CN110162906B - Seepage equivalent seepage resistance method for tight oil reservoir and hydroelectric simulation system - Google Patents
Seepage equivalent seepage resistance method for tight oil reservoir and hydroelectric simulation system Download PDFInfo
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Abstract
A constant-current power supply is converted from a stabilized voltage power supply by a voltage-current converter and is used for simulating constant-yield production, the yield is controlled at a lower value, fluid in a near wellbore zone is slowly extracted, sufficient time for the fluid in the far wellbore zone to flow to a wellbore is provided, the exploitation of a reservoir layer and the stability of the yield are facilitated, and therefore an experimental result is more accurate. The invention provides a seepage resistance formula considering heterogeneity, non-Darcy seepage and a cubic law, and can be better suitable for a new process for developing compact oil reservoirs such as a staged fracturing synchronous injection-production horizontal well and the like. Through the superposition principle and the parallel computation, the mutual influence among different wells is researched, the computation efficiency is improved, and the method has great guiding significance for field production. The flow rule of the shaft under different conditions can be obtained by simple experiment and calculation steps through the Thevenin theorem, the Nonton theorem, the function generator and the oscilloscope.
Description
Technical Field
The invention relates to a tight reservoir seepage equivalent seepage resistance method and a hydroelectric simulation system under a fixed-yield condition, belonging to the technical field of oil and gas field development research simulation methods.
Background
At present, the reservoir seepage simulation research method is mainly divided into numerical simulation, core experiment, water and electricity simulation and the like. Complex structural wells such as multilateral wells, staged fracturing horizontal wells, fishbone wells, injection and production wells in the same well and the like, and tertiary oil recovery technologies such as gas injection are inevitable choices for economic and effective development of compact oil reservoirs, and seepage models and numerical simulation methods of the means are complex and difficult to realize. The core experiment can be carried out by adopting an actual oil reservoir core, is relatively close to the actual geological condition and the injection-production process, and can directly measure more accurate production data, but the core, a complex structure well, a crack model and the like have large manufacturing difficulty, the experiment period is generally longer, the cost is higher, and the higher and higher requirements on the seepage simulation of the compact oil reservoir cannot be met. Therefore, water and electricity simulation experiments and equivalent seepage resistance methods are increasingly paid more attention to by people. According to the literature, the general Flow in meso pore Medium and the Analytical Solutions for 1-D Waterfood additives Capillary effects can be mutually coupled according to the hydroelectric similarity principle to develop a hydroelectric simulation experiment and an equivalent seepage resistance method, a conductive Medium is used for simulating a stratum, an electric field generated by a certain potential difference is applied to the Medium to simulate a stable seepage field in the stratum, the method is a simple, convenient and effective method for researching the steady-state production energy of a compact oil reservoir, the current and voltage data can be obtained by utilizing the circuit law, the production data can be obtained by utilizing the similar proportion relation, the method can be applied to various complex shaft and fracture models, the realization is easy, the period is short, the cost is low, and the two methods are increasingly emphasized by people in recent years.
Because the steady-current power supply is easy to burn out when being broken and is not safe enough, the traditional hydroelectric simulation experiment and the equivalent seepage resistance method only adopt the steady-voltage power supply. And therefore is only suitable for constant pressure production. The voltage-stabilizing and current-stabilizing power supply model interchange law, Thevenin's theorem and Noton's theorem are not applied, so that a large number of equation sets need to be solved for solving the model, which is difficult to apply to complex well patterns.
Therefore, the invention adopts the interchange law of the voltage-stabilizing and current-stabilizing power supply models to transform the seepage equivalent circuit diagram, can continuously simplify the well pattern, and can obtain the yield of the well under different pressures or the pressure under different yields without solving the equations of other wells again by the Thevenin theorem and the Nutton theorem. By adopting the superposition principle, the mutual influence among the wells can be obtained.
Disclosure of Invention
Aiming at the defects of the prior art, the invention discloses a dense oil reservoir seepage equivalent seepage resistance method under the condition of fixed yield.
The invention also discloses a hydroelectric simulation system for realizing the method.
Summary of the invention:
the invention introduces a steady-current power supply into a hydropower simulation experiment for the first time, converts the steady-current power supply into the steady-current power supply through a voltage-current converter on the basis of the traditional hydropower simulation device, is used for simulating production with fixed yield, controls the yield at a lower value, slowly extracts fluid in a near wellbore zone, provides enough time for the fluid in a far wellbore zone to flow to a wellbore, is more favorable for reservoir exploitation and yield stability, and has more accurate experimental results.
