CN115217443B - Nitrogen injection yield increasing method - Google Patents
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- CN115217443B CN115217443B CN202110420078.9A CN202110420078A CN115217443B CN 115217443 B CN115217443 B CN 115217443B CN 202110420078 A CN202110420078 A CN 202110420078A CN 115217443 B CN115217443 B CN 115217443B
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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 412
- 238000002347 injection Methods 0.000 title claims abstract description 346
- 239000007924 injection Substances 0.000 title claims abstract description 346
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000007789 gas Substances 0.000 claims abstract description 349
- 238000004519 manufacturing process Methods 0.000 claims abstract description 313
- 239000003245 coal Substances 0.000 claims abstract description 107
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 90
- 238000003795 desorption Methods 0.000 claims abstract description 32
- 238000006073 displacement reaction Methods 0.000 claims description 40
- 239000000700 radioactive tracer Substances 0.000 claims description 23
- 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
- 238000005065 mining Methods 0.000 claims description 5
- 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
- 238000011084 recovery Methods 0.000 abstract description 12
- 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
- 230000008901 benefit Effects 0.000 description 7
- 239000011148 porous material Substances 0.000 description 6
- 230000001276 controlling effect Effects 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 239000000243 solution Substances 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
- 238000010408 sweeping Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 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
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000000638 stimulation Effects 0.000 description 1
Classifications
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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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- 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
- E21B43/16—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
-
- 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
-
- 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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- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Environmental & Geological Engineering (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
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Abstract
The application discloses a nitrogen injection yield increasing method, and belongs to the technical field of coalbed methane exploitation. The method comprises the following steps: selecting one coal-bed gas well with better connectivity with other wells as a nitrogen injection well, and selecting the coal-bed gas wells with corresponding periphery as gas production wells; determining nitrogen injection equipment meeting the conditions according to the desorption pressure and the gas production amount of the coalbed methane 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, so that coal bed gas is displaced to a gas production well group of at least one communicated gas production well by the nitrogen injection well, and the nitrogen injection amount, the nitrogen injection pressure and the gas production amount of the nitrogen injection equipment 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 coal bed gas production rate is improved, and the recovery ratio is improved.
Description
Technical Field
The application relates to the technical field of coalbed methane exploitation, in particular to a nitrogen injection yield increasing method.
Background
In the process of exploiting the coalbed methane, if the gas production of the coalbed methane reaches 30%, the gas production of the gas production well can be rapidly reduced, and the gas production 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 by a water suction pump, so that the pressure of the coal bed is reduced, the coal bed gas is desorbed from the coal bed, then the coal bed gas is diffused and flows to a shaft, and an annular space between the oil pipe and a sleeve reaches a wellhead, so that the exploitation of the coal bed gas is realized. But coal bed gas is mined by means of drainage and depressurization, so that the gas mining speed is low, and the recovery ratio is low.
Disclosure of Invention
The embodiment of the application provides a nitrogen injection yield increasing method, which ensures that injected nitrogen can drive coalbed methane in a coal bed to enter a gas production well, improves the gas production speed of the coalbed methane and improves the recovery ratio. The technical scheme provided by the embodiment of the application is as follows:
in one aspect, the embodiment of the application provides a nitrogen injection and production increase method, wherein at least one gas production well in the same coal seam is communicated with one nitrogen injection well 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 well group;
Determining the maximum nitrogen injection pressure of the nitrogen injection device according to the desorption pressure of the coalbed methane in the coalbed;
Controlling the nitrogen injection equipment, injecting nitrogen into the nitrogen injection well 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 is used for exploiting the coal bed gas based on the injected nitrogen;
According to the volume of nitrogen injected by the nitrogen injection device, the displacement and burst direction, the daily gas production amount and the nitrogen content of each gas production well, the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well of the nitrogen injection device are adjusted, and the displacement and burst direction is the direction of the nitrogen injection well pointing 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, and mining the coal bed gas by at least one gas production well based on the injected nitrogen and the adjusted daily gas production.
In one possible implementation, the method further includes:
the coal seam is a coal seam with gas content higher than preset gas content and permeability higher than preset permeability.
In another possible implementation, the method further includes:
The number of the gas production wells connected with the nitrogen injection wells is higher than the preset number.
