阅读说明：本技术 用于从井孔进行地层评估的系统和方法 (System and method for formation evaluation from a wellbore ) 是由 迪巴舍希·萨卡尔 迈克尔·罗斯·韦尔斯 斯图尔特·布雷克·巴西 詹姆斯·维娜·莱格特 于 2018-05-09 设计创作，主要内容包括：一种被配置成延伸穿过钻孔的井下测量工具包括源和三分量接收器。所述源被配置成将源信号发射到所述钻孔周围的一定体积的材料中,所述源信号可以是压缩波或剪切波。所述源信号传播通过所述钻孔周围的所述一定体积的材料并且从设置于所述钻孔周围的所述一定体积的材料内的特征反射离开。所述三分量接收器包括第一元件、第二元件和第三元件。所述第一元件定向在与所述钻孔的轴线正交的第一平面中并且接收所述源信号的反射组的第一分量。所述第二元件与所述第一元件正交地定向在所述第一平面中并且接收所述源信号的所述反射组的第二分量。所述第三元件与所述轴线平行地定向并且接收所述源信号的所述反射组的第三分量。(A downhole measurement tool configured to extend through a borehole includes a source and a three-component receiver. The source is configured to emit a source signal, which may be a compressional wave or a shear wave, into a volume of material surrounding the borehole. The source signal propagates through the volume of material surrounding the borehole and reflects off of a feature disposed within the volume of material surrounding the borehole. The three-component receiver includes a first element, a second element, and a third element. The first element is oriented in a first plane orthogonal to an axis of the borehole and receives a first component of the reflected set of source signals. The second element is oriented in the first plane orthogonal to the first element and receives a second component of the reflected set of the source signals. The third element is oriented parallel to the axis and receives a third component of the reflection set of the source signal.)

1. A downhole measurement tool configured to extend through a borehole, the downhole measurement tool comprising:

a source configured to emit a source signal into a volume of material surrounding the borehole, wherein the source signal is configured to propagate through the volume of material surrounding the borehole and reflect off of a feature disposed within the volume of material surrounding the borehole; and

a three-component receiver, the three-component receiver comprising:

a first element oriented in a first plane orthogonal to an axis of the borehole, wherein the first element is configured to receive a first set of reflections of the source signal;

a second element oriented orthogonally to the first element in the first plane, wherein the second element is configured to receive a second set of reflections of the source signal; and

a third element oriented parallel to the axis, wherein the third element is configured to receive a third set of reflections of the source signal.

2. The downhole measurement tool of claim 1, wherein the source is configured to transmit the source signal along a second plane perpendicular to the borehole axis.

3. The downhole measurement tool of claim 1, wherein the first and second sets of reflections include a compressional component (P) of the source signal and a second shear component (S2) of the source signal.

4. The downhole measurement tool of claim 3, wherein the third set of reflections includes a first shear component of the source signal (S1).

5. The downhole measurement tool of claim 1, wherein the three-component receiver comprises a three-axis magnetoresistive sensor.

6. The downhole measurement tool of claim 1, wherein the three-component receiver comprises one or more geophones.

7. The downhole measurement tool of claim 1, wherein the three-component receiver comprises one or more accelerometers.

8. A system, the system comprising:

a downhole measurement tool configured to extend through a borehole, the downhole measurement tool comprising:

a source configured to emit a source signal into a volume of material surrounding the borehole, wherein the source signal is configured to propagate through the volume of material surrounding the borehole and reflect off of a feature disposed within the volume of material surrounding the borehole;

a three-component receiver, the three-component receiver comprising:

a first element oriented in a first plane orthogonal to an axis of the borehole, wherein the first element is configured to receive a first set of reflections of the source signal;

a second element oriented orthogonally to the first element in the first plane, wherein the second element is configured to receive a second set of reflections of the source signal; and

a third element oriented parallel to the axis, wherein the third element is configured to receive a third set of reflections of the source signal;

wherein the downhole measurement tool is configured to acquire the received first, second, and third sets of reflections of the source signal; and

a computing device configured to analyze the received first, second, and third sets of reflections of the source signal and generate one or more images of the volume of material surrounding the borehole based on the first, second, and third sets of reflections of the source signal.

