Systems and methods for downhole imaging through a scattering medium

Abstract

The present invention discloses a system for downhole optical imaging. The system includes a housing (208) that forms at least a part of a tool string (112). The system further includes a source (212) disposed within the housing (208), the source (212) emitting light through a window (210) formed in the housing (208). The system also includes an imager (214) disposed within the housing (208), the imager (214) receiving imaging data through the window (210). The system further includes a control system (504) communicatively coupled to the imager (214), the control system (504) using one or more algorithms to process the image data, the one or more algorithms modifying the imaging data at least in part based on a scattering material (218) surrounding the housing (208).

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit and priority of co - pending U.S. Patent Application Serial No. 16 / 557,018, filed on August 30, 2019, entitled "SYSTEMS AND METHODS FOR DOWNHOLE IMAGING THROUGH A SCATTERING MEDIUM", the entire disclosure of which is incorporated herein by reference for all purposes. Background Art 1. Technical Field

[0004] This disclosure generally relates to oil and gas tools, and more particularly to systems and methods for downhole optical imaging applications through wellbore fluids that may include particles or fluids.

[0005] 2. Description of the Prior Art

[0006] In oil and gas production, various tools and techniques can be utilized in downhole imaging to provide information for determining one or more characteristics of a wellbore. For example, different imaging techniques, such as acoustic, electromagnetic, nuclear, etc., can be used to determine different properties, such as resistivity, permeability, etc. Different downhole imaging techniques can offer various advantages and disadvantages related to aspects such as cost, resolution, and time. Additionally, the deployment difficulty can vary between different techniques. For example, while optical imaging techniques have much better spatial resolution and image quality than non - optical techniques, it may be difficult to deploy optical techniques in a wellbore due to pressure, temperature, and the overall environment. In various embodiments, the wellbore can be filled with a fluid (e.g., gas, liquid, solid, or a combination thereof) that can attenuate or scatter light and pose difficulties for downhole optical methods. The resolution of typical acoustic or electrical borehole imaging tools is about 2.5 mm to 5 mm, while the resolution achievable by processing optical images obtained through a scattering medium can be approximately 34 microns, which is 75 to 150 times better.

[0007] Historically, downhole optical wellbore imaging has utilized one of three main techniques: 1) pressing a transparent optical window (or fiber optic) against the borehole wall as a mud excluder to exclude the highly scattering drilling mud; 2) replacing the drilling mud with a transparent fluid on the section of the wellbore wall to be optically imaged; and 3) using infrared light to see through the dark asphaltenes of crude oil. However, each of these techniques has drawbacks, and none of them provides a means to reconstruct an image taken through a light-scattering medium such as a borehole fluid containing suspended solid particles, bubbles, or liquid-liquid emulsions. For example, the mud excluder may be difficult to fix tightly against the borehole wall. For example, with wireline applications, additional anchors may be required to push the window or fiber tightly against the wellbore to achieve maximum mud exclusion. Additionally, with respect to the transparent fluid, it may be difficult to position the transparent fluid slug at the desired depth in the well, and this can also disrupt wellsite operations. By scattering suspended particles in wellbore fluids such as drilling mud, the light is also highly attenuated. Such scattering can easily reduce the light intensity by a factor of 100,000 or more per millimeter of path length.

[0008] The prior art in the literature has failed to overcome these problems. For example, U.S. Patent 2,334,475 describes pressing a window against the wall of a well in accordance with the above-described Technique 1. Similarly, U.S. Patent 2,812,697 describes the use of local displacement of fluid according to Technique 2. British Patent 2,332,331 describes infrared radiation to enable imaging of the asphaltenes in crude oil, because the asphaltene absorbance decreases at longer wavelengths. However, such techniques are still subject to scattering by any suspended particles. U.S. Patent 2,334,475, filed in 1938, describes the use of a transparent mud eliminator and optical imaging of the wellbore using infrared to ultraviolet light. Formally, "the incident beam and the light emitted by the wall are arranged to pass through a window of a transparent material such as glass or quartz, which window is, for example, firmly pressed against the wall of the well by appropriate means in accordance with the present invention." U.S. Patent 5,517,024 states that drilling "fluids are relatively opaque even over short distances of about a few millimeters. Even when water or brine is used as the drilling fluid, the presence of drill cuttings and suspended solids and formation fluids makes the fluid effectively opaque." The only mitigation provided by U.S. Patent 5,517,024 is at a separation distance "less than one millimeter" or "nonexistent" or the use of a "light-transmissive fluid such as water or brine" that contains no suspended particles. U.S. Patent 7,646,480 for optical imaging of a borehole states that "video techniques for inspecting the interior of a borehole are known," but "this method requires the presence of a transparent fluid in the well and thus cannot be used during the drilling or production phases of a well in which an opaque fluid is present." The only mitigation provided by U.S. Patent 7,646,480 is the use of a "sensor head that includes a window for applying against the wall of the borehole" such that "the sensor head is applied to the borehole wall." U.S. Patent Publication No. 2011 / 0096622 proposed acoustic imaging for optically opaque fluids and stated that using a "conventional optical camera... requires days to replace the existing drilling fluid with clear water." U.S. Patent 9,765,609 states that "in cases where the borehole fluid is too opaque, a clear fluid can be used to flush the area in front of the sensor to enable imaging." It is not recommended to perform downhole wellbore imaging with the aid of algorithms for obtaining images through highly scattering media, and thus for 81 years, this has been a long-standing unmet need in borehole imaging. There are many other examples of these specific implementations in the literature. Summary of the Invention

[0009] The Applicant has recognized the problems mentioned above herein and has conceived and developed embodiments of a system and method for downhole optical imaging in accordance with the present disclosure.

