Downhole Rotatable Muon Detector and Detection Method

Abstract

This invention discloses a downhole rotatable muon detector and detection method. The muon detector includes a housing, a first detection unit, a second detection unit, and a rotation drive unit. The outer surface of the housing is adapted to the inner wall of the wellbore. The first detection unit and the second detection unit are disposed at a preset distance from each other and are arranged opposite each other within the housing. The first detection unit and the second detection unit each include a detection area for receiving muons, and the detection area extends along the central axis of the muon detector. The rotation drive unit is disposed at the ends of the first detection unit and the second detection unit and is drively connected to the first detection unit and the second detection unit. The rotation drive unit is configured to drive the first detection unit and the second detection unit to rotate synchronously around the central axis by a preset angle, so that the first detection unit and the second detection unit together cover a circumferential direction perpendicular to the central axis during the rotation.

Description

Technical Field

[0001] This invention relates to the field of muons, and more specifically to a downhole rotatable muon detector and detection method. Background Technology

[0002] Muon transmission imaging technology utilizes the attenuation differences of cosmic ray muons as they pass through media of different densities to achieve non-destructive detection of large objects, showing significant application potential in fields such as downhole mineral exploration and cavity identification. Existing downhole muon detectors typically employ a ring-shaped detector array or multiple fixed detector units surrounding the well wall, requiring large amounts of scintillator material and electronic channels, resulting in high manufacturing costs and bulky equipment. To cover the entire circumference around the well wall, traditional solutions often require multiple detector units covering the entire perimeter, which is not only structurally complex but also consumes a large amount of material and is difficult to lower into the well. Summary of the Invention

[0003] The purpose of this invention is to provide a downhole rotatable muon detector and detection method to solve the problems existing in the prior art.

[0004] To address the aforementioned problems, a first aspect of the present invention provides a downhole rotatable muon detector, the muon detector comprising a housing, a first detection unit, a second detection unit, and a rotation drive unit;

[0005] The outer surface of the outer shell is adapted to the inner wall of the well hole;

[0006] The first detection unit and the second detection unit are spaced at a preset distance and are disposed opposite each other within the housing. The first detection unit and the second detection unit each include a detection area for receiving muons, and the detection area extends along the central axis of the muon detector.

[0007] The rotation drive unit is disposed at the end of the first detection unit and the second detection unit and is connected to the first detection unit and the second detection unit in a transmission manner. The rotation drive unit is configured to drive the first detection unit and the second detection unit to rotate synchronously around the central axis by a preset angle, so that the first detection unit and the second detection unit together cover the circumferential direction perpendicular to the central axis during the rotation.

[0008] Optionally, the first detection unit or the second detection unit each includes at least one column of scintillator arrays, wherein the scintillator arrays include a plurality of scintillator units distributed along the axial direction;

[0009] In either the first or the second detection unit, the detection areas of all the scintillator elements in the scintillator array are coplanar, and the planes containing the detection areas of the first and second detection units are parallel to each other.

[0010] Alternatively, in the first detection unit or the second detection unit, multiple columns of the scintillator arrays are arranged sequentially along the circumference and the planes containing the detection areas of two adjacent columns of the scintillator arrays form a preset angle, so that the plane containing the detection area of ​​the first detection unit or the second detection unit as a whole is set as an arc surface, and the openings of the detection areas of the arc surface of the first detection unit and the second detection unit are set opposite to each other.

[0011] Optionally, the rotary drive unit includes a ring track, a first limiting member, a second limiting member, and a drive mechanism.

[0012] The annular track is disposed at the top and / or bottom of the housing, and the axis of the annular track coincides with the central axis of the muon detector;

[0013] The first limiting member and the second limiting member are respectively fixedly connected to the ends of the first detection unit and the second detection unit, and the first limiting member and the second limiting member are respectively in sliding engagement or rolling engagement with the annular track;

[0014] The driving mechanism is configured to drive the first limiting member and the second limiting member to move along the circular track respectively, thereby causing the first detection unit and the second detection unit to rotate synchronously.

[0015] Optionally, the muon detector also includes a signal transmission unit and an angle sensor.

[0016] The signal transmission unit is configured to have an independent readout circuit connected to each scintillator unit in the first and second detection units, for independently acquiring the output signal of the corresponding scintillator array.

[0017] The angle sensor is configured to acquire rotation angle information of the first detection unit and the second detection unit in real time.

[0018] A second aspect of the present invention provides a downhole detection method, the method comprising the following steps:

[0019] From a single muon event, two representative points of impact are determined when the muon passes through the first and second detection units of the muon detector, and the coordinates of the two representative points of impact in the local coordinate system of the muon detector are recorded.

