WO2021239151A1 - Novel device and method for developing natural gas hydrate - Google Patents

Abstract

A novel device and method for developing natural gas hydrate. Said device comprises a power plant high-temperature water vapor injection pipeline (1), a heat exchange device, a low-temperature return-water recovery pipeline (4), a CO ₂ injection pipeline (6) and a CH ₄ extraction pipeline (7), the heat exchange device being provided in a natural gas hydrate reservoir; the power plant high-temperature water vapor injection pipeline (1) is connected to a water inlet of the heat exchange device, a water outlet of the heat exchange device is connected to one end of the low-temperature return-water recovery pipeline (4), and the other end of the low-temperature return-water recovery pipeline (4) extends out of a seawater layer and is provided at a ground end; one end of the CO ₂ injection pipeline (6) is connected to a CO ₂ storage tank, and the other end of the CO ₂ injection pipeline (6) extends into the bottom of the natural gas hydrate reservoir; one end of the CH ₄ extraction pipeline (7) is provided at the top of the natural gas hydrate reservoir, and the other end thereof is connected to a CH ₄ storage tank; and the CO ₂ injection pipeline (6) and the CH ₄ extraction pipeline (7) are provided in an inner cavity of the heat exchange device.

Description

New development device and method for natural gas hydrate Technical field

The invention relates to the technical field of natural gas hydrate exploration and development, in particular to a novel natural gas hydrate development device and method.

Background technique

Natural gas hydrate is _{a kind of ice cage-like solid compound formed by natural gas (CH 4} ) and water under high pressure and low temperature environment. It is mainly distributed in tundra environments such as polar regions and plateaus and underwater stratum environments such as deep sea and deep water. Because its combustion has little impact on the environment, it is a new type of high-efficiency clean energy and has great resource potential to replace traditional fuels. Therefore, it has been favored by various countries and major energy companies in recent years. Although a series of natural gas hydrate mining methods have been formed, such as depressurization method, thermal excitation method, inhibitor method, CO ₂ replacement method and solid mining method, the efficiency of various natural gas hydrate mining methods is low due to the use of various natural gas hydrate mining methods alone. , High energy consumption, high cost, etc., so it is often necessary to combine two or more mining methods to be used at the same time to realize the economic and sustainable exploitation of submarine natural gas hydrate. At present, the relatively mature combined mining methods mainly include the pressure-reducing-thermal excitation combined mining method, the pressure-reducing-inhibitor combined mining method, and the CO ₂ replacement-inhibitor combined mining method.

The circulating water, tail water and flue gas produced by thermal power plants often carry a large amount of heat energy. Cooling tower circulating water below a certain temperature threshold will no longer be used and directly discharged, resulting in an overall low heat utilization rate of the power plant. If this kind of waste heat is used as the heat source in the traditional thermal excitation method, the utilization rate of thermal energy in power plants can be improved, and the energy consumption of producing high-temperature fluids during the development of natural gas hydrate can be greatly reduced, thereby controlling the mining cost of natural gas hydrate. In addition, the flue gas after combustion often carries a large amount of CO ₂ gas. If it is directly discharged into the air, it will cause _{a waste of CO 2} resources on the one hand, and will also contribute to the greenhouse effect on the other hand. If the CO _{2 is} injected into the submarine natural gas hydrate reservoir, it can promote the decomposition of natural gas hydrate through displacement and accelerate the formation of _{CH 4 gas.} Therefore, it is necessary to propose a new type of power plant-natural gas hydrate joint development device to maximize the energy efficiency of the power plant side and the subsea natural gas hydrate side.

Summary of the invention

The purpose of the present invention is to provide a new type of natural gas hydrate development device and method, which solves the defects of high cost and low efficiency in the prior art for natural gas hydrate mining methods; at the same time, the circulating water and tail water produced by thermal power plants There is a problem of waste of resources with the heat energy of the flue gas.

