A natural fracture accurate positioning and orientation method based on imaging logging information coupling

Abstract

The application provides a core fracture accurate positioning and orientation method based on imaging logging information coupling, which comprises the following steps: firstly, constructing a basic method of a core planar structure positioning and orientation parameter mathematical model; secondly, establishing a core-imaging logging planar structure matching principle according to the corresponding relationship between the core and the imaging logging planar structure; thirdly, establishing an imaging logging and core planar structure positioning and orientation information dataset according to the planar structure positioning and orientation parameter mathematical model and the matching principle; fourthly, determining a core direction line azimuth; and finally, calculating core fracture orientation parameters according to the relationship between the core direction line azimuth and the fracture, so that the core fracture positioning and orientation are realized. The application effectively solves the problem of accurate positioning and orientation of core fractures under complex geological conditions, and provides an important technical foundation for reservoir fine characterization, efficient oil and gas development and enhanced oil recovery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas exploration and development, and particularly relates to a core natural fracture accurate positioning and orientation method based on imaging logging information coupling. BACKGROUND

[0002] The positioning and orientation of core fractures play a key role in oil and gas exploration and development. The observed reservoir fracture characteristics in core samples are not only key information for evaluating oil and gas migration paths and positioning oil and gas reservoirs, but also scientific basis for evaluating reservoir effectiveness and formulating reservoir fracturing strategies. However, natural fractures are affected by complex geological processes, have the characteristics of strong concealment and complex morphology, and core natural fractures need to be accurately oriented to correctly reflect geological information such as fracture characteristics.

[0003] The existing core natural fracture orientation methods mainly include paleomagnetic method and directional coring method, which can realize the positioning and orientation of core fractures to a certain extent, but still have many limitations such as high cost, low efficiency, limited applicability, etc., and are difficult to meet the demand for accurate characterization of core fractures under complex geological conditions.

[0004] Technical scheme of prior art one

[0005] 《Paleomagnetic core orientation method review》. Progress in Geophysics, 2020 35(3):0906-0917, authors: Xie Ji-hai, Ge Kun-peng, Xu Hui-ru, etc. As a traditional core positioning technology, the paleomagnetic method has been widely used in the positioning and orientation of core fractures. Its technical principle is mainly based on the magnetization of the earth's magnetic field on the ferromagnetic minerals in the rock, and the ability of these minerals to record and preserve the direction of the geomagnetic field. Specifically, the earth's magnetic field has the nature of axial geocentric dipole magnetic field, and the remanent magnetization of the rock or sediment under the action of the geomagnetic field is used to restore the original orientation of the core. The paleomagnetic method measures the remanent magnetization in the core by high-precision equipment, separates the viscous remanent magnetization and primary remanent magnetization, and corrects the viscous remanent magnetization component of the core to the present geomagnetic field direction, so as to restore the original orientation of the core and deduce the occurrence of the fracture.

[0006] Disadvantages of prior art one

[0007] 1. High cost. Paleomagnetic measurement requires high-precision equipment such as rotating magnetometer, superconducting magnetometer and demagnetization instrument, and the test process needs a laboratory environment shielded from the magnetic field, which involves high purchase, construction and maintenance costs.

[0008] 2. Strong dependence on core magnetization. Paleomagnetic method has strong dependence on core magnetization and magnetic mineral composition. For rock types with weak magnetism (such as carbonate rock, mudstone, etc.), the remanent magnetization signal is weak, and it is difficult to accurately measure and separate the remanent magnetization component, resulting in unreliable positioning and orientation results.

[0009] 3. Susceptible to later geological processes, limited application range. Thermal events (such as magma intrusion, metamorphism) of strata, chemical changes or folding, faulting and other tectonic activities may cause partial or complete resetting of remanent magnetization information, seriously affecting the measurement accuracy of paleomagnetic method, and limiting its applicability in complex geological conditions.

[0010] Technical solution of prior art two

[0011] Directional coring is a technology that changes the drilling trajectory with special drilling tools to obtain cores in a specific direction during drilling. This method can directly obtain directional cores containing fracture orientation information.

[0012] Disadvantages of prior art two

[0013] Directional coring can directly obtain cores containing fracture orientation, but compared with non-directional coring, directional drilling requires higher technical requirements and is more expensive. At the same time, directional coring has high requirements for drilling operation and equipment, and the operation time is longer than conventional coring, which is difficult to operate and has high time cost. In addition, it also has strict requirements on the formation conditions, and it is difficult to guarantee the core quality and success rate in the formation where the core is easy to break and deform. Summary of the invention

[0014] The main purpose of the present application is to solve the defects of the prior art, and to provide a natural fracture precise positioning and orientation method based on coupling of imaging logging information.

