CN108590634A - A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique - Google Patents
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique Download PDFInfo
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Abstract
The present invention relates to a kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction techniques, and steps are as follows：S1, be segmented along pit shaft length, and according to known some fluid flow parameters, estimate subsequent point pressure drop and temperature drop；S2, calculate physical properties of fluids parameter, and pressure drop is calculated according to pressure drop equation and energy conservation equation and temperature drops；S3, whether there is crack and bridge plug according to calculating section, calculate gas-liquid two-phase inbound traffics, the loss of injection interference drop and the bridge plug droop loss for entering pit shaft by crack, and update gas-liquid two-phase flow and pressure drop in pit shaft；S4, by step S2And S3The pressure drop being calculated and temperature drop repeat step S compared with estimated value1~S4Until pressure drop and temperature drop while meeting required precision；S5, repeat step S1~S5Until all segmentations calculating terminates.The present invention considers that pit shaft gas liquid two-phase flow, horizontal wellbore mass variable flow and Reservoir Seepage are coupled with pit shaft multiphase flow, establish the prediction technique of shale gas multistage fracturing horizontal well pit shaft gas liquid two-phase flow rule and inbound traffics, compensate for the technological gap of shale gas multistage fracturing Horizontal Well bottom pressure and the prediction of inbound traffics section, understanding of the field engineer to shale gas well Production development can be improved, shale gas well daily management is reinforced.
Description
Technical field
The present invention relates to shale gas development level well multistage fracturing technical fields, and in particular to a kind of coupling pit shaft multiphase flow
The prediction technique of dynamic shale gas multistage fracturing horizontal well inbound traffics.
Background technology
2016,《Paris climate agreement》It comes into force, quickening has pushed world energy sources consumption structure to make the transition, and is had issued to the whole world
The strong signal of green low-carbon and sustainable development.China " 13 " planning proposes the year two thousand twenty natural gas in energy-consuming
The target of accounting 10%, and China's natural gas is chronically at the situation that supply falls short of demand, under current policies scene, realizes the target
Face larger challenge.The exploitation for accelerating shale gas is the inevitable choice for alleviating China's natural gas imbalance between supply and demand.Shale gas reservoir
Permeability is extremely low, without natural production capacity, needs to carry out extensive hydraulic fracturing volume increase to achieve the purpose that business exploitation, horizontal well
Multistage fracturing technology is the Main Yield-increasing operation means of current shale gas exploitation.
During shale gas exploitation, pressure, temperature and data on flows are monitored to bottom pressure and inbound traffics according to well head
It is the key that understanding and management shale gas well that section, which carries out prediction,.However due to there are following technical barrier, field engineering at present
Teacher mainly rule of thumb predicts.(1) in shale gas production process, due to the row of returning of fracturing fluid, with gas-liquid two in pit shaft
Phase forma fluens exist；(2) during horizontal wellbore gas-liquid two-phase flows to heel end by toe-end, gas-liquid two-phase passes through crack
Pit shaft is constantly flowed into, is variable mass gas liquid two-phase flow in pit shaft；(3) in horizontal wellbore variable mass gas liquid two-phase flow process
In, Multiphase Flow rule in pit shaft can be changed by flowing into the fluid of pit shaft through crack by Reservoir Seepage, and the variation of well cylinder pressure
The inbound traffics of gas-liquid two-phase can be influenced again, this process is the coupling process of Reservoir Seepage and pit shaft gas liquid two-phase flow.Above-mentioned 3 side
Face problem increases the complexity that shale gas multistage fracturing horizontal well pit shaft fluid stream moves rule and inbound traffics prediction, to lead
Field engineer is caused to recognize bottom pressure variation and inbound traffics section during shale gas trends exploitation insufficient, lack has at present
The technological means of effect.
To solve the above-mentioned problems, the present invention considers horizontal wellbore Variable Mass Flow and Reservoir Seepage-pit shaft multiphase flow coupling,
According to gas-liquid two-phase theory, shale gas multistage fracturing horizontal well pit shaft gas liquid two-phase flow model is established, to accurately predict
Bottom pressure and gas-liquid two-phase inbound traffics section, improve the understanding and management level of field engineer.