The invention provides a novel electric simulation system for revealing the seepage rule of a horizontal well and an equivalent seepage resistance method, which aim to solve the following problems in the prior art: first, the existing electrical simulation device and equivalent seepage resistance method are mainly applicable to the situation of constant pressure production, but for dense oil reservoirs, fluid near the wellbore flows to the wellbore during constant pressure production, a far wellbore area is difficult to draw, the yield is decreased rapidly, and the result is not accurate enough. Secondly, the existing electric simulation experiment device and the equivalent seepage resistance method do not adopt Thevenin theorem, Nuoton theorem and oscilloscope, so repeated experiment and calculation are needed to research the influence of the pressure radius of the wellhead and the width of the fracture on production, and the steps are complex. Third, the existing equivalent seepage resistance method does not simplify the circuit coupled with the reservoir, and a large number of equations need to be solved. Fourthly, the existing equivalent seepage resistance method does not adopt the superposition theorem and cannot research the influence of each well on the seepage field. Fifth, the existing equivalent seepage resistance method does not consider reservoir heterogeneity and non-Darcy seepage, and cannot be applied to tight reservoirs. And sixthly, providing a simple and convenient experiment and calculation method capable of researching the seepage rule of the staged fracturing synchronous injection-production horizontal well.
The detailed technical scheme of the invention is as follows:
the utility model provides a tight oil reservoir seepage equivalent seepage resistance method under the ration condition, includes utilizes water and electricity simulation principle to carry out following simulation experiment, its characterized in that:
in the hydroelectric simulation circuit, a stabilized voltage power supply and a resistor are connected in series and are equivalent to a stabilized current power supply and a resistor which are connected in parallel, the stabilized current power supply and the resistor are coupled to an oil reservoir, and one constant pressure well or the boundary is equivalent to two wells: an injection well having an internal resistance equal to that of the well and a wellhead pressure of 0 and a well producing a fixed flow rate without internal resistance, the flow rate being equal to the wellhead pressure divided by the internal resistance of the well;
the short circuit dual is that the pressure of the well head is 0;
the open-circuit dual is yield 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source; marking out a required parameter as a point C;
2) judging whether the equivalent circuit diagram is a simplest circuit diagram: if yes, directly solving the parameter corresponding to the point C; if not, fixing the point C and converting the stabilized voltage power supply into a current-stabilized power supply;
3) the circuit diagram is simplified to the simplest circuit diagram by using series-parallel connection of a resistor and a power supply.
According to the invention, preferably, when the tight reservoir seepage equivalent seepage resistance method under the fixed yield condition is applied to a well pattern:
the independent action of the well group or the well A means that other constant-yield wells except the well A are opened and other constant-pressure wells are short-circuited;
dualizing a superposition law into the oil reservoir, wherein the oil reservoir pressure field comprises a plurality of pressure fields generated by independent actions of different wells;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) determine if the effect of all wells on point C has been studied: if so, the sum of the influences of all the wells on the point C is the parameter of the point C; if not, taking one or a group of wells A;
3) the other constant flow wells are open-circuited, and the constant pressure well is short-circuited;
4) and (5) simplifying the circuit diagram to the simplest circuit diagram by using the series-parallel connection of the resistor and the power supply, and repeating the step 2).
Preferably according to the invention, the method is used for simulating the staged fracturing synchronous injection-production well by considering heterogeneity, non Darcy seepage and cube law:
when the oil reservoir reconstruction area has a fractal structure, the permeability is distributed in a linear, exponential and power law mode and is expressed as
k(x，y)＝k0fx(x)fy(y) (1)
Wherein k is reservoir permeability, m2；k0The near-well near-hydraulic fracture penetration rate m2(ii) a x is hydraulic fracture alongThe direction of the seam, m; y is the direction along the horizontal well, m; d is a fractal dimension; f. ofx(x)、fyAnd (y) represents the law that the permeability decreases along the directions x and y respectively.
Permeability decreases in a linear mode in the x and y directions
k(x，y)＝k0(1-Dx)(1-Dy) (2)
Permeability decreases in an exponential manner in the x and y directions
k(x，y)＝k0e-Dxe-Dy(3)
Permeability decreases in the x and y directions in a power law mode
k(x，y)＝k0x-Dy-D(4)
The reservoir reformation zone external resistance is expressed as
Wherein 1 is the hydraulic fracture length m; mu is the viscosity of the crude oil, Pa.s; r is the seepage resistance of the formation fluid; h is the reservoir height, m.
