CN108868730B - Supercritical carbon dioxide jet fracturing phase state control method and device and electronic equipment - Google Patents
Supercritical carbon dioxide jet fracturing phase state control method and device and electronic equipment Download PDFInfo
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- E—FIXED CONSTRUCTIONS
- E21—EARTH DRILLING; MINING
- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/25—Methods for stimulating production
- E21B43/26—Methods for stimulating production by forming crevices or fractures
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- E—FIXED CONSTRUCTIONS
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- E21B—EARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/164—Injecting CO2 or carbonated water
Abstract
The invention provides a supercritical carbon dioxide jet fracturing phase state control method, a supercritical carbon dioxide jet fracturing phase state control device and electronic equipment, wherein the method comprises the steps of obtaining stratum parameters, well completion parameters and construction parameters; establishing a physical property parameter calculation model of the carbon dioxide; building a wellbore pressure calculation model of carbon dioxide; building a wellbore temperature calculation model of carbon dioxide; and calculating the temperature and pressure of the carbon dioxide at the injection point under different construction parameters by combining a physical property parameter calculation model, a shaft pressure calculation model and a shaft temperature calculation model based on the stratum parameters, the completion parameters and the construction parameters so as to optimize the construction parameters. According to the method, through comprehensive application of heat transfer science and hydromechanics, a corresponding pressure and temperature calculation model is established by considering the heat exchange phenomenon of the carbon dioxide sprayed by the nozzle and the annular carbon dioxide when the carbon dioxide is mixed at the spraying point, so that the calculation accuracy is improved, and the construction parameters are optimized more accurately.
Description
Technical Field
The invention relates to the technical field of yield increase transformation of oil and gas fields, in particular to a supercritical carbon dioxide jet fracturing phase state control method, a supercritical carbon dioxide jet fracturing phase state control device and electronic equipment.
Background
At present, large-scale hydraulic fracturing is a key technology for exploiting unconventional oil and gas resources such as shale gas and compact sandstone gas, but the shale gas is mainly distributed in hills and mountainous areas with deficient water resources and relatively inconvenient traffic such as Sichuan and the like for iteration, and frequent and multi-well large-scale fracturing is difficult to develop. There is therefore a need to make a breakthrough in either waterless or low-water fracturing methods. Supercritical carbon dioxide jet fracturing, one type of anhydrous fracturing, has received much attention because it has many unique advantages. The key of supercritical carbon dioxide jet fracturing is to accurately predict the temperature and pressure of carbon dioxide at an injection point, so that the carbon dioxide is in a supercritical state through artificial regulation.
The wellbore fluid flow and heat transfer process during supercritical carbon dioxide jet fracturing can be described as: (1) injecting carbon dioxide from the annulus and the coiled tubing simultaneously, wherein the carbon dioxide is continuously heated by the stratum in the process that the carbon dioxide flows from the wellhead to the bottom of the well; (2) the carbon dioxide in the continuous oil pipe is sprayed out from the nozzle at the spraying point and then mixed with the carbon dioxide injected into the annulus, and the carbon dioxide is sprayed out from the nozzle and then subjected to large temperature drop, so that heat exchange is generated in the mixing process of the low-temperature carbon dioxide sprayed out from the nozzle and the high-temperature carbon dioxide in the annulus; (3) the mixed carbon dioxide flows into the formation at a high velocity.
At present, few reports about supercritical carbon dioxide jet fracturing wellbore temperature and pressure calculation methods are reported, influence consideration in multiple aspects is not sufficient, and calculation accuracy is low.
Disclosure of Invention
In view of the above, the present invention provides a method, an apparatus, and an electronic device for controlling a supercritical carbon dioxide jet fracturing phase state, so as to establish a corresponding pressure and temperature calculation model by comprehensively applying heat transfer science and hydromechanics, considering a heat exchange phenomenon when carbon dioxide jetted from a nozzle is mixed with annular carbon dioxide at a jetting point, and improve calculation accuracy, thereby more accurately optimizing construction parameters.
In a first aspect, an embodiment of the present invention provides a supercritical carbon dioxide jet fracturing phase state control method, including:
acquiring stratum parameters, well completion parameters and construction parameters;
establishing a physical property parameter calculation model of the carbon dioxide;
establishing a wellbore pressure calculation model of carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through a nozzle;
establishing a shaft temperature calculation model of carbon dioxide, wherein the shaft pressure calculation model comprises a shaft internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through a nozzle and a temperature mixing equation;
and calculating the temperature and pressure of the carbon dioxide at the injection point under different construction parameters based on the formation parameters, the completion parameters and the construction parameters by combining the physical property parameter calculation model, the wellbore pressure calculation model and the wellbore temperature calculation model so as to optimize the construction parameters.
In a second aspect, an embodiment of the present invention further provides a supercritical carbon dioxide jet fracturing phase state control apparatus, including:
the parameter acquisition module is used for acquiring stratum parameters, well completion parameters and construction parameters;
the physical property model establishing module is used for establishing a physical property parameter calculation model of the carbon dioxide;
the pressure model building module is used for building a shaft pressure calculation model of the carbon dioxide, and the shaft pressure calculation model comprises a shaft pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through the nozzle;
the calculation model establishing module is used for establishing a shaft temperature calculation model of the carbon dioxide, and the shaft pressure calculation model comprises a shaft internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through the nozzle and a temperature mixing equation;
and the parameter optimization module is used for calculating the temperature and the pressure of the carbon dioxide at the injection point under different construction parameters by combining the physical property parameter calculation model, the shaft pressure calculation model and the shaft temperature calculation model based on the stratum parameters, the completion parameters and the construction parameters so as to optimize the construction parameters.
In a third aspect, an embodiment of the present invention further provides an electronic device, including a memory and a processor, where the memory stores a computer program operable on the processor, and the processor executes the computer program to implement the method according to the first aspect.