In order to achieve the above objective, the technical solution adopted by the present invention is:

The invention provides a new development device for natural gas hydrate, which includes a power plant high-temperature water vapor injection pipeline, a heat exchange device, a low-temperature return water return pipeline, a CO ₂ injection pipeline, and a CH ₄ extraction pipeline, wherein the exchange The heating device is placed in the natural gas hydrate reservoir; the high temperature water vapor injection pipeline of the power plant is connected to the water inlet of the heat exchange device, and the water outlet of the heat exchange device is connected to one end of the low temperature return water return pipeline. The other end of the drainage pipeline extends out of the seawater layer and is placed on the ground end; _{one end of the CO 2} injection pipeline is connected to a CO ₂ storage tank, and the _{other end of the CO 2} injection pipeline extends to the bottom of the natural gas hydrate reservoir ; One end of the CH ₄ pumping pipeline is placed on the top of the natural gas hydrate reservoir, and the other end is connected to the CH ₄ storage tank; the CO ₂ injection pipeline and the CH ₄ pumping pipeline are placed in the inner cavity of the heat exchange device middle.

Preferably, a drain pump is provided at the water outlet of the low-temperature return water flowback pipeline.

Preferably, _{one end of the CH 4} gas extraction pipeline placed on the seabed is provided with a gas production pipe hole, and the free end of the gas production pipe hole is placed at the bottom of the natural gas hydrate reservoir.

Preferably, an air pump is provided at one end of _{the CH 4 air pumping pipeline extending from the ground end.}

Preferably, the heat exchange device includes at least two heat exchange row pipes, and two adjacent heat exchange row pipes are connected by a pipe, wherein the water inlet of the heat exchange row pipe placed in the first place is connected to the high temperature water vapor injection of the power plant Pipeline connection; the water outlet of the heat exchange row pipe at the tail is connected with the low-temperature return water return pipeline.

Preferably, when there are two heat exchange row pipes, the CO ₂ injection pipe and CH ₄ gas extraction pipe are placed between the two heat exchange row pipes; when the number of heat exchange row pipes is greater than two At this time, the heat exchange row pipes are arranged in a circumferential structure, and the CO ₂ injection pipeline and the CH ₄ gas extraction pipeline are placed in the cavity formed by the heat exchange row pipes.

Preferably, the pipeline is placed under the natural gas hydrate reservoir.

Preferably, the height of the heat exchange tube is consistent with the thickness of the natural gas hydrate reservoir.

A new natural gas hydrate development method, based on the described new natural gas hydrate development device, includes the following steps:

Step 1: Inject the high-temperature tail water and CO _{2 of the} power plant into the high-temperature water vapor injection pipeline and the CO ₂ injection pipeline respectively, and perform water and gas test to determine whether the device is operating normally;

Step 2: Inject the high-temperature tail water of the power plant into the high-temperature water vapor injection pipeline until the low-temperature return water return pipeline produces a stable fluid; _{slowly pass the CO 2} gas captured by the power plant into the _{CO 2} injection pipeline, and start CH ₄ pumping Air pump until a stable mixture _{of CH 4} and CO ₂ is produced in the _{CH 4 pumping pipeline;}

Step 3. After stable water and gas production, based on numerical simulation results and site conditions, continuously adjust the temperature and rate of injection of high-temperature water vapor, CO ₂ gas injection rate, and gas injection/extraction pressure. Under the premise, to achieve the optimal concentration and rate of _{CH 4 gas production;}

Step 4. When the _{gas production rate of CH 4} decreases, turn off the suction pump and the water pump in turn, and close the well.

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a new natural gas hydrate development device, which heats the natural gas hydrate reservoir through heat exchange pipes, thereby causing the natural gas hydrate to overflow, and at the same time using CO _{2 to} replace the natural gas hydrate to form a power plant supply The three-method joint development device of submarine natural gas hydrate pressure reduction-thermal excitation-CO ₂ replacement for heating and supplying CO _{2 will stably seal the CO 2 produced by the power plant on the seabed, and provide CH 4} gas for the energy supply of the power plant, which is beneficial to the global CO ₂ Emission reduction and alleviation of world energy pressure are of positive significance. It not only achieves effective cooling of power plant tail water/tail steam and CO ₂ emission reduction, but also improves the mining efficiency of submarine natural gas hydrates, and ensures the long-term stability and stability of the energy supply system. Win-win development.

The invention provides a new natural gas hydrate development method, which is a three-method joint development method of submarine natural gas hydrate decompression-thermal excitation-CO _{2 replacement for power plant heating and CO 2} supply. This method can fully benefit the power plant tail Heat, improve the mining efficiency of natural gas hydrates and reduce the cost of thermal excitation during the mining process; at the same time, the produced natural gas can also be used for heating in power plants, achieving the development goal of a win-win situation and increased production.

