structure, with each layer consisting of two long core holders connected in series and horizontally arranged. The vertical fractured reservoir simulation unit includes three full-diameter core holders connected in series vertically. The top full-diameter core holder is located between the first layer of long core holders and the second layer of long core holders. One end of the top full-diameter core holder is connected to the pipeline between the two long core holders in the first layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the second layer through a pipeline. The central full-diameter core holder is located between the second-layer long core holder and the third-layer long core holder. One end of the central full-diameter core holder is connected to the pipeline between the two long core holders in the second layer through a pipeline, and the other end is connected to the pipeline between the two long core holders in the third layer through a pipeline. One end of the bottom full-diameter core holder is connected to the pipeline between the two long core holders in the third layer via a pipeline, and the other end is connected to the bottom water simulation unit. The core in the long core holder consists of 10 small cores with a diameter of 2.5 cm and a length of 5 cm. The combined long core after the small cores are connected in series has a length of 0.5 m. The combined long core is placed in a rubber tube (32). There is an annular space between the outside of the rubber tube (32) and the long core holder. Hydraulic oil is injected into the annular space. The core in the full-diameter core holder consists of two longitudinally fractured reservoir cores obtained directly after drilling. The longitudinally fractured reservoir cores are 10cm in diameter and 25cm in length. The cores are connected in series and are 0.5m long. The connected cores are placed in rubber sleeve A. There is an annular space between the outside of rubber sleeve A and the full-diameter core holder. Hydraulic oil is injected into the annular space. The long core holder or full-diameter core holder is equipped with a pipeline valve (15) and a pressure monitor (14) at both the outlet and inlet ends. The long core holder or full-diameter core holder is also connected to a confining pressure pump (16) for controlling the confining pressure of the core.

2. The experimental apparatus for simulating the development of strongly heterogeneous multi-layered water-bearing gas reservoirs according to claim 1, characterized in that, The original fluid saturation unit includes a formation CH4 intermediate container (26), a tracer intermediate container (27), a gas mixing and sample preparation device (28), a formation water intermediate container (29), a vacuum pump (25), and a high-pressure injection pump (30). The CH4 intermediate container (26), the tracer intermediate container (27), the gas mixing and sample preparation device (28), and the formation water intermediate container (29) are connected in parallel. The high-pressure injection pump (30) is connected to the parallel connection pipeline, and after the parallel connection, it is connected to the long core holder or the full-diameter core holder through the pipeline. The vacuum pump (25) is connected to the long core holder or the full-diameter core holder through the pipeline.

3. The experimental apparatus for simulating the development of strongly heterogeneous multi-layered water-bearing gas reservoirs according to claim 1, characterized in that, The edge water simulation unit includes an edge water injection pump (1) and an edge water intermediate container (2) for storing high-pressure saturated sodium bromide solution. The edge water injection pump (1) is connected to one side of the multi-layer parallel structure through the edge water intermediate container (2). The bottom water simulation unit includes a bottom water injection pump (3) and a bottom water intermediate container (4) for storing high-pressure saturated potassium chloride solution. The bottom water injection pump (3) is connected to the bottom full-diameter core holder (13) through the bottom water intermediate container (4).

4. The experimental apparatus for simulating the development of strongly heterogeneous multi-layered water-bearing gas reservoirs according to claim 1, characterized in that, The back pressure control unit includes a back pressure valve (19), a gas intermediate container (18), and a back pressure pump (17). The back pressure pump (17) is connected to the gas intermediate container (18), and the gas intermediate container (18) is connected to the back pressure valve (19). The back pressure valve (19) is located on the pipeline between the other side of the multi-layer parallel structure and the gas-water separator meter (20).

5. The experimental apparatus for simulating the development of strongly heterogeneous multi-layered water-bearing gas reservoirs according to claim 1, characterized in that, The gas-water monitoring unit includes a GC / MS gas chromatography-mass spectrometer (21) and an online ion chromatograph (22). The GC / MS gas chromatography-mass spectrometer (21) and the online ion chromatograph (22) are connected in parallel and then connected to the gas-water separation meter (20).

6. An experimental method using the experimental apparatus for simulating the development of strongly heterogeneous multi-layered water-bearing gas reservoirs as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1, Simulation of gas reservoir development: The original fluid saturation of the long core holder and the full-diameter core holder is completed through the original fluid saturation unit, so that the fluid in each holder contains different gas tracer components with a concentration of 20%. Step 2: Connect the saturated long core holder and the full-diameter core holder to the experimental pipeline, open the outlet and inlet valves of all holders, control the pressure drop rate at the total outlet, release the saturated fluid inside the core at the set pressure drop rate, and simultaneously input the gas and liquid obtained from the gas-liquid separator into the gas chromatograph / mass spectrometer and the online ion chromatograph, respectively, and record the various parameter data online in real time until the pressure at the outlet reaches the waste pressure and stop the experiment. Step 3: By analyzing the changes in pressure data from the pressure sensors at the inlet and outlet of the gripper, combined with the changes in the concentration and composition of the gas tracer in the gas chromatograph and the changes in the concentration of liquid ions in the online ion chromatograph, we can assess the degree of utilization of the original gas in different grippers during the development of highly heterogeneous multilayer water-bearing fractured gas reservoirs, as well as the mechanism of edge and bottom water intrusion in the fractured reservoir.

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