CLIAMS:1. A system for detection and characterization of at least one fracture in a bore-well, said system comprising:
a single Fiber Bragg Grating (FBG) sensor configured to generate temperature profile of
said bore-well by passing of said FBG sensor through water column of said bore-well; and
a means for comparing said generated temperature profile with theoretically simulated
temperature profile to detect and characterize said fracture.

2. The system of claim 1, wherein said FBG sensor measures generates said temperature profile by measuring temperature along depth of said bore-well.

3. The system of claim 1, wherein said theoretically simulated temperature profile is generated based on conduction-convection equation.

4. The system of claim 1, wherein said FBG sensor is configured within a rigid casing so as to form a FBG probe having good thermal conductivity.

5. The system of claim 4, wherein said FBG probe is operatively coupled with a fiber by means of a splice joint.

6. The system of claim 4, wherein said casing is made of stainless steel.

7. The system of claim 4, wherein said FBG probe is pressure insensitive.

8. The system of claim 1, wherein said means comprises a display unit configured to enable view and comparison of said generated temperature profile with theoretically simulated temperature profile to detect and characterize said fracture.

9. A method for detecting and characterizing at least one fracture in a bore-well, said method comprising:
incorporating a single Fiber Bragg Grating (FBG) sensor for generating temperature
profile of said bore-well by passing of said FBG sensor probe through water column
of said bore-well;
generating a theoretically simulated temperature profile based on conduction-
Convection equation; and
enabling comparison of said generated temperature profile with said theoretically
simulated temperature profile to detect and characterize said fracture.

10. The method of claim 9, wherein said FBG sensor is configured within a rigid casing so as to form a FBG probe having good thermal conductivity such that said FBG sensor is pressure insensitive, and wherein said FBG probe is operatively coupled with a fiber by means of a splice joint.
,TagSPECI:FIELD OF THE INVENTION
[0001] The present disclosure in general pertains to the fields of geo-engineering, hydrogeology and ground water hydrology. In particular, the present disclosure pertains to detection and characterization of fracture(s) in bore-well(s) by temperature profiling using pressure insensitive FBG temperature probe.

BACKGROUND OF THE INVENTION
[0002] The background description includes information that may be useful in understanding the present disclosure. It is not an admission that any of the information provided here in is prior art or relevant to the presently claimed disclosure, or that any publication specifically or implicitly referenced is prior art.
[0003] Good fractures in a bore-well can be a good source of ground water or other minerals in the subsurface region. There are several techniques for detection and characterization of fractures in subsurface region such as various forms of galvanic resistivity, electromagnetic conductivity, ground penetrating radar, etc. For detection of dominant fracture and characterization of a bore well, several methods and systems have been developed that use seismic and electromagnetic sounds. Fractures are mechanical breaks in rocks and may originate from strains arising from stress concentrations around gas or liquid flaws, heterogeneities, and physical discontinuities. Detection and characterization of fractures during different seasons can help, for example, the groundwater supply system to analyze recharge and discharge of water through such fractures.
[0004] Methods used in past capture temperature data measured as a function of depth, and look for sharp changes to detect/identify fractured bore-well portion/site/zone. A portion of bore-well where a sharp change in temperature profile is measured could be a potential fracture portion. Temperature log of the bore-well as a function of bore-well depth is recorded and any sharp departure in the temperature from the local geothermal gradient is monitored to identify fracture or fracture zones. Conventional sensors, such as thermistors, are often used to measure temperature of bore-well at different depths. However, these sensors are not designed for high temperature applications and may not work well in the geothermal settings having high temperature zones where temperature may exceed 200oC. Further, as the spatial resolution of these conventional thermistors is not very high, they may not be suitable in shallow subsurface groundwater systems where the temperature gradient is usually small and hence detecting fractures is difficult due to insignificant flow in the fractures resulting in substantial anomalies in temperature at fracture intersections.
[0005] In known implementations, in order to obtain higher resolution of temperature along the depth of the bore-well, one may either install a large number of individual sensors, or move a single sensor along the depth of the bore-well to capture bore-well temperature at different depths. The former approach requires a large number of sensors along with installation of complex instrumentation at different depths of bore-well. However, the small diameter of bore-wells poses constraints on this approach and therefore it may not be possible to place multiple sensors to detect temperature at different depths. Cost for sure is another consideration for not selecting this approach requiring multiple sensors at different depths of bore-well. The latter approach that uses a single sensor to record the temperature of bore-well at different depths by lowering or profiling the entire depth of the bore well by means of a rope or a measurement tape, though free from the above mentioned limitations, suffers from the drawback that the temperature cannot be logged synchronously at all depths.
[0006] Off late fiber-optic sensors have found application replacing conventional sensors in field of hydrology for applications such as monitoring stream temperature dynamics, submarine ground-water discharge, stream/groundwater interaction and temperature profiling along depth of lakes. One of the important techniques used is Fiber Optic Distributed Temperature Sensing (FO-DTS) that uses Raman scattering in a fiber optic cable to measure temperatures along the length of the fiber. A fiber cable is passed through the bore-well and temperature along depth measured and monitored to detect any sharp change in temperature. FO-DTS approach is also used for logging temperature profiles in bore-wells by either lowering fiber optic cable into the bore-well directly or by wrapping the fiber around a tube. The latter results in a higher spatial resolution of temperature. Using FO-DTS technique temperature resolution as fine as 0.010C with spatial and temporal resolutions of 1–2 m and10–60 sec respectively can be achieved for cables of length up to 10 km.
[0007] Though this approach has shown great promise, alternate approaches that are free from calibration, having high signal to noise ratio and improved accuracy are being explored in field of disclosure. There is therefore a need in the art to provide alternate systems and methods for quick and accurate detection of fracture using high resolution temperature data in bore-well that can be used for temperature profiling along the depth of shallow groundwater in an un-pumped bore-well.