Description of the drawings

Figure 1 is a flow chart of the development method involved in the present invention;

Figure 2 is a schematic diagram of the structure of the development device involved in the present invention

Figure 3 is a schematic diagram of the heat cycle and CO ₂ -CH _{4 cycle involved in the present invention.}

Detailed ways

In the following, the present invention will be further described in detail with reference to the accompanying drawings.

Based on the above analysis, the present invention proposes a new development device for natural gas hydrate, which not only realizes the effective cooling of power plant tail water/tail steam and CO ₂ emission reduction, but also improves the mining efficiency of submarine natural gas hydrate and ensures the energy supply system. Long-term stability and win-win development. In order to improve the comprehensive utilization efficiency of power plants' energy and resources, and at the same time promote the extraction volume and rate of natural gas hydrate.

The present invention is mainly based on the establishment of a new natural gas hydrate development device based on the schematic diagram of the device, and _{test water and gas respectively to the high-temperature water vapor injection pipeline and the CO 2} injection pipeline to observe whether the device is operating normally; secondly, the device is debugged in sequence In the heat circulation pipeline and CO ₂ -CH ₄ circulation pipeline in the, after the pipeline outlet produces a stable fluid and a stable CH ₄ -CO ₂ mixed gas, based on the numerical simulation results and on-site conditions, continuously adjust the temperature and rate of the injection of high-temperature water vapor , CO _{2 injection rate and pumping / pumping pressure to ensure that the optimal CH 4} gas production concentration and rate can be achieved under the premise of normal operation of the power plant; finally, it is not possible to wait until the CH ₄ gas production rate is significantly reduced or through repeated adjustments. After obtaining the economically beneficial CH ₄ concentration, turn off the air pump and the water pump in turn, recover the device pipelines one by one, and close the wells.

Specifically, the present invention provides a new development device for natural gas hydrate, which includes a power plant high-temperature water vapor injection pipeline 1, a heat exchange pipe 2, a pipeline 3, a low-temperature return water return pipeline 4, a drainage pump 5, and CO ₂ The injection pipeline 6, the CH ₄ gas extraction pipeline 7, the gas extraction pipe hole 8 and the gas extraction pump 9. Among them, the power plant high temperature water vapor injection pipeline 1 is connected to the heat exchange pipe 2; the heat exchange pipe 2 is arranged in the natural gas hydrate storage In the layer; the heat exchange row pipes 2 are provided with at least two, and the two heat exchange row pipes 2 are connected by a pipeline 3, and the pipeline 3 is arranged under the natural gas hydrate reservoir.

The water outlet of the other heat exchange exhaust pipe 2 is connected to the water inlet of the low-temperature return water return pipeline 4, and the water outlet of the low temperature return water return pipeline 4 is provided with a drain pump 5.

_{A CO 2} injection pipeline 6 is provided at the bottom of the natural gas hydrate reservoir. The _{subsea end of the CO 2} injection pipeline 6 is placed between two or more heat exchange tubes 2, and the free end extends out of the seawater layer and Power plant CO ₂ storage tank connection.

_{A CH 4} pumping pipeline 7 is provided on the top of the natural gas hydrate reservoir. _{One end of the CH 4} pumping pipeline 7 placed on the seabed is provided with a gas production pipe hole 8, and the free end of the gas production pipe hole 8 is placed in natural gas. The bottom of the hydrate reservoir.

The free end of the CH ₄ pumping pipe 7 extends out of the ground end, and a pump 9 is provided at this end.

The CO ₂ injection pipe 6 and the CH ₄ gas extraction pipe 7 are placed between the two heat exchange pipes 2.

When a plurality of heat exchange row tubes 2 are provided, the plurality of heat exchange row tubes 2 are arranged in a circumferential structure.

The height of the heat exchange pipe 2 is close to the thickness of the natural gas hydrate reservoir, and the pipe wall should be made of materials with good thermal conductivity, high heat exchange efficiency, seawater corrosion resistance, and moraine abrasion resistance.

The pipeline 3 should be made of materials with good thermal insulation performance and corrosion resistance, and should be laid under the natural gas hydrate reservoir.