[0010] In one embodiment, a system for downhole optical imaging includes a housing forming at least a portion of a tool string. The system also includes a source disposed within the housing, the source emitting light through a window formed in the housing. The system also includes an imager disposed within the housing, the imager receiving imaging data through the window. The system also includes a control system communicatively coupled to the imager, the control system using one or more algorithms to process the image data, the one or more algorithms modifying the imaging data at least in part based on a scattering material surrounding the housing.

[0011] In one embodiment, a method for downhole optical imaging includes positioning an imaging device and a source within a downhole tool. The method also includes disposing the downhole tool in a subterranean formation proximate a wellbore wall. The method also includes collecting image data, the image data being collected through a scattering material such as drilling fluid positioned between the downhole tool and the wellbore wall. The method also includes using one or more algorithms to process the image data, the one or more algorithms adjusting the image data at least in part due to the scattering material.

[0012] In one embodiment, a system for downhole optical imaging includes a housing forming at least a portion of a tool string, the housing being disposed within a wellbore that includes a fluid having suspended particles. The system also includes a source disposed within the housing, the source emitting light through a window formed in the housing. The system also includes an imager disposed within the housing, the imager receiving imaging data through the window, the imager being disposed proximate the source. The system also includes a control system adapted to process the image data through one or more algorithms for determining imaging information through the scattering material, the one or more algorithms being adapted to be used with a downhole environment in which the imaging information travels through the scattering material at least twice. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present technology will be better understood by reading the following detailed description of non-limiting embodiments of the technology and by viewing the drawings, in which:

[0014] Figure 1 is a schematic front view of an embodiment of a wellbore system in accordance with an embodiment of the present disclosure;

[0015] Figure 2 is a schematic cross-sectional view of an embodiment of a downhole tool disposed within a wellbore in accordance with an embodiment of the present disclosure;

[0016] Figures 3A - 3D is an example of image data for use with downhole optical imaging in accordance with an embodiment of the present disclosure;

[0017] Figures 4A - 4D is an example of image data for use with downhole optical imaging in accordance with an embodiment of the present disclosure;

[0018] Figure 5 is a schematic diagram of an environment for use with downhole optical imaging in accordance with an embodiment of the present disclosure; and

[0019] Figure 6 is a flowchart of an embodiment of a method for downhole optical imaging in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] The foregoing aspects, features, and advantages of the present technology will be further understood when considered in conjunction with the following description of the preferred embodiments and the accompanying drawings, in which like reference numerals represent like elements. Specific terminology will be used to describe the preferred embodiments of the technology shown in the drawings for clarity. However, the present technology is not intended to be limited to the specific terminology used, and it should be understood that each specific term includes equivalents that operate in a similar manner to achieve a similar purpose.

[0021] When introducing elements of the various embodiments of the present invention, the articles "a," "an," "the," and "said" are intended to mean that there is 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 in addition to the listed elements. Any examples of operating parameters and / or environmental conditions do not exclude other parameters / conditions of the disclosed embodiments. Additionally, it should be understood that references to "one embodiment," "an embodiment," "certain embodiments," or "other embodiments" of the present invention are not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, references to terms regarding orientation such as "above," "below," "upper," "lower," "side," "front," "rear," or other terms are made with reference to the embodiments shown and are not intended to limit or exclude other orientations.

[0022] Embodiments of the present disclosure relate to systems and methods for downhole optical imaging to determine one or more properties of a borehole wall or formation. In various embodiments, the optical imaging may be performed in a borehole filled with a scattering medium such as a substantially opaque fluid that may contain particulates. The scattering medium may negatively affect optical signals (e.g., light) through various interactions such as absorption, reflection, scattering, etc. Even in the presence of the scattering medium, embodiments of the present disclosure facilitate the collection of imaging information. The image information may then be analyzed, for example, using time gating or speckle correlation algorithms. By way of example only, time gating may be used to evaluate certain types of photons, such as ballistic photons, or to evaluate data collection over a period of time in order to determine image information based on the concept that less scattered photons will reach their destination earlier. Ballistic photons are photons that have not scattered but have taken a straight-line path, which is the shortest path, and thus they will arrive first. The photons that arrive next have undergone some scattering, and so on. Combining data from all time frames reconstructs the original object being imaged. In the time gating method, photons may be emitted by a laser in short bursts, where the time of the burst defines time zero. In another example, speckle correlation may evaluate a speckle pattern and reconstruct the original image through a correlation algorithm. For example, when a light beam (e.g., photons) is diffusely reflected by a scattering material, a seemingly random granular pattern may be observed. Speckle correlation utilizes autocorrelation and phase retrieval algorithms, which may include trained neural networks, etc., to correct the granular pattern and reconstruct the granular pattern into the original image.

