CN105301200A - Testing apparatus for characteristics of sand production during mining of natural gas hydrate - Google Patents

Abstract

The invention provides a testing device for sand production characteristics of natural gas hydrate exploitation, which includes a simulated sand production system, a pressure system and a measurement system; the simulated sand production system includes a reactor main body, a reactor flange cover and an overlying pressure loading device; the pressure includes an overlying pressure loading system, a natural gas injection pressurization system, a bottom liquid injection system, and a visualized gas-liquid-solid separator; the measurement system includes a data acquisition system, a first pressure sensor, a second pressure sensor, A third pressure sensor and a temperature sensor. The invention is a device capable of in situ simulating the characteristics of sand production under high pressure and low temperature, which expands the application range of existing devices and improves measurement accuracy.

Description

A testing device for sand production characteristics of natural gas hydrate mining

technical field

The invention relates to a device for in-situ synthesis of natural gas hydrate-containing deposits and testing of sand production characteristics during mining, in particular to a device for in-situ simulation of mining sand production characteristics under high pressure and low temperature.

Background technique

Natural gas hydrate is an ice-like solid formed by gas (or volatile liquid) and water under certain temperature and pressure conditions, commonly known as combustible ice, widely distributed in the tundra 200-2100 meters below the surface and between the seabed at the continental margin In the sediments of 0-1100 meters below, there is a huge natural gas storage capacity, and the methane hydrate contains 164 times the natural gas in the standard state. The natural gas hydrate reserves in the world are very huge. It is estimated that the natural gas resources in hydrates are 2×10 ¹⁶ cubic meters, which is equivalent to 2×10 ⁵⁰⁰ million tons of oil equivalent, which is twice the total carbon content of conventional fuels in the world. Natural gas hydrate is listed as an important alternative energy source in the post-petroleum era by developed countries. my country has also included it in the medium and long-term development plan, and will carry out trial mining during the 13th Five-Year Plan period.

However, the exploitation of gas hydrate reservoirs will cause a large amount of gas hydrates to decompose, which will lead to changes in the mechanical properties of hydrate-bearing formations, which may lead to engineering and geological disasters such as wellbore instability, sand production, formation collapse, submarine landslides and even tsunamis. Sand production is a phenomenon in the process of oil and gas production due to the migration of reservoir sand particles from the reservoir with the fluid, and it is also unavoidable in the process of natural gas hydrate production. From the point of view of sand production in conventional oil and gas production, the sand production mechanism is caused by the break of the original pressure balance of the oil and gas reservoir near the bottom of the well, which makes the deposits of the oil and gas reservoir yield, resulting in the destruction of its original structure. In conventional offshore oil and gas extraction, the hazards of sand production mainly include the following aspects: 1. Erosion of oil and gas production equipment. 2. Formation and borehole wall instability. 3. Sand blockage and siltation damage equipment. 4. In offshore oil and gas fields, the disposal of discarded formation sand will pollute the environment.

Therefore, before gas hydrate mining, only by accurately understanding the nature of sand production in the production wellbore can we guide the smooth progress of natural gas hydrate production in the future and reduce the possibility of sand production accidents caused by natural gas hydrate production. However, the existing sand production devices are mainly designed at normal temperature and pressure, which cannot satisfy the in-situ measurement of natural gas hydrate under low temperature and high pressure conditions. To sum up, research and develop the sand production characteristics test device for natural gas hydrate mining, deeply study the sand production characteristics of natural gas hydrates and reservoirs, explore the response mechanism of different influencing factors to the sand production characteristics in hydrate production, and analyze the process of hydrate production. The establishment of an evaluation model for the risk of sand production in gas hydrates is of great significance to the development of gas hydrates.

Contents of the invention

The purpose of the present invention is to provide a device for in-situ synthesis of natural gas hydrate-containing sediments and testing of sand production characteristics during mining, especially a device for in-situ simulation of mining sand production characteristics under high pressure and low temperature, which expands the existing There is a range of use of the device and the measurement accuracy is improved.

