Method for calculating single well controlled reserves of tight sandstone gas reservoir multi-section fractured horizontal well

Abstract

The invention discloses a single well control reserve calculation method for a tight sandstone gas reservoir multi-section fractured horizontal well, and belongs to the field of fractured horizontal wells. The method comprises the following steps: firstly, determining fracture network characteristics of each fractured section; the matrix seepage length is determined according to the original formation pressure, the well bottom waste flowing pressure and the starting pressure gradient, the matrix seepage width is determined according to the permeability and the width of the area not subjected to fracturing transformation, and the matrix seepage range is determined according to the obtained matrix seepage length and width; according to the fracture network characteristics and the matrix seepage range, the single-section control area of each fracturing section is calculated, and then the single-well control reserves of the horizontal well are determined through the single-section control areas and reservoir data. According to the method, the matrix seepage range is determined through the permeability of the non-fractured transformation area and the permeability of the adjacent fractured sections, that is, the characteristics that the interiors of the fractured sections are heterogeneous and the fractured sections are also heterogeneous are considered, and the accuracy of determining the single well controlled reserves according to the matrix seepage range is improved.

Description

Technical Field

[0001] The invention belongs to the field of fractured horizontal wells, and in particular relates to a method for calculating the controlled reserves of a single well in a multi-stage fractured horizontal well of a tight sandstone gas reservoir. Background Art

[0002] Tight sandstone gas reservoirs are often developed using multi-stage fracturing horizontal wells. Due to the influence of factors such as reservoir heterogeneity and fracturing construction parameters, the reservoir thickness, physical properties, gas content and fracturing scale of each fracturing section of the horizontal well vary greatly, resulting in different reconstruction areas, matrix gas leakage widths and lengths of each fracturing section. Only by calculating the controlled area and reserves of each fracturing section separately and then accumulating the controlled reserves of a single well, can the controlled reserves of a single well in a reservoir with strong heterogeneity be accurately calculated.

[0003] At present, there are two methods for calculating the controlled reserves of a single horizontal well: static method and dynamic method. The static method mainly adopts the volumetric method. The Chinese patent application document with application publication number CN113177322A discloses a method for calculating the controlled reserves of a single fractured well, which is mainly aimed at low-permeability and ultra-low-permeability reservoir types. The single well controlled volume is obtained by obtaining the basic fracture fracture control unit volume V1 and using the starting pressure gradient to calculate the matrix unit seepage volume V2, and then the single well controlled reserves are calculated. Although this method takes into account the influence of different fracturing construction parameters on the fracture volume, and uses the starting pressure gradient to solve the vertical well gas leakage radius, the spacing between the horizontal well fracture sections is greater than the width of the artificial fracture, and there is a long unreconstructed area between the sections. The patent fails to solve the problem of the matrix control width of the horizontal well fracture section, and the horizontal well fracture section control volume will have a large deviation.

[0004] In the January 2017 issue of the Journal of Yangtze University (Natural Science Edition), Cai Zhenhua, Wang Wensheng, Li Yunyun and others published the article “Calculation Method of Dynamic Controlled Reserves of Multi-stage Fractured Horizontal Gas Wells in Tight Sandstone Gas Reservoirs”, which expounded on dynamic reserve calculation methods such as material balance method and production decline method. However, these calculation methods are based on the fact that the gas wells have a lot of gas well production data, and the dynamic reserves are calculated by the cumulative gas production, pressure and other parameters of the gas wells, which have nothing to do with the actual reservoir parameters encountered by the horizontal wells, the fracturing operation parameters, etc. At present, the existing static method for calculating the controlled reserves of a single well in multi-stage fractured horizontal wells in tight sandstone gas reservoirs usually calculates the controlled reserves of a single well by treating the horizontal section as a whole homogeneous reservoir, without considering the differences in geological parameters such as effective thickness, physical properties and gas content at different positions in the horizontal section, and also ignoring the differences in fracture control area caused by different fracturing operation parameters (displacement, sand addition, etc.), which also has a certain impact on the controlled reserves of horizontal wells. Therefore, there is a large error between the single well controlled reserves calculated by the volumetric method and the actual controlled reserves.

[0005] In summary, the existing determination of single well controlled reserves does not take into account the differences in fracturing parameters between fracturing sections in heterogeneous reservoirs and the impact of unfractured areas between fracturing sections on single well controlled reserves, resulting in low accuracy of the obtained single well controlled reserves. Summary of the invention

[0006] The purpose of the present invention is to provide a method for calculating the controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir, so as to solve the technical problem that the influencing factors considered in the prior art for determining the controlled reserves of a single well are not comprehensive, resulting in low accuracy of the obtained controlled reserves of the single well.