[0015] The present application provides a core fracture precise positioning and orientation method based on coupling of imaging logging information, which comprises the following steps: first, constructing a basic method based on planar structure positioning parameter mathematical model and planar structure orientation parameter mathematical model; then, establishing a core-imaging logging fracture matching principle according to the corresponding relationship between core and imaging logging planar structure parameters; then, establishing an imaging logging and core planar structure positioning and orientation information dataset according to the basic method of planar structure positioning and orientation parameter mathematical model and the matching principle; further determining the direction line direction of the core; finally, calculating the core fracture orientation parameter according to the relationship between the core direction line direction and the fracture, so as to realize the positioning and orientation of the core fracture. The present application effectively solves the problem of accurate positioning and orientation of core fractures under complex geological conditions, and provides an important technical foundation for fine characterization of reservoirs, promotion of efficient oil and gas development and improvement of recovery efficiency.

[0016] The present application adopts the following technical solutions:

[0017] A core natural fracture positioning and orienting method based on imaging logging information coupling, comprising the following steps:

[0018] S1. Basic method for constructing a mathematical model of core planar structure positioning and orienting parameters

[0019] S11. Constructing a mathematical model of planar structure positioning parameters

[0020] Let the planar structure of natural fractures and bedding be F1, the plane where the planar structure F1 is located be S1, the wellbore be a cylinder cy1 with a radius R, the core be a cylinder cy2 with a radius r, and the cylinders cy1 and cy2 have the same axis; take the north direction as 0° and the clockwise direction as positive, and spread the sides of the cylinders cy1 and cy2 into a plane;

[0021] According to the intersection relationship of S1 with cy1 and cy2, the planar structure positioning parameters are obtained:

[0022] (1) Middle depth D m

[0023] When S1 is obliquely intersected with the cylinders cy1 and cy2, let the oblique sections of S1 with the cylinders cy1 and cy2 be ellipses ABCD and A'B'C'D' respectively; F1 is a pair of chord curves in the spread plane graphs of the cylinders cy1 and cy2, and let their expressions be y1=D m +k1sin(θ1+δ1) and y2=D m +k2sin(θ2+δ2) respectively, where D m is the middle depth of the planar structure when S1 is obliquely intersected with the cylinders cy1 and cy2, the independent variables θ1 and θ2 are angles, and θ1 and θ2 ∈ [0, 2π], k1, k2, δ1 and δ2 are constants;

[0024] (2) Top depth D t and bottom depth D b

[0025] When S1 is vertically cut with the cylinders cy1 and cy2, let the intersection lines of the natural fractures F1 with the sides of the cylinders cy1 and cy2 be line segments HQ, IJ, H'Q' and I'J' parallel to the axis, where H' and I' are points on the line segment HI, and Q' and J' are points on the line segment QJ; then the midpoints of the line segment HI and the line segment H'I' are the same point, denoted as the top depth D t of the planar structure; the midpoints of the line segment QJ and the line segment Q'J' are the same point, denoted as the top depth D b of the planar structure;

[0026] S12. Constructing a mathematical model of planar structure orienting parameters

[0027] The directional parameters of the planar structure F1 of natural fracture, bedding plane include the relative tendency γ of planar structure and the relative strike of planar structure ξ , which are as follows:

[0028] (1) The relative tendency of planar structure γ

[0029] Let the core direction line be L, which is a vertical line marked along the top and bottom of the core after coring, indicating the original direction of the core in the ground. The lowest point of S1 intersecting with the core is B'', and the relative tendency of planar structure is the angle of the core direction line L to B'' in the clockwise direction. γ As positive, the distance of the core direction line L to B''; according to the source of the core planar structure image, it is divided into the following three types of models:

[0030] ① The relative tendency of planar structure based on the horizontal photograph of core column γ Mathematical model

[0031] Let the horizontal photograph of core column be the horizontal projection of the side surface of the core column placed horizontally, and the curve A''B''C'' be the intersection line of the planar structure F1 and the side surface of the core column cy2, where B'' is the lowest point of the curve. Then γ is expressed as

[0032] γ = f (α, b, r) (1)

[0033] Where α is the distance of the direction line L to the side surface boundary of the horizontal projection of the core column, b is the distance of B'' to the side surface boundary of the horizontal projection of the core column, and r is the radius of the core;

[0034] ② The relative tendency of planar structure based on the top or bottom surface photograph of core column γ Mathematical model

[0035] Let the top or bottom surface of the core column cy2 be circular, with the center O' and the radius r. The planar structure F1 intersects with cy2 obliquely and intersects with the top or bottom surface of cy2 at MN. The point G is the intersection of the direction line L and the top or bottom surface of cy2. O'P is perpendicular to MN, and T is the intersection of the extension of O'P and the circle O'. The relative tendency of planar structure is the angle of the circular arc GT, with the clockwise direction as positive. γ

[0036] ③ The relative tendency of planar structure based on the rolling photograph of core column γ Mathematical model