OBJECTS OF THE INVENTION
[0008] An object of the present disclosure is to resolve problems and disadvantages of conventional technologies as described above.
[0009] Another object of the present disclosure is to provide a method and system for capturing temperature data using a sensor to create temperate profile of bore-well that can be used to detect fractured portion of bore-well.
[00010] It is an object of the present disclosure to obtain temperature profile along the depth of shallow groundwater in an un-pumped bore-well in a crystalline fracture granitic rock system.
[00011] It is another object of the present disclosure to provide a system and method for high resolution temperature profiling for narrow bore-wells.
[00012] It is an object of the present disclosure to provide a method and system for capturing high resolution temperature data using a fiber brag grating (FBG) sensor to create temperate profile of bore-well that can be used to detect fractured portion of bore-well.
[00013] It is an object of the present disclosure to provide a method and system for detecting fractured portion of bore-well by comparing the FBG temperature profile with theoretical model based on conduction-convection equation.
[00014] It is another object of the present disclosure to provide a pressure insensitive FBG temperature sensing probe for detecting temperature of the bore-well.
[00015] It is an object of the present disclosure to provide method and system for detecting amount of water/liquid entering un-pumped bore-well through detected fracture.
[00016] It is another object of the present disclosure to provide system and method for fracture detection of bore-wells independent of magnitude of water pressure.
[00017] It is another object of the present disclosure to provide system and method for characterization of flow behavior in fractures during different seasons of the year.

