CN110410054A - A kind of coal bed gas well fracturing fracture becomes the prediction technique of space-time flow conductivity - Google Patents
A kind of coal bed gas well fracturing fracture becomes the prediction technique of space-time flow conductivity Download PDFInfo
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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- E21B43/26—Methods for stimulating production by forming crevices or fractures
- E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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Abstract
The invention discloses the prediction techniques that a kind of coal bed gas well fracturing fracture becomes space-time flow conductivity, comprising the following steps: S1, the reservoir rock relevant parameter for collecting target coal seam gas well；The spatial distribution of initial time supporting crack universe flow conductivity after S2, calibration pressure break；S3, coal dust deposition is established, the mechanism expression formula that proppant embedment and time influence proppant pack fracture condudtiviy；S4, the flow conductivity value of different moments each discrete unit is obtained to the universe flow conductivity progress spatial spreading demarcated in step S2 according to the flow conductivity change mechanism model having built up；S5, using the calculated result of step S4 as starting point, repeat step S3~S4, until by universe flow conductivity calculating finish.The shortcomings that predicting flow conductivity the present invention overcomes existing laboratory experiment after realizing coal bed gas well pressure break, considers coal dust deposition and injury of the proppant embedment to flow conductivity, reaches the ability that the change space-time water conservancy diversion in universe proppant pack crack can be effectively predicted.
Description
Technical field
The present invention relates to coal-bed-gas production-increases, and field technical field is transformed, and in particular to a kind of coal bed gas well fracturing fracture change
The prediction technique of space-time flow conductivity.
Background technique
China's Coal bed gas project is abundant, and geological resources occupy third place in the world, and exploitation prospect is wide.Due to it
Unique occurrence status and reservoir properties, establishing effective fracture network by hydraulic fracturing is the key that cbm development.But
After pressure break in coal bed gas well mining Practice, since coal dust can settle blocking coal seam fracture system, coal seam infiltration is significantly reduced
Rate, cause to be substantially reduced water yield, coal bed gas desorption slowly, the formation of gas well industrial output is caused to seriously affect, because
This, the migration rule of studying coal powder, the output for controlling coal dust has become the key of coal bed gas well high yield, stable yields.
It is obtained since the flow conductivity of proppant pack is difficult to measure by downhole hardware, at present proppant water conservancy diversion energy
Power is evaluated mainly based on laboratory experiment, but can only also obtain the average flow conductivity under Fracture System changes over time.It is
Utilize API guiding device, it then follows evaluation criterion include short-term water conservancy diversion experiment RP-61 and long-term water conservancy diversion experiment ISO 13503-
5.Long-term water conservancy diversion experimental data can more embody supporting crack flow conductivity and change with time in the earth formation trend, but each pressure
The testing time in force is more than 50 more than hour, if high temperature and pressure experiment condition surveys the more demanding of experimental facilities
It is long, at high cost to try the period.
Relative to fracture condudtiviy laboratory experiment method, establish analytic modell analytical model predicted it is more economical quick. Gao
Single layer, the contact of Multi-layer supporting agent and incorporation model are given with Li et al. people, the proppant under specific clossing pressure can be calculated
Contact, insertion and fracture aperture situation of change (Li K, Gao Y, Lyu Y, et al.New mathematical models
for calculating proppant embedment and fracture conductivity[J].SPE Journal,
2015,20 (03): 496-507) .Guo et al propose consider creep of rock effect the long-term incorporation model (Guo of proppant
J,Liu Y.Modeling ofproppant embedment:elastic deformation and creep
deformation[C]//SPE International Production and Operations Conference&
Exhibition.Society ofPetroleum Engineers,2012).T.Iwasaki(IWASAKI T,SLADE J J,
STANLEY W E.Some notes on sand filtration[with discussion][J].
1937,29 (10): AmericanWaterWorks Association 1591-1602.) etc. has initially set up in-depth filtration system
The mathematical model of particle migration in system is laid a good foundation for suspended particulate migration-deposition characteristics research in porous media, it
Classical transport-sedimentation model based on amounts of particles balance and sediment dynamics equation is formed again afterwards, because it can predict porous Jie
Matter blockage, particle migration distance etc., and calculated result and experimental data have good consistency, and be widely used
In fields such as petroleum works.
