CN111749652A - System and method for exploiting natural gas hydrate in frozen soil area through vertical well - Google Patents
System and method for exploiting natural gas hydrate in frozen soil area through vertical well Download PDFInfo
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- CN111749652A CN111749652A CN202010516622.5A CN202010516622A CN111749652A CN 111749652 A CN111749652 A CN 111749652A CN 202010516622 A CN202010516622 A CN 202010516622A CN 111749652 A CN111749652 A CN 111749652A
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/12—Methods or apparatus for controlling the flow of the obtained fluid to or in wells
- E21B43/121—Lifting well fluids
Abstract
The embodiment of the invention discloses a natural gas hydrate vertical well exploitation system and a natural gas hydrate vertical well exploitation method in a frozen soil area, wherein the natural gas hydrate vertical well exploitation system comprises a first-order deep well pressure pipeline inserted below a natural gas hydrate stability zone and a second-order depressurization pipeline connected with the upper end of the first-order deep well pressure pipeline, and free gas or free bodies below the natural gas hydrate stability zone are discharged along the first-order deep well pressure pipeline and the second-order depressurization pipeline under the high-pressure action to realize depressurization processing of the natural gas hydrate stability zone; the first-order deep well pressure pipeline is connected with a gas production pipe, the lower end of the gas production pipe is provided with a plurality of uniformly distributed gas collecting ports, buffers for relieving the impulse force of decomposed natural gas are arranged in the gas collecting ports, and a port below the first-order deep well pressure pipeline is also used as a gas inlet of the gas production pipe; the power is got to the less pump of this scheme utilization, can realize higher decompression exploitation speed, reduces the gas production pressure of the gas collection mouth of gas production pipe self to improve the security that the natural gas was gathered.
Description
Technical Field
The embodiment of the invention relates to the technical field of natural gas hydrate exploitation, in particular to a vertical well exploitation system and method for natural gas hydrate in a frozen soil area.
Background
According to the exploitation scheme measures of the natural gas hydrate and the actual experience of the current oil gas exploitation, an economic, feasible and environment-friendly exploitation scheme which takes electric energy as power, natural gas decomposed in holes as a circulating medium, mainly reduces pressure, and mainly heats, is integrated with field unmanned, automatic and manual control, and is monitored by remote alarm is provided.
According to the natural gas hydrate accumulation characteristics and geological characteristics in the woodland area, a submersible pump drainage mode is adopted for depressurization exploitation, so that a water layer is kept below a natural gas hydrate layer, the hydrate layer is not stressed by underground water pressure any more, 1, the high-pressure environment is broken, and natural gas is decomposed; 2. after pressure reduction exploitation is completed, decomposed natural gas is used as a circulating medium to be subjected to electromagnetic heating or solar heating, the heated natural gas is conveyed to the bottom of a hole through a booster pump, and a hydrate layer in the hole is heated to accelerate decomposition of a hydrate.
However, the existing natural gas hydrate vertical well exploitation system in the frozen soil region has the following defects:
(1) the pressure of the natural gas hydrate layer is reduced by pumping free gas or other fluids below the natural gas hydrate layer, the balanced storage condition of the natural gas hydrate is broken, and the natural gas hydrate is decomposed, but the existing pressure reduction pipeline is long, so that the problems of unstable pressure reduction work, long pressure reduction time, slow pressure reduction efficiency and high power requirement on a pressure reduction pump are caused;
(2) because the natural gas hydrate is difficult to decompose under the action of the high-pressure environment of the water column, the gas is difficult to escape, after the pressure is released, the gas can volatilize in a well-spraying manner, the safety of the well-sprayed natural gas during gas production is poor, the stability is low, and a gas production pipe is easy to burst under the action of internal and external pressure.
Disclosure of Invention
Therefore, the embodiment of the invention provides a natural gas hydrate vertical well exploitation system and a natural gas hydrate vertical well exploitation method in a frozen soil area, and aims to solve the problems that in the prior art, the pressure reduction work is unstable, the pressure reduction time is long, the pressure reduction efficiency is slow, the safety during gas exploitation is poor, the stability is low, and a gas exploitation pipe is easy to burst under the action of internal and external pressure.