SUMMARY
[00018] Aspects of present disclosure generally pertain to detection and characterization of fracture in bore-wells, and further relate to analyzing recharge and discharge of water through such fractures for the purpose of studying groundwater supply system.
[00019] In an aspect, system and method of present disclosure provide for use of Fiber Bragg Grating (FBG) sensors for measuring temperature along the depth of bore-well for creating temperature profile along the depth of the shallow groundwater in an un-pumped bore-well in a crystalline fracture granitic rock system.
[00020] In another aspect, present disclosure discloses a system and method for detecting fracture in bore-well by comparing temperature profile with theoretical model based on conduction-convection equation. Systems and methods of the present disclosure can be used for detecting water/liquid entering the un-pumped bore-well through detected fracture.
[00021] Another aspect of the present disclosure provides a customized and calibrated pressure insensitive FBG temperature sensing probe for temperature measurement of a bore-well along its depth.
[00022] In another aspect, the present disclosure provides technique(s) that uses a single sensing element for temperature measurement along the length/depth of the bore-well that is independent of the magnitude of water pressure inside the bore-well.
[00023] According to one aspect of the present disclosure, temperature profile obtained from FBG sensor during different seasons of the year can be used to analyze the behavior of groundwater flow patterns in the detected fractures during different seasons.
[00024] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[00025] FIG. 1 illustrates an exemplary schematic view of pressure insensitive FBG temperature probe for temperature sensing in accordance with embodiments of the present disclosure.
[00026] FIG.2 illustrates an exemplary calibration curve of pressure insensitive FBG temperature probe in accordance with embodiments of the present disclosure.
[00027] FIG. 3 illustrates an exemplary graph of wavelength shift in respect of bare fiber FBG sensor and FBG temperature probe during a test set up, illustrating pressure insensitivity of FBG temperature probe in accordance with embodiments of the present disclosure.
[00028] FIG. 4 illustrates geographical map of experimental sites for bore-well experimentations in accordance with embodiments of the present disclosure.
[00029] FIG. 5 illustrates exemplary temperatures profiles along bore well depth during various experiments conducted in accordance with embodiments of the present disclosure.
[00030] FIG. 6(a) illustrates an exemplary bore-well camera image indicating a non-fracture bore surface recorded during experimentation in accordance with embodiments of the present disclosure.
[00031] FIG. 6(b) illustrates an exemplary bore well camera image indicating a fracturedbore surface recorded during experimentation in accordance with embodiments of the present disclosure.
[00032] FIG. 7(a) illustrates an exemplary temperature profile of a bore-well recorded during experimentation spread over two different seasons in accordance with embodiments of the present disclosure.
[00033] FIG. 7(b) illustrates another exemplary temperature profile of another bore-well recorded during experimentation spread over two different seasons in accordance with embodiments of the present disclosure.
[00034] FIG. 8 illustrates exemplary modules of fracture detection and characterization system in accordance with embodiments of the present disclosure.
[00035] FIG. 9 illustrates an exemplary flow chart of method used for detection and characterization of fracture in bore-well in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION
[00036] Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[00037] Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[00038] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[00039] The headings and abstract of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[00040] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
[00041] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[00042] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[00043] The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed.
[00044] Embodiments of present disclosure described herein relate to system and method of temperature profiling of bore-well for detection and characterization of fractures in bore-well. One or more embodiments of present disclosure describe systems and methods that use Fiber Bragg Grating sensors (FBG sensor(s)) for temperature measurement along the depth of bore-well and create temperature profile of the bore-well. Further, the temperature profile can be used for detection and characterization of one or more fractures in the bore-well.
[00045] According to an embodiment of present disclosure, system and method for creating temperature profile along the depth of the shallow groundwater in an un-pumped bore-well in a crystalline fracture granitic rock system is described.
[00046] Use of Fiber Bragg Grating (FBG) sensors, which have advantages such as low fatigue, high sensitivity, and ultra-fast response, have a strong industrial application in capturing and recording temperature of a bore-well. FBG is a periodic modulation of refractive index of a core of a single-mode photosensitive optical fiber along its axis. In implementation, when a broadband light is launched into an FBG, a single wavelength that satisfies the Bragg condition can be reflected back while the rest of the spectrum is transmitted. This reflected Bragg wavelength (?B) of the FBG can be given by
?B=2neff ?
where, ? is periodicity of grating, and neff is effective refractive index of fiber core.
[00047] In the present disclosure, any external perturbation such as strain, temperature, etc. at the grating site of the FBG sensor, can alter periodicity of grating, and in turn change the reflected Bragg wavelength. By interrogating shift in Bragg wavelength, parametric external perturbation can be quantified. Shift in the Bragg wavelength is sensitive to both strain and temperature and is given by,

where is change in Bragg wavelength, is the strain effect term, and is the temperature effect term.
[00048] Temperature affects Bragg wavelength due to the thermal expansion or contraction through thermo-optic and thermal expansion coefficients. Using this property of FBG, it can be effectively and gainfully used for preparing temperature profile of a bore-well and thereafter for detection and characterization of fracture in the bore-well.
[00049] Studies have been performed in the past by comparing observed and simulated temperature profiles in a water column of a bore well using conduction-convection heat transport equation. The model is used to estimate groundwater recharge rate with the help of temperature profile of the bore well. The hypothesis used is that the temperature profile of water column in subsurface is linked to the changes in the air temperature, which controls upper boundary condition and recharge rate, and which further controls shape of the temperature profile with depth in the water column. The theoretical equation for temperature profile with depth is based on the work of Taniguchi et al. (1993) and is given as follows,