Invention content
The technical problem to be solved in the present invention is：During solving shale gas exploitation, bottom pressure is pre- with inbound traffics
Survey problem, especially pit shaft gas liquid two-phase flow, horizontal segment variable mass two-phase flow and pit shaft and reservoir coupled problem, this hair
The bright a kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique, this method of providing can realize shale gas exploitation
When bottom pressure and produce liquid and gas-producing profile accurate prediction.
Technical scheme is as follows：
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique, steps are as follows：
It obtains to calculate and needs basic data；
According to basic data, in conjunction with vertical and slanted well bore two-phase flow model, calculated level pit shaft heel end flow parameter；
Reservoir Seepage rule is coupled according to horizontal wellbore Variable Mass Flow movable model based on heel end flow parameter, is solved horizontal
The wellbore pressure regularity of distribution and gas-liquid two-phase inbound traffics.
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique, the model of the present invention include
Vertical bore two-phase flow model, horizontal wellbore variable mass two-phase flow model, two-phase deliverability equation, the two-phase be gas and
Liquid.
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique of the present invention, it is described vertical and incline
Inclined shaft cylinder two-phase flow model includes continuity equation, barometric gradient equation and energy conservation equation；
The vertical and slanted well bore two-phase flow model of the present invention, shown in the continuity equation such as following formula (1),
Wherein, miIndicate that gas-liquid two-phase mass flow, i=1 are gas, i=2 is liquid (units/kg/s), and l is indicated along well
Cylinder depth (unit m)；
The vertical and slanted well bore two-phase flow model of the present invention, shown in the barometric gradient equation such as following formula (2),
Wherein, P indicates that downhole well fluid pressure (unit Pa), l are indicated along mine shaft depth (unit m), ρlIndicate that liquid is close
Spend (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), g indicates acceleration of gravity (unit ms-2), λ indicates flowing
Resistance coefficient, G indicate that the mass flow (units/kg/s) of mixture, v indicate gas-fluid two-phase mixture mean flow rate (unit m/
S), D indicates that (unit m), A indicate that pipeline section accumulates (unit m to internal diameter of the pipeline2), flIndicate liquid holdup, vsgIndicate that shale gas is apparent
Flow velocity (unit m/s)；
The vertical and slanted well bore two-phase flow model of the present invention, shown in the energy conservation equation such as following formula (3),
Wherein, T indicates downhole well fluid temperature (unit K), TeIndicate that environment temperature (unit K), l are indicated along mine shaft depth
(unit m), ρlIndicate fluid density (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), flIndicate liquid holdup, vlTable
Show flow rate of liquid (unit m/s), vgIndicate gas flow rate (unit m/s), CplIndicate liquid specific heat at constant pressure (unit J/ (kg
K)), CpgIndicate liquid specific heat at constant pressure (unit J/ (kgK)), RtIndicate thermal resistance (unit K/W)；
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique of the present invention, the horizontal wellbore
Two-phase Variable Mass Flow movable model includes continuity equation, barometric gradient equation, parasitic pressure drop equation and energy conservation equation；
The horizontal wellbore two-phase Variable Mass Flow movable model of the present invention, shown in the continuity equation such as following formula (4),
Wherein, miIndicate that gas-liquid two-phase mass flow, i=1 are gas, i=2 is liquid (units/kg/s), and l is indicated along well
Cylinder depth (unit m), msiIndicate the gas-liquid two-phase inbound traffics of inflow horizontal wellbore in dl sections, i=1 is gas, and i=2 is liquid
(units/kg/s)；
The horizontal wellbore two-phase Variable Mass Flow movable model of the present invention, shown in the barometric gradient equation such as following formula (5),
Wherein, P indicates that downhole well fluid pressure (unit Pa), l indicate that (unit m), A indicate pipeline section along mine shaft depth
Product (unit m2), m indicates that gas-fluid two-phase mixture mass flow (units/kg/s), ρ indicate gas-fluid two-phase mixture density (unit
kg/m3), flIndicate that liquid holdup, M indicate that shale gas relative molecular weight (units/kg/mol), R indicate gas constant (unit J/
(molK)), T indicates that fluid temperature (F.T.) (unit K), τ indicate the shear stress (unit N/m) between gas-liquid two-phase and tube wall, D tables
Show that (unit m), v indicate gas-fluid two-phase mixture mean flow rate (unit m/s), C to internal diameter of the pipeline0Indicate constant, βTIndicate that liquid is swollen
Swollen coefficient (unit 1/K)；
Wherein, (6) calculate the shear stress between gas-liquid two-phase and tube wall according to the following formula,
Wherein, f indicates that the coefficient of friction resistance, v indicate the flow velocity (unit m/s) of gas-fluid two-phase mixture；
Wherein, coefficient of friction resistance f is calculated according to Beggs-Brill methods.