Forefathers are comprehensively considering proppant deformation, rock wall surface shape in the research model of supporting crack flow conductivity
Become, the research deficiency of insertion influence, lacks the research in terms of coal dust migration blocks the filling of supporting crack.When laboratory experiment,
Its surface will form class clay pore filling mine after proppant is stood for a long time in water flooding (or manually preparing water flooding)
Object, and rock surface diagenesis precipitation.After coal petrography pressure break, with the progress of production process, coal dust will also be filled in proppant
Packing course gradually deposits, and blocks crack, reduces fracture porosity and permeability, leads to the forfeiture of fracture condudtiviy.The present invention
Coal will be established for several respects such as proppant particles Elastic Contact, wall surface deformation, proppant embedment and coal dust migration fillings
Rock pressure splits supporting crack flow conductivity prediction model.
Summary of the invention
In view of the above-mentioned problems, the present invention provides a kind of prediction technique of coal bed gas well fracturing fracture change space-time flow conductivity,
Its object is to overcome existing laboratory experiment prediction flow conductivity, after realizing coal bed gas well pressure break, coal dust deposition is considered
Injury with proppant embedment to flow conductivity reaches the change space-time water conservancy diversion that universe proppant pack crack can be effectively predicted
Ability.
The present invention uses following technical solutions:
A kind of coal bed gas well fracturing fracture becomes the prediction technique of space-time flow conductivity, comprising the following steps:
S1, the reservoir rock mechanics parameter for collecting target coal seam gas well, completion parameter, fracturing parameter, stratum ginseng
Number；
S2, using Fracturing Pressure inversion technique, demarcate initial time supporting crack universe flow conductivity after pressure break
Spatial distribution；
S3, coal dust deposition is established, the mechanism table that proppant embedment and time influence proppant pack fracture condudtiviy
Up to formula；
The flow conductivity that S4, basis have built up is in different time with coal dust migration deposition, proppant embedment change mechanism
Model carries out spatial spreading to the universe flow conductivity demarcated in step S2, obtains leading for different moments each discrete unit
Flow ability value；
S5, using the calculated result of step S4 as starting point, step S3~S4 is repeated, until universe flow conductivity is calculated
It finishes.
Preferably, the Fracturing Pressure inversion technique are as follows: be to lead target well formation parameter and pressure construction parameter
Enter fracturing fracture simulation softward, fitting obtains the fracture pattern at the end of pressing crack construction, obtain the form in original manual crack with
And initial flow conductivity distribution in crack.
Preferably, the mechanism expression formula are as follows: by proppant pack dynamic slit width and supporting crack active diversion ability
Product coupling is carried out by time relationship.
Preferably, the proppant pack dynamic slit width are as follows: after coal petrography, the mechanical characteristics of proppant and pressure break
Flowing bottomhole pressure (FBHP) variation, establishes the computation model for considering that proppant pack slit width changes over time, comprising the following steps:
A, it is tested by three axis rock mechanics parameters, obtains the mechanics parameter of coal petrography rock sample and proppant material, be model
Necessary basis parameter is provided；
B, according to mining data after pressure break, flowing bottomhole pressure (FBHP) is calculated, and then seam fluid pressure is calculated, thus
Different moments crack wall surface effective stress is calculated.
Preferably, the supporting crack active diversion ability are as follows: coal dust deposition blocking pair is considered based on classical filtration theory
The computation model for considering that proppant pack permeability changes over time is established in the influence of porosity, comprising the following steps:
I, coal dust deposition system is obtained to the arresting efficiency of coal dust and the porosity calculation of proppant pack according to proppant
Number；
II, the branch after coal dust deposition blocking is calculated according to the coal powder density in coal dust sedimentation coefficient and sand packed fracture
Support fracture porosity；
III, the fracture permeabgility after coal dust deposition blocking is obtained according to K-C equation.
The beneficial effects of the present invention are:
1, the present invention combines coal petrography physical parameter, fracturing parameter, drainage and mining parameters etc., after effectively can combining pressure break
Actual production data realize pre- to dynamic of flow conductivity during crack is gradually closed, coal dust constantly deposits blocking
It surveys.
2, the present invention considers the flow conductivity distribution situation that universe proppant pack crack becomes space-time, can get along seam
Deposition conditions and deposition of the length direction coal dust at each point change with time trend, avoid forefathers select it is different
The change time combines the method defect being simply multiplied with emptying empirical function.
3, the present invention can more reflect the timeliness and stress sensitive of supporting crack flow conductivity compared with laboratory experiment simultaneously
Property, the more accurate prediction water conservancy diversion out-of-service time.