Substituting the formulas (2), (3) and (4) into the formula (5) to obtain
When low-speed non-Darcy seepage exists in crude oil in an unmodified area and the flow rate and the pressure gradient are in a power law relationship, the Ikuko-Ramey method is adopted, and the external resistance of the unmodified area is
Wherein G is an unmodified region of fidaxyFlow coefficient, m is the non-Darcy flow index. When m is 1, the flow in the unmodified zone is darcy flow, G is the permeability of the unmodified zone, luLength of the unmodified area, m.
Preferably, according to the present invention, the method for measuring the equivalent seepage resistance of tight reservoir seepage under the constant yield condition further comprises:
duality of thevenin's theorem, norton's theorem, into the reservoir, where any well or group of wells a is taken out of a well pattern, the rest of the well pattern is equivalent to well a:
a constant pressure production well B, wherein the pressure of the constant pressure production well B is equal to the pressure when the well A is open-circuit and the internal resistance is infinite, and the internal resistance of the constant pressure production well B is equal to the flow resistance generated by the rest part when the well A acts alone;
or equivalent to a production well C and an injection well D, equivalent to the production well C with internal resistance equal to the flow resistance of the rest part when the well A acts alone, the wellhead pressure is 0, the injection well D has no internal resistance, and the injection amount is equal to the yield when the well A is short-circuited and the internal resistance is 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) assuming that the other constant pressure wells except the well A are short-circuited and the constant flow rate well is open-circuited, the resistance Rb generated by the rest part of the well pattern is calculated, which respectively comprises the following two types:
2-1) the pressure pb when the well A is short-circuited and the internal resistance is 0, then the rest part is equivalent to the well B, the pressure of the well B is equal to pb, and the internal resistance is equal to Rb;
2-2) the well A is opened, the flow rate Qb is infinite in internal resistance, then the rest part is equivalent to a production well C and an injection well D, the internal resistance of the well C is equal to Rb, the wellhead pressure is 0, the well D has no internal resistance, and the injection amount is equal to Qb;
3) converting the equivalent circuit diagram into a simplest circuit diagram;
4) and obtaining production data under different working systems and wellhead sizes.
A hydroelectric simulation system comprising:
an electrolytic cell: the electrolyte solution is used for containing electrolyte solution, and saline, ionic liquid and mineral oil can be selected according to actual needs;
a voltage-to-current converter: converting the stabilized voltage power supply into a current stabilizing power supply for simulating constant-yield production, wherein the output current of the current stabilizing power supply is adjustable;
a voltmeter: the simulation well or the probe and the position sensor are connected with the simulation crack to obtain the simulated bottom hole pressure, and the simulation well or the probe and the position sensor are connected with the data acquisition unit;
an ammeter: the analog well is connected between the voltage-current converter and the analog well to obtain the yield, and is connected with the data acquisition unit;
a data acquisition unit: the device is used for transmitting the voltage value and the current value automatically recorded in the hydroelectric simulation system to a computer.
According to the optimization of the invention, when the hydroelectric simulation system is used for simulating the staged fracturing synchronous injection-production well, an oscilloscope is used for replacing a voltmeter and an ammeter to realize data acquisition of the voltage value and the current value; the function generator is used as a stabilized voltage power supply which generates sawtooth waves to obtain output values under different simulated pressures or pressure values under different simulated outputs.
Preferably, in the hydroelectric simulation system, the simulation well is a copper model of a staged fracturing synchronous injection-production well.
Preferably according to the invention, the hydroelectric simulation system further comprises: a probe and a position sensor;
the probe and position sensor are configured to: and (3) utilizing the probe to perform simulated three-dimensional direction free movement and simulated measurement in the electrolytic bath.
The technical advantages of the invention are as follows:
firstly, the constant current power supply is introduced into the hydropower simulation system and the equivalent seepage resistance method for the first time, namely, the constant output production can be considered, the yield decrement can be relieved through the constant output production, the fluid in a far well zone is used to adapt to the initiation of a compact oil reservoir, the solution step of a seepage equation set can be simplified, and the result is more accurate.
Secondly, the voltage-current converter converts the voltage-stabilized power supply into the current-stabilized power supply, so that the current-stabilized power supply is prevented from being burnt out due to open circuit, and the life safety of experimenters is greatly protected.
Thirdly, the invention provides a seepage resistance formula considering the heterogeneity, the non-Darcy seepage and the cube law, and can be better suitable for the new process for developing the compact oil reservoir such as the staged fracturing synchronous injection-production horizontal well and the like.
