Natural gas hydrate reservoir stimulation and yield increase experimental apparatus

Abstract

A natural gas hydrate reservoir stimulation and yield increase experimental apparatus, comprising a simulation reaction vessel (1), and a high-pressure sand filling system (2), a crack-forming loading system (3), an overlying-pressure loading system (4), a gas pressurization system (7), a fracturing system and a data collection system, which are respectively connected to the simulation reaction vessel (1), wherein during a simulation test process, a reservoir medium is arranged in the simulation reaction vessel (1); by means of the crack-forming loading system (3), cracks having various widths and / or shapes are simulated and generated in the simulation reaction vessel (1); by means of the high-pressure sand filling system (2), the reservoir medium is compacted; by means of the overlying-pressure loading system (4), seabed overlying pressure is simulated for the reservoir medium; by means of the gas pressurization system (7), gas is pressurized, and then enters the simulation reaction vessel (1); by means of the fracturing system, a fracturing fluid or proppant (23) is injected into the simulation reaction vessel (1); and by means of the data collection system, experimental data is collected.

Description

A natural gas hydrate reservoir transformation and production increase experimental device Technical field:

[0001] The invention relates to the technical field of natural gas hydrate exploitation, in particular to a natural gas hydrate reservoir transformation and production increase experimental device. Background technology:

[0002] Natural gas hydrates, commonly known as combustible ice, are cage-type ice crystals formed by small molecular gases such as light hydrocarbons and CO2 and water under low temperature and high pressure. They are widely distributed in permafrost layers and the pores of most unconsolidated submarine strata. my country has rich reserves of natural gas hydrates and related research is progressing rapidly. In June 2007, the China Geological Survey discovered marine natural gas hydrates for the first time in the Shenhu area of ​​the South China Sea. In November 2008, the China Geological Survey discovered terrestrial natural gas hydrates in the permafrost area of ​​the Qilian Mountains in Qinghai. After continuous research on natural gas hydrates on land and in the sea, China conducted its first trial production of natural gas hydrates in the Muli area of ​​the Qilian Mountains in September 2011. In 2017, China carried out its second trial production of natural gas hydrates in the Shenhu area of ​​the South China Sea and successfully obtained natural gas from a 1,266-meter-deep muddy siltstone natural gas hydrate reservoir on the seabed. It has been producing gas stably for 60 days, with a cumulative gas production of 309,000 m 3 In 2020, China took the lead in adopting horizontal well drilling production technology and carried out the second round of natural gas hydrate test in the Shenhu area of ​​the South China Sea. After one month of test production, the total gas production was 861,200 m 3 , with a daily output of 28,700 m 3 , which is 5.57 times the daily output of the first vertical well production experiment. The experiment shows that muddy siltstone oil and gas has good development potential. However, the average daily output is still below the critical value of commercial production. Wu Nengyou et al. believe that the gas production required for commercial production of marine natural gas hydrates is about 5.0*10 5 m, the gas production of the second trial production in the South China Sea is still 2-3 orders of magnitude lower than that.

[0003] Research shows that the factors leading to low productivity are mainly reflected in the following three aspects:

[0004] First, the muddy silt hydrate reservoir has extremely low permeability, resulting in extremely poor heat and mass transfer efficiency in the reservoir, making the gas produced by the in-situ decomposition of the hydrate difficult to release and transport;

[0005] Second, during the depressurization process, the endothermic effect associated with hydrate decomposition often leads to the formation of secondary hydrate ice, further blocking the gas seepage channel;

[0006] Third, with the decomposition of hydrates, the continuous decrease in reservoir strength has greatly increased the risk of inducing submarine disasters such as submarine landslides, submarine collapses and methane leaks.

[0007] A large number of scientific studies and engineering practices have shown that reservoir transformation is an important way to improve the production performance of unconventional low-permeability reservoirs.

[0008] Compared with the passive optimization and adaptation of native hydrate reservoirs through production well design, decomposition stimulation enhancement, and development strategy optimization, reservoir transformation is an active artificial transformation of hydrate reservoirs to improve the porosity (porosity, permeability) and mechanical properties of the native reservoir, providing good conditions for subsequent pressure transmission and gas-water seepage production processes, thereby achieving increased production and efficiency.

[0009] However, in the prior art, there is no device that can realize hydrate generation and exploitation and can achieve different forms of reservoir transformation in the process.

[0010] Summary of the invention:

[0011] The purpose of the present invention is to solve the problems existing in the prior art and provide a natural gas hydrate reservoir transformation and production increase experimental device.

