CN110984973A - Determination method for single-well controlled reserve of fracture-cave carbonate gas reservoir - Google Patents

Determination method for single-well controlled reserve of fracture-cave carbonate gas reservoir Download PDF

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CN110984973A
CN110984973A CN201911199219.8A CN201911199219A CN110984973A CN 110984973 A CN110984973 A CN 110984973A CN 201911199219 A CN201911199219 A CN 201911199219A CN 110984973 A CN110984973 A CN 110984973A
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fracture
crack
dimensionless
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karst cave
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叶海峰
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China National Petroleum Corp
CNPC Chuanqing Drilling Engineering Co Ltd
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    • E21—EARTH DRILLING; MINING
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Abstract

The invention relates to a single-well controlled reserve evaluation method of a large-scale fracture-cave carbonate gas reservoir, which comprises the following steps of 1, establishing a well testing model according to the combination relation of a fracture, a karst cave and a shaft of the large-scale fracture-cave carbonate gas reservoir and the measurement parameters of the fracture, the karst cave and the shaft; 2. performing Laplace transformation on the well testing model and solving to obtain a bottom hole pressure solution function in a Laplace space, then programming and obtaining a real space bottom hole pressure solution function through a numerical inversion technology, and simultaneously programming to obtain theoretical bottom hole pressure data and drawing a theoretical curve graph; 3. fitting the real space bottom hole pressure solution function and the actually measured bottom hole pressure data on a theoretical curve graph to obtain related data; 4. and (3) fitting the related data obtained in the step (3) by using a well testing model to obtain the volumes of the two karst caves and the scales of the two cracks, and obtaining the single-well control reserve by using a volume method. The invention can more accurately carry out the reserve prediction calculation evaluation in the initial stage of the gas reservoir.

Description

Determination method for single-well controlled reserve of fracture-cave carbonate gas reservoir
Technical Field
The invention belongs to the technical field of oil-gas exploration and development, and particularly relates to a method for determining the single-well control reserve of a large-scale fracture-cavity carbonate gas reservoir.
Background
The difficulty of controlling the reserve evaluation aiming at the single well of the large-scale fracture-cave type carbonate rock gas reservoir lies in the mathematical description of the large-scale fracture-cave type carbonate rock gas reservoir model and the calculation method of the reserve. For the description of the fracture-cavity type carbonate oil and gas reservoir model, scholars at home and abroad make a great deal of research, and the flow problem in the complex multi-scale fracture-cavity type carbonate oil and gas reservoir can not be solved by establishing a dual-medium, triple-medium and multi-medium well testing model which is based on the assumption of a continuous homogeneous seepage field. Mathematical models of different fracture-cave structures are established on the large-scale fracture-cave type oil and gas reservoir well testing problem, such as a single large solution cavity model when a well drilling is carried out and a multi-fracture-cave unit model when the well drilling is carried out. However, a carbonate gas reservoir model with parallel connected slots and holes is not established, and the description of a fluid exchange mechanism among different media and the flowing rule of fluid in the media is not perfect. On the other hand, reasonable evaluation of the reserves of the fracture-cavity carbonate rock gas reservoir is the key for effective development of the fracture-cavity carbonate rock gas reservoir, but due to the fact that the discontinuity and the fluid flow mechanism of a large-scale fracture-cavity reservoir are greatly different from those of a relatively homogeneous sandstone reservoir, the method for evaluating the reserves of similar sandstone has many problems. At present, there are 2 main calculation methods, one is a volume method: the single-well geological reserve of the research area is estimated based on geological modeling, the modeling process is complex and difficult, and more test data are needed. The second method is a material balance method: a quantity of fluid is produced, the average formation pressure before and after production is measured, and then material balance calculations are performed based on known system PVT characteristics, which method does not take into account the changing processes and complex reservoir internal structures. In addition, the method for calculating the dynamic reserves of the single-well gas reservoir also comprises an elastic two-phase method, a pressure recovery method and the like, and has the limitations that: when the yield of the gas well is overlarge, the gas supply energy of the gas reservoir is insufficient, and the condition that the calculation result is smaller occurs. The pressure recovery method has certain randomness in the slope due to the selection of the artificial straight line segment, so that certain errors exist in the single-well reserve calculation result.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a method for determining the single-well control reserve of a fracture-cavity type carbonate gas reservoir.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a determination method for controlling reserves of a single well of a fracture-cave carbonate gas reservoir comprises the following steps:
