CN115217443A - Nitrogen injection yield increasing method - Google Patents
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- CN115217443A CN115217443A CN202110420078.9A CN202110420078A CN115217443A CN 115217443 A CN115217443 A CN 115217443A CN 202110420078 A CN202110420078 A CN 202110420078A CN 115217443 A CN115217443 A CN 115217443A
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 title claims abstract description 823
- 229910052757 nitrogen Inorganic materials 0.000 title claims abstract description 403
- 238000002347 injection Methods 0.000 title claims abstract description 345
- 239000007924 injection Substances 0.000 title claims abstract description 345
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000007789 gas Substances 0.000 claims abstract description 401
- 238000004519 manufacturing process Methods 0.000 claims abstract description 275
- 239000003245 coal Substances 0.000 claims abstract description 169
- 238000011084 recovery Methods 0.000 claims abstract description 86
- 238000003795 desorption Methods 0.000 claims abstract description 32
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 6
- 238000006073 displacement reaction Methods 0.000 claims description 44
- 239000000700 radioactive tracer Substances 0.000 claims description 23
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 17
- 238000000926 separation method Methods 0.000 claims description 17
- 230000035699 permeability Effects 0.000 claims description 8
- 239000011800 void material Substances 0.000 claims description 8
- 239000011148 porous material Substances 0.000 claims description 7
- 239000002808 molecular sieve Substances 0.000 claims description 5
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 5
- 230000005484 gravity Effects 0.000 claims description 3
- 239000001307 helium Substances 0.000 description 8
- 229910052734 helium Inorganic materials 0.000 description 8
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical group [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 8
- 230000008569 process Effects 0.000 description 7
- 230000008901 benefit Effects 0.000 description 5
- 230000009467 reduction Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- VXAUWWUXCIMFIM-UHFFFAOYSA-M aluminum;oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Al+3] VXAUWWUXCIMFIM-UHFFFAOYSA-M 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005065 mining Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004936 stimulating effect Effects 0.000 description 1
- 230000000638 stimulation Effects 0.000 description 1
- 238000010408 sweeping Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- 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
- E21B43/006—Production of coal-bed methane
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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
- E21B43/166—Injecting a gaseous medium; Injecting a gaseous medium and a liquid medium
- E21B43/168—Injecting a gaseous medium
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- 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
- E21B43/30—Specific pattern of wells, e.g. optimising the spacing of wells
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
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Abstract
The application discloses a nitrogen injection yield increasing method, and belongs to the technical field of coal bed methane development. The method comprises the following steps: selecting a coal bed gas well with better connectivity with other wells as a nitrogen injection well, and taking the coal bed gas well corresponding to the periphery as a gas production well; determining nitrogen injection equipment meeting the conditions according to the desorption pressure and the gas production rate of the coal bed gas of each gas production well in the gas production well group; and nitrogen is injected into the nitrogen injection well by adopting the nitrogen injection equipment, so that the coal bed gas is displaced to the gas production well group of at least one communicated gas production well through the nitrogen injection well, and the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the gas production amount of the gas production well are adjusted according to the gas production amount and the nitrogen content of the gas production well group, so that the injected nitrogen can drive the coal bed gas in the coal bed to enter the gas production well, the exploitation rate of the exploited coal bed gas is improved, and the recovery ratio is improved.
Description
Technical Field
The application relates to the technical field of coal bed gas exploitation, in particular to a nitrogen injection yield increasing method.
Background
In the process of exploiting the coal bed gas, if the gas production rate of the coal bed gas reaches 30%, the gas production rate of the gas production well can be rapidly reduced, and the gas production rate of the gas production well needs to be improved by adopting a yield increasing measure.
At present, water in a coal bed is usually pumped out through an oil pipe through a water suction pump, the pressure of the coal bed is reduced, so that coal bed gas is desorbed from the coal bed, then the coal bed gas is diffused and seeps into a shaft, and reaches a wellhead from an annular space between the oil pipe and a sleeve pipe, so that the coal bed gas is mined. However, the coal bed gas is mined in a drainage and pressure reduction mode, the gas production speed is low, and the recovery rate is low.