[0007] To achieve the above object, the present invention provides a technical solution for calculating the controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir:

[0008] A method for calculating the controlled reserves of a single well in a multi-stage fracturing horizontal well of a tight sandstone gas reservoir comprises the following steps: obtaining reservoir data, a starting pressure gradient and fracture network characteristics of each fracturing section of the horizontal well, wherein the reservoir data comprises gas layer thickness, porosity, permeability, gas saturation, fracturing section spacing, original formation pressure and bottom hole abandoned flow pressure, and the fracture network characteristics comprises sweep width and fracture half length; determining the width of an unfractured reformed area by using the sweep width and the fracturing section spacing, determining the matrix seepage length according to the original formation pressure, the bottom hole abandoned flow pressure and the starting pressure gradient, determining the matrix seepage width according to the fracturing section permeability, the adjacent fracturing section permeability and the width of the unfractured reformed area, and determining the matrix seepage range by using the matrix seepage length and the matrix seepage width; calculating the single-section controlled area of ​​each fracturing section by using the fracture network characteristics and the matrix seepage range; determining the single-section controlled reserves of each fracturing section by using the single-section controlled area and the reservoir data, and determining the controlled reserves of a single well of the horizontal well according to the single-section controlled reserves of each fracturing section.

[0009] The beneficial effects are: first obtain the reservoir data of each fracturing section, and use the obtained data to determine the fracture network characteristics of each fracturing section; use the original formation pressure, the bottom hole abandoned flow pressure and the start-up pressure gradient to determine the matrix seepage length, use the permeability and the width of the unfractured transformation zone to determine the matrix seepage width, and determine the matrix seepage range according to the obtained matrix seepage length and width; calculate the single-stage control area of ​​each fracturing section according to the fracture network characteristics and the matrix seepage range, and then use the single-stage control area and reservoir data to determine the single-stage controlled reserves of each fracturing section, and finally, determine the controlled reserves of the single well of the horizontal well according to the single-stage controlled reserves of each fracturing section. In this application, when determining the matrix seepage range, the width of the unfractured transformation zone and the permeability of the adjacent fracturing sections are considered to determine the matrix seepage range, that is, the characteristics that the inside of the fracturing section is heterogeneous and the various fracturing sections are also heterogeneous are considered, which improves the accuracy of determining the single well controlled reserves according to the matrix seepage range.

[0010] As a further improvement, the calculation formula of matrix seepage width is:

[0011] L i =L iA +L iB

[0012] Among them, L i is the width of matrix seepage in the i-th fracturing section, L iA is the matrix seepage width in the direction of target point A near the wellhead in the i-th fracturing stage, L iB is the matrix seepage width in the direction of target point B near the well tail of the i-th fracturing stage;

[0013] The fracturing sections are arranged in order from the well tail to the well head, and the calculation formulas for the matrix seepage width close to the target point in the fracturing section are:

[0014]

[0015]

[0016] Among them, L iA is the matrix seepage width in the direction of target point A near the wellhead in the i-th fracturing stage, L iB is the matrix seepage width in the direction of target point B near the well tail of the i-th fracturing stage, K i is the permeability of the i-th fracturing stage, K i+1 Permeability of the i+1th fracturing stage, W i is the width of the unfractured zone in the i-th fracturing stage, and i is the serial number of the fracturing stage.

[0017] The beneficial effects are: the matrix seepage length of the fracturing section is determined by referring to the target point position, and the matrix seepage width is determined by the permeability of the adjacent fracturing sections and the width of the unfractured zone, providing a data basis for calculating the single-section control width, making the calculated single-section control width more accurate.

[0018] As a further improvement, the matrix seepage width of the fracturing section adjacent to the target point A is equal to the sum of the matrix seepage width in the direction of the target point B of the fracturing section close to the well tail and the matrix seepage length of the fracturing section; the matrix seepage width of the first fracturing section is equal to the sum of the matrix seepage width in the direction of the target point A of the fracturing section close to the wellhead and the matrix seepage length of the fracturing section.