[0037] Let the width of the rolling photograph of core column be Dw 1, and the lowest point of the planar structure F1 in the rolling photograph of core column be Z. The distance of Z to the direction line L is Dw 2, and the clockwise direction is positive. Then the relative tendency of planar structure is γ expressed as:​

[0038] (2)

[0039] (2) Strike of planar structure ξ

[0040] Suppose the top or bottom surface of the core column cy2 is circular, the center of the circle is O', and the radius is r. The planar structure F1 is perpendicular to cy2, F1 intersects the top or bottom surface of cy2 at MN, and G is the intersection point of the direction line L and the top or bottom surface of cy2, γ is the angle of the circular arc GT, and the clockwise direction is positive. Then the strike of planar structure is ξ

[0041] ξ = γ ±90° (3)

[0042] (3) Dip of planar structure θ

[0043] Dip of planar structure θ is equal to the angle between the plane S1 where the planar structure F1 is located and its horizontal projection;

[0044] (4) Axial distance of planar structure Dsur

[0045] Axial distance of planar structure Dsur is the distance from the planar structure perpendicular to the wellbore to the core axis;

[0046] Suppose the top or bottom surface of the core column cy2 is circular, the center of the circle is O', and the radius is r. The planar structure F1 is perpendicular to cy2, F1 intersects the top or bottom surface of cy2 at MN, and P is the midpoint of MN. Then the axial distance of planar structure is Dsur is expressed as

[0047] Dsur = O'P (4)

[0048] S2. Based on the relationship between the core and the imaging logging planar structure positioning and orientation parameters, establish the core-imaging logging planar structure matching principle;

[0049] S3. Establish the imaging logging and core planar structure positioning and orientation information dataset;

[0050] Based on steps S1 and S2, establish the imaging logging and core planar structure positioning and orientation information dataset, including the imaging logging planar structure information dataset and the core planar structure information dataset;

[0051] S4. Determine the core direction line azimuth ψ;

[0052] ​Based on the matching principle of core-imaging logging planar structure and the data set of imaging logging and core planar structure information, the orientation of the core direction line is calculated;

[0053] S5. Calculation of core fracture orientation parameters;

[0054] Based on the obtained core azimuth line orientation and the relationship between the core planar structure and the core direction line orientation, the dip direction of the oblique core fractures is calculated. γ c Or the direction of the cracks in the vertically cut rock core.

[0055] Furthermore, the specific principle for matching the core-imaging logging surface structure in step S2 is as follows:

[0056] (1) Matching principle of oblique wellbore planar structure

[0057] Core and imaging logging planar structural parameters meet the following conditions to be considered the same planar structure:

[0058] ① Depth D in the middle of the planar structure in core and imaging logging m equal;

[0059] ② The relative dip of the planar structures in the core and imaging logging θ equal;

[0060] ③ Dip angle of planar structures in core and imaging logging ξ equal;

[0061] (2) Matching principle of vertical shaft surface structure

[0062] Core and imaging logging planar structural parameters meet the following conditions to be considered the same planar structure:

[0063] ①Strike of planar structures in core and imaging logging Dsur equal;

[0064] ② Core and imaging logging planar structure center distance ψ equal;

[0065] ③Top depth D of core and imaging logging t and bottom depth D b equal.

[0066] Furthermore, the specific orientation of the core direction line in step S4 is as follows:

[0067] Using core wear and breakage points as boundaries, the same core cylinder is divided into several segments. For each segment, it is assumed that there are N planar structures that conform to the core-imaging logging planar structure matching principle; for the i-th planar structure, the core azimuth line azimuth... γ i ,tendency ξfi , relative dip ξ ci , strike ψ fi , relative strike = γ ci The direction line azimuth of the i-th planar structure is calculated as follows:

[0068] When the planar structure meets the planar structure matching principle of the oblique wellbore,

[0069] ψ i = ξ fi - γ ci (5)

[0070] When the planar structure meets the planar structure matching principle of the vertical wellbore,

[0071] γ i ψ fi - γ ci (6)

[0072] The direction line azimuth of this core section is,

[0073] (7)

[0074] Further, the dip of the oblique core fracture in step S5 γ c and the strike of the vertical core fracture are calculated as follows:

[0075] (1) The dip of the oblique core fracture = ψ + γ c

[0076] For any oblique core natural fracture with a relative dip of ξ c on the core, if the direction line azimuth of the core section to which it belongs is ψ , then the dip ξ c is:

[0077] ξ c = ψ + ξ c (8)

[0078] (2) The strike of the vertical core fracture

[0079] For any vertical core natural fracture with a relative strike of Figure 1 cThe vertical cutting core natural fracture is set as the direction line azimuth of the core section to which it belongs Figure 2 , then the strike Figure 3 c is:

[0080] Figure 4 c Figure 5 c (9). The beneficial effects of the present application:

[0081] 1. Significant cost-effectiveness. Traditional core fracture positioning and orientation techniques mainly include paleomagnetic method and directional coring method, which rely on high-precision and expensive professional equipment, resulting in high cost. However, the present application significantly reduces the dependence on equipment and experimental cost by constructing a mathematical model of planar structure positioning and orientation parameters and combining the quantitative matching principle of imaging logging fracture and core fracture.