In another possible implementation manner, before the determining the maximum nitrogen injection pressure of the nitrogen injection device according to the desorption pressure of the coalbed methane in the coalbed, the method further includes:
and determining the average value of the desorption pressure of the coalbed methane of the coalbed where each gas production well is located in the injection and production well group as the desorption pressure of the coalbed methane of the coalbed 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 production wells through a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor which are arranged in each gas production well in the injection and 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 production well, and determining the direction of the nitrogen injection well to the gas production well with the detected tracer as the displacement and burst direction.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well according to the volume of the nitrogen injected by the nitrogen injection device, the displacement kick direction and the daily gas production amount and the 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 seam as an injected void volume multiple;
And 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 injection void volume multiple.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well according to the volume of the nitrogen injected by the nitrogen injection device, the displacement kick direction and the daily gas production amount and the nitrogen content of each gas production well includes:
Determining the displacement area of the nitrogen injection well for the injection and production well group according to the displacement and outburst direction, the injection void volume multiple, the daily gas production amount and the nitrogen content of each gas production well;
And 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 displacement area.
In another possible implementation manner, the adjusting the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well according to the volume of the nitrogen injected by the nitrogen injection device, the displacement kick direction and the daily gas production amount and the nitrogen content of each gas production well includes:
Determining the recovery ratio according to the total gas production of the injection well group and the total storage capacity of the coal seam;
And 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 recovery ratio.
In another possible implementation manner, the coalbed methane produced by the injection and production well group is input into a separation device, and the method further comprises:
The separation equipment separates the coal bed gas mined by the injection well group from the nitrogen in a gravity sinking mode;
or the separation equipment separates the coal bed gas mined by the injection well group from the nitrogen in a low-temperature deacidification mode;
Or the separation equipment separates the coal bed gas mined by the injection well group from the nitrogen in a molecular sieve mode.
The technical scheme provided by the embodiment of the application has the beneficial effects that at least:
The embodiment of the application provides a method for injecting nitrogen into a nitrogen injection well to improve the gas production of a gas production well group, which comprises the steps of determining nitrogen injection equipment meeting the conditions according to the desorption pressure and daily gas production of coal bed gas of each gas production well in the gas production well group, injecting nitrogen into the nitrogen injection well by using the nitrogen injection equipment, displacing the coal bed gas in a coal bed into the gas production well communicated with the nitrogen injection well, and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production of the gas production well according to the daily gas production of the gas production well so as to ensure that the injected nitrogen can drive the coal bed gas in the coal bed into the gas production well, thereby improving the exploitation rate of the coal bed gas and the recovery ratio.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a nitrogen injection stimulation method provided by an embodiment of the application;
Fig. 2 is a schematic structural diagram of an injection well group according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the embodiments of the present application will be described in further detail 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 the coal bed gas in the coal bed is exploited for a period of time, the reserve of the coal bed gas stored in the coal bed can be reduced, so that the yield of the coal bed gas is reduced.
FIG. 1 is a flow chart of nitrogen injection and yield increase provided by an embodiment of the 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 and production well group.
In the embodiment of the application, 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 and the device have the advantages that coal bed gas can be displaced to at least one communicated gas production well through the nitrogen injection well, nitrogen in the nitrogen injection well is produced by the nitrogen injection device and is injected into the nitrogen injection well, so that the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection device are determined according to the parameters of the at least one gas production well, the nitrogen injection device is selected according to the determined maximum nitrogen injection amount and the maximum nitrogen injection pressure, and the nitrogen is injected into the nitrogen injection well by the nitrogen injection device.
It should be noted that, the embodiments of the present application are only described directly by taking the injection well group as an example. In another embodiment, when selecting the injection and production well group, the production well which has good connectivity with surrounding wells and proper geological conditions and is located in the central position is converted into a nitrogen injection well, and other wells located around the nitrogen injection well continue to serve as production wells to form one injection and production well group together.
Because one nitrogen injection well is communicated with one or more gas production wells, the coal bed gas is displaced from the nitrogen injection well to the one or more gas production wells so as to improve the daily gas production of each gas production well, the maximum nitrogen injection amount of the nitrogen injection device is determined according to the daily gas production of at least one gas production well, and the nitrogen injection device is selected according to the subsequently determined maximum nitrogen injection amount so as to ensure that the nitrogen injection amount of the nitrogen injection device can meet the daily gas production requirement of each gas production well.