Fourthly, through the superposition principle and parallel calculation, the mutual influence among different wells is researched, the calculation efficiency is improved, and the method has great guiding significance for field production.
Fifthly, the flow rule of the shaft under different conditions can be obtained by the Thevenin theorem, the Nuoton theorem and the oscilloscope through simpler experiment and calculation steps.
Drawings
FIG. 1 is a schematic structural diagram of a staged fracturing synchronous injection-production horizontal well seepage law hydroelectric simulation system provided by the invention;
FIG. 2 is a schematic structural diagram of a hydroelectric simulation system for researching the influence of crack size and working system on production parameters;
in fig. 1, 2, the hydroelectric simulation system comprises: 1. a regulated power supply; 2. a voltage-to-current converter; 3. an ammeter; 4. a voltmeter; 5. an electrolytic cell; 6. a copper sheet for simulating a boundary; 7. a copper sheet for simulating injection cracks; 8. a copper sheet for simulating production cracks; 9. a probe and a position sensor; 10. a data acquisition unit; 11. a computer; 12. a function generator; 13. an oscilloscope;
FIG. 3 is a flow chart of the equivalent seepage resistance method of the present invention;
FIG. 4 is a flow chart of the present invention for calculating the effect between different wells using the superposition principle;
FIG. 5 is a flow chart of the present invention for calculating the influence of the crack size and the working system on the production parameters by adopting the Thevenin theorem and the Nuoton theorem;
FIG. 6 is a table of reservoir parameters for application examples 1, 2;
FIG. 7 is a graph of five fracture flows, listed in left-to-right order, for application example 1;
FIG. 8 shows the flow and pressure of five fractures in application example 2, in left-to-right order;
FIG. 9 shows reservoir parameters for application example 3;
FIG. 10 shows five fracture pressures in application example 3, listed in order from left to right.
Detailed Description
The embodiments of the present invention will be described in detail with reference to the accompanying drawings, but not limited thereto.
A hydroelectric simulation system comprising: an electrolytic cell 5: the electrolyte solution is used for containing electrolyte solution, and saline, ionic liquid and mineral oil can be selected according to actual needs;
voltage-to-current converter 2: converting the stabilized voltage power supply into a current stabilizing power supply for simulating constant-yield production, wherein the output current of the current stabilizing power supply is adjustable;
voltmeter 4: the analog well bottom pressure acquisition device is connected between two output ends of the voltage-current converter to acquire analog well bottom pressure and is connected with the data acquisition unit;
ammeter 3: the analog well is connected between the voltage-current converter and the analog well to obtain the yield, and is connected with the data acquisition unit;
the data collector 10: for transmitting the voltage values and current values automatically recorded in the hydro-electric simulation system to the computer 11.
When the hydroelectric simulation system is used for simulating staged fracturing synchronous injection and production wells, the oscillograph 13 is used for replacing the voltmeter 4 and the ammeter 3 to realize data acquisition of the voltage value and the current value; the function generator 12 is used as a stabilized voltage power supply which generates a sawtooth wave to obtain output values under different simulated pressures or pressure values under different simulated outputs.
In the hydroelectric simulation system, the simulation well is a horizontal copper model of a staged fracturing synchronous injection-production well, such as a copper sheet 8 used for simulating a production crack in figures 1 and 2.
The hydroelectric simulation system further comprises: a probe and position sensor 9;
the probe and position sensor 9 is used for: the probe is used to perform simulated three-dimensional free movement and simulated measurement in the electrolytic bath 5.
The working process of the hydropower simulation system comprises the following steps: the electrolytic bath 5 was placed on a bench, and a copper sheet for simulating a boundary, a crack was placed in the electrolytic bath 5. The voltage-current converter converts the stabilized voltage power supply into a stabilized current power supply, and the stabilized current power supply is connected to a copper sheet for simulating production and injecting cracks, so that the constant-flow injection and production can be simulated. The copper sheet used for simulating the boundary is connected to the stabilized voltage power supply 1 and can be used for simulating the constant voltage boundary. The voltmeter 4 is connected between the copper sheets simulating the cracks and the boundaries or between the copper sheets simulating the boundaries and the probes, the ammeter 3 is connected between the copper sheets simulating the cracks and the voltage-current converter 2, the output current of the voltage-current converter 2 is adjusted, the data collector 10 can collect the positions, the currents and the voltages of the probes in real time, and then the computer 11 is used for drawing a pressure field.