[0020] Based on the coordinate difference between the two representative points of impact, calculate the local zenith angle and local azimuth angle of the muon event in the local coordinate system;

[0021] Obtain the rotation angle of the muon detector around the central axis, and use the rotation angle to transform the local zenith angle and the local azimuth angle in the local coordinate system to the world coordinate system to obtain the world zenith angle and the world azimuth angle;

[0022] According to the preset zenith angle interval and azimuth angle interval, the world zenith angle and the world azimuth angle are binned, each muon event is assigned to the corresponding direction box, and the muon events of each direction box are accumulated and counted during the target body measurement process to obtain the measured count of each direction box.

[0023] Obtain the unobstructed reference measurement count in the same azimuth box, and compare the measured count with the unobstructed reference measurement count to obtain the transmittance or transmittance matrix of each azimuth box for use in the detection of downhole anomalies.

[0024] Optionally, the local coordinate system is set in the following manner:

[0025] With the geometric center of the muon detector as the origin o′, and the direction of the central axis as the z′ axis, and the z′ axis perpendicular to the ground; two orthogonal directions, namely the x′ axis and the y′ axis, are set in the horizontal cross-section of the muon detector, and the x′ axis and the y′ axis rotate synchronously with the rotation of the muon detector around the z′ axis;

[0026] The world coordinate system is set up as follows:

[0027] With the wellhead or downhole reference point as the origin O, the direction perpendicular to the ground as the Z-axis, and the two orthogonal directions in the horizontal plane as the X-axis and Y-axis respectively, the X-axis and the Y-axis are fixed, and the z′ axis coincides with the Z-axis.

[0028] Optionally,

[0029] Let the coordinates of the two hit representative points in the local coordinate system be respectively and ,

[0030] The coordinate differences between the two hit representative points on the x′ axis, the y′ axis, and the z′ axis are as follows:

[0031] Δx′=x2′-x1′,

[0032] Δy′=y2′-y1′,

[0033] Δz′=z2′-z1′,

[0034] The local zenith angle is calculated according to the following formula:

[0035] ,

[0036] Where θ′ is the local zenith angle, and L′ is the three-dimensional spatial distance between the two points represented by the hits.

[0037] The local azimuth angle is calculated according to the following formula:

[0038] ,

[0039] Where φ′ is the local azimuth angle.

[0040] Optionally,

[0041] The direction vectors (ΔX, ΔY, ΔZ) in the world coordinate system are obtained through the following rotation transformation:

[0042] ,

[0043] Wherein, γ is the rotation angle of the muon detector about the central axis, and Δx′, Δy′ and Δz′ are the coordinate differences of the two hit representative points on the x′ axis, the y′ axis and the z′ axis, respectively;

[0044] The zenith angle is calculated according to the following formula:

[0045] ,

[0046] Where θ is the world zenith angle, and L is the total path length between the two hit representative points. ;

[0047] The world azimuth is calculated according to the following formula:

[0048] ,

[0049] Where φ is the world azimuth.

[0050] Optionally,

[0051] The world azimuth angle is converted to a continuous range from 0° to 360° to obtain a continuous world azimuth angle, which is calculated according to the following formula:

[0052] ,

[0053] Where, φ 360 φ represents the continuous world azimuth angle.

[0054] Each of the aforementioned muon events is assigned to a direction box (i, j) determined by the zenith angle bin index and the azimuth angle bin index;

[0055] Calculate the zenith angle bin index using the following formula:

[0056] ,

[0057] Where i is the zenith angle bin index, θ is the world zenith angle, and Δθ is the zenith angle bin interval;

[0058] Calculate the azimuth bin index using the following formula:

[0059] ,

[0060] Where j is the azimuth bin index, φ 360 For continuous world azimuth, Δφ is the azimuth box interval.

[0061] Optionally,

[0062] The method for detecting downhole anomalies based on the transmittance of each of the aforementioned orientation boxes includes:

[0063] Pre-set the transmittance threshold;

[0064] When the transmittance of the steering box is greater than the transmittance threshold, it is determined that there is no obvious abnormality in the spatial direction corresponding to the steering box; when the transmittance of the steering box is less than or equal to the transmittance threshold, it is determined that there is an abnormality in the spatial direction corresponding to the steering box.

[0065] For the direction box that is determined to have an anomaly, the anomaly zenith angle and the anomaly azimuth angle are reversed based on the zenith angle sub-box index and the azimuth angle sub-box index.

[0066] The zenith angle and azimuth angle of the anomalous body are used to indicate the orientation of the anomalous body relative to the center of the detector.

[0067] The method for detecting downhole anomalies based on the aforementioned transmittance matrix includes:

[0068] The transmittance matrix is ​​input into the image reconstruction algorithm, which is selected from any one of the filtered back projection algorithm, iterative reconstruction algorithm, or compressed sensing algorithm. The image reconstruction algorithm generates a three-dimensional density distribution image of the anomaly around the well wall, thereby realizing the detection of the downhole anomaly.

