CN112761607B - Interactive sand-filled fracture conductivity calculation method for intersection of hydraulic fracture and natural fracture - Google Patents

Interactive sand-filled fracture conductivity calculation method for intersection of hydraulic fracture and natural fracture Download PDF

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CN112761607B
CN112761607B CN202110164362.4A CN202110164362A CN112761607B CN 112761607 B CN112761607 B CN 112761607B CN 202110164362 A CN202110164362 A CN 202110164362A CN 112761607 B CN112761607 B CN 112761607B
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sand
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bank
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CN112761607A (en
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卢聪
马莅
郭建春
曾祺俊
张涛
孟宪波
刘彦辉
周广清
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Southwest Petroleum University
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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
    • 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
    • E21B43/267—Methods for stimulating production by forming crevices or fractures reinforcing fractures by propping
    • 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
    • E21B47/00—Survey of boreholes or wells
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
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Abstract

The invention relates to a method for calculating the flow conductivity of an interactive sand-filled fracture intersected by a hydraulic fracture and a natural fracture, which comprises the following steps: the interactive sand filling fracture consists of a hydraulic fracture, a natural fracture 1 and a natural fracture 2, wherein an outlet of the hydraulic fracture is connected with inlets of the two natural fractures, and the hydraulic fracture is vertical to the natural fractures; processing the sand bank shape in the crack, simplifying the crack sand bank shape into a cuboid and a triangular prism which is in common and coplanar with the cuboid, and obtaining the basic characteristic parameters of the sand bank shape; then calculating the single-slit flow conductivity based on a Kozeny model, wherein the single-slit flow conductivity comprises the flow conductivity of a rectangular sand bank and the flow conductivity of a triangular sand bank; correcting a single-slit flow conductivity calculation formula through experimental parameters obtained by a slit net flow conductivity experiment; and finally, calculating the flow conductivity of the interactive sand-filled fracture based on the water-electricity similarity principle. The invention can optimize hydraulic fracturing design and improve hydraulic fracturing effect, has reliable principle and strong field operability and has wide market prospect.

Description

Interactive sand-filled fracture conductivity calculation method for intersection of hydraulic fracture and natural fracture
Technical Field
The invention relates to the field of petroleum engineering, in particular to a method for calculating the flow conductivity of an interactive sand-filled fracture intersected with a hydraulic fracture and a natural fracture in the field of hydraulic fracturing.
Background
Along with the continuous deepening of oil and gas exploration and development, unconventional oil and gas resources show huge exploration and development potential. The hydraulic fracturing is an important measure for increasing production and improving unconventional oil and gas reservoirs, and is mainly characterized in that high-pressure liquid (pad fluid) is injected into a reservoir under the condition that the fracture pressure of the reservoir or the closing pressure of natural fractures, the hydraulic fractures are generated in the reservoir and simultaneously communicated with the natural fractures, and the hydraulic fractures and the natural fractures are mutually interwoven to form interactive fractures. Then, the fracturing fluid (sand carrying fluid) with the proppant is injected continuously, and the proppant is transported and settled in the fracture to form a sand bank. After the fracturing fluid is drained back, the propping agent left in the fracture can play a role of preventing the fracture from being completely closed, so that the fracture still keeps a certain opening degree under the closing pressure, a sand-filled fracture which has a certain length and allows fluid to flow is formed in the stratum, the oil-gas seepage condition is improved by utilizing the high flow conductivity of the fracture, and the productivity of an oil-gas well is further improved.
The fracture conductivity is an index for evaluating the mobility of fluid in a fracture, the higher the conductivity is, the better the mobility of the fluid in the fracture is, and the conductivity of the fracture is usually determined directly by the size of the conductivity of the fracture, so that the research on the fracture conductivity has a vital role in evaluating the hydraulic fracturing effect and optimizing the hydraulic fracturing technology.