Detailed description of the invention
In order to illustrate the technical solution of the embodiments of the present invention more clearly, will make simply to the attached drawing of embodiment below
It introduces, it should be apparent that, the accompanying drawings in the following description merely relates to some embodiments of the present invention, rather than to limit of the invention
System.
Fig. 1 is initial flow conductivity distribution schematic diagram in the form and crack of man-made fracture of the present invention；
Fig. 2 is two sphere Elastic Contact schematic diagrames in the present invention；
Fig. 3 is target coal seam gas well Production curve schematic diagram of the present invention；
Fig. 4 is present invention flow conductivity distribution schematic diagram in crack after 1 year；
Fig. 5 is flow conductivity distribution schematic diagram in crack after 3 years in the present invention；
Fig. 6 is flow conductivity distribution schematic diagram in crack after 5 years in the present invention；
Specific embodiment
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
Attached drawing, the technical solution of the embodiment of the present invention is clearly and completely described.Obviously, described embodiment is this hair
Bright a part of the embodiment, instead of all the embodiments.Based on described the embodiment of the present invention, the common skill in this field
Art personnel every other embodiment obtained under the premise of being not necessarily to creative work, shall fall within the protection scope of the present invention.
Unless otherwise defined, the technical term or scientific term that the disclosure uses are should be in disclosure fields
The ordinary meaning that personage with general technical ability is understood.The similar word such as " comprising " or "comprising" used in the disclosure
The meaning of one's words points out that element or object before the existing word are covered the element for appearing in the word presented hereinafter or object and its waited
Together, other elements or object are not excluded for."upper", "lower", "left", "right" etc. are only used for indicating relative positional relationship, work as quilt
After the absolute position of description object changes, then the relative positional relationship may also correspondingly change.
Present invention will be further explained below with reference to the attached drawings and examples.
As shown in Figures 1 to 6, a kind of coal bed gas well fracturing fracture becomes the prediction technique of space-time flow conductivity, including following
Step:
S1, collection target coal seam gas well basic parameter (by taking Qinshui basin block coal bed gas well as an example) include: reservoir rock
Stone mechanics parameter, completion parameter, fracturing parameter, formation parameter, as shown in table 1:
1 target coal seam gas well mechanics of table and completion parameter
2 target coal seam gas well of table pump note program parameter
S2, using Fracturing Pressure inversion technique, especially construction net pressure fitting technique is demarcated initial after pressure break
The spatial distribution of moment (at the end of pressing crack construction) supporting crack universe flow conductivity；The Fracturing Pressure inversion technique
It is that target coal seam gas well mechanics, completion parameter and pressure construction parameter are used into fracturing fracture simulation softward (including but not limited to
Fracpro PT software), fitting obtains the fracture pattern at the end of pressing crack construction, obtain original manual crack form and
Initial flow conductivity distribution in crack, as shown in Figure 1.
Hydraulic fracture incipient crack form and flow conductivity distribution map are obtained according to underlying parameter and pressing crack construction data,
The fracture pattern is discrete according to 1m × 5m, obtain the initial flow conductivity example of certain points of the flow conductivity distribution map such as
Under:
| Coordinate (m, m) | Flow conductivity (mDm) | Coordinate (m, m) | Flow conductivity (mDm) |
| (0,0) | 3000 | (10,0) | 2600 |
| (0,10) | 2500 | (10,10) | 2000 |
| (0,-10) | 2450 | (10,-10) | 2010 |
The initial flow conductivity table of 3 target coal seam gas well of table
S3, coal dust deposition is established, the mechanism table that proppant embedment and time influence proppant pack fracture condudtiviy
Up to formula；The mechanism expression formula are as follows: by proppant pack dynamic slit width (crack slit width) and supporting crack active diversion ability
Product coupling is carried out by time relationship.
The proppant pack dynamic slit width are as follows: according to flowing bottomhole pressure (FBHP) after coal petrography, the mechanical characteristics of proppant and pressure break
The computation model for considering that proppant pack slit width changes over time is established in variation, comprising the following steps:
A, it is tested by three axis rock mechanics parameters, obtains mechanics parameter (including the bullet of coal petrography rock sample and proppant material
Property modulus, Poisson's ratio), necessary basis parameter is provided for model；
B, according to liquid level, the casing pressure (well head pressure) after pressure break in mining data, flowing bottomhole pressure (FBHP) is calculated, into
And seam fluid pressure (seam fluid pressure is approximately equal to bottom pressure) is calculated, it is split so that different moments be calculated
Slotted wall face effective stress.