[0019] As a further improvement, the width of the unfractured zone is calculated as follows:

[0020]

[0021] Among them, W i is the width of the unfractured zone in the i-th fracturing section, D iis the spacing between the i-th fracturing stages, x fi is the sweep width of the i-th fracturing stage, x f(i-1) is the sweep width of the i-1th fracturing section.

[0022] The beneficial effect is that the width of the unfractured zone is determined by the fracture network characteristics and the spacing between the fracturing stages, providing a data basis for the calculation of the matrix seepage width.

[0023] As a further improvement, the calculation formula of matrix seepage length is:

[0024]

[0025] Among them, r i is the matrix seepage length of the i-th fracturing stage, P e is the original formation pressure, P wf is the bottom hole abandoned flow pressure, and λ is the matrix starting pressure gradient of the i-th section.

[0026] The beneficial effect is that the matrix seepage length of the fracturing section is determined by using reservoir data, and a data basis is provided for calculating the control area of ​​a single section of the calculation section.

[0027] As a further improvement, the calculation formula for the single-stage control area is:

[0028] A i =x ie ×y ie

[0029] Among them, A i is the single-stage controlled area of ​​the i-th fracturing stage, y ie is the single-stage control length of the i-th fracturing stage, x ie is the single-stage control width of the i-th fracturing stage.

[0030] The beneficial effect is that the control area is simplified into a rectangle, which facilitates the calculation of the control area.

[0031] As a further improvement, the calculation formulas for the single-segment control length and the single-segment control width are:

[0032] y ie =y fi +r i

[0033] x ie =x fi +L i

[0034] Among them, x fi is the sweep width of the i-th fracturing stage, r i is the matrix seepage length of the i-th fracturing stage, y fiis the half length of the fracture in the i-th fracturing stage, L i Matrix seepage width of the i-th fracturing stage.

[0035] The beneficial effect is that the single-segment control length and width are jointly determined by the swept width and half-length of the fracture network characteristics and the length and width of the matrix seepage, thereby improving the accuracy of the determined single-segment control length and width and providing a data basis for the calculation of the control area.

[0036] As a further improvement, the calculation formula for the single-stage control reserve is:

[0037]

[0038] Among them, G i is the single-stage controlled reserves of the i-th fracturing stage; Bg is the natural gas volume coefficient, A i is the single-stage control area of ​​the i-th fracturing stage, h i is the gas layer thickness of the i-th fracturing stage, is the porosity of the i-th fracturing stage, Sg i is the gas saturation of the i-th fracturing stage.

[0039] As a further improvement, the single well controlled reserves calculation formula is:

[0040]

[0041] Among them, G i is the single-stage controlled reserves of the i-th fracturing stage, and G is the single-well controlled reserves. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a single well control area diagram of the present invention;

[0043] Figure 2 It is a schematic diagram of a method for calculating a single-stage control area of ​​the present invention;

[0044] Figure 3 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0045] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0046] An embodiment of a method for calculating the controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir is as follows:

[0047] Take the Box 1 gas reservoir of the Lower Shihezi Formation in a certain basin in China as an example. The Box 1 gas reservoir of the Lower Shihezi Formation in this area is a braided river deposit with strong heterogeneity and rapid changes in sandstone reservoirs. The reservoir thickness, physical properties, and gas content at different locations in the same river channel vary greatly. The gas content and permeability of the reservoir are mainly affected by the physical properties. The higher the porosity, the higher the gas saturation and the better the permeability. Among them, Well B is a typical horizontal well of the Box 1 gas reservoir of the Lower Shihezi Formation in the X gas field. The actual horizontal section is 900m long, the sandstone is 900m long, and the gas-bearing sandstone is only 439m long. The average total hydrocarbon is 42%, the overall gas-bearing sandstone drilling rate is low, and the reservoir thickness and physical properties at different locations in the horizontal section vary greatly.

[0048] like Figure 3 As shown, the steps for calculating the single well controlled reserves of Well B by the single well controlled reserves calculation method for multi-stage fractured horizontal wells in tight sandstone gas reservoirs of this application are as follows:

[0049] 1) Obtain reservoir data and fracturing construction data of each fracturing section of the horizontal well, wherein the reservoir data includes gas layer thickness, porosity, permeability, gas saturation, fracturing section spacing, original formation pressure, and bottom hole abandoned flow pressure. Obtain the start-up pressure gradient based on the reservoir data. Obtain relevant data of fracture network characteristics based on the reservoir data and fracturing construction data using the existing technology library, and the fracture network characteristics include sweep width and fracture half-length.