[0069] The beneficial effects of this invention are as follows: the first and second detection units are arranged opposite to each other and include a detection area extending along the axial direction. Combined with a rotation drive unit, they are driven to rotate synchronously by a preset angle, allowing the two detection units to jointly cover a complete circumferential direction perpendicular to the central axis during rotation. Compared to fixed detectors, this significantly reduces the scintillator unit and downhole space occupied, while also reducing system complexity and cost. Attached Figure Description

[0070] Figure 1 This is a three-dimensional schematic diagram of the assembly of a muon detector according to an embodiment of the present invention;

[0071] Figure 2 This is a schematic diagram showing that the plane containing the detection area of ​​the first detection unit in one embodiment of the present invention is arranged in an arc shape.

[0072] Figure 3 for Figure 1 An exploded three-dimensional diagram of the muon detector;

[0073] Figure 4 for Figure 1 An exploded stereoscopic view of the muon detector, with the outer shell removed;

[0074] Figure 5 This is a three-dimensional schematic diagram of a first detection unit or a second detection unit according to an embodiment of the present invention;

[0075] Figure 6 This is a perspective view of a rotary drive unit according to an embodiment of the present invention;

[0076] Figure 7 This is a schematic diagram of the first and second representative hit points according to an embodiment of the present invention;

[0077] Figure 8 This is a schematic diagram of a first detection unit and a second detection unit synchronously rotating around a central axis by a preset angle according to an embodiment of the present invention. Detailed Implementation

[0078] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so as to better understand the purpose, features and advantages of the present invention. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are only for illustrating the essential spirit of the technical solution of the present invention.

[0079] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, components, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0080] Throughout this specification, references to "an embodiment" or "an embodiment" indicate that a particular feature, component, or characteristic described in connection with the embodiment is included in at least one embodiment. Therefore, the appearance of "in an embodiment" or "an embodiment" in various places throughout the specification does not necessarily refer to the same embodiment. Furthermore, a particular feature, component, or characteristic may be combined in any manner in one or more embodiments.

[0081] In the following description, in order to clearly demonstrate the components and working method of the present invention, a number of directional terms will be used. However, terms such as "front", "back", "left", "right", "outer", "inner", "outward", "inward", "up", and "down" should be understood as convenient terms and not as limiting terms.

[0082] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that a component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the component must be completely horizontal, but can be slightly tilted.

[0083] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0084] Example 1

[0085] This embodiment provides a downhole rotatable muon detector 1 (hereinafter referred to as the muon detector), referring to... Figures 1-8 The muon detector 1 includes a housing 11, a first detection unit 12, a second detection unit 13, and a rotation drive unit 14. The outer surface of the housing 11 is adapted to the inner wall of the wellbore. The first detection unit 12 and the second detection unit 13 are arranged relative to each other within the housing 11 at a preset distance. The first detection unit 12 and the second detection unit 13 each include a detection area 15 for receiving muons, and the detection area 15 extends along the central axis of the muon detector 1. The rotation drive unit 14 is disposed at the ends of the first detection unit 12 and the second detection unit 13 and is connected to the first detection unit 12 and the second detection unit 13 in a transmission connection. The rotation drive unit 14 is configured to drive the first detection unit 12 and the second detection unit 13 to rotate synchronously around the central axis by a preset angle, so that the first detection unit 12 and the second detection unit 13 together cover a circumferential direction perpendicular to the central axis during the rotation.

[0086] With this design, the first detection unit 12 and the second detection unit 13 are positioned opposite each other and include a detection area 15 extending along the axial direction. Combined with a rotation drive unit 14, they are driven to rotate synchronously by a preset angle, allowing the two detection units to jointly cover a complete circumferential direction perpendicular to the central axis during rotation. Compared to fixed detectors, this significantly reduces the scintillator unit and downhole space occupied, while also lowering system complexity and cost.

[0087] In one embodiment of the present invention, the first detection unit 12 or the second detection unit 13 respectively includes at least one column of scintillator array 16, and the scintillator array 16 includes a plurality of scintillator units 161 distributed along the axial direction.

[0088] Specifically, in the first detection unit 12 or the second detection unit 13, the detection areas 15 of the scintillator units 161 in all scintillator arrays 16 are coplanar, and the planes containing the detection areas 15 of the first detection unit 12 and the second detection unit 13 are parallel to each other. This can be understood as the plane containing the detection area of ​​each scintillator unit 161 in the first detection unit 12 being parallel to the plane containing the detection area of ​​each scintillator unit 161 in the second detection unit 13. In each detection unit, the rows and columns of the scintillator units 161 are equidistantly arranged in mutually perpendicular X and Y directions, forming a regular grid. Optionally, the outer wall of the scintillator unit 161 is covered with a high-reflectivity layer. Optionally, the scintillator unit 161 is made of plastic, and the high-reflectivity layer 164 is a polytetrafluoroethylene strip or aluminum foil. Optionally, a front-end signal processing board 162 is provided on one side of the scintillator unit 161, and a photomultiplier tube mounting slot is provided for mounting a photomultiplier tube 163. Optionally, the photomultiplier tube is fixed in the photomultiplier tube mounting slot by conductive adhesive or welding.