The embodiment of the invention has the following beneficial effects:
the method provided by the embodiment of the invention comprises the steps of obtaining stratum parameters, completion parameters and construction parameters; establishing a physical property parameter calculation model of the carbon dioxide; building a wellbore pressure calculation model of the carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through a nozzle; establishing a shaft temperature calculation model of carbon dioxide, wherein the shaft pressure calculation model comprises a shaft internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through a nozzle and a temperature mixing equation; and calculating the temperature and pressure of the carbon dioxide at the injection point under different construction parameters by combining a physical property parameter calculation model, a shaft pressure calculation model and a shaft temperature calculation model based on the stratum parameters, the completion parameters and the construction parameters so as to optimize the construction parameters. According to the method, through comprehensive application of heat transfer science and hydromechanics, a corresponding pressure and temperature calculation model is established by considering the heat exchange phenomenon of the carbon dioxide sprayed by the nozzle and the annular carbon dioxide when the carbon dioxide is mixed at the spraying point, so that the calculation accuracy is improved, and the construction parameters are optimized more accurately.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
Fig. 1 is a schematic flow chart of a supercritical carbon dioxide jet fracturing phase control method according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of another method for controlling the phase state of supercritical carbon dioxide jet fracturing provided in an embodiment of the present invention;
FIG. 3 is a schematic diagram of supercritical carbon dioxide jet fracturing wellbore flow and heat transfer provided by an embodiment of the present invention;
FIG. 4 is a wellbore temperature profile at different coiled tubing injection rates;
FIG. 5 is a wellbore pressure profile at different coiled tubing injection rates;
fig. 6 is a schematic structural diagram of a supercritical carbon dioxide jet fracturing phase state control device according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
At present, reports about methods for calculating the temperature and the pressure of a supercritical carbon dioxide jet fracturing well bore are few, influence in multiple aspects is not considered sufficiently, and calculation accuracy is low.
For the understanding of the present embodiment, a detailed description will be given to a supercritical carbon dioxide jet fracturing phase control method disclosed in the present embodiment.
The first embodiment is as follows:
fig. 1 illustrates a supercritical carbon dioxide jet fracturing phase control method provided by an embodiment of the present invention, including:
and S101, acquiring stratum parameters, completion parameters and construction parameters.
In a possible embodiment, the formation parameters include geothermal gradient, rock thermal conductivity, rock specific heat capacity; the well completion parameters comprise well depth, casing size, coiled tubing size, cement sheath size, well bore size, casing thermal conductivity, casing specific heat capacity, coiled tubing thermal conductivity, coiled tubing specific heat capacity, cement sheath thermal conductivity, and cement sheath specific heat capacity; the construction parameters include nozzle diameter, injection speed, injection temperature and injection time.
And step S102, establishing a physical parameter calculation model of the carbon dioxide.
And step S103, establishing a wellbore pressure calculation model of the carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through the nozzle.
And step S104, establishing a wellbore temperature calculation model of the carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through the nozzle and a temperature mixing equation.
And S105, calculating the temperature and pressure of the carbon dioxide at the injection point under different construction parameters by combining a physical property parameter calculation model, a shaft pressure calculation model and a shaft temperature calculation model based on the stratum parameters, the well completion parameters and the construction parameters so as to optimize the construction parameters.
In a possible embodiment, the temperature and the pressure under different construction parameters are compared and analyzed, and the construction parameters meeting the pressure requirement and the temperature requirement are selected as the optimized construction parameters.
According to the mode, through comprehensive application of heat transfer science and hydromechanics, a corresponding pressure and temperature calculation model is established by considering the heat exchange phenomenon when the carbon dioxide sprayed from the nozzle is mixed with the annular carbon dioxide at the spraying point, and the calculation accuracy is improved, so that the construction parameters are more accurately optimized, and the supercritical state of the carbon dioxide is effectively regulated and controlled.
Example two:
fig. 2 illustrates another supercritical carbon dioxide jet fracturing phase control method provided by an embodiment of the present invention, which includes:
step S201, stratum parameters, well completion parameters and construction parameters are obtained.
In a possible embodiment, the formation parameters include geothermal gradient, rock thermal conductivity, rock specific heat capacity; the well completion parameters comprise well depth, casing size, coiled tubing size, cement sheath size, well bore size, casing thermal conductivity, casing specific heat capacity, coiled tubing thermal conductivity, coiled tubing specific heat capacity, cement sheath thermal conductivity, and cement sheath specific heat capacity; the construction parameters include nozzle diameter, injection speed, injection temperature and injection time.
Step S202, establishing a physical property parameter calculation model of the carbon dioxide.
In a possible embodiment, the physical property parameters include carbon dioxide density and specific heat capacity of carbon dioxide, which facilitates calculation of pressure and specific heat capacity of carbon dioxide in different cases in subsequent steps. The physical property parameter calculation model includes:
carbon dioxide density calculation formula
The specific heat capacity of carbon dioxide is calculated as
Wherein:
wherein T is the temperature of carbon dioxide and has a unit of K; p is the pressure of carbon dioxide in Pa; rho is the density of carbon dioxide in kg/m3(ii) a Delta is contrast density, no dimension; tau is inverse contrast temperature without dimension; rhocIs the critical density in kg/m3；TcIs the critical temperature in kg/m3；cpThe specific heat capacity at constant pressure is expressed in J/(kg.K); c. CvThe specific heat capacity is the constant volume, and the unit is J/(kg.K); rc0.1889kJ/(kg K) as gas constant; phi is aoThe free energy is an ideal part of Helmholtz free energy, and has no dimension; phi is arThe residual Helmholtz free energy is dimensionless;
are all constants determined experimentally.
Step S203, a wellbore pressure calculation model of the carbon dioxide is established, and the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through the nozzle.
Specifically, the wellbore internal pressure calculation equation includes a calculation equation of carbon dioxide pressure in a continuous oil pipe in the wellbore and a calculation equation of carbon dioxide pressure in an annular space in the wellbore.