The horizontal wellbore two-phase Variable Mass Flow movable model of the present invention, the parasitic pressure drop equation includes bridge plug droop loss side
Journey and injection interference drop loss equation,
The parasitic pressure drop equation of the present invention, shown in the bridge plug droop loss equation such as following formula (7),
Wherein, Δ PJIndicate bridge plug choke pressure drop loss (unit Pa), ζcIndicate restriction loss coefficient, CcIt indicates to shrink system
Number, A indicate that pipeline section accumulates (unit m2), AcIndicate bridge plug sectional area (unit m2), ρ indicates that gas-fluid two-phase mixture density is (single
Position kg/m3), v indicates the flow velocity (unit m/s) of gas-fluid two-phase mixture；
The parasitic pressure drop equation of the present invention, the injection interference drop loss equation enter shown in following formula (8),
Wherein, Δ PmIndicate injection interference drop loss (unit Pa), fTIndicate that injection interference drag coefficient, D indicate pipeline
(unit m), ρ indicate gas-fluid two-phase mixture density (units/kg/m to internal diameter3), v indicates the flow velocity (unit of gas-fluid two-phase mixture
M/s), dl indicates fracture interval (unit m)；
Wherein, injection interference drag coefficient fT(9) calculate according to the following formula,
Wherein, fTIndicate that injection interference drag coefficient, D indicate that (unit m), dl indicate fracture interval (unit to internal diameter of the pipeline
M), Re indicates fluid Reynolds number, qinIndicate that the mass flow (units/kg/s) for entering horizontal wellbore from crack, Q indicate horizontal well
Cylinder mainstream fluid mass flow (units/kg/s)；
Wherein, (10) calculate fluid Reynolds number according to the following formula,
Wherein, D indicates that (unit m), v indicate the flow velocity (unit m/s) of gas-fluid two-phase mixture, ρ to internal diameter of the pipelinelIndicate liquid
Volume density (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), flIndicate liquid holdup, μlIndicate hydrodynamic viscosity
(unit Pas), μgIndicate aerodynamic force viscosity (unit Pas)；
The horizontal wellbore two-phase Variable Mass Flow movable model of the present invention, shown in the energy conservation equation such as formula (3).
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique of the present invention, the two-phase production capacity
Equation includes liquid phase deliverability equation and gas phase deliverability equation；
The two-phase deliverability equation of the present invention, shown in the liquid phase deliverability equation such as following formula (11),
Wherein, PeiIndicate reservoir pressure (unit Pa), PwfiIndicate the corresponding flowing bottomhole pressure (FBHP) (unit Pa) in i-th of crack,
qfiIt indicates to flow into liquid volume flow (the unit m in pit shaft through i-th of crack3/ s), μlIndicate hydrodynamic viscosity (unit
Pas), B indicates that the volume factor of liquid, K indicate the permeability (unit 10 of reservoir rock-3μm2), KfIndicate the infiltration in crack
Rate (unit 10-3μm2), h indicates reservoir thickness (unit m), aiIndicate fracture interval (unit m), b the expression storage in i-th of crack
Slice width degree (unit m), LfIndicate that (unit m), w indicate fracture width (unit m), r to fracture lengthwIndicate wellbore radius (unit
M), s indicates skin factor.
The two-phase deliverability equation of the present invention, shown in the gas phase deliverability equation such as following formula (12),
Wherein, PeiIndicate reservoir pressure (unit kPa), PwfiIndicate the corresponding flowing bottomhole pressure (FBHP) (unit kPa) in i-th of crack,
qgiIt indicates to flow into volumetric flow of gas (the unit m in pit shaft through i-th of crack3/ s), A and B indicate coefficient distribution according to the following formula
(13) it is calculated with (14),
Wherein, μgIndicate that aerodynamic force viscosity (unit mPas), Z indicate that the compressed coefficient of gas, T indicate gas temperature
(unit K), K indicate the permeability (unit μm of reservoir rock2), KfIndicate the permeability (unit μm in crack2), h indicates that reservoir is thick
Spend (unit m), aiIndicate fracture interval (unit m), b expression reservoir width (the unit m), L in i-th of crackfIndicate fracture length
(unit m), w indicate fracture width (unit m), rwIndicate that (unit m), s indicate that skin factor, β indicate turbulent flow speed to wellbore radius
Spend coefficient (unit m-1), γgIndicate the relative density of gas.
