CN105138029B

CN105138029B - The compress control method of note nitrogen volume increase coal bed gas

Info

Publication number: CN105138029B
Application number: CN201510467978.3A
Authority: CN
Inventors: 陈信平
Original assignee: CHEN ZAIQIAN
Current assignee: Xi'an Huabang Petroleum Technology Development Co.,Ltd.
Priority date: 2015-08-03
Filing date: 2015-08-03
Publication date: 2016-06-29
Anticipated expiration: 2035-08-03
Also published as: CN105138029A

Abstract

A kind of pressure control program noting nitrogen volume increase coal bed gas and method.Note nitrogen well note nitrogen pressure, the note well head pressure of repercussion producing well of nitrogen speed, gas production, the change of nitrogen volumn concentration are fed back to note nitrogen well by the method by coalbed methane reservoir, adjust note nitrogen pressure, note nitrogen speed；To high permeability coalbed methane reservoir, building the pressure if desired, even conversion uses low pressure vibration pattern of pressure；To low-permeability coalbed methane reservoir, conversion if desired uses high-voltage oscillation pattern of pressure.Pressure control program and the method for the note nitrogen volume increase coal bed gas that the present invention provides are applicable to any coal seam, as long as there is sufficiently large air content in coal seam.The technical method of the present invention ensures that the nitrogen being injected into enters inside coal seam, whole coal seams between inswept note nitrogen well and producing well, make nitrogen enter micropore, coal seam, promote ADSORPTION STATE coal bed gas to desorb, and the free state coal bed gas after drive row desorption is to producing well, reaches to increase production the purpose of coal bed gas.

Description

The compress control method of note nitrogen volume increase coal bed gas

Technical field

The present invention relates to a kind of pressure control program noting nitrogen volume increase coal bed gas and method.Specifically, the present invention relates to a kind of from flatly or the many mouthfuls of wells connected with coal seam (hereinafter referred to as " noting nitrogen well ") are to coal seam nitrogen injection, promote hydrocarbon gas desorption, the mixed gas of the hydrocarbon gas of output and hydrocarbon gas and nitrogen is gathered from the multiple wells (hereinafter referred to as " producing well ") that connects with coal seam, when increasing solution volume increase coal bed gas, the pressure control program of use and method.

Background technology

Coal bed gas is the flammable hydrocarbon gas in coal seam, is also called gas, and its main component is methane.Coal bed gas is natural gas clean energy resource, is again to cause coal mine gas prominent and the reason of blast.It is reported, in countries such as China of rich coal resources, the U.S., Canada, Australia, Coal bed gas project more than or be equivalent to conventional gas stock number.Coal bed gas is the new clean energy resource that the mankind are important.

The coal bed gas of more than 95% is composed with ADSORPTION STATE and is existed in coal seam, is attached to surface, micropore in fluid film, it is impossible to move freely, separately composes in hole, hugger, crevice space with free state with the presence of the coal bed gas less than 5%.The mainstream technology of current exploitation coal bed gas is " drilling well-pressure break-draining-step-down-gas production " technology mode, relies on pressure break to increase coal seam permeability, relies on draining to reduce coal seam pressure and promotes coal bed gas desorption.But, the original permeability in most of coal seams is less than 1 millidarcy, and mechanical strength is little, and pressure break increases the DeGrain of permeability.If additionally, coal seam mechanical strength is little, due to the plastic behavior in coal seam, pressure break increases the effect of permeability can not be lasting；If Coal Pore Structure is affected by tectonic movement after the coalforming period and destroys, coal dust is serious, then, pressure break increases the effect of permeability can not be lasting.Although Coal bed gas project is huge, within 2013, world's Coal bed gas project is more than 260 tcms, much larger than world's conventional gas proved reserves 187 tcm, but world's methane output is very little, within 2013, world's coal bed gas total output is less than 700 billion cubic meters, only the 2.1% of world's conventional gas yield 3.38 tcm.Coal bed gas reserves are the most big and yield is the lowest, it is because currently used " drilling well-pressure break-draining-step-down-gas production " technology mode and can only develop the high-quality coalbed methane reservoir that minority permeability is high, mechanical strength is moderate, be not suitable for most coalbed methane reservoir.Accordingly, it would be desirable to develop new cbm development technology.

Puri and Stein proposes a kind of method increasing production coal bed gas, the method injects inert gas from note nitrogen well flatly to coal seam, such as, nitrogen, from flatly or many mouthfuls of producing wells obtain coal bed gas, it is possible to increase and methane output (see Rajen Puri and Michael H.Stein, 1988, Method of coalbed methane production, U.S. Patent number 4883122).This patented method requires " note nitrogen pressure keeps invariable (wherein the injection pressure is maintained substantially constant.) fully ", " note nitrogen pressure less than coalbed methane reservoir fracture pressure but is greater than the initial pressure (wherein the inert gas is injected at a pressure less than reservoir parting pressure but greater than initial reservoir pressure.) of coalbed methane reservoir ".

Although the gas injected to coal seam in theory can be any inert gas or with coal seam, the gas of chemical reaction not occur, but the gas injected to coal seam in practice may often be such that high-purity nitrogen and the mixed gas with nitrogen as main component, such as, chimney gas, blast furnace gas etc..This is primarily due to: (1) obtains the with low cost of high-purity nitrogen, and obtains other inert gases or with coal seam, gas relatively expensive of chemical reaction do not occur.(2) it is nitrogen and CO due to the main component of chimney gas, blast furnace gas₂, inject chimney gas, blast furnace gas to coal seam, while volume increase coal bed gas, have again carbon to bury, offset the dual benefits of CO2 emissions.But, coal seam is to CO₂High adsorption capacity, coal seam adsorb a large amount of CO₂Very big to the harm mined afterwards, therefore, note chimney gas, blast furnace gas may not apply to can working seam, and should apply to the unworkable coal seam that buried depth is big.

The patented method of Puri and Stein requires " gas injection pressure keeps invariable fully ", and " inert gas by with less than coalbed methane reservoir fracture pressure but be greater than the pressure of the initial pressure of coalbed methane reservoir and inject (coal seam) ".The patented method of Puri and Stein is not used by world's coal bed gas industry, one of reason is, it practice, this patented method is only applicable to, to the requirement of note nitrogen pressure, the high-quality coalbed methane reservoir that permeability is high, it is incorrect to most coalbed methane reservoirs, it is impossible to enforcement.

Pressure control program and the method for the note nitrogen volume increase coal bed gas that the present invention provides are applicable to any coal seam, the nitrogen being injected into is made to enter inside coal seam, whole coal seams between inswept note nitrogen well and producing well, nitrogen is made to enter micropore, coal seam, ADSORPTION STATE coal bed gas is promoted to desorb, and the free state coal bed gas after drive row desorption is to producing well, reaches to increase production the purpose of coal bed gas.

Summary of the invention

The present invention relates to a kind of pressure control program noting nitrogen volume increase coal bed gas and method.Specifically, the present invention relates to a kind of from flatly or the many mouthfuls of note nitrogen wells connected with coal seam are to coal seam nitrogen injection, promote hydrocarbon gas desorption, the mixed gas of the hydrocarbon gas of outputs and hydrocarbon gas and nitrogen is gathered from the many mouthfuls of producing wells that connect with coal seam, when increasing solution volume increase coal bed gas, the pressure control program of use and method.

The present invention is to use techniques below means to realize:

The present invention relates to a kind of pressure control program noting nitrogen volume increase coal bed gas and method.Specifically, the present invention relates to a kind of from flatly or the many mouthfuls of note nitrogen wells connected with coal seam are to coal seam nitrogen injection, promote hydrocarbon gas desorption, the mixed gas of the hydrocarbon gas of outputs and hydrocarbon gas and nitrogen is gathered from the many mouthfuls of producing wells that connect with coal seam, when increasing solution volume increase coal bed gas, the pressure control program used and method, enter inside coal seam with the nitrogen reaching to make to be injected into, whole coal seams between inswept note nitrogen well and producing well, nitrogen is made to enter micropore, coal seam, ADSORPTION STATE coal bed gas is promoted to desorb, and the free state coal bed gas after drive row desorption is to producing well, reach to increase production the purpose of coal bed gas.