[0023] In various embodiments of the present disclosure, the systems and methods may be deployed in a downhole environment, such as within a wellbore. Accordingly, the components of the system may be specifically selected for use in high temperature and / or high pressure environments. Additionally, in various embodiments, the systems and methods may be used to reduce the amount of scattering material or to reduce the distance between the source and / or imager and the borehole wall, such as an optical window extension, etc.

[0024] In various embodiments, the optical imaging data provides higher resolution images for later evaluation, enabling the detection of fine fractures in unconventional reservoirs. It also enables geologists to view and interpret fine geological features below the resolution of acoustic or electrical imaging tools. Additionally, the systems and methods applied in the present invention address two obstacles associated with imaging through a scattering fluid such as drilling mud: 1) optical scattering by suspended solid particles in the mud (either through bubbles or through a liquid-liquid emulsion), and 2) optical absorption by these mixtures that have been intentionally added or have accidentally accumulated during drilling through various rock layers containing asphaltenes and resins, especially in oil-based mud. To address these issues, embodiments of the present disclosure may include a pad device on the logging tool to reduce the mud thickness between the imager and the borehole wall (e.g., about 2 mm - 3 mm or less). Additionally, the source of embodiments of the present disclosure may be near-infrared light (e.g., integrating all light between 1300 nm and 2000 nm), which is much less absorbed by asphaltenes and resins, but visible light may be used when there are small amounts of visible light absorbers such as asphaltenes present in the wellbore fluid. Furthermore, algorithms developed for optical imaging may be deployed with embodiments of the present disclosure.

[0025] Figure 1 FIG. 4 is a schematic side view of an embodiment of a wellbore system 100 that includes a tool 102 (which may be part of a tool string) that descends from a surface location 108 into a wellbore 104 formed in a formation 106. The illustrated wellbore 104 may be referred to as an open hole because no casing is shown along the wellbore wall. However, it should be understood that other wellbores such as cased wellbores may also utilize embodiments of the present disclosure. In a cased wellbore, a casing may be installed along at least a portion of the wellbore wall and glued in place to form a barrier along the wellbore wall. In an embodiment, the casing may be penetrable to facilitate the recovery of fluids such as hydrocarbons from the wellbore. Additionally, in various embodiments, the wellbore 104 may be filled with a fluid such as drilling fluid, hydrocarbons, brine, combinations thereof, etc. Furthermore, it should be understood that other components may also be disposed within the wellbore 104, and Figure 1The embodiments are for illustrative purposes only. For example, wellbore 104 may also include plugs or remedial equipment. The illustrated wellbore system 100 may be referred to as a wireline system because tool 102 is conveyed on cable 110, such as an electrical cable, but the system may also be deployed on a drill string for measurements during drilling. In various embodiments, the electrical cable may transmit electrical signals and / or energy from surface location 108 into wellbore 104, for example to provide operating power for tool 102 and / or to transmit data, such as data obtained from sensors disposed on tool 102. In various embodiments, tool 102 may be used to perform downhole logging operations and may be an imaging tool, a resistivity tool, a nuclear tool, or any other logging tool that can be used in a downhole environment. Additionally, in various embodiments, tool 102 may include multiple logging or imaging tools therein. For simplicity, all logging or imaging tools described herein will be referred to with reference to tool 102. However, in various embodiments, different tools 102 may be used to obtain logs or images from various tools at different times.

[0026] As described above, in various embodiments, tool 102 may be part of tool string 112, which may include various components for wellbore operations. For example, tool string 112 may include various other tools 114A - 114C, which may include sensors, measurement devices, communication devices, etc., and not all of these will be described for clarity. In various embodiments, tool string 112 may include one or more tools to perform at least one of logging operations, penetration operations, or well interventions. For example, nuclear logging tools, acoustic imaging tools, optical imaging tools, fluid sampling tools, core sampling devices, etc. may be utilized in logging operations. The correlation between the high-resolution optical images obtained in one well in the disclosed embodiments and the corresponding lower-resolution acoustic or electrical images and other logging data obtained in the same well may be used to interpret historical acoustic or electrical images or other logging data obtained in adjacent wells across the same geological formation where optical images have not yet been obtained. Penetration operations may include lowering a ballistic device into the wellbore to penetrate a casing or formation. Additionally, well interventions may include operations related to analyzing one or more features of the wellbore and continuing to perform one or more tasks in response to those features, such as data acquisition processes, cutting processes, cleaning processes, plugging processes, and inspection processes, etc. Thus, in various embodiments, tool string 112 may refer to tools lowered into the wellbore. Additionally, passive devices such as centralizers or stabilizers, tractor devices for facilitating the movement of tool string 112, etc. may also be incorporated into tool string 112.

[0027] In various embodiments, different power and / or data conducting tools may be utilized through the embodiments of the present disclosure to transmit and receive signals and / or electrical power. As will be described below, in various embodiments, sensors may be incorporated into various components of the tool string 112 and may communicate with the surface or other tool string components, for example, via communication through the cable 110, mud pulse telemetry, wireless communication, wired drill pipe, etc. Additionally, it should be understood that although various embodiments include a cable system, in other embodiments, rigid drill pipe, coiled tubing, or any other downhole exploration and production method may be utilized with the embodiments of the present disclosure.