the method comprises the following steps: setting a fracture-cavity type carbonate rock gas reservoir to have a crack 1, a crack 2, a karst cave 1 and a karst cave 2, wherein the crack 1 is intersected with the crack 2; under the set condition, a shaft is arranged at the intersection of the crack 1 and the crack 2, the karst cave 1 is communicated with the bottom end of the shaft through the crack 1, and the karst cave 2 is communicated with the bottom end of the shaft through the crack 2, so that a well testing model is established;
step two: performing Laplace transformation on the well testing model and solving to obtain a bottom hole pressure solution function in a Laplace space, then programming in matlab, obtaining a real space bottom hole pressure solution function through a Stehfest numerical inversion technology, and simultaneously programming in matlab to obtain theoretical bottom hole pressure data and drawing a theoretical curve graph;
step three: fitting the real space bottom hole pressure solution function and the measured bottom hole pressure data on a theoretical curve graph to obtain related data, wherein the related data comprise a passing performance force parameter of fluid in a crack 1 and a karst cave 1, a passing performance force parameter of fluid in a crack 2 and a karst cave 2, a shaft storage coefficient, a channeling coefficient when the karst cave 1 supplies fluid to the crack 1, a channeling coefficient when the karst cave 2 supplies fluid to the crack 2, a fracture storage capacity ratio, a crack 1 length, a crack 1 cross-sectional area, a crack 2 length, a crack 2 cross-sectional area, a karst cave 1 volume and a parameter karst cave 2 volume parameter;
step four: and (3) fitting the related data obtained in the step (3) by adopting a well testing model to obtain the volumes of the two karst caves and the scales of the two cracks, and obtaining the single-well controlled reserve by adopting a volume method.
The well testing model established in the first step is as follows:
Figure BDA0002295444860000031
wherein the content of the first and second substances,
position coordinates of dimensionless fracture end points
Figure BDA0002295444860000032
Dimensionless pressure
Figure BDA0002295444860000033
Storage capacity ratio
Figure BDA0002295444860000034
Dimensionless time
Figure BDA0002295444860000035
Dimensionless wellbore reservoir coefficient
Figure BDA0002295444860000036
Dimensionless fracture cross-sectional area
Figure BDA0002295444860000041
Dimensionless fracture cross-sectional area
Figure BDA0002295444860000042
Dimensionless cavern volume
Figure BDA0002295444860000043
Dimensionless cavern volume
Figure BDA0002295444860000044
Coefficient of proportionality between permeability and cross-sectional area between cracks
Figure BDA0002295444860000045
Dimensionless actual length of fractures f1, f2 in the reservoir
Figure BDA0002295444860000046
In formula (1): k is a radical off1、kf2Represents the permeability, mD, of the fracture systems f1, f 2; psiiRepresents the original pseudo-pressure of the gas reservoir, MPa2/mPa·s；ψjShows the gas pseudo pressure (j ═ f1, f2, v1, v2, w respectively show fracture f1,. fracture f2, karst cave 1, karst cave 2, and bottom hole), and MPa2mPa.s; q represents the surface yield of a gas well (P0.101 MPa, T293.15K), 104m3D; t represents the temperature of the gas reservoir, K; mu.sgiRepresents the original viscosity of the gas, mPa · s; cjA compression coefficient of gas (j ═ f1, f2, v1, v2 respectively represent fracture f1, fracture f2, cavern 1, cavern 2), 1/MPa; phi is ajPorosity (j ═ f1, f2, v1, v2 indicate a crack f1, a crack f2, a karst cave 1, and a karst cave 2, respectively); l isf1、Lf2Representing the actual length of the fractures f1, f2 in the reservoir, m; x represents the distance in the horizontal direction on the numerical axis, m; r iswRepresents the radius of the wellbore, m; a. thef1、Af2The cross-sectional areas of the slits f1 and f2, m2；V1、V2Denotes the volume of the caverns 1, 2, m3(ii) a t represents time, h; c represents a wellbore storage coefficient, MPa/m3；R1、R2Respectively represents the radius of the karst cave 1 and the radius of the karst cave 2, and m; k is a radical of*Expressing relative ratio parameters of permeability and fracture cross-sectional area of two fracture systems; psijDDimensionless pseudo-pressures (j ═ f1, f2, v1, v2, w indicate fracture f1, fracture f2, cavern 1, cavern 2, wellbore, respectively); l isf1D、Lf2DRepresenting dimensionless actual lengths of fractures f1, f2, respectively, in the reservoir; x is the number off1D、xf2DThe dimensionless lengths of the slits f1, f2 projected in the horizontal direction are shown, respectively; a. thef1DRepresents the cross-sectional area of dimensionless fracture f 1; v1DRepresents dimensionless cavern 1 volume; a. thef2DRepresents the cross-sectional area of dimensionless fracture f 2; v2DRepresents dimensionless cavern 2 volume; t is tDDimensionless time; cDRepresenting dimensionless wellbore reservoir coefficients; omegajThe storage-solution ratios are shown (j ═ f1, f2, v1, v2 respectively show the crack f1, the crack f2, the karst cave 1, and the karst cave 2); r1D、R2DRespectively, the dimensionless radii of the caverns 1, 2.