And (3) calculating the pressure of carbon dioxide in the coiled tubing in the shaft by the following equation:
and (3) calculating the pressure of the carbon dioxide in the annulus in the shaft by the equation:
wherein
Wherein z is the longitudinal depth of the wellbore in m (meters); g is the acceleration of gravity in m/s2；rtiThe inner diameter of the coiled tubing is m; r istoThe unit is the outer diameter of the coiled tubing and is m; r isciIs the inner diameter of the sleeve, and the unit is m; p is a radical oftThe pressure of carbon dioxide in the continuous oil pipe is expressed in Pa; p is a radical ofaThe pressure of the carbon dioxide in the annulus is expressed in Pa; rhotIs the density of carbon dioxide in the coiled tubing and has the unit of kg/m3；ρaIs the density of carbon dioxide in the annulus in kg/m3；vtThe flow rate of carbon dioxide in the coiled tubing is expressed in m/s; v. ofaThe flow rate of the carbon dioxide in the annulus is expressed in m/s; re is Reynolds number, and has no dimension; deltatThe roughness of the continuous oil pipe is expressed in m; deltaaThe roughness of the sleeve is expressed in m.
Specifically, when carbon dioxide flows through the nozzle, a pressure drop occurs, and in order to calculate the pressure after carbon dioxide is ejected from the nozzle, the following implicit equation, that is, a pressure calculation equation after carbon dioxide flows through the nozzle, needs to be solved:
wherein
Wherein m istThe unit is kg/s, and the injection speed of carbon dioxide in the coiled tubing is shown as the unit; a is the cross-sectional area of the nozzle in m2；pupIs the carbon dioxide pressure upstream of the nozzle in Pa; p is a radical ofdownThe pressure of the carbon dioxide at the downstream of the nozzle, namely the pressure of the carbon dioxide after flowing through the nozzle, is expressed by Pa; rhoupThe density of carbon dioxide upstream of the nozzle is given in kg/m3；ρdownIs the density of carbon dioxide downstream of the nozzle, i.e. after the carbon dioxide has passed through the nozzle, in kg/m3(ii) a k is carbon dioxide isentropic index.
And step S204, establishing a wellbore temperature calculation model of the carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through the nozzle and a temperature mixing equation.
Specifically, the calculation equation of the temperature in the wellbore comprises a calculation equation of the temperature of carbon dioxide in a continuous oil pipe in the wellbore and a calculation equation of the temperature of carbon dioxide in an annular space in the wellbore.
(a) Equation for calculating temperature of carbon dioxide in continuous oil pipe
Specifically, referring to FIG. 3, carbon dioxide CO in microelements in a continuous oil tube2The heat source of (2) comprises four parts: heat Q flowing into upper part of micro elementt(z); heat of flow out of the lower part of the infinitesimal element, Qt(z + dz); heat Q flowing from annulus into coiled tubingta；CO2Heat Q generated by friction with tube walltf. From this, the energy conservation equation in the coiled tubing can be derived:
Qt(z)-Qt(z+dz)+Qta+Qtf＝0 (13)
wherein
Qt(z)＝mtCtpTt(z) (14)
Qt(z+dz)＝mtCtpTt(z+dz) (15)
Qta＝2πrtiUt(Ta-Tt)dz (16)
Qtf＝Δptfqtdz (17)
Wherein
Substituting equations (14) - (17) into equation (13) can obtain the calculation equation of the carbon dioxide temperature in the coiled tubing:
wherein, TtThe temperature of carbon dioxide in the coiled tubing is represented by K; t isaThe temperature of the carbon dioxide in the annulus is expressed in K; r istiThe inner diameter of the coiled tubing is m; r istoThe unit is the outer diameter of the coiled tubing and is m; ctpThe specific heat capacity of carbon dioxide in the continuous oil pipe is expressed in J/(kg.K); u shapetIs the total heat conductivity coefficient of the coiled tubing and has the unit of W/(m)2.K)；ΔptfThe unit is Pa/m of the friction pressure drop in the continuous oil pipe; q. q.stIs the volume flow rate of carbon dioxide in the coiled tubing, and the unit is m3/s；λtIs the heat conductivity coefficient of the continuous oil pipe and has the unit of W/(m)2.K)；htiIs the convection heat transfer coefficient of the inner surface of the continuous oil pipe, and has the unit of W/(m)2.K)；htoIs the convection heat transfer coefficient of the outer surface of the continuous oil pipe, and the unit is W/(m)2.K)。
The temperature calculation equation after the carbon dioxide flows through the nozzle is as follows:
wherein p isupIs the carbon dioxide pressure upstream of the nozzle in Pa; p is pdownThe pressure of the carbon dioxide at the downstream of the nozzle, namely the pressure of the carbon dioxide after flowing through the nozzle, is expressed by Pa; k is carbon dioxide isentropic index without dimension；TupIs the carbon dioxide temperature upstream of the nozzle in K; t isdownIs the temperature of the carbon dioxide downstream of the nozzle, i.e. after the carbon dioxide has flowed through the nozzle, and is given in K.
(b) Equation for calculating temperature of carbon dioxide in annular space
As can be seen from FIG. 3, the micro-elements in the annulus contain CO2The heat source comprises five parts: heat Q flowing into upper part of micro elementa(z); heat Q flowing out of the lower part of the elementa(z + dz); heat Q flowing out to coiled tubingta；CO2Heat Q generated by friction with tube wallaf(ii) a Heat Q from the formation flowing into the annulusF. From this, the energy conservation equation in the annulus can be derived:
Qa(z)-Qa(z+dz)-Qta+Qaf+QF＝0 (21)
wherein
Qa(z)＝maCapTa(z) (22)
Qa(z+dz)＝maCapTa(z+dz) (23)
Qaf＝Δpafqadz (24)
Substituting equations (22) - (25) into equation (21) can obtain the calculation equation of the temperature of the carbon dioxide in the annular space in the well bore as follows:
wherein
Wherein r iscoIs the outer diameter of the sleeve, and the unit is m; m isaThe mass injection speed of the carbon dioxide in the annulus is kg/s; t isaThe temperature of the carbon dioxide in the annulus is expressed in K; t istThe temperature of carbon dioxide in the coiled tubing is represented by K; h isciIs the convective heat transfer coefficient of the inner surface of the annular space and has the unit of W/(m)2.K)；qaIs the volume flow rate of carbon dioxide in the annulus, and has the unit of m3/s；ΔpafThe annular internal friction pressure drop is expressed in Pa/m; capThe specific heat capacity of the carbon dioxide in the annulus is expressed in J/(kg.K); lambda [ alpha ]casThe thermal conductivity of the sleeve is expressed in W/(m.K); lambda [ alpha ]cemThe cement sheath thermal conductivity is expressed in W/(m.K); lambda [ alpha ]eIs the formation thermal conductivity in W/(m.K); t iseiIs the formation initial temperature in K; r iswbIs the borehole radius in m; t is time in units of s (seconds); rhoeIs the density of the stratum in kg/m3；CeIs the formation specific heat capacity. The unit is J/(kg.K).