The nitrogen injection amount provided by the selected nitrogen injection equipment is larger than the maximum nitrogen injection amount so as to ensure enough nitrogen injection amount, and the nitrogen injection displacement of the nitrogen injection equipment is adjustable.
In one possible implementation, a daily gas production sum of daily gas production for each of the at least one gas production well is obtained, and a product of the daily gas production sum and a preset parameter is determined as a maximum nitrogen injection amount of the nitrogen injection device.
The preset parameter is greater than 1, and the preset parameter is set by an operator or set by other modes, which is not limited in the embodiment of the present application. For example, the preset parameter is 1.1, 1.2 or other values.
For example, if the preset parameter is 1.1 and the sum of the daily gas production amounts of at least one gas production well is x, the determined maximum nitrogen injection amount of the nitrogen injection device is 1.1x.
It should be noted that, the daily gas production amount of the gas production well in the embodiment of the present application is a preset daily gas production amount, or the daily gas production amount of the gas production well is a daily gas production amount of the gas production well in the previous production process.
Optionally, the coal seam in the embodiment of the present application is a coal seam with a gas content higher than a preset gas content and a permeability higher than a preset permeability.
Wherein the preset air content is set by an operator or set in other manners. In addition, the preset permeability is set by the operator, or otherwise.
Optionally, the number of gas production wells connected by the nitrogen injection well is higher than a preset number. Wherein the preset number is set by an operator or otherwise. For example, the preset number is 4,5 or other value.
102. And determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coalbed methane in the coal bed.
In the embodiment of the application, the nitrogen injection device controls the pressure of injecting nitrogen in the process of injecting nitrogen into the nitrogen injection well, and if the injection pressure is larger, the pressure which needs to be provided by the nitrogen injection device is larger, so that when the nitrogen is injected into the nitrogen injection well through the nitrogen injection device, the maximum nitrogen injection pressure of the nitrogen injection device needs to be determined first, and the maximum nitrogen injection pressure of the nitrogen injection device is ensured to meet the requirement of the nitrogen injection process.
The embodiment of the application has the advantages that the coalbed methane is adsorbed in the coalbed, if the coalbed methane needs to be mined, the pressure in the gas-producing well needs to be controlled so that the pressure in the gas-producing well is smaller than the desorption pressure of the coalbed methane, the coalbed methane is ensured to be desorbed from the coalbed, and then the nitrogen is displaced into the gas-producing well, so that the effect of mining the coalbed methane is achieved by adopting the gas-producing well. And when determining the maximum nitrogen injection pressure of the nitrogen injection equipment, determining the maximum nitrogen injection pressure of the nitrogen injection equipment according to the desorption pressure of the coalbed methane of the coalbed where the injection and production well group is located.
Optionally, the product of the desorption pressure of the injection and production well group and the preset multiple is determined as the maximum nitrogen injection pressure of the nitrogen injection device. Wherein the preset multiple is greater than 1, for example, the preset 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 determined maximum nitrogen injection pressure of the nitrogen injection device is 1.5y.
In one possible implementation manner, before determining the maximum nitrogen injection pressure of the nitrogen injection device according to the desorption pressure of the injection well group, determining the desorption pressure of the injection well group is needed, and an average value of the desorption pressures of the coalbed methane of the coalbed where each of the at least one gas well in the injection well group is located can be determined as the desorption pressure of the coalbed methane of the coalbed where the injection well group is located.
For example, the injection and production well group comprises 3 gas production wells, the desorption pressure of the coalbed methane in the coal bed where each gas production well is located is a, b and c, and the calculated average value of the desorption pressures of the 3 gas production wells 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 drainage depressurization process of the coalbed methane gas production well, as the pressure is reduced to a certain degree, the coalbed methane starts to desorb from the coalbed, and the bottom hole flow pressure when the wellhead starts to see the casing pressure is determined as the desorption pressure of the well.
In addition, in the embodiment of the application, the coal bed where the gas production well is located has fracture pressure, if the pressure born by the coal bed is greater than the fracture pressure of the coal bed, the coal bed is fractured, and then nitrogen injected through the nitrogen injection well enters the fractured coal bed, the injected nitrogen cannot displace coal bed gas in the coal bed to enter the gas production well, the injected nitrogen is wasted, and the gas production amount of the gas production well cannot be improved, so that the determined maximum nitrogen injection pressure of the nitrogen injection equipment needs to be smaller than the fracture pressure of the coal bed.