And in the second step, the model after the Laplace transform is carried out on the well testing model is as follows:
Figure BDA0002295444860000051
in the formula (2), the reaction mixture is,
Figure BDA0002295444860000052
is psif1D、ψf2D、ψv1D、ψv2D、ψwDThe solution in Laplace, s is the Laplace variable.
Further, solving the equation (2) to obtain a bottom hole pressure expression in a laplace space as follows:
Figure BDA0002295444860000061
in the second step, the bottom hole pressure solution function psi in the real spacewD(tD) Obtained by the following stepfest numerical inversion technique:
Figure BDA0002295444860000062
in the formula (2), N is an even number and ranges from 8 to 16.
In the fourth step, the expression of the seam hole volume method corresponding to the model is as follows:
N＝(V1+V2+Af1Lf1+Af2Lf2)/Bg。
the invention has the advantages that:
1. according to reservoir characteristics of a large-scale fracture-cave carbonate gas reservoir in a research area, the method has limitations in the evaluation method for controlling reserves of a single well of the gas reservoir, a physical model of a fracture-cave parallel structure is established on the basis of dividing a reservoir fracture-cave connecting structure, a bilinear seepage relational expression is used, geometric parameters of a fracture and the radius of a karst cave are introduced, parameters of the permeability of two fracture systems and related ratios of fracture cross-sectional areas are considered, a mathematical model of the carbonate gas reservoir seepage of the large-scale fracture-cave parallel structure is established, and under the condition of fixed-yield production, the applicability and the accuracy of the model are verified through fitting calculation analysis with on-site actual production data, so that the control reserves of the single well can be determined more accurately.
2. The reservoir geological characteristics and the fracture-cavity structure of the large-scale fracture-cavity carbonate gas reservoir are comprehensively considered, the large-scale fracture-cavity carbonate gas reservoir well testing mathematical model is established, the well testing model is used for well testing explanation, and the effectiveness and the applicability of the model are verified. Finally, by carrying out dynamic control reserve check on a single well, the karst cave volume method disclosed by the invention is tightly combined with the characteristics of the reservoirs, and can meet the requirement of evaluating the reserve scale of the large-scale fracture-cave type gas reservoir in the initial stage.
3. The invention establishes a well testing interpretation model of the large-scale fracture-cavity gas reservoir, the model is simpler than a numerical simulation discrete model, the solution is convenient, an analytic solution can be given in the Laplace space, and the analytic solution does not relate to the calculation of a complex function.
4. Compared with other traditional single-well reserves calculation methods, the reserves evaluation method is more suitable for large-scale fracture-cavity carbonate gas reservoirs.
Drawings
FIG. 1 is a flow chart of the present invention;
FIG. 2 is a diagram showing the combination of fractures, karst caves and well bores of the fracture-cavity structure model of the present invention;
FIG. 3 is a simplified schematic diagram of the model created after horizontal projection of the cracks f1 and f2 to f1 and f2 in FIG. 2;
FIG. 4 is a typical graph of the mathematical model of the present invention;
FIG. 5 is a graph of the effect of the invention on fitting a curve to an example well;
FIG. 6 is a graph of the effect of the invention on fitting a curve to an example well by Saphir software.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and therefore are only examples, and the protection scope of the present invention is not limited thereby.
