CN112127866B - Process for developing deep coal bed by using underground coal gasification technology - Google Patents
Process for developing deep coal bed by using underground coal gasification technologyDownload PDFInfo
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- CN112127866B CN112127866BCN201910554318.7ACN201910554318ACN112127866BCN 112127866 BCN112127866 BCN 112127866BCN 201910554318 ACN201910554318 ACN 201910554318ACN 112127866 BCN112127866 BCN 112127866B
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- E—FIXED CONSTRUCTIONS
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/295—Gasification of minerals, e.g. for producing mixtures of combustible gases
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- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
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- E21B—EARTH OR ROCK 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
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/24—Enhanced recovery methods for obtaining hydrocarbons using heat, e.g. steam injection
- E21B43/243—Combustion in situ
- E21B43/247—Combustion in situ in association with fracturing processes or crevice forming processes
- E—FIXED CONSTRUCTIONS
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- E21B—EARTH OR ROCK 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
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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Abstract
Description
Technical Field
The invention relates to a process for developing a deep coal bed by utilizing an underground coal gasification technology, belonging to the technical field of coal bed development.
Background
The Underground Coal Gasification technology (UCG) is also called as in-situ Coal Gasification, and the process is to convert the Coal bed existing Underground from physical Coal mining to chemical Coal mining, and the essential thing is to convert the useful substances (volatile components, fixed carbon and the like) in the Coal into combustible gas through physical and chemical conversion modes such as pyrolysis, combustion, Gasification and the like. The UCG integrates three processes of well construction, coal mining and gasification into a whole, and has the advantages of low gas production cost, high safety and good environmental benefit. The cost of the gas produced by the UCG is only 25-50% of that of the ground gasification furnace, and the gas can be used as the raw material gas for gas power generation, boiler fuel and chemical product synthesis, thereby obviously reducing the cost of power generation or chemical product synthesis. UCG still has apparent environmental benefit, reduces the emission of coal fired pollution, gangue and lime-ash greatly, can effectively solve the atmosphere haze problem that present coal-fired arouses, and combines together with carbon entrapment and seal up the deposit technique, can effectively reduce greenhouse gas and discharge. At present, UCG is widely regarded worldwide, and a number of theoretical studies and industrial trials have been conducted on the technology in soviet union, europe, usa, japan, australia, china and many countries in asia. Therefore, underground coal gasification is firstly a coal development method, is an innovation of the traditional coal mining mode, and is known as a second generation coal mining method; from the benefit, the technology is a new technology for developing clean energy by low carbon of high carbon resources. The technology has wide application prospect in the aspects of mining and utilization of residual coal such as low-quality (high-sulfur and high-ash), steep inclined, thin coal bed, deep coal bed, coal pressing under the third coal bed, conventional technology economy, non-mining and the like.
In recent years, the industrial test and the industrialized popularization strength of underground coal gasification are increased in main coal producing countries in the world, a large number of field tests are carried out in the United states, Australia, Canada, south Africa, China and the like, and the sequence of the commercial popularization and industrialization of underground coal gasification is opened. The underground coal gasification test in China begins in the 60 th century, and twenty field tests are carried out so far, so that well-type and well-free underground coal gasification processes are formed. At present, the coal underground gasification does not realize industrialized production, and one important reason is that the scale of the coal underground gasification is small and the gas production is unstable. On one hand, under the influence of external hydrological and geological environment, the conditions (coal thickness, coal quality and the like) and occurrence conditions (geology, hydrology, structure and the like) of a gasified coal bed are complex and variable, the difficulty is increased for the underground gasification process of the coal, and the factors needing manual regulation and control are more; secondly, the control means of the underground coal gasification process is limited, and is influenced by factors such as high temperature, gas, coal body thermal fracture, surrounding rock stress, overlying strata collapse, fissure zone development and the like of an underground gasification space, so that effective monitoring and control means are difficult to be adopted like an underground coal gas producer, and the difficulty of artificial regulation and control is increased.
Therefore, in order to solve the problems of the existing underground coal gasification furnace production system, the underground coal gasification furnace production system and the process which are adaptive to geological environment and have a controllable function need to be developed, and technical support is provided for further realizing the industrialization of underground coal gasification.