[0082] 2. Significant improvement in reliability. Traditional techniques are limited by rock magnetism, core integrity and other factors, and under complex geological conditions, the fracture positioning and orientation results often have large errors. The technology proposed in the present application is based on the mathematical model of planar structure positioning and orientation and the quantitative matching principle, and through the coupling relationship between imaging logging and core information, the limitations of traditional methods are effectively overcome, and the reliability and accuracy of the results are significantly improved.

[0083] 3. Perfect method system, wide applicability. The core fracture positioning and orientation technology proposed in the present application has clear principles and is easy to popularize and apply. The mathematical model of planar structure positioning and orientation parameters and the quantitative matching principle have strong universality, providing reliable technical support for fracture positioning and orientation in complex geological environments. BRIEF DESCRIPTION OF DRAWINGS

[0084] Figure 6 is the technical idea provided by the present application;

[0085] Figure 7 is the planar structure intersecting with the wellbore and the core oblique mode diagram provided by the present application;

[0086] Figure 8 is the planar structure intersecting with the wellbore and the core vertical cutting mode diagram provided by the present application;

[0087] Figure 9 is the planar structure image orientation parameter model diagram of the core column horizontal placement photo provided by the present application;

[0088] Figure 10 is the planar structure image orientation parameter model diagram of the core column top and bottom surface photo provided by the present application;

[0089] Figure 1 is the planar structure image orientation model diagram of the core column rolling scan photo provided by the present application;

[0090] Figure 2 is a core planar structure No. 1 (Table 3) orientation parameter map provided by the present application;

[0091] Figure 3 is a core planar structure No. 3 (Table 3) orientation parameter map provided by the present application;

[0092] ξ is a core planar structure No. 4 (Table 3) orientation parameter map provided by the present application;

[0093] γ is a core planar structure No. 7 (Table 3) orientation parameter map provided by the present application. DETAILED DESCRIPTION

[0094] In order to make the objectives, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0095] The application principles of the present application will be further described below with reference to the accompanying drawings and specific embodiments.

[0096] The present application proposes a basic method of constructing a set of planar structure positioning and orientation parameter mathematical models; then a set of core-imaging logging fracture matching principles is established according to the corresponding relationship between the core and the imaging logging planar structure; then the imaging logging and core planar structure positioning and orientation information dataset is established according to the basic method of the planar structure positioning and orientation parameter mathematical models and the matching principles, and the core direction line azimuth is determined; finally, the core fracture orientation parameters are calculated according to the relationship between the core direction line azimuth and the fractures, so as to realize the positioning and orientation of the core fractures. The natural fracture positioning and orientation technology based on the imaging logging information coupling proposed by the present application can obtain good natural fracture orientation results of the core.

[0097] As shown in Figure 4 , a natural fracture accurate positioning and orientation method based on imaging logging information coupling of the present application includes the following steps:

[0098] S1. Constructing a basic method of core planar structure positioning and orientation parameter mathematical models.

[0099] S11. Planar structure positioning parameter mathematical model

[0100] Let natural fracture, bedding and other planar structures be F1, the plane where planar structure F1 is S1, the wellbore (i.e. the well wall of imaging logging) be a cylinder cy1 with radius R, the core be a cylinder cy2 with radius r, and the cylinders cy1 and cy2 have the same axis. Take the north direction as 0° and the clockwise direction as positive, and spread the sides of the cylinders cy1 and cy2 into a plane.

[0101] According to the intersection relationship between S1 and cy1 and cy2, the following planar structure positioning parameters can be obtained:

[0102] (1) Middle depth D m

[0103] Middle depth D m is a positioning parameter when the planar structure is oblique to the core or the wellbore, and is specifically as follows:

[0104] When S1 is oblique to the cylinders cy1 and cy2, let the oblique sections of S1 and cy1 and cy2 be ellipses ABCD and A'B'C'D' respectively; F1 is a pair of chord curves in the spread plane of cy1 and cy2, and let their expressions be y1=D m +k1sin(θ1+δ1) and y2=D m +k2sin(θ2+δ2) respectively, where D m is the middle depth of the planar structure when S1 is oblique to the cylinders cy1 and cy2, the independent variables θ1 and θ2 are angles, and θ1 and θ2 ∈ [0, 2π], k1, k2, δ1 and δ2 are constants; the middle depth D m is a planar structure positioning parameter, as shown in γ .