9. The system of claim 8, wherein the third set of reflections includes a first shear component of the source signal (S1).

10. The system of claim 9, wherein the first set of reflections and the second set of reflections include a compressional component (P) of the source signal and a second shear component (S2) of the source signal.

11. The system of claim 8, wherein the three-component receiver comprises a three-axis magnetoresistive sensor.

12. The system of claim 8, wherein the one or more images of the volume of material around the borehole comprise one or more 3D images.

13. The system of claim 12, wherein the computing device is configured to determine the orientation and tilt based on the one or more 3D images.

14. The system of claim 8, wherein the one or more images of the volume of material around the borehole comprise one or more 2D images.

15. The system of claim 14, wherein the computing device is configured to estimate strike and dip based on the one or more 2D images.

16. A method, the method comprising:

extending a downhole measurement tool through the borehole;

transmitting, via a source of the downhole measurement tool, a source signal into a volume of material surrounding the borehole, wherein the source signal is configured to propagate through the volume of material surrounding the borehole and reflect off of a feature disposed within the volume of material surrounding the borehole;

receiving a first set of reflections of the source signal via a first element of a three-component receiver, wherein the first element is oriented in a first plane orthogonal to an axis of the borehole;

receiving a second set of reflections of the source signal via a second element of the three-component receiver, wherein the second element is oriented orthogonally to the first element in the first plane; and

receiving a third set of reflections of the source signal via a third element of the three-component receiver, wherein the third element is oriented parallel to the axis.

17. The method of claim 16, comprising generating one or more 3D images of the volume of material around the borehole based on the first, second, and third sets of reflections of the source signals.

18. The method of claim 17, comprising determining a strike and a dip based on the one or more 3D images.

19. The method of claim 16, comprising generating one or more 2D images of the volume of material around the borehole based on the first, second, and third sets of reflections of the source signals.

20. The method of claim 19, comprising estimating strike and dip based on the one or more 2D images.

Background

The subject matter disclosed herein relates to subsurface formation evaluation, and more particularly, to evaluating geological formations disposed about a hydrocarbon extraction wellbore.

The underground reservoir may be accessed by drilling a borehole extending from the surface to the reservoir and then pumping the hydrocarbons up to the surface via the borehole. In some applications, after a borehole has been drilled, a measurement tool may be extended through the borehole to make measurements of the borehole or a ground disposed immediately surrounding the borehole. However, because such systems are designed to measure formation properties along the axis of the wellbore, such systems are not suitable for evaluating formations further from the wellbore. Formation evaluation methods that rely on elastic wave propagation typically focus on reflected waves propagating along the wall of the borehole and other wave modes propagating along its axis within the borehole. Micro-fracture planes and macro-fracture planes extending tens of meters away from the wellbore cannot be studied using such conventional tools and methods. It would be beneficial to design a measurement tool that is capable of detecting both small and large fractures extending tens of meters away from a well bore that can be used as a reservoir or path for hydrocarbons.

Disclosure of Invention

Certain embodiments having a scope consistent with the original claims are summarized below. These embodiments are not intended to limit the scope of the claims, but rather these embodiments are intended only to provide a brief summary of possible forms of the claimed subject matter. Indeed, the claims may encompass a variety of forms that may be similar to or different from the embodiments set forth below.

In one embodiment, a downhole measurement tool configured to extend through a borehole includes a source and a three-component receiver. The source is configured to emit a source signal, which may be a compressional wave or a shear wave, into a volume of material surrounding the borehole. The source signal propagates through the volume of material surrounding the borehole and reflects off of a feature disposed within the volume of material surrounding the borehole. The three-component receiver includes a first element, a second element, and a third element. The first element is oriented in a first plane orthogonal to an axis of the borehole and receives a first component of the reflected set of source signals. The second element is oriented in the first plane orthogonal to the first element and receives a second component of the reflected set of the source signals. The third element is oriented parallel to the axis and receives a third component of the reflection set of the source signal.