At present, the diversion capacity of a fracture is mainly obtained through an experimental mode at home and abroad, the diversion capacity of the fracture is calculated by a theoretical mode at least, and the calculation method for the diversion capacity of the interactive sand-filled fracture under the condition that the hydraulic fracture and the natural fracture are intersected is a little research at home and abroad, cannot meet the design requirement of the current hydraulic fracturing construction, and cannot provide effective guidance for hydraulic fracturing optimization.
Disclosure of Invention
The invention aims to provide a method for calculating the flow conductivity of an interactive sand-filled fracture intersected with a hydraulic fracture and a natural fracture.
In order to achieve the technical purpose, the invention adopts the following technical scheme.
Aiming at the calculation of the flow conductivity of the interactive sand-filled fracture under the condition of intersection of the hydraulic fracture and the natural fracture, the method firstly processes the sand bank shape in the single fracture (comprising the hydraulic fracture and the natural fracture) to obtain the basic characteristic parameters of the sand bank shape. Then calculating the single-slit flow conductivity (including the flow conductivity of the rectangular sand bank and the flow conductivity of the triangular sand bank) based on a Kozeny model; and correcting the single-slit flow conductivity calculation formula through the experimental parameters obtained by the slit net flow conductivity experiment. And finally, calculating the flow conductivity of the interactive sand-filled fracture based on the water-electricity similarity principle.
Because the fluid flow inside the fracture network and the proppant laying form are very complicated in the practical situation of the stratum, some simplifying assumptions on the model are necessary: the momentum reduction caused by collision of fluid and a wall surface is not counted at the crack interaction position; the fluid flow in the cracks conforms to Darcy's law; thirdly, the flow conductivity is totally dependent on the sand bank in the crack, and the seepage capacity of the reservoir matrix is not considered; the arrangement modes of the propping agents are all arranged in a prismatic shape; and fifthly, completely closing the crack without the proppant accumulation part in the crack, and neglecting the permeability.
The interactive sand-filled fracture conductivity calculation method for intersection of the hydraulic fracture and the natural fracture sequentially comprises the following steps of:
(1) processing the sand bank form formed in the interactive cracks, and then extracting relevant characteristic parameters of the sand bank form, wherein the process comprises the following steps:
the interactive sand filling crack is composed of a hydraulic crack, a natural crack 1 and a natural crack 2, an outlet of the hydraulic crack is connected with inlets of the two natural cracks, the hydraulic crack and the natural cracks are perpendicular to each other, the shapes of the hydraulic crack and the sand bank in the natural cracks are simplified into a cuboid, and a common triangular prism is arranged on the cuboid, so that the section of the shape of the sand bank in the crack is a rectangle, a common triangle is arranged on the rectangle, and the opposite angle of the common triangle is a slope angle.
The relevant characteristic parameters include: the balance height of the sand bank in the hydraulic fracture and the natural fracture is H; width W of sand bank in hydraulic fracturehThe width of the sand bank in the natural crack 1 and the natural crack 2 is W respectivelyn1、Wn2(ii) a The length of the hydraulic fracture sand bank comprises the length L of a rectangular sand bankhAAnd the length L of the triangular sand bankhBThe length of the natural crack 1 sand bank comprises the length L of a rectangular sand banknA1And the length L of the triangular sand banknB1And the length of the natural crack 2 sand bank comprises the length L of a rectangular sand banknA2And the length L of the triangular sand banknB2(ii) a The slope angle of the sand bank in the hydraulic fracture is alpha, and the slope angles of the sand bank in the natural fracture 1 and the natural fracture 2 are beta respectively1、β2。
(2) Calculating the flow conductivity of the rectangular sand bank, wherein the process is as follows:
calculating the number n of sand layers in the width direction of the crack according to the following formula:
Figure BDA0002937124430000021
in the formula: r ispIs the proppant radius, m;
w is the width of sand bank, W is W in hydraulic fracturehW in natural fracture 1 ═ Wn1W in natural fracture 2 ═ Wn2，m；
HpThe distance m between adjacent layers of proppants in the sand bank under the condition that the proppants are distributed in a prismatic shape.