[0105] (2) Top depth D t and bottom depth D b

[0106] Top depth D t and bottom depth D b are positioning parameters when the planar structure is vertical to the core and the wellbore, and are specifically as follows:

[0107] When S1 is vertical to the cylinders cy1 and cy2, let the intersection lines of natural fracture F1 and the sides of cy1 and cy2 be line segments HQ, IJ, H'Q' and I'J' parallel to the axis, where H' and I' are points on line segment HI, and Q' and J' are points on line segment QJ; then the midpoints of line segment HI and line segment H'I' are the same point, denoted as planar structure top depth D t ; the midpoints of line segment QJ and line segment Q'J' are the same point, denoted as planar structure top depth D b ; as shown in γ .

[0108] S12, Mathematical Model of Orientation Parameters for Planar Structures

[0109] Based on planar structures such as natural cracks and bedding planes, F1 orientation parameters include the relative dip γ and relative strike of the planar structures. γ wait.

[0110] (1) Relative dip of planar structures Figure 4

[0111] Let L be a vertical line marked along the top and bottom of the core sample after core extraction, indicating the original orientation of the core underground. For example... γ As shown, the lowest point where S1 intersects with the core is B'', then the planar structure relatively dips... Figure 4 The angle from core direction line L to B'' is defined with clockwise as positive. Based on the sources of core planar structure images: horizontal core column photographs, top and bottom core column photographs, and roll-scan core column photographs, the following information was obtained: γ Three commonly used models:

[0112] ① Relative dip of planar structures based on transverse core photographs γ Mathematical model

[0113] Assume the horizontal photograph of the core column is the horizontal side projection of the core column when it is placed horizontally. γ (b) Curve A''B''C'' is the intersection of the planar structure F1 and the side of the core column cy2, where B'' is the lowest point of the curve. γ The relationship between B'' and the projection of the direction line L onto the top surface of the core column in the top view is as follows: Figure 5 As shown in c, then γ This can be expressed as,

[0114] Dw = f (α, b, r) (1)

[0115] Where α is the distance from the direction line L to the horizontal projection side boundary of the core column, b is the distance from B'' to the horizontal projection side boundary of the core column, and r is the core radius.

[0116] ② Relative dip of planar structures based on core column top and bottom photographs Dw Mathematical model

[0117] The photographs of the top and bottom surfaces of the core column show images of the top and bottom of the core column. Assume the top or bottom surface of core column cy2 is circular, with center O' and radius r. The planar structure F1 intersects cy2 obliquely and intersects the top or bottom surface of cy2 at MN. Point G is the intersection of direction line L and the top or bottom surface of cy2. O'P is perpendicular to MN, and T is the intersection of the extension of O'P and circle O'. Then the planar structure dips relatively... Figure 6 The angle of the arc GT (clockwise is positive), such asγ is shown.

[0118] ③Relative tendency of planar structure in core barrel roll scan photo ξ Mathematical model

[0119] The core barrel roll scan photo is an image generated by continuous shooting or scanning when rolling the core barrel. Let the width of the core barrel roll scan photo be L, the lowest point of the planar structure F1 in the core barrel roll scan photo be Z, and the distance from Z to the direction line L be Figure 5 1, the relative tendency of the planar structure F1 in the core barrel roll scan photo be γ 2 (positive value for clockwise), as shown in ξ , the relative tendency of the planar structure F1 can be expressed as: ξ = γ

[0120] (2)

[0121] (2) Relative strike of planar structure θ

[0122] As shown in θ , let the top or bottom surface of the core barrel cy2 be circular, the center of the circle be O', and the radius be r. The planar structure F1 is vertically cut by cy2, that is, the core barrel axis is parallel to F1, F1 intersects the top or bottom surface of cy2 at MN, and G is the intersection point of the direction line L and the top or bottom surface of cy2, Dsur is the angle of the circular arc GT (positive for clockwise direction), and the relative strike of the planar structure F1 can be expressed as: Dsur

[0123] ±90° (3) Figure 5

[0124] (3) Dip angle of planar structure Dsur

[0125] The dip angle of the planar structure F1 is equal to the angle between the plane S1 on which the planar structure F1 is located and its horizontal projection Dsur =

[0126] (4) Axial distance of planar structure γ

[0127] The axial distance of the planar structure F1 is the distance from the planar structure vertically cut by the wellbore to the core axis. θ

[0128] As shown in ξ , let the top or bottom surface of the core barrel cy2 be circular, the center of the circle be O', and the radius be r. The planar structure F1 is vertically cut by cy2, that is, the core barrel axis is parallel to F1, F1 intersects the top or bottom surface of cy2 at MN, and P is the midpoint of MN, and the axial distance of the planar structure F1 can be expressed as Dsur

[0129] ψ ​​​​​O'P (4)

[0130] S2. According to the relationship between the core and the imaging logging planar structure positioning and orientation parameters, the core-imaging logging planar structure matching principle is established.