[00050] The equation is based on the conduction-convection heat transport equation (also referred as conduction-convection equation and two terms used interchangeably hereinafter), where T is temperature in degree Celsius, t is time in seconds, z is depth of the bore well water column in meters, a is subsurface thermal diffusivity (m2/s), q* is a variable dependent on vertical groundwater flux and thermal properties of water and subsurface. The variable q* is given by,
q*= qc0 ?0/c?
where q is the vertical groundwater flux (m s-1), which may be the recharge from rainfall in the ideal conditions, c0 is the specific heat of water (J Kg-1°C-1), ?0 is the density of water (Kg m-3), c is the specific heat of the subsurface (J Kg-1°C-1), and ? is the density of the subsurface (Kg m-3). The variable q* is constant if the subsurface is assumed to be homogenous with a uniform vertical groundwater flux q. As this is a semi-infinite medium, there is only one boundary condition. The boundary condition at the upper end is atmosphere, which maintains water at cooler temperature than the core of the earth.
[00051] The above equation and its solution can be advantageously utilized for fracture detection and characterization in a bore well in combination with temperature profile of bore well obtained using FBG temperature probe.
[00052] According to an embodiment of the present disclosure, one or more fracture portions/zone/sites in the bore-well can be detected by comparing temperature profile created by the FBG sensor data with theoretically simulated model based on conduction-convection equation. Embodiments of the present disclosure can be used for detecting water/liquid entering the un-pumped bore-well through detected fracture sites/portions. Also, as FBG sensor element is di-electric in nature since it is made of silica material, it does not cause any short circuit in wet environment.
[00053] According to another embodiment of the present disclosure, the FBG sensors used for the purpose of present disclosure can be customized and calibrated for making it pressure insensitive, which is interchangeably referred to as FBG temperature probe hereinafter. The present disclosure also introduces a new sensing methodology for qualitative investigation of fractures in bore wells, particularly to assess flow behavior in the fractures different time periods/seasons.
[00054] According to an embodiment of the present disclosure, a single sensing element can be used for creating temperature profile along the entire length/depth of the bore-well, and the created temperature profile can be independent of the magnitude of water pressure inside the bore-well.
[00055] In another embodiment of the present disclosure, temperature profile obtained from FBG temperature probe during different seasons of the year can be used to analyze the pattern and behavior of groundwater flow through the delineated fractures.
[00056] In another embodiment, the present disclosure provides for use of a pressure insensitive FBG temperature sensing probe that can be packed and calibrated for temperature profiling of bore-well. As FBG sensors, in addition to temperature, are also sensitive to other external perturbations such as strain caused by mechanical pressure and other impacts, exemplary FBG temperature probe in accordance with present disclosure needs to be isolated from these for getting accurate temperature measurement free from pressure variations.
[00057] FIG. 1 illustrates an exemplary schematic view of a FBG temperature probe 100 configured to isolate FBG sensor from perturbation other than temperature, and for use as temperature probe in accordance with present disclosure. In an exemplary implementation, FBG sensor can be placed in a casing made of corrosion resistant, hard, and rigid material having good thermal conductivity such as, but not limited to, a tube made of stainless steel 102of suitable inner diameter such as 200 µm. The FBG sensor itself can be fabricated on a fiber of diameter 125 µm, whose one end is enclosed and the other end is pigtailed to the connecting fiber106 through a splice joint 104.
[00058] In an experimental embodiment, the fabricated FBG temperature probe 100 can be validated for correctness of temperature recording and for its insensitivity to external pressure and impact. Validation and calibration of FBG temperature probe100can be carried out using bare FBG sensors whose temperature response is known. At the start of validation, both bare FBG sensor and the fabricated FBG temperature probe 100 can be placed and bonded in close vicinity on a flat metal plate whose temperature can be raised from 20K to 120K. Wavelength shift in the FBG temperature probe 100 can be noted for every 50pm shift in wavelength of the bare FBG sensor (corresponding to a temperature change of 5K at 10pm/K).
[00059] FIG. 2 illustrates an exemplary calibration curve 200 of the FBG temperature probe in accordance with an embodiment of the present disclosure. The curve compares wavelength shift represented by curve 202 pertaining to FBG temperature probe 100with that of bare FBG sensor represented by curve 204. From the two curves, it can be concluded that response of both FBG temperature probe 100and bare FBG sensor matches well through the entire temperature range covered by heating during the calibration. Therefore, calibration factor 10 pm/K of the bare FBG sensor can been used as calibration factor for FBG temperatureprobe100 developed in accordance with embodiment of present disclosure.
[00060] In another experimental embodiment, FBG temperature probe 100 of the present disclosure can be validated for pressure insensitivity. Pressure insensitivity trials can be carried out by comparing its response to applied pressure and impacts in comparison to that of another sensor such as bare FBG sensor with known temperature and pressure response. In an embodiment, a flat stainless steel metal plate is used to bond the two sensors in close vicinity to each other using suitable adhesive such as but not limited to cyano-acrylate adhesive in such a manner that external pressure and impact perturbations applied on them are equally experienced by both. In order to simulate pressure and impact perturbations the sensor bonded area of the stainless steel metal plate can be exposed to random air pressure bursts using a commercial air blowing device. To assess and compare the effect of perturbations caused by air burst on the two sensors wavelength shift of both the sensors can be simultaneously recorded.
[00061] FIG. 3 illustrates exemplary graphs of wavelength shift over time for pressure insensitivity test of FBG temperature probe 100 in accordance with above embodiment of the present disclosure. Graphs plotted therein illustrate wavelength shift of the two sensors under the condition of external pressure and impact perturbations applied on them by means of three randomly increasing air pressure bursts. Bragg wavelength shift 302 in respect of bare FBG sensor illustrates that the bare FBG sensor is affected by external perturbations imparted by airbursts, whereas there is no wavelength shift in respect of FBG temperature probe 100, as depicted by wavelength shift curve 304 in respect of same establishing its pressure insensitivity, thus validating design requirement of FBG temperature probe 100 for its use in pressure/strain varying bore-well application for temperature measurements.