② the total amount N of the proppant in the rectangular sand bank comprises the amount N of the proppant on the wall surface of the sand bankfNumber of proppant N in sand bankiThe calculation formula is as follows (Gaojinjian. Complex slotted net proppant sedimentation rule and flow conductivity research [ D)].2016)：
Figure BDA0002937124430000022
Figure BDA0002937124430000023
Ni＝N-Nf (4)
In the formula: h is the sand bank balance height m;
l is the length of the sand bank, and when the flow conductivity of the rectangular sand bank is calculated, L is equal to L in the hydraulic fracturehAIn natural fracture 1, L is LnA1L ═ L in natural fracture 2nA2，m；
C1And C2Is constant, when n is 3i-2, C1＝2i-2，C20; when n is 3i-1, C1＝2i-1，C2＝1；
When n is 3i, C1＝2i，C21, wherein i ═ 1, 2, 3 ·.
Thirdly, calculating the total porosity phi of the rectangular sand bank by the following formula based on the definition of the physical meaning of the porosity:
Figure BDA0002937124430000031
and fourthly, based on a Kozeny model, regarding the sand levee formed by the accumulation of the proppant as a capillary tube model, and calculating the permeability K of the rectangular sand levee in the crack according to the following formula:
Figure BDA0002937124430000032
in the formula: tau is the capillary tortuosity and takes a value of 1.5;
and r is the pore radius of the rectangular sand bank, m.
The calculation formula of the pore radius r of the rectangular sand bank is as follows:
Figure BDA0002937124430000033
in the formula: r is1The radius of the pore on the wall surface of the sand bank is m;
r2is the internal pore radius of the sand bank, m.
The sand bank wall surface pore is composed of a crack wall surface and a semi-sphere of the propping agent, the calculation formula of the sand bank wall surface pore radius is shown as a formula (8), the sand bank internal pore is formed by piling up propping agent particles, and the calculation formula of the sand bank internal pore radius is shown as a formula (9).
Figure BDA0002937124430000034
Figure BDA0002937124430000035
In the formula: n is a radical of1The number of the sand wall surface pores is;
N2the number of the inner pores of the sand bank.
Sand bank wall surface pore number N1And the number N of inner pores of the sand bank2The calculation formula is as follows:
Figure BDA0002937124430000036
Figure BDA0002937124430000037
in the formula: when n is 3i-2, C3＝0，C42 i-2; when n is 3i-1, C3＝1，C42 i-2; when n is 3i, C3＝1，C4＝2i-1，i＝1、2、3···。
Calculating the flow conductivity of the rectangular sand bank, wherein the calculation formula is as follows:
Figure BDA0002937124430000038
in the formula: fAIs the flow conductivity of a rectangular sand bank, mu m2·m。
(3) Calculating the flow conductivity of the triangular sand bank, wherein the process is as follows:
the derivation process of the triangular sand bank flow conductivity is similar to that of a rectangle, and the calculation formula of the triangular sand bank flow conductivity is obtained as follows:
Figure BDA0002937124430000041
in the formula: fBIs the flow conductivity of a triangular sand bank, mu m2·m；
L is the length of the sand bank, and when the flow conductivity of the triangular sand bank is calculated, L is equal to L in the hydraulic fracturehBIn natural fracture 1, L is LnB1L ═ L in natural fracture 2nB2，m；
C5The proportional coefficient is 0.5;
x is a slope angle, X in the hydraulic fracture is alpha, and X in the natural fracture 1 is beta1X ═ β in natural fracture 22，°。
(4) Under the condition of high closure stress of an actual stratum, the flow conductivity of a propped fracture is obviously reduced due to the conditions of proppant embedding, crushing, compaction deformation and the like. And correcting the sand bank flow conductivity formula through flow conductivity experiment test data:
Figure BDA0002937124430000042
in the formula: fcAThe flow conductivity of the rectangular sand bank is adjusted to be in the micron range under the condition of closed pressure2·m；
FcBIn order to correct the flow conductivity of the triangular sand bank under the condition of closed pressure, the diameter is mum2·m；
C6For correcting the coefficient, the calculation formula is as follows (Wangxinghui. calculation model of flow conductivity of the seam network based on the principle of water and electricity similarity [ J)]Petroleum machine, 2017):
Figure BDA0002937124430000043
in the formula: sigmapThe compressive strength of the proppant particles is MPa;
Pcthe reservoir fracture closure pressure is MPa;
rpthe radius of the proppant is the radius of the proppant,m；
r20/40radius of the proppant of 20/40 mesh, m.