Wherein, (15) calculate turbulent velocity factor beta according to the following formula,
Wherein, K indicates the permeability (unit μm of reservoir rock2)。
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique of the present invention, the Model coupling
Solution procedure is specially：
S1, known some mass flow mi, pressure PiWith temperature Ti, estimation calculates section pressure drop Δ P and Δ T drops in temperature,
And according to calculating section average pressure and temperature computation physical properties of fluids parameter；
S2, judge calculate section whether be located at horizontal segment, if so, according to following steps calculate pressure drop Δ P ', if it is not, then
Pressure drop Δ P ' is calculated according to formula (2)；
S21, according to formula (5) calculate pressure drop, judge calculate section whether there is crack, if so, according to formula (10) and (11)
Calculate the liquid measure q for entering pit shaft by crackfiWith tolerance qgi, and injection interference drop loss Δ P is calculated according to formula (8)m, and Δ P '
=Δ P '+Δ Pm, walked if it is not, then entering next calculating；
S22, judge that calculating section whether there is bridge plug, if so, calculating bridge plug droop loss Δ P according to formula (7)J, and Δ P '
=Δ P '+Δ PJ, walked if it is not, then entering next calculating；
S3, temperature drop Δ T ' is calculated according to energy equation；
S4If, ︱ Δ P- Δ P ' ︱≤ε, next calculating step；
If ︱ Δ P- Δ P ' ︱ ＞ ε, Δ P=(Δ P+ Δs P ')/2 is updated, repeats step S2~S4, until ︱ Δ P- Δs
Until P ' ︱≤ε；
S5If, ︱ Δ T- Δ T ' ︱≤ε, next calculating step；
If ︱ Δ T- Δ T ' ︱ ＞ ε, Δ T=(Δ T+ Δs T ')/2 is updated, repeats step S2~S5, until ︱ Δ T- Δs
Until T ' ︱≤ε；
S6, calculate subsequent point flow mi+1, pressure Pi+1With temperature Ti+1, judge whether to calculate and arrive toe-end, if so, calculating
Terminate, export result of calculation, if not, repeating step S1~S6。
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique of the present invention, the basic data
Including：
Shale gas well attribute：Cement thickness, casing size, tubing size, bridge plug size, eye diameter, kickoff point (KOP) enter
Target spot is tiltedly deep, enters target spot vertical depth, and it is tiltedly deep to go out target spot, goes out target spot vertical depth, displacement, deep under oil pipe；
Reservoir attribute：Reservoir pressure, reservoir temperature, reservoir width, reservoir thickness, matrix permeability；
Crack attribute：Fracture length, fracture width, fracture height, fracture permeabgility；
Multistage fracturing perforating scheme：Series is segmented bottom circle, segmentation top circle, segment length, perforation bottom circle, perforation top circle, perforation
Number, cluster spacing, bridge plug position；
Fluid properties：The viscous warm data of liquid, aerodynamic force viscosity, gas relative density, fluid density；
Primary condition：Well head pressure, wellhead temperature, Liquid output, gas production.
Beneficial effects of the present invention：
1, shale gas multistage fracturing horizontal well inbound traffics prediction technique proposed by the present invention is highly practical, simple easily to realize,
It disclosure satisfy that shale gas exploitation prediction of the scene to horizontal wellbore two-phase flow rule and inbound traffics section in the process.
2, shale gas multistage fracturing horizontal well inbound traffics prediction technique proposed by the present invention considers vertical, inclination and level
Pit shaft gas liquid two-phase flow, the coupling of horizontal wellbore mass variable flow and Reservoir Seepage and wellbore tubular stream, to what is made
Prediction result is more coincide with shale gas multistage fracturing horizontal well actual conditions.
Description of the drawings
Fig. 1 is shale gas output process fluid flow schematic diagram in the embodiment of the present invention.
