Shale oil horizontal well spacing optimization method based on interference crack area

Abstract

The invention provides a shale oil horizontal well spacing optimization method based on an interference fracture area. The shale oil horizontal well spacing optimization method based on the interference fracture area comprises the steps that 1, a three-dimensional geomechanical model containing double wells is established; step 2, calculating geometric parameters of the fracturing crack; step 3, extracting fracturing crack characteristic parameters, namely interference crack area-crustal stress vertical plane areas of all failure units; 4, keeping in-situ geomechanical parameters and construction parameters of the model unchanged, only changing the well spacing, and repeating the steps 1-3; 5, the well spacing is used as an independent variable, the interference crack area is used as a dependent variable, a relational graph that the cross section area of the interference crack changes along with the well spacing is drawn, and the optimal well spacing is determined. The shale oil horizontal well spacing optimization method based on the interference crack area is provided.

Description

Technical Field

[0001] The present invention relates to the technical field of continental shale oil horizontal well fracturing, and in particular to a method for optimizing the spacing of shale oil horizontal wells based on interference fracture areas. Background Art

[0002] The world is rich in shale oil resources, and China is one of the most successful countries in the world in commercial development of continental shale oil. During shale excavation, if the horizontal well spacing is too large, it will lead to insufficient reservoir transformation and reserve utilization under the corresponding fracturing scale conditions, resulting in reserve waste; if the horizontal well spacing is small, strong inter-well pressure interference will affect the gas well production performance and reduce the development efficiency of the block. Unreasonable well spacing will affect the uniformity of geology and fractures and interfere with inter-well communication. China's continental shale oil is in the stage of development breakthrough. Inter-well interference and fracturing shock are the main factors affecting shale development. Optimizing the horizontal well spacing of shale, overcoming the difficulties in continental shale oil exploration, clarifying the sedimentary environment of organic-rich shale, accelerating the exploration and development of medium- and high-mature continental shale oil, and improving the recovery rate are expected to provide a theoretical basis and technical support for the large-scale economic exploration and development of China's continental shale oil.

[0003] At present, the demonstration of shale oil and gas development well spacing at home and abroad mainly adopts qualitative judgment and numerical simulation methods to roughly determine, and adjusts through field tests and test analysis. The advantage of this method is that it is directly combined with geological conditions, but the disadvantages are large blindness, long time, high cost, and lack of a method for well interference intensity analysis and well spacing determination based on quantitative characterization. The natural fractures in the reservoir seriously affect the stress field update and distribution state during the fracturing process, and the well interference is complicated. At this time, the role of well spacing in the efficient production of oil and gas is particularly important. The well spacing optimization method based on the interference fracture area has guiding significance for on-site fracturing construction.

[0004] CN115659724A provides a method for evaluating the reasonable well spacing for shale gas development based on the distribution of fracture networks after compression, including: conducting an analysis and evaluation of the extension of the fracture network after compression of the gas well under the test well spacing and constructing a hydraulic fracture model, optimizing the fracture network parameters, taking the economic evaluation well spacing as the lower limit and the simulated fracture length after compression as the upper limit, and combining numerical simulation, unstable production analysis, small well spacing test and interference well test results to determine the best well spacing for shale gas development. Due to the differences in geological parameters and construction conditions of different projects, only one test well spacing is not universal and has no reference for determining the well spacing suitable for the overall project. The reliability of the optimal well spacing value obtained by simulation based on the optimization of the fracturing parameters of the test well spacing is not high.

[0005] CN114329346A discloses a method for calculating and arranging reasonable well spacing for a three-dimensional development well network. According to the basic physical properties of the target reservoir, the development units are divided vertically. For each individual development unit, the reasonable well spacing of all development units in the three-dimensional well network is obtained to realize the well spacing calculation of the three-dimensional development well network. Horizontal wells are deployed according to the reasonable well spacing corresponding to each development unit in the three-dimensional well network to realize the reasonable well spacing calculation and well layout of the three-dimensional development well network. The sizes of the excavation units divided vertically according to the reservoir properties are indeterminate. Even if the optimal well spacing is determined for the independent units, it cannot be guaranteed that there is no interference between the wellbores of adjacent units. The staggered arrangement of wellbores cannot avoid all interference, and the cost performance is low.