(c) Temperature mixing equation
The carbon dioxide in the continuous oil pipe is mixed with the carbon dioxide in the annular space after the carbon dioxide is sprayed from the nozzle at the spraying point, and the temperature difference exists between the carbon dioxide sprayed from the nozzle and the carbon dioxide in the annular space. There will be heat exchange during the mixing process.
According to the heat convection theory, the heat absorbed by the low-temperature carbon dioxide sprayed from the nozzle in the mixing process is as follows:
Qabsorb＝mtCtd(Tmix-Tdown) (31)
similarly, in the mixing process, the heat released by the annular high-temperature carbon dioxide is as follows:
Qrelease＝maCad(Tad-Tmix) (32)
because during the mixing process, Qabsorb＝QreleasThus, a temperature mixing equation can be obtained, the temperature of the carbon dioxide after mixing being:
wherein, TmixIs the carbon dioxide temperature after heat exchange, and has the unit of K; t isadThe temperature of carbon dioxide at the downstream of the annular inner nozzle is expressed in K; cadIs the specific heat capacity of the carbon dioxide in the annulus at the injection point, and has the unit of J/(kg.K); ctdThe specific heat capacity of carbon dioxide after being jetted from the nozzle is expressed as J/(kg.K).
And S205, dispersing the wellbore internal pressure calculation equation and the wellbore internal pressure calculation equation to obtain a numerical value dispersion model.
Solving the model established in the step S203 and the step S204 by discretizing and iterating the wellbore pressure calculation equation and the wellbore pressure calculation equation.
(A) Specifically, the numerical discrete model comprises a discrete equation and an iterative equation for carbon dioxide pressure calculation in the coiled tubing, and a discrete equation and an iterative equation for carbon dioxide pressure calculation in the annulus.
Through dispersing the equation (7), the calculated dispersion equation of the pressure of the carbon dioxide in the coiled tubing is obtained as follows:
the carbon dioxide pressure calculation iterative equation in the continuous oil pipe is as follows:
by dispersing the equation (8), the calculation dispersion equation of the pressure of the carbon dioxide in the annulus is obtained as follows:
the iterative equation of the calculation of the pressure of the carbon dioxide in the annulus is as follows:
the subscript t represents a coiled tubing, the subscript a represents an annulus, the subscript j represents a jth node, and the superscript n represents an nth iteration step; such as: p is a radical ofa,jThe carbon dioxide pressure at the jth node in the annulus; p is a radical oft,jThe pressure of the carbon dioxide at the j-th node in the continuous oil pipe; rhoa,jThe carbon dioxide density of the jth node in the annulus; rhot,jThe carbon dioxide density of the j node in the continuous oil pipe;
the density of carbon dioxide at the jth node in the annulus in the nth iteration step;
the density of carbon dioxide at the jth node in the continuous oil pipe in the nth iteration step;
the carbon dioxide pressure of the jth node in the annulus in the nth iteration step is obtained;
the carbon dioxide pressure of the jth node in the continuous oil pipe during the nth iteration step; v. ofa,jThe carbon dioxide flow rate of the jth node in the annulus; v. oft,jThe carbon dioxide flow rate of the j node in the continuous oil pipe;
the carbon dioxide flow rate of the jth node in the annulus in the nth iteration step;
and the carbon dioxide flow rate of the jth node in the continuous oil pipe in the nth iteration step.
(B) The numerical discrete model comprises a discrete equation and an iterative equation for calculating the temperature of the carbon dioxide in the continuous oil pipe, and a discrete equation and an iterative equation for calculating the temperature of the carbon dioxide in the annulus.
By dispersing the equation (19), the calculation dispersion equation of the carbon dioxide temperature in the coiled tubing is obtained as follows:
the carbon dioxide temperature calculation iterative equation in the continuous oil pipe is as follows:
by dispersing the equation (26), the temperature of the carbon dioxide in the annulus is obtained, and the calculated dispersion equation is as follows:
the iterative equation of the calculation of the temperature of the carbon dioxide in the annulus is as follows:
wherein, the subscript t represents coiled tubing, the subscript a represents annular space, the subscript j represents jth node, and the superscript n represents nth iteration step, and the specific explanation can be seen in equations (34) to (37).
Equations (35), (37), (39), (41) require repeated iterative computations until the convergence condition shown in equation (42) below is satisfied:
wherein the content of the first and second substances,
to provide for a pressure convergence tolerance in the coiled tubing,
for the pressure in the annulus to converge to a tolerance,
to account for the temperature convergence tolerance in the coiled tubing,
is the temperature convergence tolerance in the annulus.
And S206, calculating the temperature and the pressure of the carbon dioxide at the last node from top to bottom in the shaft under different construction parameters based on the formation parameters, the completion parameters and the construction parameters by combining the physical property parameter calculation model and the numerical value discrete model.
Specifically, the construction parameters (nozzle diameter, injection speed, injection temperature, injection time) are divided into a plurality of groups.
A numerical discrete model established in the step S205 of formation parameters (geothermal gradient, rock heat conductivity coefficient and rock specific heat capacity) and well completion parameters (well depth, casing size, coiled tubing size, cement ring size, well bore size, casing heat conductivity coefficient, casing specific heat capacity, coiled tubing heat conductivity coefficient, coiled tubing specific heat capacity, cement ring heat conductivity coefficient and cement ring specific heat capacity);
from the plurality of sets of construction parameters, a selected set of construction parameters is input into the numerical discrete model established in step S205, and the temperature and pressure of carbon dioxide at the last node from top to bottom in the wellbore are calculated.
Wherein the temperature of the carbon dioxide at the last node from top to bottom in the wellbore comprises: carbon dioxide temperature at the last node of the annulus (tad), carbon oxide temperature at the last node in the continuous oil pipe, and carbon dioxide temperature at the last node of the annulus; the carbon oxide pressure of the last node in the coiled tubing.