In order to achieve the above object, an embodiment of the present invention provides the following:
a natural gas hydrate vertical well exploitation system in a frozen soil area comprises a first-order deep well pressure pipeline inserted below a natural gas hydrate stable zone and a second-order depressurization pipeline connected with the upper end of the first-order deep well pressure pipeline, wherein the first-order deep well pressure pipeline discharges gas in a pipeline of the first-order deep well pressure pipeline to form a vacuum environment by using a one-way air suction principle, the second-order depressurization pipeline discharges gas in a pipeline of the second-order depressurization pipeline to form a vacuum environment by using a water suction pump, and free gas or free body below the natural gas hydrate stable zone is discharged along the first-order deep well pressure pipeline and the second-order depressurization pipeline under the high pressure effect to realize depressurization processing of the natural gas hydrate stable zone;
the gas collecting device is characterized in that the first-order deep well pressure pipeline is connected with a gas collecting pipe, the lower end of the gas collecting pipe is provided with a plurality of gas collecting ports which are uniformly distributed, a buffer used for relieving the impulse force of decomposed natural gas is arranged in each gas collecting port, and an air port below the first-order deep well pressure pipeline is also used as an air inlet of the gas collecting pipe.
As a preferable scheme of the present invention, an air extraction cylinder is disposed at an upper end of the first-order deep well pressure pipeline, a one-way drawing piston is mounted on a telescopic shaft of the air extraction cylinder, a one-way valve allowing only air to move upwards is disposed below the one-way drawing piston of the first-order deep well pressure pipeline, and a depressurization drawing hole with a filter screen is disposed at a lower end of the first-order deep well pressure pipeline.
As a preferable scheme of the invention, the one-way drawing piston comprises a honeycomb air permeable block and a sealing rubber block wrapped on a side curved surface of the honeycomb air permeable block, a lower concave hole groove is formed in the center of the upper surface of the honeycomb air permeable block, a secondary rubber plate with the height lower than the depth of the lower concave hole groove is arranged inside the lower concave hole groove, the upper surface of the secondary rubber plate is connected with a telescopic shaft of the air exhaust cylinder, the secondary rubber plate penetrates through the center of the honeycomb air permeable block through a connecting rod and is connected with the sealing cup pad, and a rubber pin for blocking an air hole of the honeycomb air permeable block is arranged on the upper surface of the sealing cup pad.
As a preferable scheme of the present invention, a telescopic working range of the pumping cylinder in the first-order deep well pressure pipeline is divided into a decompression telescopic range and a gas production working position, the decompression telescopic range is lower than the gas production working range, a connection position of the second-order decompression pipeline and the first-order deep well pressure pipeline is located at the gas production working position of the pumping cylinder, a connection position of the gas production pipe and the first-order deep well pressure pipeline is located between the decompression telescopic range of the pumping cylinder and the gas production working position, a connection gas port of the second-order decompression pipeline is blocked by the sealing rubber block, and natural gas decomposed by the natural gas hydrate is transferred from the first-order deep well pressure pipeline into the gas production pipe.
As a preferable aspect of the present invention, the connection end of the gas production pipe and the first-order deep well pressure pipeline is also provided with a one-way valve which only allows gas to be transferred from the first-order deep well pressure pipeline to the gas production pipe.
In a preferred embodiment of the present invention, the damper includes a plurality of interconnected conducting airbags installed inside the gas collecting port, two of the conducting airbags are connected to each other by an annular plate, a unidirectional circular plate for controlling the decomposed natural gas to move toward the gas production pipe is hinged to a center position of the annular plate, and volumes of the plurality of conducting airbags sequentially increase from an installation position of the gas collecting port to the inside of the gas production pipe.
In addition, the invention also provides a natural gas hydrate vertical well exploitation method in the permafrost region, which comprises the following steps:
step 100, detecting mechanical operation of the two-step depressurization pipeline and the gas production pipeline, and simultaneously lowering the depressurization pipeline and the gas production pipeline into a vertical well;
200, dividing the double-stage depressurization pipeline into two sections for depressurization work, respectively and sequentially pumping the double-stage depressurization pipeline into a vacuum environment to destroy the high-pressure balance condition of the natural gas hydrate layer, and monitoring the air pressure intensity of the gas production pipe in real time;
step 300, an upper-layer depressurization pipeline of the depressurization pipeline is closed, and decomposed natural gas is dispersed from the lower-layer depressurization pipeline and the gas collection port and enters a gas production pipe;
and 400, storing the natural gas of the gas production pipe into a gas tank through a gas production tree.