[0006] CN112241801A provides a method and device for determining the optimal well spacing for shale gas development. The method includes clarifying the type of well-to-well interference, establishing a gas reservoir numerical simulation conceptual model, using the gas reservoir numerical simulation conceptual model to simulate the impact of well-to-well interference on gas well production dynamics, and analyzing the impact of well spacing on development indicators; by adjusting the well spacing parameters in the gas reservoir numerical simulation conceptual model and combining with the net present value model, the optimal well spacing for shale gas development is determined. The gas reservoir model cannot intuitively display the crack extension image under the well spacing, cannot directly feedback the strength of the well-to-well interference, and has a single function. Establishing numerical analysis simulation before engineering development is currently a common means, and the determination of shale gas excavation well spacing can also be determined by numerical simulation. How to simply and efficiently optimize the well spacing is a focus of current research.

[0007] The above existing technologies are significantly different from the present invention and fail to solve the technical problem we want to solve. For this reason, we have invented a new method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area. Summary of the invention

[0008] The purpose of the present invention is to provide a shale oil horizontal well spacing optimization method based on interference fracture area, which can effectively solve the well spacing optimization problem in shale oil development projects from the perspective of the inter-well interference fracture area changing trend line.

[0009] The purpose of the present invention can be achieved by the following technical measures: a method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area, the method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area comprises:

[0010] Step 1: Establish a three-dimensional geomechanical model containing two wells;

[0011] Step 2: Calculate the geometric parameters of the fracturing crack;

[0012] Step 3: Extract the characteristic parameters of the hydraulic fractures, namely the interference fracture area - the vertical surface area of ​​the in-situ stress of all the failure units;

[0013] Step 4: Keep the in-situ geomechanical parameters and construction parameters of the model unchanged, only change the well spacing, and repeat the above steps 1-3;

[0014] Step 5: With the well spacing as the independent variable and the interfering fracture area as the dependent variable, a relationship diagram of the interfering fracture cross-sectional area changing with the well spacing is plotted to determine the optimal well spacing.

[0015] The purpose of the present invention can also be achieved by the following technical measures:

[0016] In step 1, a three-dimensional geomechanical model containing two wells is established using numerical simulation software based on reservoir mechanical parameters, porosity and permeability parameters, in-situ geostress and natural structural surface distribution characteristics.

[0017] In step 1, the formation geological parameters referenced when establishing the model, including reservoir mechanical parameters, porosity and permeability parameters, and in-situ geostress, are established according to the actual engineering formation structure.

[0018] In step 1, the formation characteristics are the distribution structure of the actual continental shale formation obtained by logging interpretation, and the numerical model contains reservoirs and interlayers; the distribution characteristics of natural structural planes include the strike, dip and inclination of bedding and natural fractures; the formation characteristics in the numerical model are established according to the actual formation structure, and the distribution of natural structural planes is randomly generated according to the statistical characteristic parameters that satisfy the bedding and natural fractures.

[0019] In step 4, the on-site fracturing construction parameters include construction displacement, viscosity, liquid volume, cluster spacing, section spacing, and well spacing; the ground stress conditions include the vertical stress of the reservoir, the maximum and minimum horizontal principal stresses, and the initial pore pressure.

[0020] In step 1, the three-dimensional geomechanical model containing two wells is established as follows:

[0021] E=f 1 (C 1 ) (1)

[0022] v=f 2 (C 2 ) (2)

[0023] σ c =f 3 (C 3 ) (3)

[0024]

[0025] σ t =f 5 (C 5 ) (5)

[0026] φ=f 6 (C 6 ) (6)

[0027] k=f 7 (C 7 ) (7)

[0028] Where: E is the elastic modulus of shale, GPa; ν is the Poisson's ratio of shale; σ c is the uniaxial compressive strength of shale, MPa; is the internal friction angle of shale σ t ,°; is the tensile strength of shale, MPa; φ is the porosity of shale; κ is the permeability of shale, mD; f i (i=1,…,7) are different logging interpretation functions; C i (i=1,…,7) are different types of logging data.

[0029] In step 2, based on the three-dimensional geomechanical model, combined with the actual construction parameters such as displacement, viscosity, liquid volume, cluster spacing, section spacing, and well spacing, a horizontal well synchronous fracturing fracture expansion simulation is carried out to calculate the fracturing fracture geometric parameters.

[0030] In step 2, the fracturing fracture geometric parameters include the number of damaged units and the interference fracture area.

[0031] In step 3, the established model is divided into unit grids of the same area, and the fracture area of ​​each unit cell is extracted, that is, the characteristic parameters of the fracturing fracture are extracted, and then a relationship diagram between the interference fracture area and the spacing change is drawn.