At present, scholars at home and abroad propose different types of underground coal gasification furnace type structures and gasification production methods aiming at different coal seam occurrence conditions. In the aspect of the construction of the gasification furnace type, from the distribution positions of the gas injection channel, the gasification channel and the exhaust channel, the underground gasification furnace can be divided into a plurality of furnace types, namely a blind hole furnace, a one-line furnace, a V-shaped furnace, a U-shaped furnace, an E-shaped furnace and the like, and then a porous furnace and a long fireplace capable of converting the gas injection and exhaust operations are invented. The research direction of foreign underground gasification is mainly a well-free underground coal gasification process, which constructs an underground coal gasification furnace by drilling a well on the ground, and the well-free gasification process which is relatively mature comprises a linear Injection Point retreat (CRIP) process and a CRIP process of parallel directional drilling. In the last forty years, the soviet union firstly carried out an on-site underground gasification test, in which two adjacent vertical drilling wells are respectively used as an injection well and a gas production well of a gasification agent, then the bottoms of the two vertical drilling wells are communicated in a coal seam by adopting various communication methods (such as fire communication, electric power communication, reverse combustion, air fracturing and the like) to form a gasification channel, and then the gasification agent is blown in from a gas injection well, so that gas is produced from the gas production well. The furnace building process of the gasification furnace has the defects of low through speed, poor through directivity, difficult through or no through when the vertical well spacing is large; the vertical drilling distance is small, the number of vertical drilling is large during continuous production, and the investment is large; a gas injection device is not arranged in the gasification furnace, and the gasification agent is diffused and combusted in the whole gasification furnace, so that the combustion range and the boundary can not be effectively controlled, and the gas production quality is low; the enlarged combustion range causes large area collapse of overlying strata, and the stability control effect of surrounding rocks is poor. Since the last seventies, the countries in europe and america, represented by the united states, mainly develop a wellless CRIP process, which adopts a drawtube type mobile gas injection point device in the aspect of gas injection control, periodically retreats to pull a gas injection point, and retreats the gas injection point for a certain distance each time, but the process needs to build a large-scale gas injection elbow spiral pulling device on the ground, so that the equipment investment is high, the process operation is complex, the gas injection elbow is difficult to seal at the ground end, and when the coal seam buries deeply, the operation reliability of the mobile gas injection device is reduced due to the influence of geological stress and borehole deformation.
Therefore, providing a novel process for developing deep coal seams by using underground coal gasification technology has become an urgent technical problem in the field.
Disclosure of Invention
In order to solve the defects and shortcomings, the invention aims to provide a process for developing a deep coal bed by using an underground coal gasification technology. The process provided by the invention is suitable for developing deep coal resources with the depth of more than 500m, and the method can effectively reduce the complexity of operation, improve the production efficiency of the coal bed and improve the development effect and gasification effect of the deep coal bed.
In order to achieve the above objects, the present invention provides a process for developing a deep coal seam using an underground coal gasification technology, wherein the process comprises the steps of:
(1) according to the direction perpendicular to the maximum principal stress, drilling a horizontal production well in parallel above the bottom of a coal seam, and drilling two rows of vertical injection wells at two sides of the horizontal production well, wherein the horizontal section of the horizontal production well is completed by a large-size slotted sieve tube and a common casing at intervals, and the horizontal production well corresponding to the vertical injection well is the large-size slotted sieve tube;
(2) perforating a vertical injection well in a coal seam, and sequentially carrying out CO2 Fracturing to form an extended fracture, followed by maintaining formation hydrostatic pressure within the fracture and filling with quartz sand;
(3) putting a continuous oil pipe in the horizontal production well, and putting a packer according to the distribution position of the large-size slotted sieve pipe;
(4) continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well to the coal bed fracture pressure, closing the horizontal production well, quickly injecting high-temperature steam from the vertical injection well, and continuously supplementing oxygen-enriched air to keep the pressure in the vertical injection well above the hydrostatic pressure; and meanwhile, monitoring the temperature change condition near the vertical injection well, and opening the horizontal production well when the temperature and the pressure of the vertical injection well suddenly rise so as to ensure that the production pressure is produced under the back pressure higher than the hydrostatic pressure.
According to the specific embodiment of the invention, in the process, preferably, the injection speed of the air or the oxygen-enriched air is 20000-40000 square/day so as to control the bottom flow pressure of the production well within the original coal bed hydrostatic pressure range.