As a preferred aspect of the present invention, in step 100, the content of detecting the operation of the dual-step pressure-reducing pipeline and the gas production pipeline mainly includes the air extraction work of the dual-step pressure-reducing pipeline, the sealing effect between the dual-step pressure-reducing pipelines, and the conduction relationship between the lower pressure-reducing pipeline and the gas production pipe.
As a preferred embodiment of the present invention, in step 200, the step of evacuating the internal environment of the dual-step pressure-reducing pipe includes:
step 201, performing high-frequency operation on an upper-layer pressure reduction pipeline in a two-step pressure reduction pipeline, and setting a power source of the upper-layer pressure reduction pipeline as variable-frequency power;
202, when the interior of the upper-layer pressure reduction pipeline is in a vacuum environment, a power source of the lower-layer pressure reduction pipeline in the double-step pressure reduction pipeline works, and gas in the pipeline is pumped into the upper-layer pressure reduction pipeline;
203, adjusting the power source low-frequency work of the upper-layer depressurization pipeline, and monitoring the liquid level height in the lower-layer depressurization pipeline in real time;
and 204, adjusting the high-frequency work of the power source of the upper-layer pressure reduction pipeline until the liquid level is lower than a set value, and closing the power source of the double-step pressure reduction pipeline.
As a preferred scheme of the present invention, the power source of the lower depressurization pipeline is divided into a depressurization operating range and a gas production operating position, when the power source of the lower depressurization pipeline is in the depressurization operating range, the free matter of the natural gas hydrate layer enters the upper depressurization pipeline from the inside of the lower depressurization pipeline, and when the power source of the lower depressurization pipeline is in the depressurization operating range, the natural gas decomposed by the natural gas hydrate enters the upper depressurization pipeline from the lower depressurization pipeline.
The embodiment of the invention has the following advantages:
(1) in order to improve the depressurization speed of a natural gas hydrate reservoir and reduce the depressurization energy consumption and the working pressure of a depressurization power source, a depressurization pipeline is divided into two-stage pipelines, the depressurization power source is installed in each pipeline, the two-stage pipelines are firstly extracted into a vacuum environment, and free gas or other fluids below a natural gas hydrate layer enter the pipelines under the high-pressure action of a storage layer after each pipeline is gradually adjusted to the vacuum environment due to the fact that the free gas or other fluids exist below the natural gas hydrate layer, so that the high depressurization exploitation speed can be realized by using small pumping power;
(2) the inlet position of the gas production pipe is divided into the gas collecting port and the connecting position of the first-order deep well pressure pipeline and the gas production pipe, so that the decomposed natural gas realizes a certain buffering effect in the first-order deep well pressure pipeline, the gas production pressure of the gas collecting port of the gas production pipe is reduced, and the safety of natural gas collection is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.
FIG. 1 is a schematic side sectional view of a vertical well development system according to an embodiment of the present invention;
FIG. 2 is a schematic structural view of a gas production pipe according to an embodiment of the present invention;
FIG. 3 is a schematic structural view of a one-way withdrawal piston according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a buffer according to an embodiment of the present invention.
In the figure:
1-first order deep well pressure pipe; 2-second order depressurization line; 3, a water pump; 4-gas production pipe; 5-an air collecting port; 6-a buffer; 7-an air exhaust cylinder; 8-one-way drawing piston; 9-one-way valve; 10-a reduced pressure extraction well;
601-conducting the airbag; 602-an annular plate; 603-one-way round plate;
801-honeycomb air permeable block; 802-sealing rubber block; 803-lower concave hole groove; 804-secondary rubber plate; 805-sealing the cup pad; 806-rubber pins; 807-connecting rod.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, in order to increase the depressurization speed of a natural gas hydrate reservoir and reduce the depressurization energy consumption and the working pressure of a depressurization power source, the depressurization pipeline is divided into two-stage pipelines, the depressurization power source is installed in each pipeline, the two-stage pipelines are firstly pumped into a vacuum environment, and after each pipeline is gradually adjusted to the vacuum environment due to the existence of free gas or other fluids below the natural gas hydrate reservoir, the free gas or other fluids below the natural gas hydrate reservoir enter the pipeline under the high pressure action of the reservoir, so that a higher depressurization exploitation speed can be realized by using a smaller pumping power.