[0131] In order to determine the relationship between the imaging logging planar structure inclination and the core direction line, it is necessary to determine whether the imaging logging planar structure image and the core planar structure are the same planar structure. According to the relationship between the planar structure and the wellbore, for the same type (natural fracture, bedding plane, etc.) of planar structure, there are the following two matching conditions:

[0132] (1) Diagonal wellbore planar structure matching principle

[0133] The core and the imaging logging planar structure parameters meet the following conditions to be the same planar structure:

[0134] ① Planar structure middle depth D m is equal.

[0135] ② Planar structure relative inclination γ is equal.

[0136] ③ Planar structure dip angle ξ is equal.

[0137] (2) Vertical wellbore planar structure matching principle

[0138] The core and the imaging logging planar structure parameters meet the following conditions to be the same planar structure:

[0139] ① Planar structure strike ξ is equal.

[0140] ② Planar structure axis distance ψ is equal.

[0141] ③ Top depth D t and bottom depth D b are equal.

[0142] S3. Establishing imaging logging and core planar structure positioning and orientation information dataset

[0143] Based on the above steps S1 and S2, the imaging logging and core planar structure positioning and orientation information dataset is established, including the imaging logging planar structure information dataset, the core planar structure information dataset, and the specific contents are shown in Table 1.

[0144] Table 1 Imaging logging and core planar structure positioning and orientation dataset

[0145]

[0146] S4. Determining the core direction line azimuth ψ.

[0147] The same core barrel is divided into several segments with core barrel wear and breakage points as boundaries. For each segment of core, it is assumed that there are N planar structures that meet the core-imaging well planar structure matching principle. For the ith planar structure, the core azimuth line azimuth is = γ i , the dip is ψ fi , the relative dip is = ξ ci , the strike is γ fi , the relative strike is γ ci . The direction line azimuth of the ith planar structure is calculated according to the following formula,

[0148] When the planar structure meets the oblique wellbore planar structure matching principle,

[0149] ψ i γ fi - γ ci (5)

[0150] When the planar structure meets the vertical cutting wellbore planar structure matching principle,

[0151] = ψ + γ i ξ fi - ψ ci (6)

[0152] Then the direction line azimuth of the segment of core is,

[0153] (7)

[0154] S5. Core fracture directional parameter calculation

[0155] (1) Dip of oblique core fracture ξ c

[0156] For any oblique core natural fracture with a relative dip of ξ c on the core, assuming that the direction line azimuth of the core segment to which it belongs is = ψ + ξ , then the dip Figure 7 c is

[0157] Figure 8 c Figure 9 c (8)

[0158] (2) Strike of vertical core fracture

[0159] For any one of the relative strike of the vertical core fracture on the core Figure 10 c , set the direction line azimuth of the core section to which it belongs as ​ , then the strike ​ c is

[0160] ​ c ​ c (9)

[0161] Embodiment

[0162] This embodiment takes the core wear and breakage point as the limit, and the first barrel core of Well X in Kuqa Sag, Tarim Basin can be divided into five sections. Based on the basic method described in S1 and S2, the core natural fracture positioning and orientation are realized, mainly including the following steps:

[0163] Step 1. Calculate the core planar structure positioning and orientation parameters.

[0164] The planar structure of this section of core includes 6 natural fractures and 1 bedding plane (see Table 3). According to technical scheme S2, the planar structures that meet the imaging logging and core planar structure matching principle are 3 natural fractures and 1 bedding plane, which are planar structures 1, 3, 4, and 7 in Table 3, and the corresponding relationship with the imaging logging planar structure is shown in Table 2. The positioning and orientation parameters of the above four planar structures are calculated respectively:

[0165] ① According to S11 in technical scheme S1, the positioning parameters of core planar structure 1 (natural fracture) in Table 3 are the middle depth Dm (Dm= 1.5 m) and the middle azimuth γm (γm= 0°), and according to technical scheme S1-S12-(1)-③, the orientation parameter of planar structure 1 is its relative dip γc1, and its mathematical model is based on the column rolling scan photo of this section of core. The calculation results according to formula (2) are shown in Table 3; ​

[0166] ② According to technical scheme S1-S12-(1)-①, the orientation parameter of core planar structure 3 (natural fracture) in Table 3 is the relative dip γ c2 , and its mathematical model is based on the horizontal photo of this section of core (Dm= 1.5 m, γm= 0°), and the calculation results according to formula (10) are shown in Table 3, ​

[0167] (10)

[0168] Where a is the distance from the direction line L to the horizontal projection side boundary of the core column, b is the distance from G to the horizontal projection side boundary of the core column, and r is the core radius.

[0169] ​​According to the technical scheme S1-S12-(1)- (2), the directional parameters of the core planar structure 4 (natural fracture) in Table 3 are relative tendency γ c3 , the mathematical model of which is based on the top surface photograph of the core segment ​ , and the calculation results according to formula (11) are shown in Table 3.