As shown in figure 1, the invention discloses a method for determining the single-well control reserve of a fracture-cavity type carbonate gas reservoir, which is characterized in that the carbonate gas reservoir is described by earthquake display, coring test and three-dimensional geological carving in a research area, and the reservoir type is determined to be a fracture-karst-cavity type by means of on-site information, a karst-cavity is a main reservoir space, a fracture is a flow channel and a secondary reservoir space, the mobility of fluid outside the karst-cavity is poor, the fracture is connected with the karst-cavity in a coupling manner, two large karst-cavities are connected through two intersected fractures according to the knowledge of the reservoir, a well is drilled at the intersection of the two fractures, and the fluid respectively flows through the fracture from the two karst-cavities and finally flows to a well bore, so that a large-scale fracture-cavity type carbonate gas reservoir well test model is established. The method specifically comprises the following steps:
the method comprises the following steps: setting a fracture-cavity type carbonate rock gas reservoir to have a crack 1, a crack 2, a karst cave 1 and a karst cave 2, wherein the crack 1 is intersected with the crack 2; under the set condition, the shaft is opened at the intersection of the crack 1 and the crack 2, the karst cave 1 is communicated with the bottom end of the shaft through the crack 1, and the karst cave 2 is communicated with the bottom end of the shaft through the crack 2, so that a well testing model is established, as shown in fig. 2 and 3.
In addition, the physical model corresponding to the well testing model is assumed to be:
(1) the gas well is produced with fixed production, the shaft is positioned at the intersection of the crack f1 and the crack f2, and the pressure distribution in the karst cave and the crack is uniform before the well is opened and produced;
(2) the exploitation mode of the gas reservoir is depletion exploitation;
(3) the fluid is a single phase, and the reservoir storage space is a karst cave and a crack;
(4) the karst cave 1, the karst cave 2, the crack f1, the crack f2 and the fluid are all slightly compressible, and the compression coefficient is constant;
(5) the karst cave 1 and the karst cave 2 are not filled, and the karst cave is always regarded as an equipotential body (the pressure in the karst cave is equal everywhere);
(6) neglecting the influence of gravity, not considering the skin effect, and considering the well bore storage effect;
(7) supplying gas to the shaft at the same time from the crack f1 and the crack f2, wherein the flow of fluid in the crack meets Darcy's law, the karst cave 1 supplies gas to the crack f1, and the karst cave 2 supplies gas to the crack f 2;
(8) consider the length, cross-sectional area, porosity, and permeability of the crack f1, crack f 2;
(9) the karst cave and crack boundaries are impervious boundaries.
In this step, the well testing model established is:
Figure BDA0002295444860000091
wherein the content of the first and second substances,
position coordinates of dimensionless fracture end points
Figure BDA0002295444860000092
Dimensionless pressure
Figure BDA0002295444860000093
Storage capacity ratio
Figure BDA0002295444860000094
Dimensionless time
Figure BDA0002295444860000095
Dimensionless wellbore reservoir coefficient
Figure BDA0002295444860000096
Dimensionless fracture cross-sectional area
Figure BDA0002295444860000101
Dimensionless fracture cross-sectional area
Figure BDA0002295444860000102
Dimensionless cavern volume
Figure BDA0002295444860000103
Dimensionless cavern volume
Figure BDA0002295444860000104
Coefficient of proportionality between permeability and cross-sectional area between cracks
Figure BDA0002295444860000105
Dimensionless actual length of fractures f1, f2 in the reservoir
Figure BDA0002295444860000106
In formula (1): k is a radical off1、kf2Represents the permeability, mD, of the fracture systems f1, f 2; psiiRepresents the original pseudo-pressure of the gas reservoir, MPa2/mPa·s；ψjShows the gas pseudo pressure (j ═ f1, f2, v1, v2, w respectively show fracture f1,. fracture f2, karst cave 1, karst cave 2, and bottom hole), and MPa2mPa.s; q represents the surface yield of a gas well (P0.101 MPa, T293.15K), 104m3D; t represents the temperature of the gas reservoir, K; mu.sgiRepresents the original viscosity of the gas, mPa · s; cjA compression coefficient of gas (j ═ f1, f2, v1, v2 respectively represent fracture f1, fracture f2, cavern 1, cavern 2), 1/MPa; phi is ajPorosity (j ═ f1, f2, v1, v2 indicate a crack f1, a crack f2, a karst cave 1, and a karst cave 2, respectively); l isf1、Lf2Representing the actual length of the fractures f1, f2 in the reservoir, m; x represents the distance in the horizontal direction on the numerical