Patent Description:
Existing coiled tubing, wireline, or slickline operations performed in an oil and gas well environment may offer fiber optic sensing technology for measuring wellbore parameters using Raman and Rayleigh backscattering processes. However, due to excess signal power loss and limited sensitivity to absolute strain in Raman and Rayleigh backscattered light return signals, the existing fiber optic sensing technology bypasses use of a fiber optic rotary joint within a reel assembly that stores the coiled tubing, wireline, or slickline. Because the fiber optic rotary joint is bypassed, the coiled tubing, wireline, or slickline-including the optical fiber-must be fully deployed and a lockout-tagout (LOTO) procedure must be completed prior to creating a physical connection between the optical fiber and an optical fiber interrogator capable of receiving the backscattered light signals. Further, the Raman and Rayleigh backscattering processes may be limited to performing accurate measurements for optical fibers extending up to a maximum of <NUM> in length.

Providing the physical connection between the optical fiber within the coiled tubing, wireline, or slickline and the interrogator may add excessive labor and time costs to a distributed temperature sensing process. Additionally, the physical connection limits acquisition of data to when the system is stationary (e.g., data cannot be collected while running into or out of a wellbore). Further, performing Raman or Rayleigh backscattering operations through the fiber optical rotary joint may introduce significant losses to the backscattered light signals. These significant losses may result in a reduction in temperature resolution and accuracy over a length of the optical fiber within a wellbore. <CIT> discloses systems and methods regarding a reel, downhole tool, control system and rotary joint. <CIT> discloses methods and apparatus for using an audible signal to monitor conditions at a downhole location in a well through use of a well cable containing a fiber optic, which may be either a slickline or a wireline fiber-optic cable, and providing an audible signal which varies in response to the monitored condition. <CIT> discloses a system for managing multiple transmissions over a single fiber optic thread at an oilfield. <CIT> discloses a system and method to log a wellbore, comprising a logging tool adapted to be deployed in a wellbore environment, the logging tool including at least one sensor for taking a measurement of the wellbore environment. <CIT> discloses a fiber optic modulation and demodulation system. <CIT> discloses a distributing strain sensing (DSS) system used to measure strain using optical fibers functioning as linear sensors. <CIT> discloses a method and system for monitoring a rapidly changing parameter in a well which includes detecting gain-based stimulated Brillouin backscattering due to light transmitted through at least one optical waveguide installed in a well, the Brillouin backscattering being dependent upon temperature and strain experienced by the waveguide in the well. <CIT> discloses an apparatus for estimating at least one parameter in a downhole environment which includes an optical fiber configured to be disposed in a borehole, the optical fiber having a property that causes intrinsic backscattering of signals transmitted therein.

Certain aspects and examples of the disclosure relate to monitoring wellbore temperature and optical fiber strain along an optical fiber installed within a wellbore. Light backscatters in the optical fiber due to a variety of effects, such as elastic scattering (e.g., Rayleigh scattering), inelastic photon scattering (e.g., Raman scattering), and interaction with a crystalline lattice wave (e.g., Brillouin scattering). Each of these backscattered light signals have distinctive spectral attributes (e.g., frequency shifts or peak amplitude shifts) related to the temperature and strain locally at the scattering event. These local variations in the optical fiber may be measured by transmitting light signals into the optical fiber and detecting backscattered light resulting from each location. In some examples, the backscattered light signals may return to an interrogator or other light signal measurement device through a fiber optic rotary joint. The fiber optic rotary joint may be attached to a reel storing the optical fiber or a coiled tubing, wireline, or slickline that contains the optical fiber. Further, the fiber optic rotary joint may maintain optical communication between the optical fiber and the interrogator or other light signal measurement device even while the optical fiber is deployed within the wellbore.

For example, the optical fiber described herein may be placed within a length of coiled tubing or within a length of wireline or slickline. The optical fiber may be used to monitor temperatures along a length of a wellbore in which the optical fiber is deployed. In using a Brillouin backscatter strain and temperature sensing technique, a backscattered light signal returned to a surface of the wellbore may be strong enough for a Brillouin optical time domain sensor (BOTDS) system, which may include a Brillouin optical time domain reflectometer (BOTDR) or analyzer (BOTDA), to measure the backscattered light signal through a fiber optic rotary joint (FORJ) coupled to a coiled tubing, wireline, or slickline reel. The reel, which stores excess coiled tubing, wireline, or slickline, rotates to run the coiled tubing, wireline, or slickline into or out of the wellbore. The FORJ may optically couple an uphole end of the optical fiber with the BOTDS system such that the BOTDS system is able to measure optical fiber strain and temperature along a length of the optical fiber within the wellbore even during rotation of the reel. For example, the FORJ may provide an optical path for backscattered light signals to reach the BOTDS system from the optical fiber.