To achieve the above object, the present invention proposes the following technical solutions:

A device for testing sand production characteristics of natural gas hydrate mining, characterized in that it includes:

A simulated sand production system, the simulated sand production system includes a reactor main body, a reactor flange cover and an overlying pressure loader, and the reactor flange cover is fixedly installed on the upper end surface of the reactor main body; the reactor main body includes A production wellbore, a sand control mechanism and a sample reservoir chamber, the production wellbore is a hollow cylindrical structure with openings on the side wall, the sample reservoir chamber is located outside the production wellbore, and the sand control mechanism is located between the sample reservoir chamber and the production wellbore , the lower end of the overlying pressure loader communicates with the sample reservoir chamber,

Pressure system, the pressure includes an overlying pressure loading system, a natural gas injection pressurization system, a bottom liquid injection system, and a visible gas-liquid-solid separator; wherein, the upper end of the overlying pressure loader passes through the flange cover of the reactor Afterwards, it communicates with an overlying pressure loading system; the natural gas injection pressurization system and the bottom liquid injection system are both communicated with the sample reservoir chamber, and the visualized gas-liquid-solid separator is communicated with the bottom of the production wellbore; the The visible gas-liquid-solid separator is provided with a gas outlet and a liquid outlet;

A measurement system, the measurement system includes a data acquisition system, a first pressure sensor, a second pressure sensor, a third pressure sensor and a temperature sensor; the first pressure sensor is installed between the natural gas injection pressurization system and the sample reservoir chamber On the pipeline between, the temperature sensor and the second pressure sensor are installed on the flange cover of the reaction kettle, the third pressure sensor is installed on the pipeline between the visualized gas-liquid-solid separator and the production wellbore, and the first The first pressure sensor, the second pressure sensor, the third pressure sensor, the temperature sensor and the fourth pressure sensor attached to the overlying pressure loader are all connected to the data acquisition system.

The main body of the reaction kettle is a special pressure vessel, which can withstand high pressure and low temperature without leakage or deformation, and can promote porous media, natural gas and water to synthesize hydrate-containing porous media samples inside the pressure chamber under the specified high pressure and low temperature ranges, so that meet the requirements of the test.

The porous media described in the present invention can be various types of sediments, such as seabed sediments, lake sediments, frozen soil and the like. However, since the sample fidelity is required to simulate mining during the testing process, however, hydrate samples can only be measured effectively under high pressure and low temperature conditions. Difficult to obtain fidelity samples to test. Therefore, after the sediment in the target area is selected in the present invention, the sediment is surrounded by the overlying pressure loader to make samples around the production wellbore. Sediment sample preparation is an important link in the test process, which directly affects the test results, so the process must be carried out in strict accordance with the operating procedures.

The natural gas injection pressurization system includes a gas source, a gas pressure increasing and decreasing pump, and a buffer tank. A first pressure sensor and a safety valve are installed on the air source pipeline.

The natural gas injection pressurization system communicates with the side of the sample reservoir chamber, and the bottom liquid injection system communicates with the bottom of the sample reservoir chamber.

The sand control mechanism includes a sand control pipe and a sand control net. The sand control pipe is a porous hollow cylindrical structure. The production shaft is located in the sand control pipe, and the sand control net is located between the production well shaft and the sand control pipe.

The test device for sand production characteristics of natural gas hydrate mining further includes a temperature control system, the temperature control system includes a constant temperature circulating water bath, a reactor external water jacket and a built-in heat exchange tube in the reactor, and the reactor external water jacket Located on the outside of the sample reservoir chamber and attached to the sample reservoir chamber, the internal heat exchange tube of the reaction kettle is installed in the sample reservoir chamber and jacketed with the water outside the reaction kettle, and the constant temperature circulating water bath is connected to the reaction chamber through the connecting pipeline. The water jacket outside the kettle is connected. The liquid in the constant temperature circulating water bath passes through the connecting pipe, the internal heat exchange tube of the reaction kettle and the outer water jacket of the reaction kettle, and then flows back to the constant temperature bath through the connecting pipe to complete the cycle and maintain the constant temperature of the reaction kettle.