Examples 1,
The utility model provides a tight oil reservoir seepage equivalent seepage resistance method under the condition of fixed output, includes utilizes water and electricity simulation principle to carry out following simulation experiment, and in water and electricity analog circuit, constant voltage power supply and resistance series connection equivalence are that constant current power supply and resistance are parallelly connected, and in the dual oil reservoir, a constant pressure well or boundary equivalence are two wells: an injection well having an internal resistance equal to that of the well and a wellhead pressure of 0 and a well producing a fixed flow rate without internal resistance, the flow rate being equal to the wellhead pressure divided by the internal resistance of the well; the short circuit dual is that the pressure of the well head is 0; the open-circuit dual is yield 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source; marking out a required parameter as a point C;
2) judging whether the equivalent circuit diagram is a simplest circuit diagram: if yes, directly solving the parameter corresponding to the point C; if not, fixing the point C and converting the stabilized voltage power supply into a current-stabilized power supply;
3) the circuit diagram is simplified to the simplest circuit diagram by using series-parallel connection of a resistor and a power supply.
Examples 2,
The method for the seepage equivalent seepage resistance of the tight oil reservoir under the fixed-yield condition as described in the example 1 comprises the following steps of:
the independent action of the well group or the well A means that other constant-yield wells except the well A are opened and other constant-pressure wells are short-circuited;
dualizing a superposition law into the oil reservoir, wherein the oil reservoir pressure field comprises a plurality of pressure fields generated by independent actions of different wells;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) determine if the effect of all wells on point C has been studied: if so, the sum of the influences of all the wells on the point C is the parameter of the point C; if not, taking one or a group of wells A;
3) the other constant flow wells are open-circuited, and the constant pressure well is short-circuited;
4) and (5) simplifying the circuit diagram to the simplest circuit diagram by using the series-parallel connection of the resistor and the power supply, and repeating the step 2).
Examples 3,
A tight reservoir permeability equivalent permeability method under fixed-volume conditions as described in example 1, couples the davinan and norton theorems into a reservoir, wherein any well or group of wells a is removed from a well pattern, and the remainder of the pattern is equivalent to well a:
a constant pressure production well B, wherein the pressure of the constant pressure production well B is equal to the pressure when the well A is open-circuit and the internal resistance is infinite, and the internal resistance of the constant pressure production well B is equal to the flow resistance generated by the rest part when the well A acts alone;
or equivalent to a production well C and an injection well D, equivalent to the production well C with internal resistance equal to the flow resistance of the rest part when the well A acts alone, the wellhead pressure is 0, the injection well D has no internal resistance, and the injection amount is equal to the yield when the well A is short-circuited and the internal resistance is 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) assuming that the other constant pressure wells except the well A are short-circuited and the constant flow rate well is open-circuited, the resistance Rb generated by the rest part of the well pattern is calculated, which respectively comprises the following two types:
2-1) the pressure pb when the well A is short-circuited and the internal resistance is 0, then the rest part is equivalent to the well B, the pressure of the well B is equal to pb, and the internal resistance is equal to Rb;
2-2) the well A is opened, the flow rate Qb is infinite in internal resistance, then the rest part is equivalent to a production well C and an injection well D, the internal resistance of the well C is equal to Rb, the wellhead pressure is 0, the well D has no internal resistance, and the injection amount is equal to Qb;
3) converting the equivalent circuit diagram into a simplest circuit diagram;
4) and obtaining production data under different working systems and wellhead sizes.
As shown in fig. 2, in order to study the yield of a crack under different pressures or the pressures under different yields during constant flow production, a function generator is used to generate a sawtooth wave, the sawtooth wave is input to an X channel and a voltage-current converter of an oscilloscope to obtain a current which changes along with a time period, the current is input to a copper sheet which simulates the crack to be studied, the voltage between the copper sheet or a probe and the copper sheet at a simulated boundary is input to a Y channel of the oscilloscope, and the relationship between the crack yield and a pressure field can be obtained.
The equivalent seepage resistance method of the invention has the working process that: drawing an equivalent circuit diagram of the oil reservoir seepage, solving the internal resistance and the external resistance, marking the point where the required parameters are located, and setting the point as a point C.
When the oil reservoir reconstruction area has a fractal structure, the permeability is distributed in a linear, exponential and power law mode and is expressed as
k(x，y)＝k0fx(x)fy(y) (1)
Wherein k is reservoir permeability, m2；k0The near-well near-hydraulic fracture penetration rate m2(ii) a x is the direction along the hydraulic fracture, m; y is the direction along the horizontal well, m; d is a fractal dimension; f. ofx(x)、fyAnd (y) represents the law that the permeability decreases along the directions x and y respectively.