[00062] In an embodiment, a single FBG temperature probe 100can be advantageously used to measure temperature of a bore-well. In an exemplary implementation, a single FBG temperature probe 100scans entire depth of the water column in a bore-well by traversing through the bore-well. In an alternate methodology, multiple temperature probes can be used to get spatial temperature measurements along depth of bore-well by placing a number of FBG sensors at different depths. The methodology suffers from drawback of uncertainty of detecting the fractures in bore-wells of moderate depths (˜100 m). This is specially so in an un-pumped bore-well, which is free from strong circulation and mixing of water within the water column. In such circumstances, the embodiment of temperature measurement along depth of bore-well by lowering of a single probe is advantageous. In another embodiment of application. Vertical spatial resolution of the temperature depends on rate of lowering of probe and FBG temperature probe is advantageous in view of its quick response resulting in faster scanning of entire depth of bore-well. Therefore, in a preferred embodiment of the present disclosure, it is advisable to use a single FBG temperature probe 100 that can be lowered into the bore-well to record temperature data at different depths and creation of temperature profile of the bore-well for use to detect fractures or characterize inside the bore-well.
[00063] In an exemplary implementation, FBG temperature probe 100can be attached to a graduated measuring tape with suitable weight (500 gm) and can be lowered along the water column of the bore-well to get temperature data along the depth of the bore-well. To acquire the shift in wavelength of the FBG temperature probe 100 due to the variations in temperature along the column of water, a FBG interrogator such as one having sampling frequency of 1 kHz with a typical wavelength resolution of 1pm can be used. This interrogated wavelength can then be converted to corresponding temperature using calibration factor for example 10pm/°K as ascertained during calibration/validation. A temperature profile is created for bore-well using the data obtained from FBG temperature probe 100. Any sudden change in temperature along the depth can be an indication of a fracture and by identifying the depths at which the temperature anomaly exists, fracture depths can be assessed. Experiments to try out and validate above embodiments were conducted and there details are enumerated in successive paragraphs.
[00064] FIG. 4 illustrates geographical sketch 400 of the site used for validation of embodiments of present disclosure. The sketch 400 illustrates topographical details along with recharge and discharge zones of the site located in the semi-urban micro-catchment area. The sketch 400 also illustrates first and next order stream drainages. For validation trials, two bore-wellsWELL-1 402 and WELL-2 404 located in the small micro-catchment area with stream draining towards south-east direction and to a lake were selected. WELL-1 402was located away from the first-order stream and located at a higher elevation of 925 m amsl, whereas WELL-2 404was located in valley close to the first-order stream at 910 m amsl. Depth of both wells WELL-1 402 andWELL-2 from ground level was around 130 m, where the geology of the region is granitic and subsurface is characterized by a weathered zone of 15-20 m deep, followed by fractured rock. Using the FBG temperature probe, temperature profiles of the WELL-1 402 and WELL-2 404were created for the purpose of fracture detection and study of its seasonal behavior.
[00065] Figure 5illustrates exemplary temperature profiles of bore-wells along their depth recorded during various validation experiments in accordance with embodiments of the present disclosure. In implementation, temperature can be logged along the entire depth of bore-well using FBG temperature probe 100 and interrogator connected to the probe 100. The temperature recorded can then be normalized with respect to the temperature of the water surface in the well at the time of the measurement. Normalization can be done by correcting the profile temperature by subtracting the temperature of the water surface.
[00066] In an embodiment of the present disclosure, a uniform speed for lowering of the FBG probe can be maintained to get reliable temperature readings as the temperature readings could be sensitive to the variations in the transiting time of the probe along the depth of the bore-well. Those skilled in art can implement contraption to lower the temperature probe 100 in a bore well at a desirable uniform rate and such implementation is well within the scope of present disclosure. Alternately, it is possible to discount such errors by carrying out multiple measurements while lowering the probe manually. As shown in the FIG.5, these multiple-trials record a reliable temperature profile with the inflection point.
[00067] In the exemplary graph illustrated in FIG. 5 depicting temperature profile of WELL-1 302, data was collected three times during Trial 1, Trial 2, and Trial 3 and depicted therein as curve 504, curve 506, and curve 508. As is illustrated by the graphs in FIG. 5, the normalized temperature generally increases with depth of water column. However, this increase is not monotonic and a noticeable shift is observed at depth of 72 m from ground surface.
[00068] Usually abrupt temperature changes in water column of a bore-well occur in localized fracture zones or small faults due to which temperature profile often exhibits abrupt temperature changes over a small distance, typically surging or dropping several degrees over several tens of meters. In the present case, a similar behavior is observed with the temperature shifting at 72 m towards a lower value. The shift to the lower value could be due to water coming from a colder source into the well at this depth. Since the temperature of water in the upper layers is colder, the temperature profile showing an inflection at 72 m can be attributed to the flow of water from upper layers through the fracture intersecting the well at this depth. Therefore, the shift itself can be interpreted to indicate presence of a fracture but can be better appreciated when compared with theoretical simulated temperature profile 502 in accordance with an embodiment of present disclosure.
[00069] In an embodiment, temperature profile created from the BFG temperature sensing probe can be compared with theoretically simulated temperature profile of the water column, which can be obtained by any known method. In an embodiment of the present application, conduction-convection equations mentioned above can be used to simulate theoretical temperature profile of the water column for which required parameters (a and q*) can be optimized in MATLAB using GA tool box and the simulated temperature profile can be worked out.
[00070] Figure 5 incorporates an exemplary theoretically simulated temperature profile curve 502 for WELL-1 402. It can be seen that the measured temperature in the shallow depth matches well with theoretical value, and shows a deviation close to fracture at 72m as interpreted in paragraph above based on the inflection point in the measured profile. Beyond 72m, recorded temperature profile 504, 506 or 508 slowly regains temperature trend of theoretically simulated temperature profile 502. In absence of any other fracture, measured temperature profile follows the theoretical temperature profile for the remaining depth of bore-well. Though the exemplary curves represent a case where only a single fracture is detected, it is possible for the system of present disclosure to detect one or more fracture in a single measurement. In case there are more than one fracture in bore-well temperature profile may show deviation from the theoretical model at more than one site.
