CN111400853B - Method and device for predicting unsteady state capacity of closed boundary fractured horizontal well - Google Patents

Method and device for predicting unsteady state capacity of closed boundary fractured horizontal well Download PDF

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CN111400853B
CN111400853B CN201910003901.9A CN201910003901A CN111400853B CN 111400853 B CN111400853 B CN 111400853B CN 201910003901 A CN201910003901 A CN 201910003901A CN 111400853 B CN111400853 B CN 111400853B
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何军
范子菲
赵伦
宋珩
陈烨菲
何聪鸽
罗二辉
郝峰军
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Petrochina Co Ltd
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Abstract

The invention provides a method and a device for predicting unsteady state capacity of a closed boundary fractured horizontal well, wherein the method comprises the following steps: acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted; inputting the oil reservoir physical property, the fluid physical property, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady capacity prediction model of the closed boundary fractured horizontal well to obtain unsteady capacity corresponding to the fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters, time steps and corresponding unsteady-state capacity are obtained; and establishing a fracturing horizontal well productivity influence factor optimization chart according to the plurality of fracture parameters, the time step length and the corresponding unsteady state productivity, and screening out the optimal fracturing horizontal well fracture parameters according to the chart. According to the technical scheme, the accuracy and the efficiency of yield prediction of the fractured horizontal well are improved, and scientific guidance is provided for efficient development of the fractured horizontal well of the oil field.

Description

Method and device for predicting unsteady state capacity of closed boundary fractured horizontal well
Technical Field
The invention relates to the technical field of oil reservoir engineering in oil development, in particular to a method and a device for predicting unsteady state capacity of a closed boundary fractured horizontal well.
Background
With the continuous rising of the global oil and gas resource demand, the inferior low-grade oil and gas resource becomes an important battlefield for future oil and gas field development, the traditional vertical well development is difficult to meet the needs of economic technology, and the fractured horizontal well technology becomes an important tool for the efficient development of the oil and gas resource. The demonstration of the productivity of the fractured horizontal well is the basis for obtaining economic benefits by the horizontal well technology, and the demonstrated quality of the productivity directly influences the potential exertion of the horizontal well and the development effect of an oil field. The previous people do a lot of research and exploration on the fractured horizontal well productivity prediction method, but most of the methods are based on a steady-state method and have a large difference with the actual production situation of an oil field, and few prediction methods consider a non-steady-state method but do not consider a boundary effect, so that the method is only suitable for evaluating the initial fractured horizontal well productivity.
Therefore, the problem that the existing fractured horizontal well productivity prediction scheme is low in prediction accuracy and efficiency exists.
Disclosure of Invention
The embodiment of the invention provides a method for predicting unsteady state capacity of a closed boundary fractured horizontal well, which is used for improving the accuracy and efficiency of the prediction of the capacity of the fractured horizontal well and comprises the following steps:
acquiring oil reservoir physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted;
inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state capacity prediction model of the closed boundary fractured horizontal well to obtain unsteady state capacity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and each time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent hole diameter of the crack;
establishing a fractured horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady state productivity corresponding to each fracture parameter and time step, and screening out the optimal fractured horizontal well fracture parameters according to the fractured horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for the application of the fractured horizontal well in the oil field;
determining unsteady state productivity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil deposit physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures, wherein the unsteady state productivity comprises the following steps:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all the mirror image wells to the equivalent well, the oil deposit physical property parameters and the fluid physical property parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
The embodiment of the invention also provides a device for predicting the unsteady state capacity of the closed boundary fractured horizontal well, which is used for improving the accuracy and efficiency of the capacity prediction of the fractured horizontal well and comprises the following components:
the acquiring unit is used for acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of the fractured horizontal well to be predicted;
the fracture parameter and productivity determining unit is used for inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state productivity prediction model of the closed boundary fractured horizontal well to obtain unsteady state productivity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and each time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent hole diameter of the crack;
the prediction unit is used for establishing a fracturing horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady state productivity corresponding to each fracture parameter and time step, and screening out the optimal fracturing horizontal well fracture parameters according to the fracturing horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for oilfield field fractured horizontal well application;
determining unsteady state productivity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil reservoir physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures, and the method comprises the following steps:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all the mirror image wells to the equivalent well, the oil deposit physical property parameters and the fluid physical property parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
The embodiment of the invention also provides computer equipment which comprises a memory, a processor and a computer program which is stored on the memory and can be run on the processor, wherein the processor executes the method for predicting the unsteady capacity of the closed boundary fractured horizontal well.
The embodiment of the invention also provides a computer readable storage medium, which stores a computer program for executing the method for predicting the unsteady state capacity of the closed boundary fractured horizontal well.
The technical scheme provided by the embodiment of the invention comprises the following steps: firstly, acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted; secondly, inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established closed boundary fracturing horizontal well unsteady state productivity prediction model to obtain unsteady state productivity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and each time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent well diameter of the fracture; and then, establishing a fractured horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady capacity corresponding to each fracture parameter and time step, and screening out the optimal fractured horizontal well fracture parameters according to the fractured horizontal well productivity influence factor optimization chart.