The reactor flange cover is fixedly connected to the upper end surface of the reactor main body through the reactor flange bolts, and is sealed by a sealing ring between the reactor flange cover and the reactor main body.

The data collected by the data acquisition system include overlying loading pressure, pore pressure, temperature, and gas flow. The temperature and pressure transmit signals to the data acquisition and control system through the corresponding sensors, which are read by the measurement and control acquisition system and sent to the computer for display, recording and analysis of the data. Among them, the output and sand output are separated and collected in a visual gas-liquid-solid separator, the water output and sand output are obtained by weighing the gas-liquid-solid separator, and the sand output is obtained by drying sand and weighing records, and the gas output After passing through the gas-liquid-solid separator, it is dried, and measured and recorded by a gas flow meter.

The steps to use this device are as follows:

(a) Check the airtightness of the equipment: connect the corresponding drainage and exhaust pipes, close and seal the mining reaction kettle, keep the temperature at room temperature, use the side air pipe to inject nitrogen gas, and use detergent water to test the airtightness along the seam. If the airtightness is good, go to the next step.

(b) Sample filling: Open the flange cover of the reaction kettle, fill it with water-containing sand into the sand storage layer for compaction, and close the upper flange cover for sealing.

(c) Hydrate synthesis: open the overlying pressure loading system, load the initial overlying pressure, and gradually lower the temperature to the initial temperature (usually at 20°C), and the gas injection pressurization system supplies methane gas from the side intake pipe to generate natural gas hydrate After the air pressure is stable, it will be stable for 24 hours. Then cool down to the required hydrate synthesis temperature, and record the overlying loading pressure (measured by the fourth pressure sensor attached to the overlying pressure loader), temperature (the temperature inside the main body of the reactor, measured by the temperature sensor) every 10 seconds ), pore pressure (measured by the second pressure sensor), air intake (the amount of natural gas injected into the sample reservoir chamber by the natural gas injection pressurization system), and liquid intake (the amount of water injected into the sample reservoir chamber by the bottom liquid injection system) . If there is a need for gas-saturated or liquid-saturated experiments, it is also necessary to inject gas at the side or inject liquid at the bottom after the sample is synthesized for sample preparation.

(d) Sand production in the pressure chamber: the mining port at the bottom of the wellbore is subjected to pressure reduction/heat injection mining with the set pressure reduction rate/heat injection rate and other parameters, and the overlying loading pressure, temperature, and pores are recorded at regular intervals. The pressure, air intake and liquid intake will wait until solids appear in the visualized gas-liquid-solid separator or reach a certain sand output or the end of mining. Among them, the output and sand output are separated and collected in a visual gas-liquid-solid separator, the water output and sand output are obtained by weighing the gas-liquid-solid separator, and the sand output is obtained by drying sand and weighing records, and the gas output After passing through the gas-liquid-solid separator, it is dried, and measured and recorded by a gas flow meter.

Compared with the prior art, the beneficial effect of the present invention is that: the present invention provides a device that synthesizes in situ at high pressure and low temperature and simulates the characteristics of mining sand, which expands the application range of existing devices and improves measurement accuracy.

Description of drawings

Fig. 1 is a structural block diagram of a testing device for sand production characteristics of natural gas hydrate mining in the present invention;

Fig. 2 is the matching structure diagram of the reaction kettle flange cover and the overlying pressure loader in Fig. 1;

Fig. 3 is a layered view of the interior of the reactor body in Fig. 1 .

Explanation of reference signs:

1. Gas source; 2. Gas increasing and reducing pump; 3. Buffer tank; 4. First pressure sensor; 5. Safety valve; 6. Reactor flange cover; 7. Reactor body; 8. Temperature sensor; 9 10. Pressure reducing valve; 11. Third pressure sensor; 12. Gas outlet; 13. Liquid outlet; 14. Visual gas-liquid-solid separator; 15. Data collector; 16. Constant temperature circulating water bath ; 17. Overlying pressure loader; 18. Overlying pressure loading system; 19. Bottom liquid injection system; 20. Production shaft; 21. Sand control pipe; 22. Sample reservoir chamber; 23. Reactor outer water jacket; 24. Reactor built-in heat exchange tube; 25. Reactor flange bolts; 26. Sand control net.

detailed description

The content of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example:

Gas hydrate is an enveloping crystal formed by the interaction of gas or volatile liquid with water. Gas hydrate needs to exist under high pressure and low temperature, so its physical properties need to be measured in situ.