Concrete pressure controlling step, flow process and method are as follows:

A (), in note nitrogen starting stage, transition stage, the stabilization sub stage, as required, uses different note nitrogen pressure；

B (), according to coalbed methane reservoir permeability, uses different note nitrogen pressure；

(c) monitoring producing well well head pressure, nitrogen percentage composition；

D (), to high permeability coalbed methane reservoir, in starting stage and transition stage, builds the pressure if desired, make note nitrogen pressure more than initial reservoir pressure and more than coal seam hydrostatic pressure；

E (), to high permeability coalbed methane reservoir, when there is nitrogen percentage composition exception well, on the premise of keeping note nitrogen speed, selectively reduces abnormal well array tolerance, or reduces note nitrogen pressure, or reduce abnormal well array tolerance simultaneously and reduce note nitrogen pressure；

F () is to high permeability coalbed methane reservoir, when nitrogen percentage composition exception well occurs, reducing note nitrogen pressure to less than initial reservoir pressure and less than after hydrostatic pressure, if the continuation of nitrogen percentage composition exception well quantity increases or nitrogen percentage composition speed over time does not reduces or continue to become big singularly, conversion use low pressure vibration pattern of pressure；

G (), to low-permeability coalbed methane reservoir, on the premise of keeping predetermined note nitrogen speed and note nitrogen pressure much smaller than coalbed methane reservoir top board and floor rocks fracture pressure, uses the least note nitrogen pressure；

H () is to low-permeability coalbed methane reservoir, in starting stage and transition stage, note nitrogen pressure more than coal seam fracture pressure and much smaller than coalbed methane reservoir top board and floor rocks fracture pressure but note nitrogen speed still less than predetermined note nitrogen speed in the case of, conversion uses high-voltage oscillation pattern of pressure；

H (), to low-permeability coalbed methane reservoir, when there is nitrogen percentage composition exception well, is reduced note nitrogen pressure, or is selectively reduced nitrogen percentage composition exception well array tolerance, or reduce note nitrogen pressure simultaneously and reduce nitrogen percentage composition exception well array tolerance；

I () is to low-permeability coalbed methane reservoir, when nitrogen percentage composition exception well occurs, nitrogen speed is then noted less than predetermined note nitrogen speed to less than coal seam fracture pressure reducing note nitrogen pressure, rising notes nitrogen pressure to increasing much smaller than roof and floor rocks fracture pressure then nitrogen percentage composition exception well quantity or in the case of the speed continuation change greatly singularly over time of nitrogen percentage composition, changing and use high-voltage oscillation pattern of pressure；

J () increases solution at note nitrogen and increases production in whole production period, Logic judgment flow process according to Fig. 3, note nitrogen pressure according to note nitrogen well, note nitrogen speed, the well head pressure of producing well, gas production, the change of nitrogen volumn concentration, judge, note nitrogen pressure, lines of producing wells tolerance according to judging to adjust.

The present invention compared with prior art, has following obvious beneficial effect and an advantage:

The pressure control program and the method that use the note nitrogen volume increase coal bed gas of the inventive method offer are applicable to any coalbed methane reservoir, as long as there is sufficiently large air content in coal seam.

World's coal bed gas reserves are huge, and yield is the lowest, is because currently used cbm development technology and can develop top quality coalbed methane reservoir, are not suitable for most coalbed methane reservoir.The technology that the present invention provides can develop most of coalbed methane reservoir, makes flood tide coal bed gas resource promote the well-being of mankind.

Accompanying drawing explanation

Fig. 1 (a) is the photo of high permeability coalbed methane reservoir coal sample, and figure (b) and (c) are the photos of low-permeability coal seam same coal sample different angles.The photo of Fig. 1 compares high and low permeability coalbed methane reservoir hugger, the greatest differences of cranny development degree, and this is the reason of coalbed methane reservoir permeability difference, also determines that one of foundation of note nitrogen pressure control program, selection pressure control method.

Fig. 2 (a) and Fig. 2 (b) is liquid, gas seepage velocity sectional schematic diagram in the duct connect blowhole respectively.This figure proves, owing to slipping slippage effect, at tube wall, gas molecule participates in flowing, is equivalent to increase the duct flowing space, therefore, gas permeability K in coal seam_aMore than absolute permeability K in coal seam, of course much larger than liquid permeability K in coal seam_L。

Fig. 3 is note nitrogen Stress control flow chart.

Detailed description of the invention

Below in conjunction with detailed description of the invention, the present invention will be further described.

" nitrogen " of the present invention is high-purity nitrogen and the gas with nitrogen as main component.High-purity nitrogen is the nitrogen volumn concentration gas more than 95%.Gas with nitrogen as main component is the nitrogen volumn concentration mixed gas more than 50%, such as, chimney gas, blast furnace gas.

Note nitrogen volume increase coal bed gas it is crucial that how to make the nitrogen that is injected into enter inside coal seam, whole coal seams between inswept note nitrogen well and producing well, make nitrogen enter micropore, coal seam, promote ADSORPTION STATE coal bed gas to desorb, and the free state coal bed gas after drive row desorption is to producing well.This " promotees to solve drive row " effect and promotes coal bed gas desorption and migrate to producing well from note nitrogen well, arrives producing well well head collected.Note nitrogen pressure must be sufficiently large, at least have to be larger than initial reservoir pressure, nitrogen can be injected coal seam, at least have to be larger than coal seam hydrostatic pressure, the water drive in coal seam could be discharged in country rock or drive row is to ground.

The pressure on fluid that reservoir pressure refers to act in reservoir pore space, also referred to as formation pore pressure.Reservoir pressure is exactly strata pressure, merely because certain stratum is reservoir, and the reservoir pressure so this strata pressure is otherwise known as.The initial reservoir pressure of coalbed methane reservoir is the fluid pressure experienced when ground in-situ before CBM exploration and development in the hole of coal seam.

The initial reservoir pressure P of coalbed methane reservoir_JustWith the relation of coal seam depth H it is:

P_Just=P_Gradient*H (1)

Wherein P_JustIt is the initial reservoir pressure of coalbed methane reservoir, unit: MPa, i.e. MPa；

H is the coal seam degree of depth, unit: m, i.e. rice；

P_GradientFormation pressure gradient, i.e. the change of per unit degree of depth strata pressure, unit: MPa/m.P_GradientIt is usually the parameter become with the degree of depth, but can be approximated to be constant.If P_GradientBe parameter, then formula (1) should be integral expression.

Initial reservoir pressure is formed by many factors, but mainly has 2 sources: the rock pressure that (1) overburden weight produces, i.e. geostatic pressure.(2) water column pressure that in reservoir pore space, formation water weight produces, i.e. hydrostatic pressure.Hydrostatic pressure can be expressed as:

P_Water=H ρ_WaterG/1000 (2)

Wherein P_WaterIt is hydrostatic pressure, unit: MPa；

H is the coal seam degree of depth, unit: m, i.e. rice；

G is acceleration of gravity, unit: 9.8m/s²；

ρ_WaterIt is the density of water, unit: g/cm³.

By initial reservoir pressure P_JustWith hydrostatic pressure P_WaterRatio be defined as reservoir pressure factor alpha_P:

If < 0.9, then reservoir is referred to as low pressure reservoir to 0.75 < reservoir pressure coefficient；If < 1.1, then reservoir is referred to as normal pressure reservoir to 0.9 < reservoir pressure coefficient；If < 1.4, then reservoir is referred to as high-pressure reservoir to 1.1 < reservoir pressure coefficients；If reservoir pressure coefficient > 1.4, then reservoir is referred to as overpressured reservoir, is abnormal pressure.Conventional gas gas field there may be high-pressure reservoir or overpressured reservoir.Coalbed methane reservoir is typically low pressure reservoir or normal pressure reservoir, high-pressure reservoir less, does not has overpressured reservoir.