In conclusion, the technical scheme provided by the embodiment of the invention improves the accuracy and efficiency of the yield prediction of the fractured horizontal well, and provides scientific guidance for the efficient development of the fractured horizontal well in the oil field.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:
FIG. 1 is a schematic flow chart of a method for predicting unsteady state capacity of a closed boundary fractured horizontal well in the embodiment of the invention;
FIG. 2 is a schematic view of an equivalent hole diameter of a fractured horizontal well in an embodiment of the invention;
FIG. 3 is a schematic diagram of a multi-well mirror inversion of a rectangular closed boundary formation in an embodiment of the present invention;
FIG. 4 is a schematic diagram of a rectangular closed boundary stratum mirror inversion subdivision unit in the embodiment of the invention;
FIG. 5 is a schematic flow chart illustrating capacity prediction of a closed boundary fractured horizontal well according to an embodiment of the invention;
FIG. 6 is a comparison schematic diagram of the calculation (prediction) results of the productivity of fractured horizontal wells in the embodiment of the invention;
FIG. 7 is a fractured horizontal well production fit schematic in an embodiment of the invention;
FIG. 8 is a diagram of a plate for optimizing crack number (a plate for influence of crack number on productivity) according to an embodiment of the present invention;
FIG. 9 is a schematic illustration of a fracture yield distribution plate (individual fracture yield distribution plates) in an embodiment of the invention;
FIG. 10 is a schematic diagram of a crack length optimization plate (a plate with half crack length affecting productivity) according to an embodiment of the present invention;
FIG. 11 is a diagram of a dimensionless fracture conductivity optimization chart (a chart of the influence of dimensionless fracture conductivity on the fracture) in an embodiment of the present disclosure;
fig. 12 is a schematic structural diagram of the device for predicting the unsteady state capacity of the closed boundary fractured horizontal well in the embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the following embodiments and accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
The inventor finds that: some scholars in the prior art perform a great deal of research and exploration on a fractured horizontal well productivity evaluation (prediction) model, but most of the scholars are based on a steady-state method, the difference from the actual production situation of an oil field is large, and a few models consider a non-steady-state method but do not consider a boundary effect, so that the method is only suitable for evaluating the initial fractured horizontal well productivity.
For example: some schemes disclose application potential theory and superposition principle, consider infinite diversion and limited diversion of cracks, push to productivity linear equation sets of the segmented multi-cluster fractured horizontal well, solve the capacity linear equation sets by using a numerical solving method, and analyze the influence of crack diversion capacity and half-length of cracks on the capacity of the fractured horizontal well.
For example: some schemes disclose that a fractured horizontal well productivity evaluation model is established based on a quasi-steady-state equivalent well diameter model, a fracture internal variable mass linear flow model and a potential superposition principle, and the influence of fracture parameters on the horizontal well productivity is analyzed, but the model is based on a quasi-steady-state production condition and is different from the actual condition of on-site fractured horizontal well non-steady-state production, so that the application of the method is restricted.
For example: according to some schemes, the method includes the steps that one fractured horizontal well at the center of an infinite earth stratum is considered, crude oil flows to cracks from the stratum linearly, then flows to a shaft from the cracks to meet a linear seepage rule, a flow pressure drop formula is set by combining points of the infinite earth stratum, a fractured horizontal well productivity prediction model is deduced according to a potential theory and a superposition principle, and influences of included angles between the cracks and the horizontal shaft and crack intervals on horizontal well productivity are analyzed. Although the influence of unsteady-state seepage is considered, the method is based on infinite stratum seepage, an oil drainage area of an actual fracturing horizontal well of an oil field is a limited area, and the method causes a great prediction result of the capacity of the fracturing horizontal well.
For example: some schemes disclose that on the basis of a single-fracture productivity model, interference between adjacent fractures is considered, a multi-stage fractured horizontal well productivity prediction model in the whole process from a stratum to a well bottom is established, and although the model considers the influence of a limited boundary and unsteady seepage, complicated mathematical transformation is involved in the solving process, such as Fourier integral transformation and Fredholm integral equation, so that the field application and popularization of the method are restricted.
In conclusion, the existing fractured horizontal well seepage model has the following problems: (1) Most fractured horizontal well seepage models are based on steady-state seepage, can only reflect static production characteristics of oil and gas wells under a constant pressure boundary condition, and cannot consider the influence of time dimension on oil and gas well production; secondly, the early model assumes that the stratum is an infinite stratum, and the fracture has infinite conductivity, which inevitably leads to a large calculation result of the yield of the fractured horizontal well; finally, although the unsteady state seepage and the limited fracture diversion are considered in part of models, the solving process is complex, fredholm integral processing is involved, and the application of the fractured horizontal well productivity calculation model is restricted.
Therefore, in consideration of the technical problems, the inventor provides a fracturing horizontal well unsteady state capacity prediction scheme with a closed boundary, the fractured horizontal well unsteady state capacity prediction scheme takes boundary effects into consideration, the precision and the efficiency of the fractured horizontal well unsteady state capacity prediction are improved, and scientific guidance is provided for efficient development of the fractured horizontal well in the oil field. Specifically, on the basis of a fracture equivalent caliper model, the unsteady state capacity prediction model of the fractured horizontal well with the closed boundary is established by applying the mirror image inversion and pressure drop superposition principles, and then the capacity prediction of the fractured horizontal well is carried out by using the model. The unsteady state capacity prediction model for the closed boundary fractured horizontal well, provided by the invention, has the advantages of comprehensive consideration factors, simple derivation process, high capacity prediction precision, high efficiency and strong field applicability. The unsteady state capacity prediction scheme of the closed boundary fractured horizontal well is described in detail as follows.
Fig. 1 is a schematic flow chart of a method for predicting unsteady state capacity of a closed boundary fractured horizontal well in the embodiment of the invention, and as shown in fig. 1, the method comprises the following steps:
step 101: acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted;
step 102: inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state capacity prediction model of the closed boundary fractured horizontal well to obtain unsteady state capacity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent hole diameter of the crack;
step 103: establishing a fractured horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady state productivity corresponding to each fracture parameter and time step, and screening out the optimal fractured horizontal well fracture parameters according to the fractured horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for the application of the fractured horizontal well in the oil field;
determining unsteady state productivity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil deposit physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures, wherein the unsteady state productivity comprises the following steps:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all the mirror image wells to the equivalent well, the oil deposit physical property parameters and the fluid physical property parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
The technical scheme provided by the embodiment of the invention comprises the following steps: firstly, acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted; secondly, inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established closed boundary fracturing horizontal well unsteady state productivity prediction model to obtain unsteady state productivity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent well diameter of the fracture; and then, establishing a fractured horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady capacity corresponding to each fracture parameter and time step, and screening out the optimal fractured horizontal well fracture parameters according to the fractured horizontal well productivity influence factor optimization chart.
In conclusion, the technical scheme provided by the embodiment of the invention improves the accuracy and efficiency of the yield prediction of the fractured horizontal well, and provides scientific guidance for the efficient development of the fractured horizontal well in the oil field.