The flowing bottomhole pressure (FBHP), the calculation formula of crack wall surface effective stress are as follows:
Pc=σmin-Pwf (1)
Pwf=Psurface+Phydrostatic-Ppf (2)
In formula: Pc- crack wall surface effective stress, MPa；Pwf- flowing bottomhole pressure (FBHP), MPa；Psurface- well head pressure, MPa；
Phydrostatic- well liquid injection pressure power, MPa；Ppf- Kong Zhaoxia；σmin- minimum horizontal principal stress, MPa；Wherein well liquid
Injection pressure power and Kong Zhaoxia can obtain (prior art) according to the art conventional Calculation Method.
As shown in figure 3, the casing pressure after 1 year is 0.16MPa, liquid level 670m, roof height is 776m, well
Cylinder liquid injection pressure power is 1.2MPa, and wellbore frictional resistance is 2MPa, and it is 8.8MPa that crack wall surface effective stress, which is calculated,.
The calculation formula of the proppant pack dynamic slit width is as follows:
In formula, w-proppant pack dynamic slit width (crack slit width), m；wideal- ideal/dynamic slit width, m；N-
Support oxidant layer number, dimensionless, Δ dppDiameter after being contacted between-proppant particles, m；Δdrock-p- proppant particles and sides of fracture
Amount of elastic deformation after face contact, m, h-proppant embedment rock depth；
The Δ dpp、Δdrock-p, h is calculated by following formula:
The Elastic Contact of proppant:
After contact in 2 spheres or outer contacting stress, due to the flexible deformation of material, so that contact point is to adjacent to four
Week gradually extends and becomes the circle that radius is c.According to known to Elasticity knowledge:
Contact the radius of circle:
In formula: E is equivalent elasticity modulus, MPa；F is the normal direction contact pressing force being pressed on two spheres, N；ρ is that equivalent is bent
Rate radius, m, calculation formula are as follows:
Er、ERThe respectively elasticity modulus of spherula and big ball material, MPa；μr、μRRespectively spherula and big sphere
The Poisson's ratio of material；R, R is respectively that spherula and big sphere initially contact the radius of curvature pointed out, m；Contact form is represented, is born
Contact in number "-" is corresponding, indicates that the center of 2 spheres be in the same side of contact point, as sphere is contacted with ball seat, sphere and
The contact of recessed raceway ditch, positive sign "+" correspond to outer contacting, indicate that the center of 2 spheres is in the two sides of contact point, as sphere with it is interior
Raceway contacts.
Proppant particles and sides of fracture face contact
F1=σmin·π·c1 2 (7)
In formula: F1For proppant particles and sides of fracture face contact pressing force, N；σminFor horizontal minimum principal stress, MPa；c1
Radius of circle, m are contacted for proppant particles and sides of fracture face contact position；Ep、ErockThe respectively bullet of proppant particles and rock
Property modulus, MPa；μp、μrockThe respectively Poisson's ratio of proppant particles and rock；ρ1For proppant particles and sides of fracture face contact
Normal radius of curvature, m；d0For proppant particles initial diameter, m.
Contact between proppant particles:
According to Elasticity knowledge and Newton's third law:
F2=F1 (11)
In formula: F2Contact pressing force between proppant particles, N；c2Contact position contacts between proppant particles
Radius of circle, m；ρ2The normal radius of curvature contacted between proppant particles, m；.
After solution obtains the contact pressure between two elastomers, stress caused by contact pressure can be further determined that
And deformation.Be analyzed as follows: two elastomers are all spherosomes, and radius is respectively R1And R2, as shown in Figure 3.When there is no pressure
When effect, only O is contacted two spheres on one point.If two spheres show on away from common normal be r M1And M2Point, they cut away from public
The distance in face is respectively z1And z2, then had by geometrical relationship:
(r-z2)2+c2 2=r2 (16)
It therefore deduces that
In formula: M1And M2It is close from contact point O, then Z1Much smaller than 2R, Z2Much smaller than 2r, it is believed that above formula is set up.
Therefore M1And M2The distance between are as follows:
That is, after being contacted between proppant particles and sides of fracture face contact or proppant particles, under the action of clossing pressure
Its effective diameter will become smaller, changing value are as follows:
It is further derived from, the amount of elastic deformation after proppant particles and sides of fracture face contact are as follows:
Diameter after being contacted between proppant particles are as follows:
The insertion of proppant:
The final goal of hydraulic fracturing is the supporting crack for forming a high flow conductivity in the earth formation, in crack closure
Afterwards, proppant and crack and interaction, the phenomenon that generating proppant embedment rock, is (this phenomenon in soft formation, such as page
It is especially pronounced in rock).Lead to the reduction of supporting crack width after proppant embedment, and then reduces fracture condudtiviy.Therefore, have
Necessity studies the proppant embedment behavior in pressing crack construction process.