In a second embodiment, a system includes a downhole measurement tool and a computing device. The downhole measurement tool extends through a borehole and includes a source and a three-component receiver. The source emits a source signal into a volume of material surrounding the borehole. The source signal propagates through the volume of material surrounding the borehole and reflects off of a feature disposed within the volume of material surrounding the borehole. The three-component receiver includes a first element, a second element, and a third element. The first element is oriented in a first plane orthogonal to an axis of the borehole and receives a first component of the reflected set of source signals. The second element is oriented in the first plane orthogonal to the first element and receives a second component of the reflected set of the source signals. The third element is oriented parallel to the axis and receives a third component of the reflection set of the source signal. The downhole measurement tool acquires a first, second, and third set of received components of the reflection of the source signal. The computing device analyzes the received first, second, and third components of the transmitted set of source signals for formation evaluation and generates one or more images of the volume of material surrounding the borehole based on the first, second, and third components of the reflected set of source signals.

In a third embodiment, a method comprises: extending a downhole measurement tool through the borehole; transmitting, via a source of the downhole measurement tool, a source signal into a volume of material surrounding the borehole, wherein the source signal is configured to propagate through the volume of material surrounding the borehole and reflect off of a feature disposed within the volume of material surrounding the borehole; receiving a reflected first component set of the source signal via a first element of a three-component receiver, wherein the first element is oriented in a plane orthogonal to an axis of the borehole; receiving a reflected second component set of the source signal via a second element of the three-component receiver, wherein the second element is oriented orthogonally to the first element in the first plane; and receiving a third set of components of reflections of the source signal via a third element of the three-component receiver, wherein the third element is oriented parallel to the borehole axis.

Drawings

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

fig. 1 is a schematic diagram of a mineral extraction system according to one embodiment;

FIG. 2 is a graphical representation of a signal propagating through an isotropic material according to one embodiment;

FIG. 3 is a graphical representation of birefringence in an anisotropic material according to an embodiment;

fig. 4 is a schematic view of a measurement tool disposed within a borehole of the mineral extraction system of fig. 1, according to one embodiment;

FIG. 5 is an illustration of various planes for 2D imaging after data is collected, according to one embodiment;

fig. 6 is a flow diagram of a process for measuring and generating a 3D image of a volume surrounding a borehole of the mineral extraction system of fig. 1, according to one embodiment; and

fig. 7 is a flow diagram of a process for measuring and generating a 2D image of a volume around a borehole of the mineral extraction system of fig. 1, according to one embodiment.

Detailed Description

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present disclosure, the articles "a," "an," "said," and "the" are intended to mean that there are one or more of the elements. The terms "comprising," "including," and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus additional values, ranges, and percentages are within the scope of the disclosed embodiments.

The disclosed technique includes utilizing a measurement tool that includes a source and a three-component receiver. The source emits a signal outwardly into material surrounding the borehole as the measurement tool moves through the borehole. The signal reflects off a feature in the material and returns toward the borehole. The receiver receives a compression component and two shear components of a reflected signal. The collected data may be used to generate 2D and 3D images of the material surrounding the borehole for performing formation evaluation.

Fig. 1 is a schematic diagram of an embodiment of a mineral extraction system 10. Oil and/or gas may be accessed from the underground deposit 12 via the oil well 14. For example, a drilling tool 17 (e.g., a drill bit) may be used to drill a borehole 16 extending from the surface 18 to the deposit 12. Although borehole 16 is shown in fig. 1 as extending vertically from rig 19 at surface 18 to deposit 12, borehole 16 may extend at any angle of inclination to surface 18. Similarly, the borehole 16 may change direction as it extends from the surface 18 to the deposit 12. That is, borehole 16 may include a portion that extends obliquely, vertically, or parallel relative to ground surface 18. A measurement tool 20 may be inserted into the borehole 16 behind the drilling tool 17 to measure or image a volume of material 21 surrounding the borehole 16 for formation evaluation. The measurement tool 20 may extend down the borehole 16 behind the drilling tool 17 and make measurements while drilling the borehole 16 (logging while drilling or LWD). In other embodiments, the measurement tool 20 may extend down the borehole 16 after the borehole 16 has been drilled, and measurements are taken (wireline logging) when the measurement tool 20 has been pulled back up through the borehole 16 (e.g., withdrawn from the borehole). In other embodiments, measurement tool 20 may extend down borehole 16 after borehole 16 has been drilled and make measurements while pipe is being removed from borehole 16 (logging while tripping, LWT) when measurement tool 20 has been pulled back up through borehole 16.