(5) Based on the principle of water-electricity similarity, in the porous medium flow, the pressure difference is regarded as a voltage difference, and the fluid flow is regarded as an electric current, so that the seepage resistance is equivalent to resistance. R1、R2Is seepage resistance of a triangular sand bank and a rectangular sand bank in the hydraulic fracture R3、R4Is the seepage resistance of a rectangular sand bank and a triangular sand bank in a natural crack 1, R5、R6The seepage resistance of the rectangular sand bank and the triangular sand bank in the natural crack 2 is shown. And regarding seepage between the rectangular sand bank and the triangular sand bank on the same fracture as series connection, and regarding seepage between two natural fractures as parallel connection.
Based on Darcy's law, calculating the seepage resistance of the sand bank as follows:
Figure BDA0002937124430000044
in the formula: rAIs the seepage resistance of the rectangular sand bank and the R in the hydraulic fractureA＝R2R in natural fracture 1A＝R3R in natural fracture 2A＝R5，mPa·s/(μm2·m)；
RBIs the seepage resistance of the triangular sand bank and the R in the hydraulic fractureB＝R1R in natural fracture 1B＝R4In natural cracks 2
RB＝R6，mPa·s/(μm2·m)；
Mu is the fracturing fluid viscosity, mPa · s;
LAis the length of the rectangular sand bank and the hydraulic fracture middle LA＝LhAL in Natural fracture 1A＝LnA1L in Natural crack 2A＝LnA2，m；
LBIs the length of the triangular sand bank and the hydraulic fracture middle LB＝LhBL in Natural fracture 1B＝LnB1In natural cracks 2
LB＝LnB2，m。
Based on the principle of hydroelectric similarity, the total seepage resistance R of the hydraulic fracture and the natural fracture in an interaction state is deduced, and the calculation formula is as follows:
Figure BDA0002937124430000051
in the formula: r is the total seepage resistance of the interactive sand-filled fracture in the interactive state of the hydraulic fracture and the natural fracture, and mPa & s/(mum)2·m)。
(6) Calculating the flow conductivity F of the interactive sand-filled fracture under the interactive state of the hydraulic fracture and the natural fractureRThe calculation formula is as follows:
Figure BDA0002937124430000052
compared with the conventional flow conductivity calculation method, the method has the beneficial effects that: optimizing the shape of the sand levee in the single slit into the combination of a rectangular sand levee and a triangular sand levee, respectively calculating the flow conductivity of the sand levee based on a Kozeny model, and then correcting the single slit flow conductivity calculation model through experimental parameters obtained by a slit network experiment; and finally, establishing a method for calculating the flow conductivity of the interactive sand-filled fracture in the interaction state of the hydraulic fracture and the natural fracture based on the hydropower similarity principle.
Drawings
FIG. 1 is a schematic view of an alternate sand pack fracture.
Fig. 2 is a schematic diagram of sand bank division in a fracture.
Figure 3 is a schematic of proppant placement in a fracture.
FIG. 4 is an equivalent circuit diagram of an alternate sand pack fracture.
Detailed Description
The invention is further illustrated below with reference to the figures and examples in order to facilitate the understanding of the invention by a person skilled in the art. It is to be understood that the invention is not limited in scope to the specific embodiments, but is intended to cover various modifications within the spirit and scope of the invention as defined and defined by the appended claims, as would be apparent to one of ordinary skill in the art.