During specific implementation, the optimal fracture parameter or the optimal fracture parameter combination is finally predicted, and oil field developers can perform oil field development work according to the optimal fracture parameter or the optimal fracture parameter combination, for example, fracturing is performed according to the predicted fracture parameters such as the length, the height and the width of the fracture, so that more oil can be produced, the yield prediction precision and efficiency of the fractured horizontal well are improved, and scientific guidance is provided for efficient development of the fractured horizontal well in the oil field.
The steps involved in the present invention are described in detail below.
1. Firstly, a process of establishing a closed boundary fractured horizontal well unsteady state productivity prediction model in advance is introduced.
1. First, collecting reservoir property parameters, fluid property parameters, horizontal well bore structure, fracturing parameters, and fracture parameters in historical data, in one embodiment, the reservoir property parameters may include: the method comprises the following steps of (1) obtaining the size of an oil reservoir, the thickness of the reservoir, the permeability of the reservoir, the porosity of the reservoir, the comprehensive compressibility of the reservoir and the like, wherein the size of the oil reservoir can be obtained through well testing interpretation results in the initial stage of an oil field, and the thickness of the reservoir, the permeability of the reservoir, the porosity of the reservoir and the comprehensive compressibility of the reservoir can be obtained through well testing interpretation results and core indoor tests; the fluid property parameters may include: fluid viscosity and other parameters, wherein the fluid viscosity can be obtained through a fluid laboratory test; the horizontal well body structure parameters comprise: horizontal well horizontal segment length, shaft radius, etc.; the fracturing parameters may include: the number of fracturing stages, etc.; fracture parameters may include: the fracture conductivity coefficient, the fracture length, the fracture height, the fracture width, the fracture permeability and the like, wherein the shaft radius, the fracturing section number, the fracture conductivity coefficient, the horizontal section length, the fracture height, the fracture width and the fracture permeability can be obtained through oil field fracturing evaluation data.
2. According to the obtained parameters and the relation between the obtained parameters and the corresponding unsteady state capacity, a closed boundary fractured horizontal well unsteady state capacity evaluation model is established based on the fracture equivalent well diameter and by applying a mirror image inversion and pressure drop superposition principle, and the closed boundary fractured horizontal well unsteady state capacity prediction model is established in advance by applying the mirror image inversion and pressure drop superposition principle according to the fracture equivalent well diameter. Due to the fact that the unsteady capacity prediction of time factors and the like and the prediction of the closed boundary are considered in the unsteady capacity prediction model of the closed boundary fractured horizontal well, the accuracy and the efficiency of the prediction of the unsteady capacity of the closed boundary fractured horizontal well are improved, and scientific guidance is provided for efficient development of the oilfield fractured horizontal well. In specific implementation, the establishing process of the unsteady state capacity prediction model of the closed boundary fractured horizontal well may include:
(1) Determining the equivalent hole diameter of the fracture:
(1) firstly, determining the equivalent hole diameter of a fractured vertical well fracture:
in the process of establishing the unsteady state capacity prediction model of the closed boundary fractured horizontal well, deducing an equivalent well diameter formula of the limited diversion fracture of the vertical well by using Laplace transformation and Fredholm type integral:
Figure BDA0001934693430000081
in the formula: r is wev The equivalent well diameter of the vertical well fracture is m; x is the number of f M is the half-length of the crack; c fd The fracture conductivity is dimensionless; f (C) fd ) Is a dimensionless fracture conductivity influence function;
wherein, C fd And f (C) fd ) The expression of (a) is:
Figure BDA0001934693430000082
Figure BDA0001934693430000083
in the formula, k f Is the crack permeability, w f Is the fracture width, k is the reservoir permeability, x f Is half the length of the crack, n is largeEqual to 1.
The seepage mode in the fracture of the fracturing horizontal well is similar to that of the fracturing vertical well. Seepage in the vertical well fracture is single linear flow, and flow in the horizontal well fracture is composed of two parts: a. near wellbore radial flow; b. linear flow away from the wellbore. Thus, the flow in a fractured horizontal well fracture will create an additional pressure drop near the wellbore compared to the flow in a fractured vertical well fracture, a phenomenon known as radial current crowding, the skin factor of wellbore current crowding:
Figure BDA0001934693430000084
in the formula: s. the c Is the flux skin coefficient; h is reservoir thickness, m, r w Is the radius of the horizontal wellbore; for the meanings of the other parameters, see the above description.
(2) Secondly, according to the introduction, determining the equivalent hole diameter of the fractured horizontal well fracture:
thus, the equivalent caliper of a single fracture of a fractured horizontal well can be expressed as:
Figure BDA0001934693430000085
in the formula, r we The equivalent hole diameter of a single crack of a fractured horizontal well.
In specific implementation, the assumed conditions of the unsteady state capacity prediction model of the closed boundary fractured horizontal well are as follows: the method comprises the following steps of (1) forming a rectangular enclosed stratum, wherein the thickness and permeability of a reservoir are constants; the fluid is single-phase incompressible Newtonian fluid, the viscosity is constant, and the seepage meets the flow of Darcy; the fracture is a limited diversion fracture, the horizontal shaft is an infinite diversion (the pressure drop of the horizontal shaft is small and can be ignored), and fluid enters the fracture from the matrix and then enters the horizontal shaft from the fracture; the shape of the crack is rectangular and penetrates through the whole oil layer; the parameters of each fracture may be different, and the seepage is unstable seepage.
Through the formula (5), the seepage problem of one fracturing horizontal well of the closed stratum can be converted into the seepage problem of a plurality of vertical wells of the limited stratum, as shown in FIG. 2, rwe1, rwe, rwe and rwe are equivalent well diameters of corresponding fractures. A fractured horizontal well typically has a plurality of fractured fractures rwe1, rwe, rwe, rwe representing the equivalent caliper of fracture 1,2,3,4. According to the equivalent well diameters, the equivalent well position coordinates of the fractured horizontal well fractures of the closed boundary stratum can be determined by utilizing the mathematical coordinates.