These illustrative examples are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the drawings in which like numerals indicate like elements, and directional descriptions are used to describe the illustrative aspects but, like the illustrative aspects, should not be used to limit the present disclosure.

<FIG> is a cross-sectional schematic view of an example of a wellbore environment <NUM>. During a downhole operation within a well <NUM>, a conveyance subsystem <NUM>, which includes an optical fiber disposed within the conveyance subsystem <NUM>, may be deployed within a wellbore <NUM>. In an example, the conveyance subsystem <NUM> may include coiled tubing, a wireline, or a slickline. In an example, the downhole operation may include a wellbore stimulation operation (e.g., hydraulic fracturing), and a downhole end of the conveyance subsystem <NUM> (e.g., coiled tubing) may include a wellbore stimulation tool <NUM>. During other operations within the well <NUM>, the conveyance subsystem <NUM> may be a wireline or a slickline. The wireline or slickline may also include an optical fiber disposed within the wireline or slickline. Further, the coiled tubing, wireline, or slickline may provide power, control, communication lines, or a combination thereof from a surface <NUM> of the wellbore environment <NUM> to a downhole tool located at a downhole end of the coiled tubing, wireline, or slickline (e.g., a wireline logging tool, a perforating tool, a wellbore completion tool, a telemetry tool, etc. in place of the illustrated wellbore stimulation tool <NUM>). In an example, the optical fiber may be a single mode optical fiber or a multimode optical fiber. In one or more examples, multiple optical fibers may be included in the conveyance subsystem <NUM>. Further, in an example, a single optical fiber can be used for communication and logging.

As illustrated, the wellbore stimulation tool <NUM>, or any other downhole tool, is coupled to the downhole end of the conveyance subsystem <NUM>. The conveyance subsystem <NUM> may be deployed with the wellbore stimulation tool <NUM> into the wellbore <NUM> using a deployment system <NUM>. In an example, the deployment system <NUM> may include a reel <NUM> that stores unused portions of the conveyance subsystem <NUM> and turns to inject or retract the conveyance subsystem <NUM> within the wellbore <NUM>. The deployment system <NUM> may also include a surface equipment cabin <NUM>. The surface equipment cabin <NUM> may include a controller <NUM> that controls operation of the deployment system <NUM> (e.g., raising and lowering the conveyance subsystem <NUM>, controlling downhole operations within the wellbore <NUM>, etc.). A Brillouin optical time domain sensor (BOTDS) system <NUM> may also be positioned within the surface equipment cabin <NUM> or elsewhere at the surface <NUM> of the wellbore environment <NUM>.

The BOTDS system <NUM> may be optically coupled to an optical fiber <NUM> disposed outside the conveyance subsystem <NUM>, and the optical fiber <NUM> may be optically coupled to a fiber optic rotary joint (FORJ) <NUM> at the reel <NUM>. The FORJ <NUM> may provide an optical coupling between the optical fiber <NUM> and the optical fiber disposed within the conveyance subsystem <NUM>. The FORJ <NUM> may maintain the optical coupling even during rotation of the reel <NUM> to inject or retract the conveyance subsystem <NUM> into or from the wellbore <NUM>. For example, the FORJ <NUM> may provide an optical path for backscattered light signals to reach the BOTDS system <NUM> from the optical fiber <NUM>. Accordingly, measurements can be made by the BOTDS system <NUM> without connecting and disconnecting the optical fiber <NUM> between rotational movement of the reel <NUM>. Further, the BOTDS system <NUM> may take measurements while the wellbore stimulation tool <NUM>, or any other downhole tool, performs downhole operations.