[0089] With this design, by dividing the scintillator units 161 into at least one column array and making the effective receiving areas of all scintillator units coplanar and the planes of the two detector units parallel, a parallel plate-like structure can be formed, enabling high-efficiency coincidence measurement of muons in a specific direction.

[0090] In another embodiment, refer to Figure 2The first and second detection units have the same structure; the first detection unit 12 is used as an example in the figure. In the first or second detection unit, multiple rows of scintillator arrays 16 are arranged sequentially along the circumference, and the planes containing the detection areas 15 of adjacent rows of scintillator arrays 16 form a preset angle, making the plane containing the detection area 15 of the entire first or second detection unit an arc surface. This arc surface can be understood as an approximate arc surface composed of line segments. The openings of the arc surface detection areas 15 of the first and second detection units are arranged opposite each other. In this case, the central axes of the arc surfaces of the two arc surface detection areas (the first and second detection units) are the same axis, which is the central axis of the muon detector 1.

[0091] With this design, multiple columns are arranged sequentially along the circumference with the planes of adjacent columns containing the detection areas forming a preset angle, creating a relative arc structure. This allows for an expansion of the angular coverage of a single measurement with small-angle rotation, while maintaining a symmetrical arrangement of the two arc surfaces. This improves the detection solid angle within the limited space downhole, enhancing statistical accuracy and imaging resolution.

[0092] In one embodiment of the present invention, the rotary drive unit 14 includes an annular track 141, a first limiting member 142, a second limiting member 143, and a drive mechanism (not shown in the figure). The annular track 141 is disposed on the top and / or bottom of the housing, and the axis of the annular track 141 coincides with the central axis of the muon detector 1. The first limiting member 142 and the second limiting member 143 are respectively fixedly connected to the ends of the first detection unit 12 and the second detection unit 13. The first limiting member 142 can be fixedly connected to the upper end and / or the lower end of the first detection unit 12, and the second limiting member 143 can be fixedly connected to the upper end and / or the lower end of the second detection unit 13. The first limiting member 142 and the second limiting member 143 are respectively in sliding engagement or rolling engagement with the annular track 141. The drive mechanism is configured to drive the first limiting member 142 and the second limiting member 143 to move along the annular track 141, thereby driving the first detection unit 12 and the second detection unit 13 to rotate synchronously.

[0093] Specifically, the drive mechanism can be implemented in any way available in the prior art. For example, the drive mechanism includes a drive motor, a driving gear, and a driven gear ring. The driven gear ring is fixed to the first limiting member 142 or the second limiting member 143 and is concentrically arranged with the annular track 141. The drive motor is mounted on the housing, and its output shaft is connected to the driving gear, which meshes with the driven gear ring. When the motor starts, the driving gear drives the driven gear ring to rotate, thereby driving the first limiting member 142 and the second limiting member 143 to slide synchronously along the annular track 141, realizing the synchronous rotation of the first detection unit 12 and the second detection unit 13.

[0094] Specifically, the first limiting member 142 and the second limiting member 143 have the same structure. The following description focuses on the first limiting member 142. The first limiting member 142 includes a limiting groove 1421 disposed at the bottom or top. The limiting groove 1421 is configured to cooperate with the annular track 141 to restrict the movement trajectory of the first limiting member 142. The first limiting member 142 also includes an outer surface 1422 disposed on its outer periphery. The outer surface 1422 is configured to adapt to the shape of the inner surface of the housing 11. Additionally, the first limiting member 142 includes a detection unit mounting slot 1423 located at the bottom or top for mounting a first detection unit. The detection unit mounting slot 1423 and the limiting groove 1421 are disposed on opposite sides of the first limiting member 142. Similarly, the second limiting member also includes a limiting groove, an outer surface, and a detection unit mounting slot, which will not be elaborated further here. As shown in the figure, the first limiting member 142 and the second limiting member 143 can be two separate structures. In another embodiment, the first limiting member and the second limiting member can also be an integral structure, for example, the portions of the first limiting member and the second limiting member located on the inner peripheral side are connected.