[0028] The wellbore system 100 includes a wellhead assembly 116 shown at the opening of the wellbore 104 to provide pressure control of the wellbore and to allow equipment such as the cable 110 and the tool string 112 to enter the wellbore 104. In various embodiments, the wellhead assembly 116 may include a blowout preventer (BOP). In this example, the cable 110 is a cable spooled from a service vehicle 118. The shown cable 110 extends downward to the end of the tool string 112. In operation, when the tool string 112 is lowered into the wellbore 104, for example, to a predetermined depth, slack may be provided to the cable 110. In various embodiments, for example, in cases where gravity may be insufficient, such as in a deviated wellbore, fluid may be delivered into the wellbore 104 to drive the movement of the tool string 112. For example, a fluid pumping system (not shown) at the surface may pump fluid from a source into the wellbore 104 through a supply line or conduit. To control the travel rate of the downhole assembly, the tension on the cable 110 is controlled at a winch on the surface, which may be part of the service vehicle 118. Thus, the combination of the fluid flow rate and the tension on the cable may contribute to the travel rate or penetration rate of the tool string 112 into the wellbore 104. The cable 110 may be an armored cable that includes conductors for supplying electrical power (power) to downhole devices and a communication link for providing two-way communication between downhole tools and surface devices. Additionally, in various embodiments, tools such as tractor units, etc., may be further disposed along the tool string 112 to facilitate the movement of the tool string 112 into the wellbore 104. Thereafter, in various embodiments, the tool string 112 may be retrieved from the wellbore 14 by winding the cable 110 upward through the service vehicle 118. In this manner, well logging operations may be performed when the tool string 112 is brought to the surface 108.

[0029] In operation, various logging techniques can be utilized to obtain one or more formation characteristics to provide information to an operator for hydrocarbon recovery. For example, the detection of fine fractures along the wellbore wall can indicate that hydraulic fracturing operations can be used to create flow paths along these fractures. However, many logging techniques provide low-resolution images that can be difficult to analyze and detect one or more formation features, such as fine fractures, whereas optical imaging is capable of detecting the one or more formation features. Accordingly, embodiments of the present disclosure can deploy optical imaging techniques that utilize one or more algorithms to facilitate optical imaging through scattering materials such as the fluid present within the wellbore. Optical imaging can also be used to view the fracturing and effectiveness of proppants in keeping fractures open after the formation has been fractured and after the use of proppants. The optical imaging techniques can include equipment specifically selected for use with high-temperature and high-pressure wellbore environments. Additionally, the optical imaging techniques can overcome the deficiencies of the prior art by imaging through scattering materials, using light sources that may have reduced absorbance in the presence of hydrocarbons, and integrating machine learning techniques for evaluation and analysis.

[0030] Figure 2 FIG. 4 is a schematic cross-sectional view of an embodiment of a downhole environment 200 that includes an imaging tool 202 that interrogates the wellbore wall 204 of a wellbore 206. In various embodiments, the imaging tool 202 can form at least a portion of a tool string 112 and is conveyed into the wellbore 206 in a wireline operation via a cable 110. It should be appreciated that the downhole environment 200 can be subject to high temperatures and pressures, and thus components of the imaging tool 202, such as the housing 208, window 210, etc., can be specifically selected to accommodate the environment. In various embodiments, the window 210 comprises a transparent or translucent material to facilitate interrogation of the wellbore wall 204 by the source 212 and also reception of imaging information by the imager 214. In various embodiments, the source 212 includes a light source that emits near-infrared light, such as light having wavelengths of approximately 1300 nm and 2000 nm. The source 212 can emit a beam 216 that travels through the window 210 and into a scattering material 218 positioned within the wellbore 206. In various embodiments, the scattering material 218 can be a fluid within the wellbore annulus and can include solids, liquids, gases, or combinations thereof. For example, in the illustrated embodiment, the scattering material 218 includes suspended particles 220. In various embodiments, the scattering material 218 can also include fluids having a variety of different compositions, such as hydrocarbons, water, brine, etc.

[0031] The beam 216 shown enters the scattering material 218 and may be deflected due to interaction with components of the scattering material 218. For example, due to the scattering material 218, the first deflected beam 222 and the second deflected beam 224 provide the potential interactions shown. Thus, the imaging information (e.g., data acquired due to interrogation of the wellbore wall 204) may be blurred or otherwise perturbed in response to the deflected beam. However, in some embodiments, the beam 216 may include a direct path beam 226, which may include photons within the beam 216 that reach the wellbore wall 204 without interaction (or with minimal interaction) within the scattering material 218. In various embodiments, these may be referred to as ballistic photons. As will be described below, in time-gated data collection, the ballistic photons may reach the wellbore wall 204 first, and thus the data collected within a certain time period may have a high correlation with the ballistic photons. The beam 216 may be reflected from the wellbore wall 204 and returned to the imager 214. In various embodiments, the imager 214 is an electrically coupled device image sensor, a complementary metal oxide semiconductor image sensor, etc. The imager 214 receives the reflected beam and may thus acquire image information with respect to the wellbore wall 204. As described above, different types of reactions within the scattering material 218 may affect the type of information received. For example, the reflected direct path beam 228 may not undergo interaction (or limited interaction) with the scattering material 218, while the third deflected light beam 230 may interact with the scattering material 218.