The measuring tool 20 may comprise: one or more sources 22 that emit signals that propagate through the earth; and one or more receivers 24 that receive signals reflected off of features 26 (e.g., planar features, microfractures, faults, layers, and other scatterers) within the volume of material 21 surrounding borehole 16. The data collected using the measurement tool 20 may be analyzed using a computing device 28 (e.g., a computer, tablet, mobile device, etc.) or a combination thereof. Computing device 28 may include communication circuitry 30, processor 32, memory 34, communication port 36, and user interface 38, which may include display 40. While the measurement tool 20 is being passed through the borehole 16 to make a measurement or after the measurement tool 20 has been passed through the borehole 16, the data may be passed to a memory component 42 (e.g., via a cable 44) for storage until the data is processed, which may be located at the surface 18 or within the measurement tool 20. In other embodiments, the collected data may be communicated to computer 28 wirelessly (e.g., via cloud 46) or through a wired connection via communication port 36. The computer 28 may be located near the rig 19 or remotely from the well 14. In some embodiments (e.g., the computer 28 is located remotely from the well 14), the data may be transferred to the computer 28 via the cloud 46 or over a network. In other embodiments, the computer 28 may communicate wirelessly with the measurement tool 20 as the measurement tool 20 is traveling through the borehole 16 and analyzing the data in real time or near real time. In some embodiments, the operation of the measurement tool 20 may be adjusted based on analysis performed by the computing device 28 (e.g., dynamic software). The computer 28 may be equipped with software stored on the memory component 34 and executed by the processor 32 to facilitate analysis of the collected data. For example, computing device 28 may be capable of post-processing data collected by measurement tool 20 and identifying features 26 in a volume of material 21 surrounding borehole 16. Based on the reflected signals received by receiver 24, 2D and 3D imaging of a volume of material 21 around borehole 16 may be performed.

Fig. 2 is a graphical representation of a signal 100 propagating through an isotropic material. As shown, the signal includes a compression component P and a shear component S. The compression component P extends axially along the travel axis 102. The shear component S acts orthogonally to the axis of travel 102. In the illustrated embodiment, the shear component S is oriented along the axis 104. However, it should be understood that the shear component S may be oriented along the axis 106 or in any other direction. As signal 100 propagates through the anisotropic or birefringent material, the shear component splits into a first shear component S1 and a second shear component S2, which are generally orthogonally polarized to each other along a given ray path in the subsurface earth formation.

FIG. 3 is a graphical representation of shear signal splitting in an anisotropic material. As shown, the signal propagates through the homotropic material 108, passes through the anisotropic material 110, and then exits the anisotropic material 110 back into the isotropic material 108. As shown and described with respect to fig. 2, the signal propagates through the isotropic material 108 as a single signal having a pressure component P and a shear component S, which is oriented entirely along the plane 109 as the single signal 100. The signal 100 contacts the front plane 112 of the anisotropic material 110 and the shear component S splits into two polarization components S1 and S2 because the refractive index of the anisotropic material 100 depends on the polarization of the signal 100. The first shear component S1 polarized around the first plane 114 propagates at a first velocity according to the first refractive index of the anisotropic material 110, and the second shear component S2 polarized around the second plane 116 propagates at a second velocity according to the second refractive index of the anisotropic material 110. The first shear component S1 and the second shear component S2 reach the back plane 118 of the anisotropic material 110 at different times and exit the anisotropic material 110 into the isotropic material 108. Thus, the shear component S of the signal 100 at the beginning is received by the receiver 24 as a first shear component S1 and a second shear component S2, the first and second shear components arriving at different times.