The pipe walls of the high-temperature water vapor injection pipeline 1, the low-temperature return water return pipeline 4, the CO ₂ injection pipeline 6 and the CH ₄ extraction pipeline 7 should be made of materials with good thermal insulation performance, fluid sealing performance, and corrosion resistance.

The setting range of the gas production pipe hole 8 should cover the entire height of the natural gas hydrate reservoir, so that the CO ₂ -CH ₄ gas can pass smoothly, but it is better to effectively filter the sand and gravel/loose sediment on the seabed.

The pipelines, components, and valves should be reliably connected and should not be significantly deformed under submarine temperature and pressure. Except for the CO ₂ injection pipeline 6 and the CH ₄ gas extraction pipeline 7 subsea ends, they should be kept closed.

As shown in Figure 1, the operating steps of the device are:

Step 1. Build a new natural gas hydrate development device based on the schematic diagram of the device of the present invention.

First, lay a heat exchange pipe 2 that is as thick as the reservoir in the submarine gas hydrate reservoir. The wall of the heat exchange pipe 2 should be made of materials with good thermal conductivity, high heat exchange efficiency, seawater corrosion resistance, and moraine abrasion resistance. ; If multiple heat exchange pipes 2 need to be laid, the bottom of each heat exchange pipe 2 should be connected with a pipeline 3 with good heat preservation and corrosion resistance under the natural gas hydrate.

After the heat exchange tube 2 and the pipeline 3 are buried, the bottom of the high temperature steam injection pipeline 1 and the low temperature return water return pipeline 4 are reliably connected to the top of the heat exchange tube 2, and the top of the pipeline leads to the power plant. High temperature tail water/tail steam outlet and low temperature return pool; the pipe wall should be made of materials with good heat preservation performance and corrosion resistance, and the connection parts should have good sealing performance.

The top outlet of the low-temperature return water return pipeline 4 should also be provided with a water pump 5 to regulate the flow rate of the exchange hot water.

The _{bottom of the CO 2} injection pipeline 6 and the CH ₄ gas extraction pipeline 7 extend into the bottom of the natural gas hydrate reservoir, and the upper part of the pipeline leads to the CO ₂ capture outlet of the _{power plant and the CH 4} gas extraction/gas inlet, respectively. The wall should be made of materials with good thermal insulation properties and resistance to seawater and CO _{2 corrosion.}

The part of the CH ₄ gas pumping pipeline 7 within the range of the natural gas hydrate reservoir should be provided with a gas production pipe hole 8 with a certain filtering function to increase the CH ₄ gas collection rate.

An exhaust pump 9 with regulating function should be installed near the outlet of the top of the CH ₄ extraction pipeline 7 to control the extraction pressure and rate; the top of all pipelines should be reliably and stably connected to the corresponding parts of the power plant.

Step 2: Test the water and gas into the high-temperature water vapor injection pipe 1 and CO ₂ injection pipe 6, respectively, and observe whether the device is operating normally;

Pass the high-temperature tail water/tail steam and the captured CO _{2 of the} power plant into the high-temperature water vapor injection pipe 1 and the CO ₂ injection pipe 6 in sequence, and observe the low-temperature return water flowback pipe 4 and the CH ₄ gas extraction pipe 7 Whether the water flow and air flow can be produced stably, and at the same time, the entire device is monitored for abnormal conditions such as significant temperature and pressure changes and well instability. If there is an abnormal situation, you should stop water/gas injection and water pumping/gas pumping immediately, investigate the cause of the abnormality, and retest the water/gas after the problem is solved. After stable water/gas production, stop the water/gas test and wait for the formal natural gas hydrate exploitation.

Step 3. Debug the heat circulation pipeline: slowly inject the high temperature tail water of the power plant into the high temperature water vapor injection pipeline 1, start the pump 5, adjust the injection water vapor and pumping rate, until the low temperature return water return pipeline 4 can produce stable output Until low temperature fluid.