[0012] In order to solve the problems existing in the prior art, the present invention adopts the following technical solutions:

[0013] A natural gas hydrate reservoir transformation and production increase experimental device includes a simulation reactor, and a high-pressure sand filling system, a fracture loading system, an overburden loading system, a gas pressurization system, a fracturing system, and a data acquisition system respectively connected to the simulation reactor;

[0014] During the simulation test, a reservoir medium is provided in the simulation reactor, and the fracture creation and loading system is used to simulate the generation of fractures of various widths and / or shapes in the simulation reactor. The reservoir medium is compacted by the high-pressure sand filling system, and the seabed overburden pressure is simulated on the reservoir medium by the overburden pressure loading system. The gas is pressurized by the gas boosting system and then enters the simulation reactor. The fracturing fluid or proppant is injected into the simulation reactor through the fracturing system, and the experimental data is collected and obtained by the data acquisition system.

[0015] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, at least one horizontal production well and at least one vertical production well are provided in the simulation reactor;

[0016] The data acquisition system may be arranged in the horizontal production well and the vertical production well to acquire pressure values ​​and / or temperature values ​​in the horizontal production well and the vertical production well.

[0017] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the simulation reactor is equipped with an end cover, a sediment loading and unloading tool and a lifting mechanism;

[0018] The end cover seals the simulated reactor, and the sediment is loaded into and unloaded from the simulated reactor through the sediment loading and unloading mechanism. The lifting mechanism is used to adjust the height of the simulated reactor.

[0019] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, a heat-insulating jacket is provided on the outside of the simulation reactor, and the simulation reactor is placed in a low-temperature water bath.

[0020] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the gas pressurization system includes an air compressor, a booster pump, a gas storage tank and a pressure regulating valve connected in sequence, and the pressure regulating valve is connected to the simulation reactor.

[0021] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the fracturing system includes a fracturing pump connected in sequence, an intermediate container and a stirring container respectively connected to the fracturing pump, and the pressure pump is connected to the simulation reactor through the intermediate container or the stirring container.

[0022] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the natural gas hydrate reservoir transformation and production increase experimental device also includes a control system, which includes a PID system for controlling the production pressure.

[0023] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the data acquisition system includes a resistance measurement system, a temperature and pressure testing system, a gas-liquid flow measurement and sand production measurement, a data acquisition system, a computer processing system and a large centralized display screen.

[0024] As an improvement to the technical solution of the natural gas hydrate reservoir transformation and production increase experimental device of the present invention, the seam-making loading system includes a seam-making hydraulic cylinder, a displacement lead-out rod and a seam-making blade. The hydraulic device controls the downward displacement of the blade to create a seam in the reservoir. By replacing different tools and changing the tool displacement, various seam shapes and widths can be simulated.

[0025] Beneficial effects of the present invention:

[0026] The present invention provides a method for simulating reservoir pressure and temperature conditions based on the displacement mechanism and similarity principle, and with the help of the latest achievements of modern science and technology, such as computer technology and advanced sensor technology, which are mainly used for automatic measurement simulation experiments under laboratory conditions, it is possible to carry out hydrate reservoir fracturing experiments, seepage capacity tests before and after hydrate reservoir fracturing, hydrate formation and decomposition simulation and other development experiments, study the invasion of fracturing fluid and proppant, crack distribution and other experiments, and simulate various shapes of cracks and cracks of different widths to evaluate the reservoir transformation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG1 is a schematic structural diagram of the present invention.

[0028] Explanation of the accompanying symbols: 1-simulation test kettle; 2-high-pressure sand filling system; 3-fracture loading system; 4-overpressure loading system; 5-low-temperature water bath; 6-insulation jacket; 7-gas boosting system; 8-fracturing pump; 9-intermediate container; 10-mixing container; 11-air compressor; 12-boosting pump; 13-gas storage tank; 14-pressure regulating valve; 15-temperature field; 16-valve body; 17-gas flow meter; 18-gas-liquid separator; 19-electronic balance; 20-vertical production well; 21-horizontal production well; 22-fracture blade; 23-proppant. Specific implementation method:

[0029] In order to make the purpose of the invention, technical solutions and beneficial effects of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] A natural gas hydrate reservoir transformation and production increase experimental device includes a simulation test kettle 1, and a high-pressure sand filling system 2, a fracture loading system 3, an overburden loading system 4, a gas pressurization system 7, a fracturing system, and a data acquisition system respectively connected to the simulation test kettle 1;

[0031] During the simulation test, a reservoir medium is provided in the simulation test kettle 1, and various seam widths and / or seam shapes are simulated in the simulation test kettle 1 through the seam creation loading system 3. The reservoir medium is compacted by the high-pressure sand filling system 2, and the seabed overburden is simulated on the reservoir medium through the overburden loading system 4. The gas is pressurized by the gas boosting system 7 and then enters the simulation test kettle 1. The fracturing fluid or proppant 23 is injected into the simulation test kettle 1 through the fracturing system, and the experimental data is collected and obtained through the data acquisition system.