Fig. 2 is shale gas multistage fracturing horizontal well pit shaft Multiphase Flow, inbound traffics couple solution stream in the embodiment of the present invention
Cheng Tu.
Fig. 3 is wellbore pressure distribution curve in the embodiment of the present invention.
Fig. 4 is well bore temperature distribution curve in the embodiment of the present invention.
Fig. 5 is pit shaft horizontal segment shale gas inbound traffics sectional view in the embodiment of the present invention.
Fig. 6 is pit shaft horizontal segment liquid inlet stream amount sectional view in the embodiment of the present invention.
Specific implementation mode
Below by specific embodiment and in conjunction with attached drawing, the invention will be further described, but not limited to this.
A kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique, iterative calculation flow chart such as Fig. 1
Shown, steps are as follows for specific calculating：
S1, Fig. 2 be shale gas output process fluid flow schematic diagram, it is known that primary condition：Well head pressure, temperature and gas-liquid
Two phase flow is segmented along pit shaft according to length, and ensures that calculating section step-length is less than 20 meters, to improve computational accuracy；
S2, first according to upper pressure and temperature, estimate the pressure drop Δ P and temperature drop Δ T of the calculating section；Then
The average pressure and temperature that Δ T calculates this section drop according to the pressure drop Δ P and temperature of estimation, and according to average pressure and thermometer
Calculate the physical parameter of this section of fluid；
S3, judge to calculate whether section is located at horizontal segment, if so, calculated along journey fluid pressure drop Δ P ' according to formula (5),
If it is not, then being calculated along journey fluid pressure drop Δ P ' according to formula (2)；
S4, judge that calculating section whether there is crack, if so, by crack entering pit shaft according to formula (10) and (11) calculating
Gas and liquid inlet stream amount, and calculate injection pressure according to the gas-liquid two-phase flow of result of calculation update subsequent point, and according to formula (8)
Drop loss Δ Pm, and update and calculate section pressure drop：Δ P '=Δ P '+Δ Pm, if it is not, then entering S5；
S5, judge that calculating section whether there is bridge plug, if so, calculating bridge plug droop loss Δ P according to formula (7)J, and update
Calculate section pressure drop：Δ P '=Δ P '+Δ PJ, if it is not, then entering S6；
S6, temperature drop Δ T ' is calculated according to energy equation (3)；
S7, judge estimated pressure drop with temperature drop it is whether accurate,
If ︱ Δ P- Δ P ' ︱≤ε, and ︱ Δ T- Δ T ' ︱≤ε, then enter S8；
If ︱ Δ P- Δ P ' ︱ ＞ ε, update Δ P=(Δ P+ Δs P ')/2；If ︱ Δ T- Δ T ' ︱ ＞ ε, update Δ T
=(Δ T+ Δs T ')/2 repeats step S2~S7, until ︱ Δ P- Δ P ' ︱≤ε and ︱ Δ T- Δ T ' ︱≤ε；Step S7In, ε
Indicate required precision, ε=10 in the present embodiment-3；
S8, repeat the above steps S1~S7, until all segmentations have been calculated.
Fig. 3 and Fig. 4 is respectively shale gas multistage fracturing horizontal well cylinder pressure and temperature distribution history, mark position in figure
Respectively kickoff point (KOP) and heel end.Barometric gradient is mainly by gas-liquid two-phase fluid from reassembling into vertical bore, as depth increases,
Pressure approximation linearly increases, and after reaching kickoff point (KOP), pressure increases trend and slows down；And in horizontal segment, friction drag and part
Restriction loss is the main composition of barometric gradient, but some effects are smaller, to make horizontal segment pressure keep constant substantially.Well
Fluid temperature (F.T.) obeys changing rule identical with pressure substantially in cylinder, and leads to temperature due to the presence of thermostat layer in adjacent ground surface
Degree deviates linear variability law.
Fig. 5 and Fig. 6 is respectively horizontal wellbore shale gas and fluid inflow amount sectional view, and gas-liquid two-phase obeys identical become a mandarin
Rule, since toe-end downhole well fluid pressure is higher, gas-liquid two-phase inbound traffics are relatively low, and are kept substantially in longer horizontal segment
Constant, with being changed from toe-end to heel end, downhole well fluid pressure reduction, producing pressure differential increases, and inbound traffics are consequently increased, and
Near heel end, producing pressure differential is maximum, so as to cause gas-liquid two-phase inbound traffics highest.