According to a particular embodiment of the present invention, preferably, the process further comprises:
monitoring the change of the components of the produced gas in the production process, reducing the injection speed of air or oxygen-enriched air when the volume content of oxygen in the produced gas exceeds 3%, closing the horizontal production well for a period of time, and then opening the well to continue production.
According to a particular embodiment of the invention, in said process, preferably, when the oxygen content by volume in the produced gas exceeds 3%, the injection rate of said air or oxygen-enriched air is reduced by 30-50%; such as 10000-.
In the process according to a particular embodiment of the invention, the horizontal production well is preferably shut down for 10-40 days.
In accordance with a particular embodiment of the present invention, in the process, preferably the well is opened to continue production, comprising:
continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well at pulse pressure, and then producing;
wherein the pulsed pressure comprises: the pressure of the air or the oxygen-enriched air is made to be more than 1.5 times of the hydrostatic pressure and kept for 1 to 3 days, and then the pressure of the air or the oxygen-enriched air is reduced to 0.6 to 0.8 times of the hydrostatic pressure and kept for 10 to 30 days.
According to a particular embodiment of the present invention, preferably, the process further comprises:
monitoring the temperature of the produced gas during production, closing the horizontal production well when the temperature of the produced gas exceeds 200 ℃, and switching to other horizontal wells distal to the vertical injection well to continue production.
According to a particular embodiment of the present invention, preferably, the process further comprises:
changes in the composition of the produced gas are monitored during production and production is stopped when the oxygen content of the produced gas continues to rise and exceeds 10%.
According to the specific embodiment of the invention, in the process, preferably, in the step (1), a horizontal well is drilled in parallel at a distance of 1-2m above the bottom of the coal seam.
According to the specific embodiment of the invention, in the process, preferably, in the step (1), the length of the horizontal well is 300-1000 m.
According to the specific embodiment of the invention, in the process, preferably, in the step (1), two rows of vertical wells are drilled at a distance of 30-50m from the horizontal well, and the distance between two adjacent vertical wells in each row is 30-70 m.
According to a specific embodiment of the present invention, in the process, preferably, in the step (1), the length of the large-sized slotted screen is 20 to 40 m.
According to a specific embodiment of the present invention, in the process, preferably, in step (1), the interval of the interval completion is 20-40 m.
According to the specific embodiment of the invention, in the process step (1), a horizontal well can be used as a gas injection well instead of a row of vertical injection wells;
two horizontal wells can be adopted to replace two rows of vertical injection wells as gas injection wells;
the length of the horizontal well is 300-1000m, the horizontal gas injection well is vertically positioned above the horizontal production well by 3-5m, the horizontal distance is 30-50m, the horizontal production well corresponding to the horizontal gas injection well is a large-size slotted screen pipe, and screen pipe completion is performed on the horizontal gas injection well in a segmented manner.
According to a particular embodiment of the invention, in said process, preferably, in step (2), the CO is carried out sequentially2 And fracturing to form a fracture extending 30-60 m.
According to a specific embodiment of the present invention, in the process, preferably, in the step (2), the silica sand has a particle size of 0.5 to 2 mm.
According to a specific embodiment of the present invention, in the process, the step (2) may further include: and (3) carrying out fishbone well drilling in the horizontal production well to drill branches of 30-50m, and ensuring that the distance from the single branch of the fishbone well to the bottom of the vertical injection well is less than 2m so as to improve the displacement efficiency between vertical wells.
According to the specific embodiment of the invention, in the process, in the step (3), the number of the used packers is preferably enough to meet the requirements of the sectional production (for example, if the horizontal production well is divided into three sections for control, 3 packers need to be put in, and a production string needs to be configured for each part of the horizontal section design).
According to a particular embodiment of the invention, in said process, preferably in step (2), CO2 CO used in the fracturing process2 The pressure of the fracturing fluid is kept to be 2.1-2.5 times of the hydrostatic pressure for 1-2 days.
According to a particular embodiment of the present invention, in the process, it is preferred that the concentration of oxygen in step (4) is in the range of 20 to 60% based on the total volume of the oxygen-enriched air.
According to the specific embodiment of the present invention, in the process, preferably, in the step (4), the injection amount of the high-temperature steam is 100-200 t.
According to the specific embodiment of the present invention, in the process, preferably, in the step (4), the temperature of the high-temperature steam is 260-320 ℃.