[0032] In detail, through literature research and preliminary experimental verification, it is shown that the method of fracturing the reservoir and injecting fracturing fluid during the mining process can, under certain conditions, increase the permeability of the reservoir and thus increase the efficiency of mining and achieve the effect of increasing production.

[0033] In the present invention, a reservoir medium is provided in the simulation test kettle 1, and different functional systems are coordinated to simulate different experiments to carry out a natural gas hydrate reservoir transformation and production increase experiment.

[0034] In more detail, in the present invention, a reservoir medium is provided in the simulation test kettle 1, and various seam widths and / or seam shapes can be simulated in the simulation test kettle 1 through the seam creation loading system 3, the reservoir medium is compacted by the high-pressure sand filling system 2, the seabed overburden is simulated on the reservoir medium by the overburden loading system 4, the gas is pressurized by the gas boosting system 7 and then enters the simulation test kettle 1, the fracturing fluid or proppant 23 is injected into the simulation test kettle 1 through the fracturing system, and the experimental data is acquired through the data acquisition system.

[0035] That is, in the present invention, since the natural gas hydrate reservoir transformation and production increase experimental device of the present invention includes a simulation test kettle 1, and a high-pressure sand filling system 2, a fracture loading system 3, a back pressure loading system 4, a gas pressurization system 7, a fracturing system and a data acquisition system respectively connected to the simulation test kettle 1, automatic measurement simulation experiments can be carried out in the laboratory as needed, and hydrate reservoir fracturing experiments, seepage capacity tests before and after hydrate reservoir fracturing, hydrate formation, decomposition simulation and other development tests can be carried out, the invasion of fracturing fluid and proppant 23, crack distribution and other experiments can be studied, and various shapes of cracks and cracks of different widths can be simulated to evaluate the reservoir transformation effect.

[0036] Example 1

[0037] During hydrate formation and decomposition, the reservoir medium is placed in the test vessel 1. High-pressure sand filling system 2 compacts the reservoir medium, and then fractures of various widths and / or shapes are simulated in the test vessel 1 using fracture creation and loading system 3. During the experiment, the seawater pressure exerted on the reservoir medium is simulated using overpressure loading system 4. Combined with gas boosting, the pressurized gas is then pressurized before entering the test vessel 1. This allows for development experiments such as hydrate formation and decomposition simulations to be conducted, as well as experiments to simulate fractures of various shapes and widths to evaluate the effectiveness of reservoir stimulation.

[0038] Example 2

[0039] Based on Example 1, when it is necessary to conduct a hydrate reservoir fracturing experiment, or to study the intrusion of fracturing fluid and proppant 23, the distribution of fractures, etc., or to test the permeability of the hydrate reservoir before and after fracturing, the fracturing system can be used to inject the fracturing fluid or proppant 23 into the simulated test kettle 1 through the fracturing system to achieve the effect of fracturing the reservoir medium, thereby increasing permeability and improving mining efficiency. At the same time, it is also possible to simulate fractures of various shapes and widths to evaluate the reservoir transformation effect.

[0040] The simulation test kettle 1 in the present invention is used to prepare natural gas hydrate samples, realistically simulate the natural gas hydrate accumulation environment (temperature, pressure, sediment, gas-water-hydrate saturation) in the sedimentary layer at a depth of 3,000 meters in the South China Sea, and, under the joint action of other systems and theirs, simulate the natural hydrate reservoir environment under different conditions to conduct different experiments.

[0041] Preferably, the simulation test kettle 1 may be a simulation test kettle 1 with a volume of 7.5 L, a working pressure of 40 MPa, and a working temperature of -20°C to 80°C.

[0042] In the present invention, other systems include not only the high-pressure sand filling system 2, the seam loading system 3, the overpressure loading system 4, the gas boosting system 7, the fracturing system and the data acquisition system, but also other auxiliary systems. Other auxiliary systems include combustible gas detection devices, cold storage explosion-proof ventilation devices, test equipment installation and operation platforms, and instrument electrical control cabinets, etc., to ensure the integrity of the present invention and improve the functionality of the present invention.

[0043] In some embodiments of the present invention, the seam-making loading system 3 is arranged above the simulation test kettle 1. The seam-making loading system 3 includes a seam-making hydraulic cylinder, a displacement lead-out rod and a seam-making blade 22. The hydraulic device controls the downward displacement of the blade to create a seam in the reservoir. By replacing different tools and changing the tool displacement, various seam shapes and different seam widths can be simulated.

