Technical Field
[0001] The present invention relates to the technical field of coal resource development,
particularly relates to a gas injection apparatus with controllable gas injection
point, gas injection process and gasification method.
Background Art
[0002] Shaftless underground gasification technologies mainly employ the directional drilling
and reverse burning to construct gasification channel, and inject gasification agents
such as air and oxygen/steam to conduct underground gasification to produce coal gas.
Its advantage lies in that gas production of single gasifier is large. Its disadvantage
lies in that position of burning zone is not stable, loss rate of the gas is high,
and it is necessary to add auxiliary boreholes if the gasification channel is very
long.
[0003] To solve the problems above, Lawrence Livermore national laboratory in USA has developed
controlled retraction injection point (CRIP), which makes the injection point retract
to form new burning zone by burning a section of the casing-tube so that the injection
point can move towards the gas injection well, as shown in figure 1. The igniter has
many pipes, which can carry fluid from ground to the underground. Start the igniter,
the silane from one pipe encountered in the air will cause spontaneous combustion,
the spark will ignite propane from another pipe, and the flame will burn off a section
of the casing-tube and further ignite the coal seam. In Thulin, Belgium, the underground
gasification test designs that the injection tube employs concentric annular tubes,
wherein the center tube can move within the annular tube. There are three thermocouple
electric wires and two combustible hollow pipes in the center tube. One hollow pipe
is used for delivering triethylborine, which will burn once meets air, and CH
4. The other hollow pipe is filled with oxygen. An igniter is fixed at the end of the
center tube.
[0004] The advantage of CRIP technology is that the gasification process can be effectively
controlled, while its disadvantage is that this technology requires multiple ignitions
to ignite the coal seam at different distance location within a directional well before
gasification. Because the gas injection point movement is discontinuous, the gasification
is unstable, and the apparatus for ignition and gas injection has complicated structure
and is expensive, the ignition process is complicated, difficult to control and not
safe enough.
Summary of the Invention
[0005] Aiming to solve a series of problem of existing CRIP process in the shaftless underground
coal gasification including multiple ignition, complicated device, discontinuous gas
injection point movement and unstable gasification process, the present invention
provides a reverse burning ignition and gasification method of controllable gas injection
point movement of shaftless underground gasification, thereby achieving the goal of
improving gasification stable control and safety performance and reducing the production
cost. The present invention also provides a gas injection apparatus and a gas injection
process with controllable gas injection point.
[0006] The present invention is based on the techniques of directional drilling and coiled
tubing, utilizes the principle of directional drilling cooperating with coiled tubing
to realize the movement of gas injection point and adjusting gasification agent injection
parameter to control the reverse combustion, finally achieves the goal of modulating
movement and burning rate of flame working face position to conduct reverse burning
ignition and gasification of the underground coal seam.
[0007] To achieve this goal, the present invention employs the following technical solutions:
One goal of the present invention is to provide a gas injection apparatus with controllable
gas injection point. The gas injection apparatus comprises a directional well channel.
The directional well channel is disposed with coiled tubing. The coiled tubing is
connected with oxygen/oxygen-enriched gas line. The annular space between the coiled
tubing and the directional well has connection to an auxiliary gasfication agent line
and a steam line. The start end of the coiled tubing is disposed with gas injector
head and the terminal end is disposed with a nozzle.
[0008] The coiled tubing is sealed by a blowout preventer (box) and placed in the well.
[0009] The second goal of the present invention is to provide a gas injection process with
controllable gas injection point. In the gas injection process, the oxygen/oxygen-enriched
gas is delivered by the coiled tubing deposited within the directional well channel.
The oxygen/oxygen-enriched gas, and the auxiliary gasification agent delivered through
the annular space between the coiled tubing and the directional well will be uniformly
mixed at the nozzle location at the terminal end of coiled tubing. The mixed gasification
agent enters the predetermined gasification location of the coal seam through the
directional well channel or the pore channels within the coal seam.
[0010] The oxygen/oxygen-enriched gas and auxiliary gasification agent are mixed at the
position of nozzle at the terminal end of the coiled tubing, that is, within the drill-hole
or the channel.
[0011] The gas injection point movement control of the present invention during the gas
injection, can realize gas injection position change by lifting and lowering action
to control movement of the coiler tubing and nozzle.