Disclosure of Invention
The embodiment of the application provides a nitrogen injection yield-increasing method, which can ensure that injected nitrogen can drive coal bed gas in a coal bed to enter a gas production well, improve the gas production speed of the coal bed gas and improve the recovery ratio. The technical scheme provided by the embodiment of the application is as follows:
on one hand, the embodiment of the application provides a nitrogen injection and yield increase method, wherein at least one gas production well and one nitrogen injection well in the same coal seam are communicated to form a nitrogen injection and production well group; the method comprises the following steps:
determining the maximum nitrogen injection amount of the nitrogen injection equipment according to the daily gas production amount of the injection-production well group;
determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coal bed gas in the coal bed;
controlling the nitrogen injection equipment to inject nitrogen into the nitrogen injection well so as to displace the coal bed gas in the coal bed into at least one corresponding gas production well, wherein the at least one gas production well produces the coal bed gas based on the injected nitrogen;
adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas recovery amount of each gas recovery well of the nitrogen injection equipment according to the volume of the nitrogen injected by the nitrogen injection equipment, the displacement plunging direction and the daily gas recovery amount and nitrogen content of each gas recovery well, wherein the displacement plunging direction is the direction in which the nitrogen injection well points to any gas recovery well;
and controlling the nitrogen injection equipment to inject nitrogen into the nitrogen injection well according to the adjusted nitrogen injection amount and the adjusted nitrogen injection pressure, wherein the at least one gas production well produces the coal bed gas based on the injected nitrogen and the adjusted daily gas production amount.
In one possible implementation, the method further comprises:
the coal bed is a coal bed with gas content higher than preset gas content and permeability higher than preset permeability.
In another possible implementation, the method further includes:
and the number of the gas recovery wells connected with the nitrogen injection well is higher than the preset number.
In another possible implementation manner, before determining the maximum nitrogen injection pressure of the nitrogen injection device according to the desorption pressure of the coal bed gas in the coal bed, the method further includes:
and determining the average value of the desorption pressure of the coal bed gas of the coal bed where each gas production well in the injection and production well group is located as the desorption pressure of the coal bed gas of the coal bed where the injection and production well group is located.
In another possible implementation, the method further includes:
and detecting the nitrogen content, the gas yield, the temperature and the wellhead pressure of the corresponding gas recovery well through a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor which are arranged on each gas recovery well in the injection-production well group.
In another possible implementation, the method further includes:
the nitrogen injection device injects a tracer into the nitrogen injection well;
and detecting the tracer in the at least one gas recovery well, and determining the direction of the nitrogen injection well pointing to the gas recovery well in which the tracer is detected as the displacement outburst direction.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of the nitrogen injected by the nitrogen injection equipment, the displacement plunging direction and the daily gas production rate and nitrogen content of each gas production well includes:
determining the ratio of the volume of the injected nitrogen to the pore volume of the coal bed as an injection void volume multiple;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production amount of each gas production well according to the injection void volume multiple.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of the nitrogen injected by the nitrogen injection equipment, the displacement plunging direction and the daily gas production rate and nitrogen content of each gas production well comprises:
determining the displacement area of the nitrogen injection well to the injection and production well group according to the displacement outburst direction, the injection void volume multiple, and the daily gas production rate and nitrogen content of each gas production well;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production rate of each gas production well according to the displacement area.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of the nitrogen injected by the nitrogen injection equipment, the displacement plunging direction and the daily gas production rate and nitrogen content of each gas production well includes:
determining a recovery ratio according to the total gas production amount of the injection-production well group and the total storage amount of the coal bed;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production amount of each gas production well according to the recovery ratio.
In another possible implementation manner, the coal bed gas produced by the injection and production well group is input into a separation device, and the method further comprises the following steps:
the separation equipment separates the coal bed gas and the nitrogen gas which are mined by the injection and production well group in a gravity sinking mode;
or the separation equipment separates the coal bed gas and the nitrogen gas which are extracted by the injection and production well group in a low-temperature deacidification mode;
or separating the coal bed gas and the nitrogen gas which are extracted by the injection and production well group by the separation equipment in a molecular sieve mode.
The beneficial effects that technical scheme that this application embodiment brought include at least:
the embodiment of the application provides a method for injecting nitrogen into a nitrogen injection well to improve the gas production rate of a gas production well group, nitrogen injection equipment meeting conditions is determined according to the desorption pressure and daily gas production rate of coal bed gas of each gas production well in the gas production well group, nitrogen is injected into the nitrogen injection well by adopting the nitrogen injection equipment to displace the coal bed gas in the coal bed into a gas production well communicated with the nitrogen injection well, the nitrogen injection amount and nitrogen injection pressure of the nitrogen injection equipment and the daily gas production rate of the gas production well can be adjusted according to the daily gas production rate of the gas production well, so that the injected nitrogen can drive the coal bed gas in the coal bed into the gas production well, the exploitation rate of the exploited coal bed gas is improved, and the recovery ratio is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, 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 description below are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of a method for stimulating production by injecting nitrogen provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of an injection-production well group provided in an embodiment of the present application.
Detailed Description
To make the objects, technical solutions and advantages of the present application more clear, embodiments of the present application will be described in further detail below with reference to the accompanying drawings.