When note nitrogen increases solution volume increase coal bed gas, the water in the nitrogen of injection first drive row coal seam hugger, crack, from the close-by examples to those far off gradually occupy from note nitrogen well to the space being originally occupied by the water producing well dust trajectory.Secondly, at this while migration, nitrogen permeates to matrix of coal block under high pressure effect, enters micropore, and displacement surface, micropore is the coal bed gas of ADSORPTION STATE fluid film shape, makes free state coal bed gas；Finally, free state coal bed gas is under high drive, and diffusion arrives hugger, crack；In hugger, the desorption of fracture surface generation secondary, enter in hugger, networking, crack, arrived producing well along hugger, crack by drive row.

The patented method of Puri and Stein requires " note nitrogen pressure keeps invariable fully ", " note nitrogen pressure less than coalbed methane reservoir fracture pressure but is greater than the initial pressure of coalbed methane reservoir ".These are about the requirement of note nitrogen pressure, and for hugger, cranny development thus the high high-quality coalbed methane reservoir of permeability, such as, original permeability is more than the coal seam of several millidarcies, although can not be said to be mistake, but is not enough to instruct note nitrogen Stress control；For hugger, crack agensis or suffer tectonic movement transformation to cause the low-permeability coalbed methane reservoir of hugger, closing of fracture after the coalforming period, it is incorrect.Such as, Fig. 1 (a) illustrates hugger, the photo in the preferable coal seam of cranny development, and hugger, crack constitute the network of water and nitrogen migration.For such coalbed methane reservoir, as long as note nitrogen pressure is substantially greater than coal seam initial reservoir pressure, the nitrogen injected just can be along hugger, fracture seepage migration, water in drive row hugger, crack, be full of hugger, the nitrogen in crack is migrated to matrix of coal block diffusion inside under high pressure effect, enter micropore, coal seam, the ADSORPTION STATE coal bed gas of displacement drive row micropore surface liquid film-form.Fig. 1 (b) and (c) are the photos of low-permeability coal seam same coal sample different angles.This coal sample picks up from underground coal mine Driving Face in Coal Tunnel, and this coal seam permeability is the 0.1～0.001 millidarcy order of magnitude.This is the scope of the original permeability in most coal seams in the world.To coal seam shown in Fig. 1 (b) and (c), can't see hugger, the crack opened, the original hugger in possible coal seam, crack agensis, it is also possible to the tectonic movement after the coalforming period causes hugger, closing of fracture.The hugger in this coal seam shown with Fig. 1 (a), crack form a sharp contrast.In Fig. 1 (b) and (c), it can be seen that coal seam exists layer reason.It is, in general, that the diameter of the intracrystalline pore between layer reason, primary intergranular pore is more than layer reason internal intracrystalline pore, the diameter of primary intergranular pore.Between these layers of reason and the internal micropore of layer reason, the pore throat of the connection micropore being made up of intracrystalline pore, primary intergranular pore, be the path in nitrogen entrance coal seam.Those hugger being closed under crustal stress effect, cracks, it is also possible to do not have of completely closed, be simply invisible to the naked eye.Not having of completely closed hugger, crack can also be the path that nitrogen enters micropore, coal seam.But, according to the requirement of the patented method of Puri and Stein, keeping " note nitrogen pressure is less than coalbed methane reservoir fracture pressure ", nitrogen will only be through micropore, intracrystalline pore, primary intergranular pore, do not has the inswept coal seams of seepage flow such as of completely closed hugger, crack.Nitrogen by intracrystalline pore, primary intergranular pore pore throat, do not have of completely closed hugger, fracture seepage to enter micropore, coal seam.Nitrogen is big along such path migration resistance, and buckling factor is big, path length.Obviously, in this case, in coal seam, nitrogen flow is little, the time in the inswept coal seam of nitrogen migration injected may be the veryest long, to such an extent as to the patented method of Puri and Stein " notes the selection of note nitrogen pressure nitrogen pressure and keep invariable fully " and " note nitrogen pressure less than coalbed methane reservoir fracture pressure but is greater than the initial pressure of coalbed methane reservoir " is infeasible in practice.

Fluid flow Q in coal seam is stated by following formula:

Q = K \frac{A Δ p}{μ L} \times 10 - - - (3)

In formula, Q is the fluid flow by coal seam, unit: cm³/s；

K is the permeability in coal seam, unit: darcy (D), and K is with the absolute permeability in coal seam as radix, because in coal seam, fluid properties is different and change；

A is nitrogen dilatation wave frontal area in coal seam, unit: cm²；

L is length, i.e. same coal seam extended length between note nitrogen well and producing well, unit: cm；

△ P is to be added in the pressure reduction at two ends, coal seam, unit: MPa (MPa) between note nitrogen well and producing well；

μ is the viscosity of fluid, unit: mPa s (pascal second in the least).

In same coal seam, due to the factors such as capillary effect, the liquid (i.e. underground water) permeability K in coal seam_LAbsolute permeability K less than coal seam；Due to slip phenomenon, gas permeability K in coal seam_aMore than absolute permeability K in coal seam, the even larger than underground water (i.e. liquid) permeability K in coal seam_L.Liquid seepage flow in coal seam is affected by capillary, owing to there is viscosity resistance between fluid molecule, there is also viscosity resistance F between viscosity resistance, and fluid molecule and pore wall between fluid molecule and pore wall_Liquid _- _{Tube wall}More than viscosity resistance F between fluid molecule_Liquid _- _Liquid.On capillary cross sectional, at tube wall, viscosity resistance is maximum, and center is minimum, and therefore, flow rate of liquid is maximum at capillary center, and tube wall is minimum, and on tube wall, fluid molecule is stuck, and flow velocity is equal to zero, and flow velocity section is conic section, as shown in Fig. 2 (a).Such flowing is referred to as " newtonian viscous flowing ".Due to the suction-operated between underground water and coal, at tube wall, hydrone formation liquid film does not flows, and reduces the duct flowing space, therefore, water permeability K in coal seam_LAbsolute permeability K less than coal seam.By contrast, gas seepage flow in coal seam, owing to molecular radius is little, between molecule, spacing is big, and viscosity resistance disappears.Molecular collision, produces momentum-exchange, and at tube wall, molecule is not bound on tube wall, still in motion state.Therefore, on the pore channel section of coal seam, between gas molecule, current difference disappears, gas flows in pore channel and slide effect occurs, deviation newtonian viscous flowing, as shown in Fig. 2 (b), here it is so-called slip phenomenon, i.e. gas are in coal seam during seepage flow,, there is the flow phenomenon that gas molecule speed at tube wall is not equal to zero in its flow velocity distribution deviation viscous fluid flow on pore section.Due to slippage effect, at tube wall, gas molecule participates in flowing, is equivalent to increase the duct flowing space, therefore, gas permeability K in coal seam_aMore than absolute permeability K in coal seam, of course much larger than liquid permeability K in coal seam_L。

It is that under conditions of an atmospheric pressure, temperature are 20 DEG C, the viscosity of water is 1.01 × 10 at pressure^-3Pa s, the viscosity of nitrogen is 17.58 × 10^-6Pa s, differs 57 times.The viscosity of fluid is mainly affected by temperature and pressure.When temperature raises, the viscosity of gas raises and the viscosity of liquid declines.When pressure increases, the viscosity of liquids and gases all increases, but the amount increased is the least.Note nitrogen increases pressure and temperature when solving volume increase coal bed gas in coal seam, and relative to the standard conditions that an atmospheric pressure, temperature are 20 DEG C, water and the viscosity B coefficent of nitrogen that temperature and pressure change causes are the most little.Therefore, when note nitrogen increases solution volume increase coal bed gas, for the underground water in coal seam and the nitrogen injected in coal seam, can think that their viscosity two orders of magnitude of difference differ tens times in other words roughly.