[0012] The directional well channel of the present invention is formed with directional
drilling method. Directional drilling technology is one of the most advanced well
drilling technologies in the field of petroleum exploration and development in the
current time. It is a well-drilling process technology that utilizes special under-well
tools, measurement devices and process technology to effectively control the well
trajectory, making drilling bit drill to the predetermined underground position along
a specific direction. It is widely used in oilfield development in current. Directional
drilling technology can economically and effectively develop petroleum resources with
limited ground and underground conditions and greatly improve petroleum production
and reduce well-drilling cost, thus it is good to natural circumstance protection
and has significant economical and social benefit.
[0013] The directional drilling method of the present invention preferably employ any one
of directional well drilling technology, horizontal well drilling technology, lateral
drilling technology, radial horizontal well technology, multilateral well technology,
cluster wells technology and extended reach well technology in petroleum or coal seam
gas drilling technologies. The directional well channel is longer than 10 meters.
[0014] The directional well channel of the present invention is unsupported channel or supported
channel. In practical implementation process, whether supporting the channel or not
is determined according to the factors such as coal rock and geological condition.
[0015] The supported channel utilizes sieve-tube support and/or casing-tube support, preferably
sieve-tube support or the combination of sieve-tube support and casing-tube support.
In the practical implementation process, different support pattern can be selected
according to the factors that influence reverses burning ignition speed, such as support
tube intensity, coal gangue and coal water. Preferably, sieve-tube support or combination
of sieve-tube support and casing-tube support is employed to improve the contact area
of gasification agent and coal seam to be ignited.
[0016] The support tube materials are combustible materials, more preferably organic materials,
most preferably glass fiber reinforced plastics or PE pipe materials. During the implementation
process, organic materials such as glass fiber reinforced plastics or PE pipe materials
are preferred due to factors such as intensity or burning features.
[0017] The oxygen/oxygen-enriched gas is provided by the gasification agent preparation
system. The oxygen-enriched gas is a mixed gas composed of oxygen and one or both
of nitrogen and carbon dioxide, wherein the concentration by volume of oxygen is larger
than 21%.
[0018] The auxiliary gasification agent is one of nitrogen, carbon dioxide and water, or
mixture thereof. A person skilled in the art can select one or two of the gases according
to the gas injection requirement. The nitrogen is provided by a nitrogen production
device. The carbon dioxide is provided by a decarbonization device. The auxiliary
gasification agent has the following functions: firstly, it will take part in the
underground gasification reduction reaction, such as CO
2 or H
2O; secondly, its remixing with oxygen/oxygen-enriched gas can reduce the oxygen concentration
of the mixed gasification agent, thereby protecting gasification process and equipment.
[0019] During gasification process, the oxygen content of the auxiliary gasification agent
delivered between the coiled tubing and directional well wall should be controlled
to prevent self-burning of coal seam or gas injection string tempering in the delivery
process. The oxygen concentration is determined by the lower limit of oxygen concentration
which can cause the coal self-burning. For the thickness of loose coal seam is less
than 0.5 meter, the oxygen concentration by volume of the auxiliary gasification agent
is generally required to be less than 5%.
[0020] For the coiled tubing and nozzle of the present invention can select the formed materials
and equipment of the current petroleum and natural gas industry. In coiled tubing
selection, the processing parameters such as oxygen concentration, pressure and flow
rate of delivered gasification agent are key factors to be considered; the coiled
tube with different pressure, material and diameter can be selected to reduce the
composite cost.
[0021] The pore channels within the coal seam is formed by artificial drilling or fracturing
process, or formed by coal seam under thermal effect of burning.
[0022] The third goal of the present invention is to provide two controlled gas injection
point gasification method utilizing the above-mentioned gas injection process.
[0023] The first controlled gas injection point gasification method conducts reverse burning,
gasification channel processing and gasification production by segmentally moving
the coiled tubing to make the gas injection point segmentally move to the predetermined
gasification position, and then adjusting the gas injection technology parameters.