[00071] In order to further validate the experimental findings, detected fracture can be verified using a bore-well camera that can be slowly lowered through the depth of the well and images of bore wall displayed on the display screen. A commercial bore-well camera system, which is equipped with a light source at the camera tip, a graduated tape, a tele-viewer and a video logger, can be used for imaging the walls of well from the water surface to the bottom of the well. The presence of fractures and any anomalies on the wall of the bore-well can be visualized and captured by the proposed system. Visual identification of fracture detected by the FBG temperature profiling shall validate the disclosed process of detection and characterization of fractures in bore-well.
[00072] FIG. 6(a) illustrates an exemplary image 600 of a non-fracture surface recorded with bore-well camera system. The highlighted portion 602 of the image 600 depicts regular texture of the bore-well wall where there is no fracture. FIG. 6(b) illustrates an exemplary image 650 obtained from bore-well camera system recorded at depth of 72 m of experimental bore-well 402 showing the fractured surface in accordance with an embodiment of the present disclosure. The highlighted portion 652 of the image 650 depicts caved surface of the wall of bore-well. The difference in texture of highlighted portion 602 and 652 can be indicative of the fracture. Due to the presence of an active fracture, wall surface of the bore-well could have eroded, which resulted in patterns observed in highlighted portion 652. Depth of the fracture obtained from the bore-well camera system at 72m matches exactly with the interpreted depth of the fracture obtained from the FBG temperature sensing probe data. Thus bore-well investigation by camera has validated the disclosed process of detection and characterization of fractures in bore-well.
[00073] In an embodiment, behavior of the detected fractures in bore-well during different seasons can also be observed and analyzed by technique of temperature profiling by collecting temperature data using FBG temperature probe 100. The difference in temperature at the fractured site can be an indication of varying inflow of water/liquid during different seasons on the year. The present disclosure can be used for characterization of flows in known fractures during different seasons.
[00074] In an exemplary experiment, temperature profiles in two contrasting bore-wells, one located in recharge zone and other in discharge zone of a micro catchment area were chosen. To analyze the seasonal behavior of the detected fracture, temperature profile of the bore-well can be created using FBG temperature sensing probe in different months of the years such as one profile can be collected in end of summer and another in post monsoon season. Based on the change of temperature at particular fracture site during different months of the year, the seasonal behavior of fracture of bore-well can be determined.
[00075] In another exemplary experiment, for characterization of flow in known fractures during different seasons of a bore-well, temperature profile of bore well was recorded during different seasons such as during pre-monsoon season and post-monsoon season.
[00076] FIG. 7(a) illustrates an exemplary temperature profile 700 of a bore-well such as WELL-1 402recorded during two different seasons such as during pre-monsoon and post-monsoon seasons in accordance with an embodiment of the present disclosure. Depicted therein is theoretically simulated temperature profile 702, the pre-monsoon temperature profile 704, post monsoon temperature profile 706 and the detected fracture site 708. The temperature profile along the bore-well can be influenced by water surface temperature, which on the other hand, is affected by the air temperature. Therefore, temperature profiles 704 and 706 recorded during different seasons are shifted apart. It is observed from FIG. 7(a) that the simulated temperature profile 702 fits with pre-monsoon temperature profile 704. However, the post-monsoon temperature profile 706 deviates from the theoretical model profile 702. The good fit between the theoretical model temperature profile702 and measured pre-monsoon temperature profile 704 suggests that the there is relatively very little flow through the fracture during that season. This is feasible as the WELL-1 402 is located in the local ridge of the catchment and hence there would be no recharge from the upper layers after a prolonged dry season. On the contrary, the large deviation of the post monsoon temperature profile706 suggests that there exists a flow in the fracture, which is resulting from the vertical recharge occurring even at the local ridge portions of the catchment during rainy season.
[00077] FIG. 7(b) illustrates an exemplary temperature profile 750 of another bore-well WELL-2 404 recorded during two different seasons such as during pre-monsoon and post-monsoon seasons in accordance with an embodiment of the present disclosure. Depicted therein are theoretically simulated temperature profile 752, pre-monsoon temperature profile 754, post monsoon temperature profile 756, and the detected fracture site 758. It can be observed that at a depth of 72.6m, the measured profiles sharply deviate from the theoretical profiles indicating the presence of a fracture at this depth. Moreover, it is observed that the deviation in summer is smaller than that in the winter at this depth suggesting that the flow to the fracture is occurring from the upper layers in pre-monsoon season but at considerably reduced level. This is logical as WELL-2 is located closer to the valley of the first-order stream as shown in FIG. 4. A deviation from the theoretical profile is also observed at an approximate depth of 100 m but the deviation is not as sharp as it is at 72.6 m. This suggests that there could be small/minor multiple fractures at this depth. There is a distinct deviation between profiles in the April and November seasons at this depth suggesting change in quantum of flow from pre-monsoon to post-monsoon season.
[00078] Above validation has confirmed that it is possible to carry out detection and characterization of fractures in a bore well using FBF pressure insensitive temperature probe that can help water management system to plan the water supply during different seasons.
[00079] FIG. 8 illustrates different exemplary functional modules of fracture detection and characterization system 800 in accordance with embodiments of the present disclosure. In an aspect, the fracture detection and characterization system 800 can include a FBG temperature data collection module 802, a temperature profiling module804, a theoretical model generation module 806, a fracture detection module 808, and a fracture characterization module 810. One or more of these modules can be configured to work on single or different computing systems. The computing means for implementation of this fracture detection and characterization system 800 can be cloud based computing system, a standalone system, a general personal computer, or a laptop or a special purpose computer or a microcontroller. The said computing means/system can have an optional display device, input/output means and storage devices configured along with it or provided separately.