Note nitrogen is increased solution volume increase coal bed gas production process and is divided into three phases by the present invention: (1) note nitrogen starting stage, be also called " starting stage "；(2) note nitrogen transition stage, is also called " transition stage "；(3) the steady production stage, it is also called " stabilization sub stage ".Increasing for note nitrogen and solve volume increase coal bed gas technology, from starting to note nitrogen to stable state, in coal seam, the character of fluid has a change procedure from liquid to gas.In the note nitrogen starting stage, the fluid in coal seam is substantially a phase liquid water.Along with nitrogen injects coal seam, entering transition stage, the fluid in coal seam becomes the mixture of two-phase fluid water and gas.Narrowly, the fluid in this stage coal seam is heterogeneous fluid, at least the three-phase fluid of water, nitrogen, methane.But, owing to the difference between the fluid behaviour parameters such as nitrogen and the permeability of coal bed gas (its main component is methane), viscosity is the least, therefore, it can simplification and process, do not differentiate between nitrogen and methane, it is believed that the fluid in coal seam is gas-liquid two-phase fluid.Note nitrogen continues, and the water in coal bed gas is gradually by outside high pressure nitrogen drive row to wellblock and top, in floor rocks, or be discharged to ground by the drainpipe of producing well.When the fluid in coal seam becomes one phase flow body gas, when i.e. only having the mixed gas of gas coal bed gas and nitrogen in coal seam, note nitrogen increasing solution is increased production coal bed gas production and is reached so-called " stabilization sub stage ".

In the note nitrogen starting stage, only a small amount of methane and nitrogen in coal seam, approximate 100% water saturation, therefore, permeability K in formula (3) and viscosity, mu are permeability and the viscosity of water respectively.Along with nitrogen injects coal seam, water saturation degree reduces, the gas mixture of methane (nitrogen or the nitrogen with) saturation degree increases, and the fluid in coal seam becomes two-phase fluid, and permeability K in formula (3) and viscosity, mu should be equivalent permeability and the equivalent viscosities of this two-phase fluid.

This equivalent permeability is permeability and saturation degree, the permeability of gas and the function of saturation degree thereof of water, and it continues with nitrogen of showwing loving care for and increases.In starting stage and transition stage early stage, because gas saturation is low, the main component of this equivalent permeability is the permeability of water, and gas permeability is less on the impact of this equivalent permeability.With showwing loving care for, nitrogen continues, and gas saturation increases, and the impact of this equivalent permeability is increased by gas permeability, and water saturation reduces, and the impact of this equivalent permeability is also reduced by water penetration rate.Owing to gas permeability is more than water penetration rate, this equivalent permeability will be gradually increased in transition stage.In transition stage late period, because water saturation is low, the main component of this equivalent permeability is gas permeability, and water penetration rate is less on the impact of this equivalent permeability.After note nitrogen increasing solution volume increase reaches stable state, permeability K in formula (3) is the permeability of gas.

Similarly, the equivalent viscosity of inverted gas and water body is viscosity and saturation degree, the viscosity of gas and the function of saturation degree thereof of water, and it continues with nitrogen of showwing loving care for and reduces.In starting stage and transition stage early stage, because gas saturation is low, the main component of this equivalent viscosity is the viscosity of water, and gas viscosity is less on the impact of this equivalent viscosity.With showwing loving care for, nitrogen continues, and gas saturation increases, and the impact of this equivalent viscosity is increased by gas viscosity；Water saturation reduces, and the impact of this equivalent viscosity is also reduced by water viscosity.Owing to water viscosity is much larger than gas viscosity, this equivalent viscosity will be gradually reduced in transition stage.In transition stage late period, because water saturation is low, the main component of this equivalent viscosity is gas viscosity, and water viscosity is less on the impact of this equivalent viscosity.After note nitrogen increasing solution volume increase reaches stable state, viscosity K in formula (3) is the viscosity of gas.

Therefore, from the note nitrogen starting stage, to transition stage, again to the stabilization sub stage, along with in coal seam, fluid properties is changed to air water two-phase mixture from a phase liquid, then it is changed to a phase gas, the equivalent permeability of fluid experienced by a change procedure from small to large, being i.e. the permeability of gas from the permeability variation of water, and the equivalent viscosity of fluid experienced by a change procedure from big to small, i.e. from the viscosity B coefficent of water be the viscosity of gas.

The present invention is by the nitrogen volume under note nitrogen well injects the status of criterion in coal seam flatly in the unit interval, referred to as " note nitrogen speed ".When having many mouthfuls of note nitrogen wells, each note nitrogen well can have different predetermined note nitrogen speed.Note nitrogen speed and the flow Q positive correlation in formula (3), but it is not equal to.When using nitrogen making machine as nitrogen source, typically will " make a reservation for note nitrogen speed " speed being set equal to source nitrogen the supply of nitrogen.Such as, if the nitrogen ability processed of nitrogen making machine is 2000m³/ h, then, predetermined note nitrogen speed is typically also 2000m³/ h, on the one hand avoids wasting nitrogen, on the other hand keeps the gas production that producing well is stable.When using low-temperature liquefaction nitrogen or use blast furnace gas, chimney gas, generally having many mouthfuls of note nitrogen wells, each note nitrogen well can have different predetermined note nitrogen speed.In production practices, when noting nitrogen speed less than predetermined note nitrogen speed, it is necessary to ascertain the reason, take corresponding measure.

For high permeability coal seam, owing to permeability K is big, as long as note nitrogen pressure is more than the initial pressure of coalbed methane reservoir and more than hydrostatic pressure, it becomes possible to nitrogen is injected coal seam according to predetermined note nitrogen speed.After note nitrogen starts, the network path that nitrogen will be constituted along hugger, crack, migrate to producing well from note nitrogen well, and in network path, form inverted gas and water body, surround matrix of coal block.Note nitrogen continues, producing well needs to build the pressure, gradually step up the pressure of fluid in network path, until note nitrogen pressure is more than the initial reservoir pressure in coal seam and more than hydrostatic pressure, and reach following four purposes: (1) orders about nitrogen microfissure seepage flow along matrix of coal block, the coal seam that nitrogen is the most inswept between note nitrogen well and producing well.(2) order about nitrogen and enter the micropore in matrix of coal block by microcrack, intergranular pore throat, intergranular pore throat diffusion And Movement, promote the ADSORPTION STATE methane on surface, micropore to desorb.Meanwhile, sub-fraction nitrogen is converted to ADSORPTION STATE nitrogen, ties up the position on surface, micropore, " stripping " ADSORPTION STATE methane, promotes methane desorption.(3) by the water in coal seam intercrystalline water, micropore, the network path that drive row to hugger, crack are constituted, the water drive in this network path is discharged to producing well pit shaft.(4) by automatic for the water in producing well pit shaft pressure to ground, the fluid in coal seam is made to complete to become the change procedure of a phase gas from air water two-phase mixture.After note nitrogen pressure is more than coal seam initial reservoir pressure and is more than the hydrostatic pressure long enough time, the fluid in coal seam becomes a phase (gas phase) fluid, and note nitrogen increasing solves increases production entrance stable state.To high permeability coal seam, both there is no need also to should not be larger that coal seam fracture pressure, reason is as follows: (1) is as long as coal seam permeability is enough the most significantly, even if in note nitrogen starting stage and transition stage early stage, as long as keeping note nitrogen pressure more than coal seam initial reservoir pressure and more than hydrostatic pressure, just it is enough to ensure that, by predetermined note nitrogen speed, nitrogen is injected coal seam, therefore, it is not necessary to use bigger note nitrogen pressure.If coal seam permeability is the biggest, it is possible to when note nitrogen pressure is less than coal seam initial reservoir pressure, it is also possible to by predetermined note nitrogen speed, nitrogen is injected coal seam.In this case it is necessary to control producing well gas production, even completely close producing well aerogenesis valve, promote coalbed methane reservoir pressure to raise；This is referred to as " producing well builds the pressure ".By building the pressure, by note nitrogen boost in pressure to more than coal seam initial reservoir pressure and more than hydrostatic pressure, reach to squeeze in country rock by the water in coal seam, or squeeze after producing well pit shaft, under gas pressure effect, drain into ground through lines of producing wells water pipe.(2) note nitrogen increases success or failure and the effect size solving volume increase, be decided by inject coal seam nitrogen can from note nitrogen well in the road that producing well is migrated, can coal seam between inswept note nitrogen well as much as possible and producing well, enter in the micropore of matrix of coal block, " replace ", " stripping " ADSORPTION STATE coal bed gas, and by its drive row to producing well pit shaft.To high permeability coalbed methane reservoir, the note pressure controlled emphasis of nitrogen be not to ensure that nitrogen migration to producing well because accomplishing that this point is easy to；And it is to ensure that nitrogen should be migrated to producing well from note nitrogen well, directly can not scurry into producing well from note nitrogen well again.Therefore, note nitrogen pressure should not be larger that coal seam fracture pressure, and otherwise, powerful fracture pressure is likely to result in nitrogen and directly scurries into the path of producing well from note nitrogen well.(3) note nitrogen pressure is big, and the power that supercharger consumes is many, and note nitrogen increasing solves volume increase cost and raises.Therefore, it should on the premise of ensureing note nitrogen speed, use the most lower note nitrogen pressure.