[0044] Under the joint action of the slit-making loading system 3 and the data acquisition system, data such as slit-making displacement can be obtained in real time, so that the experimenter can obtain real-time experimental data.

[0045] In some embodiments of the present invention, the overburden loading system 4 is used to simulate seabed overburden on the reservoir medium, which mainly includes a plunger pump, an overburden piston and an overburden piston pressure plate. The plunger pump is used to displace the overburden piston, causing the overburden piston pressure plate to displace downward to apply overburden pressure to the reservoir, thereby simulating the seawater pressure on the reservoir.

[0046] Under the joint action of the overburden loading system 4 and the data acquisition system, data such as overburden displacement and overburden pressure can be obtained in real time, so that the experimenters can obtain real-time experimental data.

[0047] In some embodiments of the present invention, the data acquisition system includes a resistance measurement system, a temperature and pressure testing system, a gas-liquid flow measurement and sand production measurement system, a computer processing system and a large centralized display screen; the data acquisition system is used to collect, store, process and display data on the temperature, pressure, gas-water-hydrate three-phase saturation distribution, gas-liquid injection flow, gas production, water production and sand production of the test device.

[0048] Furthermore, the gas-liquid flow measurement and sand production measurement system includes a control valve 16 , a gas-liquid separator 18 and an electronic balance 19 which are sequentially connected to the simulation test kettle 1 , wherein the gas-liquid separator 18 is also connected to a gas flow meter 17 .

[0049] In some embodiments of the present invention, at least one horizontal production well 21 and at least one vertical production well 20 are provided in the simulation test kettle 1; a data acquisition system can be provided in the horizontal production well 21 and the vertical production well 20 to collect pressure values ​​and / or temperature values ​​in the horizontal production well 21 and the vertical production well 20.

[0050] In some embodiments of the present invention, the high-pressure sand filling system 2 can not only compact the reservoir medium, but also restore the fractures after completing an experiment to prepare for the next experiment. Alternatively, during the current experiment, the high-pressure sand filling system 2 can be used to adjust the depth, width, or shape of the fractures.

[0051] As a specific embodiment of the present invention, a horizontal production well 21 and a vertical production well 20 are installed within a test vessel 1. Temperature measurement points are located in three layers, with 21 sensors per layer, for a total of 63 temperature sensors, with a measurement accuracy of ±0.1°C. The pressure sensor has a range of 40 MPa and an accuracy of ±0.1%.

[0052] In some embodiments of the present invention, the simulation test kettle 1 is equipped with an end cover, a sediment loading and unloading tool and a lifting mechanism; the end cover seals the simulation test kettle 1, and the sediment is loaded and unloaded into and out of the simulation test kettle 1 through the sediment loading and unloading tool, and the lifting mechanism is used to adjust the height of the simulation test kettle 1.

[0053] Furthermore, a heat-insulating jacket 6 is provided on the outside of the simulation test kettle 1 , and the simulation test kettle 1 is placed in a low-temperature water bath 5 , thereby ensuring the temperature environment of the simulation test kettle 1 during testing and forming a temperature field 15 of the simulation test kettle 1 during testing.

[0054] Furthermore, the inlet and outlet of the simulation test kettle 1 and the inlet and outlet of the piston container are designed with quick connectors, which makes loading and unloading quick and convenient.

[0055] In some embodiments of the present invention, the high-pressure sand filling system 2 is arranged above the simulation test kettle 1, and mainly includes a sand adding interface and a sand storage chamber. After the seam is created, the seam filling sand can be quickly filled with proppant 23.

[0056] In some embodiments of the present invention, the gas pressurization system 7 includes an air compressor 11, a booster pump 12, a gas storage tank 13, and a pressure regulating valve 14 connected in sequence. The pressure regulating valve 14 is connected to the simulation test kettle 1. The gas pressurization system 7 is used to pressurize the gas when quantitatively injecting gas into the simulation test kettle 1 during hydrate formation.

[0057] In some embodiments of the present invention, the fracturing system includes a fracturing pump 8, an intermediate container 9 and a stirring container 10 connected in sequence to the fracturing pump 8, and the pressure pump is connected to the simulation test kettle 1 through the intermediate container 9 or the stirring container 10. In the present invention, the fracturing pump 8 can inject fracturing fluid into the reservoir to achieve a fracturing effect, thereby increasing permeability and improving production efficiency.