The technology contents that the present invention does not elaborate belong to the known technology of those skilled in the art.
Although being illustrated and described to the preferred embodiment of the present invention, it will be apparent to those skilled in the art that of the invention
It is not limited to the range of preferred embodiment, for those skilled in the art, as long as various change is appended
In the spirit and scope of the present invention that claim is limited and determined, these variations are it will be apparent that all utilize the present invention
The innovation and creation of design are in the row of protection.
Claims (6)
1. a kind of shale gas multistage fracturing horizontal well wellbore pressure and inbound traffics prediction technique, steps are as follows：
S1, be segmented along pit shaft, according to upper pressure and temperature, estimate the pressure drop Δ P and temperature drop Δ of the calculating section
T, and according to the physical parameter of this section of fluid of average pressure and temperature computation；
S2, judge calculate section whether be located at horizontal segment, if so, according to formula (1) calculate along journey fluid pressure drop Δ P ', if it is not, then
It is calculated along journey fluid pressure drop Δ P ' according to formula (2)；
In formula (1)~(2), P indicates that downhole well fluid pressure (unit Pa), l indicate that (unit m), A indicate pipe along mine shaft depth
Road sectional area (unit m2), m indicates that gas-fluid two-phase mixture mass flow (units/kg/s), ρ indicate that gas-fluid two-phase mixture is close
Spend (units/kg/m3), ρlIndicate fluid density (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), flLiquid is held in expression
Rate, M indicate that shale gas relative molecular weight (units/kg/mol), R indicate that gas constant (unit J/ (molK)), T indicate fluid
Temperature (unit K), τ indicate that the shear stress (unit N/m) between gas-liquid two-phase and tube wall, D indicate internal diameter of the pipeline (unit m), v
Indicate gas-fluid two-phase mixture mean flow rate (unit m/s), vsgIndicate shale gas apparent velocity (unit m/s), C0Indicate constant,
βTIndicate that the liquid coefficient of expansion (unit 1/K), g indicate acceleration of gravity (unit ms-2), λ indicates flow resistance coefficient, G tables
Show the mass flow (units/kg/s) of mixture；
S3, judge calculate section whether there is crack, if it is not, then entering step S4, if so, being calculated according to formula (3) and (4) by splitting
Gas and liquid inlet stream amount of the seam into pit shaft；
Wherein, A and B is coefficient, and (5) and (6) calculate according to the following formula,
Wherein, β is turbulent velocity coefficient, and (7) calculate according to the following formula,
In formula (3)~(7), PeiIndicate reservoir pressure (unit Pa), PwfiIndicate the corresponding flowing bottomhole pressure (FBHP) (unit in i-th of crack
Pa), qfiIt indicates to flow into liquid volume flow (the unit m in pit shaft through i-th of crack3/ s), qgiIt indicates to flow into through i-th of crack
Volumetric flow of gas (unit m in pit shaft3/ s), μlIndicate hydrodynamic viscosity (unit Pas), μgIndicate that aerodynamic force is viscous
It spends (unit mPas), B indicates that the volume factor of liquid, K indicate the permeability (unit 10 of reservoir rock-3μm2), KfExpression is split
Permeability (the unit 10 of seam-3μm2), h indicates reservoir thickness (unit m), aiIndicate i-th of crack fracture interval (unit m),
B indicates reservoir width (unit m), LfIndicate that (unit m), w indicate fracture width (unit m), r to fracture lengthwIndicate wellbore radius
(unit m), s indicate that skin factor, Z indicate that the compressed coefficient of gas, T indicate gas temperature (unit K), γgIndicate gas
Relative density；
Subsequent point gas-liquid two-phase flow is updated according to gas-liquid two-phase inbound traffics,
Qfi+1=Qfi+1-qfi (8)
Qgi+1=Qgi+1-qgi (9)
Injection pressure drop loss Δ P is calculated according to formula (10)m, and update and calculate section pressure drop：Δ P '=Δ P '+Δ Pm,
Wherein, fTTo inject interference drag coefficient, (11) calculate according to the following formula,
Then (12) calculate fluid reynolds number Re according to the following formula,