[0032] In step 3, the characteristic parameter of the fracturing crack is extracted, namely, the interference crack area - the area of ​​the vertical surface of the in-situ stress of all the damaged units. This surface is parallel to the wellbore layout plane and is representative, and all units have the same size. The statistical interference crack area can reduce the amount of calculation relative to the volume of the crack unit, and the statistical interference crack area is more quantitative relative to the number of crack units; the vertical surface of the in-situ stress of each unit is called the cross-section, and the area of ​​the vertical surface of the in-situ stress of each unit is called the cross-sectional area. The interference crack area is the sum of the cross-sectional areas of all the damaged units.

[0033] In step 4, the in-situ geomechanical parameters and construction parameters of the model are kept unchanged, and only the value of the well spacing is changed using the control variable method. Three simulation tests are carried out for each well spacing, and the average value of the interference fracture area obtained from the three simulations is selected as the final interference fracture area, and the above steps 1-3 are repeated.

[0034] In step 5, with the well spacing as the independent variable and the interfering fracture area as the dependent variable, a relationship diagram of the cross-sectional area of ​​the interfering fractures changing with the well spacing is drawn, and a data trend line is fitted based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the point where the fracture overlap area is the minimum. The corresponding well spacing is the optimal well spacing.

[0035] The purpose of the present invention can also be achieved through the following technical measures: a shale oil horizontal well spacing optimization system based on interference fracture area, which adopts a shale oil horizontal well spacing optimization method based on interference fracture area to determine the optimal well spacing of shale oil horizontal wells.

[0036] The shale oil horizontal well spacing optimization method based on the interference fracture area in the present invention comprehensively considers the reservoir mechanical parameters, porosity parameters, net pressure in the fracture, reservoir transformation volume and fracture width, in-situ ground stress and natural structural surface distribution characteristics, and establishes a full three-dimensional field-scale geomechanical matrix-fracture full coupling model. The physical meaning of each parameter is clear and the simulation results are accurate. With the well spacing and fracture cross-sectional area as variables, the characteristic parameters of the fracturing fracture are extracted, and the fracture total cross-sectional area-well spacing change relationship curve is drawn. According to the trend line fitting of the field data points, the tangent intersection point, that is, the inflection point of the trend line change, represents the well spacing-interference fracture area relationship diagram, and the trend line is drawn according to the data point fitting. The tangent intersection point is the inflection point of the trend line change. At this time, the interference fracture overlap area is the smallest, and the corresponding well spacing is the minimum value of the optimal well spacing fracture overlap area, and the corresponding well spacing is determined as the optimal well spacing. According to the well spacing data results for the reasonable development of the block, the reasonable development well spacing can be clarified, the effective development of shale gas can be achieved, the economic benefits can be improved, and the basis for determining the well spacing of shale oil development projects can be provided.

[0037] The present invention optimizes the well spacing of shale oil horizontal wells through numerical simulation based on statistics of interference fracture area. A three-dimensional geomechanical model containing two wells is established according to formation geological parameters such as reservoir mechanical parameters, porosity and permeability parameters, in-situ geostress, and distribution characteristics of natural structural surfaces; a horizontal well synchronous fracturing fracture expansion simulation is carried out according to the three-dimensional geomechanical model, and the geometric parameters of fracturing interference fractures are calculated; the characteristic parameters of fracturing fractures are extracted according to the number of fracture units and the area of ​​interference fractures; the in-situ geomechanical parameters and construction parameters of the model are kept unchanged, only the well spacing is changed, and the above steps are repeated; a plate curve 1 is formed with the well spacing and the cross-sectional area of ​​interference fractures as variables to optimize the well spacing, which is helpful to improve the fracturing effect and oil and gas recovery rate of continental shale reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of a specific embodiment of the method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area of ​​the present invention;

[0039] Figure 2 This is a simplified schematic diagram of the numerical model described in Example 2 of the present invention;

[0040] Figure 3 It is a schematic top view of a simplified model when different wellbore distances are set in Example 2 of the present invention;

[0041] Figure a is a schematic top view of a simplified model when the wellbore distance is set to 700m in Example 2 of the present invention; Figure b is a schematic top view of a simplified model when the wellbore distance is set to 500m in Example 2 of the present invention; Figure c is a schematic top view of a simplified model when the wellbore distance is set to 300m in Example 2 of the present invention; Figure d is a schematic top view of a simplified model when the wellbore distance is set to 100m in Example 2 of the present invention;