According to a specific embodiment of the present invention, in the process, preferably, in the step (4), when the temperature of the vertical injection well suddenly rises to above 500 ℃, and at the same time, the pressure of the vertical injection well exceeds the hydrostatic pressure by above 2MPa, the horizontal production well is opened.
Wherein, the pressure of the vertical injection well is kept close to the hydrostatic pressure in the initial stage, and the upper part and the lower part of the vertical injection well do not exceed 1 MPa.
According to the specific embodiment of the invention, preferably, when a high permeability layer is present at the bottom of the coal seam, the process comprises the following steps:
1) according to the direction perpendicular to the maximum principal stress, drilling a horizontal production well in parallel above the bottom of a coal seam, and drilling two rows of vertical injection wells at two sides of the horizontal production well, wherein the horizontal section of the horizontal production well is completed by a large-size slotted sieve tube and a common casing at intervals, and the horizontal production well corresponding to the vertical injection well is the large-size slotted sieve tube;
2) perforating a vertical injection well in a coal seam, and sequentially carrying out CO2 Fracturing to form an extended fracture, followed by maintaining formation hydrostatic pressure within the fracture and filling with quartz sand;
3) continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen well completion section corresponding to the vertical injection well until the fracture pressure of the coal bed is reached, closing the horizontal production well, quickly injecting high-temperature steam from the vertical injection well, and continuously supplementing oxygen-enriched air to keep the pressure in the vertical injection well above the hydrostatic pressure; and simultaneously monitoring the temperature change condition near the vertical injection well, and opening the horizontal production well when the temperature and the pressure of the vertical injection well suddenly rise so as to ensure that the production is carried out under the back pressure of which the production pressure is higher than the hydrostatic pressure.
According to an embodiment of the present invention, in the process, preferably, the deep coal seam is a coal seam having a depth of 500m or more.
Compared with the existing method for gasifying the coal bed in the field, the process for developing the deep coal bed by using the underground coal gasification technology has the following unexpected beneficial technical effects:
1) the process adopts a mode of combining the vertical well and the horizontal well, so that gas injection well points are effectively increased, the distance between the vertical well and the horizontal well is small, and formed fracturing cracks are easy to form and keep effective communication;
2) the process injects oxygen-enriched air into the coal bed at high pressure, and injects high-temperature steam to initiate spontaneous combustion of the coal bed, so that the efficiency is higher than that of electric ignition, and the process is simple and safe;
3) the process adopts CO in a vertical well2 Fracturing and maintaining high fluid (CO) for long periods of time2 Fracturing fluid) pressure, can keep the fracture in an open state and is beneficial to CO2 The gas diffuses to the deep part of the coal bed, so that the pore pressure of the coal body is increased, the crack opening is promoted, and the desorption of the adsorbed gas in the coal bed is promoted;CO 22 After the coal is diffused into the coal bed, the permeability of the coal bed can be improved, and the combustion expansion condition is improved;
4) the operation process adopts pulse pressure operation, so that the coal bed creep effect in the combustion cavity can be promoted, the coal creep volume is increased, and high-efficiency fuel is provided for gasification combustion; meanwhile, the pulse operation has a transformation effect on the deep part of the coal seam, and formation and expansion of cracks in the coal seam are promoted.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of well pattern deployment in the process for developing deep coal seams by using underground coal gasification technology, which is provided byembodiment 1 of the invention.
Fig. 2 is a schematic diagram (top view) of the well pattern deployment in the process for developing deep coal seams by using underground coal gasification technology, which is provided inembodiment 1 of the invention.
Fig. 3 is a schematic diagram of the screen distribution and the structure of the horizontal production well in the process for developing deep coal seams by using underground coal gasification technology according toembodiment 1 of the present invention.
The main reference numbers illustrate:
0. the bottom of the coal bed;
1. a horizontal production well;
1-1, 1-3, 1-5 and 1-7 are a first casing completion section to a fourth casing completion section of the horizontal production well;
1-2, 1-4, 1-6 and 1-8 are the first screen pipe well completion section to the fourth screen pipe well completion section of the horizontal production well;
2. a vertical injection well;
2-1, a first vertical injection well;
2-2, a second vertical injection well;
2-3, a third vertical injection well;
2-4, a fourth vertical injection well;
2-5, a fifth vertical injection well;
2-6, a sixth vertical injection well;
2-7, a seventh vertical injection well;
2-8 and an eighth vertical injection well.