[0095] In one embodiment of the present invention, the muon detector 1 further includes a signal transmission unit and an angle sensor; the signal transmission unit is configured to be connected to an independent readout circuit with each scintillator unit 161 in the first detection unit 12 and the second detection unit 13, for independently acquiring the output signal of the corresponding scintillator array; the angle sensor is configured to acquire the rotation angle information of the first detection unit 12 and the second detection unit 13 in real time.

[0096] In one embodiment of the present invention, the muon detector 1 further includes a processor, which uses the method of embodiment 2 to detect downhole anomalies.

[0097] Example 2

[0098] This embodiment provides a downhole anomaly detection method based on a rotatable muon detector, which includes the following steps:

[0099] From a case involving Muzi, refer to Figure 7 Two representative points of impact were determined when the muon passed through the first and second detection units of the muon detector, and the coordinates of the two representative points of impact in the local coordinate system of the muon detector were recorded.

[0100] Calculate the local zenith angle and local azimuth angle of the muon event in the local coordinate system based on the coordinate difference between the two hit representative points;

[0101] Obtain the rotation angle of the Muon detector around the central axis, and use the rotation angle to transform the local zenith angle and local azimuth angle in the local coordinate system to the world coordinate system to obtain the world zenith angle and world azimuth angle;

[0102] According to the preset zenith angle interval and azimuth angle interval, the world zenith angle and world azimuth angle are binned, each muon event is assigned to the corresponding direction box, and the muon events of each direction box are accumulated and counted during the target body measurement process to obtain the measured count of each direction box.

[0103] Obtain the unobstructed reference measurement count in the same orientation box, and compare the measured count with the unobstructed reference measurement count to obtain the transmittance or transmittance matrix of each orientation box, which can be used for the detection of downhole anomalies.

[0104] Preferably, refer to Figure 1 , Figures 2-8 In this embodiment, the plane containing the detection area of ​​each scintillator unit 161 in the first detection unit 12 of the muon detector is parallel to the plane containing the detection area of ​​each scintillator unit 161 in the second detection unit 13.

[0105] In one embodiment of the present invention, the local coordinate system is set in the following manner:

[0106] With the geometric center of the muon detector as the origin o′, and the direction of the central axis as the z′ axis, which is perpendicular to the ground; two orthogonal directions are set in the horizontal cross-section of the muon detector, namely the x′ axis and the y′ axis, which rotate synchronously with the rotation of the muon detector around the z′ axis.

[0107] In one embodiment of the present invention, the world coordinate system is set in the following manner:

[0108] With the wellhead or downhole reference point as the origin O, the direction perpendicular to the ground as the Z-axis, and the two orthogonal directions in the horizontal plane as the X-axis and Y-axis respectively, the X-axis and Y-axis are fixed, and the z′ axis coincides with the Z-axis.

[0109] In one embodiment of the present invention, two representative hit points are respectively located on the scintillator elements of the scintillator arrays of the first and second detection units, and each representative hit point can be taken as the geometric center of the region of the corresponding scintillator element hit by the muon. (Refer to...) Figure 7 Let the coordinates of the two points representing the hits in the local coordinate system be respectively... and .

[0110] The incident direction in the local coordinate system is calculated based on the coordinate difference between the two representative points of impact.

[0111] First, calculate the coordinate differences between the two hit representative points on the x′, y′, and z′ axes:

[0112] Δx′=x2′-x1′,

[0113] Δy′=y2′-y1′,

[0114] Δz′=z2′-z1′,

[0115] Δx′ and Δy′ are the displacement components of the muon in the horizontal plane, and Δz′ is the displacement component of the muon in the vertical direction.

[0116] Additionally, the direction vector in the local coordinate system is calculated based on the coordinate difference between the two hit representative points. The local direction vector v′ represents the vector pointing from the first hit representative point to the second hit representative point:

[0117] ,

[0118] Expand into component form:

[0119] .

[0120] The three-dimensional spatial distance L′ between two representative points (i.e., the magnitude of the local direction vector) is:

[0121] ,

[0122] L′ represents the actual path length of the muon between the two detector units as it passes through the detector, and is used for subsequent zenith angle calculations.

[0123] The local trajectory line r′(t) describes the flight path of the muon in the local coordinate system, and its parametric equation can be expressed as:

[0124]

[0125] Where t is the trajectory parameter, used to represent the position of any point on the straight line;

[0126] When t=0, it corresponds to the first hit representing point P′1;

[0127] When t=1, it corresponds to the second hit representing point P′2;

[0128] When 0≤t≤1, it represents the trajectory line segment between the two hit representative points;

[0129] When it is necessary to represent the entire straight line of the trajectory of the muon, one can take... ;

[0130] t is not calculated from the zenith angle and azimuth angle, but is merely a parameter of the trajectory equation. Transmittance statistics typically only require directional information and do not require solving for t separately.

[0131] The linear equation fully describes the geometric trajectory of the muon as it passes through the space of the muon detector, but in actual transmission imaging, only directional information is needed, not the complete path.