[0024] The gasification method comprises the following steps:
- 1) according to the parameters such as thickness and reserves of gasifiable coal seam
in gasification area, segmentally moving coiled tubing according to the gas injection
process to make the gas injection point position segmentally move to the predetermined
gasification position;
- 2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; segmentally moving the flame working face to the predetermined gasification
position in the manner of reverse burning and making gasification channel process
at the same time;
- 3) after completing the ignition and process of the gasification channel, improving
intensity of the gasification agent injection, enhancing the gasification of underground
coal and conducting gas production of underground gasification on a large scale;
- 4) when the coal seam gasification of the predetermined gasification position is done,
determining stopping or reducing gasification agent injection according to the consumed
amount of the gasification coal, and heat value and composition of coal gas, and starting
the injector head to move the oxygen/oxygen-enriched gas injection point to the next
predetermined gasification position;
- 5) conducting the next segment gasification channel process according to step 2),
and completing the underground gasification of the predetermined coal seam area according
to step 3) and 4); repeating those steps until the coal resource around the directional
well channel is gasified completely.
[0025] The gas injection point segmental movement distance in the step 1) is 10∼150m.
[0026] Preferably, the gasification flow rate during the gasification channel ignition and
processing is limited within 300-3000 m
3/h.
[0027] Preferably, the oxygen concentration by volume in the gasification agent is 21∼55%.
[0028] In the present invention, the gas injection movement is estimated according to the
parameters such as the amount of coal has gasified, the heat value and composition
of coal gas. The movement standard determined by general process operation is as follows:
the amount of coal has gasified is more than 50% of the total gasifiable coal in the
section of directional well channel; and the heat value and composition of the production
gas reduce by more than 20% compared with normal value.
[0029] Another controllable gas injection point gasification method provided by the present
invention conducted reverse burning, gasification channel processing and gasification
production by continuously or intermittently lifting the coiled tubing to make the
gas injection point continuously move to the predetermined gasification position,
and then adjusting the gas injection technology parameters.
[0030] The gasification method comprises the following steps:
- 1) according to the parameters such as thickness and reserves of gasifiable coal seam
in gasification area, and continuously or intermittently lifting coiled tubing to
make the gas injection point continuously move to the predetermined gasification position;
- 2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; achieving continuously processing gasification channel and underground gasification
production on a large scale in a manner of reverse burning;
- 3) adjusting the gasification agent injection parameters whenever necessary, to guarantee
relative stable status of coal gas composition and heat value;
- 4) when coal seam gasification of the predetermined gasification position is done,
controlling reverse movement speed of coiled tubing according to burning speed of
the coal gasification, heat value and composition of coal gas, and the gasifiable
coal reserves, until the coal resource around the directional well channel is gasified
completely.
[0031] The flow rate of the gasification agent in the step 2) is larger than 2000 m
3/h; preferably, the oxygen concentration by volume of gasification agent is 21∼95%.
[0032] Preferably, when the oxygen concentration by volume is larger than 60%, water steam
or water can be injected to adjust the temperature and gas quality in the cavity.
[0033] The movement speed of the gas injection point is determined according to the amount
of coal burned per unit of time (m), heat value and composition fluctuation of coal
gas. In the practical operation of underground gasification, the movement standard
determined by process operation is as follows: the gas injection point can begin to
continuously move till the gasification rate (η) is larger than 50%, which is the
ratio of coal burned to the gasifiable coal (T) per unit length of the directional
well channel. and the reduction of heat value and composition is more than 20% of
normal value, wherein the gas injection point movement rate (V) control satisfies
the following equation: V= T*η/m.
[0034] The controllable gas injection point gasification method of the present invention
includes the following steps:
- 1) employing directional drilling technology to build up a directional well channel
connecting to the existing burn zone in the predetermined gasification coal seam;
- 2) delivering the coiled tubing and the nozzle to the predetermined gasification position
along the directional well through the gas injection well using the injector head;
- 3) injecting the auxiliary gasification agent into the annular space between the coiled
tubing and the directional well wall to conduct replacement protection of the channel,
and then injecting oxygen/oxygen-enriched gas into the coiled tubing;
- 4) delivering the oxygen/oxygen-enriched gas through the coiled tubing to output at
the nozzle, allowing its uniform mixture with the auxiliary gasification agent delivered
through the annular space at the predetermined gasification position; mixed gasification
agent enters the predetermined ignition position through the directional well channel
or the pore channel within the coal seam;
- 5) adjusting pressure and flow rate of a single gas and controlling the parameters
such as pressure, flow rate and oxygen concentration of the mixed gasification agent
injected into the gasifier by the ground control system; segmentally guiding the flame
working face move to the predetermined gasification position in the manner of reverse
burning; at the same time, processing the gasification channel and making underground
gasifier to produce syngas;
- 6) determining the condition of coal seam burning and gasification at the predetermined
gasification position according to the coal burned, the heat value and composition
of coal gas; when the stability of the heat value and composition decrease, starting
the injector head to make the oxygen injection point move to the next predetermined
gasification position;
- 7) accomplishing the coal underground gasification in the predetermined area according
to the steps 5) and 6); repeating those steps until the coal resource around the directional
well channel is gasified completely; and
- 8) stopping oxygen/oxygen-enriched gas input of the coiled tubing, then stopping auxiliary
gasification agent input of the annular space of sieve-tube; taking out the gasification
agent injection apparatus from the directional well channel and moving it to the next
gasification area.