For high permeability coalbed methane reservoir, the requirement of the patented method of Puri and Stein " inert gas by with less than coalbed methane reservoir fracture pressure but be greater than the pressure of the initial pressure of coalbed methane reservoir and inject (coal seam) ", although can not be said to be mistake, but it is not enough to instruct note nitrogen Stress control.First, from the initial pressure of coalbed methane reservoir to coalbed methane reservoir fracture pressure be a pressure limit the biggest.If coalbed methane reservoir is normal pressure reservoir, initial reservoir pressure is approximately equal to hydrostatic pressure.The degree of depth of most coalbed methane reservoirs of current exploitation is less than 1000m.Buried depth is that the hydrostatic pressure in the coal seam of 1000m is about 9.8MPa.Coal seam fracture pressure is generally between 25～35MPa.From the initial pressure of coalbed methane reservoir to coalbed methane reservoir fracture pressure, pressure range at more than 15MPa, even up to 25MPa.Selecting note nitrogen pressure is 10MPa, meets the requirement of the patented method of Puri and Stein.Selecting note nitrogen pressure is 24MPa, also complies with the requirement of the patented method of Puri and Stein.Obviously, 10MPa note nitrogen pressure is the biggest with the effect difference of 24MPa note nitrogen pressure.The patented method of Puri and Stein does not provide the foundation of selection.Secondly, to high permeability coalbed methane reservoir, even if note nitrogen pressure is less than fracture pressure, also having nitrogen directly to scurry into the danger of producing well from note nitrogen well, such danger has occurred and that or predicts that such danger will occur to need monitoring to determine.Furthermore, the fracture pressure in coal seam is unknown.The coal seam fracture pressure obtained during implementing fracturing engineering, an only estimate.Keep note nitrogen pressure less than this estimate, it is impossible to ensure that coal seam does not ruptures.This also illustrates to need detection there is coal seam risk of rupture or have occurred and that coal seam ruptures.The patented method of Puri and Stein does not provide the detection method that coal seam ruptures and corresponding method of disposal.3rd, if coalbed methane reservoir is low pressure reservoir, even if note nitrogen pressure is more than initial reservoir pressure, cannot guarantee that noting nitrogen pressure is more than hydrostatic pressure, obstruction note nitrogen increases solution and increases production the coal bed gas entrance stabilization sub stage.Therefore, the minimum requirements of note nitrogen pressure is not " more than initial reservoir pressure ", and should be " more than initial reservoir pressure and more than hydrostatic pressure ".4th, due in starting stage and transition stage early stage, permeability K in formula (3) and viscosity, mu are permeability and the viscosity of water respectively, permeability K value is little, viscosity, mu value is big, and in transition stage late period and stabilization sub stage, permeability K in formula (3) and viscosity, mu are permeability and the viscosity of gas respectively, permeability K value is big, viscosity, mu value is little, therefore, in order to keep predetermined note nitrogen speed, starting stage and transition stage note nitrogen pressure in early days, it should more than the note nitrogen pressure of transition stage late period and stabilization sub stage.The patented method of Puri and Stein does not embody the change that note nitrogen pressure should have in different phase.

For high permeability coalbed methane reservoir, owing to permeability is very big, or owing to note nitrogen pressure is big excessively, or due to the common effect of the two reason, nitrogen is likely directly scurried into producing well from note nitrogen well, is not adequately diffuse in matrix of coal block.This is that impact note nitrogen increases solution effect of increasing production principal element.Coal seam is the high reservoir oozed in local, is also the reservoir that permeability orientation is bigger, because coal seam permeability depends mainly on hugger, cranny development degree, and the development degree of hugger, crack is to change and directive.Some or certain several producing well well head pressures become big singularly, the nitrogen percentage composition of institute's aerogenesis body is singularly higher than other wells, or the time dependent speed of nitrogen percentage composition becomes greatly (hereinafter referred to as " nitrogen percentage composition exception well ") singularly, it is to judge that nitrogen directly scurries into the foundation of producing well from note nitrogen well.The present invention provides three processing methods to " the nitrogen percentage composition exception well " of high permeability coalbed methane reservoir: (1) reduces note nitrogen pressure；(2) " nitrogen percentage composition exception well " gas production, even temporary close " nitrogen percentage composition exception well " are reduced；(3) after implementing the first two method, if " nitrogen percentage composition exception well " quantity does not reduces, and be to continue with increasing, it is transformed into " low pressure vibration pattern of pressure ", i.e. note nitrogen pressure change in oscillation in time, the interval of pressure oscillation change is, minimum note nitrogen pressure is substantially smaller than initial pressure and the substantially smaller than hydrostatic pressure of coalbed methane reservoir, maximum note nitrogen pressure is more than the initial pressure of coalbed methane reservoir and more than hydrostatic pressure, and substantially smaller than coal seam fracture pressure, alternately use minimum note nitrogen pressure, maximum note nitrogen pressure, allow note nitrogen speed less than predetermined note nitrogen speed, but, keep producing well well head pressure more than the initial pressure more than coalbed methane reservoir and more than hydrostatic pressure.

For low-permeability coal seam, due to original hugger, crack agensis or after the coalforming period tectonic movement and crustal stress be closed part or all of original hugger, crack, the nitrogen injecting coal seam is difficult to or may not migrate to producing well along hugger, crack, but the path constituted by intracrystalline pore, intergranular pore and microcrack, diffuse into the micropore in coal seam, displacement, " stripping " ADSORPTION STATE methane.Intracrystalline pore, intergranular pore, the yardstick of microcrack are usually 1～100 micron number magnitudes, and water, methane, nitrogen molecule diameter are respectively 0.40 nanometer, 0.414 nanometer, 0.35 nanometer.Therefore, on the one hand, water, methane, nitrogen can be migrated to producing well along the path that pore throat radius is micron number magnitude from note nitrogen well；On the other hand, such migration path buckling factor is big, migration resistance is big.According to formula (3), in order to keep predetermined note nitrogen speed, only increase the pressure reduction △ P at two ends, coal seam between note nitrogen well and producing well, i.e. increase note nitrogen pressure.For the coal seam that the primary hugger shown in Fig. 1 (b) and (c) is of completely closed, note nitrogen pressure must be sufficiently large, can be in the path that the intracrystalline pore of micron number magnitude, intergranular pore, microcrack are constituted, the seepage flow migration of water or inverted gas and water body or gas could be formed, it is possible to obtain and keep predetermined note nitrogen speed.