If the medium is isotropic, the received shear wave is polarized in the propagation plane containing the reflection point. To fully capture such arrivals, receivers oriented in the axial direction are used. Note that conventional cross-dipole geometries do not record this component of the wavefield. When stress, planar fissures, micro-fissures are present in a volume of material 21 surrounding the borehole 16, as shown in FIG. 1, the volume of material 21 becomes anisotropic and birefringent. Thus, a signal 100 emitted by one or more sources 22, reflected by a feature 26 in the volume 21, and received by one or more receivers 24 will be split into a pressure compression component P and first and second shear components S1 and S2 arriving at different times. Thus, using a 3-component receiver to receive the entire wave pattern of the reflected signals P, S1, S2 and capture it results in the most complete formation evaluation of a volume of material 21 surrounding the borehole 16.

FIG. 4 is a schematic view of the measurement tool 20 of FIG. 1 disposed within the borehole 16, according to one embodiment. For purposes of illustration, an axis 200 of borehole 16 is shown. Although bore 16 is shown in fig. 4 as extending vertically, it should be understood that bore 16 may extend horizontally or at any oblique angle to ground 18. Similarly, as bore 16 changes direction, bore axis 200 also changes direction. The X, Y, Z coordinate system is also shown in fig. 4. For simplicity, it will be appreciated that the coordinate system also reflects changes in the direction of borehole 16, such that borehole axis 200 extends in the Z direction at all times.

As shown, the measurement tool 20 includes a source 22 and a receiver 24. As previously discussed, the measurement tool 20 may include a plurality of sources 22 and a plurality of receivers 24. Similarly, the source 22 and the receiver may be part of the same module or component, or part of separate modules or components. Source 22 may be any device that may be electrically or mechanically excited to outwardly generate compression or shear waves into a volume of material 21 surrounding borehole 16. Fig. 4 shows a specific example of a source that is typically used in a cross-dipole geometry. However, other multimode systems with 4, 6, 8 or more poles may also be possible. Here, the source emits a signal into a volume of material 21 surrounding the borehole 16 in a plane parallel to the XY plane and orthogonal to the borehole axis 200, as indicated by arrows 202 and 204. However, source 22 may be any number of devices capable of transmitting a signal into a volume of material 21 surrounding borehole 16. For example, source 22 may be any source of vibration that may be electrically or mechanically activated to produce compression and shear waves. The source 22 may operate, for example, as a monopole, a dipole, or both. The signal penetrates deeply (e.g., 30 meters, 40 meters, or 50 meters or more) into a volume of material 21 surrounding the borehole 16, such that fractures having various sizes can be detected. For example, the signal may have a frequency greater than 1 KHz.

Receiver 24 is a sensor capable of receiving P, S1 and S2 components of the reflected signal. For example, receiver 24 may have first and second elements, indicated by arrows 206 and 208, respectively, oriented in planes parallel to the XY plane and orthogonal to borehole axis 200. A third element, indicated by arrow 210, may be oriented parallel to the borehole axis 200. As previously discussed with respect to fig. 2, the P-component of the reflected signal travels along the propagation axis. For isotropic media, the shear component S is polarized in the plane of propagation. For anisotropic media, the shear wave splits into two polarization components, S1 and S2. Thus, first element 206 and second element 208 oriented in a plane orthogonal to borehole axis 200 primarily receive the P and S2 components of the reflected signal. The third element 210, oriented parallel to the borehole axis 200, receives the S1 component. In some embodiments, receiver 24 may be a three-component (3C) sensor (e.g., a three-axis magnetoresistive sensor, a piezoelectric sensor, a magnetoresistive, a capacitive sensor, a MEMS sensor, etc.). In other embodiments, the receiver 24 may include one or more geophones or accelerometers. In addition, receiver 24 may include multiple sensors in a single package or in separate packages. As previously discussed, while the measurement tool 20 shown in FIG. 4 has a single source 22 and a single receiver 24, it should be understood that embodiments having multiple sources 22, multiple receivers 24, or a combination thereof are also contemplated.