After the water test and gas test of the device are normal, start to inject the high temperature tail water/tail steam of the power plant into the high temperature water vapor injection pipeline 1, and slowly start the pump 5, and observe the return water temperature and the return water temperature of the low temperature return water return pipeline 4 at any time. flow. Gradually adjust the pumping pressure of the pump 5, and when the heat exchange efficiency η of the device reaches the best, stop adjusting the pumping pressure and keep it stable. The calculation method of the heat exchange efficiency η of the device is:

η=C _m ·Q·(T _in -T _out )

Wherein, C _m water / vapor heat capacity, J / (t · ℃) ; Q is a return flow, t / h; T _in and T _out are injected into a high temperature vapor and low temperature of the return water, ℃.

Step 4. Debug the CO ₂ -CH ₄ circulation pipeline: _{slowly pass the CO 2} gas captured by the power plant into the _{CO 2} injection pipeline 6, start the CH ₄ extraction pump 9 slowly, and observe whether the CH ₄ extraction pipeline 7 is in place Produce stable CH ₄ and CO ₂ mixed gas.

CO ₂ is injected into the conduit 6 and the outlet is connected to CO ₂ capture plant, until the CO ₂ capture operational means, a slow start the suction pump 9 CH _4; CH ₄ is gradually increased suction pressure pump 9, the pumping rate is not greater than The _{gas production efficiency of the CO 2} capture device; until the CH ₄ gas extraction pipeline 7 starts to produce a higher concentration of CH ₄ gas, the pressure adjustment of the gas extraction pump 9 is suspended and remains stable for a period of time.

Step 5. Based on numerical simulation results and site conditions, continuously adjust the injection temperature and rate of high temperature water vapor, CO ₂ injection rate and gas injection/extraction pressure to ensure that the CH ₄ gas production concentration and rate are achieved under the premise of normal operation of the power plant Optimal.

In the new natural gas hydrate development device, _{multiple circulation pipelines such as heat circulation and CO 2} -CH ₄ carbon circulation are involved. Therefore, it is necessary to optimize the design of the natural gas hydrate extraction efficiency of the device through various means, as shown in Figure 3. Numerical simulation can conduct integrated thermal-chemical-mechanical coupling check calculations for heat exchange, natural gas hydrate phase change, CO ₂ replacement and pressure effects involved in the device, and the simulation results can provide guidance for the operation of the device.

As numerical simulation often ignores the problems of heat loss and gas escape in the actual natural gas hydrate mining process, it is more important to use the specific conditions of the site to repeatedly debug various data to achieve CH ₄ production, production rate, and cooling efficiency. Optimization of related indicators.

Step 6. When the CH ₄ gas production rate is significantly reduced or the economically beneficial CH ₄ concentration cannot be obtained through repeated debugging, turn off the suction pump 9, the water pump 5, the CO ₂ injection pipe 6 and the high temperature water vapor injection pipe 1 in turn , Item by item recovery device pipeline and seal well.

Through production estimation and economic evaluation, if it is found that the _{gas production of CH 4} has no economic value for further development, relevant measures should be taken to stop production and shut down the well in time. Discontinued process should be gradual, in turn reduced pressure and suction pump 9 is gradually closed, pumps 5, gradually reduce the CO ₂ injection line 6 and a high temperature water vapor in the injection line and the high-temperature CO ₂ injection rate of water vapor injection amount until the entire gas hydrate After the gas and water production of the new-type development device is basically zero, the water pump 5, the air pump 9, each pipeline and the heat exchange pipe 2 are sequentially recovered to stabilize the natural gas hydrate reservoir and close the well.

The present invention can provide a method that can effectively utilize the high-temperature waste heat of the power plant and the CO ₂ captured, and improve the utilization efficiency of the energy and resources of the power plant; at the same time, the combined thermal excitation method, depressurization method, CO ₂ replacement method and other natural gas The hydrate development method can comprehensively improve the gas production and mining efficiency _{of CH 4 ; and it can also stably store the CO 2} generated by the power plant on the seabed, and provide CH ₄ gas for the power plant, reducing global CO ₂ emissions and alleviating the world's energy Stress has a positive meaning. The invention utilizes a relatively simple device to realize relatively high-efficiency exploitation of submarine natural gas hydrate, and has good promotion significance in the field of natural gas hydrate development and design.

The above are only specific embodiments of the present invention and cannot be used to limit the scope of implementation of the invention. Therefore, replacement of equivalent components or equivalent changes and modifications made in accordance with the scope of protection of the present invention shall still fall within the scope of the present invention. category.