For low-permeability coal seam, in the note nitrogen starting stage, permeability K in formula (3) and viscosity, mu are permeability and the viscosity of water respectively, and permeability K value is little, and viscosity, mu value is big.Even if note nitrogen pressure is more than the initial pressure of coalbed methane reservoir, it is possible to after the of short duration time, note nitrogen speed becomes less than predetermined note nitrogen speed.According to formula (3), in order to maintain note nitrogen speed, not only need to increase note nitrogen pressure, and be likely to require and note nitrogen pressure is increased above coal seam fracture pressure.Especially, coal seam (hereinafter referred to as " microdarcy coal seam ") for permeability as little as 0.01mD～the 0.001mD order of magnitude, such as, Fig. 1 (b) and the coal seam shown in (c), it is necessary note nitrogen pressure is increased above coal seam fracture pressure, as nitrogen foam pressure break, pressure break coal seam, crack, microfissure, microcrack is caused in coal seam, the passage migrated to producing well from note nitrogen well as nitrogen, enters the offer passage easily of micropore, coal seam for nitrogen.On the contrary, if as Puri and Stein patented method require as, limit note nitrogen pressure, be less than coal seam fracture pressure, nitrogen from note nitrogen well migration arrive producing well time will the veryest long, from but note nitrogen increase solve increase production coal bed gas become impossible.Note nitrogen pressure is increased, it is necessary to assure note nitrogen pressure is much smaller than roof and the fracture pressure of floor rocks, and otherwise, top board or floor rocks, by pressure break, form the passage in nitrogen effusion coal seam, and note nitrogen increases solution volume increase will failure it can however not unrestricted.Therefore, in the note nitrogen starting stage, note nitrogen pressure should be more than the initial pressure of coalbed methane reservoir and more than hydrostatic pressure, substantially simultaneously less than top board and the fracture pressure of floor rocks.Due to top, the common coal seam such as sandstone, shale, limestone, floor rocks fracture pressure much larger than the fracture pressure in coal seam, therefore, make note nitrogen pressure more than coal seam fracture pressure substantially smaller than top board and the fracture pressure of floor rocks, it is possible to easily to accomplish.

For low-permeability coal seam, in note nitrogen transition stage, the selection of some impact note nitrogen pressure below: (1) starting stage note nitrogen pressure is big, has produced substantial amounts of microcrack in coal seam.If starting stage note nitrogen pressure is relatively big more than the degree of coal seam fracture pressure, note nitrogen also causes microfissure, crack in coal seam.Therefore, coal seam is modified the most more or less, and absolute permeability increases.(2) in coal seam, gas saturation is gradually increased, and gas relative permeability is gradually increased, and the equivalent permeability in coal seam is gradually increased, and equivalent viscosity is gradually reduced.(3) if note nitrogen pressure is more than coal seam fracture pressure or once more than coal seam fracture pressure, high pressure nitrogen is likely to result in the gas passage that directly connects between note nitrogen well and producing well, and nitrogen has and ruptures the passage caused and directly scurry into producing well possibility from noting coal seam, nitrogen well.Therefore, in transition stage, control note nitrogen pressure by following principle: (1) note nitrogen pressure range is, more than the initial pressure of coalbed methane reservoir and more than hydrostatic pressure, and substantially smaller than top board and the fracture pressure of floor rocks.(2) on the premise of ensure that predetermined note nitrogen speed, the least note nitrogen pressure is used.(3) if having to make note nitrogen pressure more than coal seam fracture pressure for a long time, it is contemplated that conversion uses " high-voltage oscillation pattern of pressure ", even if note nitrogen pressure change in oscillation in time, the interval of pressure oscillation change is, minimum note nitrogen pressure is more than the initial pressure of coalbed methane reservoir and more than hydrostatic pressure, maximum note nitrogen pressure is less than roof and the fracture pressure of floor rocks, and guarantee will not pressure break roof and floor rocks, alternately use minimum note nitrogen pressure, maximum note nitrogen pressure.(4) when having to make note nitrogen pressure more than coal seam fracture pressure, the change of nitrogen percentage composition in monitoring producing well well head pressure, institute's aerogenesis body.If there is one or several " nitrogen percentage composition exception well ", do corresponding disposal.The present invention provides three processing methods to " the nitrogen percentage composition exception well " of low-permeability coalbed methane reservoir: (i) reduces note nitrogen pressure；(ii) " nitrogen percentage composition exception well " gas production, even temporary close " nitrogen percentage composition exception well " are reduced；(iii) after implementing the first two method, if " nitrogen percentage composition exception well " quantity does not reduces, and it is to continue with increasing, is transformed into " high-voltage oscillation pattern of pressure ".For low-permeability coal seam, in note nitrogen transition stage, 4 targets that the target that note nitrogen is to be reached notes nitrogen transition stage to be reached with aforementioned high permeability coal seam are identical, mainly the water drive in coal seam intercrystalline water, micropore is discharged to producing well pit shaft, by automatic for the water in producing well pit shaft pressure to ground, the fluid in coal seam is made to complete to become the change procedure of a phase gas from air water two-phase mixture.In this process, note nitrogen pressure is controlled most important by aforementioned four principles, should ensure, by predetermined note nitrogen speed, nitrogen is injected coal seam, diffusion and/or seepage flow enter micropore, coal seam, ensure that nitrogen the most directly scurries into producing well from note nitrogen well again, ensure not pressure break roof and floor rocks, it is to avoid the nitrogen injecting coal seam spills in country rock.In starting stage and transition stage, owing to note nitrogen pressure is big, especially, if note nitrogen pressure is more than coal seam fracture pressure, crack that high pressure nitrogen causes in coal seam, microcrack, permeability of coal bed gas will be increased significantly.

For low-permeability coal seam, in the note nitrogen stabilization sub stage, on the one hand, owing to the fluid in coal seam is a phase gas, permeability K in formula (3) and viscosity, mu are permeability and the viscosity of gas respectively.This gas is coal bed gas (main component is methane), nitrogen or the mixed gas of the two.The permeability of methane, nitrogen or its mixed gas, viscosity have difference, but difference is little, therefore are referred to as gas.It has been observed that gas permeability is more than the permeability of water, little two orders of magnitude of viscosity of gas viscosity far water.Therefore, if the note nitrogen speed of stabilization sub stage is identical with the note nitrogen speed of transition stage, then, the note nitrogen pressure required for the stabilization sub stage likely will be substantially less that the note nitrogen pressure of transition stage.On the other hand, coal seam is the rock that plastic deformation is big, and in the crack that transition stage high pressure nitrogen causes in coal seam, microcrack, after the stabilization sub stage, note nitrogen pressure reduced, crack, microcrack may gradually close, and cause coal seam permeability to lower.In order to keep predetermined note nitrogen speed, need to increase note nitrogen pressure, the most again or repeatedly make note nitrogen pressure more than coal seam fracture pressure.Therefore, for low-permeability coal seam, the note nitrogen pressure of stabilization sub stage is not changeless, but according to predetermined note nitrogen speed, nitrogen seepage flow and diffusion And Movement situation in coal seam, adjusts constantly.With nitrogen time lengthening of showwing loving care for, coal bed gas desorbs in a large number, and the desorption-blockage effect of coal bed gas will cause coal seam to be shunk, and produces new crack, microcrack in coal bed gas, and and crack, microcrack that high pressure injection nitrogen causes will not be closed again.