Taking a certain block of oil well W as an example, the closing pressure of the stratum fracture is 52MPa, the compressive strength of 20/40-mesh propping agent (the diameter is 0.6mm) is 69MPa, and the viscosity of the fracturing fluid is 5 mPas. And the proppant enters two sides of the natural fracture from the hydraulic fracture and is accumulated in the hydraulic fracture and the natural fracture to form a sand bank. And because the widths of the two natural fractures are not consistent, the sand bank forms formed in the hydraulic fracturing process are different, and the flow conductivity of the interactive sand-filled fracture is calculated according to the different forms.
A method for calculating the flow conductivity of an interactive sand-filled fracture intersected with a hydraulic fracture and a natural fracture sequentially comprises the following steps:
(1) and processing the sand bank morphology formed in the interactive fractures, and then extracting relevant characteristic parameters of the sand bank morphology.
As shown in figure 1, the interactive sand-filled fracture is composed of a hydraulic fracture, a natural fracture 1 and a natural fracture 2, wherein the outlet of the hydraulic fracture is connected with the inlets of the two natural fractures, and the hydraulic fracture and the natural fracture are perpendicular to each other. As shown in fig. 2, the sand bank shape in the hydraulic fracture and the natural fracture is simplified into a cuboid and a triangular prism which is common to the cuboid, so that the cross section of the sand bank shape in the fracture is a rectangle and a triangle which is common to the rectangle, and the opposite angle of the common side is a slope angle.
The balance height of the sand bank in the hydraulic fracture and the natural fracture is H; width W of sand bank in hydraulic fracturehThe width of the sand bank in the natural crack 1 and the natural crack 2 is W respectivelyn1、Wn2(ii) a The length of the hydraulic fracture sand bank comprises the length L of a rectangular sand bankhAAnd the length L of the triangular sand bankhBThe length of the natural crack 1 sand bank comprises the length L of a rectangular sand banknA1And the length L of the triangular sand banknB1And the length of the natural crack 2 sand bank comprises the length L of a rectangular sand banknA2And the length L of the triangular sand banknB2(ii) a The slope angle of the sand bank in the hydraulic fracture is alpha, and the slope angles of the sand bank in the natural fracture 1 and the natural fracture 2 are beta respectively1、β2. The parameters are shown in table 1.
TABLE 1 Sand bank form parameters
Figure BDA0002937124430000061
(2) The flow conductivity of the rectangular sand bank is calculated by the following method:
firstly, the proppants are in prismatic accumulation distribution in the cracks, the distance between the proppants in adjacent layers can be calculated to be 0.98mm based on the spatial solid geometry theory, and then the number n of the sand-paving layers in different crack width directions can be calculated.
Secondly, as shown in figure 3, the total number (N) of the propping agents in the rectangular sand bank and the number (N) of the propping agents on the wall surface of the sand bank are respectively calculated according to formulasf) Number of proppant in sand bank (N)i)。
And thirdly, calculating the total porosity phi of the rectangular sand bank through a formula based on the definition of the physical meaning of the porosity.
And fourthly, calculating the permeability K of the rectangular sand bank in the crack through a formula based on a Kozeny model.
Fifthly, calculating the flow conductivity F of the rectangular sand bank in the crackA。
(3) Calculating to obtain the flow conductivity F of the triangular sand bank by a fitting formulaB。
(4) And correcting the sand bank flow conductivity data through the flow conductivity experiment related data.
(5) And calculating seepage resistance of the rectangular sand bank and the triangular sand bank of the single crack based on Darcy's law. As shown in FIG. 4, the total seepage resistance R of the hydraulic fracture and the natural fracture in an interaction state is calculated by a hydroelectric similarity principle.
(6) Calculating the flow conductivity F of the interactive sand-filled fracture formed by the intersection of the hydraulic fracture and the natural fractureRThe calculation results are shown in Table 2.