And S207, calculating the temperature and the pressure of the carbon dioxide at the injection point under different construction parameters according to the temperature and the pressure of the carbon dioxide at the last node, a pressure calculation equation after the carbon dioxide flows through the nozzle, a temperature calculation equation after the carbon dioxide flows through the nozzle and a temperature mixing equation, so as to optimize the construction parameters.
Concretely, the obtained carbon oxide pressure of the last node in the coiled tubing is substituted into the carbon dioxide pressure p at the upstream of the parameter nozzle in the equation (11)upDetermining the pressure p of carbon dioxide downstream of the nozzle, i.e. the pressure of carbon dioxide after flowing through the nozzledownI.e. the carbon dioxide temperature pressure at the injection point.
Then substituting the carbon oxide temperature of the last node in the continuous oil pipe into the parameter of the carbon dioxide temperature T at the upstream of the nozzle in the equation (20)upThe temperature of carbon dioxide downstream of the nozzle, i.e., the temperature T after the carbon dioxide has flowed through the nozzle, is calculated from this equation (20)down。
Finally, substituting the carbon dioxide temperature of the last node of the annular space into the downstream carbon dioxide temperature of the nozzle in the parameter annular space in the equation (33), and calculating through the equation (33) to obtain the carbon dioxide temperature T after heat exchangemixI.e. the carbon dioxide temperature at the injection point.
And selecting different construction parameters, and calculating by referring to the step S206 and the step S207 to obtain the carbon dioxide temperature at the injection point under different parameters. And carrying out comparative analysis on the temperature and the pressure under different construction parameters, and selecting the construction parameters meeting the pressure requirement and the temperature requirement as optimized construction parameters.
The following examples are given in further detail in connection with the well and are not to be construed as limiting the invention in any way. The calculation parameters are shown in table 1.
TABLE 1
In a possible embodiment, the annular injection speed is 200kg/min, and the injection speeds in the coiled tubing are 300kg/min, 400kg/min and 500kg/min respectively. Substituting the above parameters into the numerical discrete model established in step S205, iteratively solving the carbon dioxide temperature and pressure at the injection point, and calculating the results as shown in fig. 4 and 5. In fig. 4, a1 line indicates the temperature of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 300 Kg/min); a2 line type represents the temperature of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 400 Kg/min); a3 line type represents the temperature of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 500 Kg/min); a4 line represents the temperature of carbon dioxide in the annulus (300 Kg/min injection rate in coiled tubing); a5 line type shows the temperature of carbon dioxide in the annulus (the injection speed in the coiled tubing is 400 Kg/min); a6 line represents the temperature of carbon dioxide in the annulus (the injection speed in coiled tubing is 500 Kg/min); the a7 line represents the critical temperature. In fig. 5, b1 is a line representing the pressure of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 300 Kg/min); b2 line type represents the pressure of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 400 Kg/min); b3 line type represents the pressure of carbon dioxide in the coiled tubing (the injection speed in the coiled tubing is 500 Kg/min); b4 line represents the pressure of carbon dioxide in the annulus (300 Kg/min injection rate in coiled tubing); b5 line type represents the pressure of carbon dioxide in the annulus (the injection speed in the coiled tubing is 400 Kg/min); line b6 shows the pressure of carbon dioxide in the annulus (500 Kg/min injection rate in coiled tubing).
As can be seen from fig. 4, the carbon dioxide temperatures at the injection points were 307.42K, 301.02K, 293.07K, respectively, at three different injection rates in the coiled tubing. As can be seen from FIG. 5, the carbon dioxide pressures at the injection points were 49.61MPa, 49.43MPa, and 49.14MPa, respectively, at the injection rates in the three different coiled tubing. Therefore, under the condition, due to the temperature requirement, only when the injection speed in the coiled tubing is 300kg/min, the carbon dioxide can enter the stratum in a supercritical state, and the construction requirement is met.
In summary, because few reports on methods for calculating the temperature and the pressure of the supercritical carbon dioxide jet fracturing well bore exist at present, and no consideration is given to the influence of thermal resistance of a coiled tubing, a casing and a cement sheath on heat transfer and fluid friction heat generation, the heat exchange phenomenon of carbon dioxide sprayed from a nozzle and annular carbon dioxide at the injection point is ignored. According to the invention, through comprehensively applying knowledge of related disciplines of heat transfer science and hydromechanics, considering the influence of thermal resistance of the continuous oil pipe, the casing pipe and the cement sheath on heat transfer and considering fluid friction heat generation, a temperature and pressure calculation model of the supercritical carbon dioxide jet fracturing well bore is established, and the calculation accuracy is improved, so that the construction parameters are more accurately optimized, and the effective regulation and control of the supercritical state of the carbon dioxide are realized.
Example three:
with respect to the method for controlling the supercritical carbon dioxide jet fracturing phase state in the first embodiment, referring to fig. 6, the apparatus for controlling the supercritical carbon dioxide jet fracturing phase state includes:
the parameter acquisition module 11 is used for acquiring formation parameters, completion parameters and construction parameters;
in a possible embodiment, the formation parameters include geothermal gradient, rock thermal conductivity, rock specific heat capacity; the well completion parameters comprise well depth, casing size, coiled tubing size, cement sheath size, well bore size, casing thermal conductivity, casing specific heat capacity, coiled tubing thermal conductivity, coiled tubing specific heat capacity, cement sheath thermal conductivity, and cement sheath specific heat capacity; the construction parameters include nozzle diameter, injection speed, injection temperature and injection time.
The physical property model establishing module 12 is used for establishing a physical property parameter calculation model of the carbon dioxide;
the pressure model building module 13 is used for building a wellbore pressure calculation model of the carbon dioxide, and the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the carbon dioxide flows through the nozzle;
the calculation model establishing module 14 is used for establishing a shaft temperature calculation model of the carbon dioxide, and the shaft pressure calculation model comprises a shaft internal temperature calculation equation, a temperature calculation equation after the carbon dioxide flows through the nozzle and a temperature mixing equation;
and the parameter optimization module 15 is used for calculating the temperature and the pressure of the carbon dioxide at the injection point under different construction parameters based on the formation parameters, the completion parameters and the construction parameters by combining the physical property parameter calculation model, the wellbore pressure calculation model and the wellbore temperature calculation model so as to optimize the construction parameters.