Based on the above principles, the present invention provides a device for in-situ simulating sand production characteristics under high pressure and low temperature, so as to improve measurement accuracy. As shown in Fig. 1, a device for in-situ synthesis of gas hydrate-containing sediments and testing of sand production characteristics during exploitation includes a pressure system, a simulated sand production system, a measurement system, and a temperature control system.

The simulated sand production system consists of the main body of the reactor 7, the flange cover of the reactor 6 and the overlying pressure loader 17, which can realize the in-situ synthesis of natural gas hydrate and the simulation of sand production during mining. The reaction kettle main body 7 and the reaction kettle flange cover 6 are special pressure vessels made of stainless steel, and the two are connected by flange cover bolts 25 and sealed with sealing rings.

Please refer to FIGS. 1 and 3 , the reactor main body 7 is composed of a production wellbore 20 , a sand control pipe 21 and a sample reservoir chamber 22 . The production shaft 20 and the sand control pipe 21 are made of stainless steel pipes. The sand control pipe 21 is composed of two porous steel pipes (large-pore pipe and small-pore pipe) and a sand control screen 26 with multiple specifications of filter gauze inside, and is set around the production shaft 20. , and be replaced according to the needs of the experiment; the sample reservoir chamber 22 surrounds the sand control pipe 21 and can be filled with different types of sediment samples to simulate the reservoir in the mining area.

The pressure system is divided into an overlying pressure loading system 18, a bottom liquid injection system 19 and a gas pressure system. in:

The overlying pressure loading system 18 mainly provides the overlying pressure required for the experiment and simulates formation stress. Please refer to Fig. 2, the overlying pressure loader 17 passes through the reactor flange cover 6 from the top and seals it with a sealing ring. One end of the pressure loader 17 is connected to the overlying pressure loading system 18, and the overlying pressure loading system 18 is pressurized for stress loading; the other end of the overlying pressure loader 17 is hollow cylindrical, and is used to load the overlying pressure to the sample reservoir chamber. Pressure: The top opening of the flange cover 6 of the reaction kettle is connected with the overlying pressure loader 17, the second pressure sensor 9 and the temperature sensor 8, which are used for overlying pressure and temperature measurement in the experiment.

The bottom liquid injection system 19 mainly includes a booster pump, a liquid injection system, a liquid inlet pipeline, etc., and mainly provides high-pressure liquid required for experiments, mainly water.

The gas pressure system includes a natural gas injection pressurization system and a vacuum pumping system: the natural gas injection pressurization system includes a gas source 1, a gas pressure increase and decrease pump 2, and a buffer tank 3. The gas source 1 passes through the gas increase and decrease pressure pump 2 and buffer The tank 3 communicates with the sample reservoir chamber 22 through the gas source pipeline. A first pressure sensor 4 and a safety valve 5 are installed on the gas source pipeline. In addition, an air pressure regulating valve and a gas flow meter are installed on the gas source pipeline. It mainly provides high-pressure gas required for synthetic natural gas. The vacuum system consists of a filter vacuum pump, a vacuum controller, a vacuum regulator and a transparent connecting hose, which mainly provides the vacuum environment required for the experiment.

There are 3 inlets and outlets at the bottom of the main body 7 of the reaction kettle, of which 2 inlets and outlets at the bottom of the sample reservoir chamber are connected to the bottom liquid injection system 19, and the inlet and outlet at the bottom of the production wellbore 20 are connected to the visualized gas-liquid-solid separator 14 through pipelines for Separation of gas-liquid solid substances in mining: Visual gas-liquid-solid separator 14 is provided with a gas outlet 12 and a liquid outlet 13, the gas is discharged through the gas outlet 12, the liquid is discharged through the liquid outlet 13 and the solid is in the separator's internal clapboard filter separate.