In operation, the BOTDS system <NUM> may transmit a series of short and powerful light bursts into the optical fiber <NUM>. The FORJ <NUM> provides an optical coupling between the optical fiber <NUM> and the optical fiber within the conveyance subsystem <NUM>. In this manner, the light bursts from the BOTDS system <NUM> are transmitted from the FORJ <NUM> downhole along the optical fiber within the wellbore <NUM>. The FORJ <NUM> may maintain the optical coupling between the optical fiber <NUM> and the optical fiber within the conveyance subsystem <NUM> during ingress and egress of the conveyance subsystem <NUM> into and out of the wellbore <NUM>.

When the light bursts travel along the optical fiber within the conveyance subsystem <NUM>, an intense electric field of the light beam induces acoustic vibrations due to electrostriction or radiation pressure. The induced acoustic vibrations interact with the incoming light and result in backscattering of the light bursts toward the surface <NUM>. These backscattered light signals may be received and measured by the BOTDS system <NUM>. Based on the magnitude, frequency, and timing of the backscattered light signals, the BOTDS system <NUM> is able to monitor temperature and optical fiber strain at precise locations along the optical fiber within the wellbore <NUM>. Further, Brillouin scattering events result in backscattered light bursts that are stronger than Raman scattering events (e.g., approximately <NUM> dB stronger). The Brillouin scattering events are also more sensitive to absolute strain and temperature than Rayleigh scattering events. For example, Rayleigh scattering events exhibit a small dependence on temperature. Thus, the backscattered light signals may be strong enough to traverse the FORJ <NUM> on a return path to the BOTDS system <NUM> and sensitive enough to obtain temperature and strain information.

The BOTDS system <NUM> may be a Brillouin optical time domain reflectometer (BOTDR), or the BOTDS system <NUM> may be a Brillouin optical time domain analyzer (BOTDA). The BOTDR may use a single optical fiber within the conveyance subsystem <NUM>. The BOTDA may use two optical fibers within the conveyance subsystem <NUM> to form an optical transmission loop from the surface <NUM> of the wellbore environment <NUM> to a total depth of the conveyance subsystem <NUM> and back to the surface <NUM>. Operation of the BOTDA may be similar to operation of the BOTDR with increased sensitivity. The increased sensitivity may enable the BOTDA to compensate for strain-induced measured temperature variations along the optical fiber within the wellbore <NUM> more easily than the BOTDR.

When deploying the conveyance subsystem <NUM> into the wellbore <NUM> using the deployment system <NUM>, the conveyance subsystem <NUM> may be run through a gooseneck <NUM>. The gooseneck <NUM> may guide the conveyance subsystem <NUM> as it passes from a reel orientation on the reel <NUM> to a vertical orientation within the wellbore <NUM>. In an example, the gooseneck <NUM> may be positioned over a wellhead <NUM> and a blowout preventer <NUM> using a crane (not shown).

The gooseneck <NUM> may be mechanically and fluidically attached to an injector <NUM>, and the injector <NUM> may be mechanically and fluidically attached to a lubricator <NUM>, which is positioned between the injector <NUM> and the blowout preventer <NUM>. In operation, the injector <NUM> grips the conveyance subsystem <NUM> and a hydraulic drive system of the injector <NUM> provides an injection force on the conveyance subsystem <NUM> to drive the conveyance subsystem <NUM> within the wellbore <NUM>. The lubricator <NUM> may provide an area for staging tools (e.g., the wellbore stimulation tool <NUM>) prior to running the tools downhole within the wellbore <NUM> when the wellbore <NUM> represents a high-pressure well. Further, the lubricator <NUM> provides an area to store the tools during removal of the tools from the high-pressure well. That is, the lubricator <NUM> provides a staging area for injection and removal of tools into and from a high-pressure well (e.g., a live well).

While the wellbore environment <NUM> is depicted as using the conveyance subsystem <NUM> to install the wellbore stimulation tool <NUM> within the wellbore <NUM>, other tool conveyance systems, as discussed above, may also be employed to deploy other tools within the wellbore <NUM>. For example, the wellbore environment <NUM> may include a wireline or slickline, which also include an integrated optical fiber, to install the other downhole tools within the wellbore <NUM>. Additionally, while the wellbore environment <NUM> is depicted as a land based environment, the wellbore environment <NUM> may also be similarly introduced and operated in a subsea based environment. In an example, the conveyance subsystem <NUM> may be between <NUM> and <NUM> (i.e., between approximately <NUM>,<NUM> and <NUM>,<NUM> feet) in length, and the BOTDS system <NUM> may be able to detect temperature and optical fiber strain along the entire length In other examples, the conveyance subsystem <NUM> may be up to <NUM> (i.e., approximately <NUM>,<NUM> feet) in length. Further, in an example, the conveyance subsystem <NUM> may be between <NUM> inch and <NUM> inches in diameter.