(2) Closed boundary mirror inversion:
the inventor finds that in the prior art, the model assumes that the stratum is an infinite stratum, and the fracture has infinite conductivity, so that the calculation result of the yield of the fractured horizontal well is larger, therefore, the production of a plurality of vertical wells in a rectangular stratum can be converted into the production of a plurality of wells in the infinite stratum through mirror inversion (figure 3). The gray area in the figure represents the original enclosed stratum, the well of the gray area part in the figure is defined as an equivalent well of the fracture, and other wells are mirror image wells corresponding to the equivalent well. The dotted line rectangular part represents 4 times of drainage area, and the dotted line rectangular area is infinitely expanded to the upper part, the lower part, the left part and the right part, so that the mirror inversion result of the closed stratum fractured horizontal well can be obtained. In actual calculation, infinite inversion is not needed, and only finite inversion is needed in the longitudinal direction and the transverse direction, so that a better calculation result can be obtained, and the accuracy of the fracturing horizontal well productivity prediction is improved.
Taking 4 slits as an example, taking n (n > =10, the model can obtain better convergence result) rectangles above, below, left and right dotted rectangles, the number of the rectangles is (2n + 1) ^2, and the total number of the wells is 16 ^ (2n + 1) ^2. By analyzing the action of all the wells at the equivalent well, the yield of each equivalent well, namely the yield of each fracture of the fractured horizontal well, can be obtained.
The following equation is the pressure drop produced at any point for a single well in an infinite formation, which is the basis for pressure drop stacking for multiple wells.
Figure BDA0001934693430000091
In the formula: p is a radical of formula i To the pressure of the original formationMPa; p (x, y, t) is the pressure of any point of the stratum, MPa; q is the yield, m3/d; k is reservoir permeability, μm 2 (ii) a μ is fluid viscosity, mpa.s; x, y are any point of the stratum, x 0 ,y 0 Well point coordinates (equivalent well coordinates); eta is the pressure derivative coefficient, t is time, and Ei represents the power integral function in mathematics.
In order to determine the position coordinates of each well, the rectangular area in fig. 2 is selected as the study unit, and a corresponding coordinate system is established (fig. 4). A1, B1, C1, D1 represent a straight well corresponding to fracture 1, A2, B2, C2, D2 represent a straight well corresponding to fracture 2, A3, B3, C3, D3 represent a straight well corresponding to fracture 3, and A4, B4, C4, D4 represent a straight well corresponding to fracture 4. The subdivision unit of fig. 4 (the subdivision unit has no special meaning, mainly for the following description, it is a simple dotted area in fig. 3, and the dotted area is expanded up, down, left and right according to the dotted area, so as to obtain fig. 3, and in order to eliminate the influence of the closed boundary of the gray area, it is essentially boundary inversion, a mathematical processing method) is expanded up, down, left and right, so as to obtain the result of mirror inversion of fig. 2, and the coordinates of each well in the subdivision unit of fig. 3 can be obtained as long as the coordinates of each well in the subdivision unit of fig. 2 are obtained.
Let x Ai ,x Bi ,x Ci ,x Di X-coordinate representing the equivalent well corresponding to fracture i (i =1,2,3,4) and its mapped well, which is known from the above analysis Ai ,x Bi ,x Ci ,x Di For a matrix of order (2n + 1), the x coordinate of the well corresponding to fracture i can be expressed as:
x fi ＝[x Ai x Bi x Ci x Di ]； (7)
similarly, the y-coordinate of the well corresponding to fracture i may be expressed as
y fi ＝[y Ai y Bi y Ci y Di ]； (8)
Wherein: x is the number of fi ,y fi The matrix can be regarded as formed by splicing 4 (2n + 1) step block matrixes, and the size of the matrix is (2n + 1) 4 (2n + 1);
next, coordinates of the pressure drop reference point are obtained, where the pressure drop reference point is set as A1, A2, A3, and A4 wells in the gray area in fig. 3, and the coordinates may be expressed as (x 1+ rwe1, y 1), (x 2+ rwe, y 2), (x 3+ rwe, y 3), (x 4+ rwe, y 4), in order to facilitate the following solution, the coordinates of the pressure drop reference point are expanded, and the expanded x coordinate of the pressure drop reference point may be expressed as:
x wAi ＝[x wi x wi x wi x wi ]； (9)
wherein: x is the number of wi (i =1,2,3,4) represents the x coordinate, x, of the Ai well pressure drop reference point after propagation wi A matrix of order (2n + 1), each element of the matrix being x wi +r wei ；
Similarly, the y coordinate of the expanded pressure drop reference point is:
y wAi ＝[y wi y wi y wi y wi ]； (10)
wherein: y is wi (i =1,2,3,4) represents the x-coordinate, y, of the Ai well drawdown reference point after expansion wi A matrix of order (2n + 1), each element of the matrix being y wi ；
Thus, x fi ，y fi ，x wAi ，y wAi The matrix size is (2n + 1) × 4 (2n + 1), which is convenient for matrix operation;
let r ij Representing the equivalent well j (j =1,2,3,4) and its mirror image well spacing from the equivalent well Ai (i =1,2,3,4).
Figure BDA0001934693430000111
Wherein: (x) fj -x wAi ) 2 、(y fj -y wAi ) 2 Representing the subtraction of corresponding elements of two matrices, then squaring, r ij There is a matrix of (2n + 1) × 4 (2n + 1), there are 16 such matrices combined according to subscript.
And the step (2) of closed boundary mirror image inversion realizes the distance from all mirror image wells to the equivalent well after the equivalent well position coordinates of the fracture of the horizontal well fractured by the closed boundary stratum are determined.
(3) After the distances from all the mirror image wells to the equivalent wells are determined according to the formula (11), determining the pressure drop of each mirror image well and each equivalent well at the equivalent wells according to the distances from all the mirror image wells to the equivalent wells, the oil deposit physical property parameters and the fluid physical property parameters, and determining the unsteady state capacity of the equivalent wells according to the pressure drop and the time step length are introduced as follows:
in specific implementation, the distances from all wells to 4 equivalent wells of the rectangular enclosed stratum are obtained, and then the pressure drop of each well at the equivalent wells is calculated by applying a pressure drop superposition principle.