TABLE 2 calculation results
Figure BDA0002937124430000062
Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention.

Claims (3)

1. The interactive sand-filled fracture conductivity calculation method for intersection of the hydraulic fracture and the natural fracture sequentially comprises the following steps of:
(1) the interactive sand filling crack is composed of a hydraulic crack, a natural crack 1 and a natural crack 2, an outlet of the hydraulic crack is connected with inlets of the two natural cracks, the hydraulic crack and the natural cracks are vertical to each other, the shapes of the hydraulic crack and the sand bank in the natural cracks are simplified into a cuboid, and a common triangular prism is arranged on the cuboid, so that the section of the shape of the sand bank in the crack is a rectangle, a common triangle is arranged on the rectangle, and the opposite angle of the common triangle is a slope angle; obtaining related characteristic parameters: the balance height of the sand bank in the hydraulic fracture and the natural fracture is H; width W of sand bank in hydraulic fracturehThe width of the sand bank in the natural crack 1 and the natural crack 2 is W respectivelyn1、Wn2(ii) a The length of the hydraulic fracture sand bank comprises the length L of a rectangular sand bankhAAnd the length L of the triangular sand bankhBThe length of the natural crack 1 sand bank comprises the length L of a rectangular sand banknA1And the length L of the triangular sand banknB1And the length of the natural crack 2 sand bank comprises the length L of a rectangular sand banknA2And the length L of the triangular sand banknB2(ii) a The slope angle of the sand bank in the hydraulic fracture is alpha, and the slope angles of the sand bank in the natural fracture 1 and the natural fracture 2 are beta respectively1、β2；
(2) Calculating the flow conductivity of the rectangular sand bank, wherein the process is as follows:
calculating the number n of sand layers in the width direction of the crack:
Figure FDA0002937124420000011
in the formula: r ispIs the proppant radius, m;
w is the width of sand bank, W is W in hydraulic fracturehW in natural fracture 1 ═ Wn1W in natural fracture 2 ═ Wn2，m；HpThe distance m between adjacent layers of proppants in the sand bank under the condition that the proppants are distributed in a prismatic shape;
② the total amount N of the proppant in the rectangular sand bank comprises the amount N of the proppant on the wall surface of the sand bankfNumber of proppant N in sand banki：
Figure FDA0002937124420000012
Figure FDA0002937124420000013
Ni＝N-Nf
In the formula: h is the sand bank balance height m;
l is the length of the sand bank, and when the flow conductivity of the rectangular sand bank is calculated, L is equal to L in the hydraulic fracturehAIn natural fracture 1, L is LnA1L ═ L in natural fracture 2nA2，m；
C1And C2Is constant, when n is 3i-2, C1＝2i-2，C20; when n is 3i-1, C1＝2i-1，C21 is ═ 1; when n is 3i, C1＝2i，C21, wherein i is 1, 2, 3 …;
and thirdly, calculating the total porosity phi of the rectangular sand bank:
Figure FDA0002937124420000014
and fourthly, regarding the sand levee formed by stacking the propping agents as a capillary model, and calculating the permeability K of the rectangular sand levee in the crack according to the following formula:
Figure FDA0002937124420000021
in the formula: tau is the capillary tortuosity and takes a value of 1.5;
r is the aperture radius of the rectangular sand bank, m;
calculating the flow conductivity of the rectangular sand bank:
Figure FDA0002937124420000022
in the formula: fAIs the flow conductivity of a rectangular sand bank, mu m2·m；
(3) Calculating the flow conductivity of the triangular sand bank:
Figure FDA0002937124420000023
in the formula: fBIs the flow conductivity of a triangular sand bank, mu m2·m；
L is the length of the sand bank, and when the flow conductivity of the triangular sand bank is calculated, L is equal to L in the hydraulic fracturehBIn natural fracture 1, L is LnB1L ═ L in natural fracture 2nB2，m；