[0042] Figure 4 The three-dimensional hydraulic fracturing finite element numerical model described in Example 2 of the present invention;

[0043] Figure 5 This is a curve chart showing the variation of the interference fracture area with the well spacing described in Example 2 of the present invention. DETAILED DESCRIPTION

[0044] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0045] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0046] like Figure 1 As shown, Figure 1 The flowchart of the method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area of ​​the present invention is as follows. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area includes:

[0047] Step 101: According to reservoir mechanical parameters, porosity parameters, in-situ geostress and natural structural surface distribution characteristics, a three-dimensional geomechanical model containing two wells is established using numerical simulation software, such as Figure 2 Shown is a simplified schematic diagram of the numerical model of the present invention;

[0048] Step 102: Based on the three-dimensional geomechanical model, combined with actual construction parameters such as displacement, viscosity, liquid volume, cluster spacing, and segment spacing, a horizontal well synchronous fracturing fracture propagation simulation is performed to calculate the fracturing fracture geometric parameters;

[0049] Step 103: Extract the characteristic parameters of the hydraulic fractures, namely, the interference fracture area - the area of ​​the vertical surface of the in-situ stress of all the damaged units. This surface is parallel to the wellbore layout plane and is representative. All units have the same size. Statistical interference fracture area can reduce the amount of calculation relative to the fracture unit volume. Statistical interference fracture area is more quantitative relative to the number of fracture units. The vertical surface of the in-situ stress of each unit is called a cross section, and the area of ​​the vertical surface of the in-situ stress of each unit is called a cross-sectional area. The interference fracture area is the sum of the cross-sectional areas of all damaged units.

[0050] Step 104: Keep the in-situ geomechanical parameters and construction parameters of the model unchanged, and only change the well spacing, such as Figure 3 The figure shows a simplified schematic top view of the model when different well spacings are set according to the present invention. Three simulation tests are performed for each well spacing, and the average value of the interference fracture area obtained by the three simulations is selected as the final interference fracture area, and the above steps 101-103 are repeated;

[0051] Step 105: With the well spacing as the independent variable and the interference fracture area as the dependent variable, a relationship diagram of the cross-sectional area of ​​the interference fractures changing with the well spacing is drawn, and a data trend line is fitted based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the point where the fracture overlap area is the minimum. The corresponding well spacing is the optimal well spacing.

[0052] As a preferred embodiment of the present invention, the formation geological parameters referred to when establishing the model, including reservoir mechanical parameters, porosity parameters, in-situ geostress, etc., are established according to the actual engineering formation structure; the number of destruction units of the characteristic parameters of the fracturing cracks is extracted in step 103, and the established model is divided into unit grids of the same area, and the interference fracture area of ​​the model is calculated - the vertical surface area of ​​the geostress of all the destruction units, this surface is parallel to the wellbore layout surface and is representative, and all units have the same size. The statistical interference fracture area can reduce the amount of calculation relative to the fracture unit volume, and the statistical interference fracture area is more quantitative relative to the number of fracture units. The vertical surface of the geostress of each unit is called a cross section, and the vertical surface area of ​​the geostress of each unit is called a cross-sectional area. The interference fracture area is the sum of the cross-sectional areas of all the destruction units, and then a relationship diagram of the interference fracture area with the change in spacing is drawn.

[0053] By changing a single variable, i.e., the spacing between the two wells, a relationship diagram between the well spacing and the area of ​​interfering fractures is drawn, and a trend line is drawn based on the data point fitting. The intersection of the tangent lines is the turning point of the trend line change. At this time, the overlapping area of ​​the interfering fractures is the smallest, and the corresponding well spacing is the optimal well spacing.

[0054] As a preferred embodiment of the present invention, the numerical model is shown in formulas (1)-(7):

[0055] E=f 1 (C 1 ) (1)

[0056] v=f 2 (C 2 ) (2)

[0057] σ c =f 3 (C 3 ) (3)

[0058]

[0059] σ t =f 5 (C 5 ) (5)

[0060] φ=f 6 (C 6 ) (6)

[0061] k = f 7 (C 7 ) (7)

[0062] Where: E is the elastic modulus of shale, GPa; ν is the Poisson's ratio of shale; σ c is the uniaxial compressive strength of shale, MPa; is the internal friction angle of shale, °; σ t is the tensile strength of shale, MPa; φ is the porosity of shale; κ is the permeability of shale, mD; f i (i=1,…,7) are different logging interpretation functions; C i (i=1,…,7) are different types of logging data respectively;

[0063] The model stress boundary and seepage boundary are assigned according to the on-site fracturing construction parameters and ground stress conditions.