Permeability decreases in a linear mode in the x and y directions
k(x，y)＝k0(1-Dx)(1-Dy) (2)
Permeability decreases in an exponential manner in the x and y directions
k(x，y)＝k0e-Dxe-Dy(3)
Permeability decreases in the x and y directions in a power law mode
k(x，y)＝k0x-Dy-D(4)
The reservoir reformation zone external resistance is expressed as
Wherein 1 is the hydraulic fracture length m; mu is the viscosity of the crude oil, Pa.s; r is the seepage resistance of the formation fluid; h is the reservoir height, m.
Substituting the formulas (2), (3) and (4) into the formula (5) to obtain
When low-speed non-Darcy seepage exists in crude oil in an unmodified area and the flow rate and the pressure gradient are in a power law relationship, the Ikuko-Ramey method is adopted, and the external resistance of the unmodified area is
Wherein G is the non-Darcy flow coefficient of the unmodified area, and m is the non-Darcy flow index. When m is 1, the flow in the unmodified zone is darcy flow, G is the permeability of the unmodified zone, luLength of the unmodified area, m.
The flow in the hydraulic fracture conforms to the cubic law, and the internal resistance of the hydraulic fracture is
Wherein w is the hydraulic fracture width, m;
as shown in fig. 3, the fixed point C simplifies the equivalent circuit diagram by using the law of interchange between the regulated power supply and the law of series-parallel connection. A well or boundary with a pressure p and an internal resistance R can be equivalent to two wells: one well with an internal resistance of R and a pressure of 0 and one well with a flow of Q, and vice versa. The relationship among p, Q and R is as follows
The equivalent seepage resistance method shown in fig. 4 can adopt parallel calculation, each calculation node corresponds to a well a, the constant flow wells except the wells a are opened, the constant pressure wells are short-circuited, the method shown in fig. 3 can be used for solving the influence of the wells a on the flow of all the wells, a matrix is filled, then each node takes out the influence of all the wells on the wells a from the matrix, and the influence is superposed to obtain the production data of the wells a.
As shown in FIG. 5, a well group or well A is taken from the pattern, and the remainder of the pattern may be equivalent to a pressure p for well AbInternal resistance of RbAssuming that the well A is open and has infinite internal resistance, the pressure of the well A, p, can be determined by the method shown in FIG. 3 and FIG. 4bIf the constant flow rate well of the rest part is open-circuited and the constant pressure well is short-circuited, the flow resistance generated by the rest part is Rb(ii) a Can also be equivalent to a production well C and an injection well D, and the internal resistance of the well C is RbWell head pressure is 0, well D internal resistance is 0, flow is QbAssuming that well A is short-circuited and has an internal resistance of 0, the method shown in FIG. 3 and FIG. 4 can be used to determine the flow rate of well A, i.e., Qb. The flow law of the well A under different conditions can be obtained by changing the conditions of the well A.
Application examples 1,
Based on the paper of Temporal scale analysis of two phase flow in fractional flow well, the patent of US 2015/0007996 and the patent of US 2014/015603, a staged fracturing synchronous injection and production horizontal well model as shown in fig. 1 is researched, namely, an injection fracture and a production fracture exist in the same horizontal well at the same time, and parameters are shown in fig. 6. The seepage resistance method and the experimental device in the Chinese patent CN201610822268.2 are respectively adopted to obtain the hydraulic fracture yield and the injection amount, and the superposition principle and the stabilized voltage power supply interchange theorem are adopted, so that the obtained five fracture flows are sequentially shown in the figure 7 from left to right. The experimental result is used as a reference solution to verify the correctness of the method. The error is mainly due to the boundary effect of the hydraulic fracture.
Application examples 2,
The research data of the staged fracturing synchronous injection-production horizontal well model shown in fig. 6 shows that the production and injection fractures are produced at a constant flow rate, and the yield and injection amount of the five fractures are sequentially shown in fig. 8 from left to right. The equivalent seepage resistance method and the hydroelectric simulation system are adopted to obtain the pressure of each crack, one side boundary is taken, the other side boundary and all cracks are equivalent to a fixed kill, and when the total injection quantity of the obtained well pattern is equal to the total output, the pressure of the crack closest to the boundary is equal to the boundary pressure. By adopting the stabilized voltage power supply and stabilized current power supply interchange theorem, the obtained five crack pressures are sequentially shown in FIG. 8 from left to right, and the correctness of the method is further verified. The error mainly results from the calculated rounding error.