axis, m; r iswRepresents the radius of the wellbore, m; a. thef1、Af2The cross-sectional areas of the slits f1 and f2, m2；V1、V2Denotes the volume of the caverns 1, 2, m3(ii) a t represents time, h; c represents a wellbore storage coefficient, MPa/m3；R1、R2Respectively represents the radius of the karst cave 1 and the radius of the karst cave 2, and m; k is a radical of*Expressing relative ratio parameters of permeability and fracture cross-sectional area of two fracture systems; psijDDimensionless pseudo-pressures (j ═ f1, f2, v1, v2, w indicate fracture f1, fracture f2, cavern 1, cavern 2, wellbore, respectively); l isf1D、Lf2DRepresenting dimensionless actual lengths of fractures f1, f2, respectively, in the reservoir; x is the number off1D、xf2DThe dimensionless lengths of the slits f1, f2 projected in the horizontal direction are shown, respectively; a. thef1DRepresents the cross-sectional area of dimensionless fracture f 1; v1DRepresents dimensionless cavern 1 volume; a. thef2DRepresents the cross-sectional area of dimensionless fracture f 2; v2DRepresents dimensionless cavern 2 volume; t is tDDimensionless time; cDRepresenting dimensionless wellbore reservoir coefficients; omegajThe storage-solution ratios are shown (j ═ f1, f2, v1, v2 respectively show the crack f1, the crack f2, the karst cave 1, and the karst cave 2); r1D、R2DRespectively, the dimensionless radii of the caverns 1, 2.
Step two: and performing Laplace transformation on the well testing model and solving to obtain a bottom hole pressure solution function in a Laplace space, programming in matlab, obtaining a real space bottom hole pressure solution function through a Stehfest numerical inversion technology, programming in matlab to obtain theoretical bottom hole pressure data, and drawing a theoretical curve graph.
In this step, the model after the test well model is subjected to laplace transform is:
Figure BDA0002295444860000111
in the formula (2), the reaction mixture is,
Figure BDA0002295444860000112
is psif1D、ψf2D、ψv1D、ψv2D、ψwDThe solution in Laplace, s is the Laplace variable.
Further, solving the equation (2) to obtain a bottom hole pressure expression in a laplace space as follows:
Figure BDA0002295444860000121
further, the real space bottom hole pressure solution function psiwD(tD) Obtained by the following stepfest numerical inversion technique:
Figure BDA0002295444860000122
in the formula (4), N is an even number and ranges from 8 to 16.
After the bottom hole pressure solution function in the Laplace space is obtained in the step, theoretical bottom hole pressure data is obtained through programming in matlab, and a theoretical curve graph is drawn, wherein the theoretical curve graph is shown in fig. 4.
Step three: fitting is carried out on a theoretical curve diagram by utilizing a real space bottom hole pressure solution function and actually measured bottom hole pressure data to obtain related data, wherein the related data comprise a passing performance force parameter of fluid in a crack 1 and a karst cave 1, a passing performance force parameter of fluid in a crack 2 and a karst cave 2, a shaft storage coefficient, a channeling coefficient when the karst cave 1 supplies fluid to the crack 1, a channeling coefficient when the karst cave 2 supplies fluid to the crack 2, a fracture storage capacity ratio, a crack 1 length, a crack 1 cross-sectional area, a crack 2 length, a crack 2 cross-sectional area, a karst cave 1 volume and a parameter karst cave 2 volume parameter.
Step four: and (3) fitting the related data obtained in the step (3) by adopting a well testing model to obtain the volumes of the two karst caves and the scales of the two cracks, and obtaining the single-well controlled reserve by adopting a volume method. Specifically, the expression of the fracture-cavity volume method corresponding to the model is as follows:
N＝(V1+V2+Af1Lf1+Af2Lf2)/Bg。
the invention is illustrated in the following examples, an S4 well of a No. I fracture zone lower disc in a Tarim basin tower is selected, the earthquake shows 'beaded' strong reflection, and the east-west earthquake section is a strip-shaped strong reflection string; coring to show the development of a seam hole, and the opening degree is higher; intercrystalline pores develop, and local intercrystalline pores are filled with argillaceous substances; loss of 6000m in target interval of drilling well3And 5.48m of air is discharged. And the production pressure appears the phenomenon that the well is opened and closed suddenly, the surrounding reservoirs are displayed, the well opening pressure is reduced quickly, the reservoir is not communicated with the bottom of the well and is connected with the karst cave through cracks. Based on the above judgment, the well reservoir type conforms to the basic characteristics of the physical model, and the basic parameters are shown in table 1.