[0064] The on-site construction parameters include displacement, viscosity, liquid volume, cluster spacing, and segment spacing.

[0065] As a preferred embodiment of the present invention, the formation geological condition parameters include reservoir mechanical parameters, porosity and permeability parameters, in-situ geostress, and the like.

[0066] The geostress conditions include the vertical stress of the reservoir, the maximum and minimum horizontal principal stresses, and the initial pore pressure.

[0067] Fracture geometry parameters include fracture segment spacing, fracture half-length, reservoir permeability, and natural fractures.

[0068] The fracturing fracture geometric parameters include the number of cells where the fracture is located and the area that interferes with the fracture damage.

[0069] The model is analyzed taking into account well communication interference, fracturing shock, and geological and fracture heterogeneity.

[0070] As a preferred embodiment of the present invention, step 103 divides the established model into unit grids of the same area.

[0071] As a preferred embodiment of the present invention, the fracturing fracture geometric parameters in step 103 include the area of ​​interference fracture destruction.

[0072] As a preferred embodiment of the present invention, in step 104, the in-situ geomechanical parameters and construction parameters of the model are kept unchanged, and the control variable method is adopted to only change the well spacing value.

[0073] When simulating the model for each spacing, conduct three tests and record the data to prevent accidental tests and reduce errors.

[0074] As a preferred embodiment of the present invention, in step 105, when drawing the relationship diagram of the interfering fracture area and the well spacing, a data trend line is fitted according to the field data points, and the intersection of the two tangents of the trend line, that is, the inflection point of the trend line change, corresponds to the well spacing corresponding to the optimal well spacing.

[0075] The present invention establishes a three-dimensional geomechanical model containing double wells based on formation characteristics such as reservoir mechanical parameters, porosity parameters, in-situ geostress, and natural structural surface distribution characteristics; conducts horizontal well synchronous fracturing fracture expansion simulation in combination with actual working conditions; extracts fracture characteristic parameters related to fracture units and interfering fracture areas under different well spacings; draws a well spacing-interfering fracture area relationship diagram, and draws a trend line based on data point fitting. The intersection of the tangents is the inflection point of the trend line change. At this time, the overlapping area of ​​the interfering fractures is the smallest, and the corresponding well spacing is the optimal well spacing. The present invention efficiently solves the well spacing optimization problem in shale oil development projects from the perspective of the trend line of the inter-well interfering fracture area changing with the well.

[0076] The following are several specific embodiments of the present invention.

[0077] Example 1

[0078] A method for optimizing the spacing of shale oil horizontal wells based on interference fracture areas, the method comprising the following steps:

[0079] Step 1. According to reservoir mechanical parameters, porosity and permeability parameters, in-situ geostress and natural structural surface distribution characteristics, a three-dimensional geomechanical model containing two wells is established using numerical simulation software;

[0080] E=f 1 (C 1 ) (1)

[0081] v=f 2 (C2 ) (2)

[0082] σ c =f 3 (C 3 ) (3)

[0083]

[0084] σ t =f 5 (C 5 ) (5)

[0085] φ=f 6 (C 6 ) (6)

[0086] k = f 7 (C 7 ) (7)

[0087] Where: E is the elastic modulus of shale, GPa; ν is the Poisson's ratio of shale; σ c is the uniaxial compressive strength of shale, MPa; is the internal friction angle of shale σ t ,°; is the tensile strength of shale, MPa; φ is the porosity of shale; κ is the permeability of shale, mD; f i (i=1,…,7) are different logging interpretation functions; C i (i=1,…,7) are different types of logging data respectively;

[0088] The stratigraphic characteristics are the distribution structure of actual continental shale formations obtained from logging interpretation, and the numerical model includes reservoirs and interlayers; the distribution characteristics of natural structural planes include the strike, dip and inclination of bedding and natural fractures; the stratigraphic characteristics in the numerical model are established according to the actual stratigraphic structure, and the distribution of natural structural planes is randomly generated according to the statistical characteristic parameters that satisfy the bedding and natural fractures.

[0089] The field fracturing construction parameters include construction displacement, viscosity, liquid volume, cluster spacing, section spacing, well spacing, etc. The ground stress conditions include the vertical stress of the reservoir, the maximum and minimum horizontal principal stresses, and the initial pore pressure.