[0050] Specifically, the main rock types encountered in the horizontal section of Well B are fine sandstone, medium sandstone, coarse sandstone, etc. Due to the strong heterogeneity of the reservoir, the rock type, physical properties, and gas content encountered in the wellbore do not represent the reservoir characteristics of the entire region. Therefore, the reservoir data in different fracturing sections are determined in combination with the vertical and horizontal reservoir predictions of the horizontal wells. Taking the 9th section of the fracturing section of Well B as an example, the spacing range of the fracturing sections is 80-115m. Combined with the reservoir prediction, the average reservoir data of each fracturing section is obtained. The obtained reservoir data is shown in Table 1 below, and some fracturing construction data are shown in Table 2 below.

[0051] Table 1

[0052]

[0053] 2) Determine the seam network characteristics based on the acquired data.

[0054] The fracture network characteristics include the swept width and the half-length of the fracture. The fracture network characteristics of the hydraulic fracture are related to the reservoir rock type and reservoir physical properties, as well as the construction parameters of each section of the hydraulic fracturing. Therefore, according to the reservoir characteristics and the hydraulic fracturing construction parameters, the parameters such as the half-length of the hydraulic fracture are obtained through the simulation of the hydraulic fracturing software. The maximum and minimum principal stress differences of the formations in the same area are basically the same. Combined with microseismic monitoring, it can be seen that the swept width of the hydraulic fracture is related to the principal stress and construction parameters. In the same area, the half-length of the hydraulic fracture has a certain correlation with the swept width. Through the microseismic monitoring data, it can be seen that the ratio of the half-length of the hydraulic fracture to the swept width of the Box 1 section of the X gas field is basically 4. Therefore, the data such as the half-length and swept width of the hydraulic fractures in each section are clarified.

[0055] The specific data of the fracture half-length and sweep width obtained according to the above formula are shown in Table 2 below:

[0056] Table 2

[0057]

[0058] 3) Determine the matrix seepage range based on the acquired data.

[0059] For each fracturing stage, the matrix gas leakage length can be calculated based on the starting pressure gradient, original formation pressure, abandoned bottom hole flow pressure, etc.; for the matrix gas leakage width between stages, according to the different permeabilities between stages, the reservoir with high permeability has a large seepage width per unit time, so the matrix seepage range can be determined based on the above data obtained. Specifically, the matrix seepage range includes matrix seepage length and matrix seepage width, among which the matrix seepage length is determined by the original formation pressure, the abandoned bottom hole flow pressure and the starting pressure gradient; the matrix seepage width is determined according to the permeability of the fracturing stage, the permeability of the adjacent fracturing stage, and the width of the unfractured transformation area. Specific data are shown in Table 3. The calculation formula of the matrix seepage length is:

[0060]

[0061] Among them, r i is the matrix seepage length of the i-th fracturing stage, P e is the original formation pressure, P wf is the bottom hole abandoned flow pressure, λ is the matrix starting pressure gradient of the i-th section;

[0062] The calculation formula of the matrix seepage width is:

[0063] L i =L iA +L iB

[0064] Among them, L i is the width of matrix seepage in the i-th fracturing section, L iA The matrix seepage width of the i-th fracturing section near the target point A, LiB The matrix seepage width of the i-th fracturing section close to the target point B.

[0065] like Figure 1 , Figure 2 As shown in the figure, the target point refers to the turning point from the vertical well to the horizontal well. Target point A is the position close to the end of the wellhead, and target point B is the position at the end of the horizontal well. Target point B can also be said to be the end of the horizontal well away from the wellhead. The fracturing sections are arranged in sequence from the well tail to the wellhead. The calculation formula for the matrix seepage width close to target point A in the fracturing section is:

[0066]

[0067] Among them, K i is the permeability of the i-th fracturing stage, K i+1 Permeability of the i+1th fracturing stage, W i is the width of the unfractured zone in the i-th fracturing stage.

[0068] The calculation formula of the matrix seepage width close to the target point B in the fracturing section is:

[0069]

[0070] Among them, K i is the permeability of the i-th fracturing stage, K i+1 Permeability of the i+1th fracturing stage, W i is the width of the unfractured zone in the i-th fracturing stage.