[0035] Compared with the existing technical solutions, the gas injection apparatus of the
present invention employs directional drilling and coil tubing technologies so that
it can control the movement of the gas injection position and can stably adjust the
gasification agent injection parameters.
[0036] In the gas injection process of the present invention, the gas injection point being
able to move in any distance within the directional well channel according to requirement,
and effectively improve gasification recycling rate of the coal along the directional
well channel. Besides, employing annular space between the coiled tubing and the directional
well wall to deliver auxiliary gasification agent can effectively prevent channel
coal self-burning and gas injection tube backfire, can form mixed gasification agent
at the gas injection point ( nozzle position), and can continuously controlling various
gas injection parameters.
[0037] In the implementation process of the present invention, there is no need igniter
at gas injection point to ignite, whereas it controls gasification agent injection
parameters including oxygen concentration, flow rate, pressure, to make gasification
channel reverse burning, quick ignition and processing, thus the gas injection point
movement is continuous and the gasification process is highly stable.
Description of Figures
[0038]
Figure 1 shows the schematic diagram of the present shaftless CRIP technology.
Figure 2 shows the schematic diagram of gasification furnace employing controllable
gas injection gasification.
Figure 3 shows the underground gasification furnace with supported structure at horizontal
segment of directional well channel as described in Embodiment 1.
Figure 4 shows the schematic diagram of controllable gas injection point movement
gasification process of Embodiment 1 (plane sectional view).
Figure 5 shows the underground gasification furnace with bare hole structure (no support
structure) at horizontal segment of the directional well channel as described in Embodiment
2.
[0039] In the figures: 1-coiled tubing reel ; 2-gas injection well head; 3-coiled tubing;
4-nozzle; 5- glass fiber reinforced plastics sieve-tube; 6-directional well channel;
7-cavity; 8-the roof of coal seam; 9-the floor of coal seam; 10- production well;
11-bare hole segment of horizontal well.
[0040] Hereinafter, the present invention is described in further details. However, the
following embodiments are merely simple examples of the present invention and do not
represent or limit the protection scope of the present invention. The scope of protection
of the invention is prescribed by the attached claims.
Detailed Description
[0041] For better illustrating the present invention and helping to understand the technical
solution of the present invention, the typical but non-limiting embodiments of the
present invention are described in the following:
Embodiment 1
[0042] Gas injection apparatus with controllable gas injection point comprises directional
well channel 6, the directional well channel 6 is disposed with coiled tubing 3. The
coiled tubing 3 is connected with oxygen/oxygen-enriched gas line. The annular space
between the coiled tubing 3 and the directional well 6 has connection to the auxiliary
gasification agent line and steam line. The start end of the coiled tubing 3 is disposed
with gas injection well head 2 and the terminal end is disposed with nozzle 4.
[0043] Coiled tubing reel 1 is used for carrying the coiled tubing 3.
Embodiment 2
[0044] A gas injection technology with controllable gas injection point, wherein oxygen/oxygen-enriched
gas is delivered by the coiled tubing deposited within the directional well channel;
the oxgen/oxygen-enriched gas and the auxiliary gasification agent delivered through
the annular space between the coiled tubing and the directional well wall are uniformly
mixed at the nozzle at the terminal end of coiled tubing; the mixed gasification agent
enters the predetermined gasification position of the coal seam through the directional
well channel or the pore channel within the coal seam.
[0045] The directional well channel is formed by the directional drilling method. The directional
drilling method preferably employ any of directional well drilling technology, horizontal
well drilling technology, lateral drilling technology, radial horizontal well technology,
multilateral well technology, cluster wells technology and extended reach well technology
in petroleum or coal seam gas drilling technologies. The directional well channel
is longer than 10 meters.