According to the mode, through comprehensive application of heat transfer science and hydromechanics, a corresponding pressure and temperature calculation model is established by considering the heat exchange phenomenon when the carbon dioxide sprayed from the nozzle is mixed with the annular carbon dioxide at the spraying point, and the calculation accuracy is improved, so that the construction parameters are more accurately optimized, and the supercritical state of the carbon dioxide is effectively regulated and controlled.
Example four:
referring to fig. 7, an embodiment of the present invention further provides an electronic device 100, including: a processor 40, a memory 41, a bus 42 and a communication interface 43, wherein the processor 40, the communication interface 43 and the memory 41 are connected through the bus 42; the processor 40 is arranged to execute executable modules, such as computer programs, stored in the memory 41.
The Memory 41 may include a high-speed Random Access Memory (RAM) and may also include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The communication connection between the network element of the system and at least one other network element is realized through at least one communication interface 43 (which may be wired or wireless), and the internet, a wide area network, a local network, a metropolitan area network, etc. may be used.
The bus 42 may be an ISA bus, PCI bus, EISA bus, or the like. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of illustration, only one double-headed arrow is shown in FIG. 7, but this does not indicate only one bus or one type of bus.
The memory 41 is used for storing a program, the processor 40 executes the program after receiving an execution instruction, and the method executed by the apparatus defined by the flow process disclosed in any of the foregoing embodiments of the present invention may be applied to the processor 40, or implemented by the processor 40.
The processor 40 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 40. The Processor 40 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; the device can also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other Programmable logic devices, discrete Gate or transistor logic devices, discrete hardware components. The various methods, steps and logic blocks disclosed in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory 41, and the processor 40 reads the information in the memory 41 and completes the steps of the method in combination with the hardware thereof.
The supercritical carbon dioxide jet fracturing phase state control device and the electronic equipment provided by the embodiment of the invention have the same technical characteristics as the supercritical carbon dioxide jet fracturing phase state control method provided by the embodiment, so the same technical problems can be solved, and the same technical effect is achieved.
The computer program product for performing the supercritical carbon dioxide jet fracturing phase state control method provided in the embodiment of the present invention includes a computer readable storage medium storing processor-executable nonvolatile program code, where instructions included in the program code may be used to execute the method described in the foregoing method embodiment, and specific implementation may refer to the method embodiment, and will not be described herein again.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the apparatus and the electronic device described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. Unless specifically stated otherwise, the relative steps, numerical expressions, and values of the components and steps set forth in these embodiments do not limit the scope of the present invention.
In the several embodiments provided in the present application, it should be understood that the disclosed apparatus and method may be implemented in other ways. The above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one logical division, and there may be other divisions when actually implemented, and for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of devices or units through some communication interfaces, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a non-volatile computer-readable storage medium executable by a processor. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (8)
1. A supercritical carbon dioxide jet fracturing phase state control method is characterized by comprising the following steps:
acquiring stratum parameters, well completion parameters and construction parameters;
establishing a physical property parameter calculation model of the supercritical carbon dioxide;
establishing a wellbore pressure calculation model of supercritical carbon dioxide, wherein the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the supercritical carbon dioxide flows through a nozzle;
establishing a shaft temperature calculation model of supercritical carbon dioxide, wherein the shaft temperature calculation model comprises a shaft inner temperature calculation equation, a temperature calculation equation after the supercritical carbon dioxide flows through a nozzle and a temperature mixing equation;
calculating the temperature and pressure of supercritical carbon dioxide at an injection point under different construction parameters based on the formation parameters, completion parameters and construction parameters by combining the physical property parameter calculation model, the wellbore pressure calculation model and the wellbore temperature calculation model so as to optimize the construction parameters;
the calculating the temperature and the pressure of the supercritical carbon dioxide at the injection point under different construction parameters based on the formation parameters, the completion parameters and the construction parameters by combining the physical property parameter calculation model, the wellbore pressure calculation model and the wellbore temperature calculation model to optimize the construction parameters comprises:
dispersing the calculation equation of the pressure in the shaft and the calculation equation of the temperature in the shaft to obtain a numerical value dispersion model;
based on the stratum parameters, the completion parameters and the construction parameters, combining the physical property parameter calculation model and the numerical value discrete model, calculating the temperature and the pressure of the supercritical carbon dioxide at the last node from top to bottom in the shaft under different construction parameters;
according to the temperature and the pressure of the supercritical carbon dioxide at the last node, a pressure calculation equation after the supercritical carbon dioxide flows through the nozzle, a temperature calculation equation and a temperature mixing equation after the supercritical carbon dioxide flows through the nozzle, and the temperature and the pressure of the supercritical carbon dioxide at the injection point under different construction parameters are calculated so as to optimize the construction parameters;
the wellbore temperature calculation model of supercritical carbon dioxide comprises:
the calculation equation of the supercritical carbon dioxide temperature in the continuous oil pipe in the shaft is as follows:
wherein
Wherein m istThe injection speed of supercritical carbon dioxide in the continuous oil pipe, TtIs the temperature, T, of supercritical carbon dioxide in a continuous oil tubeaIs the temperature of the supercritical carbon dioxide in the air, rtiIs the inner diameter of the coiled tubing, rtoIs the outer diameter of a coiled tubing CtpIs the specific heat capacity of supercritical carbon dioxide in the continuous oil pipe, UtIs the total thermal conductivity, Δ p, of the coiled tubingtfIs the friction pressure drop in the coiled tubing, qtIs the volume flow rate of supercritical carbon dioxide in the continuous oil pipe, lambdatIs the heat conductivity coefficient of the continuous oil pipe, htiIs the convection heat transfer coefficient h of the inner surface of the continuous oil pipetoThe convection heat transfer coefficient of the outer surface of the coiled tubing;
the temperature calculation equation after the supercritical carbon dioxide flows through the nozzle is as follows:
wherein p isupIs supercritical carbon dioxide pressure upstream of the nozzle, pdownThe pressure of the supercritical carbon dioxide at the downstream of the nozzle, namely the pressure of the supercritical carbon dioxide after flowing through the nozzle, k is the isentropic index of the supercritical carbon dioxide, TupIs the supercritical carbon dioxide temperature, T, upstream of the nozzledownThe temperature of the supercritical carbon dioxide at the downstream of the nozzle is the temperature of the supercritical carbon dioxide after the supercritical carbon dioxide flows through the nozzle;
the calculation equation of the supercritical carbon dioxide temperature in the annulus in the shaft is as follows:
wherein
Wherein r isciIs the inner diameter of the casing, rcoIs the outer diameter of the casing, maIs the mass injection rate, T, of supercritical carbon dioxide in the annulusaIs the temperature, T, of the supercritical carbon dioxide in the airtIs the temperature of supercritical carbon dioxide in the continuous oil pipe, hciIs the heat convection coefficient of the inner surface of the annular space, rtiIs the inner diameter of the coiled tubing, qaIs the volume flow rate, delta p, of supercritical carbon dioxide in the annulusafIs annular internal friction pressure drop, CapIs the specific heat capacity, lambda, of supercritical carbon dioxide in the annuluscasIs the sleeve heat conductivity coefficient, lambdacemIs the cement sheath thermal conductivity coefficient, lambdaeIs the formation thermal conductivity coefficient, TeiIs the formation initial temperature, rwbIs the borehole radius, t is the time, ρeIs the formation density, CeIs the formation specific heat capacity;
the temperature mixing equation is:
wherein, TmixIs supercritical carbon dioxide temperature after heat exchange, TadIs the supercritical carbon dioxide temperature at the downstream of the annular inner nozzle CadSpecific heat capacity of the annular supercritical carbon dioxide at the injection point, CtdIs the specific heat capacity of the supercritical carbon dioxide after being sprayed from the nozzle.