Measurement tool 20 may extend through borehole 16 to measure a volume of material 21 surrounding borehole 16. The measurements may be taken as the measurement tool 20 moves through the borehole 16 toward the reservoir and away from the surface, or as the measurement tool 20 moves through the borehole 16 toward the surface and away from the reservoir. The data acquisition may be continuous as the measurement tool 20 moves through the borehole 16, or the data acquisition may occur at discrete locations as the measurement tool 20 moves through the borehole 16. As discussed with respect to fig. 1, the analysis of the collected data may be performed in real-time or near real-time on a measurement tool, or the data may be collected and communicated to an external computing device for analysis.

Existing systems typically transmit signals using a cross-dipole source (i.e., two dipole antennas positioned orthogonally to each other) and using a two-component receiver having two elements aligned in a plane orthogonal to the borehole axis 200. As a result, the two-component receiver receives only the P and S2 components of the reflected signal. The S1 component is not fully captured, which travels perpendicular to the borehole axis 200 and is polarized in a plane parallel to the borehole axis 200 and is the most dominant arrival in most cases. Thus, the effective measurement direction is only along the borehole axis 200, and measurements can only be made over a range of a few meters into the volume of material 21 surrounding the borehole 16. Utilizing a three-component receiver 24 as shown in fig. 3 allows the measurement tool 20 to capture all three components of the reflected signal (i.e., P, S1 and S2) such that the effective measurement direction is along the borehole axis 200 and radially outward from the borehole axis 200, enabling formation evaluation deep into the volume of material 21 surrounding the borehole 16. For example, using the disclosed techniques, formation evaluation may be performed over a distance of up to 50 meters or more into a volume of material 21 surrounding borehole 16. Once the data is collected by the measurement tool 20, a 2D or 3D image may be generated for a volume of material 21 surrounding the borehole 16.

For a cross-dipole source, fig. 5 shows various planes for 2D imaging after data is collected. While 3D imaging provides a better quality image of a volume of material 21 surrounding a borehole, 3D imaging may cost more processing power than 2D imaging. Thus, in some embodiments (e.g., when processing power is limited), 2D imaging may be performed prior to or in place of 3D imaging. As shown, the borehole 16 and borehole axis 200 extend along a line at the intersection of the XZ plane 300 and the YZ plane 302. The XY plane 304 extends outward orthogonal to the borehole axis 200. As described with respect to figure 4 of the drawings,it should be understood that as borehole 16 changes direction, borehole axis 200 and the coordinate system also change direction. In some embodiments, the measurement tool 20 may include a gyroscope or other sensor to help determine the orientation of the measurement tool. As shown, the source 22 emits a signal in a plane orthogonal to the borehole axis 200 and parallel to the XY plane, which may be split into its component parts S_yAnd S_x. Receiver 24 receives the reflected signal in three axes such that the received signal can be split into its component parts R_x、R_yAnd R_z. The received signal may also be split based on the components of its corresponding source 22 signal. That is, R_xThe component may be split into S_xR_xAnd S_yR_x，R_yThe component may be split into S_xR_yAnd S_yR_yAnd R is_zThe component may be split into S_xR_zAnd S_yR_z. Each of these components may correspond to the compression component P and the shear component S1, S2 of the reflected signal. For example, for the XZ plane, the P image corresponds to S_xR_xThe S1 image corresponds to S_xR_zAnd the S2 image corresponds to S_yR_y. For the YZ plane, the P image corresponds to S_yR_yThe S1 image corresponds to S_yR_zAnd the S2 image corresponds to S_xR_x。

The strike is defined as the angle of the azimuth of the plane of the detected feature relative to the borehole. Dip is the angle that the detected feature makes with respect to the borehole. Based solely on the 2D images described above for the XZ plane and the YZ plane, the values of the trend and the tilt angle of the detected features may not be determined. However, by mixing S_xR_yAnd S_yR_xTaking into account the values, the trend and the dip can be estimated.