[00080] In an embodiment, the FBG temperature data collection module 802 can be configured to lower FBG temperature probe 100into bore-well at a predetermined rate in accordance with the requirement of transient response time of the FBG temperature probe 100. Such lowering can be performed manually or mechanically or by any other appropriate means.FBG temperature data collection module 802 can additionally be configured with an FBG interrogator that detects wavelength shift. Furthermore, the module 802 can be configured to use a calibration data computing means to arrive at temperature readings corresponding to different depths.
[00081] In another embodiment, temperature profiling module 804 can be configured to record corresponding depth so as to enable temperature profiling of the bore-well in context. In case the means to lower FBG temperature probe 100 are mechanical, corresponding depth data can be automatically logged with computing system so as to prepare temperature profile of bore-well.
[00082] In another embodiment, theoretical model generation module 806 can be configured to incorporate conduction-convection heat transfer equations and feed requisite constants to computing means, which can generate theoretically simulated temperature profile of the bore-well.
[00083] In another embodiment, fracture detection module 808 can include a display means on which recorded temperature profile and theoretically simulated temperature profile can be displayed for analysis and detection of fractures. Alternately, there can be means to highlight zones where recorded temperature profile deviates from theoretically simulated temperature profile beyond a predetermined amount.
[00084] In another embodiment, fracture characterization module 810 can include a means to store temperature profile of particular bore-well during different seasons and recall and compare them among themselves as also with theoretically simulated temperature profile to assess flow characteristics of the bore-well. There could also be empirical tables quantifying flow corresponding to various temperature differences.
[00085] FIG. 9 illustrates flow chart of an exemplary method 900 used for detection and characterization of fracture in bore-well in accordance with an embodiment of the present disclosure. At first step 902, a pressure insensitive FBG temperature probe can be configured and calibrated. In an embodiment, a bare FBG sensor can be configured in a casing and thereafter calibrated to make it a pressure insensitive FBG temperature probe. At step 904, theoretically simulated temperature profile of bore-well can be generated, wherein conduction-convection equations, as mentioned above, can be used to simulate theoretical temperature profile of the water column for which required parameters (a and q*) can be optimized in MATLAB using GA tool box and the simulated temperature profile can be worked out.
[00086] At step 906, temperature data of bore-well can be collected by lowering FBG temperature probe into bore-well. Lowering of FBG temperature probe can be manual or through mechanical means. In either case, corresponding depth data can be collected and temperature profile of bore-well can be prepared.
[00087] At steps 908, recorded temperature profile can be compared with theoretically simulated temperature profile of bore-well. The two profiles can be compared manually or through one or more computing means, wherein any difference between the two beyond certain predetermined values can be highlighted. At step 910, the identified departure in recorded temperature profile can be used to locate position of the fracture from depth data.
[00088] In an embodiment, one or more other sensors to detect different contaminants can be attached with the FBG temperature probe to detect presence of contaminants along the depth of the bore-well. The data collected from these sensors can be used to detect the contamination of the water/mineral within the bore-well or flow pattern of such contaminants. In an aspect, since the FBG sensor used is of 3 mm in length and about 300um in diameter, it can be deployed in inaccessible and narrow wells where submersible pumping system is previously installed. This developed instrumentation can also be used in un-pumped bore holes since the fracture evaluation method is independent of magnitude of water pressure. Furthermore, the effect of water pressure and sensor impacting to the bore well wall can be negated by the use of a specially developed explicit temperature sensing probe. At the same time, by using WDM (Wavelength Division Multiplexing) technique and multichannel FBG interrogator, large number of bore wells can be simultaneously and remotely monitored. The fracture delineation judgments can made in the present methodology, by comparing the deviation of experimental curve of the temperature and the simulated theoretical temperature curve; the obtained results are found be consistent. In another aspect, fracture delineation method in the present work is on the basis of experimental data obtained unlike bore hole imaging techniques which are prone to human interpretation errors.
[00089] In another aspect of the present disclosure, the present disclosure allows measurement of water temperature along the depth of bore well using FBG sensor system. The present disclosure further allows use of single FBG sensor methodology for detection of fracture in bore wells. The present disclosure, in an aspect, further provides a FBG sensor traversing method adopted for real-time temperature logging along the depth of the bore well along with enabling use of pressure insensitive FBG temperature sensor probe for bore well fracture detection and flow characterization. The present disclosure, in another aspect, allows characterization of flow behavior in fractures using temperature profile logged in the bore well using FBG sensor.
[00090] In another embodiment, one or more fractures detected in a one or more bore-well can be used to map the interconnected fractures or porous zone. For the purpose of mapping interconnected fractures, temperature of nearby bore-wells can be collected and simulated using the methods and systems of present disclosure.
[00091] Thus, the present disclosure provides systems and methods for detection and characterization of bore-well using pressure insensitive FBG temperature probe that are cost effective and save time.
[00092] The above description represents merely an exemplary embodiment of the present disclosure, without any intention to limit the scope of the present disclosure thereto. Various equivalent changes, alterations or modification based on the present disclosure are all consequently viewed as being embraced by the scope of the present disclosure.
[00093] As used herein, and unless the context dictates otherwise, the term "coupled to" is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms "coupled to" and "coupled with" are used synonymously. Within the context of this document terms "coupled to" and "coupled with" are also used euphemistically to mean “communicatively coupled with” over a network, where two or more devices are able to exchange data with each other over the network, possibly via one or more intermediary device.
[00094] It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C …. and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.