2. The method of claim 1, wherein the formation parameters comprise geothermal gradient, rock thermal conductivity, rock specific heat capacity;
the well completion parameters comprise well depth, casing size, coiled tubing size, cement sheath size, well bore size, casing thermal conductivity, casing specific heat capacity, coiled tubing thermal conductivity, coiled tubing specific heat capacity, cement sheath thermal conductivity, and cement sheath specific heat capacity;
the construction parameters comprise nozzle diameter, injection speed, injection temperature and injection time.
3. The method of claim 1, wherein the physical property parameter calculation model of supercritical carbon dioxide comprises:
supercritical carbon dioxide density calculation formula
The specific heat capacity of the supercritical carbon dioxide is calculated as
Wherein:
wherein T is the temperature of the supercritical carbon dioxide, p is the pressure of the supercritical carbon dioxide, ρ is the density of the supercritical carbon dioxide, δ is the contrast density, τ is the inverse contrast temperature, ρcIs critical density, TcIs the critical temperature, cpSpecific heat capacity at constant pressure, cvFor constant specific heat capacity, RcIs a gas constant, phioIs an ideal part of Helmholtz free energy, phirIs the residue partThe free energy of Helmholtz is divided,
θi 0、di、ni、ti、ci、αi、εi、βi、γi、Ci、bi、Diare all constants.
4. The method of claim 1, wherein the wellbore pressure calculation model for supercritical carbon dioxide comprises:
calculating the pressure of supercritical carbon dioxide in a continuous oil pipe in a shaft by the following equation:
and (3) calculating the pressure of the supercritical carbon dioxide in the annulus in the shaft by the following equation:
wherein
Wherein z is the longitudinal depth of the wellbore, g is the acceleration of gravity, rtiIs the inner diameter of the coiled tubing, rtoIs the outer diameter of the coiled tubing rciIs the inner diameter of the casing, ptIs the pressure of supercritical carbon dioxide in the continuous oil pipe, paIs the pressure of supercritical carbon dioxide in the annulus, ptIs the density of supercritical carbon dioxide in the continuous oil pipe，ρaIs the density, v, of the supercritical carbon dioxide in the airtIs the flow velocity of supercritical carbon dioxide in the continuous oil pipe, vaThe flow rate of supercritical carbon dioxide in the annulus, Re is the Reynolds number, DeltatIs the roughness of the coiled tubing, DeltaaThe roughness of the casing pipe;
the pressure calculation equation after the supercritical carbon dioxide flows through the nozzle is as follows:
wherein
Wherein m istThe mass injection speed of the supercritical carbon dioxide in the continuous oil pipe is shown, A is the cross section area of a nozzle, and p isupIs supercritical carbon dioxide pressure upstream of the nozzle, pdownThe pressure of the supercritical carbon dioxide at the downstream of the nozzle, i.e. the pressure of the supercritical carbon dioxide after flowing through the nozzle, rhoupIs the supercritical carbon dioxide density, p, upstream of the nozzledownIs the density of the supercritical carbon dioxide at the downstream of the nozzle, namely the density of the supercritical carbon dioxide after flowing through the nozzle, k is the isentropic index of the supercritical carbon dioxide, cpSpecific heat capacity at constant pressure, cvThe specific heat capacity is constant volume.
5. The method of claim 4, wherein the numerical discrete model comprises a supercritical carbon dioxide pressure calculation discrete equation and an iterative equation in a continuous oil pipe, and a supercritical carbon dioxide pressure calculation discrete equation and an iterative equation in an annulus;
the supercritical carbon dioxide pressure in the continuous oil pipe is calculated by the discrete equation:
the supercritical carbon dioxide pressure calculation iterative equation in the continuous oil pipe is as follows:
the discrete equation of the supercritical carbon dioxide pressure calculation in the annulus is as follows:
the iterative equation of the supercritical carbon dioxide pressure calculation in the annulus is as follows:
the subscript t represents a coiled tubing, the subscript a represents an annulus, the subscript j represents a jth node, and the superscript n represents an nth iteration step;
the supercritical carbon dioxide pressure calculation discrete equation in the continuous oil pipe and the supercritical carbon dioxide pressure calculation iterative equation in the annulus need to satisfy the following conditions:
wherein the content of the first and second substances,
to provide for a pressure convergence tolerance in the coiled tubing,
the annulus internal pressure converges to a tolerance.