After the pressure is reduced, the natural gas hydrate layer is not influenced by the static pressure of the underground water, the balance condition of the natural gas hydrate layer is destroyed, the hydrate begins to be decomposed and released, and the pressure reduction speed is improved along with the release of the natural gas and the continuous rising of the natural gas hydrate layer in the exploitation casing to the surface acquisition device compared with the operation of utilizing a first-order submersible pump to discharge the underground water in the prior art, so that the natural gas exploitation speed is improved.
Specifically including inserting first-order deep well pipeline 1 below the natural gas hydrate stability is taken, and with second order depressurization pipeline 2 that 1 upper end of first-order deep well pipeline is connected, first-order deep well pipeline 1 utilizes one-way air exhaust principle to form vacuum environment with the interior gas outgoing of the pipeline of first-order deep well pipeline 1, second order depressurization pipeline 2 utilizes suction pump 3 to form vacuum environment with the interior gas outgoing of the pipeline of second order depressurization pipeline 2, free gas or the free body of natural gas hydrate stability area below along under the high pressure action first-order deep well pipeline 1 with second order depressurization pipeline 2 discharges and realizes right the step-down of natural gas hydrate stability area is handled.
The natural gas hydrate is the ice-like crystalline substance formed by natural gas and water under the conditions of high pressure and low temperature, so the pressure of a natural gas hydrate stable zone is large, the depressurization mode of the prior art to the natural gas hydrate stable zone is mostly that submersible pumps are put down in a drilling well, underground water is discharged by starting the submersible pumps, and the liquid level is lower than a natural gas hydrate stable layer.
The pumping mode is divided into an upper section and a lower section in the embodiment, the first-order deep well pressure pipeline 1 pumps the underground water to the upper end of the first-order deep well pressure pipeline 1 by adopting a one-way pumping principle, and the second-order depressurization pipeline 2 pumps the underground water at the upper end of the first-order deep well pressure pipeline 1 to the ground by adopting a water pump, so that the power working ranges of the first-order deep well pressure pipeline 1 and the second-order depressurization pipeline 2 in the embodiment are slightly larger than the heights of the pipelines, the negative pressure environments of the two depressurization pipelines are stable, the depressurization work is stable and high in efficiency, and the natural gas exploitation time is relatively shortened.
As shown in fig. 2, the first-order deep well pressure pipeline 1 is connected with a gas production pipe 4, the lower end of the gas production pipe 4 is provided with a plurality of uniformly distributed gas collection ports 5, a buffer 6 for relieving the impulse force of decomposed natural gas is arranged in each gas collection port 5, and a through hole below the first-order deep well pressure pipeline 1 is also used as a gas inlet of the gas production pipe 4.
As is well known, the decompression mining method is a mining method for promoting the decomposition of natural gas hydrate by reducing pressure, natural gas is difficult to escape due to the pressure of underground water in a natural gas hydrate stabilizing zone, and after the underground water is pumped out, the pressure is released, and the natural gas can volatilize in a well-spraying manner, so that the stability of natural gas collection is improved and the pressure of 4 gas production pipes is relieved in order to avoid a well blowout phenomenon, in the embodiment, the inlet position of the gas production pipe 4 is divided into a gas collecting port and the connecting position of the first-order deep well pressure pipeline 1 and the gas production pipe 4, so that the decomposed natural gas realizes a certain buffering effect in the first-order deep well pressure pipeline 1, the gas production pressure of the gas collecting port 5 of the gas production pipe 4 is reduced, and the safety of natural gas collection is improved.
In addition, the surface device connected with the second-order depressurization pipeline 2 and the ground gas collecting device connected with the gas production pipe 4 both use the processing mode in the prior art, and the surface device is not the main improvement direction of the embodiment, so the description is omitted.
The operating principle of the double-step pressure reduction pipeline is described in detail below, the upper end of the first-step deep well pressure pipeline 1 is provided with an air exhaust cylinder 7, a one-way drawing piston 8 is installed on a telescopic shaft of the air exhaust cylinder 7, the first-step deep well pressure pipeline 1 is provided with a one-way valve 9 which only allows air to move upwards and is arranged below the one-way drawing piston 8, and the lower end of the first-step deep well pressure pipeline 1 is provided with a pressure reduction extraction hole 10 with a filter screen.