[0071] In addition, the matrix seepage width of the fracturing section adjacent to target point A is equal to the sum of the matrix seepage width in the direction of target point B near the well tail of the fracturing section and the matrix seepage length of the fracturing section; the matrix seepage width of the first fracturing section is equal to the sum of the matrix seepage width in the direction of target point A near the wellhead of the fracturing section and the matrix seepage length of the fracturing section. The reason for this calculation is that the seepage on the side of the fracturing section adjacent to target point A near target point B is no longer affected by the fracturing section, and similarly, the matrix seepage performance of the fracturing section adjacent to target point B near target point B is not affected by the fracturing section. Therefore, the matrix seepage width on the side of the fracturing section adjacent to target point A near target point B is equal to the matrix seepage length of the fracturing section, and the matrix seepage width on the side of the fracturing section adjacent to target point B near target point A is also equal to the matrix seepage length of the fracturing section.

[0072] Table 3

[0073]

[0074] 4) Determine the single-segment control area based on the fracture network characteristics and matrix seepage range.

[0075] The controlled length of each fracturing unit is calculated from the half-length of each fracturing section and the matrix seepage length; the controlled width of each fracturing unit is calculated from the affected width of each fracturing section and the matrix seepage width; and the controlled area of ​​each fracturing unit can be simplified into a rectangle to obtain the controlled area of ​​each fracturing unit. Specifically, the calculation formula for the single-section controlled area is:

[0076] A i =x ie ×y ie

[0077] Among them, A i is the single-stage controlled area of ​​the i-th fracturing stage, y ie is the single-stage controlled length of the i-th fracturing stage, x ie is the single-stage control width of the i-th fracturing stage;

[0078] The calculation formulas for the single-segment control length and single-segment control width are:

[0079] y ie =y fi +r i

[0080] x ie =x fi +L i

[0081] Among them, x fi is the sweep width of the i-th fracturing stage, r i is the matrix seepage length of the i-th fracturing stage, y fi is the half length of the fracture in the i-th fracturing stage, L i The matrix seepage width of the i-th fracturing stage. i Equivalent to Figure 2 r e .

[0082] 5) The single-stage controlled reserves are determined using the single-stage controlled area and reservoir data, and the controlled reserves of the single well of the horizontal well are determined based on the single-stage controlled reserves of each fracturing stage.

[0083] By calculating the controlled area of ​​a single stage of the fracturing stage, the single stage controlled reserves are calculated using the volumetric method according to the geological parameters, and the entire single well controlled reserves are the sum of the single stage controlled reserves, and finally the single well controlled reserves are obtained. The calculation formula for the single stage controlled reserves is:

[0084]

[0085] Among them, G i is the single-stage controlled reserves of the i-th fracturing stage; Bg is the natural gas volume coefficient, A i is the single-stage control area of ​​the i-th fracturing stage, hi is the gas layer thickness of the i-th fracturing stage, is the porosity of the i-th fracturing stage, Sg i is the gas saturation of the i-th fracturing stage. Since the measurement units of the data used in this formula are not uniform, in order to adjust the units of various variables, the single-stage controlled reserves G i Multiply the calculation formula by 0.01.

[0086] The calculation formula for single well controlled reserves is:

[0087]

[0088] Among them, G i is the single-stage controlled reserves of the i-th fracturing stage, and G is the single-well controlled reserves.

[0089] The single well controlled reserves data of each fracturing stage of Well B calculated by the above formula are shown in Table 4 below:

[0090] Table 4

[0091]

[0092]

[0093] According to the data in Table 4, the controlled area and geological parameters of each fracturing section vary greatly, and the controlled reserves of each section are also different. The final calculated controlled reserves of Well B are 121.5 million cubic meters. The controlled reserves of each fracturing unit vary greatly, among which the controlled reserves of Section 7 are the largest, at 54.9 million cubic meters, and the controlled reserves of Section 5 are the smallest, at 0.006 million cubic meters.

[0094] Through case analysis, the calculation method of this application is used to determine the matrix seepage range by considering the characteristics that the inside of the fracturing section is heterogeneous and that the various fracturing sections are also heterogeneous, and further determine the controlled reserves of a single well. This solves the problem that the current method for determining the controlled reserves of a single well by fracturing horizontal wells in heterogeneous reservoirs does not consider the influencing factors of the controlled reserves comprehensively, resulting in inaccurate single-well controlled reserves calculated by the existing method, and improves the calculation accuracy of the controlled reserves of a single well in heterogeneous fracturing horizontal wells. The calculation results are closer to actual production, which is of great significance to the fine development of gas fields.