No matter for high permeability coalbed methane reservoir or for low-permeability coalbed methane reservoir, no matter in note nitrogen starting stage, transition stage or stabilization sub stage, all there is the nitrogen injecting coal seam and directly scurry into the possibility of producing well from note nitrogen well, although the reason producing this possibility is not quite similar.Therefore, during note nitrogen is whole, it is required for monitoring whether to there occurs that nitrogen directly scurries into producing well from note nitrogen well, and takes corresponding measure.The method of monitoring is to analyze the percentage composition of nitrogen in each producing well institute aerogenesis body, gas production change, the change of nitrogen percentage composition in real time.When finding nitrogen percentage composition exception well and other ANOMALOUS VARIATIONS, need, according to coalbed methane reservoir characteristic, note nitrogen history (note nitrogen pressure, speed etc. change history), producing well history (the change history such as well head pressure, gas production, each gas componant volumn concentration), to do corresponding disposal；Conversion if desired uses vibration pattern of pressure.

Pressure control program and the method for the note nitrogen volume increase coal bed gas shown in Fig. 3 are summary discussed above and materialization, graphical achievement.In figure " well head pressure > coal seam hydrostatic pressure？" it is that " producing well well head pressure is more than coalbed methane reservoir initial reservoir pressure and more than hydrostatic pressure？" abbreviation；" nitrogen percentage composition " refers to " volumn concentration of nitrogen in producing well institute aerogenesis body "；" abnormal producing well " is the abbreviation of " nitrogen percentage composition exception well ".

Fig. 3 is applicable to the note nitrogen of any coalbed methane reservoir and increases solution volume increase Stress control, it is adaptable to note nitrogen increasing solves starting stage, transition stage and stabilization sub stage.In the preceding paragraphs, discuss high permeability coalbed methane reservoir and low-permeability coalbed methane reservoir respectively the different of note nitrogen pressure are required and repercussion.Fig. 3 does not has which part of clear and definite flow process to be applicable to high permeability coalbed methane reservoir, and which part is applicable to low-permeability coalbed methane reservoir, because should not be also impossible to do the clearest and the most definite differentiation.To this, it is explained as follows: (1) " high permeability coalbed methane reservoir ", " low-permeability coalbed methane reservoir ", is all concept qualitatively, there is no clear and definite boundary line.Between high permeability coalbed methane reservoir and low-permeability coalbed methane reservoir, it is also possible to have medium permeability coalbed methane reservoir.Permeability is high or low, and in different places, to different people, standard is difficult to unified.This does not denies that " high permeability coalbed methane reservoir ", " low-permeability coalbed methane reservoir " are objective reality.(2) coalbed methane reservoir is that Local enrichment height oozes.In one coal layer gas exploration, some coal bed gas block coal seam permeabilities are higher, and other coal bed gas block coal seam permeabilities are relatively low.In same coal bed gas block, possible coal seam permeability is the highest, also has the position of low-permeability；It is likely to coal seam permeability the most relatively low, also has the position of high permeability；Likely high permeability coal seam and low-permeability coal seam are that patch shape is inlayed.(3) solving under yield-increasing technology pattern in note nitrogen increasing, coalbed methane reservoir permeability is probably the unknown, because note nitrogen increases solution yield-increasing technology and the most do not does pressure break, the most just obtains permeability not over methods such as pressure break tests.The present invention is not to distinguish high permeability coalbed methane reservoir and low-permeability coalbed methane reservoir according to the artificial permeability measured, but according to reservoir to note nitrogen pressure, the repercussion of note nitrogen speed, it is judged that permeability height, adjust note nitrogen pressure and producing well gas production.(4) increase the production period solving volume increase up to more than ten years at note nitrogen, coal seam permeability will be because desorption-blockage effect will increase lentamente, and low-permeability coal seam originally may be gradually converted into high permeability coal seam.Therefore, formulating different pressure control program respectively for high permeability coalbed methane reservoir, low-permeability coalbed methane reservoir, even if formulating, also cannot follow.

While it is true, the Stress control flow process of the leftmost side is more closely relevant to low-permeability coalbed methane reservoir in Fig. 3.If " note nitrogen speed<predetermined note nitrogen speed " condition is set up, and " note nitrogen pressure>coal seam fracture pressure " condition is also set up, and this coalbed methane reservoir is not only low-permeability, and is probably very low-permeability.Especially, only low-permeability coalbed methane reservoir its is possible to use last option of the Stress control flow process of the leftmost side in Fig. 3 " to be converted to high-voltage oscillation pattern of pressure ".Similarly, in Fig. 3, the Stress control flow process of the rightmost side is more closely relevant to high permeability coalbed methane reservoir.In the starting stage, if " note nitrogen speed<predetermined note nitrogen speed " condition is false (i.e. " note nitrogen speed predetermined note nitrogen speed " condition is set up), and " note nitrogen pressure>coal seam fracture pressure " condition is also false (i.e. " note nitrogen pressure<coal seam fracture pressure " condition is also set up), and this coalbed methane reservoir is likely to high permeability；If going back establishment condition " well head pressure < coal seam hydrostatic pressure ", substantially can affirm that this coalbed methane reservoir is high permeability, in some instances it may even be possible to be very low-permeability.Especially, only high permeability coalbed methane reservoir its is possible to use last option of the Stress control flow process of the rightmost side in Fig. 3 " to be converted to low pressure vibration pattern of pressure ".In whole note nitrogen flow process, the present invention is not to select note nitrogen pressure, note nitrogen speed according to coalbed methane reservoir permeability, but by coalbed methane reservoir to note nitrogen well note nitrogen pressure, note the repercussion i.e. well head pressure of producing well of nitrogen speed, gas production, the change of nitrogen volumn concentration, feed back to note nitrogen well, adjust note nitrogen pressure, note nitrogen speed.

Fig. 3 is applicable to note nitrogen and increases solution volume increase starting stage, transition stage and stabilization sub stage.The note nitrogen of one coal bed gas block increases to solve to increase production the production period up to the several years to more than ten years.In whole production period, it is required for note nitrogen pressure, speed, the well head pressure of producing well, gas production, each isoparametric change of gas componant volumn concentration according to note nitrogen well, according to the flow process of Fig. 3, judge, note nitrogen pressure, lines of producing wells tolerance according to judging to adjust.

Fig. 3 is applicable to note nitrogen and increases the overall process solving volume increase.Fig. 3 is not only suitable for high permeability coalbed methane reservoir, is also applied for low-permeability coalbed methane reservoir.This increases solution volume increase starting stage, transition stage and stabilization sub stage with aforementioned at note nitrogen, and note nitrogen Stress control should be different, not contradiction；Also with aforementioned to high permeability coalbed methane reservoir, low-permeability coalbed methane reservoir, it should use different note nitrogen Stress control.The most not contradiction.Fig. 3 notes the Logic judgment in nitrogen Stress control flow process and ensure that Fig. 3 notes the general applicability of nitrogen Stress control flow process, also demonstrates the general applicability of technical solution of the present invention.

After the present invention controls the note theory of nitrogen pressure, method, program when note nitrogen being discussed in detail and having increased and solve volume increase coal bed gas, pressure control program and the method for summing up the note nitrogen volume increase coal bed gas that the present invention provides are as follows:

The present invention relates to a kind of pressure control program noting nitrogen volume increase coal bed gas and method.Specifically, the present invention relates to a kind of from flatly or the many mouthfuls of note nitrogen wells connected with coal seam are to coal seam nitrogen injection, promote hydrocarbon gas desorption, the mixed gas of the hydrocarbon gas of outputs and hydrocarbon gas and nitrogen is gathered from the many mouthfuls of producing wells that connect with coal seam, when increasing solution volume increase coal bed gas, the pressure control program used and method, enter inside coal seam with the nitrogen reaching to make to be injected into, whole coal seams between inswept note nitrogen well and producing well, nitrogen is made to enter micropore, coal seam, ADSORPTION STATE coal bed gas is promoted to desorb, and the free state coal bed gas after drive row desorption is to producing well, reach to increase production the purpose of coal bed gas.Concrete pressure controlling step, flow process and method are as follows:

Although coalbed methane reservoir permeability does not occurs in Logic judgment as a parameter in figure 3, but, this and " according to coalbed methane reservoir permeability, use different note nitrogen pressure " not contradiction described in (b) item.Coalbed methane reservoir permeability does not the most occur in as a parameter in the Logic judgment of Fig. 3, is because coalbed methane reservoir permeability and is probably the unknown, it may be possible to spatial variations, it may be possible to the change of note nitrogen time.Coalbed methane reservoir permeability is the principal element of impact note nitrogen pressure, even if this parameter occurs in note nitrogen Stress control flow chart, the influence power that note nitrogen pressure is selected by this parameter shows no sign of being compromised.