C5The proportional coefficient is 0.5;
x is a slope angle, X in the hydraulic fracture is alpha, and X in the natural fracture 1 is beta1X ═ β in natural fracture 22，°；
(4) And (3) correcting a sand bank flow conductivity formula:
Figure FDA0002937124420000024
in the formula: fcAThe flow conductivity of the rectangular sand bank is adjusted to be in the micron range under the condition of closed pressure2·m；
FcBIn order to correct the flow conductivity of the triangular sand bank under the condition of closed pressure, the diameter is mum2·m；
C6Is a correction factor;
(5) in the porous medium flow, the pressure difference is regarded as a voltage difference, the fluid flow is regarded as a current, and the seepage resistance is equivalent to resistance R1、R2Is seepage resistance of a triangular sand bank and a rectangular sand bank in the hydraulic fracture R3、R4Is the seepage resistance of a rectangular sand bank and a triangular sand bank in a natural crack 1, R5、R6The seepage resistance of the rectangular sand bank and the triangular sand bank in the natural crack 2 is determined as series connection by regarding the seepage between the rectangular sand bank and the triangular sand bank on the same crack, and the seepage between two natural cracks is determined as parallel connection by calculating the seepage resistance of the sand bank:
Figure FDA0002937124420000025
in the formula: rAIs the seepage resistance of the rectangular sand bank and the R in the hydraulic fractureA＝R2R in natural fracture 1A＝R3R in natural fracture 2A＝R5，mPa·s/(μm2·m)；
RBIs the seepage resistance of the triangular sand bank and the R in the hydraulic fractureB＝R1R in natural fracture 1B＝R4R in natural fracture 2B＝R6，mPa·s/(μm2·m)；
Mu is the fracturing fluid viscosity, mPa · s;
LAis the length of the rectangular sand bank and the hydraulic fracture middle LA＝LhAL in Natural fracture 1A＝LnA1L in Natural crack 2A＝LnA2，m；
LBIs the length of the triangular sand bank and the hydraulic fracture middle LB＝LhBL in Natural fracture 1B＝LnB1L in Natural crack 2B＝LnB2，m；
The total seepage resistance R in the interaction state of the hydraulic fracture and the natural fracture is calculated as follows:
Figure FDA0002937124420000031
in the formula: r is the total seepage resistance of the interactive sand-filled fracture in the interactive state of the hydraulic fracture and the natural fracture, and mPa & s/(mum)2·m)；
(6) Calculating the flow conductivity F of the interactive sand-filled fracture intersected by the hydraulic fracture and the natural fractureR：
Figure FDA0002937124420000032
2. The method for calculating the conductivity of an alternate sand-filled fracture wherein a hydraulic fracture intersects a natural fracture according to claim 1, wherein in step (2), the rectangular sand bank pore radius r is calculated as follows:
Figure FDA0002937124420000033
in the formula: r is1The radius of the pore on the wall surface of the sand bank is m;
r2the radius of the inner hole of the sand bank is m;
Figure FDA0002937124420000034
Figure FDA0002937124420000035
in the formula: n is a radical of1The number of the sand wall surface pores is;
N2the number of the inner pores of the sand bank;
sand bank wall surface pore number N1And the number N of inner pores of the sand bank2The calculation is as follows:
Figure FDA0002937124420000036
Figure FDA0002937124420000037
in the formula: when n is 3i-2, C3＝0，C42 i-2; when n is 3i-1, C3＝1，C42 i-2; when n is 3i, C3＝1，C4＝2i-1，i＝1、2、3…。
3. The method for calculating the conductivity of an alternate sand-filled fracture wherein a hydraulic fracture intersects a natural fracture in accordance with claim 1, wherein in step (4), the correction factor C6The calculation is as follows:
Figure FDA0002937124420000041
in the formula: sigmapThe compressive strength of the proppant particles is MPa;
Pcthe reservoir fracture closure pressure is MPa;
rpis the proppant radius, m;
r20/40radius of the proppant of 20/40 mesh, m.
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