Assuming that:
It is that a standard is spherical 1. proppant particles sphericity is good；
2. proppant in rock table and be embedded as linear deformation；
3. proppant particles intensity is sufficiently large, when embeddeding action occurs to rock, proppant is not crushed, and will not be generated
Deformation；
4. embedding depth of proppant is no more than its partial size.
According to Hertz elastic contact theory, the depth of proppant embedment rock is denoted as h, then is had:
In formula: μ1The Poisson's ratio of-rock, dimensionless；μ2The Poisson's ratio of-proppant, dimensionless；E1The elasticity of-rock
Modulus, MPa；E2The elasticity modulus of-proppant, MPa, pc- clossing pressure, MPa, in the present embodiment, clossing pressure, which is equal to, to be split
Seam avoids effective stress, it may be assumed that pc=pnet。
Connection column formula (21), (22), (23) can acquire proppant pack dynamic slit width w.By bringing above-mentioned parameter into
Crack slit width can be obtained are as follows: 0.034cm.
The supporting crack active diversion ability are as follows: consider coal dust deposition blocking to porosity based on classical filtration theory
Influence, establish and consider the computation model that changes over time of proppant pack permeability, comprising the following steps:
I, the arresting efficiency of coal dust and the porosity (porosity of porous medium) of proppant pack are counted according to proppant
Calculation obtains coal dust sedimentation coefficient；
II, the branch after coal dust deposition blocking is calculated according to the coal powder density in coal dust sedimentation coefficient and sand packed fracture
Support fracture porosity；
III, the fracture permeabgility after coal dust deposition blocking is obtained according to K-C equation.
Coal dust deposition blocking
Proppant pack is considered as porous media, coal dust deposition blocking is analyzed according to classical filtration theory.
(1) classical filtration theory basic assumption:
1. particle deposit process is irreversible；
2. being uniform flow field under pore scale；
3. surface is uniformly injected into；
4. not considering size exclusion effect and filtration.
Amounts of particles equilibrium equation and sediment dynamics equation are 2 most important parts of classical filtration theory.When assuming that
Seepage flow condition is that one-dimensional stationary flow can be used Data compatibility and describe suspended particulate when porous media is saturation, homogeneous
Migration feature.According to classical filtering model, suspended particulate sedimentation coefficient k may be expressed as: with collector collection efficiency η relationship
φ is porosity of porous medium in formula, and u is suspended particulate speed, dcFor the diameter of collector.
Scholar proposes that collector collection efficiency is the stack result of interception function, precipitation and diffusion.
η=ηi+ηs+ηd (25)
As is Happel modifying factor, d in formulapFor particle diameter, m；dcFor collector diameter, ρsGrain density, ρ are stream
Volume density, a are acceleration,For porosity, μ is coefficient of dynamic viscosity, and D is particle dispersion coefficient, and H is Hamaker constant.
Process to simplify the analysis, engineering often ignore hydrodynamic dispersion effect to suspended particulate migration-deposition process in practice
Influence, and assume that particle sedimentation coefficient does not change with space and time.For one-dimensional injection problem, it is assumed that when initial
Carving is the pure interstitial space without suspended particulate inside porous media, injects suspension at x=0 with uniform concentration, then
Acquire analytic solutions are as follows:
C (x) is concentration of suspended particles, C in formula0For original suspension granule density, t0Duration, σ (x) are injected for particle
To be deposited on the ratio between intrapore particle volume and porous media solid portion volume (coal dust sedimentation coefficient).
Supporting crack porosity after considering coal dust deposition blocking indicates are as follows:
φ (x, t)=φ (x, t- Δ t)-σ (x, t) (1- φ (x, t- Δ t)) (32)
Fracture permeabgility:
mkAnd nkFor the empirical in penetration rate model, value in the present embodiment are as follows: 1.
Consider coal dust initial concentration and coal dust migration velocity when calculating fracture permeabgility, in this example, coal dust initial concentration
0.03% is taken, coal dust migration velocity value 0.05m/s.
Connection column formula (3) and (34) can acquire multifactor lower fracture condudtiviy, and calculation formula is as follows:
FRCD (x, t)=K (x, t) w (x, t) (34)
The flow conductivity that S4, basis have built up is in different time with coal dust migration deposition, proppant embedment change mechanism
Model carries out spatial spreading to the universe flow conductivity demarcated in step S2, obtains leading for different moments each discrete unit
Flow ability value.