Application examples 3,
The method comprises the steps of researching a staged fracturing synchronous injection-production horizontal well model shown in figure 1, wherein the areas among fractures comprise a modified area and an unmodified area, the permeability k of the modified area is reduced to 10% along an x axis, the permeability k of the unmodified area is reduced to 10% along a y axis, low-speed non-Darcy seepage exists in the unmodified area, parameters are shown in figure 9, and five fracture pressures obtained by the equivalent seepage method are sequentially shown in figure 10 from left to right. When the reservoir has non-Darcy seepage and heterogeneity, the pressure of the production well is reduced.
While the principles and embodiments of this invention have been described and illustrated herein to provide a practical example, it will be appreciated by those skilled in the art that variations may be made in the embodiments and applications without departing from the principles and spirit of the invention. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (7)
1. The utility model provides a tight oil reservoir seepage equivalent seepage resistance method under the ration condition, includes utilizes water and electricity simulation principle to carry out following simulation experiment, its characterized in that:
in the hydroelectric simulation circuit, a stabilized voltage power supply and a resistor are connected in series and are equivalent to a stabilized current power supply and a resistor which are connected in parallel, the stabilized current power supply and the resistor are coupled to an oil reservoir, and one constant pressure well or the boundary is equivalent to two wells: an injection well with a wellhead pressure of 0, referred to as well a, a well producing at a fixed flow rate without internal resistance, referred to as well B, said wells being equivalent to fixed pressure well C, the well C pressure being equal to well B production multiplied by the internal resistance of well a; well C or constant pressure boundary is equivalent to A, B two wells: the internal resistance of the injection well A is equal to the internal resistance of the well C; the wellhead pressure of the well C is 0; well B produces a fixed amount without internal resistance, the amount being equal to the wellhead pressure divided by the internal resistance of the well;
the short circuit dual is that the pressure of the well head is 0;
the open-circuit dual is yield 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source; marking out a required parameter as a point C; the required parameter is the well C of the required production or pressure;
2) judging whether the equivalent circuit diagram is a simplest circuit diagram: if yes, directly solving the parameter corresponding to the point C; if not, fixing the point C and converting the stabilized voltage power supply into a current-stabilized power supply;
3) the circuit diagram is simplified to the simplest circuit diagram by using series-parallel connection of a resistor and a power supply.
2. The method for simulating the tight reservoir seepage equivalent seepage resistance under the condition of fixed yield according to claim 1, which is used for simulating the staged fracturing synchronous injection and production well by considering the heterogeneity, the non-Darcy seepage and the cube law:
when the oil reservoir reconstruction area has a fractal structure, the permeability is distributed in a linear, exponential and power law mode and is expressed as
k(x，y)＝k0fx(x)fy(y) (1)
Wherein k is reservoir permeability, m2；k0The near-well near-hydraulic fracture penetration rate m2(ii) a x is the direction along the hydraulic fracture, m; y is the direction along the horizontal well, m; d is a fractal dimension; f. ofx(x)、fy(y) respectively representing the law that the permeability decreases along the x direction and the y direction;
permeability decreases in a linear mode in the x and y directions
k(x，y)＝k0(1-Dx)(1-Dy) (2)
Permeability decreases in an exponential manner in the x and y directions
k(x，y)＝k0e-Dxe-Dy(3)
Permeability decreases in the x and y directions in a power law mode
k(x，y)＝k0x-Dy-D(4)
The reservoir reformation zone external resistance is expressed as
Wherein 1 is the hydraulic fracture length m; mu is the viscosity of the crude oil, Pa.s; r is the seepage resistance of the formation fluid; h is the reservoir height, m;
substituting the formulas (2), (3) and (4) into the formula (5) to obtain
Wherein l is the hydraulic fracture length, m; mu is the viscosity of the crude oil, Pa.s; r is the seepage resistance of the formation fluid; h is the reservoir height, m;
when low-speed non-Darcy seepage exists in crude oil in an unmodified area and the flow rate and the pressure gradient are in a power law relationship, the Ikuko-Ramey method is adopted, and the external resistance of the unmodified area is
Wherein G is the non-Darcy flow coefficient of the unmodified area, and m is the non-Darcy flow index; when m is 1, the flow in the unmodified zone is darcy flow, G is the permeability of the unmodified zone, luLength of the unmodified area, m;
the flow in the hydraulic fracture conforms to the cubic law, and the internal resistance of the hydraulic fracture is
Wherein w is the hydraulic fracture width, m.