TABLE 1S 4 well basic parameters Table
Figure BDA0002295444860000131
The actual measurement time pressure data of the sample well is fitted by using a well testing interpretation model of the large-scale fracture-cavity type carbonate rock gas reservoir, the obtained main interpretation parameter data are shown in the table 2, and fig. 5 is a curve effect graph fitted to the sample well by the method. FIG. 6 is a graph of the effect of fitting a curve to an example well using the Saphir software.
Table 2 interpretation parameter results comparison table
Figure BDA0002295444860000132
Figure BDA0002295444860000141
Fitting actual well testing information by adopting a well testing interpretation model of the large-scale fracture-cave carbonate gas reservoir to obtain the volume of a large karst cave and the scale of a fracture system, further providing a reserve calculation formula by using a volume method (the reserve calculation only considers the reserves in the fractures and the karst cave, and does not consider matrix reserves), and establishing a large-scale fracture-cave carbonate gas reservoir reserve evaluation method. The calculation method is shown in table 3, and the comparison of the calculation results of different calculation methods is shown in table 4.
TABLE 3 calculation method of slot reserves
Figure BDA0002295444860000142
Note: v1，V2Represents the volume (m) of a large cavern3)；Af1，Af2Represents the cross-sectional area (m) of the fracture system2)；Lf1，Lf2Represents the length (m) of the fracture system or the filled section; b isgRepresents the volume coefficient (m)3/m3)；
TABLE 4 comparison table of calculation results of different single well reserves
Figure BDA0002295444860000143
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims (6)

1. A determination method for controlling reserves of a single well of a fracture-cave carbonate gas reservoir comprises the following steps:
the method comprises the following steps: setting a fracture-cavity type carbonate rock gas reservoir to have a crack 1, a crack 2, a karst cave 1 and a karst cave 2, wherein the crack 1 is intersected with the crack 2; under the set condition, a shaft is arranged at the intersection of the crack 1 and the crack 2, the karst cave 1 is communicated with the bottom end of the shaft through the crack 1, and the karst cave 2 is communicated with the bottom end of the shaft through the crack 2, so that a well testing model is established;
step two: performing Laplace transformation on the well testing model and solving to obtain a bottom hole pressure solution function in a Laplace space, then programming in matlab, obtaining a real space bottom hole pressure solution function through a Stehfest numerical inversion technology, and simultaneously programming in matlab to obtain theoretical bottom hole pressure data and drawing a theoretical curve graph;
step three: fitting the real space bottom hole pressure solution function and the measured bottom hole pressure data on a theoretical curve graph to obtain related data, wherein the related data comprise a passing performance force parameter of fluid in a crack 1 and a karst cave 1, a passing performance force parameter of fluid in a crack 2 and a karst cave 2, a shaft storage coefficient, a channeling coefficient when the karst cave 1 supplies fluid to the crack 1, a channeling coefficient when the karst cave 2 supplies fluid to the crack 2, a fracture storage capacity ratio, a crack 1 length, a crack 1 cross-sectional area, a crack 2 length, a crack 2 cross-sectional area, a karst cave 1 volume and a parameter karst cave 2 volume parameter;
step four: and (3) fitting the related data obtained in the step (3) by adopting a well testing model to obtain the volumes of the two karst caves and the scales of the two cracks, and obtaining the single-well controlled reserve by adopting a volume method.