[0046] The pore channel within the coal seam is formed by artificial drilling or fracturing
process, or formed by coal seam under thermal effect of burning.
[0047] The directional well channels are unsupported channel or supported channel. The supported
channels employ sieve-tube and/or casing-tube, preferably sieve-tube or the combination
of sieve-tube and casing-tube for support. The support tube materials are combustible
materials, more preferably organic materials, most preferably glass fiber reinforced
plastics or PE pipe materials.
[0048] The oxygen/oxygen-enriched gas is provided by the gasification agent production system.
The oxygen-enriched gas is a mixed gas composed of oxygen and one or both of nitrogen
and carbon dioxide, wherein the concentration by volume of oxygen is larger than 21%.
[0049] The auxiliary gasification agent is one of nitrogen, carbon dioxide and water, or
mixture thereof. The nitrogen is provided by a nitrogen production device. The carbon
dioxide is provided by a decarbonization device.
Embodiment 3
[0050] A controllable gas injection point gasification method, wherein reverse burning,
gasification channel process and gasification production is conducted by segmentally
moving the coiled tubing to make the gas injection point segmentally move to the predetermined
gasification position, and then adjusting the gas injection technology parameters.
[0051] The gasification method comprises the following steps:
- 1) according to the parameters such as thickness and reserves of gasifiable coal seam
in gasification area, segmentally moving coiled tubing according to the gas injection
process to make the gas injection point position segmentally move to the predetermined
gasification position;
- 2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; segmentally moving the flame working face to the predetermined gasification
position in the manner of reverse burning and making gasification channel process
at the same time;
- 3) after completing the ignition and process of the gasification channel, improving
intensity of the gasification agent injection, enhancing the gasification of underground
coal and conducting gas production of underground gasification on a large scale;
- 4) when the coal seam gasification of the predetermined gasification position is done,
determining stopping or reducing gasification agent injection according to the amount
of the coal gasified, and heat value and composition of coal gas, and starting the
injector head to move the oxygen/oxygen-enriched gas injection point to the next predetermined
gasification position;
- 5) conducting the next segment gasification channel process according to step 2),
and completing the underground gasification of the predetermined coal seam area according
to step 3) and 4); repeating those steps until the coal resource around the directional
well channel is gasified completely;
wherein, the gas injection point segmental movement distance in the step 1) is 10∼150m,
the gasification flow rate during the gasification channel ignition and processing
is limited within 300∼3000 m
3/h, and the oxygen concentration by volume in the gasification agent is 21∼55%.
Embodiment 4
[0052] A controllable gas injection point gasification method, wherein reverse burning,
gasification channel processing and gasification production is conducted by continuously
or intermittently lifting the coiled tubing to make the gas injection point continuously
move to the predetermined gasification position, and then adjusting the gas injection
technology parameters.
[0053] The gasification method comprises of the following steps:
- 1) according to the parameters such as thickness and reserve of gasifiable coal seam
in gasification area, and continuously or intermittently lifting coiled tubing according
to the gas injection process to make the gas injection point continuously move to
the predetermined gasification position;
- 2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; achieving continuously processing gasification channel and underground gasification
production on a large scale in a manner of reverse burning;
- 3) adjusting the gasification agent injection parameters whenever necessary, to guarantee
relative stable status of coal gas composition and heat value;
- 4) when coal seam gasification of the predetermined gasification position is done,
controlling reverse movement speed of coiled tubing according to burning speed of
the coal gasification, heat value and composition of coal gas, and gasifiable coal
seam storage situation, until the coal resource around the directional well channel
is gasified completely;
wherein, the flow rate of the gasification agent in the step 2) is set to larger than
2000 m
3/h, and the oxygen concentration by volume of gasification agent is 21∼95%;
and wherein when the oxygen volume concentration is larger than 60%, water steam or
water can be injected to adjust the temperature and gas quality in the cavity.
Working Example 1
[0054] The present example is to apply the controllable gas injection point gasification
method of the present invention in the brown coal seam with low metamorphic degree.
As lithology intensity of coal seam is low so that the borehole is easy to collapse
and shrink, the present example select the directional horizontal well structure supported
with glass fiber reinforced plastics sieve-tube, which has the common advantage of
the present invention and is also beneficial to improve drilling stability and reduce
drilling accident rate.