Figure BDA0001934693430000112
r ij 2 A matrix r of representation pairs ij Is subjected to a square calculation for each element in (b),
Figure BDA0001934693430000113
representation pair matrix r ij 2 Each element in (a) is divided by 4 etat,
Figure BDA0001934693430000114
representation pair matrix
Figure BDA0001934693430000115
Each element of (a) is subjected to a power integration operation,
Figure BDA0001934693430000116
representation pair matrix
Figure BDA0001934693430000117
Is summed. Δ p ij Representing the pressure drop created at the equivalent well i by the equivalent well j and its mirror well. The implementation of this equation (12) can be seen in equation (6) above.
When the yield of each crack of the fractured horizontal well is changed, the pressure drop of each time step can be obtained by using the Du Hamei principle:
Figure BDA0001934693430000121
where t (τ) denotes the τ th time step, Δ p ij (τ) represents the pressure drop at the equivalent well i for the equivalent well j and its mirror image at the τ -th time step.
To facilitate the solution of daily fracture production per time step, let
Figure BDA0001934693430000122
Δp ij (τ)＝q j (τ)c ij (τ)； (14)
Wherein q is j Yield per fracture, c ij (τ) has no special meaning, but is an intermediate variable set for simplifying the expression form of equation (13).
Because the pressure drop of the fluid in the well bore is small and can be ignored, the pressure at the bottom of the well is equal for each equivalent well and is the bottom flowing pressure of the horizontal well. Therefore, only considering one time step, each equivalent vertical well corresponds to one pressure drop equation, and there are 4 (taking 4 fractures as an example), that is:
Figure BDA0001934693430000123
order to
Figure BDA0001934693430000124
When τ =1, the above formula is:
C 1 *Q 1 ＝P 1 ； (16)
when considering tau time steps, the productivity formula of the fractured horizontal well is as follows:
Figure BDA0001934693430000125
Q k a matrix of all equivalent well productions at the first time step; p τ Is a matrix of the bottom hole drawdowns of all the equivalent wells at the time step τ; c τ And (4) at the Tth time step, respectively acting the equivalent wells corresponding to all the cracks and the mirror image wells thereof on a matrix formed by seepage resistance of all the equivalent wells, wherein the yield is multiplied by the seepage resistance = the pressure.
C τ And at the time step tau, the equivalent well corresponding to each crack and the mirror image well thereof respectively act on a matrix formed by seepage resistance of each equivalent well.
The above formula is a fracturing horizontal well productivity solving formula for the first tau time step of a 4-crack fracturing horizontal well of a rectangular closed stratum, and the fracturing horizontal well productivity formula for any plurality of time steps of any plurality of cracks can be obtained by using the same method.
2. And secondly, introducing a prediction process of the fractured horizontal well to be predicted according to the pre-established unsteady state capacity prediction model of the closed boundary fractured horizontal well.
1. Firstly, in the step 101, the reservoir physical property parameter, the fluid physical property parameter and the horizontal well body structure parameter of the fractured horizontal well to be predicted are obtained.
2. Secondly, in step 102, as shown in fig. 5, the acquired parameters and the assumed fracture parameters are input into the pre-established unsteady capacity prediction model of the closed boundary fractured horizontal well to obtain unsteady capacity corresponding to the assumed fracture parameters, and the assumed fracture parameters and the time step are continuously modified and input into the unsteady capacity prediction model of the closed boundary fractured horizontal well until a plurality of fracture parameters and time steps and unsteady capacity corresponding to each fracture parameter and time step are obtained.
In specific implementation, the inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established model for predicting the unsteady state capacity of the closed boundary fractured horizontal well to obtain the unsteady state capacity corresponding to the assumed fracture parameter may include:
determining the equivalent hole diameter of the fractured vertical well fracture according to the fracture parameters (the formula (1) can be applied);
determining the equivalent well diameter of the fractured horizontal well fracture (the above formulas (2) - (5) can be applied) according to the equivalent well diameter of the fractured vertical well fracture and the oil reservoir physical property parameters;
determining equivalent well position coordinates (which can be directly extracted according to a coordinate system) of the fractured horizontal well fractures of the closed boundary stratum according to the equivalent well diameter of the fractured horizontal well fractures;
and determining unsteady state capacity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil reservoir physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures.
In specific implementation, as shown in fig. 5, the process is a process of applying the pre-established model for predicting the unsteady-state capacity of the closed boundary fractured horizontal well: solving the equivalent well diameter of each crack, extracting the well position coordinates of the equivalent well, and determining the unstable production capacity of the closed boundary fractured horizontal well by applying an LU decomposition method according to a power integral function, a matrix splitting and splicing function, a recursion solving function and the like which are compiled in advance. And then, subsequently modifying the crack parameters and the time step length to optimize the crack parameters until obtaining a plurality of crack parameters and time step lengths and unsteady state productivity corresponding to each crack parameter and time step length.
In an embodiment, determining the unsteady state capacity corresponding to the fracture parameter according to the equivalent well position coordinates, the oil reservoir property parameter and the fluid property parameter of the closed boundary stratum fractured horizontal well fracture may include:
determining the well position coordinates (which can be determined according to the coordinates of a mathematical method) of all mirror image wells corresponding to the fracturing equivalent wells of the closed boundary stratum according to the well position coordinates of the equivalent wells of the fracturing horizontal well of the closed boundary stratum;
determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells (the above formulas (7) - (11) can be applied);
determining the pressure drop of each mirror image well and each equivalent well at the equivalent well according to the distances from all mirror image wells to the equivalent wells, the oil deposit physical property parameters and the fluid physical property parameters (the above formulas (12) - (13) can be applied);
based on the pressure drop and the time step, the unsteady state production capacity of the equivalent well is determined (equations (14) - (17) above can be applied).