The method for acquiring the fracture pressure of the coal seam in the embodiment of the application comprises the following steps: and obtaining injection pressure drop test data of adjacent evaluation wells.
In one possible implementation, the nitrogen injection apparatus is composed of a nitrogen production apparatus and a nitrogen pressure boosting apparatus. The nitrogen production equipment is an air separation device for alternately separating and reducing two groups of aluminum dioxide molecular sieves, and the nitrogen boosting equipment is a reciprocating compressor, a screw compressor and the like.
It should be 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 of the gas production well, and the displacement pressure is the pressure of injected nitrogen to displace coalbed methane in the coalbed, and is less than the desorption pressure of the coalbed methane, so as to ensure that the gas production 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 as to ensure that the injected nitrogen can smoothly displace the coalbed methane in the coalbed, and further ensure the gas production of the gas production well.
The embodiment of the application is only exemplified by a nitrogen injection device connected with one nitrogen injection well, and the maximum nitrogen injection quantity and the maximum nitrogen injection pressure of the nitrogen injection device are determined. In another embodiment, the nitrogen injection device can be connected with a plurality of nitrogen injection wells, and when determining the maximum nitrogen injection amount and the maximum nitrogen injection pressure of the nitrogen injection device, 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 taken as the maximum nitrogen injection pressure of the nitrogen injection device.
103. And controlling nitrogen injection equipment, injecting nitrogen into the nitrogen injection well 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 is used for exploiting 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 device are determined, the nitrogen injection device meeting the requirements can be selected according to the maximum nitrogen injection amount and the maximum nitrogen injection pressure, and then the nitrogen injection device is controlled to inject nitrogen into the nitrogen injection well.
According to the nitrogen injection equipment selected in the mode, the nitrogen injection requirement of the nitrogen injection well is met, so that the injected nitrogen is ensured to have enough discharge capacity, the coal seam is not broken due to overlarge injected pressure, and the gas production amount of the gas production well is ensured.
In the embodiment of the application, the 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 the 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, the nitrogen injection pressure and the daily gas production amount of each gas production well according to the volume of nitrogen injected by the nitrogen injection device, the displacement plunging direction and the daily gas production amount and the nitrogen content of each gas production well.
The displacement and outburst direction is the direction that the nitrogen injection well points to any gas production well. Because one nitrogen injection well is connected with at least one gas production well, and the gas production wells are possibly communicated with a plurality of nitrogen injection wells, each gas production well improves daily gas production under the effect of nitrogen injection of the nitrogen injection well, and the influence of part of the nitrogen injection wells on the daily gas production of the gas production well is small due to the structure of a coal seam, the displacement and outburst direction of the nitrogen injection device is required to be determined, and then the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection device are adjusted according to the displacement and outburst direction, so that the daily gas production of each gas production well is guaranteed to be improved.
In the embodiment of the application, nitrogen is injected into a nitrogen injection well by nitrogen injection equipment, coal bed gas is displaced into a gas production well by the injected nitrogen, the gas production well is used for producing the coal bed gas, the daily gas production of the gas production well and the nitrogen content in the produced coal bed gas can be recorded, and the nitrogen injection amount, the nitrogen injection pressure and the daily gas production of each gas production well of the nitrogen injection equipment can be adjusted according to the injected volume, the displacement and the outburst direction of the nitrogen injection equipment and the daily gas production and the nitrogen content of each gas production well.
In one possible implementation manner, each gas production well is provided with a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor, wherein 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 yield 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 coal bed gas is mined through the gas production wells, the embodiment of the application can respectively detect the nitrogen content, the gas production amount, the temperature and the wellhead pressure in each gas production well through the nitrogen content detector, the gas flowmeter, the temperature sensor and the pressure sensor in each gas production well, and then 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 are adjusted according to the detected parameters.
In another possible implementation, 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 to the gas production well in which the tracer is detected is determined as the displacement kick direction.
Wherein the tracer is helium or other inert gases, and embodiments of the application are not limited.
Optionally, one nitrogen injection well is connected with a plurality of gas production wells, the nitrogen injection device injects tracer in the nitrogen injection well, the tracer in at least one gas production well is detected, and the direction of the nitrogen injection well to the gas production well in which the tracer is detected is determined as the displacement plunge 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 the first nitrogen injection well, detecting whether the tracer exists in the gas production well after a preset time interval, then injecting the tracer into the second nitrogen injection well, detecting whether the tracer exists in the gas production well after a preset time interval, and the like, injecting the tracer into the next nitrogen injection well every preset time interval, detecting whether the tracer exists after a preset time interval until the tracer is detected by the gas production well, and determining that the direction of the previous nitrogen injection well to the gas production well is a displacement burst direction.