Detailed Description
In order to clearly understand the technical features, objects and advantages of the present invention, the following detailed description of the technical solutions of the present invention will be made with reference to the following specific examples, which should not be construed as limiting the implementable scope of the present invention.
Example 1
The embodiment provides a process for developing a deep coal seam by using an underground coal gasification technology, wherein the process comprises the following steps:
the burial depth of the coal seam in the embodiment is 930m, the effective thickness of the coal seam is 20.0m, and the coal seam is continuously and stably distributed and is a high-quality lignite coal seam. The coal seam is not provided with a pure mudstone interlayer, the upper part of the coal seam is provided with a better cover layer, the bottom of the coal seam is provided with a mudstone layer, and the permeability of the coal seam is 0.01 md.
1. According to the geological characteristics and the current development situation of the coal bed, performing primary evaluation:
the coal seam satisfies the following conditions: the reservoir is deep and 930m, the thickness of the coal seam is 20.0m, and the top cover layer of the coal seam is well developed, so that gas can be effectively prevented from escaping;
2. drilling a horizontal production well 1 at a position 1-2m above the coal bed bottom 0 in parallel according to a direction perpendicular to the maximum principal stress, wherein the length of the horizontal production well is 300m, and two rows ofvertical injection wells 2 are drilled at two sides 35m away from the horizontal production well, in the embodiment, 8 vertical injection wells are arranged, and are respectively marked as a first vertical injection well to an eighth vertical injection well, and the corresponding reference numbers in the figure 1 are respectively 2-1 to 2-8;
the distance between every two adjacent vertical injection wells in each row is 70 m; the well pattern deployment in this embodiment is schematically illustrated in fig. 1 and 2;
the horizontal section of the horizontal production well is completed at intervals by a large-size slotted sieve tube and a common casing and is respectively recorded as a sieve tube completion section and a casing completion section, in the embodiment, the sieve tube completion section has 4 sections which are respectively recorded as a first sieve tube completion section to a fourth sieve tube completion section, and the corresponding reference numerals in figure 3 are respectively 1-2, 1-4, 1-6 and 1-8; the number of the casing completion sections is 4, and the casing completion sections are respectively marked as a first casing completion section to a fourth casing completion section, and the corresponding reference numbers in the figure 3 are respectively 1-1, 1-3, 1-5 and 1-7;
wherein, the length of the single-section sieve tube is 35m, the length of the single-section casing is 35m, the slotted sieve tube is 1m multiplied by 1.5mm, the phase interval is 30 degrees, the length interval is 0.5m, and the distribution and the structural schematic diagram of the sieve tube of the horizontal production well are shown in figure 3;
3. perforating the vertical injection well within the range of 3m above the bottom of the coal bed, and sequentially carrying out CO treatment on the coal bed2 Fracturing to form a crack extending for 30-50m, then keeping the formation hydrostatic pressure (about 10 MPa) in the crack and filling quartz sand with the grain diameter of about 2 mm;
4. running a coiled tubing in the horizontal production wellbore, and running 3 packers (1-3, 1-5 and 1-7 in the figure 3) according to the distribution positions of the screen pipes;
5. injecting air or oxygen-enriched air from the vertical injection well to 19MPa continuously to each large-size slotted screen pipe completion section corresponding to the vertical injection well, closing the horizontal production well, then injecting 150t of high-temperature steam into each 1 vertical injection well within 1 day, and then continuously supplementing the oxygen-enriched air to keep the pressure in the vertical injection well above 9.3 MPa; monitoring the temperature change condition near the vertical injection well, when the temperature of the vertical injection well suddenly rises after two days until the temperature exceeds 500 ℃, and simultaneously the pressure of the vertical injection well also rises to 15MPa, and opening a production well to keep the pressure of an injection and production system at the back pressure of 10MPa for production;
6. the process requires constant monitoring of the change in the composition of the produced gas, wherein the initial produced gas has a composition of 45% by volume CO2 15% by volume of CO, 10% by volume of H2 15% by volume of CH4 And 15 v% of N2 . After 2 months of production, the produced gas from the horizontal producer was found to have oxygen content of 3%. Then the gas injection speed (air or oxygen-enriched air) of the injection well is reduced, the corresponding production pipe column of the part is closed for 20 days, and then the well is opened for production, so that the oxygen content is obviously reduced;
opening the well to continue production, comprising:
continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well at pulse pressure, and then producing;
wherein the pulsed pressure comprises: keeping the pressure of the air or the oxygen-enriched air at 20MPa for 3 days, and then reducing the pressure of the air or the oxygen-enriched air to 6MPa for one month; then switching to 20MPa, and circulating the steps; maintaining the high pressure (20MPa) for 3 days, and then reducing the operating pressure (6MPa) for 30 days;
7. after half a year of operation, the produced gas temperature of three sections of horizontal production wells exceeds 200 ℃, the corresponding production well sections are closed, the vertical injection wells on the different sides of the horizontal injection wells are converted into production wells for continuous production, at the moment, the operation mode is that 2-1, 2-2, 2-3 and 2-4 on one side of the horizontal well are injection wells, and 2-5, 2-6, 2-7 and 2-8 on the other side are production wells;
8. after 2 years of operation, the production process of the vertical production well on the opposite side is continued until the amount of oxygen produced continuously rises over 10%, and the production process is stopped.