3. Finally, in the step 103, establishing a fracturing horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady capacity corresponding to each fracture parameter and time step, and screening out the optimal fracturing horizontal well fracture parameters according to the fracturing horizontal well productivity influence factor optimization chart. In one embodiment, the fracture horizontal well productivity influencing factor optimization plate may include: the number of cracks affects one or any combination of a production capacity influence plate, a yield distribution plate of each crack, a production capacity influence plate of half-length of the crack, and a crack influence plate of non-dimensional crack flow conductivity. Based on the plates, the optimal fracture parameters of the fractured horizontal well are screened out, so that the optimal fracture parameter combination suitable for the oil reservoir conditions is determined, and guidance is provided for the deployment of the fractured horizontal well of the oil field.
In addition, the optimized chart for the productivity influencing factors of the fractured horizontal well can visually display the optimal fracture parameter combination suitable for the oil reservoir conditions, and is flexible and convenient for oil field mining personnel.
Therefore, according to the technical scheme provided by the embodiment of the invention, the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established by applying the mirror inversion and the pressure drop superposition principle on the basis of the equivalent hole diameter of the crack, and the unsteady state capacity prediction model of the closed boundary fractured horizontal well is simple to solve, high in prediction precision and strong in field applicability.
The following description will be given with reference to fig. 6 to 11 for an example to illustrate how the present invention is implemented.
(1) Point source function method verification
In order to verify the model of the invention, the point source function method is used for verifying the initial productivity of the fractured horizontal well, and the basic parameters of the model are as follows in the following table 1:
table 1 basic parameters of the model
Figure BDA0001934693430000151
By comparing with a source function method, the accuracy and the reliability of the fracturing horizontal well productivity formula are analyzed. As can be seen from FIG. 6, the calculation result of the embodiment of the invention is very close to the initial yield result of the source function method no matter whether the horizontal well is fractured by a single fracture or 3 fractures, and the relative error is within 3%, which illustrates the accuracy and reliability of the model of the invention.
(2) Mine field experiment verification
And further verifying the accuracy of the productivity model of the closed boundary fracturing horizontal well by using the production dynamic data. In fig. 7, a curve with hollow dots is actual production data of a fractured horizontal well of a certain oil field, and the other curve represents a calculation (prediction) result of the model of the invention, as can be seen from fig. 7, although the actual data of the oil field has certain fluctuation, the fitting effect of the model of the invention and the actual production data is better, as can be seen from table 2 below, the coincidence rate of the calculated productivity and the actual productivity reaches more than 90%, the average error of the initial yield is 8.06%, and the average error of the accumulated yield is 5.53%. Therefore, the model has high productivity prediction precision and can be popularized and applied in oil field sites.
TABLE 2 actual and calculated yield comparison of fractured horizontal wells
Figure BDA0001934693430000152
Figure BDA0001934693430000161
(3) Fracture parameter optimization
The method is most important in optimizing design of fracture parameters of the horizontal well fractured on site in the oil field. The basic parameters of the model are as in table 1, and the fracture number optimization plate, the fracture yield distribution plate, the fracture length plate, and the fracture conductivity optimization plate established in step 103 are described below.
As can be seen from fig. 8, in the initial stage of production, the capacity of the fractured horizontal well is high, the interference among fractures is gradually enhanced along with the increase of production time, and the capacity of the horizontal well is reduced; along with the increase of the number of the cracks, the increase of the capacity of the fractured horizontal well is gradually reduced. In the fracturing process, the influence of the number of the cracks needs to be considered, but the number of the cracks is not the more, the better the number of the cracks is, but the optimal number of the cracks exists, and according to the embodiment of the invention, the optimal number of the cracks is 4. Meanwhile, by combining the crack yield distribution chart of fig. 9, it can be known that the yields of the 4 cracks are close to each other during the production of the 4 cracks, which indicates that the crack interference is weak, and further verifies that the 4 cracks are the optimal number of cracks.
FIG. 10 is a fracture length optimization chart, and the horizontal well productivity is increased with the increase of the fracture length, but the increase amplitude is gradually smaller. When the half length of the fracture is more than 40 meters, the capacity of the fractured horizontal well is slowly increased and decreased, so that the optimal half length of the fracture is 40 meters according to the embodiment of the invention.
Fig. 11 is a non-dimensional fracture conductivity optimization chart, the capacity of the fractured horizontal well is continuously increased with the increase of the non-dimensional conductivity, but the increase amplitude is gradually reduced, and when the non-dimensional fracture conductivity is greater than 0.4, the yield curve of the fractured horizontal well gradually tends to be balanced, so that the optimal non-dimensional fracture conductivity is 0.2 according to the embodiment of the invention.
Based on the same inventive concept, the embodiment of the invention also provides a device for predicting the unsteady state capacity of the closed boundary fractured horizontal well, which is shown in the following embodiment. Because the principle of solving the problems of the device for predicting the unsteady state capacity of the closed boundary fractured horizontal well is similar to that of the method for predicting the unsteady state capacity of the closed boundary fractured horizontal well, the implementation of the device for predicting the unsteady state capacity of the closed boundary fractured horizontal well can refer to the implementation of the method for predicting the unsteady state capacity of the closed boundary fractured horizontal well, and repeated parts are not described again. As used hereinafter, the term "module" or "unit" may implement a combination of software and/or hardware of predetermined functions. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware or a combination of software and hardware is also possible and contemplated.
Fig. 12 is a schematic structural diagram of a device for predicting unsteady state capacity of a closed boundary fractured horizontal well in the embodiment of the present invention, and as shown in fig. 12, the device includes:
the acquiring unit 02 is used for acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of the fractured horizontal well to be predicted;
the fracture parameter and productivity determining unit 04 is configured to input the oil deposit physical property parameter, the fluid physical property parameter, the well structure parameter, and the assumed fracture parameter into a pre-established unsteady-state capacity prediction model of the closed boundary fracturing horizontal well, so as to obtain unsteady-state productivity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and each time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent borehole diameter of the fracture;
the prediction unit 06 is used for establishing a fractured horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady state productivity corresponding to each fracture parameter and time step, and screening out the optimal fractured horizontal well fracture parameters according to the fractured horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for the application of the fractured horizontal well in the oil field;
inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state capacity prediction model of the closed boundary fracturing horizontal well to obtain unsteady state capacity corresponding to the assumed fracture parameter, wherein the unsteady state capacity prediction model comprises the following steps:
determining the equivalent well diameter of the fractured vertical well fractures according to the fracture parameters;
determining the equivalent well diameter of the fractured horizontal well fracture according to the equivalent well diameter of the fractured vertical well fracture and the oil reservoir physical property parameters;
determining the equivalent well position coordinates of the fractured horizontal well fractures of the closed boundary stratum according to the equivalent well diameter of the fractured horizontal well fractures;
and determining the unsteady state capacity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil deposit physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures.