In another possible implementation, the ratio of the volume of 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 amount of each gas production well of the nitrogen injection device 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 injected nitrogen is ensured to be sufficient in volume, and the daily gas production of a gas production well is ensured.
Wherein the preset multiple is greater than 1, for example, the preset multiple is 3, 4, 5, 6 or other values.
In another possible implementation manner, the displacement area of at least one gas production well by the nitrogen injection well is determined according to the displacement plunge direction and the gas production and nitrogen content of each gas production well, and the nitrogen injection amount, the nitrogen injection pressure and the gas production of each gas production well of the nitrogen injection device are adjusted according to the displacement area.
The displacement area is the area of the coal seam displaced by the nitrogen injected by the nitrogen injection well. If the displacement area determined in the embodiment of the application is larger, the injected nitrogen has better effect on improving the gas production of the gas production well.
In another possible implementation, the recovery ratio is determined according to the total gas production of the injection and production well group and the total storage capacity of the coal seam, and the nitrogen injection amount, the nitrogen injection pressure and the daily gas production of each gas production well of the nitrogen injection equipment are adjusted according to the recovery ratio.
In the embodiment of the application, if the volume of nitrogen injected by the nitrogen injection device is small and the nitrogen content of each gas production well is low, the nitrogen injection amount of the nitrogen injection device is low, the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection device are improved at the moment, the daily gas production amount of each gas production well is unchanged, and 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 improved 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, the nitrogen content is high, and the gas production of the third gas production well and the fourth gas production well is low, the nitrogen content is also low, then the displacement kick 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 of the first gas production well and the second gas production well should be reduced so that the injected nitrogen is displaced toward the third gas production well and the fourth gas production well to increase the gas production of the third gas production well and the fourth gas production well. At the same time, the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection device remain unchanged.
105. And controlling 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 at least one gas production well is used for producing coal bed gas based on the injected nitrogen and the adjusted daily gas production.
In the embodiment of the application, the nitrogen injection amount and the nitrogen injection pressure of the adjusted nitrogen injection equipment and the gas production amount of the adjusted gas production well are more in accordance with the production requirements, and the gas production amount of each gas production well can be ensured, so that the nitrogen injection equipment is controlled to inject nitrogen into the nitrogen injection well according to the adjusted nitrogen injection amount and the adjusted nitrogen injection pressure so as to displace the coal bed gas to at least one gas production well, and the at least one gas production well produces the coal bed gas based on the injected nitrogen and the adjusted gas production amount.
The first point to be described is that the embodiment of the present application is only described by taking the exploitation of coalbed methane through a gas production well as an example. In another embodiment, the coal bed gas produced by the injection 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 nitrogen content 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, any one of the following manners may be used to separate the mined coalbed methane from the nitrogen:
(1) And the separation equipment separates the coal bed gas mined by the injection well group from nitrogen in a gravity subsidence mode.
(2) And the separation equipment separates the coal bed gas mined by the injection well group from nitrogen in a low-temperature deacidification mode.
(3) And the separation equipment separates the coal bed gas mined by the injection well group from nitrogen in a molecular sieve mode.
The second point to be described is that, because the embodiment of the present application generates cost in the process of injecting nitrogen into the gas production well, it is necessary to acquire the cost of injecting nitrogen, and then acquire the value of the coalbed methane obtained by injecting nitrogen, if the value of the coalbed methane acquired is greater than the cost of injecting nitrogen, continuing to mine coalbed methane in the above manner, and if the value of the coalbed methane acquired is not greater than the cost of injecting nitrogen, stopping to mine coalbed methane 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 production well, which comprises the steps of determining nitrogen injection equipment meeting the conditions according to the desorption pressure and daily gas production amount of the coal bed gas of each gas production well in a gas production well group, injecting nitrogen into the nitrogen injection well by adopting the nitrogen injection equipment to displace the coal bed gas in the direction of at least one communicated gas production well through the nitrogen injection well, and adjusting the nitrogen injection amount and the nitrogen injection pressure of the nitrogen injection equipment and the daily gas production amount of the gas production well according to the daily gas production amount of the gas production well so as to ensure that the injected nitrogen can drive the coal bed gas in the coal bed to enter the gas production well, improve the exploitation rate of the coal bed gas and improve the recovery ratio.