Through statistics, in the embodiment, the deep coal seam is developed by using the underground coal gasification technology, and the accumulated gas yield reaches 5 × 107 m3 The underground gasification quantity of the deep coal seam is reduced to 6 ten thousand tons, so that compared with the existing development method, the underground gasification development method of the deep coal seam provided by the invention obviously improvesThe production effect of the deep coal bed gasification technology improves the development efficiency and the stable production time, and has better economic effect.
The above description is only exemplary of the invention and should not be taken as limiting the scope of the invention, so that the invention is intended to cover all modifications and equivalents of the embodiments described herein. In addition, the technical features and the technical inventions of the present invention, the technical features and the technical inventions, and the technical inventions can be freely combined and used.
Claims (17)
1. A process for developing a deep coal seam by using an underground coal gasification technology is characterized by comprising the following steps:
(1) according to the direction perpendicular to the maximum principal stress, drilling a horizontal production well in parallel above the bottom of a coal seam, and drilling two rows of vertical injection wells at two sides of the horizontal production well, wherein the horizontal section of the horizontal production well is completed by a large-size slotted sieve tube and a common casing at intervals, and the horizontal production well corresponding to the vertical injection well is the large-size slotted sieve tube; wherein in the step (1), the length of the large-size slotted sieve tube is 20-40 m;
(2) perforating a vertical injection well in a coal seam, and sequentially carrying out CO2 Fracturing to form an extended fracture, followed by maintaining formation hydrostatic pressure within the fracture and filling with quartz sand;
(3) putting a continuous oil pipe in the horizontal production well, and putting a packer according to the distribution position of the large-size slotted sieve pipe;
(4) continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well to the coal bed fracture pressure, closing the horizontal production well, quickly injecting high-temperature steam from the vertical injection well, and continuously supplementing oxygen-enriched air to keep the pressure in the vertical injection well above the hydrostatic pressure; meanwhile, monitoring the temperature change condition near the vertical injection well, and opening a horizontal production well when the temperature of the vertical injection well suddenly rises to more than 500 ℃ and the pressure of the vertical injection well exceeds the hydrostatic pressure by more than 2MPa so as to ensure that the production pressure is produced under the back pressure higher than the hydrostatic pressure;
wherein, in the step (4), the injection amount of the high-temperature steam is 100-200t, the temperature of the high-temperature steam is 260-320 ℃, and the high-temperature steam is rapidly injected from the vertical injection well within 1 day;
wherein the deep coal seam is a coal seam with the depth of more than 500 m.
2. The process as claimed in claim 1, wherein the injection rate of the air or oxygen-enriched air is 20000-.
3. The process according to claim 1 or 2, characterized in that it further comprises:
monitoring the change of the components of the produced gas in the production process, reducing the injection speed of air or oxygen-enriched air when the volume content of oxygen in the produced gas exceeds 3%, closing the horizontal production well for a period of time, and then opening the well to continue production.
4. A process according to claim 3, wherein the injection rate of air or oxygen-enriched air is reduced by 30-50% when the oxygen content of the produced gas exceeds 3% by volume.