In one embodiment, determining the unsteady state capacity corresponding to the fracture parameter according to the equivalent well position coordinates, the oil reservoir physical property parameter and the fluid physical property parameter of the closed boundary formation fractured horizontal well fracture may include:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all mirror image wells to the equivalent well, the oil deposit physical parameters and the fluid physical parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
In one embodiment, determining the distances from all the mirror image wells to the equivalent wells according to the well position coordinates of the equivalent wells and the well position coordinates of the mirror image wells may include determining the distances from all the mirror image wells to the equivalent wells according to the following formula:
Figure BDA0001934693430000181
wherein r is ij A distance matrix from any mirror image well to an equivalent well; x is the number of fj A horizontal coordinate matrix of the equivalent well vertical well corresponding to a single crack is formed; y is fj A vertical coordinate matrix of the equivalent well vertical well corresponding to a single crack is formed; x is the number of wAi Is the abscissa matrix of any mirror image well; y is wAi Is a vertical coordinate matrix of any mirror image well;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all mirror image wells to the equivalent well, the oil deposit physical parameters and the fluid physical parameters, and the determining may include: determining the pressure drop of each mirror image well and each equivalent well at the equivalent well according to the following formula:
Figure BDA0001934693430000182
wherein, Δ p ij (τ) pressure drop at the equivalent well for each time step; q. q of j Yield per fracture; μ is the fluid viscosity; k is reservoir permeability; h is the reservoir thickness; eta is the pressure conduction coefficient; τ is the number of time steps; t (τ) is the τ -th time step;
determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step, which may include determining the unsteady state capacity of the equivalent well according to the following formula:
when τ =1, C 1 *Q 1 ＝P 1 (ii) a Wherein: c 1 Is the seepage resistance at τ = 1; q 1 Unsteady state capacity at τ = 1; p 1 A pressure drop at τ = 1;
when tau time steps are considered, the unsteady state capacity of the fractured horizontal well is as follows:
Figure BDA0001934693430000191
wherein: c τ The equivalent wells corresponding to the cracks and the mirror image wells of the equivalent wells act on the matrix formed by the seepage resistance of the equivalent wells respectively at the Tth time step; q τ A matrix of all equivalent well productions at the τ time step; p τ The bottom hole drawdown for all equivalent wells at the time step τ is the matrix.
The embodiment of the invention also provides computer equipment which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor executes the method for predicting the unsteady state capacity of the closed boundary fractured horizontal well.
The embodiment of the invention also provides a computer readable storage medium, wherein the computer readable storage medium stores a computer program for executing the method for predicting the unsteady state capacity of the closed boundary fractured horizontal well.
The technical scheme provided by the implementation of the invention has the beneficial technical effects that:
1) The invention establishes a model for predicting the unsteady state capacity of the closed boundary fractured horizontal well, realizes the prediction of the unsteady state capacity of the fractured horizontal well by considering the closed boundary effect, and is suitable for capacity analysis and optimization of the horizontal well capacity in an oil field.
2) Compared with a source function method, the initial energy production result of the method is very close to that of the source function method, the relative error is within 3%, and the accuracy and the reliability of the model are theoretically verified.
3) Compared with the actual production of a mine field, the unsteady state capacity prediction model of the closed boundary fracturing horizontal well provided by the invention has a good fitting effect with actual production data, the coincidence rate of the calculated capacity and the actual capacity is more than 90%, the average error of the initial output is 8.06%, and the average error of the accumulated output is 5.53%. Therefore, the model has high productivity prediction precision and can be popularized and applied in oil fields.
4) The model established by the invention can carry out optimization design on the fracturing parameters of the horizontal well on the oil field site, and provides important basis for formulation of a reasonable working system of the horizontal well and analysis and adjustment of development dynamics.
It will be apparent to those skilled in the art that the modules or steps of the embodiments of the invention described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and alternatively, they may be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, and in some cases, the steps shown or described may be performed in an order different than that described herein, or they may be separately fabricated into individual integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, embodiments of the invention are not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made to the embodiment of the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for predicting unsteady state capacity of a closed boundary fractured horizontal well is characterized by comprising the following steps:
acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of a fractured horizontal well to be predicted;
inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state capacity prediction model of the closed boundary fractured horizontal well to obtain unsteady state capacity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and each time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent borehole diameter of the fracture;
establishing a fracturing horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady capacity corresponding to each fracture parameter and time step, and screening out the optimal fracturing horizontal well fracture parameters according to the fracturing horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for the application of the fractured horizontal well in the oil field;
inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established unsteady state capacity prediction model of the closed boundary fracturing horizontal well to obtain unsteady state capacity corresponding to the assumed fracture parameter, wherein the unsteady state capacity prediction model comprises the following steps:
determining the equivalent well diameter of the fractured vertical well fractures according to the fracture parameters;
determining the equivalent well diameter of the fractured horizontal well fracture according to the equivalent well diameter of the fractured vertical well fracture and the oil reservoir physical property parameters;
determining the equivalent well position coordinates of the fractured horizontal well fractures of the closed boundary stratum according to the equivalent well diameter of the fractured horizontal well fractures;
and determining the unsteady state capacity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil deposit physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures.