[0132] The local zenith angle is calculated using the following formula:

[0133] ,

[0134] Where θ′ is the local zenith angle, L′ is the three-dimensional spatial distance between the two representative points of impact, and the value of θ′ ranges from 0° to 90°. When θ′=0°, it indicates that the muon is incident vertically, and when θ′=90°, it indicates that the muon is incident horizontally.

[0135] The local azimuth angle is calculated using the following formula:

[0136] ,

[0137] Where φ′ is the local azimuth angle, and atan2 is the arctangent function in the four quadrants, with a return value range of (-180°, 180°). φ′=0° represents the positive x′ direction, φ′=90° represents the positive y′ direction, and φ′=-90° represents the negative y′ direction. This angle describes the direction of the muon's motion in the horizontal plane.

[0138] In one embodiment of the present invention, the rotation angle γ of the muon detector (specifically, the first detection unit and the second detection unit) around the vertical axis is obtained. γ can be the angle between the local coordinate system x′ axis and the world coordinate system X axis, which is measured in real time by an angle sensor.

[0139] Define a translation vector T, representing the coordinates of the local coordinate system origin o′ in the world coordinate system:

[0140]

[0141] Define the rotation matrix R about the Z-axis. z (γ):

[0142]

[0143] Here, γ is the rotation angle of the muon detector about the vertical axis. Since the rotation axis is vertical, the horizontal component (x′, y′) rotates, while the vertical component (z′) remains unchanged.

[0144] The formula for point coordinate transformation (translation + rotation) is:

[0145]

[0146] Where P′=(x′, y′, z′) is a point in the local coordinate system, and P=(X, Y, Z) is the corresponding point in the world coordinate system.

[0147] The coordinate transformations of the two hit points are as follows:

[0148]

[0149]

[0150] Expanded coordinate components:

[0151] First point:

[0152]

[0153]

[0154]

[0155] Second point:

[0156]

[0157]

[0158]

[0159] The direction vector in the world coordinate system (the flight vector of the Muon in the world coordinate system) is:

[0160]

[0161] Expanded to:

[0162]

[0163] The vector transformation relationship can be simplified to:

[0164]

[0165] in, Let be the direction vector in the local coordinate system, and v be the direction vector in the world coordinate system. This equation shows that the transformation of the direction vector is consistent with the transformation of the point coordinates, both occurring through the rotation matrix R. z (γ) is realized.

[0166] The direction vectors (ΔX, ΔY, ΔZ) in the world coordinate system are obtained through the following rotation transformation:

[0167] ,

[0168] Where γ is the rotation angle of the muon detector about the central axis, and Δx′, Δy′ and Δz′ are the coordinate differences of the two hit representative points on the x′ axis, y′ axis and z′ axis, respectively;

[0169] The world zenith angle is calculated using the following formula:

[0170] ,

[0171] Where θ is the world zenith angle (the angle between the incident direction of the muon and the vertical Z-axis in the world coordinate system), and L is the total path length between the two hit representative points. Since the axis of rotation is vertical, the world zenith angle θ is equal to the local zenith angle θ′.

[0172] The world azimuth is calculated using the following formula:

[0173] ,

[0174] Where φ is the world azimuth (the orientation angle of the muon incident direction relative to the X-axis in the horizontal plane of the world coordinate system), and atan2 is the arctangent function in the four quadrants.

[0175] In one embodiment of the present invention, to further facilitate the binning process, the world azimuth is converted to a continuous range from 0° to 360° to obtain a continuous world azimuth, which is calculated according to the following formula:

[0176] ,

[0177] Where, φ 360 φ represents the continuous world azimuth.

[0178] In one embodiment of the present invention, the world direction is binned according to a preset zenith angle interval Δθ and azimuth angle interval Δφ, and each muon event is assigned to a direction bin (i, j) determined by the zenith angle binning index and the azimuth angle binning index;

[0179] Calculate the zenith angle bin index using the following formula:

[0180] ,

[0181] Where i is the zenith angle bin index, θ is the world zenith angle, Δθ is the zenith angle bin interval, and the value of Δθ ranges from 0 to 90°. How to set it;

[0182] Calculate the azimuth bin index using the following formula:

[0183] ,

[0184] Where j is the azimuth bin index, φ 360 For continuous world azimuth, Δφ is the azimuth box interval, and the value of Δφ ranges from 0 to 360°.

[0185] Preferably, Δθ=3° and Δφ=3°, which can be understood as 30 zenith angle sub-boxes and 120 azimuth angle sub-boxes.

[0186] In one embodiment of the invention, each muon event is determined based on its zenith angle θ and continuous azimuth angles φ. 360 Each target is assigned to a unique orientation box (i, j), and the muon events of that orientation box are accumulated during the target measurement process to obtain the measured count R for each orientation box. target (i, j).