[0055] Figure 3 shows an underground gasification furnace, wherein coal seam floor 9 is
at a depth of 255 meters, coal seam roof 8 is at a depth of 238 meters, and the coal
is lignite. The gasification furnace comprises directional well channel 6, production
well 10, gasification burning channels, etc. The diameter of the directional well
channel 6 is 177.8mm. The supported glass fiber reinforced plastics sieve-tube at
horizontal segment of the coal seam has diameter of 139.7mm, length of 300meters and
opening rate of 15%. The gas injection apparatus with controllable gas injection point
comprises coiled tubing 3 (diameter: 66.7mm, pressure grade: 6.0 MPa, material:316
stainless steel), gas injection well head 2, which comprises coiled tubing operating
Bop (single side door style) and coiled tubing injector head (ZRT series coiled tubing
injector head); and nozzle 4 (65mm diameter, high temperature resistance up to 1200°C).
[0056] In the example, the gas injection apparatus is employed to make gasification for
the coal seam of the directional well channel 6 of the underground gasification furnace,
as shown in figure 4. The gasification operating pressure of the gasification furnace
is 1.5MPa and O
2/CO
2 is used as gasification agent for gasification production of syngas. After the gasification
furnace is successfully ignited and stable gasification burning area 7 is established
i at the bottom of the production well 10, directional drilling technology is employed
to build up a directional well channel 6 in predetermined gasification coal seam,
then the controllable gas injection point gasification production is carried out.
The detailed process and implementing steps are as follows: (1) delivering coiled
tubing along directional well channel 6 to the predetermined gasification position
A through gas injection well head 2 by using the injector head; avoiding to send the
oxygen nozzle into the burning zone directly; (2) injecting CO
2 into the annular space between the coiled tubing and directional well wall to conduct
replacement protection for the channel with initial flow rate of 300∼400Nm
3/h; (3) slowly injecting oxygen into the degreased coiled tubing and through oxygen
nozzle to mix with CO
2 injected through the annular space; (4) controlling the total amount of injected
gasification agent and oxygen concentration, segmentally moving flame working face
to the predetermined gasification position in the manner of reverse burning, and making
gasification channel processing at the same time; the amount of the gasification agent
for reverse ignition and processing channel is 500∼3000Nm
3/h and the oxygen concentration is 25∼35%; (5) after the channel ignition and processing
is completed, gradually improving the injection amount of the gasification agent to
4000∼6000Nm
3/h, and the oxygen concentration to 60∼70% and then conducting coal gas production
on a large scale; (6) when the gasification at the predetermined gasification position
is completed, determining stopping or reducing gasification agent injection according
to the condition of gasification coal burning amount, gas production heat value and
composition, and starting the injector head and continuously moving coiled tubing
3 to make the oxygen injection point move to the next predetermined gasification position
B; the distance between the predetermined gasification position A and B is 0∼100m;
(7) conducting gasification channel processing according to steps (2)-(4) and accomplishing
the underground gasification of the predetermined area according to steps (4) and
(5); repeating those steps until the coal resource around the directional well channel
6 is gasified completely.
Working Example 2
[0057] The present example is to apply controllable gas injection point gasification method
of the present invention on the lean coal seam with high metamorphic degree. As coal
seam lithology is good and intensity is high, the present example selects unsupported
directional horizontal well structure, which has the common advantage of the present
invention and is also beneficial to reduce furnace building cost and improve coal
seam ignition efficiency.
[0058] Figure 5 shows an underground gasification furnace, wherein coal seam floor 9 is
at a depth of 957 meters, coal seam roof 8 is at a depth of 950 meters, and the coal
is lean coal. The gasification furnace comprises directional well channel 6, production
well 10, gasification burning channels, etc. The diameter of the directional well
channel 6 is 177.8mm. Bare hole segment 11 in horizontal well (the horizontal well
of the coal seam has unsupported bare hole) is 200 meters long. The gas injection
apparatus with controllable gas injection point comprises coiled tubing 3 (diameter:
50.8mm, pressure grade: 6.0 MPa, material: 316 stainless steel, Jiang Su Dong Tai
Hua Xuan Company), gas injection well head 2, which comprises coiled tubing operating
Bop (single side door style, Ao Lan Petroleum Company) and coiled tubing injector
head (ZRT series coiled tubing injector head, Yan Tai Jie Rui Company) and nozzle
4 (50mm diameter, high temperature resistance up to 1200°C, ENN Coal Gasification
mining Co., Ltd.).