[0170] (11)

[0171] According to the technical scheme S1-S12-(1)- (3), the directional parameters of the core planar structure 7 (bedding plane) in Table 3 are relative tendency γ c4 , the mathematical model of which is shown in ​ (clockwise is positive), and the calculation results according to formula (12) are shown in Table 3.

[0172] (12)

[0173] Step 2. Establish the imaging logging and core planar structure positioning and directional information dataset.

[0174] The imaging logging planar structure information dataset E1 and the core planar structure information dataset E2 are established, as shown in Table 2 and Table 3:

[0175] Table 2. Imaging logging planar structure positioning and directional dataset E1

[0176]

[0177] Table 3. Core planar structure positioning and directional dataset E2

[0178]

[0179] Step 3. Determine the directional line azimuth ψ of the core segment.

[0180] According to formula (5) in the technical scheme S4, the directional line azimuth ψ of the planar structures numbered 1, 3, 4 and 7 in Table 3 is calculated i , and the calculation results are shown in Table 3; and then, according to formula (7) in the technical scheme S4, the directional line azimuth ψ of the core segment is calculated, and the calculation results are shown in Table 3.

[0181] Step 4. Core fracture directional parameter calculation.

[0182] Based on the above-obtained directional line azimuth of the core segment and the relationship between the core planar structure and the core directional line, the fracture inclination of the planar structures numbered 2, 5 and 6 in Table 3 is calculated to be 56°, 68° and 172° respectively (Table 3) according to formula (8) in the technical scheme S5-(1), and thus the core fracture positioning and orientation is successful.

[0183] The above merely describes preferred embodiments of the present application, and is not used to limit the present application, any modification, equivalent replacement and improvement within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for accurate positioning and orientation of natural fractures based on coupled imaging logging information, characterized in that, The method comprises the following steps: S1. Basic method for constructing a mathematical model of core planar structure positioning and orientation parameters S11. Constructing a mathematical model of planar structure positioning parameters Let the planar structure of natural fractures and bedding be F1, the plane where the planar structure F1 is located be S1, the wellbore be a cylinder cy1 with a radius R, the core be a cylinder cy2 with a radius r, and the cylinders cy1 and cy2 have the same axis; take the north direction as 0° and the clockwise direction as positive, and spread the side surfaces of the cylinders cy1 and cy2 into a plane; According to the intersection relationship of S1, cy1 and cy2, the planar structure positioning parameters are obtained: (1) Middle depth D m When S1 is oblique to the cylinders cy1, cy2, let the oblique sections of S1 and cy1, cy2 be ellipses ABCD, A'B'C'D' respectively; F1 is a pair of involutes in the developed planar graphs of cy1, cy2, let their expressions be y1=D m +k1sin(θ1+δ1), y2=D m +k2sin(θ2+δ2) respectively, where D m is the middle depth of the surface structure when S1 is oblique to the cylinders cy1, cy2, the arguments θ1, θ2 are angles, and θ1, θ2 ∈ [0, 2π], k1, k2, δ1, δ2 are constants; (2) top depth D t , bottom depth D b When S1 is vertical cutting on the cylinder cy1, cy2, set the intersection of natural fracture F1 and the side of cy1, cy2 as the line segment HQ, IJ, H'Q', I'J' which is parallel to the axis, wherein H', I' are points on the line segment HI, Q', J' are points on the line segment QJ; the midpoint of the line segment HI and the line segment H'I' is the same point, recorded as the top depth of the planar structure D t ; the midpoint of the line segment QJ and the line segment Q'J' is the same point, recorded as the top depth of the planar structure D b ; S12. Constructing a mathematical model of planar structure orientation parameters The directional parameters of the planar structure F1 of natural fractures and bedding planes include a planar structure relative tendency γ and a planar structure relative strike Wherein, α is the distance of the direction line L to the horizontal projection side surface boundary of the core column, b is the distance of B'' to the horizontal projection side surface boundary of the core column, and r is the core radius; , and are specifically as follows: (1) planar fabric relative dip Dw The core direction line L is a vertical line marked on the top and bottom of the core after coring, indicating the original direction of the core in the ground. The lowest point of intersection of S1 and the core is B'', and the relative trend of the planar structure is Dw The angle of the core direction line L to B'' is taken as positive in the clockwise direction. According to the source of the core planar structure image, the following three types of models are divided: ① planar structural trend based on cross-pole photographs Wherein, α is the distance of the direction line L to the horizontal projection side surface boundary of the core column, b is the distance of B'' to the horizontal projection side surface boundary of the core column, and r is the core radius; mathematical model Let the core column transverse photograph be the lateral horizontal projection of the core column placed horizontally, and the curve A''B''C'' be the intersection line of the planar structure F1 and the lateral surface of the core column cy2, where B'' is the lowest point of the curve. Then ξ is represented as, ξ = f (α，b，r) （1） ξ = γ (2) Relative dip of planar structures based on top and bottom photographs of core plugs θ Mathematical model If the top surface or bottom surface of the core column cy2 is circular, the center of the circle is O', the radius is r, the planar structure F1 is oblique to cy2 and intersects the top surface or bottom surface of cy2 at MN, G is the intersection of the direction line L and the top surface or bottom surface of cy2, O'P is perpendicular to MN, T is the intersection of the extension of O'P and the circle O', and the relative dip of the planar structure is θ is the angle of the circular arc GT, and the clockwise direction is positive.