3. The tight reservoir seepage equivalent seepage resistance method under the condition of fixed yield according to claim 1, wherein when the tight reservoir seepage equivalent seepage resistance method under the condition of fixed yield is applied to a well pattern:
the independent action of the well group or the independent action of the well A means that other constant-yield wells except the well A are opened and other constant-pressure wells are short-circuited;
dualizing a superposition law into the oil reservoir, wherein the oil reservoir pressure field comprises a plurality of pressure fields generated by independent actions of different wells;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) determine if the effect of all wells on point C has been studied: if so, the sum of the influences of all the wells on the point C is the parameter of the point C; if not, taking one or a group of wells A;
3) the other constant flow wells are open-circuited, and the constant pressure well is short-circuited;
4) and (5) simplifying the circuit diagram to the simplest circuit diagram by using the series-parallel connection of the resistor and the power supply, and repeating the step 2).
4. The tight reservoir seepage equivalent seepage resistance method under the fixed-yield condition as claimed in claim 1, wherein the tight reservoir seepage equivalent seepage resistance method under the fixed-yield condition further comprises:
duality of thevenin's theorem, norton's theorem, into the reservoir, where any well or group of wells a is taken out of a well pattern, the rest of the well pattern is equivalent to well a:
a constant pressure production well B, wherein the pressure of the constant pressure production well B is equal to the pressure when the well A is open-circuit and the internal resistance is infinite, and the internal resistance of the constant pressure production well B is equal to the flow resistance generated by the rest part when the well A acts alone;
or equivalent to a production well C and an injection well D, wherein the equivalent internal resistance of the production well C is equal to the flow resistance generated by the rest part when the well A acts alone, the wellhead pressure is 0, the injection well D has no internal resistance, and the injection amount is equal to the yield when the well A is short-circuited and the internal resistance is 0;
the method comprises the following specific processes:
1) drawing an equivalent circuit diagram of the oil reservoir seepage to obtain the internal resistance and the external resistance of the equivalent current source;
2) assuming that the other constant pressure wells except the well A are short-circuited and the constant flow rate well is open-circuited, the resistance Rb generated by the rest part of the well pattern is calculated, which respectively comprises the following two types:
2-1) the pressure pb when the well A is short-circuited and the internal resistance is 0, then the rest part is equivalent to the well B, the pressure of the well B is equal to pb, and the internal resistance is equal to Rb;
2-2) the well A is opened, the flow rate Qb is infinite in internal resistance, then the rest part is equivalent to a production well C and an injection well D, the internal resistance of the well C is equal to Rb, the wellhead pressure is 0, the well D has no internal resistance, and the injection amount is equal to Qb;
3) converting the equivalent circuit diagram into a simplest circuit diagram;
4) and obtaining production data under different working systems and wellhead sizes.
5. A hydroelectric simulation system of the tight reservoir seepage equivalent seepage resistance method of claim 1, comprising:
an electrolytic cell: is used for containing electrolyte solution and is used for containing electrolyte solution,
a voltage-to-current converter: converting the stabilized voltage power supply into a current stabilizing power supply for simulating constant-yield production, wherein the output current of the current stabilizing power supply is adjustable;
a voltmeter: the simulation well or the probe and the position sensor are connected with the simulation crack to obtain the simulated bottom hole pressure, and the simulation well or the probe and the position sensor are connected with the data acquisition unit;
an ammeter: the analog well is connected between the voltage-current converter and the analog well to obtain the yield, and is connected with the data acquisition unit;
a data acquisition unit: the device is used for transmitting the voltage value and the current value automatically recorded in the hydroelectric simulation system to a computer.
6. The system for simulating the hydropower of the tight oil reservoir seepage equivalent seepage flow resistance method according to claim 5, wherein when the system for simulating the staged fracturing synchronous injection and production well, an oscilloscope is used for replacing a voltmeter and an ammeter to realize data acquisition of the voltage value and the current value; the function generator is used as a stabilized voltage power supply which generates sawtooth waves to obtain output values under different simulated pressures or pressure values under different simulated outputs.
7. The hydropower simulation system of the tight reservoir seepage equivalent seepage resistance method according to claim 6, wherein in the hydropower simulation system, the simulation well is a horizontal copper model of a staged fracturing synchronous injection and production well.
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