While the descriptions provided herein are generally directed to a Brillouin backscattering sensor system (e.g., with the BOTDS system <NUM>), other backscattering techniques may also be used through the FORJ <NUM> at the reel <NUM>. For example, other backscattering sensor systems, such as Coherent Rayleigh and Raman instruments with sufficient light signal strength, may also receive backscattered light through the FORJ <NUM> to generate temperature profiles from within the wellbore <NUM>. Additionally, strings or linear arrays of low reflectivity Fiber Bragg Gratings or in-situ reflective fiber features may be employed along the conveyance subsystem <NUM> for quasi-distributed temperature sensing operations, quasi-distributed acoustic sensing operations, and quasi-distributed strain sensing operations. Further, wavelength division multiplexing of various laser interrogation and communications instruments may be simultaneously employed within the optical fiber for multiple wellbore parameter measurements over the individual optical fiber using sufficient optical multiplexing methods.

<FIG> is a flowchart of a process <NUM> for monitoring temperature and optical fiber strain within the wellbore <NUM>. At block <NUM>, the process <NUM> involves deploying an optical fiber downhole within the wellbore <NUM>. As discussed above with respect to <FIG>, the optical fiber may be disposed within the conveyance subsystem <NUM>. The optical fiber may be deployed into or removed from the wellbore <NUM> by rotating the reel <NUM>. Further, the optical fiber may remain optically coupled to the BOTDS system <NUM> through the FORJ <NUM> even during rotation of the reel <NUM>.

At block <NUM>, the process <NUM> involves transmitting light signals through the FORJ <NUM> into the optical fiber. The light signals may be transmitted as short light bursts by the BOTDS system <NUM>. In another example, the light signals may be transmitted as continuous light signals or longer and relatively weaker light bursts across the FORJ <NUM>. Further, the light signals may be transmitted into the optical fiber while the optical fiber is run into the wellbore <NUM>, while the optical fiber is stationary within the wellbore <NUM>, while the optical fiber is being removed from the wellbore <NUM>, or any combination thereof.

At block <NUM>, the process <NUM> involves receiving backscattered light signals from the optical fiber at the BOTDS system <NUM> through the FORJ <NUM>. Interactions with stimulated phonons in the optical fiber due to temperature or optical fiber strain may result in the backscatter of the light bursts toward the surface <NUM> of the wellbore <NUM>. These backscattered light signals may be received and measured by the BOTDS system <NUM>. Because the BOTDS system <NUM> interrogates Brillouin backscattering events, the light received from the optical fiber may be stronger than those in Raman scattering operations and more sensitive to temperature and absolute strain than those in Rayleigh scattering. Accordingly, the backscattered light signals may also be strong enough to traverse the FORJ <NUM> on a return path to the BOTDS system <NUM> while being able to interrogate temperature and absolute strain more accurately.

At block <NUM>, the process <NUM> involves analyzing the backscattered light signal received at the BOTDS system <NUM> to monitor temperature and optical strain along the optical fiber. Based on the magnitude, frequency, and timing of the backscattered light signals, the BOTDS system <NUM> is able to monitor temperature and optical fiber strain at precise locations along the optical fiber within the wellbore <NUM>. Analysis of the backscattered light signal may occur during other downhole operations performed by any downhole tools within the wellbore <NUM> or during communication between the downhole tools and surface equipment using optical, electrical, acoustic, or pressure based communication techniques. For example, the BOTDS system <NUM> may receive and analyze the backscattered light signal while the wellbore stimulation tool <NUM> performs a stimulation operation within the wellbore <NUM>, such as a hydraulic fracturing operation.

Further, the BOTDS system <NUM> may include a temporal filtering system. The temporal filtering system may provide a mechanism that separates temperature measurements and strain measurements. For example, an optical fiber strain profile of the optical fiber may remain sufficiently uniform during a data acquisition scan making the temporal filtering system able to filter out the effects of optical strain on the backscattered light signals. Additionally, changes to the temperature within the wellbore <NUM> and detected by the optical fiber occur slowly enough in comparison to the optical fiber strain profile that the temporal filtering system is also able to isolate and extract a temperature profile from the optical strain profile.