Claims (9)

1. A new development device for natural gas hydrate, which is characterized in that it includes a power plant high-temperature water vapor injection pipeline (1), a heat exchange device, a low-temperature return water return pipeline (4), a CO ₂ injection pipeline (6), and CH ₄ The gas extraction pipeline (7), wherein the heat exchange device is placed in the natural gas hydrate reservoir; the power plant high temperature water vapor injection pipeline (1) is connected to the water inlet of the heat exchange device, and the water outlet of the heat exchange device is connected to the low temperature One end of the return water return pipeline (4), the other end of the low temperature return water return pipeline (4) extends out of the seawater layer and is placed on the ground end; one end of the CO ₂ injection pipeline (6) is connected to CO ₂ storage tank, the _{other end of the CO 2} injection pipeline (6) extends to the bottom of the natural gas hydrate reservoir; _{one end of the CH 4} gas extraction pipeline (7) is placed on the top of the natural gas hydrate reservoir, The other end is connected to the CH ₄ storage tank; the CO ₂ injection pipeline (6) and the CH ₄ gas extraction pipeline (7) are placed in the inner cavity of the heat exchange device.
2. A new natural gas hydrate development device according to claim 1, characterized in that a drainage pump (5) is provided at the outlet of the low-temperature return water return pipeline (4).
3. A new type of natural gas hydrate development device according to claim 1, characterized in that, _{one end of the CH 4} gas extraction pipeline (7) placed on the seabed is provided with a gas production pipe hole (8), and the gas production pipe hole ( The free end of 8) is placed at the bottom of the gas hydrate reservoir.
4. The new natural gas hydrate development device according to claim 1, characterized in that, an air pump (9) is provided at one end of _{the CH 4 pumping pipeline (7) extending from the ground end.}
5. The new natural gas hydrate development device according to claim 1, characterized in that the heat exchange device comprises at least two heat exchange pipes (2), one of two adjacent heat exchange pipes (2) It is connected by a pipeline (3), where the water inlet of the heat exchange row pipe (2) placed in the first place is connected to the high temperature water vapor injection pipeline (1) of the power plant; the water outlet of the heat exchange row pipe (2) placed at the rear Connect with the low-temperature return water return pipeline (4).
6. The new natural gas hydrate development device according to claim 5, characterized in that, when two heat exchange pipes (2) are provided, the CO ₂ injection pipeline (6) and the CH ₄ gas extraction pipeline (7) Placed between two heat exchange pipes (2); when the number of heat exchange pipes is greater than two, the heat exchange pipes are arranged in a circumferential structure, and the CO ₂ injection pipeline ( 6) and the CH ₄ gas extraction pipeline (7) are placed in the cavity formed by the heat exchange tube (2).
7. The new natural gas hydrate development device according to claim 5, characterized in that the pipeline (3) is placed under the natural gas hydrate reservoir.
8. The new natural gas hydrate development device according to claim 1, characterized in that the height of the heat exchange pipe (2) is consistent with the thickness of the natural gas hydrate reservoir.
9. A new natural gas hydrate development method, which is characterized in that, based on a new natural gas hydrate development device according to any one of claims 1-8, it comprises the following steps:

   Step 1. Inject the high-temperature tail water and CO _{2 of the} power plant into the high-temperature water vapor injection pipeline (1) and the CO ₂ injection pipeline (6) respectively, and conduct a water and gas test to determine whether the device is operating normally;

   Step 2: Inject the high-temperature tail water of the power plant into the high-temperature water vapor injection pipeline (1) until the low-temperature return water return pipeline (4) produces a stable fluid; the CO ₂ injection pipeline (6) is slowly passed into the power plant's capture CO ₂ gas, CH ₄ starts suction pump (9), until the exhaust conduit stable CH ₄ mixed _gas of CH ₄ and CO (7) is generated;

   Step 3. After stable water and gas production, based on numerical simulation results and site conditions, continuously adjust the temperature and rate of injection of high-temperature water vapor, CO ₂ gas injection rate, and gas injection/extraction pressure. Under the premise, to achieve the optimal concentration and rate of _{CH 4 gas production;}

   Step 4. When the _{gas production rate of CH 4} decreases, turn off the suction pump and the water pump in turn, and close the well.

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