[0187] The formula for calculating the transmittance of the steering box is:

[0188]

[0189] Where τ(i, j) is the transmittance of the direction box, and its value ranges from [0, 1]. τ≈1 indicates that there is no obvious obstruction in this direction; τ<1 indicates that there is anomaly (such as ore body, cavity, etc.) in this direction. The smaller the value, the greater the density or thickness of the anomaly; R target (i, j) represents the measured counts; R open (i, j) represents the unobstructed reference measurement count, preferably, R open (i, j) represents the expected count of the same orientation box in the unobstructed reference measurement; i is the zenith angle box index, and j is the azimuth angle box index.

[0190] In one embodiment of the present invention, the transmittance of all the direction boxes is organized into a transmittance matrix T:

[0191]

[0192] The transmittance matrix T directly reflects the muon attenuation distribution in different directions around the wellbore and is the basic data for downhole anomaly detection.

[0193] In one embodiment of the present invention, a method for detecting downhole anomalies based on the transmittance of each of the orientation boxes includes:

[0194] Pre-set the transmittance threshold;

[0195] When the transmittance of the steering box is greater than the transmittance threshold, it is determined that there is no obvious abnormality in the spatial direction corresponding to the steering box; when the transmittance of the steering box is less than or equal to the transmittance threshold, it is determined that there is an abnormality in the spatial direction corresponding to the steering box.

[0196] For the direction box that is determined to have an anomaly, the anomaly zenith angle and anomaly azimuth angle are inferred from the zenith angle box index and the azimuth angle box index.

[0197] Based on the zenith angle and azimuth angle of the anomalous body, the orientation of the anomalous body relative to the center of the detector is indicated, for example:

[0198] The zenith angle of the anomalous body is θ_a = i × Δθ.

[0199] The azimuth angle of the anomaly is φ_a = j × Δφ, where Δθ is the zenith angle bin interval, Δφ is the azimuth angle bin interval, i is the zenith angle bin index, and j is the azimuth angle bin index.

[0200] In one embodiment of the present invention, the method for detecting downhole anomalies based on a transmittance matrix includes:

[0201] The transmittance matrix is ​​input into the image reconstruction algorithm, which is selected from any one of the filtered back projection algorithm, iterative reconstruction algorithm, or compressed sensing algorithm. The image reconstruction algorithm generates a three-dimensional density distribution image of the anomaly around the well wall, thereby realizing the detection of the downhole anomaly.

[0202] The preferred embodiments of the present invention have been described in detail above. However, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to the present invention. These equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A downhole rotatable muon detector, characterized in that, The muon detector includes a housing, a first detection unit, a second detection unit, and a rotation drive unit; The outer surface of the outer shell is adapted to the inner wall of the well hole; The first detection unit and the second detection unit are spaced at a preset distance and are disposed opposite each other within the housing. The first detection unit and the second detection unit each include a detection area for receiving muons, and the detection area extends along the central axis of the muon detector. The rotation drive unit is disposed at the end of the first detection unit and the second detection unit and is connected to the first detection unit and the second detection unit in a transmission manner. The rotation drive unit is configured to drive the first detection unit and the second detection unit to rotate synchronously around the central axis by a preset angle, so that the first detection unit and the second detection unit together cover the circumferential direction perpendicular to the central axis during the rotation.

2. The muon detector according to claim 1, characterized in that, The first detection unit or the second detection unit each includes at least one column of scintillator array, and the scintillator array includes a plurality of scintillator units distributed along the axial direction; In either the first or the second detection unit, the detection areas of all the scintillator elements in the scintillator array are coplanar, and the planes containing the detection areas of the first and second detection units are parallel to each other. Alternatively, in the first detection unit or the second detection unit, multiple columns of the scintillator arrays are arranged sequentially along the circumference and the planes containing the detection areas of two adjacent columns of the scintillator arrays form a preset angle, so that the plane containing the detection area of ​​the first detection unit or the second detection unit as a whole is set as an arc surface, and the openings of the detection areas of the arc surface of the first detection unit and the second detection unit are set opposite to each other.

3. The muon detector according to claim 1, characterized in that, The rotary drive unit includes a ring track, a first limiting member, a second limiting member, and a drive mechanism. The annular track is disposed at the top and / or bottom of the housing, and the axis of the annular track coincides with the central axis of the muon detector; The first limiting member and the second limiting member are respectively fixedly connected to the ends of the first detection unit and the second detection unit, and the first limiting member and the second limiting member are respectively in sliding engagement or rolling engagement with the annular track; The driving mechanism is configured to drive the first limiting member and the second limiting member to move along the circular track respectively, thereby causing the first detection unit and the second detection unit to rotate synchronously.