<FIG> is a flowchart of a process <NUM> for correcting temperature or strain measurements based on backscattered light signals received from within the wellbore <NUM>. As discussed above, a temporal filtering system of the BOTDS system <NUM> may be able to distinguish between effects of optical fiber strain components and temperature components of the backscattered light signals based on the speed of change of the components. At block <NUM>, the process <NUM> involves receiving the backscattered light signals from the optical fiber at the BOTDS system <NUM> through the FORJ <NUM> and generating a temperature and optical fiber strain profile based on the backscattered light signals. As discussed above, the power of the light signals provided by the BOTDS system <NUM> using Brillouin scattering may be sufficient for the backscattered light signals to traverse the FORJ <NUM> with sufficient signal strength for the BOTDS system <NUM> to analyze the backscattered light signals.

At block <NUM>, the process <NUM> involves filtering, by the BOTDS system <NUM>, the temperature or optical fiber strain components from the temperature and optical fiber strain profile. The BOTDS system <NUM> may use a temporal filtering system to filter the components to isolate a temperature profile or an optical fiber strain profile. In an example, the temporal filtering system may filter the temperature components or the optical fiber strain components by analyzing the speed at which the temperature and optical fiber strain profile changes along a length of the optical fiber. For example, if the BOTDS system <NUM> is isolating the temperature along the length of the optical fiber, the temporal filtering system may filter out changes that occur quickly due to the slow changing nature of the temperature. Likewise, if the BOTDS system <NUM> is isolating the optical fiber strain along the length of the optical fiber, the temporal filtering system may filter out changes that occur slowly due to the relatively fast changes indicated in the temperature and optical fiber strain profile resulting from optical fiber strain.

At block <NUM>, the process <NUM> involves generating temperature or optical fiber strain profiles from the filtered temperature and optical fiber strain profile. By isolating the temperature along the optical fiber or the optical fiber strain along the optical fiber, the resulting profile may be of only the temperature or of only the optical fiber strain. In one or more examples, the BOTDS system <NUM> may generate both the temperature profile and the optical strain profile along the optical fiber.

<FIG> is a flowchart of a process <NUM> for correcting temperature measurements based on backscattered light signals received from within the wellbore <NUM>. As discussed above, a temporal filtering system of the BOTDS system <NUM> may be able to distinguish between effects of the optical fiber strain component and the temperature component of the backscattered light signals based on the speed of change of the components. In an additional example, the process <NUM> removes the optical strain component of the temperature and optical fiber strain profile generated by the BOTDS system <NUM> by comparing the backscattered light signal to a baseline temperature profile and correcting portions of the backscattered light signal that depart from the baseline temperature profile. Accordingly, at block <NUM>, the process <NUM> involves receiving the backscattered light signals from the optical fiber at the BOTDS system <NUM> through the FORJ <NUM> and generating a temperature and optical fiber strain profile based on the backscattered light signals. As discussed above, the power of the light signals provided by the BOTDS system <NUM> using Brillouin scattering may be sufficient for the backscattered light signals to traverse the FORJ <NUM> with sufficient signal strength for the BOTDS system <NUM> to analyze the backscattered light signals.

At block <NUM>, the process <NUM> involves comparing, by the BOTDS system <NUM>, the temperature and optical fiber strain profile to a baseline temperature profile. The baseline temperature profile may include a general shape that a wellbore temperature is expected to follow as the optical fiber extends from the surface <NUM> of the wellbore <NUM> into the wellbore <NUM>. Any differences between the baseline temperature profile and the temperature and optical fiber strain profile may be attributable to the optical fiber strain characteristics.

At block <NUM>, the process <NUM> involves correcting the temperature and optical fiber strain profile for deviations from the baseline temperature profile to generate a temperature profile of the wellbore <NUM>. By removing the deviations from the temperature and optical fiber strain profile from the shape of the baseline temperature profile, the optical fiber strain effects on the temperature and optical fiber strain profile are isolated and removed. Accordingly, the resulting temperature profile is based on the measured temperature along the optical fiber disposed within the wellbore <NUM>.