The method provided by the embodiment of the application is applied to the field of coal bed gas exploitation, after coal bed gas in a coal bed is exploited for a period of time, the reserve volume of the coal bed gas stored in the coal bed can be reduced, and the yield of the coal bed gas is reduced.
FIG. 1 is a flow chart of a nitrogen injection stimulation method provided in an embodiment of the present application. Referring to fig. 1, the method includes:
101. and determining the maximum nitrogen injection amount of the nitrogen injection equipment according to the daily gas production amount of the injection-production well group.
In the embodiment, at least one gas production well in the same coal seam is communicated with one nitrogen injection well to form one injection and production well group. The method comprises the steps that coal bed gas can be displaced to at least one communicated gas recovery well through the nitrogen injection well, nitrogen in the nitrogen injection well is produced by the nitrogen injection equipment and injected into the nitrogen injection well, therefore, according to the method, the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection equipment are determined according to parameters of the at least one gas recovery well, the nitrogen injection equipment is selected according to the determined maximum nitrogen injection amount and the determined maximum nitrogen injection pressure, and then the nitrogen injection equipment is adopted to inject the nitrogen into the nitrogen injection well.
It should be noted that, the embodiments of the present application are only described by taking the injection-production well group as an example. In another embodiment, when the injection and production well group is selected, the centrally-located gas production well with good connectivity with surrounding wells and various geological conditions is converted into a nitrogen injection well, and other wells around the nitrogen injection well continue to be used as gas production wells to jointly form the injection and production well group.
Because one nitrogen injection well is communicated with one or more gas recovery wells, the nitrogen injection well displaces coal bed gas to one or more gas recovery wells so as to improve the daily gas recovery rate of each gas recovery well, the maximum nitrogen injection amount of the nitrogen injection equipment is determined according to the daily gas recovery rate of at least one gas recovery well, and the nitrogen injection equipment is selected according to the subsequently determined maximum nitrogen injection amount so as to ensure that the nitrogen injection amount of the nitrogen injection equipment can meet the requirement of the daily gas recovery rate of each gas recovery well.
The selected nitrogen injection device provides nitrogen injection amount larger than the maximum nitrogen injection amount so as to ensure enough nitrogen injection amount, and the nitrogen injection displacement of the nitrogen injection device is adjustable.
In a possible implementation manner, the total daily gas production amount of the daily gas production amount of each gas production well in at least one gas production well is obtained, and the product of the total daily gas production amount and a preset parameter is determined as the maximum nitrogen injection amount of the nitrogen injection equipment.
The preset parameter is greater than 1, and the preset parameter is set by an operator or set in other manners, which is not limited in the embodiments of the present application. For example, the predetermined parameter may be 1.1, 1.2, or other values.
For example, if the preset parameter is 1.1 and the sum of the daily gas production of at least one gas production well is x, the determined maximum nitrogen injection amount of the nitrogen injection equipment is 1.1x.
It should be noted that the daily gas production rate of the gas recovery well in the embodiment of the present application is a preset daily gas production rate, or the daily gas production rate of the gas recovery well is a daily gas production rate of the gas recovery well in a previous exploitation process.
Optionally, the coal seam in the embodiment of the present application is a coal seam having a gas content higher than a preset gas content and a permeability higher than a preset permeability.
Wherein, the preset gas content is set by an operator or set by other modes. In addition, the preset permeability is set by an operator or in other ways.
Optionally, the number of gas production wells to which the nitrogen injection well is connected is higher than a preset number. Wherein the preset number is set by an operator or in other manners. For example, the predetermined number may be 4, 5, or other values.
102. And determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coal bed gas in the coal bed.
In the embodiment of the application, the nitrogen injection equipment controls the pressure of injected nitrogen in the process of injecting nitrogen into the nitrogen injection well, and if the injection pressure is higher, the pressure required to be provided by the nitrogen injection equipment is higher, so that when nitrogen is injected into the nitrogen injection well through the nitrogen injection equipment, the maximum nitrogen injection pressure of the nitrogen injection equipment needs to be determined first, and the maximum nitrogen injection pressure of the nitrogen injection equipment is ensured to meet the requirements of the nitrogen injection process.
The coal bed gas in this application embodiment adsorbs in the coal seam, if need exploit the coal bed gas, then need control the pressure in the gas production well to make the pressure in the gas production well be less than the desorption pressure of coal bed gas, guarantee that the coal bed gas is desorbed from the coal seam, and then drive in the gas production well by nitrogen gas, adopt the gas production well to reach the effect of exploiting the coal bed gas. And when the maximum nitrogen injection pressure of the nitrogen injection equipment is determined, determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coal bed gas of the coal bed where the injection and production well group is located.