[0059] In the example, gas injection apparatus is employed to conduct gasification for the
coal seam of the directional well channel 6 of the underground gasification furnace,
as shown in figure 5. The gasification operating pressure of the gasification furnace
is 2.5MPa and O
2/CO
2 is used as gasification agent for gasification production of syngas. After the gasification
furnace is successfully ignited and stable gasification burning area 7 is established
at the bottom of the production well 10, directional drilling technology is employed
to build up directional well channel 6 in predetermined gasification coal seam and
then controllable gas injection point gasification production is carried out. The
detailed process and implementing steps are as follows: (1) delivering coiled tubing
along directional well channel 6 to the predetermined gasification position A through
gas injection well head 2 by using the injector head; avoiding to send the oxygen
nozzle into the burning zone directly; (2) injecting CO
2 into the annular space between the coiled tubing and directional well wall to conduct
replacement protection for the channel with initial flow rate of 400∼600Nm
3/h; (3) slowly injecting oxygen into the degreased coiled tubing and through oxygen
nozzle to mix with CO
2 injected through the annular space; (4) controlling the total amount of the injected
gasification agent and oxygen concentration, segmentally moving the flame working
face to the predetermined gasification position in the manner of reverse burning,
and conducting gasification channel processing at the same time; the gasification
agent amount for reverse ignition and processing channel is 600∼3500Nm
3/h and the oxygen concentration is 25∼55%; (5) after channel ignition and processing
is completed, gradually improving the injection amount of the gasification agent to
4000∼7500Nm
3/h and oxygen concentration to 60∼70% and then conducting coal gas production on a
large scale; (6) when the gasification at the predetermined gasification position
is completed, determining stopping or reducing gasification agent injection according
to the condition of the amount of coal gasified, gas production heat value and composition,
and starting the injector head and continuously moving coiled tubing 3 to make the
oxygen injection point move to the next predetermined gasification position B; the
distance between the predetermined gasification position A and B is 0∼40m; (7) conducting
gasification channel processing according to steps (2)-(4) and accomplishing the underground
gasification of the predetermined area according to steps (4) and (5); repeating those
steps until the coal resource around the directional well channel 6 is gasified completely.
[0060] When the syngas (including H
2, CO, CH
4, CO
2, H
2O, etc.) produced by the gasification method of the present invention is delivered
to the ground through the production well 10 and purified, the product mainly comprising
H
2, CO, CH
4 is obtained.
[0061] The applicant stated that the present invention employ the embodiments and examples
above to describe the detailed structure feature and the gas injection and gasification
methods of the present invention, but the present invention is not limited to the
detailed structure feature and the injection and gasification methods above, i.e.
it does not mean that the present invention must rely on the detailed structure feature
and the gas injection and gasification methods above to implement. Persons skilled
in the art should understand, any improvement of the present invention, the equivalent
replacement to the raw materials of the present invention product, adding auxiliary
ingredients, specific mode selection, etc. fall within the protection scope and disclosure
scope of the present invention.
1. A gas injection apparatus with controllable gas injection point, which comprises directional
well channel; the directional well channel is disposed with coiled tubing; the coiled
tubing is connected with oxygen/oxygen-enriched gas line; the annular space between
the coiled tubing and the directional well has connection to an auxiliary gasification
agent line and a steam line; the start end of the coiled tubing is disposed with gas
injection well head and the terminal end is disposed with nozzle.
2. A gas injection process using the gas injection apparatus according to claim 1, wherein
the oxygen/oxygen-enriched gas is delivered by the coiled tubing deposited within
the directional well channel; the oxygen/oxygen-enriched gas, and auxiliary gasification
agent delivered through the annular space between the coiled tubing and the directional
well wall are uniformly mixed at the nozzle at the terminal end of the coiled tubing;
the mixed gasification agent enters a predetermined gasification location of the coal
seam through a directional well channel or pore channels within the coal seam.