It is last that it is noted that Fig. 3 is one implements note nitrogen volume increase coal bed gas pressure control program and the typical flow chart of method that the present invention provides, Fig. 3 is the part of the present invention, and and unrestricted technical scheme described in the invention.Therefore, although this specification is to present invention has been detailed description, but, it will be understood by those within the art that, still Fig. 3 and the present invention can be modified or equivalent；And all are without departing from the technical scheme of the spirit and scope of the present invention and improvement thereof, all should contain in scope of the presently claimed invention.

Claims

1. desorb, from many to a coal seam nitrogen injection, promotion hydrocarbon gas from a bite or the many mouthfuls of note nitrogen wells connected with coal seam The producing well that connect with coal seam of mouth gathers the hydrocarbon gas of output and hydrocarbon gas and the mixed gas of nitrogen, increases solution and increases production coal seam During gas, the compress control method of use, it is characterized in that:

(c) monitoring producing well well head pressure, nitrogen percentage composition, capacity；

D (), to high permeability coalbed methane reservoir, in starting stage and transition stage, builds the pressure, make note nitrogen pressure more than initial reservoir Pressure and more than coal seam hydrostatic pressure；

(e) to high permeability coalbed methane reservoir, when nitrogen percentage composition exception well occurs, keep note nitrogen speed on the premise of, Selectively reduce nitrogen percentage composition exception well array tolerance, or reduce note nitrogen pressure, or to reduce nitrogen percentage composition different simultaneously Normal well array tolerance also reduces note nitrogen pressure；

F (), to high permeability coalbed methane reservoir, when there is nitrogen percentage composition exception well, is reducing note nitrogen pressure to less than just Beginning reservoir pressure and less than after hydrostatic pressure, if nitrogen percentage composition exception well quantity continues to increase or nitrogen percentage composition with The speed of the change of time continues to become big singularly, and conversion uses low pressure vibration pattern of pressure；

G () to low-permeability coalbed methane reservoir, is keeping predetermined note nitrogen speed and note nitrogen pressure more than initial reservoir pressure and big In coal seam hydrostatic pressure but on the premise of being much smaller than coalbed methane reservoir roof rock and floor rocks fracture pressure, use the least Note nitrogen pressure；

H (), to low-permeability coalbed methane reservoir, in starting stage and transition stage, is more than coal seam fracture pressure also at note nitrogen pressure And still note nitrogen speed still less than predetermined note nitrogen speed much smaller than coalbed methane reservoir roof rock and floor rocks fracture pressure In the case of, conversion uses high-voltage oscillation pattern of pressure；

H (), to low-permeability coalbed methane reservoir, when there is nitrogen percentage composition exception well, is reduced note nitrogen pressure, or is selected Property reduce nitrogen percentage composition exception well array tolerance, or reduce note nitrogen pressure reduce nitrogen percentage composition exception well array gas simultaneously Amount；

I (), to low-permeability coalbed methane reservoir, when there is nitrogen percentage composition exception well, is reducing note nitrogen pressure to less than coal Layer fracture pressure is then noted nitrogen speed and is noted nitrogen speed less than predetermined, raises note nitrogen pressure to much smaller than roof country rock and floor rocks Fracture pressure then nitrogen percentage composition exception well quantity increases or nitrogen percentage composition speed over time continues singularly In the case of becoming greatly, conversion uses high-voltage oscillation pattern of pressure；

J () increases solution at note nitrogen and increases production in whole production period, according to note nitrogen pressure, note nitrogen speed, the well head of producing well of note nitrogen well Pressure, gas production, the change of nitrogen volumn concentration, judge, and notes nitrogen pressure, producing well exhaust according to judging to adjust Amount.

Method the most according to claim 1, the wherein said note nitrogen starting stage, is characterized in that the fluid in coal seam is basic On be a phase liquid water, wherein said note nitrogen transition stage, it is characterized in that the fluid in coal seam is water and gas two-phase fluid, The wherein said note nitrogen stabilization sub stage, it is characterized in that the fluid in coal seam is substantially a phase gas, be hydrocarbon gas, nitrogen Mixed gas.

Method the most according to claim 1, wherein said builds the pressure, and it is characterized in that reducing lines of producing wells tolerance, the completeest Contract fully producing well aerogenesis valve, promotes coalbed methane reservoir pressure to raise, make reservoir pressure reach more than initial reservoir pressure and More than coal seam hydrostatic pressure.

Method the most according to claim 1, wherein said nitrogen percentage composition exception well, it is characterized in that producing well is produced The nitrogen volumn concentration of gas is singularly higher than other wells, or the speed that nitrogen percentage composition is over time is singularly Become big, or well head pressure becomes big singularly.

Method the most according to claim 1, wherein said low pressure vibration pattern of pressure, it is characterized in that, note nitrogen pressure with Time oscillation changes, and the interval of pressure oscillation change is, minimum note nitrogen pressure is substantially smaller than the initial pressure of coalbed methane reservoir also And substantially smaller than coal seam hydrostatic pressure, maximum note nitrogen pressure is more than the initial pressure of coalbed methane reservoir and more than coal seam hydrostatic pressing Power, and substantially smaller than coal seam fracture pressure, alternately use minimum note nitrogen pressure, maximum note nitrogen pressure, using minimum note During nitrogen pressure, it is allowed to note nitrogen speed, less than predetermined note nitrogen speed, during using low pressure vibration pattern of pressure, keeps producing well well head Pressure is more than the initial pressure of coalbed methane reservoir and more than coal seam hydrostatic pressure.

Method the most according to claim 1, wherein said high-voltage oscillation pattern of pressure, it is characterized in that, note nitrogen pressure with Time oscillation changes, and the interval of pressure oscillation change is, minimum note nitrogen pressure is more than the initial pressure of coalbed methane reservoir and is more than Hydrostatic pressure, maximum note nitrogen pressure is less than roof country rock and the fracture pressure of floor rocks, and guarantees to push up in pressure break coal seam Plate country rock and floor rocks, alternately use minimum note nitrogen pressure, maximum note nitrogen pressure, when using minimum note nitrogen pressure, permit Permitted note nitrogen speed less than predetermined note nitrogen speed.

Method the most according to claim 1, wherein said step (a) to (j), it is characterized in that, the well of producing well Note nitrogen well is noted nitrogen pressure, is noted nitrogen speed as coalbed methane reservoir by mouth pressure, gas production, the change of nitrogen volumn concentration Repercussion, feeds back to note nitrogen well, adjusts note nitrogen pressure, note nitrogen speed.

Method the most according to claim 1, wherein said predetermined note nitrogen speed is that the unit interval is interior through note nitrogen well note flatly Enter the nitrogen volume under the status of criterion in coal seam, chronomere be hour or day, when having many mouthfuls of note nitrogen wells, it is allowed to each notes nitrogen well There is different predetermined note nitrogen speed.

Method the most according to claim 1, wherein said nitrogen is high-purity nitrogen or the gas with nitrogen as main component Body.

Method the most according to claim 9, the wherein said gas with nitrogen as main component is chimney gas, blast furnace Gas.