Optionally, the product of the desorption pressure of the injection-production well group and the preset multiple is determined as the maximum nitrogen injection pressure of the nitrogen injection device. Wherein the predetermined multiple is greater than 1, for example, the predetermined multiple is 1.5, 1.6, 1.7 or other values. For example, if the desorption pressure of the gas production well group is y and the preset multiple is 1.5, the maximum nitrogen injection pressure of the nitrogen injection equipment is 1.5y.
In a possible implementation manner, before the maximum nitrogen injection pressure of the nitrogen injection equipment is determined according to the desorption pressure of the injection and production well group, the desorption pressure of the injection and production well group needs to be determined, and the average value of the desorption pressure of the coal bed gas of the coal bed where each gas production well is located in at least one gas production well in the injection and production well group can be determined as the desorption pressure of the coal bed gas of the coal bed where the injection and production well group is located.
For example, the injection-production well group includes 3 gas production wells, and the desorption pressure of the coal bed gas in the coal bed in each gas production well is a, b, and c, respectively, so that the average value of the desorption pressures of the 3 gas production wells calculated is (a + b + c)/3.
It should be noted that, in the embodiment of the present application, the desorption pressure of each gas production well is obtained as follows: in the process of drainage and pressure reduction of the coal bed gas production well, along with the pressure reduction to a certain degree, the coal bed gas starts to be desorbed from the coal bed, and the bottom flowing pressure of the well when casing pressure is seen at the well mouth is determined as the desorption pressure of the well.
In addition, in the embodiment of the application, the coal seam where the gas production well is located has a fracture pressure, and if the pressure borne by the coal seam is greater than the fracture pressure of the coal seam, the coal seam is fractured, so that nitrogen injected through the nitrogen injection well enters the fractured coal seam, the injected nitrogen cannot displace the coal seam gas in the coal seam to enter the gas production well, the injected nitrogen is wasted, and the gas production rate of the gas production well cannot be improved, so that the determined maximum nitrogen injection pressure of the nitrogen injection device needs to be less than the fracture pressure of the coal seam.
The method for acquiring the fracture pressure of the coal seam in the embodiment of the application is as follows: and obtaining injection pressure drop test data from adjacent evaluation wells.
In one possible implementation, the nitrogen injection device is composed of a nitrogen production device and a nitrogen boosting device. The nitrogen making equipment is an air separation device with two groups of aluminum dioxide molecular sieves for alternate separation and reduction, and the nitrogen boosting equipment is equipment such as a reciprocating compressor, a screw compressor and the like.
It should be further noted that, in the embodiment of the present application, the gas production well further includes a displacement pressure, where the displacement pressure is an important index for increasing the gas production rate of the gas production well, the displacement pressure is a pressure for displacing the coal bed gas in the coal bed with the injected nitrogen gas, and the displacement pressure is smaller than a desorption pressure of the coal bed gas, so as to ensure that the gas production rate of the gas production well is increased.
For example, the displacement pressure is between one third and two thirds of the desorption pressure of the injection and production well group, so that the injected nitrogen can smoothly displace the coal bed gas in the coal bed, and further the gas production rate of the gas production well is ensured.
It should be noted that, the embodiments of the present application are only described by taking a nitrogen injection device connected to one nitrogen injection well as an example of determining the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection device. In another embodiment, the nitrogen injection device can be further connected with a plurality of nitrogen injection wells, when the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection device are determined, the sum of the daily gas production amounts of the gas production wells connected with each nitrogen injection well is multiplied by a coefficient larger than 1 to determine the maximum nitrogen injection amount of the nitrogen injection device, and the maximum desorption pressure is used as the maximum nitrogen injection pressure of the nitrogen injection device.
103. And controlling the nitrogen injection equipment, and injecting nitrogen into the nitrogen injection well so as to displace the coal bed gas in the coal bed into the corresponding at least one gas production well, wherein the at least one gas production well produces the coal bed gas based on the injected nitrogen.
In the embodiment of the application, after the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection equipment are determined, the nitrogen injection equipment meeting the requirements can be selected according to the maximum nitrogen injection amount and the maximum nitrogen injection pressure, and the nitrogen injection equipment is subsequently controlled to inject nitrogen into the nitrogen injection well.
The nitrogen injection equipment selected according to the mode meets the nitrogen injection requirement of the nitrogen injection well, so that the discharge capacity of injected nitrogen is enough, the coal bed is not broken due to overlarge injection pressure, and the gas production rate of the gas recovery well is ensured.
In the embodiment of the application, nitrogen is injected into the nitrogen injection well by controlling the nitrogen injection equipment, so that the nitrogen can enter the coal bed to displace coal bed gas into the gas production well, and the effect of exploiting the coal bed gas through the gas production well is realized.
104. And adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas recovery amount of each gas recovery well according to the volume of the nitrogen injected by the nitrogen injection equipment, the displacement outburst direction and the daily gas recovery amount and nitrogen content of each gas recovery well.