3. The gas injection process according to claim 2, wherein the directional well channel
is formed by using directional drilling method; the directional drilling method preferably
employ any of directional well technology, horizontal well drilling technology, lateral
drilling technology, radial horizontal well technology, multilateral well technology,
cluster wells technology and extended reach well technology in oil or coal-bed gas
drilling technologies;
preferably, the directional well channel is longer than 10 meters;
preferably, the pore channels within the coal seam is formed by using artificial drilling
or fracturing process, or formed by coal seam under thermal effect of burning.
4. The gas injection process according to claim 2 or 3, wherein the directional well
channels are unsupported channel or supported channel;
preferably, the supported channel employs sieve tube support and/or casing-tube support,
more preferably sieve tube support or the combination of sieve-tube support and casing-tube
support;
preferably, materials for the support tube are combustible material, more preferably
organic materials, most preferably glass fiber reinforced plastics or PE pipe material;
preferably, the oxygen/oxygen-enriched gas is provided by the gasification agent production
system; preferably, the oxygen-enriched gas is a mixed gas of oxygen with one or both
of nitrogen and carbon dioxide, wherein the concentration by volume of oxygen is more
than 21%;
preferably, the auxiliary gasification agent is one selected from nitrogen, carbon
dioxide and water or the mixture thereof; preferably, the nitrogen is provided by
the nitrogen production device; preferably, the carbon dioxide is provided by the
decarbonization device.
5. A gasification method with controllable gas injection point using the gas injection
apparatus according to claim 1, wherein the gas injection point segmentally move to
the predetermined gasification position by moving the coiled tubing at several times,
then the gas injection process parameter is adjusted for reverse burning, gasification
channel process and gasification production.
6. The gasification method according to claim 5, which comprises the following steps:
1) according to the parameters such as thickness and reserves of gasifiable coal seam
in gasification area, segmentally moving coiled tubing according to the gas injection
process to make the gas injection point position segmentally move to the predetermined
gasification position;
2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; segmentally moving the flame working face to the predetermined gasification
position in the manner of reverse burning and making gasification channel process
at the same time;
3) after completing the ignition and process of the gasification channel, improving
intensity of the gasification agent injection, enhancing the gasification of underground
coal and conducting gas production of underground gasification on a large scale;
4) when the coal seam gasification of the predetermined gasification position is done,
determining stopping or reducing gasification agent injection according to the consumed
amount of the gasification coal, and heat value and composition of coal gas, and starting
the injector head to move the oxygen/oxygen-enriched gas injection point to the next
predetermined gasification position;
5) conducting the next segment gasification channel process according to step 2),
and completing the underground gasification of the predetermined coal seam area according
to step 3) and 4); repeating those steps until the gasification mining of coal resource
around the directional well channel is completed.
7. The gasification method according to claim 6, wherein the distance traveled each time
for the gas injection point is 10∼150m;
preferably, the flow rate of the gasification agent at the gasification channel ignition
and processing is controlled within 300∼3000 m3/h;
preferably, the oxygen concentration by volume in the gasification agent is 21∼55%.
8. A gasification method with controllable gas injection point using the gas injection
apparatus according to claim 1, wherein the coiled tubing is continuously or intermittently
lifted to make the gas injection point continuously move to the predetermined gasification
position, then the gas injection process parameters are adjusted for reverse burning,
gasification channel processing and gasification production.
9. The gasification method according to claim 8, which comprises the following steps:
1) according to the parameters such as thickness and reserves of gasifiable coal seam
in gasification area, and continuously or intermittently lifting coiled tubing according
to the gas injection process to make the gas injection point move to the predetermined
gasification position;
2) adjusting the pressure and flow rate of a single gas and controlling the parameters
such as flow rate, pressure and oxygen concentration of the injected gasification
agent; achieving continuously processing gasification channel and gas production on
a large scale in a manner of reverse burning;
3) adjusting the gasification agent injection parameters whenever necessary, to guarantee
relative stable status of coal gas composition and heat value;
4) when the coal seam in the predetermined gasification area is gasified completely,
controlling movement speed of coiled tubing according to burning speed of the flame,
heat value and composition of coal gas, and the storage situation of the coal seam,
until the coal resource around the directional well channel is gasified completely.
10. The gasification method according to claim 9, wherein the flow rate of the gasification
agent of step 2) is set to larger than 2000 m3/h; preferably, the oxygen concentration by volume of the gasification agent is 21∼95%;
preferably, when the oxygen concentration by volume is more than 60%, water steam
or water can be injected to adjust temperature and coal gas quality in the cavity.