5. The process of claim 3, wherein the horizontal production well is shut in for 10-40 days.
6. The process of claim 3, wherein the opening continues production, comprising:
continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well at pulse pressure, and then producing;
wherein the pulsed pressure comprises: the pressure of the air or the oxygen-enriched air is made to be more than 1.5 times of the hydrostatic pressure and kept for 1 to 3 days, and then the pressure of the air or the oxygen-enriched air is reduced to 0.6 to 0.8 times of the hydrostatic pressure and kept for 10 to 30 days.
7. The process of claim 1, further comprising:
the temperature of the produced gas is monitored during production, and when the temperature of the produced gas exceeds 200 ℃, the horizontal production well is shut down and production continues with the other horizontal production well shifted distally from the vertical injection well.
8. The process of any one of claims 1 and 6 to 7, further comprising:
changes in the composition of the produced gas are monitored during production and production is stopped when the oxygen content of the produced gas continues to rise and exceeds 10%.
9. The process of claim 1, wherein in step (1), the horizontal producer well is drilled in parallel at a distance of 1-2m above the bottom of the coal seam.
10. The process as claimed in claim 1, wherein in step (1), the length of the horizontal production well is 300-1000 m.
11. The process according to claim 1, wherein in the step (1), two rows of vertical wells are drilled at the two sides of the horizontal production well with the distance between two adjacent vertical wells in each row being 30-70 m.
12. The process of claim 1, wherein in step (1), the interval completion is at intervals of 20-40 m.
13. The process according to claim 1, wherein in step (2), CO is carried out sequentially2 And fracturing to form a fracture extending 30-60 m.
14. The process according to claim 1, wherein in the step (2), the quartz sand has a particle size of 0.5 to 2 mm.
15. The process according to claim 1, wherein in step (2), CO is used2 CO used in the fracturing process2 The pressure of the fracturing fluid is kept to be 2.1-2.5 times of the hydrostatic pressure for 1-2 days.
16. The process of claim 1, wherein in step (4), the concentration of oxygen in the oxygen-enriched air is 20-60% based on the total volume of the oxygen-enriched air.
17. The process of claim 1, wherein when a high permeability layer is present at the bottom of the coal seam, the process comprises the steps of:
1) according to the direction perpendicular to the maximum principal stress, drilling a horizontal production well in parallel above the bottom of a coal seam, and drilling two rows of vertical injection wells at two sides of the horizontal production well, wherein the horizontal section of the horizontal production well is completed by a large-size slotted sieve tube and a common casing at intervals, and the horizontal production well corresponding to the vertical injection well is the large-size slotted sieve tube;
2) perforating a vertical injection well in a coal seam, and sequentially carrying out CO2 Fracturing to form an extended fracture, followed by maintaining formation hydrostatic pressure within the fracture and filling with quartz sand;
3) continuously injecting air or oxygen-enriched air from the vertical injection well to each large-size slotted screen pipe completion section corresponding to the vertical injection well to the coal bed fracture pressure, closing the horizontal production well, quickly injecting high-temperature steam from the vertical injection well, and continuously supplementing oxygen-enriched air to keep the pressure in the vertical injection well above the hydrostatic pressure; and simultaneously monitoring the temperature change condition near the vertical injection well, and opening the horizontal production well when the temperature and the pressure of the vertical injection well suddenly rise so as to ensure that the production is carried out under the back pressure of which the production pressure is higher than the hydrostatic pressure.
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| CN112761613A (en)* | 2021-01-20 | 2021-05-07 | 王柱军 | Deep coal in-situ pyrolysis mining and utilizing process |
| CN115012890A (en)* | 2021-03-03 | 2022-09-06 | 中国石油化工股份有限公司 | Steam pressure flooding oil extraction method for shallow and thin layer super heavy oil |
| CN115247549B (en)* | 2021-04-27 | 2023-11-28 | 中国石油天然气集团有限公司 | Method for establishing chemical ignition controlled environment for underground coal gasification |
| CN113027403B (en)* | 2021-05-27 | 2021-08-06 | 中国煤炭地质总局勘查研究总院 | Method and electronic device for injecting hot steam into coal seam |
| CN115419388B (en)* | 2022-08-30 | 2024-07-12 | 中天碱业有限公司 | Method for exploiting brine from underground deep trona ore |
| CN115467648B (en)* | 2022-08-31 | 2024-04-05 | 西安石油大学 | A microwave energy underground oxygen-free coal gasification method |
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