Wherein the displacement outburst direction is the direction of the nitrogen injection well pointing to any gas recovery well. Because one gas recovery well is connected with at least one gas recovery well, and one gas recovery well may be communicated with a plurality of gas recovery wells, each gas recovery well improves daily gas recovery under the action of nitrogen gas injected into the gas recovery well, and because of the structure of the coal seam, the daily gas recovery of the gas recovery well is less affected by partial nitrogen injection wells, so that the displacement plunging direction of the nitrogen injection equipment needs to be determined, the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment are adjusted according to the displacement plunging direction, and the daily gas recovery of each gas recovery well is guaranteed to be improved.
In the embodiment of the application, the nitrogen injection equipment injects nitrogen into the nitrogen injection well, the coal bed gas is displaced into the gas production well through the injected nitrogen, the gas production well produces the coal bed gas, the daily gas production rate of the gas production well and the nitrogen content of the produced coal bed gas can be recorded, and the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well of the nitrogen injection equipment can be adjusted subsequently according to the injection volume, the displacement outburst direction and the daily gas production rate and the nitrogen content of each gas production well of the nitrogen injection equipment.
In a possible implementation manner, each gas production well is provided with a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor, the nitrogen content detector is used for detecting the nitrogen content of the corresponding gas production well, the gas flowmeter is used for detecting the gas production rate of the corresponding gas production well, the temperature sensor is used for detecting the temperature of the corresponding gas production well, and the pressure sensor is used for detecting the wellhead pressure of the corresponding gas production well.
When the coal bed gas is mined through the gas recovery wells, the nitrogen content, the gas yield, the temperature and the wellhead pressure in each gas recovery well can be respectively detected through the nitrogen content detector, the gas flowmeter, the temperature sensor and the pressure sensor in each gas recovery well, and the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas recovery amount of each gas recovery well are adjusted according to the detected parameters.
In another possible implementation manner, the nitrogen injection device injects a tracer into the nitrogen injection well, the tracer enters the gas production well through the nitrogen injection well, the tracer in at least one gas production well is detected, and the direction of the nitrogen injection well pointing to the gas production well in which the tracer is detected is determined as a displacement plunging direction.
The tracer is helium or other inert gas, and the embodiment of the present application is not limited.
Optionally, one nitrogen injection well is connected with a plurality of gas recovery wells, then the nitrogen injection equipment injects a tracer into the nitrogen injection well, the tracer in at least one gas recovery well is detected, and the direction of the nitrogen injection well pointing to the gas recovery well in which the tracer is detected is determined as the displacement plunging-in direction.
Optionally, under the condition that a plurality of nitrogen injection wells are simultaneously communicated with one gas production well, firstly injecting a tracer into a first nitrogen injection well, detecting whether the tracer exists in the gas production well or not after a preset interval time, then injecting the tracer into a second nitrogen injection well, detecting whether the tracer exists in the gas production well or not after the preset interval time, and so on, injecting the tracer into a next nitrogen injection well every preset interval time, detecting whether the tracer exists or not after the preset interval time until the gas production well detects the tracer, and determining the direction of the previous nitrogen injection well to the gas production well as the displacement plunging-in direction.
In another possible implementation manner, the ratio of the volume of the injected nitrogen to the pore volume of the coal seam is determined as an injection void volume multiple, and the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well of the nitrogen injection equipment are adjusted according to the injection void volume multiple.
In the embodiment of the application, the pore volume of the coal bed is fixed, and after the pore volume of the coal bed is determined, nitrogen can be injected into the coal bed according to the volume which is a preset multiple of the pore volume, so that the volume of the injected nitrogen is enough, and the daily gas production rate of a gas production well is ensured.
The preset multiple is greater than 1, for example, the preset multiple is 3, 4, 5, 6 or other values.
In another possible implementation mode, the displacement area of the nitrogen injection well to at least one gas production well is determined according to the displacement outburst direction and the gas production rate and nitrogen content of each gas production well, and the nitrogen injection amount, nitrogen injection pressure and the gas production rate of each gas production well of the nitrogen injection equipment are adjusted according to the displacement area.
Wherein the displacement area is the area of the coal bed displaced by the nitrogen injected into the nitrogen injection well. If the displacement area determined in the embodiment of the application is larger, the effect of the injected nitrogen on improving the gas production rate of the gas production well is better.
In another possible implementation manner, the recovery ratio is determined according to the total gas production rate of the injection and production well group and the total storage capacity of the coal bed, and the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production rate of each gas production well are adjusted according to the recovery ratio.