6. The method of claim 1, wherein the numerical discrete model comprises a supercritical carbon dioxide temperature calculation discrete equation and an iterative equation in a continuous oil pipe, and a supercritical carbon dioxide temperature calculation discrete equation and an iterative equation in an annulus;
the calculation discrete equation of the supercritical carbon dioxide temperature in the continuous oil pipe is as follows:
the iterative equation of the supercritical carbon dioxide temperature calculation in the continuous oil pipe is as follows:
the calculation discrete equation of the supercritical carbon dioxide temperature in the annulus is as follows:
the calculation iterative equation of the temperature of the supercritical carbon dioxide in the annulus is as follows:
the subscript t represents a coiled tubing, the subscript a represents an annulus, the subscript j represents a jth node, and the superscript n represents an nth iteration step; z is the longitudinal depth of the wellbore;
the calculation discrete equation of the supercritical carbon dioxide temperature in the continuous oil pipe and the calculation iterative equation of the supercritical carbon dioxide temperature in the annular space need to satisfy the following conditions:
wherein the content of the first and second substances,
to account for the temperature convergence tolerance in the coiled tubing,
is the temperature convergence tolerance in the annulus.
7. A supercritical carbon dioxide jet fracturing phase state control device is characterized by comprising:
the parameter acquisition module is used for acquiring stratum parameters, well completion parameters and construction parameters;
the physical property model establishing module is used for establishing a physical property parameter calculation model of the supercritical carbon dioxide;
the pressure model building module is used for building a wellbore pressure calculation model of the supercritical carbon dioxide, and the wellbore pressure calculation model comprises a wellbore pressure calculation equation and a pressure calculation equation after the supercritical carbon dioxide flows through the nozzle;
the calculation model establishing module is used for establishing a shaft temperature calculation model of the supercritical carbon dioxide, and the shaft temperature calculation model comprises a shaft inner temperature calculation equation, a temperature calculation equation after the supercritical carbon dioxide flows through the nozzle and a temperature mixing equation;
the parameter optimization module is used for calculating the temperature and the pressure of the supercritical carbon dioxide at the injection point under different construction parameters based on the formation parameters, the completion parameters and the construction parameters by combining the physical property parameter calculation model, the wellbore pressure calculation model and the wellbore temperature calculation model so as to optimize the construction parameters;
the parameter optimization module is also used for dispersing the calculation equation of the pressure in the shaft and the calculation equation of the temperature in the shaft to obtain a numerical value dispersion model; based on the stratum parameters, the completion parameters and the construction parameters, combining the physical property parameter calculation model and the numerical value discrete model, calculating the temperature and the pressure of the supercritical carbon dioxide at the last node from top to bottom in the shaft under different construction parameters; according to the temperature and the pressure of the supercritical carbon dioxide at the last node, a pressure calculation equation after the supercritical carbon dioxide flows through the nozzle, a temperature calculation equation and a temperature mixing equation after the supercritical carbon dioxide flows through the nozzle, and the temperature and the pressure of the supercritical carbon dioxide at the injection point under different construction parameters are calculated so as to optimize the construction parameters;
the wellbore temperature calculation model of supercritical carbon dioxide comprises:
the calculation equation of the supercritical carbon dioxide temperature in the continuous oil pipe in the shaft is as follows:
wherein
Wherein m istThe injection speed of supercritical carbon dioxide in the continuous oil pipe, TtIs the temperature, T, of supercritical carbon dioxide in a continuous oil tubeaIs the temperature of the supercritical carbon dioxide in the air, rtiIs the inner diameter of the coiled tubing, rtoIs the outer diameter of a coiled tubing CtpIs the specific heat capacity of supercritical carbon dioxide in the continuous oil pipe, UtIs the total thermal conductivity, Δ p, of the coiled tubingtfIs the friction pressure drop in the coiled tubing, qtIs the volume flow rate of supercritical carbon dioxide in the continuous oil pipe, lambdatIs the heat conductivity coefficient of the continuous oil pipe, htiIs the convection heat transfer coefficient h of the inner surface of the continuous oil pipetoThe convection heat transfer coefficient of the outer surface of the coiled tubing;
the temperature calculation equation after the supercritical carbon dioxide flows through the nozzle is as follows:
wherein p isupIs supercritical carbon dioxide pressure upstream of the nozzle, pdownThe pressure of the supercritical carbon dioxide at the downstream of the nozzle, namely the pressure of the supercritical carbon dioxide after flowing through the nozzle, k is the isentropic index of the supercritical carbon dioxide, TupIs the supercritical carbon dioxide temperature, T, upstream of the nozzledownThe temperature of the supercritical carbon dioxide at the downstream of the nozzle is the temperature of the supercritical carbon dioxide after the supercritical carbon dioxide flows through the nozzle;
the calculation equation of the supercritical carbon dioxide temperature in the annulus in the shaft is as follows:
wherein
Wherein r isciIs the inner diameter of the casing, rcoIs the outer diameter of the casing, maIs the mass injection rate, T, of supercritical carbon dioxide in the annulusaIs the temperature, T, of the supercritical carbon dioxide in the airtIs the temperature of supercritical carbon dioxide in the continuous oil pipe, hciIs the heat convection coefficient of the inner surface of the annular space, rtiIs the inner diameter of the coiled tubing, qaIs the volume flow rate, delta p, of supercritical carbon dioxide in the annulusafIs annular internal friction pressure drop, CapIs the specific heat capacity, lambda, of supercritical carbon dioxide in the annuluscasIs the sleeve heat conductivity coefficient, lambdacemIs the cement sheath thermal conductivity coefficient, lambdaeIs the formation thermal conductivity coefficient, TeiIs the formation initial temperature, rwbIs the borehole radius, t is the time, ρeIs the formation density, CeIs the formation specific heat capacity;
the temperature mixing equation is:
wherein, TmixIs supercritical carbon dioxide temperature after heat exchange, TadIs the supercritical carbon dioxide temperature at the downstream of the annular inner nozzle CadSpecific heat capacity of the annular supercritical carbon dioxide at the injection point, CtdIs the specific heat capacity of the supercritical carbon dioxide after being sprayed from the nozzle.
8. An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any of claims 1 to 6 when executing the computer program.
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