<FIG> is a chart <NUM> depicting a temperature and optical fiber strain profile <NUM> of an optical fiber at the surface <NUM> of the wellbore <NUM> of the wellbore environment <NUM>. As illustrated, an abscissa <NUM> represents a length of the optical fiber. Further, an ordinate <NUM> represents a strain measurement along the optical fiber that is represented by the temperature and optical fiber strain profile <NUM>. In some examples, the ordinate <NUM> may represent a temperature measurement. In other examples, the ordinate <NUM> may represent a frequency of the backscattered light pulses. In an example, the strain measurement may be a change in length of the optical fiber over the entire length of the optical fiber, as measured by the BOTDS system <NUM> using the backscattered light signals received at the BOTDS system <NUM>. Within the optical fiber, there is a strong relationship between the frequency of the Brillouin backscattered light as depicted as a strain experienced by the optical fiber and temperature. For example, even though displayed as a strain, the temperature may be a significant contributor to the temperature and optical fiber strain profile <NUM> representative of the Brillouin backscattered light generated by the optical fiber. Accordingly, the temperature and optical fiber strain profile <NUM> provides a combined representation of a temperature component and an optical fiber strain component acting on the optical fiber. As discussed above, these components may be isolated to provide a temperature profile along the optical fiber or an optical fiber strain profile along the optical fiber.

As depicted in <FIG>, the temperature, represented by the temperature and optical fiber strain profile <NUM>, may increase along a length <NUM> of the optical fiber. In an example, this increase in temperature may be due to an optical fiber portion at an end <NUM> being at the surface (e.g., an outer layer) of the reel <NUM>, while an optical fiber portion at an end <NUM> may have layers of the optical fiber (e.g., within the conveyance subsystem <NUM>) providing insulation. Additionally, strain on the optical fiber due to the optical fiber exiting the reel <NUM> may also provide an increase in the strain at the end <NUM> of the optical fiber, as depicted in the temperature and optical fiber strain profile <NUM>.

<FIG> is a chart <NUM> depicting a temperature and optical fiber strain profile <NUM> of an optical fiber at a total depth of the wellbore <NUM> of the wellbore environment <NUM>. As illustrated, an abscissa <NUM> represents a length of the optical fiber. Further, an ordinate <NUM> represents a strain measurement along the optical fiber that is represented by the temperature and optical fiber strain profile <NUM>. In some examples, the ordinate <NUM> may represent a temperature measurement. In other examples, the ordinate <NUM> may represent a frequency of the backscattered light pulses. As discussed above with respect to <FIG>, the strain measurement may be represented by a change in length of the optical fiber over the entire length of the optical fiber. Within the optical fiber, there is a strong relationship between the frequency of the Brillouin backscattered light as depicted as a strain experienced by the optical fiber and temperature. For example, even though displayed as a strain, the temperature may be a significant contributor to the temperature and strain profile <NUM> representative of the Brillouin backscattered light generated by the optical fiber. Accordingly, the temperature and optical fiber strain profile <NUM> provides a combined representation of a temperature component and an optical fiber strain component acting on the optical fiber. As discussed above, these components may be isolated to provide a temperature profile along the optical fiber or an optical fiber strain profile along the optical fiber.

As depicted in <FIG>, the temperature, represented by the temperature and optical fiber strain profile <NUM>, may initially decrease gradually along a length <NUM> of the optical fiber as the optical fiber leaves the reel <NUM> and traverses the gooseneck <NUM> prior to insertion within the wellbore <NUM>. Upon entering the wellbore <NUM>, the optical fiber along a length <NUM> may quickly cool as the optical fiber enters the wellbore <NUM> and gradually heat up to reflect temperature changes in the wellbore <NUM> as the optical fiber extends deeper within the wellbore <NUM>.

<FIG> is a chart <NUM> depicting a temperature and optical fiber strain profile <NUM> of the optical fiber at total depth of the wellbore <NUM> of the wellbore environment <NUM> after reaching thermal equilibrium. As illustrated, an abscissa <NUM> represents a length of the optical fiber. Further, an ordinate <NUM> represents a strain measurement along the optical fiber that is represented by the temperature and optical fiber strain profile <NUM>. In some examples, the ordinate <NUM> may represent a temperature measurement. In other examples, the ordinate <NUM> may represent a frequency of the backscattered light pulses. The temperature, represented by the temperature and optical fiber strain profile <NUM>, may reach equilibrium within the wellbore after the optical fiber remains stationary for multiple hours. At equilibrium, the measured strain indicated in the temperature and optical fiber strain profile <NUM> may all be attributable to the temperature component because the strain on the optical fiber within the wellbore <NUM> after reaching equilibrium is unchanging.