[0058] Under the action of the fracturing system, the fracturing effects under different formations and different fracturing methods can be simulated, the expansion of fracturing cracks can be predicted, the performance and flow patterns of the fracturing fluid can be analyzed, and an important basis for fracturing design and optimization can be provided. Through simulated operations, operators can have a deeper understanding of the principles and processes of fracturing operations, master operating skills and safety regulations, and thus improve operational efficiency and safety.

[0059] In some embodiments of the present invention, the natural gas hydrate reservoir reformation and production enhancement experimental device also includes a control system, which includes a PID system for controlling production pressure. In conjunction with the control system, the present invention can achieve automatic control of outlet pressure, thereby realizing the purpose of automated production and intelligent monitoring.

[0060] In some embodiments of the present invention, the data acquisition system includes a resistance measurement system, a temperature and pressure testing system, a gas-liquid flow measurement system and a sand production measurement system, a data acquisition system, a computer processing system and a large centralized display screen.

[0061] The advantages of the present invention also include:

[0062] 1. Ability to conduct displacement tests under simulated reservoir conditions and meet the requirements for the development of multiple related experimental technologies;

[0063] 2. Imported key components can improve the reliability and accuracy of the test; ensure the safety, accuracy and stability of key components such as metering or control parts and safety protection; key materials are made of special materials to ensure that the fluid can withstand high pressure and can ensure easy loading and unloading of the simulation test kettle 1;

[0064] 3. Realize computer automatic collection and processing, and realize human-computer dialogue;

[0065] 4. Use advanced and reliable control hardware and software, and apply reliable control methods to ensure stable and reliable system operation, so as to achieve the purpose of unattended operation;

[0066] 5. The present invention adopts multiple safety protection measures, is designed with an electric contact pressure gauge and a safety valve, and is equipped with a safety alarm system. The temperature and pressure alarm values ​​can be set. The instrument can alarm and automatically cut off the power supply in the event of overpressure or overtemperature, ensuring the safety of equipment and life.

[0067] 6. The simulation test kettle 1 is designed with a special sediment loading and unloading tool to facilitate the loading and unloading of sediment into and out of the simulation kettle.

[0068] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

Claims

1. A natural gas hydrate reservoir transformation and production increase experimental device, characterized in that: It includes a simulation reactor, and a high-pressure sand filling system, a seam-making loading system, a pressure-overloading system, a gas pressurization system, a fracturing system and a data acquisition system respectively connected to the simulation reactor; During the simulation test, a reservoir medium is arranged in the simulation reactor, and various seam widths and / or seam shapes are simulated in the simulation reactor by the seam creation loading system, the reservoir medium is compacted by the high-pressure sand filling system, the seabed overburden is simulated on the reservoir medium by the overburden loading system, the gas is pressurized by the gas boosting system and then enters the simulation reactor, the fracturing fluid or proppant is injected into the simulation reactor by the fracturing system, and the experimental data is acquired by the data acquisition system.

2. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: At least one horizontal production well and at least one vertical production well are arranged in the simulated reactor; The data acquisition system may be arranged in the horizontal production well and the vertical production well to acquire pressure values ​​and / or temperature values ​​in the horizontal production well and the vertical production well.

3. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The simulated reactor is equipped with an end cover, a sediment loading and unloading tool and a lifting mechanism; The end cover seals the simulated reactor, and the sediment loading and unloading is realized between the simulated reactor and the simulated reactor. The lifting mechanism is used to adjust the height of the simulated reactor.

4. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 3 is characterized in that: The exterior of the simulated reactor is provided with a heat-insulating jacket, and the simulated reactor is placed in a low-temperature water bath.

5. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The gas boosting system comprises an air compressor, a boosting pump, a gas storage tank and a pressure regulating valve which are connected in sequence, and the pressure regulating valve is connected to the simulation reactor.

6. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The fracturing system includes a fracturing pump connected in sequence, an intermediate container and a stirring container respectively connected to the fracturing pump, and the pressure pump is connected to the simulation reactor through the intermediate container or the stirring container.

7. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The natural gas hydrate reservoir transformation and production increase experimental device also includes a control system, and the control system includes a PID system, and the PID system is used to control the production pressure.

8. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The data acquisition system includes a resistance measurement system, a temperature and pressure test system, a gas-liquid flow measurement system and a sand production measurement system, a data acquisition system, a computer processing system and a large centralized display screen.

9. The natural gas hydrate reservoir transformation and production increase experimental device according to claim 1, characterized in that: The slit-making loading system includes a slit-making hydraulic cylinder, a displacement lead-out rod and a slit-making blade. The blade is controlled to move downward by a hydraulic device to slit the reservoir. Various slit shapes and widths can be simulated by replacing different cutters and changing the displacement of the cutters.

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