As shown in fig. 1 and 3, the one-way drawing piston 8 includes a honeycomb air permeable block 801 and a sealing rubber block 802 wrapped on the side curved surface of the honeycomb air permeable block 801, the center of the upper surface of the honeycomb air permeable block 801 is provided with a lower concave groove 803, a secondary rubber plate 804 with a height lower than the depth of the lower concave groove 803 is arranged inside the lower concave groove 803, the upper surface of the secondary rubber plate 804 is connected with the telescopic shaft of the air suction cylinder 7, the secondary rubber plate 804 passes through the center of the honeycomb air permeable block 802 through a connecting rod 807 and is connected with a sealing cup 805, and the upper surface of the sealing cup 805 is provided with a rubber pin 806 for plugging the air hole of the honeycomb air permeable block 801.
It should be particularly noted that the first-order deep well pressure pipeline 1 performs depressurization treatment on the natural gas hydrate stability zone by using the pumping cylinder 7, and is mainly used for adapting to a narrow space inside a drilling well and facilitating the control system on the ground to regulate and control the work of the pumping cylinder 7.
Wherein, the operating principle of first order deep well pipeline under pressure 1 does: the working principle of the first-order deep well pressure pipeline 1 is basically similar to that of a pressurized water well, when the air pumping cylinder 7 pulls the one-way drawing piston 8 to draw upwards, the one-way valve 9 is opened, the one-way drawing piston 8 is sealed, so that the gas below the one-way valve 9 moves upwards, when the air pumping cylinder 7 pushes the one-way drawing piston 8 to move downwards, the one-way valve 9 is closed, the one-way drawing piston 8 is opened, the air is ejected from the inside of the piston, and the gas is discharged to the ground under the drawing force of the second-order pressure reducing pipeline 2. The circulation is performed to vacuumize the lower pipe, and free gas or free water below the natural gas hydrate stable layer is pumped out under the action of the atmospheric pressure of the reservoir.
That is to say, this kind of mode not only through power extraction free water or free gas realization depressurization treatment, has still utilized the high pressure environment of natural gas hydrate reservoir simultaneously, accelerates the extraction speed of free water or free gas through the atmospheric pressure difference, has consequently also realized accelerating depressurization speed, improves the effect of natural gas hydrate decomposition speed.
It should be further explained that the sealing and venting operation of the one-way drawing piston 8 is implemented in particular by: when the air pumping cylinder 7 pulls the one-way drawing piston 8 to draw upwards, the connecting rod 807 is lifted, the sealing cup mat 805 moves upwards under the action of pulling force, the rubber pin 806 on the upper surface of the sealing cup mat 805 is correspondingly inserted into the air hole of the honeycomb air permeable block 801, the honeycomb air permeable block 801 is blocked, the one-way drawing piston 8 at the moment realizes sealing work, the upper gas body at the lower end of the one-order deep well pressure pipeline 1 is accelerated, and the vacuum environment of the one-order deep well pressure pipeline 1 is realized.
When the air extracting cylinder 7 pushes down the one-way drawing piston 8 to integrally move downwards, the connecting rod 807 is pushed down, the sealing cup mat 805 moves downwards under the action of thrust, the rubber pins 806 on the upper surface of the sealing cup mat 805 are correspondingly drawn out from the air holes of the honeycomb air permeable block 801, the honeycomb air permeable block 801 is opened, the one-way drawing piston 8 at the moment realizes air permeability work, and air in the first-order deep well pressure pipeline 1 is discharged into the second-order pressure reducing pipeline 2.
After free gas or free water below the natural gas hydrate stable layer is extracted, the liquid level of the natural gas hydrate stable layer is lowered, the high-pressure environment of the reservoir of the natural gas hydrate is damaged, the natural gas hydrate is decomposed, and at the moment, the released natural gas is required to be transferred to an earth surface acquisition device by using the gas production pipe 4.
According to the above, when gas production works, the air pumping cylinder 7 and the water pump 3 stop working, and the first-order deep well pressure pipeline 1 is used as a gas collection inlet, so that the telescopic working range of the air pumping cylinder 7 in the first-order deep well pressure pipeline 1 is divided into a decompression telescopic range and a gas production working position.
The pressure reduction telescopic range is smaller than the gas production working range, the connecting positions of the second-order pressure reduction pipeline 2 and the first-order deep well pressure pipeline 1 are both located at the gas production working position of the air exhaust cylinder 7, and the connecting position of the gas production pipe 4 and the first-order deep well pressure pipeline 1 is located between the pressure reduction telescopic range and the gas production working position of the air exhaust cylinder 7.