In addition, the embodiment of the application separates the mined coalbed methane from the nitrogen through the separation equipment, so that the purity of the coalbed methane obtained by mining can be improved, and the coalbed methane meets the requirements of the quality standard of commodity gas.
In the following, the present application will be described with reference to three gas injection well groups. 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 one injection and production well group and are named as injection and production well group 1; the injection and production well group 2 consists of 1-2 nitrogen injection wells and 2-5 gas production wells, 2-6 gas production wells, 2-7 gas production wells, 2-8 gas production wells, 2-9 gas production wells and 2-10 gas production wells; the injection and production well group 3 consists of 1-3 nitrogen injection wells and 2-4, 2-5, 2-10, 2-11, 2-12 and 2-13 gas production wells.
The method provided by the embodiment of the application is implemented by adopting the following flow:
1. Selection area: the high-yield well in the high-permeability area is selected to be positioned at the Fan Zhuang block of the quick yield-reducing water-clearing basin, no faults and coal mines exist nearby, the gas content in the high-permeability area is 21 cubic meters per ton, and the permeability is 0.2 millidarcy.
2. Selecting a coal bed: and selecting coal beds which are uniformly distributed and have a thickness of about 5 meters, and all the wells are communicated with each other.
3. Selecting a nitrogen injection well and a gas production well: and (2) selecting 16 wells belonging to the coal seam 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 are gas production wells of two injection and production well groups.
4. Burst pressure: the burst pressure is 18 MPa according to the injection pressure drop test data of the adjacent evaluation wells; the fracturing construction curve of the 16 wells shows that the fracturing pressure is 16-21 megapascals, and the area fracturing pressure of the coal bed is determined to be 17 megapascals through analysis.
5. Desorption pressure: the desorption pressure values of all the three injection and production well groups in the zone are close, and the average value of the arithmetic of each gas production well is 2.6 megapascals as the desorption pressure of the coal bed zone for the convenience of equipment selection and daily management.
6. Nitrogen injection pressure: the coal seam displacement pressure was set at 1.7 mpa at one third to two thirds of the desorption pressure. The pressure of nitrogen injected into the wellhead was set at 1.5 times the desorption pressure of 2.6 mpa and 3.9 mpa. The nitrogen injection pressure was 17 mpa below the fracture pressure of the coal seam.
7. And (3) equipment type selection: the nitrogen injection equipment consists of nitrogen production equipment and nitrogen pressure boosting equipment. An aluminum dioxide molecular sieve air separation device is selected as nitrogen making equipment. A reciprocating compressor is selected as nitrogen boosting equipment. 13 gas production wells, wherein each well is provided with 2000 cubic meters of daily production, 26000 cubic meters of production is provided in the region, and the maximum discharge capacity of nitrogen production and pressure increasing equipment is 31000 cubic meters; the nitrogen injection pressure was 3.9 mpa by 1.1 factor and the nitrogen injection equipment discharge pressure was selected to be 4.3 mpa. A set of nitrogen injection equipment supplies nitrogen to three adjacent nitrogen injection wells simultaneously. After implementation, the actual nitrogen injection pressure is slowly raised from low to high and is gradually stabilized at 1.9-2.6 MPa.
8. Detecting nitrogen in a gas production well: and installing a nitrogen content detector in front of the flowmeter of each gas production well metering valve group, and collecting and transmitting the nitrogen content produced by each well, parameters such as gas production, pressure, temperature and the like to a database.
9. And (3) tracer injection: in order to judge the direction of the main force of nitrogen displacement, helium is injected into the 1-1, 1-2 and 1-3 nitrogen injection well heads at intervals of 5 months in sequence, and 100 cubic meters of helium is injected within 24 hours each time. The estimated time for helium to reach the gas production well was 100 days, and samples were taken from day 90 at the gas production well containing nitrogen to detect the helium of the gas production well.
10. Dynamic analysis: according to the corresponding relation and connectivity of the nitrogen injection well and the gas production well, the gas production well in the northeast and southwest directions has high gas yield and high nitrogen content, the tracer helium is detected earlier, the gas production well in the southeast and northwest directions has low yield, and the helium is not detected. Analysis suggests that northeast and southwest directions are the directions of maximum principal stress, along which the fracture crack tends to propagate, and thus nitrogen and helium are seen earlier, as principal force directions for displacement. And a dynamic adjustment scheme is designed, so that 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 sweeping area is enlarged.