In formula (10)~(12), Δ PmIndicate injection interference drop loss (unit Pa), fTIndicate injection interference drag coefficient, D
Indicate that (unit m), ρ indicate gas-fluid two-phase mixture density (units/kg/m to internal diameter of the pipeline3), v indicates gas-fluid two-phase mixture
Flow velocity (unit m/s), dl indicate that (unit m), Re indicate fluid Reynolds number, q to fracture intervalinIt indicates to enter horizontal wellbore from crack
Mass flow (units/kg/s), Q indicates that horizontal wellbore mainstream fluid mass flow (units/kg/s), v indicate that gas-liquid two-phase is mixed
Close the flow velocity (unit m/s) of object, ρlIndicate fluid density (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), flTable
Show liquid holdup, μlIndicate hydrodynamic viscosity (unit Pas), μgIndicate aerodynamic force viscosity (unit Pas)；
S4, judge calculate section whether there is bridge plug, if it is not, then entering step S5, if so, calculating bridge plug pressure drop according to formula (13)
Lose Δ PJ, and update and calculate section pressure drop：Δ P '=Δ P '+Δ PJ；
Wherein, Δ PJIndicate bridge plug choke pressure drop loss (unit Pa), ζcIndicate restriction loss coefficient, CcIndicate constriction coefficient, A
Indicate that pipeline section accumulates (unit m2), AcIndicate bridge plug sectional area (unit m2), ρ indicates gas-fluid two-phase mixture density (unit
kg/m3), v indicates the flow velocity (unit m/s) of gas-fluid two-phase mixture；
S5, temperature drop Δ T ' is calculated according to energy equation (14)；
Wherein, T indicates downhole well fluid temperature (unit K), TeIndicate that environment temperature (unit K), l are indicated along mine shaft depth (unit
M), ρlIndicate fluid density (units/kg/m3), ρgIndicate shale air tightness (units/kg/m3), flIndicate liquid holdup, vlIndicate liquid
Body flow velocity (unit m/s), vgIndicate gas flow rate (unit m/s), CplIndicate liquid specific heat at constant pressure (unit J/ (kgK)),
CpgIndicate liquid specific heat at constant pressure (unit J/ (kgK)), RtIndicate thermal resistance (unit K/W)；
S6, judge estimated pressure drop with temperature drop it is whether accurate,
If ︱ Δ P- Δ P ' ︱≤ε and ︱ Δ T- Δ T ' ︱≤ε, enter step S7；
If ︱ Δ P- Δ P ' ︱ ＞ ε, Δ P=(Δ P+ Δs P ')/2, ︱ Δ T- Δ T ' ︱ ＞ ε are updated, then update Δ T=(Δ T+
Δ T ')/2, repeat step S2~S6, until ︱ Δ P- Δ P ' ︱≤ε and ︱ Δ T- Δ T ' ︱≤ε, step S6In, ε indicates precision
It is required that；
S7, repeat the above steps S1~S6, until all segmentations have been calculated.
2. the shale gas multistage fracturing horizontal well inbound traffics prediction side of coupling pit shaft Multiphase Flow according to claim 1
Method, which is characterized in that step S1In, section length step-length should be less than 20 meters.
3. the shale gas multistage fracturing horizontal well inbound traffics prediction side of coupling pit shaft Multiphase Flow according to claim 1
Method, which is characterized in that step S1In, pressure drop and the temperature drop of estimation should be reasonable, flowed as pressure drop can be estimated as calculating in section
The product that can be estimated as length step-length and geothermal gradient drops in the pressure difference that weight power is formed, temperature.
4. the shale gas multistage fracturing horizontal well inbound traffics prediction side of coupling pit shaft Multiphase Flow according to claim 1
Method, which is characterized in that step S2In, density, flow velocity and the mass flow of gas-fluid two-phase mixture are utilized all in accordance with liquid holdup to be added
The mode of weight average calculates.
5. the shale gas multistage fracturing horizontal well inbound traffics prediction side of coupling pit shaft Multiphase Flow according to claim 1
Method, which is characterized in that step S3In, it is assumed that crack longitudinally passes completely through reservoir, i.e. fracture height is equal to reservoir thickness.
6. the shale gas multistage fracturing horizontal well inbound traffics prediction side of coupling pit shaft Multiphase Flow according to claim 1
Method, which is characterized in that step S3In, thermal resistance should be calculated according to casing programme actual conditions.
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