ADVANTAGES OF THE INVENTION
[00095] The present disclosure provides systems and methods for creating high resolution temperature profile of a bore-well that can be used for fracture detection.
[00096] The present disclosure provides system and method for use of FBG temperature probe to create temperature profile for fracture detection and characterization in a bore-well that is cost effective, quick, and accurate.
[00097] The present disclosure provides a pressure insensitive FBG temperature probe for temperature measurement along depth of bore-well irrespective of the inside pressure.
[00098] The present disclosure enables assessment of amount of water/liquid entering the un-pumped bore-well through detected fracture.
[00099] The present disclosure provides for use of single FBG temperature probe to create temperature profile of entire bore-well.
[000100] The present disclosure enables characterization of fractures in the entire length/depth of the bore-well in different seasons.
[000101] The present disclosure employs sensor element which is dielectric in nature (made by silica material), hence it does not cause any short circuit in wet environment.
[000102] The present disclosure employs sensor element which is of 3 mm in length and about 300 µm in diameter, it can be deployed in inaccessible and narrow wells where submersible pumping system is previously installed.
[000103] The present disclosure can also be used in un-pumped bore holes since the fracture evaluation method is independent of magnitude of water pressure.
[000104] The present disclosure also facilitates negation of possible errors in measurement from of the effect of water pressure and sensor impacting to the bore well by the use of a specially developed explicit temperature sensing probe.
[000105] The present disclosure also facilitates the use of WDM (Wavelength Division Multiplexing) technique and multichannel FBG interrogator, large number of bore wells can be simultaneously and remotely monitored.