2. The method for predicting the unsteady state capacity of the closed boundary fractured horizontal well according to the claim 1, wherein the determining the unsteady state capacity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil reservoir physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well comprises the following steps:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all mirror image wells to the equivalent well according to the well position coordinates of the equivalent well and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all mirror image wells to the equivalent well, the oil deposit physical parameters and the fluid physical parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
3. The method for predicting the unsteady state productivity of the closed boundary fractured horizontal well according to claim 2, wherein the step of determining the distances from all the mirror image wells to the equivalent well according to the well position coordinates of the equivalent well and the well position coordinates of the mirror image wells comprises the step of determining the distances from all the mirror image wells to the equivalent well according to the following formula:
Figure FDA0001934693420000021
wherein r is ij A distance matrix from any mirror image well to an equivalent well; x is the number of fj A horizontal coordinate matrix of the equivalent well vertical well corresponding to a single crack is formed; y is fj A vertical coordinate matrix of the equivalent well vertical well corresponding to a single crack is formed; x is the number of wAi Is the abscissa matrix of any mirror image well; y is wAi Is a vertical coordinate matrix of any mirror image well;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all mirror image wells to the equivalent well, the oil deposit physical property parameters and the fluid physical property parameters, and comprising the following steps: determining the pressure drop of each mirror image well and each equivalent well at the equivalent well according to the following formula:
Figure FDA0001934693420000022
wherein, Δ p ij (τ) pressure drop at the equivalent well for each time step; q. q of j Yield per fracture; μ is the fluid viscosity; k is the reservoir permeability; h is the reservoir thickness; eta is the pressure conduction coefficient; τ is the number of time steps; t (τ) is the τ -th time step;
determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step, wherein the unsteady state capacity of the equivalent well is determined according to the following formula:
when τ =1, C 1 *Q 1 ＝P 1 (ii) a Wherein: c 1 -seepage resistance at τ = 1; q 1 Unsteady capacity at τ = 1; p 1 Is the pressure drop at τ = 1;
when tau time steps are considered, the unsteady state capacity of the fractured horizontal well is as follows:
Figure FDA0001934693420000023
wherein: c τ The equivalent wells corresponding to the cracks and the mirror image wells of the equivalent wells act on the matrix formed by the seepage resistance of the equivalent wells respectively at the Tth time step; q τ For the time step at the τ th, all equivalentsA matrix of well productions; p τ The bottom hole drawdown for all equivalent wells at the time step τ is the matrix.
4. The method for predicting the unsteady state capacity of the closed boundary fractured horizontal well according to claim 1, wherein the fractured horizontal well capacity influencing factor optimization chart comprises the following steps: the number of cracks affects one or any combination of a production capacity influence plate, a yield distribution plate of each crack, a production capacity influence plate of half-length of the crack, and a crack influence plate of non-dimensional crack flow conductivity.
5. The method for predicting the unsteady state capacity of the closed boundary fractured horizontal well according to claim 1, wherein the petrophysical parameters comprise: the size of the reservoir, the thickness of the reservoir, the permeability of the reservoir, the porosity of the reservoir and the comprehensive compression coefficient of the reservoir; the fluid property parameters include: viscosity of the fluid; the well bore structure parameters include: the length of the horizontal section of the horizontal well; the fracture parameters include: crack conductivity, crack length, crack height, crack width, and crack permeability.
6. The utility model provides a closed boundary fracturing horizontal well unsteady state productivity prediction device which characterized in that includes:
the acquiring unit is used for acquiring oil deposit physical property parameters, fluid physical property parameters and well body structure parameters of the fractured horizontal well to be predicted;
the fracture parameter and productivity determining unit is used for inputting the oil deposit physical property parameter, the fluid physical property parameter, the well body structure parameter and the assumed fracture parameter into a pre-established closed boundary fracturing horizontal well unsteady-state productivity prediction model to obtain unsteady-state productivity corresponding to the assumed fracture parameter; continuously modifying the assumed crack parameters and the time step until a plurality of crack parameters and time steps and unsteady-state capacity corresponding to each crack parameter and time step are obtained; the unsteady state capacity prediction model of the closed boundary fractured horizontal well is established in advance by applying a mirror inversion and pressure drop superposition principle according to the equivalent borehole diameter of the fracture;
the prediction unit is used for establishing a fracturing horizontal well productivity influence factor optimization chart according to the obtained multiple fracture parameters and time steps and the unsteady capacity corresponding to each fracture parameter and time step, and screening out the optimal fracturing horizontal well fracture parameters according to the fracturing horizontal well productivity influence factor optimization chart; the optimal fractured horizontal well fracture parameters are used for providing guidance for oilfield field fractured horizontal well application;
the fracture parameter and productivity determining unit is specifically configured to:
determining the equivalent well diameter of the fractured vertical well fractures according to the fracture parameters;
determining the equivalent well diameter of the fractured horizontal well fracture according to the equivalent well diameter of the fractured vertical well fracture and the oil reservoir physical property parameters;
determining the equivalent well position coordinates of the fractured horizontal well fractures of the closed boundary stratum according to the equivalent well diameter of the fractured horizontal well fractures and the fluid physical property parameters;
and determining the unsteady state capacity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil deposit physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well fractures.
7. The device for predicting the unsteady state productivity of the closed boundary fractured horizontal well according to claim 6, wherein the determining of the unsteady state productivity corresponding to the fracture parameters according to the equivalent well position coordinates, the oil reservoir physical property parameters and the fluid physical property parameters of the closed boundary stratum fractured horizontal well comprises:
determining well position coordinates of all mirror image wells corresponding to the closed boundary stratum fracturing equivalent wells according to the equivalent well position coordinates of the closed boundary stratum fracturing horizontal well fractures;
determining the distances from all mirror image wells to the equivalent well according to the well position coordinates of the equivalent well and the well position coordinates of the mirror image wells;
determining the pressure drop of each mirror image well and the equivalent well at the equivalent well according to the distances from all the mirror image wells to the equivalent well, the oil deposit physical property parameters and the fluid physical property parameters;
and determining the unsteady state capacity of the equivalent well according to the pressure drop and the time step.
8. The device for predicting the unsteady state capacity of the closed boundary fractured horizontal well according to claim 6, wherein the fractured horizontal well capacity influencing factor optimization chart comprises the following steps: the number of cracks affects the productivity, the yield distribution of each crack, the half-length of the crack affects the productivity, and the flow conductivity of the dimensionless crack affects the crack.
9. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any of claims 1 to 5 when executing the computer program.
10. A computer-readable storage medium, characterized in that it stores a computer program for executing the method of any one of claims 1 to 5.
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