[0032] In the embodiment shown, the scattering distance 232 represents the radial distance from the window 210 to the wellbore wall 204. The scattering distance 232 may be considered the distance that the beam 216 or its components travel to interact with the wellbore wall 204. However, since the source 212 and the imager 214 are arranged close to each other in the embodiment shown, the total distance traversed by the beam 216 and its reflected information is equal to twice the scattering distance 232. Thus, it should be understood that due to the high number of potential scattering interactions, the number of photons in the direct path beam 226 and the reflected direct path beam 228 may be low. Thus, different time periods, source numbers, etc. may be utilized in order to provide sufficient information for capture and analysis.

[0033] In operation, signals can be transmitted, for example, from a local or remote controller to source 212 to interrogate wellbore wall 204 with beam 216. In various embodiments, source 212 can emit a timed beam that can correspond to the time-gating method described below. Additionally, as described above, there can be multiple sources 212 that can operate together or independently. Imager 214 can receive image information that can have an associated timestamp or other specified information. Thereafter, the image information can be processed to develop an image corresponding to wellbore wall 204. For example, as will be described below, ballistic photons can be evaluated to identify one or more features of the wellbore wall. Additionally, various algorithms can be used to reconstruct the image information of the wellbore wall from the speckle information. Thus, high-resolution information can be obtained using downhole optical imaging techniques where scattering material is present within the wellbore and along the path of the light source.

[0034] Figures 3A - 3D is an example borehole wall image that can be analyzed using the systems and methods of the present disclosure. As described above, in various embodiments, source 212 can direct beam 216 towards wellbore wall 204, and image information can be recorded by imager 214. In the illustrated embodiment, Figure 3A is an example 300 of wellbore wall 204. As shown, wall 204 includes a crack 302 that extends along a portion of wall 204. Identification of the crack can be useful for wellbore operations because the crack can indicate potential areas for well stimulation techniques such as hydraulic fracturing. Thus, image information related to the appearance of wellbore wall 204 can be advantageous to the producer. However, Figure 3A embodiments of are difficult to determine using optical imaging in a wellbore environment. For example, as described above, scattering material 218 can cause scattering of beam 216, which reduces the likelihood of obtaining imaging information. However, embodiments of the present disclosure can utilize a time-gating method to evaluate image information over a period of time to reconstruct a view of the wellbore wall.

[0035] Figure 3BAn example 304 of an implementation for utilizing a time gate to detect image data 306 related to a crack 302 for ballistic photons that may not experience scattering. Since ballistic photons arrive first due to no scattering, the imager can be time-gated to isolate and / or substantially evaluate the image data related to substantially all ballistic photons. In various implementations, systems and methods such as an ultrafast scanning camera or a Kerr cell gate can be utilized to time-gate the image data 306 to evaluate ballistic photons. As shown, the image data 306 includes a contour 308 that substantially conforms to the crack 302. However, it should be understood that in various implementations, a small amount of scattering may also be acquired during the time gating corresponding to the image data 306. Additionally, in various implementations, the number of photons that do not experience scattering may be low, and thus multiple different image data sets can be acquired. For example, the source 212 can emit multiple bursts with corresponding image data acquired within a certain time period after the burst. In a highly scattering medium, the amount of time to obtain the image data may be undesirable. Thus, the implementation can further utilize an algorithm to utilize the remaining image data to obtain the final image data corresponding to the crack 302.

[0036] Figure 3C An example 310 of image data 312 corresponding to a time-averaged image. For example, the time-averaged image includes all or substantially all the information acquired by the imager 214. For example, in various implementations, the source 212 can emit an energy burst (e.g., light), and the imager 214 can acquire the information. The previously described time-gated data can correspond to ballistic photons that have not experienced or have substantially not experienced scattering and thus arrive at the imager 214 first. However, subsequent time gating can be used to evaluate photons that have experienced slightly less scattering, and the information can be averaged over a period of time to further obtain a general contour of the crack 302. When compared with the Figure 3B image data 306 Figure 3C the image data 312 is less refined and / or has more interference, which is the result of photon scattering. In other words, if photons can be represented as circles interacting on a plane, each subsequent scattering event and time gating will have slightly larger overlapping circles. Thus, compiling the data can result in an image with a clarity or resolution below an acceptable predetermined threshold. However, the information can be evaluated by, for example, utilizing and processing the information through an algorithm to obtain additional image information.

[0037] Figure 3DThis is an example 314 of image data 316 after processing using an algorithm that determines the origin of various photons within the pixels of the image data 316. In certain embodiments, the algorithm may utilize cascade probabilities, such as the algorithm described by Guy Satat et al. in "All Photons Imaging Through Volumetric Scattering" on September 29, 2016, which is incorporated herein by reference. The algorithm may evaluate changes over time to estimate scattering. For example, a larger intensity decrease may indicate lower scattering, while a gradual intensity decrease may indicate higher scattering. Thereafter, consecutive frames that are each individually time-gated may be evaluated to determine the corresponding probabilities between the consecutive frames. The algorithm may also predict subsequent frames and later frames to adjust the predictions and the model. Thereafter, a final light pattern may be provided that may correspond to Figure 3D the image data 316. It should be understood that the algorithm may be part of a machine learning process such as a trained neural network.