Fig. 6 is a flow chart of a process 400 for measuring a volume surrounding a borehole and generating a 3D image. In block 402, a signal is emitted from a source of a measurement tool. As previously discussed, the source may transmit a signal into a volume of material surrounding the borehole (i.e., a cross dipole) in a plane parallel to the XY plane and orthogonal to the borehole axis. In other embodiments, the source may be any device that generates compression and shear waves via an electrical or mechanical excitation process. The source may be any number of devices capable of emitting a signal into a volume of material surrounding the borehole. The source may be capable of operating, for example, as a monopole, a dipole, or both. The signal penetrates deeply (e.g., 30 meters, 40 meters, or 50 meters or more) into a volume of material surrounding the borehole, such that fractures having various sizes can be detected. For example, the signal may be transmitted at an appropriate frequency such that the signal penetrates deep into a volume of material surrounding the borehole.

In block 404, a receiver receives a signal reflected from a feature within a volume of material disposed around a borehole. The receiver houses one or more sensors capable of receiving the P, S1 and S2 components of the reflected signal. For example, the receiver may have first and second elements oriented in a plane parallel to the XY plane and orthogonal to the borehole axis. The third element may be oriented coaxially or parallel to the bore axis. The P component of the reflected signal travels along the propagation axis, the S1 component is polarized in the plane of propagation for isotropic media, and the S2 component is polarized perpendicular to the plane of propagation. Thus, the first and second elements oriented in a plane orthogonal to the borehole axis receive the P and S2 components of the reflected signal. A third element oriented parallel to the bore axis receives the S1 component. For anisotropic materials, the appropriate components of the P, S1 and S2 modes are completely registered by the three components of the receiver. In some embodiments, the receiver may be a three-component (3C) sensor (e.g., a three-axis magnetoresistive sensor, a piezoelectric sensor, a magnetoresistive, a capacitive sensor, a MEMS sensor, etc.). In other embodiments, the receiver may include one or more geophones or accelerometers. In general, the receiver may be any device capable of sensing a vector quantity (such as force, velocity, acceleration, displacement, etc.). In addition, the receiver may include multiple sensors in a single package or in separate packages. In some embodiments, block 404 may include some signal conditioning, such as filtering, Fast Fourier Transform (FFT), and the like.

In block 406, one or more 3D images 408 are generated and output using the collected data. As discussed with respect to FIG. 5, the source may emit a signal in a plane orthogonal to the borehole axis and parallel to the XY plane, which may be split into its component parts S_yAnd S_x. The receiver receives the reflected signal in three axes such that the received signal can be split into its component parts R_x、R_yAnd R_z. The received signal may also be split based on the components of its corresponding source signal. That is, R_xThe component may be split into S_xR_xAnd S_yR_x，R_yThe component may be split into S_xR_yAnd S_yR_yAnd R is_zThe component may be split into S_xR_zAnd S_yR_z. Each of these components may correspond to the compression component P and the shear component S1, S2 of the reflected signal. By combining various components (S)_xR_x、S_yR_x、S_xR_y、S_yR_y、S_xR_zAnd S_yR_z) Stitching together and analyzing the collected data may produce images of various features disposed within a volume of material surrounding the borehole and extending 50 meters or more outward.

In block 410, a trend 412 and a dip 414 may be determined and output. As previously discussed with respect to FIG. 5, strike is defined as the angle of the azimuth of the plane of the detected feature relative to the borehole, and dip is the angle of the detected feature relative to the borehole. Once an image 408 of the volume surrounding the borehole has been generated, the values of the trend 412 and the dip 414 can be directly determined from one or more of the images 408 and output.

While 3D images allow for more thorough, complete formation evaluation and more accurate strike and dip values, 3D imaging may use more processing power and take more time than 2D imaging. Thus, in some applications, the user may prefer 2D imaging, or 2D imaging may be performed as a preliminary step prior to 3D imaging.