2. The method for determining the single-well controlled reserve of a fracture-cave carbonate gas reservoir according to claim 1, wherein: the well testing model established in the first step is as follows:
Figure FDA0002295444850000021
wherein the content of the first and second substances,
position coordinates of dimensionless fracture end points
Figure FDA0002295444850000022
Dimensionless pressure
Figure FDA0002295444850000023
Storage capacity ratio
Figure FDA0002295444850000024
Dimensionless time
Figure FDA0002295444850000025
Dimensionless wellbore reservoir coefficient
Figure FDA0002295444850000026
Dimensionless fracture cross-sectional area
Figure FDA0002295444850000031
Dimensionless fracture cross-sectional area
Figure FDA0002295444850000032
Dimensionless cavern volume
Figure FDA0002295444850000033
Dimensionless cavern volume
Figure FDA0002295444850000034
Coefficient of proportionality between permeability and cross-sectional area between cracks
Figure FDA0002295444850000035
Dimensionless actual length of fractures f1, f2 in the reservoir
Figure FDA0002295444850000036
In formula (1): k is a radical off1、kf2Represents the permeability, mD, of the fracture systems f1, f 2; psiiRepresents the original pseudo-pressure of the gas reservoir, MPa2/mPa·s；ψjShows the gas pseudo pressure (j ═ f1, f2, v1, v2, w respectively show fracture f1,. fracture f2, karst cave 1, karst cave 2, and bottom hole), and MPa2mPa.s; q represents the surface yield of a gas well (P0.101 MPa, T293.15K), 104m3D; t represents the temperature of the gas reservoir, K; mu.sgiRepresents the original viscosity of the gas, mPa · s; cjA compression coefficient of gas (j ═ f1, f2, v1, v2 respectively represent fracture f1, fracture f2, cavern 1, cavern 2), 1/MPa; phi is ajPorosity (j ═ f1, f2, v1, v2 indicate a crack f1, a crack f2, a karst cave 1, and a karst cave 2, respectively); l isf1、Lf2Representing the actual length of the fractures f1, f2 in the reservoir, m; x represents the distance in the horizontal direction on the numerical axis, m; r iswRepresents the radius of the wellbore, m; a. thef1、Af2The cross-sectional areas of the slits f1 and f2, m2；V1、V2Denotes the volume of the caverns 1, 2, m3(ii) a t represents time, h; c represents a wellbore storage coefficient, MPa/m3；R1、R2Respectively represents the radius of the karst cave 1 and the radius of the karst cave 2, and m; k is a radical of*Expressing relative ratio parameters of permeability and fracture cross-sectional area of two fracture systems; psijDDimensionless pseudo-pressures (j ═ f1, f2, v1, v2, w indicate fracture f1, fracture f2, cavern 1, cavern 2, wellbore, respectively); l isf1D、Lf2DRepresenting dimensionless actual lengths of fractures f1, f2, respectively, in the reservoir; x is the number off1D、xf2DThe dimensionless lengths of the slits f1, f2 projected in the horizontal direction are shown, respectively; a. thef1DRepresents the cross-sectional area of dimensionless fracture f 1; v1DRepresents dimensionless cavern 1 volume; a. thef2DRepresents the cross-sectional area of dimensionless fracture f 2; v2DRepresents dimensionless cavern 2 volume; t is tDDimensionless time; cDRepresenting dimensionless wellbore reservoir coefficients; omegajThe storage-solution ratios are shown (j ═ f1, f2, v1, v2 respectively show the crack f1, the crack f2, the karst cave 1, and the karst cave 2); r1D、R2DRespectively represent dimensionless radii of the karst caves 1 and 2。
3. The method for determining the single-well controlled reserve of a fracture-cave carbonate gas reservoir according to claim 2, wherein: and in the second step, the model after the Laplace transform is carried out on the well testing model is as follows:
Figure FDA0002295444850000041
in the formula (2), the reaction mixture is,
Figure FDA0002295444850000042
is psif1D、ψf2D、ψv1D、ψv2D、ψwDThe solution in Laplace, s is the Laplace variable.
4. The method for determining the single-well controlled reserve of a fracture-cave carbonate gas reservoir according to claim 3, wherein: solving the equation (2) to obtain a bottom hole pressure expression under the Laplace space as follows:
Figure FDA0002295444850000051
。
5. the method for determining the single-well controlled reserve of a fracture-cave carbonate gas reservoir according to claim 4, wherein: in the second step, the bottom hole pressure solution function psi in the real spacewD(tD) Obtained by the following stepfest numerical inversion technique:
Figure FDA0002295444850000052
in the formula (2), N is an even number and ranges from 8 to 16.
6. The method for determining the single-well controlled reserve of a fracture-cave carbonate gas reservoir according to claim 5, wherein: in the fourth step, the expression of the seam hole volume method corresponding to the model is as follows:
N＝(V1+V2+Af1Lf1+Af2Lf2)/Bg。
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