The connecting end of the gas production pipe 4 and the first-order deep well pressure pipeline 1 is also provided with a one-way valve 9 which only allows gas to be transferred from the first-order deep well pressure pipeline 1 to the gas production pipe 4.
Therefore, when the first-order deep well pressure pipeline 1 works at the pressure reduction, the air exhaust cylinder 7 drives the one-way drawing piston 8 to draw up and down in the pressure reduction telescopic range, and due to the work of the water suction pump 3 of the second-order pressure reduction pipeline 2, free air and free water pumped out from the first-order deep well pressure pipeline 1 are transferred into the second-order pressure reduction pipeline 2 through the first-order deep well pressure pipeline 1 according to the negative pressure working principle.
When the first-order deep well pressure pipeline 1 is in the gas production working range, the air pumping cylinder 7 pulls the one-way drawing piston 8 to move upwards to the gas production working range, the sealing rubber block 805 plugs the connecting air port of the second-order pressure reduction pipeline 2, and the natural gas decomposed by the natural gas hydrate is transferred into the gas production pipe 4 from the first-order deep well pressure pipeline 1.
Therefore, the first-order deep well pressure pipeline 1 of the embodiment not only serves as a medium for pressure reduction work, but also serves as a medium for a gas collection inlet of gas production, so that the working pressure of the gas collection port 5 of the gas production pipe 4 can be reduced, the blowout phenomenon at the initial stage of natural gas production is prevented, and the safety and the stability of natural gas collection are improved.
As shown in fig. 2 and 4, the damper 6 includes a plurality of interconnected conducting airbags 601 installed inside the gas collecting port 5, two of the conducting airbags 601 are connected by an annular plate 602, a one-way circular plate 603 for controlling the decomposed natural gas to move toward the gas production pipe 4 is hinged to a center position of the annular plate 602, and the volumes of the plurality of conducting airbags 601 are sequentially increased from the installation position with the gas collecting port 5 to the inside of the gas production pipe 4.
The opening angle of the one-way circular plate 603 is related to the internal air pressure of the single communicating air bag 601, when the internal air pressure of the single communicating air bag 601 is larger, the opening angle of the one-way circular plate 603 is correspondingly increased so as to avoid the single communicating air bag 601 from bursting due to over-large volume expansion, and when the decomposition amount of natural gas is reduced, gas can be collected through the first-order deep well pressure pipeline 1.
This embodiment has still adopted the mode of buffering gasbag to reduce the flow pressure that the natural gas was mined, and the natural gas that the decompression decomposes gets into gas production pipe 4 from gas collection mouth 5, will descend the packing of every conducting airbag 601 in proper order earlier and swell, then moves to ground collection system along gas production pipe 4 upward again, has consequently played the effect of buffering blowout phenomenon.
In addition, based on the natural gas hydrate vertical well exploitation system, the invention also provides a natural gas hydrate vertical well exploitation method in the frozen soil area, which comprises the following steps:
and 100, detecting the mechanical operation of the two-stage depressurization pipeline and the gas production pipeline, and simultaneously lowering the depressurization pipeline and the gas production pipeline into a vertical well.
Detect two-step depressurization pipeline and gas production pipeline moving content mainly include the work of bleeding of two-step depressurization pipeline, the sealed effect between the two-step depressurization pipeline and the relation of switching on between lower floor's depressurization pipeline and the gas production pipe to ensure the steady operation of depressurization work and gas production work, because the depressurization pipeline with connect through the gas production pipeline between the gas production pipeline, consequently the depressurization pipeline with the gas production pipeline need be transferred simultaneously in the straight well.
And 200, dividing the double-stage depressurization pipeline into two sections for depressurization work, respectively and sequentially pumping the double-stage depressurization pipeline into a vacuum environment to destroy the high-pressure balance condition of the natural gas hydrate layer, and monitoring the air pressure intensity of the gas production pipe in real time.
In this step, the step of evacuating the internal environment of the dual-stage depressurization pipe is implemented by:
step 201, performing high-frequency operation on an upper-layer pressure reduction pipeline in a two-step pressure reduction pipeline, and setting a power source of the upper-layer pressure reduction pipeline as variable-frequency power;
step 202, when the interior of the upper-layer depressurization pipeline is in a vacuum environment, the power source of the lower-layer depressurization pipeline in the double-step depressurization pipeline works to pump the gas in the pipeline into the upper-layer depressurization pipeline.
And 203, adjusting the power source low-frequency work of the upper-layer depressurization pipeline, and monitoring the liquid level height in the lower-layer depressurization pipeline in real time.