The temperature control system is composed of a constant temperature circulating water bath 16 with high and low temperature program controllable, a heat exchange tube 24 inside the reactor, and a water jacket 23 outside the reactor. The constant temperature circulating water bath 16 has a built-in circulating water pump, and is connected with the built-in heat exchange tube 24 of the reaction kettle and the outer water jacket 23 of the reaction kettle through corresponding pipelines. The liquid in the constant temperature bath flows back into the constant temperature circulating water 16 through the internal heat exchange tube 24 of the reaction kettle, the outer water jacket 23 of the reaction kettle and corresponding connecting pipes to complete the circulation, so as to maintain the constant temperature of the main body of the reaction kettle.

The measurement system mainly includes a data acquisition system 15 , a third pressure sensor 11 , a temperature sensor 8 , and a pressure sensor attached to the overlying pressure loader 17 . The temperature, pressure and displacement transmit signals to the data acquisition system through the corresponding sensors to read and display, record and analyze the data through the computer. The temperature and pressure are transmitted to the data acquisition system 15 through the temperature sensor 8, the pressure sensor carried by the overlying pressure loader 17 and the third pressure sensor 11 respectively, and the data is read and processed by the data acquisition system 15 before being transmitted to the computer. display and storage.

In this embodiment, the main process of starting the sand production property test includes:

(a) Check the airtightness of the equipment: connect the corresponding drainage and exhaust pipes, close and seal the mining reactor 7, keep the temperature at normal temperature, feed nitrogen gas through the side air pipe, and test the airtightness along the seam with detergent water. If the airtightness is good, go to the next step.

(b) Sample filling: open the flange cover 6 of the reaction kettle, fill the sample reservoir chamber 22 with water-containing sand for compaction, and close the flange cover 6 of the reaction kettle for sealing.

(c) Hydrate synthesis: Align the overlying pressure loader 17, load the initial overlying pressure, gradually lower the temperature to the initial temperature (usually at 20°C), and the natural gas injection pressurization system supplies methane gas from the side inlet pipe to generate Natural gas hydrate, fully inhaled, and stabilized for 24 hours after the air pressure stabilized. Cool down to the desired hydrate synthesis temperature, and record the overlying loading pressure, temperature, pore pressure, gas flow and liquid flow every 10 seconds.

(d) Sand production in the pressure chamber: set the simulated mining temperature, such as 4°C. The bottom mining port is decompressed with the set depressurization rate or rated outlet pressure and other parameters, such as 2.5MPa (the phase equilibrium pressure of methane hydrate at 4°C is 3.9MPa). Record the overlying loading pressure, temperature, pore pressure, air intake and liquid intake every 10 seconds until solids appear in the visualized gas-liquid-solid separator 14 or a certain sand output is reached or mining ends. Among them, the output and sand output are separated and collected in the visualized gas-liquid-solid separator 14, the water output and sand output are obtained by weighing the visualized gas-liquid-solid separator 14, and the sand output is obtained by drying the sand and weighing records. The output gas is dried after passing through the gas-liquid-solid separator, and is measured and recorded by the gas flow meter.

The materials involved in this example are mainly gases (methane, carbon dioxide, mixed gas, etc.), water and solids (marine sediment samples, etc.).

Various overburden pressures, pore pressures, temperatures, wellhead pressures, air and water inflows, gas production, water production and sand production can be recorded during this process. During the continuous growth stage of hydrates, the amount of gas hydrates generated can be calculated by temperature and pressure.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and its purpose is to enable those of ordinary skill in the art to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the essence of the present invention shall fall within the protection scope of the present invention.