As indicated by the similarity between <FIG> and <FIG>, measurements taken immediately after reaching the total depth of the wellbore <NUM> (or a total depth of the optical fiber) may be sufficiently similar to equilibrium temperature measurements such that the optical fiber is able to detect accurate information about the wellbore <NUM> even without reaching the temperature equilibrium. Further, the temperature and optical fiber strain measurements taken while the optical fiber is run into or out of the wellbore <NUM> may similarly provide accurate information to determine temperature and optical fiber strain. In one or more examples, the temperature and optical fiber strain measurements may also be taken while other downhole operations are being performed (e.g., wellbore stimulation, wellbore logging operations, perforating operations, etc.).

<FIG> is a chart <NUM> depicting a temperature and optical fiber strain profile <NUM> of an optical fiber while the optical fiber is being removed from the wellbore <NUM> of the wellbore environment <NUM>. As illustrated, an abscissa <NUM> represents a length of the optical fiber. Further, an ordinate <NUM> represents a strain measurement along the optical fiber that is representative of the temperature and optical fiber strain profile <NUM>. The temperature, represented by the temperature and optical fiber strain profile <NUM>, may still be accurately observed along a length <NUM> of the optical fiber as the optical fiber is reeled back to the reel <NUM> during removal from the wellbore <NUM>.

<FIG> is a chart <NUM> depicting two geothermal profiles <NUM> and <NUM> of the wellbore <NUM> of the wellbore environment <NUM> using measurements from the optical fiber (e.g., with the geothermal profile <NUM>) and measurements from a point temperature sensor (e.g., with the geothermal profile <NUM>). As illustrated, an abscissa <NUM> represents a depth of the measurement within the wellbore <NUM>. Further, a first ordinate <NUM> represents a strain measurement along the optical fiber that is represented by the geothermal profile <NUM>. A second ordinate <NUM> represents a temperature reading by the point temperature sensor that is represented by the geothermal profile <NUM>. The differences between the geothermal profiles <NUM> and <NUM> shows that the temperatures read by the point temperature sensor, and represented by the geothermal profile <NUM>, lag behind the strain measurements represented by the geothermal profile <NUM>. This lag may be the result of thermal inertia where the point temperature sensor has a slow heating effect due to a relatively large tool mass, thermal conductivity, and heat capacity. The inertial lag may effectively provide a low filter response to the measurements indicated by the geothermal profile <NUM> as the tool is advanced to the total depth within the wellbore <NUM>. With slope calibration (e.g., through the temporal filter system of the process <NUM> or the baseline fitting process <NUM>), the geothermal profile <NUM> may be smoothed of internal fiber strain variations to also provide a filtered response with greater accuracy. Further, because of the thermal inertia of the point temperature sensor, the point temperature sensor may be deployed within the wellbore <NUM> at a much slower rate than optical fiber to provide similar accuracy of the temperature measurements as the optical fiber measurements.

The foregoing description of certain examples, including illustrated examples, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or to limit the disclosure to the precise forms disclosed. Numerous modifications, adaptations, and uses thereof will be apparent to those skilled in the art without departing from the scope of the disclosure.

Claim 1:
A system, comprising:
an optical fiber integrated into a conveyance subsystem (<NUM>) that is positionable downhole in a wellbore (<NUM>);
a Brillouin optical time domain sensor system (<NUM>) positionable to monitor temperature and optical fiber strain along the optical fiber using backscattered light signals received from the optical fiber;
a fiber optic rotary joint (<NUM>) positionable to optically couple the optical fiber with the Brillouin optical time domain sensor system (<NUM>) to provide an optical path for the backscattered light signals to reach the Brillouin optical time domain sensor system (<NUM>); and
a temporal filtering system positionable to separate temperature components and optical fiber strain components from a temperature and optical fiber strain profile using a rate of change of the temperature components and the optical fiber strain components of the temperature and optical fiber strain profile generated by the Brillouin optical time domain sensor system (<NUM>).