11. And (3) regulating the injection and recovery balance, namely reducing the production allocation of the high-nitrogen 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, and inhibiting the nitrogen production to drive the gas production wells to the northwest and southeast directions, so that the high displacement speed is maintained, the local rapid sudden advance of the nitrogen is prevented, and the injection and recovery balance is achieved.
12. And analyzing the sweeping area, the volume multiple of injected pores and the recovery ratio.
13. And (3) denitrification treatment: when the nitrogen content of the coalbed methane is higher than the quality requirement of the output product gas, the coalbed methane enters the separation equipment to be deacidified at a low temperature to remove the nitrogen in the coalbed methane.
14. Economic benefit analysis: and (3) calculating comprehensive cost of nitrogen injection, gas production, denitrification, maintenance and the like, comparing and analyzing with the sales income of the coal bed gas, and judging economic benefits. If the economic benefit is available, continuing to inject nitrogen for displacement, and circulating the 8 th to the 14 th steps. If the economic benefit is not available, the nitrogen injection is finished, and the well is abandoned after the pressure energy of the coal bed is naturally released.
The foregoing description is only for the convenience of those skilled in the art to understand the technical solution of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (7)
1. The nitrogen injection and yield increase method is characterized in that at least one gas production well in the same coal bed is communicated with one nitrogen injection well 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 well group;
Determining the maximum nitrogen injection pressure of the nitrogen injection device according to the desorption pressure of the coalbed methane in the coalbed;
Controlling the nitrogen injection equipment, injecting nitrogen into the nitrogen injection well 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 is used for exploiting the coal bed gas based on the injected nitrogen;
According to the volume of nitrogen injected by the nitrogen injection device, the displacement and burst direction, the daily gas production amount and the nitrogen content of each gas production well, the nitrogen injection amount, the nitrogen injection pressure and the daily gas production amount of each gas production well of the nitrogen injection device are adjusted, and the displacement and burst direction is the direction of the nitrogen injection well pointing to any gas production well; the method for adjusting the nitrogen injection amount, the nitrogen injection pressure of the nitrogen injection device and the daily gas production amount of each gas production well according to the volume of nitrogen injected by the nitrogen injection device, the displacement kick-in direction and the daily gas production amount and the nitrogen content of each gas production well comprises the following steps: determining the displacement area of the nitrogen injection well for the injection and production well group according to the displacement and outburst direction, the injection void volume multiple, the daily gas production amount and the nitrogen content of each gas production well; 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 displacement area, wherein the injection void volume multiple is the ratio of the volume of injected nitrogen to the void volume of a coal bed;
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 mining the coal bed gas by at least one gas production well based on the injected nitrogen and the adjusted daily gas production.
2. The method according to claim 1, wherein the method further comprises:
the gas content of the coal layer is higher than the preset gas content, and the permeability of the coal layer is higher than the preset permeability.
3. The method according to claim 1, wherein the method further comprises:
The number of the gas production wells connected with the nitrogen injection wells 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 based on the desorption pressure of the coalbed methane in the coalbed, the method further comprises:
and determining the average value of the desorption pressure of the coalbed methane of the coalbed where each gas production well is located in the injection and production well group as the desorption pressure of the coalbed methane of the coalbed where the injection and production well group is located.
5. The method according to claim 1, wherein the method further comprises:
And detecting the nitrogen content, the gas yield, the temperature and the wellhead pressure of the corresponding gas production wells through a nitrogen content detector, a gas flowmeter, a temperature sensor and a pressure sensor which are arranged in each gas production well in the injection and production well group.
6. The method according to claim 1, wherein the method further comprises:
The nitrogen injection device injects a tracer into the nitrogen injection well;
And detecting the tracer in the at least one gas production well, and determining the direction of the nitrogen injection well to the gas production well with the detected tracer as the displacement and burst direction.
7. 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 mined by the injection well group from the nitrogen in a gravity sinking mode;
or the separation equipment separates the coal bed gas mined by the injection well group from the nitrogen in a low-temperature deacidification mode;
Or the separation equipment separates the coal bed gas mined by the injection well group from the nitrogen in a molecular sieve mode.
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