Claims (6)

1. exploitation of gas hydrates shakes out a characteristic test device, and it is characterized in that, it comprises:

Simulate system of shaking out, the described simulation system of shaking out comprises reactor main body (7), reactor blind flange (6) and burden pressure loader (17), and described reactor blind flange (6) is fixedly installed in reactor main body (7) upper surface; Described reactor main body (7) comprises exploitation pit shaft (20), sand control mechanism and Sample Reservoir Layer room (22), described exploitation pit shaft (20) is provided with the hollow cylindrical structure of perforate for sidewall, described Sample Reservoir Layer room (22) is positioned at the outside of exploitation pit shaft (20), sand control mechanism is positioned between Sample Reservoir Layer room (22) and exploitation pit shaft (20), the lower end of described burden pressure loader (17) is connected with Sample Reservoir Layer room (22)

Pressure system, described pressure system comprises burden pressure loading system (18), rock gas gas injection pressure charging system, bottom liquid injection system (19) and visual gas-liquid-solid separator (14); Wherein, the upper end of described burden pressure loader (17) is communicated with a burden pressure loading system (18) afterwards through reactor blind flange (6); Described rock gas gas injection pressure charging system and bottom liquid injection system (19) are all connected with Sample Reservoir Layer room (22), and described visual gas-liquid-solid separator (14) is connected with the bottom of exploitation pit shaft (20); Described visual gas-liquid-solid separator (14) is provided with gas outlet (12) and liquid outlet (13);

Measuring system, described measuring system comprises data acquisition system (DAS) (15), the first pressure transducer (4), the second pressure transducer (9), the 3rd pressure transducer (11) and temperature sensor (8), described first pressure transducer (4) is installed on the pipeline between rock gas gas injection pressure charging system and Sample Reservoir Layer room (22), described temperature sensor (8) and the second pressure transducer (9) are all installed on reactor blind flange (6), described 3rd pressure transducer (11) is installed on the pipeline between visual gas-liquid-solid separator (14) and exploitation pit shaft (20), described first pressure transducer (4), second pressure transducer (9), 3rd pressure transducer (11), the 4th pressure transducer that temperature sensor (8) and burden pressure loader (17) carry all is connected with data acquisition system (DAS) (15).

2. exploitation of gas hydrates according to claim 1 shakes out characteristic test device, it is characterized in that, described rock gas gas injection pressure charging system comprises source of the gas (1), gas increase and decrease press pump (2), surge tank (3), described source of the gas (1) is communicated with Sample Reservoir Layer room (22) by source of the gas pipeline with surge tank (3) through gas increase and decrease press pump (2) successively, and described source of the gas pipeline is provided with the first pressure transducer (4) and safety valve (5).

3. exploitation of gas hydrates according to claim 1 and 2 shakes out characteristic test device, it is characterized in that, described rock gas gas injection pressure charging system is connected with the sidepiece of Sample Reservoir Layer room (22), and described bottom liquid injection system (19) is connected with the bottom of Sample Reservoir Layer room (22).

4. exploitation of gas hydrates according to claim 1 shakes out characteristic test device, it is characterized in that, described sand control mechanism comprises sand-proof pipe (21) and sand control screens (26), described sand-proof pipe (21) is Porous hollow column structure, exploitation pit shaft (20) is positioned at sand-proof pipe (21), and described sand control screens (26) is positioned between exploitation pit shaft (20) and sand-proof pipe (21).

5. exploitation of gas hydrates according to claim 1 shakes out characteristic test device, it is characterized in that, the described exploitation of gas hydrates characteristic test device that shakes out comprises a temperature control system further, described temperature control system comprises thermostatic circulation bath (16), the outer water leg (23) of reactor and reactor inner-heating tube (24), the outer water leg (23) of described reactor is positioned at the outside of Sample Reservoir Layer room (22) and fits with Sample Reservoir Layer room (22), described reactor inner-heating tube (24) to be installed in Sample Reservoir Layer room (22) and to be communicated with the outer water leg (23) of reactor, described thermostatic circulation bath (16) is communicated with by the outer water leg (23) of connecting line and reactor.

6. exploitation of gas hydrates according to claim 1 shakes out characteristic test device, it is characterized in that, reactor blind flange (6) is fixedly connected with by the upper surface of reactor flange bolt (25) with reactor main body (7), is sealed between reactor blind flange (6) and reactor main body (7) by O-ring seal.