In the embodiment of the application, if the volume of the nitrogen injection device for injecting nitrogen is small and the nitrogen content of each gas production well is low, it indicates that the nitrogen injection amount of the nitrogen injection device is low, at this time, the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection device are increased, and the daily gas production amount of each gas production well is not changed, so that the nitrogen content in the gas production well is increased after the subsequent nitrogen injection device injects nitrogen into the nitrogen injection well based on the increased nitrogen injection amount.
For another example, in the multiple gas production wells tested at this time, if the gas production of the first gas production well and the second gas production well is high, and the nitrogen content is high, and the gas production of the third gas production well and the fourth gas production well is low, and the nitrogen content is also low, the displacement outburst direction is the direction in which the nitrogen injection well points to the first gas production well and the second gas production well. At this time, the daily gas production rate of the first gas production well and the second gas production well should be reduced, so that the injected nitrogen is displaced towards the third gas production well and the fourth gas production well, and the gas production rate of the third gas production well and the fourth gas production well is improved. Meanwhile, the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment are kept unchanged.
105. And controlling the nitrogen injection equipment to inject nitrogen into the nitrogen injection well according to the adjusted nitrogen injection amount and the adjusted nitrogen injection pressure, and exploiting the coal bed gas by at least one gas production well based on the injected nitrogen and the adjusted daily gas production amount.
In the embodiment of the application, the adjusted nitrogen injection amount and nitrogen injection pressure of the nitrogen injection equipment and the adjusted gas production rate of the gas production well more meet the exploitation requirements, and the gas production rate of each gas production well can be ensured.
The first point to be noted is that the present embodiment is described only by taking the example of extracting coal bed gas through a gas recovery well. In another embodiment, the coal bed gas produced by the injection and production well group is input into the separation equipment, and the coal bed gas is separated from the nitrogen through the separation equipment, so that the content of the nitrogen in the coal bed gas is reduced, and the purity of the coal bed gas is improved.
Optionally, in the embodiment of the present application, the mined coal bed methane and the nitrogen gas can be separated in any one of the following manners:
(1) The separation equipment separates the coal bed gas and the nitrogen gas which are mined by the injection and production well group in a gravity settling mode.
(2) The separation equipment separates the coal bed gas and the nitrogen gas which are exploited by the injection and production well group in a low-temperature deacidification mode.
(3) The separation equipment separates the coal bed gas and the nitrogen gas which are mined by the injection and production well group in a molecular sieve mode.
The second point to be described is that, since the embodiment of the present application generates a cost in the process of injecting nitrogen into the gas production well, the cost of the injected nitrogen needs to be acquired, and then the value of the coal bed gas obtained by mining through injecting nitrogen is acquired, if the value of the acquired coal bed gas is greater than the cost of the injected nitrogen, the coal bed gas is continuously mined in the above manner, and if the value of the acquired coal bed gas is not greater than the cost of the injected nitrogen, the coal bed gas is stopped being continuously mined in the above manner.
The embodiment of the application provides a method for injecting nitrogen into a nitrogen injection well to improve the yield of coal bed gas of a gas recovery well, wherein nitrogen injection equipment meeting conditions is determined according to desorption pressure and daily gas recovery rate of the coal bed gas of each gas recovery well in a gas recovery well group, the nitrogen injection equipment is adopted to inject nitrogen into the nitrogen injection well so as to displace the coal bed gas to at least one communicated gas recovery well through the nitrogen injection well, and the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas recovery rate of the gas recovery well can be adjusted according to the daily gas recovery rate of the gas recovery well, so that the injected nitrogen can drive the coal bed gas in the coal bed to enter the gas recovery well, the coal bed gas recovery rate is improved, and the recovery ratio is improved.
In addition, the coal bed gas and the nitrogen are separated through the separation equipment, so that the purity of the coal bed gas obtained through mining can be improved, and the coal bed gas meets the requirement of the quality standard of commercial gas.
In the following, the present application will be described taking three gas injection and production well groups as an example. In the application, as shown in FIG. 2, 1-1, 1-2 and 1-3 are adjacent three nitrogen injection wells, 2-1, 2-2, 2-4, 2-5, 2-6, 2-7, 2-8, 2-9, 2-10, 2-11, 2-12 and 2-13 are gas production wells corresponding to the nitrogen injection wells, wherein 1-1 and 2-1, 2-2, 2-3, 2-4, 2-5 and 2-6 are a production injection well group and are named as an injection well group 1; the injection and production well group 2 consists of nitrogen injection wells 1-2 and gas production wells 2-5, 2-6, 2-7, 2-8, 2-9 and 2-10; and the injection and production well group 3 consists of nitrogen injection wells 1-3 and gas production wells 2-4, 2-5, 2-10, 2-11, 2-12 and 2-13.