[0038] As shown, there are differences when comparing Figure 3A and Figure 3D the image data. For example, some details may not be captured. However, the general arrangement of the crack 302 may be shown after processing by the algorithm. In certain embodiments, the image data 316 may be evaluated for a confidence threshold prior to output to determine the likelihood that the image data 316 corresponds to an accurate representation. Advantageously, an optical image may be obtained within a downhole environment without the challenges associated with attempting to isolate or otherwise separate an area for imaging.

[0039] The systems and methods of the present disclosure may also include or utilize speckle correlation in an alternative form to evaluate image data corresponding to downhole optical imaging through a scattering material. As described above, in various embodiments, speckle correlation utilizes the principle that light from nearby points on an object is scattered through a scattering material to produce highly correlated but shifted random speckle patterns. Accordingly, embodiments of the present disclosure relate to the autocorrelation and reconstruction of image data to account for the shifted random speckle patterns.

[0040] Figures 4A - 4D This is an example borehole wall image that may be analyzed using the systems and methods of the present disclosure. As described above, in various embodiments, the source 212 may emit a beam 216 towards the wellbore wall 204, and image information may be recorded by the imager 214. In the illustrated embodiment, Figure 4A example 400 of Figure 4BAn example 404 of image data 406 is shown, which example may also be referred to as the original camera image. As shown, the features of the crack 402 are not recognizable in the image data 406, and thus such an image is of no value for downhole wellbore operations because this information may not provide the producer with direction or guidance regarding wellbore operations. Accordingly, the systems and methods of the present disclosure can be used to extract information indicative of the crack 402 from the image data 406.

[0041] Figure 4C An example 408 of image data 410 from an autocorrelation process is shown, where the processed Figure 4B image data 406 is processed to extract one or more features to determine an energy source (e.g., photons). In various embodiments, test data (e.g., ground truth data) can be evaluated to determine autocorrelation information, which can then be used with the autocorrelation data for an image associated with a wellbore. As described by Katz et al. in “Non-invasive real-time imaging through scattering layers and around corners via speckle correlations,” which is incorporated herein by reference, the autocorrelation for imaging through a scattering material is substantially the same as the autocorrelation of an object. Accordingly, various algorithms such as iterative Fienup-type algorithms can be used to generate image data 310 related to the autocorrelation.

[0042] Figure 4D An example 412 of image data 414 after being processed by one or more phrase retrieval algorithms is shown. Phrase retrieval refers to an algorithmic process of identifying phases that satisfy a set of constraints on the measured amplitude. In various embodiments, a hybrid input-output algorithm can be utilized. After processing, the image data 414 has a correlation with the crack 402. Accordingly, even in the presence of a scattering material, various processing algorithms can be used to extract image information to generate image data.

[0043] Figure 5FIG. 500 is a block diagram of an implementation environment 500 that can be used with embodiments of the present disclosure. It should be understood that although various components may be implemented separately, in various embodiments, different components may be integrated into one component. For example, the downhole system 502 and the analysis system 504 are shown as separate components, but in an embodiment, the analysis system 504 may be integrated into the downhole system 502 such that the analysis of image data can be performed in real time or near real time. The illustrated downhole system includes a source 212 and an imager 214. As described above, the source 212 can emit near-infrared light at various times and for different durations to provide illumination for interrogating the wellbore wall. The imager 214 can include a camera, which can be a high-speed camera or the like, and the camera can receive and process image data. A communication system 506 is further shown, which can provide communication between the downhole system 502 and the analysis system 504, for example, through a second communication system 508 of the analysis system 504. In certain embodiments, the respective communication systems 506, 508 can include wired or wireless communication protocols such as Wi-Fi, Ethernet, serial connections, etc. For example, the communication can include removing the stored memory of the imager 214 and connecting the stored memory to the analysis system 504. Thus, the communication systems 506, 508 facilitate the communication of data and instructions between the downhole system 502 and the analysis system 504.

[0044] In the illustrated embodiment, the analysis system 504 includes a controller 510, which includes a memory 512 and a processor 514. The process 514 can execute instructions stored on the memory 512 to facilitate the operation of the downhole system 502 and / or the analysis system 504. In addition, a timer 516 can be used for the time-gated analysis described above. The timer 516 can be used, for example, to send a signal to the source 212 to interrogate the wellbore wall for a predetermined period of time. Additionally, the timer 516 can determine the period of time during which the imager 214 receives image data, and the image data can be used, for example, in time-gated analysis to determine ballistic photons. Thus, in various embodiments, the analysis system 504 can be used to transmit instructions to the downhole system 502 to obtain image data.