3. Core column roll scan photo of planar structure relative tendency (4) Axial distance Dsur of planar structure Mathematical model Let the width of the core column rolling scan photo be Dsur 1, the lowest point of the planar structure F1 in the core column rolling scan photo is Z, and the distance from Z to the direction line L is Dsur 2, the clockwise is positive, and the planar structure is relative to the tendency Dsur is represented as: （2） (2) planar structural relative strike Dsur= Suppose the top surface or bottom surface of the core column cy2 is circular, the center of the circle is O', and the radius is r. The planar structure F1 is vertically cut by cy2, that is, the axis of the core column is parallel to F1, F1 intersects the top surface or bottom surface of cy2 at MN, and G is the intersection point of the direction line L and the top surface or bottom surface of cy2, S2. Establishing a core-imaging logging planar structure matching principle according to the relationship between the core and the imaging logging planar structure positioning and orientation parameters; is the angle of the circular arc GT, and the clockwise direction is positive. Therefore, the planar structure is relative to the strike S3. Establishing a core-imaging logging planar structure positioning and orientation information dataset; is represented as: Based on steps S1 and S2, the core-imaging logging planar structure positioning and orientation information dataset is established, including an imaging logging planar structure information dataset and a core planar structure information dataset; ±90° （3） (3) Dip of planar structure S4. Determining the core direction line azimuth ψ; faceted construction inclination According to the core-imaging logging planar structure matching principle and the imaging logging and core planar structure information dataset, the core direction line azimuth is calculated; is equal to the angle between the plane S1 in which the faceted construction F1 lies and its horizontal projection; S5. Core fracture orientation parameter calculation Face of the structure axis distance Step S2 in the core-imaging logging planar structure matching principle is specifically as follows: is the distance from the face of the structure to the core axis for a vertical wellbore; If the top surface or the bottom surface of the core column cy2 is circular, the center of the circle is O', and the radius is r, the planar structure F1 is vertically cut through cy2, F1 intersects the top surface or the bottom surface of cy2 at MN, and P is the midpoint of MN, then the axial distance of the planar structure is (1) Planar structure matching principle for oblique wellbore is represented as: When the core and imaging logging planar structure parameters meet the following conditions, they are the same planar structure: O'P (4) (2) Planar structure matching principle for vertical wellbore When the core and imaging logging planar structure parameters meet the following conditions, they are the same planar structure: Step S4 in the core direction line azimuth is specifically as follows: When the planar structure meets the planar structure matching principle for oblique wellbore, When the planar structure meets the planar structure matching principle for vertical wellbore, The direction line azimuth of this core is, The dip of the cross-cut core fracture is calculated according to the core orientation line orientation obtained in step S4 and the relationship between the core planar structure and the core orientation line orientation (2) Strike of vertical core fracture c or the strike of the vertical core fracture.

2. The method for natural fracture pinpointing and orientation coupled with imaging logging information according to claim 1, characterized in that, When the planar structure meets the planar structure matching principle for oblique wellbore, ​ ​ ① core and imaging well facies structure middle depth D m equal; 2. Core and imaging well face structure relative dip ​ Equal; 3. Core and imaging well log planar structure dip ​ Equal; ​ ​ ① core and imaging well facies structure strike ​ equal; ② Core and imaging logging planar structure center distance ​ equal; ③ Core and imaging log top depth D t and bottom depth D b are equal.

3. The method of claim 1, wherein, ​ With the core abrasion, broken point as the limit, the same barrel core is divided into several sections, for each section of core, set it to exist N planar structure to meet the core-imaging logging planar structure matching principle; for the ith planar structure, the core azimuth line azimuth ​ i , dip ​ fi , relative dip ​ ci , strike ​ fi , relative strike ​ ci ; The direction line azimuth of the ith planar structure is calculated as follows: ​ ​ i ​ fi - ​ ci （5） ​ ​ i ​ fi - ​ ci （6） ​ （7）。 4. The method for natural fracture precise positioning and orientation coupled based on imaging logging information according to claim 1, characterized in that, Dip of the oblique core fracture in step S5 ​ c and the strike of the vertical core fracture is specifically calculated as: (1) Dip of oblique core fractures ​ c For any natural fracture on a core with a relative dip direction ​ c of ​ , the dip direction ​ c is: ​ c ​ c （8） ​ For any natural fracture on a core with relative strike ​ c , let the direction line azimuth of the core segment to which the natural fracture belongs be ​ , then the strike ​ c is: ​ c ​ c （9）。

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