[0090] Step 2: Based on the three-dimensional geomechanical model, combined with actual construction parameters such as displacement, viscosity, liquid volume, cluster spacing, section spacing, and well spacing, conduct horizontal well synchronous fracturing fracture expansion simulation and calculate the fracturing fracture geometric parameters;

[0091] The fracturing fracture geometric parameters include the number of damaged units and the interference fracture area.

[0092] Step 3: Divide the established model into unit grids of the same area, extract the crack area of ​​each unit cell, that is, extract the characteristic parameters of the fracturing crack, and then draw a relationship diagram between the interference crack area and the spacing change.

[0093] Step 4: Keep the in-situ geomechanical parameters and construction parameters of the model unchanged, and use the control variable method to change only the value of the well spacing. Based on this, build a model in the numerical simulation software to analyze the expansion of cracks under different well spacings. The crack expansion of each well spacing is simulated three times to avoid errors;

[0094] Step 5: With the well spacing as the independent variable and the interference fracture area as the dependent variable, draw a relationship diagram of the cross-sectional area of ​​the interference fractures changing with the well spacing. Fit the data trend line based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the point with the minimum fracture overlap area. The corresponding well spacing is the optimal well spacing.

[0095] Example 2

[0096] The platform-type "factory-like" large-scale continuous operation mode can greatly improve the efficiency of shale oil well construction and realize the efficient development of shale gas. It is the main production mode of shale oil development at present. The establishment of a reasonable horizontal well spacing is the key to controlling the reservoir transformation effect and optimizing the oil well production capacity. If the horizontal well spacing is too large, it will lead to insufficient reservoir transformation and reserve utilization under the corresponding fracturing scale conditions, resulting in a waste of reserves; if the horizontal well spacing is small, the strong inter-well pressure interference will affect the production performance and reduce the benefits of block development.

[0097] Taking the continental shale reservoir in Block X of Shengli Oilfield as an example, the method for optimizing the horizontal well spacing of shale oil based on the interference fracture area in continental shale described in Example 1 is adopted, which specifically includes the following steps:

[0098] Step 1: According to the stratigraphic characteristics shown by the logging interpretation of the continental shale reservoir, the continental shale reservoir is 30m thick, the upper and lower interlayers are both 30m thick, the model length is set to 1100m, and the width is set to 180m. Statistical analysis is performed on the natural structural planes shown by the drill core, the horizontal distribution of the bedding, and two groups of natural fractures with an angle of 75° to the minimum horizontal principal stress are randomly distributed in the reservoir. The mechanical parameters obtained from the indoor test of the continental shale, such as Figure 4 As shown, the numerical model is input to establish a three-dimensional hydraulic fracturing geomechanical finite element numerical model of shale reservoirs, and the model stress boundary and seepage boundary are assigned according to the field fracturing construction parameters and ground stress conditions. Ground stress condition: σ v =91MPa,σ H =79MPa,σ h =72MPa, horizontal stress difference is 7MPa. Construction displacement 18m 3 / min, viscosity 0.015Pa·s, oil layer thickness 30m, total liquid volume 1000m 3 The designed segment length is 60m, the cluster spacing is 10m, and the crack extension process of a single-stage fracturing is simulated.

[0099] Step 2: Based on the finite element numerical model, conduct a simulation of the expansion of horizontal well dense-cut hydraulic fracturing fractures and calculate the geometric parameters of the fracturing fractures.

[0100] Step 3: Divide the established model into unit grids of the same area. The grid unit size of this model is set to length L = 5m, width d = 2m, height h = 2m, and the cross-sectional area of ​​the unit grid Se = L*d. Extract the number of cracks n in each unit grid and calculate the area of ​​the total crack unit grid of the model S = n*Se.

[0101] Step 4: Keep the in-situ geomechanical parameters and construction parameters of the model unchanged, and use the control variable method to adjust only the well spacing d. well The numerical value of is changed, and the expansion of fractures under different well spacings in the numerical simulation software is analyzed based on this. This patent studies the well spacing d well The fracture extensions at 700m, 650m, 600m, 550m, 500m, 450m, 400m, 350m, 300m, 250m, 200m, 150m, and 100m are respectively simulated three times for each well spacing, and the average value is recorded to avoid errors;

[0102] Step 5: Use well spacing d well The independent variable is θ, the interfering fracture area S is the dependent variable, and a graph showing the relationship between the interfering fracture area and the well spacing is drawn. The data trend line is fitted based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the minimum point of fracture overlap area. The corresponding well spacing is the optimal well spacing.