[0045] Figure 5Further shown in [the figure] is a machine learning system 518, which incorporates an image generator 520 that can be used to generate images for evaluation after processing. For example, in various embodiments, the machine learning system 518 can incorporate a neural network, such as a convolutional neural network, which can be trained using ground truth data from a training database 522. For example, the training database can include speckle correlation images that can be used with the above-mentioned autocorrelation or phase retrieval steps. The shown machine learning system 518 also includes an autocorrelation module 524, a phase retrieval module 526, a time averaging module 528, and an origin module 530. In an embodiment, one or more of the modules can be used to process information. For example, with regard to time-gated analysis, ballistic photons can be evaluated together with time-averaged photons in order to generate an image by determining the origin of the photons, as described above. Additionally, with regard to the above-mentioned speckle correlation, an autocorrelation process can be utilized in combination with a phase retrieval algorithm in order to generate image data. In this way, the machine learning system can be incorporated into downhole imaging analysis to enable the identification and imaging of various features of the wellbore wall.

[0046] Figure 6 It is a flowchart of an embodiment of a method 600 for performing downhole imaging operations. It should be understood that, unless otherwise specifically stated, the steps of the method can be performed in any order or in parallel. Additionally, in an embodiment, there can be more or fewer steps. Figure 6 The method 600 begins with positioning an imaging device and a source in a downhole tool 802. For example, as described above, the source can include a light source, and the imaging device can include a camera. The downhole tool is lowered into the wellbore and positioned near the wellbore wall 804. In various embodiments, the downhole tool can be part of a wireline tool string or a drill string that positions different components at various locations along the wellbore. Image data can be collected 806. For example, the source can illuminate a portion of the wellbore wall, and the illumination can be through a scattering material, and the imaging data can be collected by the imaging device. In various embodiments, the imaging data can be processed 808. The data can be processed in real time or near real time or later. The processing can include using one or more of the above algorithms to evaluate the scattering of photons due to the scattering material. The processing step can generate image data indicative of the wellbore wall, which can be used to identify one or more features of the wellbore wall 810.

[0047] It should be understood that the embodiments require the use of a physical operating device to perform one or more physical operations on a geological formation, and the physical operating device can collect image data. To support the teachings herein, various analysis components can be used, including digital systems and / or analog systems. For example, downhole sensors, downhole electronics, downhole tools, and / or surface computer processing systems can include digital and / or analog systems. These systems can have components such as processors, storage media, memories, inputs, outputs, communication links (wired, wireless, optical, or other), user interfaces (e.g., displays or printers), software programs, signal processors (digital or analog), and other such components (such as resistors, capacitors, inductors, etc.) to provide operation and analysis of the devices and methods disclosed herein in any of several well-known ways. It is contemplated that these teachings can, but need not, be implemented in conjunction with a set of computer-executable instructions stored on a non-transitory computer-readable medium, which includes memories (ROM, RAM), optical media (CD-ROM), or magnetic media (e.g., disks, hard disk drives), or any other type of medium, and these computer-executable instructions, when executed, cause a computer to implement the method of the present invention. In addition to the functions described in this disclosure, these instructions can also provide equipment operation, control, data collection, analysis, and other functions that system designers, owners, users, or other such persons consider relevant. In addition, various other components can be included and are required to provide aspects of the teachings herein. For example, a power source (at least one of a generator, a remote power supply device, and a battery), a magnet, an electromagnet, a sensor, an electrode, a transmitter, a receiver, a transceiver, an antenna, a controller, an optical unit, an electrical unit, or an electromechanical unit can be included to support the various aspects discussed herein or to support other functions outside of this disclosure.

[0048] The embodiments can also be described in accordance with the following clauses:

[0049] 1. A system for downhole optical imaging, the system comprising:

[0050] A housing that forms at least a part of a tool string;

[0051] A source disposed within the housing, the source emitting light through a window formed in the housing;

[0052] An imager disposed within the housing, the imager receiving imaging data through the window; and

[0053] A control system communicatively coupled to the imager, the control system using one or more algorithms to process the image data, the one or more algorithms modifying the imaging data at least in part based on scattering material surrounding the housing.

[0054] 2. The system according to Clause 1, wherein the housing is deployed on a cable.

[0055] 3. The system according to Clause 1, wherein one or more algorithms include at least one of time gating operation and speckle correlation.

[0056] 4. The system according to Clause 1, the system further comprising:

[0057] A machine learning system trained to identify one or more autocorrelations between first speckle image data corresponding to image data in the absence of a scattering medium and second speckle image data corresponding to image data in the presence of the scattering medium.

[0058] 5. The system according to Clause 1, the system further comprising:

[0059] A timer that restricts image data capture to a predetermined time period corresponding to ballistic photons.

[0060] 6. The system according to Clause 1, wherein the housing is positioned within a wellbore and the scattering material is drilling fluid, particulate matter, or a combination thereof.

[0061] 7. The system according to Clause 1, wherein the light emitted by the source is near-infrared light.

[0062] 8. A method for downhole optical imaging, the method comprising:

[0063] Positioning an imaging device and a source within a downhole tool;

[0064] Positioning the downhole tool adjacent to a wellbore wall in a subterranean formation;

[0065] Collecting image data collected through a scattering material positioned between the downhole tool and the wellbore wall; and

[0066] Processing the image data using one or more algorithms that at least partially adjust the image data based on the scattering material.

[0067] 9. The method according to Clause 8, wherein the image data at least partially includes speckle image data.

[0068] 10. The method according to Clause 9, wherein processing the image data further comprises:

[0069] Determining the autocorrelation between the image data and reference image data; and

[0070] Determining the phase of the image data at least partially based on a phase retrieval algorithm.