The method provided by the embodiment of the application is implemented by adopting the following process:
1. selecting a region: a high-yield well in a high-permeability region is selected to be in a Qin water basin fan village block capable of reducing yield rapidly, no fault or coal mine exists nearby, the gas content in the zone is 21 cubic meters per ton, and the permeability is 0.2 millidarcy.
2. Selecting a coal bed: and selecting a coal bed which is uniformly distributed, has the thickness of about 5 meters and is completely communicated with the well.
3. Selecting a nitrogen injection well and a gas recovery well: and (3) selecting 16 wells belonging to the coal bed in the step (2), namely coal bed gas wells which are put into drainage and production after fracturing, wherein 1-1, 1-2 and 1-3 in the central position are nitrogen injection wells, 6 gas production wells are arranged corresponding to each nitrogen injection well, 2-5 wells are gas production wells of three injection and production well groups, and 2-4, 2-6 and 2-10 wells are gas production wells of two injection and production well groups.
4. Burst pressure: according to the injection pressure drop test data of adjacent evaluation wells, the fracture pressure is 18 MPa; the fracture construction curve of the 16-hole well shows that the fracture pressure is 16-21 MPa, and the analysis determines that the fracture pressure of the area of the coal bed is 17 MPa.
5. Desorption pressure: the desorption pressure values of all wells of the three injection-production well groups in the area are close, and the arithmetic mean value of 2.6 MPa of each gas-production well is taken as the desorption pressure of the coal bed area for facilitating equipment type selection and daily management.
6. Nitrogen injection pressure: the coal bed displacement pressure is set at 1.7 mpa by one-third to two-thirds of the desorption pressure. The pressure of nitrogen injection at the well head was set to 3.9 MPa at 1.5 times the desorption pressure of 2.6 MPa. The nitrogen injection pressure is 17 MPa lower than the coal bed fracture pressure.
7. Equipment type selection: the nitrogen injection equipment consists of nitrogen making equipment and nitrogen boosting equipment. An aluminum dioxide molecular sieve empty device is selected as nitrogen making equipment. A reciprocating compressor is selected as nitrogen boosting equipment. The production allocation of 13 gas recovery wells is 2000 cubic meters per well day, the production allocation of the region is 26000 cubic meters, and the maximum displacement of nitrogen production and pressure boosting equipment is 31000 cubic meters; the nitrogen injection pressure is 3.9 MPa multiplied by 1.1 factor, and the discharge pressure of the nitrogen injection equipment is selected to be 4.3 MPa. One set of nitrogen injection equipment simultaneously supplies nitrogen to the adjacent three nitrogen injection wells. After the implementation, the actual nitrogen injection pressure is slowly increased from low to high and gradually stabilized at 1.9 MPa to 2.6 MPa.
8. Detecting nitrogen gas in a gas recovery well: a nitrogen content detector is arranged in front of a metering valve group flowmeter of each gas production well, and the nitrogen content and the parameters such as gas production, pressure, temperature and the like output by each well are collected and transmitted to a database.
9. Injecting a tracer: in order to judge the main force direction of nitrogen displacement, helium is injected into the well mouths of the three nitrogen injection wells of 1-1, 1-2 and 1-3 at intervals of 5 months in sequence, and 100 cubic meters of helium is injected within 24 hours each time. The time of arrival of helium at the gas recovery well was estimated at 100 days, and gas recovery wells containing nitrogen were sampled to detect helium from the gas recovery wells from day 90.
10. Dynamic analysis: according to the corresponding relation and the connectivity of the nitrogen injection well and the gas recovery well, the gas recovery well in the northeast and southwest directions has high gas production and high nitrogen content, the tracer helium is detected early, and the gas recovery wells in the southeast and northwest directions have low yield and no helium is detected. Analysis suggests that the northeast and southwest directions are the directions of greatest principal stress along which fracture fractures tend to propagate, so nitrogen and helium are seen earlier and are the principal directions of displacement. And a dynamic adjustment scheme design is made, the production allocation of the gas production wells in the northeast and southwest directions is adjusted and reduced, the nitrogen injection amount is unchanged, and the driving and sweeping area is enlarged.
11. And (3) injection and production balance adjustment, namely reducing the production allocation of the high-nitrogen-content gas production wells 2-2, 2-4, 2-9 and 2-11 to less than 2000 cubic meters of daily production according to the dynamic analysis result, inhibiting the nitrogen gas output, and displacing the nitrogen gas towards the northwest and southeast directions, so that the higher displacement speed is kept, the nitrogen gas is prevented from locally and rapidly rushing in, and injection and production balance is achieved.
12. And analyzing the sweep area, the injection pore volume multiple and the recovery ratio.
13. And (3) denitrification treatment: and when the nitrogen content of the coal bed gas is higher than the quality requirement of the output product gas, the coal bed gas enters separation equipment for low-temperature deacidification to remove the nitrogen in the coal bed gas.