[0103] Example 3

[0104] Taking the continental shale reservoir in Block Y of Shengli Oilfield as an example, the method for optimizing the horizontal well spacing of shale oil based on the interference fracture area in continental shale described in Example 1 is adopted, which specifically includes the following steps:

[0105] Step 1: According to the stratigraphic characteristics shown by the well logging interpretation of the continental shale reservoir, the continental shale reservoir thickness is 35m, the upper and lower interlayer thicknesses are both 35m, the model length is set to 810m, and the width is set to 150m. Statistical analysis is performed on the natural structural planes shown by the drill core, the horizontal distribution of the bedding, and two groups of natural fractures with an angle of 70° with the minimum horizontal principal stress are randomly distributed in the reservoir. The mechanical parameters obtained from the indoor test of the continental shale, such as Figure 4As shown, the numerical model is input to establish a three-dimensional hydraulic fracturing geomechanical finite element numerical model of shale reservoirs, and the model stress boundary and seepage boundary are assigned according to the field fracturing construction parameters and ground stress conditions. Ground stress condition: σ v =100MPa,σ H =85MPa,σ h =76MPa, horizontal stress difference is 9MPa. Construction displacement 20m3 / min, viscosity 0.016Pa·s, oil layer thickness 35m, total liquid volume 1500m 3 The designed segment length is 60m, the cluster spacing is 8m, and the crack expansion process of a single-stage fracturing is simulated.

[0106] Step 2: Based on the finite element numerical model, conduct a simulation of the expansion of horizontal well dense-cut hydraulic fracturing fractures and calculate the geometric parameters of the fracturing fractures.

[0107] Step 3: Divide the established model into unit grids of the same area. The grid unit size of this model is set to length L = 3m, width d = 2m, height h = 2m, and the cross-sectional area of ​​the unit grid Se = L*d. Extract the number of cracks n in each unit grid and calculate the area of ​​the total crack unit grid of the model S = n*Se.

[0108] Step 4: Keep the in-situ geomechanical parameters and construction parameters of the model unchanged, and use the control variable method to adjust only the well spacing d. well The value of is changed, and the expansion of fractures under different well spacings in the numerical simulation software is analyzed based on this. This patent studies the well spacing d well The fracture extensions at 700m, 650m, 600m, 550m, 500m, 450m, 400m, 350m, 300m, 250m, 200m, 150m, and 100m are respectively simulated three times for each well spacing, and the average value is recorded to avoid errors;

[0109] Step 5: Use well spacing d well The independent variable is θ, the interfering fracture area S is the dependent variable, and a graph showing the relationship between the interfering fracture area and the well spacing is drawn. The data trend line is fitted based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the minimum point of fracture overlap area. The corresponding well spacing is the optimal well spacing.

[0110] In addition, the inventors studied the variation of the interference fracture area with the well spacing, such as Figure 5As shown in the figure, y1, y2 and y3 are the fracture areas obtained by three simulations at the same well spacing, and y is the average of y1, y2 and y3. When the distance between wells is small, the fracture area between the two wells will overlap, inducing interference between wells; and the total fracture area decreases rapidly due to the overlap of fractures, and the slope changes greatly from the figure. As the well spacing gradually increases, it gradually becomes gentle and the slope becomes smaller. Therefore, it can be considered that the intersection of the two tangents of the trend line, that is, the inflection point of the trend line change, marks the transition of the well spacing from the extreme overlap and interference state between wells to the interference-free single well behavior. At this time, the fracture overlap area of ​​the two wells is the smallest, and the corresponding well spacing is the optimal well spacing. This method of determining the optimal well spacing is called the "well spacing output graph method."

[0111] 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 has been 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 or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0112] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. Optimization method of horizontal well spacing for shale oil based on interference fracture area, It is characterized in that The shale oil horizontal well spacing optimization method based on interference fracture area includes: Step 1: Establish a three-dimensional geomechanical model containing two wells; Step 2: Calculate the geometric parameters of the fracturing crack; Step 3: Extract the characteristic parameters of the hydraulic fractures, namely the interference fracture area - the vertical surface area of ​​the in-situ stress of all the failure units; Step 4: Keep the in-situ geostress conditions and on-site fracturing construction parameters of the model unchanged, only change the well spacing, and repeat the above steps 1-3; Step 5: With the well spacing as the independent variable and the interfering fracture area as the dependent variable, a relationship diagram of the interfering fracture cross-sectional area changing with the well spacing is plotted to determine the optimal well spacing.

2. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 1, a three-dimensional geomechanical model containing two wells is established using numerical simulation software based on reservoir mechanical parameters, porosity and permeability parameters, in-situ geostress and natural structural surface distribution characteristics.

3. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 2, It is characterized in that In step 1, the formation geological parameters referenced when establishing the model, including reservoir mechanical parameters, porosity and permeability parameters, and in-situ geostress, are established according to the actual engineering formation structure.

4. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 2, It is characterized in that In step 1, the stratigraphic characteristics referenced when establishing the model are the distribution structure of the actual continental shale formation obtained by logging interpretation, and the numerical model includes reservoirs and interlayers; the distribution characteristics of natural structural planes include the strike, dip and inclination of bedding and natural fractures; the stratigraphic characteristics in the numerical model are established according to the actual stratigraphic structure, and the distribution of natural structural planes is randomly generated according to the statistical characteristic parameters that satisfy the bedding and natural fractures.

5. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 4, the on-site fracturing construction parameters include construction displacement, viscosity, liquid volume, cluster spacing, section spacing, and well spacing; the ground stress conditions include the vertical stress of the reservoir, the maximum and minimum horizontal principal stresses, and the initial pore pressure.

6. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 1, the three-dimensional geomechanical model containing two wells is established as follows: E=f 1 (C 1 ) (1) v=f 2 (C 2 ) (2) σ c =f 3 (C 3 ) (3) σ t =f 5 (C 5 ) (5) φ=f 6 (C 6 ) (6) k=f 7 (C 7 ) (7) Where: E is the elastic modulus of shale, GPa; ν is the Poisson's ratio of shale; σ c is the uniaxial compressive strength of shale, MPa; is the internal friction angle of shale σ t ,°; is the tensile strength of shale, MPa; φ is the porosity of shale; κ is the permeability of shale, mD; f i (i=1,…,7) are different logging interpretation functions; C i (i=1,…,7) are different types of logging data.

7. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 2, based on the three-dimensional geomechanical model, combined with the actual construction parameters such as displacement, viscosity, liquid volume, cluster spacing, section spacing, and well spacing, a horizontal well synchronous fracturing fracture expansion simulation is carried out to calculate the fracturing fracture geometric parameters.

8. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 7, It is characterized in that In step 2, the fracturing fracture geometric parameters include the number of damaged units and the interference fracture area.

9. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 3, the established model is divided into unit grids of the same area, and the fracture area of ​​each unit cell is extracted, that is, the characteristic parameters of the fracturing fracture are extracted, and then a relationship diagram between the interference fracture area and the spacing change is drawn.

10. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 9, It is characterized in that In step 3, the characteristic parameter of the fracturing crack is extracted, namely, the interference crack area - the area of ​​the vertical surface of the in-situ stress of all the damaged units. This surface is parallel to the wellbore layout plane and is representative, and all units have the same size. The statistical interference crack area can reduce the amount of calculation relative to the volume of the crack unit, and the statistical interference crack area is more quantitative relative to the number of crack units; the vertical surface of the in-situ stress of each unit is called the cross-section, and the area of ​​the vertical surface of the in-situ stress of each unit is called the cross-sectional area. The interference crack area is the sum of the cross-sectional areas of all the damaged units.

11. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 4, the in-situ geomechanical parameters and construction parameters of the model are kept unchanged, and only the value of the well spacing is changed using the control variable method. Three simulation tests are carried out for each well spacing, and the average value of the interference fracture area obtained from the three simulations is selected as the final interference fracture area, and the above steps 1-3 are repeated.

12. The method for optimizing the spacing of shale oil horizontal wells based on the interference fracture area according to claim 1, It is characterized in that In step 5, with the well spacing as the independent variable and the interfering fracture area as the dependent variable, a relationship diagram of the cross-sectional area of ​​the interfering fractures changing with the well spacing is drawn, and a data trend line is fitted based on the data points. The intersection of the two tangents of the trend line is the inflection point of the trend line change, indicating the point where the fracture overlap area is the minimum. The corresponding well spacing is the optimal well spacing.

13. Shale oil horizontal well spacing optimization system based on interference fracture area, It is characterized in that The shale oil horizontal well spacing optimization system based on interference fracture area adopts the shale oil horizontal well spacing optimization method based on interference fracture area described in any one of claims 1-12 to determine the optimal well spacing of shale oil horizontal wells.

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