4. The muon detector according to claim 3, characterized in that, The muon detector also includes a signal transmission unit and an angle sensor. The signal transmission unit is configured to have an independent readout circuit connected to each scintillator unit in the first and second detection units, for independently acquiring the output signal of the corresponding scintillator array. The angle sensor is configured to acquire rotation angle information of the first detection unit and the second detection unit in real time.

5. A downhole detection method, characterized in that, The method includes the following steps: From a single muon event, two representative points of impact are determined when the muon passes through the first and second detection units of the muon detector, and the coordinates of the two representative points of impact in the local coordinate system of the muon detector are recorded. Based on the coordinate difference between the two representative points of impact, calculate the local zenith angle and local azimuth angle of the muon event in the local coordinate system; Obtain the rotation angle of the muon detector around the central axis, and use the rotation angle to transform the local zenith angle and the local azimuth angle in the local coordinate system to the world coordinate system to obtain the world zenith angle and the world azimuth angle; According to the preset zenith angle interval and azimuth angle interval, the world zenith angle and the world azimuth angle are binned, each muon event is assigned to the corresponding direction box, and the muon events of each direction box are accumulated and counted during the target body measurement process to obtain the measured count of each direction box. Obtain the unobstructed reference measurement count in the same azimuth box, and compare the measured count with the unobstructed reference measurement count to obtain the transmittance or transmittance matrix of each azimuth box for use in the detection of downhole anomalies.

6. The method according to claim 5, characterized in that, The local coordinate system is set in the following manner: With the geometric center of the muon detector as the origin o′, and the direction of the central axis as the z′ axis, and the z′ axis perpendicular to the ground; two orthogonal directions, namely the x′ axis and the y′ axis, are set in the horizontal cross-section of the muon detector, and the x′ axis and the y′ axis rotate synchronously with the rotation of the muon detector around the z′ axis; The world coordinate system is set up as follows: With the wellhead or downhole reference point as the origin O, the direction perpendicular to the ground as the Z-axis, and the two orthogonal directions in the horizontal plane as the X-axis and Y-axis respectively, the X-axis and the Y-axis are fixed, and the z′ axis coincides with the Z-axis.

7. The method according to claim 5, characterized in that, Let the coordinates of the two hit representative points in the local coordinate system be respectively and , The coordinate differences between the two hit representative points on the x′ axis, the y′ axis, and the z′ axis are as follows: Δx′=x2′-x1′, Δy′=y2′-y1′, Δz′=z2′-z1′, The local zenith angle is calculated according to the following formula: ， Where θ′ is the local zenith angle, and L′ is the three-dimensional spatial distance between the two points represented by the hits. The local azimuth angle is calculated according to the following formula: ， Where φ′ is the local azimuth angle.

8. The method according to claim 7, characterized in that, The direction vectors (ΔX, ΔY, ΔZ) in the world coordinate system are obtained through the following rotation transformation: ， Wherein, γ is the rotation angle of the muon detector about the central axis, and Δx′, Δy′ and Δz′ are the coordinate differences of the two hit representative points on the x′ axis, the y′ axis and the z′ axis, respectively; The zenith angle is calculated according to the following formula: ， Where θ is the world zenith angle, and L is the total path length between the two hit representative points. ; The world azimuth is calculated according to the following formula: ， Where φ is the world azimuth.

9. The method according to claim 8, characterized in that, The world azimuth angle is converted to a continuous range from 0° to 360° to obtain a continuous world azimuth angle, which is calculated according to the following formula: ， Where, φ 360 φ represents the continuous world azimuth angle. Each of the aforementioned muon events is assigned to a direction box (i,j) determined by the zenith angle binning index and the azimuth angle binning index; Calculate the zenith angle bin index using the following formula: ， Where i is the zenith angle bin index, θ is the world zenith angle, and Δθ is the zenith angle bin interval; Calculate the azimuth bin index using the following formula: ， Where j is the azimuth bin index, φ 360 For continuous world azimuth, Δφ is the azimuth box interval.

10. The method according to claim 5, characterized in that, The method for detecting downhole anomalies based on the transmittance of each of the aforementioned orientation boxes includes: Pre-set the transmittance threshold; When the transmittance of the steering box is greater than the transmittance threshold, it is determined that there is no obvious abnormality in the spatial direction corresponding to the steering box; when the transmittance of the steering box is less than or equal to the transmittance threshold, it is determined that there is an abnormality in the spatial direction corresponding to the steering box. For the direction box that is determined to have an anomaly, the anomaly zenith angle and the anomaly azimuth angle are reversed based on the zenith angle sub-box index and the azimuth angle sub-box index. The zenith angle and azimuth angle of the anomalous body are used to indicate the orientation of the anomalous body relative to the center of the detector.

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