After will last layer step-down pipeline takes out to the vacuum earlier, when the air rebound of lower floor's step-down pipeline extraction, the air of lower floor's step-down pipeline is because atmospheric pressure difference automatic transfer to last layer step-down pipeline, consequently when reducing the operating pressure of the power supply of upper layer step-down pipeline, has also improved the efficiency that the step-down was gathered.
And 204, adjusting the high-frequency work of the power source of the upper-layer pressure reduction pipeline until the liquid level is lower than a set value, and closing the power source of the double-step pressure reduction pipeline.
When the liquid level height issued by the natural gas hydrate is smaller than the set value, the working safety of the power source is improved in order to avoid the idling of the power source of the upper-layer depressurization pipeline.
And step 300, closing the upper-layer depressurization pipeline of the depressurization pipeline, and dispersing the decomposed natural gas into the gas production pipe from the lower-layer depressurization pipeline and the gas collection port.
The power supply of lower floor's step-down pipeline divide into step-down working range and gas production operating position, when the power supply of lower floor's step-down pipeline is in step-down working range, the free on natural gas hydrate layer by get into in the lower floor's step-down pipeline upper strata step-down pipeline, when the power supply of lower floor's step-down pipeline is in step-down working range, the natural gas that natural gas hydrate decomposes gets into by lower floor's step-down pipeline upper strata step-down pipeline.
And 400, storing the natural gas of the gas production pipe into a gas tank through a gas production tree.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (10)
1. A natural gas hydrate vertical well exploitation system in a frozen soil area is characterized by comprising a first-order deep well pressure pipeline (1) inserted below a natural gas hydrate stability zone, and a second-order pressure reduction pipeline (2) connected with the upper end of the first-order deep well pressure pipeline (1), the first-order deep well pressure pipeline (1) utilizes the one-way air extraction principle to discharge the gas in the first-order deep well pressure pipeline (1) to form a vacuum environment, the second-order pressure reduction pipeline (2) utilizes the water suction pump (3) to discharge the gas in the second-order pressure reduction pipeline (2) to form a vacuum environment, free gas or free body below the natural gas hydrate stability zone is discharged along the first-order deep well pressure pipeline (1) and the second-order depressurization pipeline (2) under the action of high pressure to realize depressurization treatment of the natural gas hydrate stability zone;
the gas production system is characterized in that the first-order deep well pressure pipeline (1) is connected with a gas production pipe (4), the lower end of the gas production pipe (4) is provided with a plurality of gas collection ports (5) which are uniformly distributed, a buffer (6) used for relieving the impulse force of decomposed natural gas is arranged in each gas collection port (5), and a through opening below the first-order deep well pressure pipeline (1) is also used as a gas inlet of the gas production pipe (4).
2. The frozen soil area natural gas hydrate vertical well exploitation system according to claim 1, wherein an air extraction cylinder (7) is arranged at an upper end of the first-order deep well pressure pipeline (1), a one-way drawing piston (8) is installed on a telescopic shaft of the air extraction cylinder (7), a one-way valve (9) allowing only gas to move upwards is arranged below the one-way drawing piston (8) of the first-order deep well pressure pipeline (1), and a depressurization extraction hole (10) with a filter screen is arranged at a lower end of the first-order deep well pressure pipeline (1).
3. The natural gas hydrate vertical well exploitation system for a frozen soil region according to claim 2, the one-way drawing piston (8) comprises a honeycomb air permeable block (801) and a sealing rubber block (802) wrapped on the side curved surface of the honeycomb air permeable block (801), the center of the upper surface of the honeycomb air permeable block (801) is provided with a lower concave groove (803), a secondary rubber plate (804) with the height lower than the depth of the lower concave groove (803) is arranged in the lower concave groove (803), the upper surface of the secondary rubber plate (804) is connected with the telescopic shaft of the air exhaust cylinder (7), the secondary rubber plate (804) penetrates through the center of the honeycomb air-permeable block (802) through a connecting rod (807) to be connected with the sealing cup gasket (805), the upper surface of the sealing cup mat (805) is provided with a rubber pin (806) for plugging the air hole of the honeycomb air permeable block (801).