The flow conductivity value of the above-mentioned point (table 3) in the crack after calculating 1 year (360d):
| Coordinate (m, m) | Flow conductivity (mDm) | Coordinate (m, m) | Flow conductivity (mDm) |
| (0,0) | 2200 | (10,0) | 1800 |
| (0,10) | 1300 | (10,10) | 1000 |
| (0,-10) | 1800 | (10,-10) | 1600 |
S5, using the calculated result of step S4 as starting point, step S3~S4 is repeated, until universe flow conductivity is calculated
It finishes.
Similarly the flow conductivity after the available production several years is distributed, after selecting 1 year in this example, after 3 years, after 5 years
Flow conductivity cloud charts are such as schemed
The above described is only a preferred embodiment of the present invention, be not intended to limit the present invention in any form,
Although the present invention has been disclosed as a preferred embodiment, however, it is not intended to limit the invention, any technology for being familiar with this profession
Personnel, without departing from the scope of the present invention, when the technology contents using the disclosure above make a little change or repair
Decorations are the equivalent embodiment of equivalent variations, but anything that does not depart from the technical scheme of the invention content, technology according to the present invention are real
Matter any simple modification, equivalent change and modification to the above embodiments, still fall within the range of technical solution of the present invention
It is interior.
Claims (5)
1. the prediction technique that a kind of coal bed gas well fracturing fracture becomes space-time flow conductivity, which comprises the following steps:
S1, reservoir rock mechanics parameter, completion parameter, fracturing parameter, the formation parameter for collecting target coal seam gas well；
S2, using Fracturing Pressure inversion technique, demarcate the space of initial time supporting crack universe flow conductivity after pressure break
Distribution；
S3, coal dust deposition is established, the mechanism expression formula that proppant embedment and time influence proppant pack fracture condudtiviy；
S4, according to the flow conductivity that has built up in different time with coal dust migration deposition, proppant embedment change mechanism model,
Spatial spreading is carried out to the universe flow conductivity demarcated in step S2, obtains the flow conductivity of different moments each discrete unit
Value；
S5, using the calculated result of step S4 as starting point, repeat step S3~S4, until by universe flow conductivity calculating finish.
2. a kind of coal bed gas well fracturing fracture according to claim 1 becomes the prediction technique of space-time flow conductivity, feature
It is, the Fracturing Pressure inversion technique are as follows: be that target well formation parameter and pressure construction parameter are imported into fracturing fracture
Simulation softward, fitting obtain the fracture pattern at the end of pressing crack construction, obtain in the form and crack in original manual crack just
The distribution of beginning flow conductivity.
3. a kind of coal bed gas well fracturing fracture according to claim 1 becomes the prediction technique of space-time flow conductivity, feature
It is, the mechanism expression formula are as follows: close proppant pack dynamic slit width and supporting crack active diversion ability by the time
System carries out product coupling.
4. a kind of coal bed gas well fracturing fracture according to claim 3 becomes the prediction technique of space-time flow conductivity, feature
It is, the proppant pack dynamic slit width are as follows: become according to flowing bottomhole pressure (FBHP) after coal petrography, the mechanical characteristics of proppant and pressure break
Change, establish the computation model for considering that proppant pack slit width changes over time, comprising the following steps:
A, it is tested by three axis rock mechanics parameters, obtains the mechanics parameter of coal petrography rock sample and proppant material, provided for model
Necessary basis parameter；
B, according to mining data after pressure break, flowing bottomhole pressure (FBHP) is calculated, and then seam fluid pressure is calculated, to calculate
To different moments crack wall surface effective stress.
5. a kind of coal bed gas well fracturing fracture according to claim 1 becomes the prediction technique of space-time flow conductivity, feature
It is, the supporting crack active diversion ability are as follows: consider the blocking of coal dust deposition to the shadow of porosity based on classical filtration theory
It rings, establishes the computation model for considering that proppant pack permeability changes over time, comprising the following steps:
I, coal dust sedimentation coefficient is obtained to the arresting efficiency of coal dust and the porosity calculation of proppant pack according to proppant；
II, the supporting crack after coal dust deposition blocking is calculated according to the coal powder density in coal dust sedimentation coefficient and sand packed fracture
Porosity；
III, the fracture permeabgility after coal dust deposition blocking is obtained according to K-C equation.
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