Fig. 7 is a flow chart of a process 500 for measuring a volume surrounding a borehole and generating a 2D image. In block 502, a signal is emitted from a source of a measurement tool. As previously discussed, the source may emit signals into a volume of material surrounding the borehole in a plane parallel to the XY plane and orthogonal to the borehole axis. However, the source may be any number of other devices capable of transmitting a signal into a volume of material surrounding the borehole. The source may be capable of operating as a monopole, dipole, 4 pole, 6 pole, 8 pole, etc. The signal penetrates deeply (e.g., 30 meters, 40 meters, or 50 meters or more) into a volume of material surrounding the borehole, such that fractures having various sizes can be detected. For example, the signals may be emitted at appropriate frequencies to resolve a fracture target and with sufficient intensity to probe deep formations.

In block 504, a receiver receives a signal reflected from a feature within a volume of material disposed around a borehole. The receiver houses one or more sensors capable of receiving the P, S1 and S2 components of the reflected signal. For example, the receiver may have first and second elements oriented in a plane parallel to the XY plane and orthogonal to the borehole axis. The third element may be oriented coaxially or parallel to the bore axis. The P component of the reflected signal travels along the propagation axis, in isotropic media the S1 component is polarized in the plane of propagation, and the S2 component is polarized perpendicular to the plane of propagation. Thus, the first and second elements oriented in a plane orthogonal to the borehole axis receive the P and S2 components of the reflected signal. A third element oriented parallel to the bore axis receives the S1 component. For anisotropic materials, the appropriate components of the P, S1 and S2 modes are fully recorded on the three components of the receiver. In some embodiments, the receiver may be a three-component (3C) sensor (e.g., a three-axis magnetoresistive sensor, a piezoelectric sensor, a magnetoresistive, a capacitive sensor, a MEMS sensor, etc.). In other embodiments, the receiver may include one or more geophones or accelerometers. In addition, the receiver may include multiple sensors in a single package or in separate packages. In some embodiments, block 504 may include some signal conditioning, such as filtering, Fast Fourier Transform (FFT), and the like.

In block 506, the collected data is split into data for the up-shift signal and the down-shift signal. The data for the up-shift signal and the down-shift signal are used separately to generate images and then combined to give a complete picture.

In block 508, a 2D image is generated and output for the XZ plane 510 and the YZ plane 512. Using S_xR_x、S_xR_zAnd S_yR_yThe data generates an image of the XZ plane 510. In the XZ plane image, the P component corresponds to S_xR_xThe S1 component corresponds to S_xR_zAnd the S2 component corresponds to S_yR_y. Using S_yR_y、S_yR_zAnd S_xR_xThe data generates an image of the YZ plane 512. The P component corresponds to S_yR_yThe S1 component corresponds to S_yR_zAnd the S2 component corresponds to S_xR_x。

In block 514, the trend 412 and the inclination 414 may be determined. Based solely on the 2D images described above for the XZ plane and the YZ plane, the values of the trend 412 and the tilt 414 of the detected features may not be determined. However, by mixing S_xR_yAnd S_yR_xTaking the values into account, the trend 412 and the dip 414 can be estimated and output.

The disclosed techniques utilize at least one source and at least one three-component receiver to make a formation evaluation of a volume of material disposed about a borehole and extending 50 meters or more outward. By sensing the compression component P and the two shear components S1 and S2, 2D and/or 3D images of the volume can be generated, allowing for estimation of birefringence of the volume and detection of microcracks several orders of magnitude below the resolution scale. The source may operate in a monopole mode or in multiple modes (i.e., dipole, quadrupole, hexapole, octopole, etc.). Additionally, the disclosed measurement tools and corresponding techniques may be used in cased and/or open boreholes. Additionally, the disclosed measurement tools may be used during tripping Logging (LWT), Logging While Drilling (LWD), Measuring While Drilling (MWD), or wireline operations.

This written description uses examples to disclose the claimed subject matter, including the best mode, and also to enable any person skilled in the art to practice the disclosed subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the disclosure is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.