[0071] 11. The method according to clause 8, wherein collecting image data further comprises:

[0072] collecting first image data during a first time period, the first image data corresponding to ballistic photons; and

[0073] collecting second image data during a second time period, the second image data corresponding to scattered photons.

[0074] 12. The method according to clause 11, wherein processing the image data further comprises:

[0075] determining a first image based at least in part on the first image data;

[0076] determining a second image based at least in part on the second image data, the second image corresponding to a time-averaged composition; and

[0077] determining the origin of the first image data and the second image data.

[0078] 13. The method according to clause 8, wherein the source and the imager are arranged on the same side of the wellbore wall.

[0079] 14. The method according to clause 8, the method further comprising:

[0080] emitting near-infrared light from the source towards the wellbore wall.

[0081] 15. The method according to clause 8, the method further comprising:

[0082] determining one or more features of the wellbore wall based at least in part on the processed image data.

[0083] 16. A system for downhole optical imaging, the system comprising:

[0084] a housing that forms at least a part of a tool string, the housing being disposed within a wellbore that includes a fluid having suspended particles;

[0085] a source disposed within the housing, the source emitting light through a window formed in the housing;

[0086] an imager disposed within the housing, the imager receiving imaging data through the window, the imager being disposed near the source; and

[0087] a control system adapted to process image data through one or more algorithms for determining imaging information through a scattering material, the one or more algorithms being adapted for use in a downhole environment in which the imaging information travels through the scattering material at least twice.

[0088] 17. The system according to clause 16, wherein the housing is deployed on a cable.

[0089] 18. The system according to clause 16, wherein at least one of the source and the imager is capable of moving to a position closer to the wellbore wall than the housing.

[0090] 19. The system according to clause 16, wherein the light emitted by the source is near-infrared light.

[0091] 20. The system according to clause 1, wherein one or more algorithms include at least one of time-gating operation and speckle correlation.

[0092] Although the techniques herein have been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the techniques. Accordingly, it should be understood that various modifications may be made to the exemplary embodiments and other arrangements may be designed without departing from the spirit and scope of the techniques as defined by the appended claims.

Claims

1. A system for downhole optical imaging in a wellbore filled with a highly scattering material, the system comprises: a housing that forms at least a part of a tool string; a source disposed within the housing, the source emitting light through a window formed in the housing; an imager disposed within the housing, the imager receiving imaging data through the window; and a control system communicatively coupled to the imager, the control system using one or more algorithms to process the image data, the one or more algorithms modifying the imaging data at least in part based on the highly scattering material surrounding the housing, the highly scattering material including one of suspended solid particles, bubbles in a liquid, or a liquid-liquid emulsion and reducing the light intensity by at least 100,000 times per millimeter of path length, wherein the one or more algorithms include at least one of time gating operation and speckle correlation.

2. The system according to claim 1, wherein the housing is deployed on a cable.

3. The system according to claim 1, the system further comprises: a machine learning system trained to identify one or more autocorrelations between first speckle image data corresponding to image data in the absence of a scattering medium and second speckle image data corresponding to image data in the presence of the scattering medium.

4. The system according to claim 1, the system further comprises: a timer that limits image data capture to a predetermined time period corresponding to ballistic photons.

5. The system according to claim 1, wherein the housing is positioned within the wellbore and the highly scattering material is drilling fluid, particulate matter, or a combination thereof.

6. The system according to claim 1, wherein the light emitted by the source is near-infrared light.

7. A method for downhole optical imaging, the method comprises: positioning an imaging device and a source within a downhole tool; positioning the downhole tool near a wellbore wall in a subterranean formation, the wellbore wall and the downhole tool being covered with a highly scattering material including one of suspended solid particles, bubbles in a liquid, or a liquid-liquid emulsion and reducing the light intensity by at least 100,000 times per millimeter of path length; collecting image data, the image data being collected through the highly scattering material positioned between the downhole tool and the wellbore wall, the image data reflecting the wellbore wall; and using one or more algorithms to process the image data, the one or more algorithms adjusting the image data at least in part based on the highly scattering material, wherein the one or more algorithms include at least one of time gating operation and speckle correlation.

8. The method according to claim 7, wherein the image data at least in part includes speckle image data.

9. The method according to claim 8, wherein processing the image data further comprises: determining an autocorrelation between the image data and reference image data; and determining a phase of the image data at least in part based on a phase retrieval algorithm.

10. The method according to claim 7, wherein collecting the image data further comprises: collecting first image data during a first time period, the first image data corresponding to ballistic photons; and collecting second image data during a second time period, the second image data corresponding to scattered photons.

11. The method according to claim 10, wherein processing the image data further comprises: determining a first image based at least in part on the first image data; determining a second image based at least in part on the second image data, the second image corresponding to a time-averaged composition; and determining an origin of the first image data and the second image data.

12. The method according to claim 7, wherein the source and the imager are arranged on the same side of the wellbore wall.

13. The method according to claim 7, the method further comprises: emitting near-infrared light from the source towards the wellbore wall.

14. The method according to claim 7, the method further comprises: determining one or more features of the wellbore wall based at least in part on the processed image data.

Images