[0095] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments without creative work, or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for calculating the controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir, characterized in that: The method comprises the following steps: Obtaining reservoir data, start-up pressure gradient and fracture network characteristics of each fracturing stage of the horizontal well, wherein the reservoir data includes gas layer thickness, porosity, permeability, gas saturation, fracturing stage spacing, original formation pressure and bottom hole abandoned flow pressure, and the fracture network characteristics include sweep width and fracture half-length; The width of the unfractured zone is determined by using the sweep width and the distance between the fracturing stages. The matrix seepage length is determined according to the original formation pressure, the abandoned flow pressure at the bottom of the well and the starting pressure gradient. The matrix seepage width is determined according to the permeability of the current fracturing stage, the permeability of the adjacent fracturing stage and the width of the unfractured zone. The matrix seepage range is determined by using the matrix seepage length and the matrix seepage width. The single-stage controlled area of ​​each fracturing stage is calculated using the fracture network characteristics and matrix seepage range, and the single-stage controlled reserves of each fracturing stage are determined using the single-stage controlled reserves and reservoir data. The controlled reserves of the single well of the horizontal well are determined based on the single-stage controlled reserves of each fracturing stage.

2. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 1, characterized in that: The calculation formula of the matrix seepage width is: L i =L iA +L iB Among them, L i is the width of matrix seepage in the i-th fracturing section, L iA is the matrix seepage width in the direction of target point A near the wellhead in the i-th fracturing stage, L iB is the matrix seepage width in the direction of target point B near the well tail of the i-th fracturing stage; The fracturing sections are arranged in order from the well tail to the well head, and the calculation formulas for the matrix seepage width close to the target point in the fracturing section are: Among them, L iA is the matrix seepage width in the direction of target point A near the wellhead in the i-th fracturing stage, L iB is the matrix seepage width in the direction of target point B near the well tail of the i-th fracturing stage, K i is the permeability of the i-th fracturing stage, K i+1 Permeability of the i+1th fracturing stage, W i is the width of the unfractured zone in the i-th fracturing stage, and i is the serial number of the fracturing stage.

3. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 2, characterized in that: The matrix seepage width of the fracturing section adjacent to the target point A is equal to the sum of the matrix seepage width in the direction of the target point B of the fracturing section close to the well tail and the matrix seepage length of the fracturing section; the matrix seepage width of the first fracturing section is equal to the sum of the matrix seepage width in the direction of the target point A of the fracturing section close to the well head and the matrix seepage length of the fracturing section.

4. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 3, characterized in that: The calculation formula for the width of the unfractured zone is: Among them, W i is the width of the unfractured zone in the i-th fracturing section, D i is the distance between the i-th fracturing stages, x fi is the sweep width of the i-th fracturing stage, x f(i-1) is the sweep width of the i-1th fracturing section.

5. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 1, characterized in that: The calculation formula of the matrix seepage length is: Among them, r i is the matrix seepage length of the i-th fracturing stage, P e is the original formation pressure, P wf is the bottom hole abandoned flow pressure, and λ is the matrix starting pressure gradient of the i-th section.

6. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 1, characterized in that: The calculation formula for the single-stage control area is: A i =x ie ×y ie Among them, A i is the single-stage control area of ​​the i-th fracturing stage, x ie is the single-stage control length of the i-th fracturing stage, y ie is the single-stage control width of the i-th fracturing stage.

7. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to claim 6, characterized in that: The calculation formulas for the single-segment control length and the single-segment control width are respectively: y ie =y fi +r i x ie =x fi +L i Among them, x fi is the sweep width of the i-th fracturing stage, r i is the matrix seepage length of the i-th fracturing stage, y fi is the half length of the fracture in the i-th fracturing stage, L i Matrix seepage width of the i-th fracturing stage.

8. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to any one of claims 1 to 7, characterized in that: The calculation formula for single-stage controlled reserves is: Among them, G i is the single-stage controlled reserves of the i-th fracturing stage, Bg is the natural gas volume coefficient, A i is the single-stage control area of ​​the i-th fracturing stage, h i is the gas layer thickness of the i-th fracturing stage, is the porosity of the i-th fracturing stage, Sg i is the gas saturation of the i-th fracturing stage.

9. The method for calculating controlled reserves of a single well in a multi-stage fractured horizontal well in a tight sandstone gas reservoir according to any one of claims 1 to 7, characterized in that: The single well controlled reserves calculation formula is: Among them, G i is the single-stage controlled reserves of the i-th fracturing stage, and G is the single-well controlled reserves.

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