4. The natural gas hydrate vertical well exploitation system according to claim 3, wherein, the telescopic working range of the air pumping cylinder (7) in the first-order deep well pressure pipeline (1) is divided into a decompression telescopic range and a gas production working position, the decompression telescopic range is lower than the gas production working range, and the connection positions of the second-order pressure reduction pipeline (2) and the first-order deep well pressure pipeline (1) are both positioned at the gas production working position of the air extraction cylinder (7), the connecting position of the gas production pipe (4) and the first-order deep well pressure pipeline (1) is positioned between the decompression expansion range of the gas extraction cylinder (7) and the gas production working position, the sealing rubber block (805) blocks the connecting air port of the second-order pressure reduction pipeline (2), and transferring the natural gas decomposed by the natural gas hydrate from the first-order deep well pressure pipeline (1) into the gas production pipe (4).
5. The frozen soil region natural gas hydrate vertical well exploitation system according to claim 4, wherein the connection end of the gas exploitation pipe (4) and the first-order deep well pressure pipeline (1) is also provided with a one-way valve (9) which only allows gas to transfer from the first-order deep well pressure pipeline (1) to the gas exploitation pipe (4).
6. The frozen soil area natural gas hydrate vertical well exploitation system according to claim 5, wherein the buffer (6) comprises a plurality of interconnected conducting airbags (601) installed inside the gas collection port (5), two conducting airbags (601) are connected through an annular plate (602), a one-way circular plate (603) for controlling decomposed natural gas to move towards the gas exploitation pipe (4) is hinged to a center position of the annular plate (602), and the volumes of the plurality of conducting airbags (601) sequentially increase from an installation position of the gas collection port (5) to the inside of the gas exploitation pipe (4).
7. A natural gas hydrate vertical well exploitation method for a frozen soil area is applied to the natural gas hydrate vertical well exploitation system for the frozen soil area according to any one of claims 1 to 6, and is characterized by comprising the following steps:
step 100, detecting mechanical operation of the two-step depressurization pipeline and the gas production pipeline, and simultaneously lowering the depressurization pipeline and the gas production pipeline into a vertical well;
200, dividing the double-stage depressurization pipeline into two sections for depressurization work, respectively and sequentially pumping the double-stage depressurization pipeline into a vacuum environment to destroy the high-pressure balance condition of the natural gas hydrate layer, and monitoring the air pressure intensity of the gas production pipe in real time;
step 300, an upper-layer depressurization pipeline of the depressurization pipeline is closed, and decomposed natural gas is dispersed from the lower-layer depressurization pipeline and the gas collection port and enters a gas production pipe;
and 400, storing the natural gas of the gas production pipe into a gas tank through a gas production tree.
8. The method for exploiting natural gas hydrates in the frozen soil region according to claim 7, wherein in step 100, the content of detecting the operation of the two-step depressurization pipeline and the gas production pipeline mainly comprises the air pumping work of the two-step depressurization pipeline, the sealing effect between the two-step depressurization pipeline and the conduction relationship between the lower depressurization pipeline and the gas production pipe.
9. The frozen soil region natural gas hydrate vertical well exploitation method according to claim 7, wherein in the step 200, the step of vacuumizing the internal environment of the double-step depressurization pipeline is realized by:
step 201, performing high-frequency operation on an upper-layer pressure reduction pipeline in a two-step pressure reduction pipeline, and setting a power source of the upper-layer pressure reduction pipeline as variable-frequency power;
202, when the interior of the upper-layer pressure reduction pipeline is in a vacuum environment, a power source of the lower-layer pressure reduction pipeline in the double-step pressure reduction pipeline works, and gas in the pipeline is pumped into the upper-layer pressure reduction pipeline;
203, adjusting the power source low-frequency work of the upper-layer depressurization pipeline, and monitoring the liquid level height in the lower-layer depressurization pipeline in real time;
and 204, adjusting the high-frequency work of the power source of the upper-layer pressure reduction pipeline until the liquid level is lower than a set value, and closing the power source of the double-step pressure reduction pipeline.
10. The vertical well exploitation method of natural gas hydrate in the frozen soil region according to claim 7, wherein a power source of the lower depressurization pipeline is divided into a depressurization working range and a gas exploitation working position, when the power source of the lower depressurization pipeline is in the depressurization working range, a free matter of the natural gas hydrate layer enters the upper depressurization pipeline from the inside of the lower depressurization pipeline, and when the power source of the lower depressurization pipeline is in the depressurization working range, natural gas decomposed by the natural gas hydrate enters the upper depressurization pipeline from the lower depressurization pipeline.
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