14. And (3) economic benefit analysis: and calculating the comprehensive cost of nitrogen injection, gas production, denitrification, maintenance and the like, comparing and analyzing the comprehensive cost with the sales income of the coal bed gas, and judging the economic benefit. If the economic benefit is available, continuing to inject nitrogen for displacement, and circulating the steps from 8 to 14. If no economic benefit exists, the nitrogen injection is finished, and the well is shut in after the coal bed pressure energy is naturally released.
The above description is only for facilitating the technical solution of the present application to be understood by those skilled in the art, and is not intended to limit the present application. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (10)
1. The nitrogen injection production increasing method is characterized in that at least one gas production well and one nitrogen injection well in the same coal seam are communicated to form a nitrogen injection and production well group; the method comprises the following steps:
determining the maximum nitrogen injection amount of the nitrogen injection equipment according to the daily gas production amount of the injection-production well group;
determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coal bed gas in the coal bed;
controlling the nitrogen injection equipment to inject nitrogen into the nitrogen injection well so as to displace the coal bed gas in the coal bed into at least one corresponding gas production well, wherein the at least one gas production well produces the coal bed gas based on the injected nitrogen;
adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well of the nitrogen injection equipment according to the volume of nitrogen injected by the nitrogen injection equipment, the displacement plunging direction and the daily gas production amount and nitrogen content of each gas production well, wherein the displacement plunging direction is the direction in which the nitrogen injection well points to any gas production well;
and controlling the nitrogen injection equipment to inject nitrogen into the nitrogen injection well according to the adjusted nitrogen injection amount and the adjusted nitrogen injection pressure, wherein the at least one gas production well produces the coal bed gas based on the injected nitrogen and the adjusted daily gas production amount.
2. The method of claim 1, further comprising:
the coal bed is a coal bed with gas content higher than preset gas content and permeability higher than preset permeability.
3. The method of claim 1, further comprising:
and the number of the gas recovery wells connected with the nitrogen injection well is higher than the preset number.
4. The method of claim 1, wherein prior to determining the maximum nitrogen injection pressure of the nitrogen injection apparatus from the desorption pressure of coal bed gas in the coal bed, the method further comprises:
and determining the average value of the desorption pressure of the coal bed gas of the coal bed where each gas production well in the injection and production well group is located as the desorption pressure of the coal bed gas of the coal bed where the injection and production well group is located.
5. The method of claim 1, further comprising:
and detecting the nitrogen content, the gas production rate, the temperature and the wellhead pressure of the corresponding gas production well through a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor which are arranged on each gas production well in the injection and production well group.
6. The method of claim 1, further comprising:
the nitrogen injection device injects a tracer into the nitrogen injection well;
and detecting the tracer in the at least one gas recovery well, and determining the direction of the nitrogen injection well pointing to the gas recovery well in which the tracer is detected as the displacement outburst direction.
7. The method of claim 1, wherein the adjusting of the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of nitrogen injected by the nitrogen injection equipment, the displacement kick-in direction and the daily gas production rate and nitrogen content of each gas production well comprises:
determining the ratio of the volume of the injected nitrogen to the pore volume of the coal bed as an injection void volume multiple;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production rate of each gas production well according to the injection void volume multiple.
8. The method of claim 1, wherein the adjusting of the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of nitrogen injected by the nitrogen injection equipment, the displacement kick-in direction and the daily gas production rate and nitrogen content of each gas production well comprises:
determining the displacement area of the nitrogen injection well to the injection and production well group according to the displacement outburst direction, the injection void volume multiple, and the daily gas production rate and nitrogen content of each gas production well;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production rate of each gas production well according to the displacement area.
9. The method of claim 1, wherein the adjusting of the nitrogen injection amount, the nitrogen injection pressure and the daily gas production rate of each gas production well according to the volume of nitrogen injected by the nitrogen injection equipment, the displacement kick-in direction and the daily gas production rate and nitrogen content of each gas production well comprises:
determining a recovery ratio according to the total gas production rate of the injection and production well group and the total storage capacity of the coal bed;
and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas recovery amount of each gas recovery well according to the recovery ratio.
10. The method of claim 1, wherein the coalbed methane produced by the injection and production well group is input into a separation device, the method further comprising:
the separation equipment separates the coal bed gas and the nitrogen gas which are extracted by the injection and production well group in a gravity settling mode;
or the separation equipment separates the coal bed gas and the nitrogen gas which are extracted by the injection and production well group in a low-temperature deacidification mode;
or separating the coal bed gas and the nitrogen gas which are extracted by the injection and production well group by the separation equipment in a molecular sieve mode.
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