Abstract: A fiber optic sensing (FOS) system and method. The system may include one or more interrogator units and a proximal wavelength division multiplexer (WDM) and a distal WDM optically connectable to the one or more interrogator units, an upgoing transmission fiber, a down-going transmission fiber, and one or more downhole sensing fibers. The method may include transmitting one or more light pulses from an interrogator unit, multiplexing the one or more light pulses from the interrogator unit with a proximal WDM into an upgoing transmission fiber and a down-going transmission fiber, and receiving the one or more light pulses with a distal WDM. The method may further include multiplexing the one or more light pulses from the upgoing transmission fiber and the down-going transmission fiber into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.

Abstract: A method for tuning a distributed acoustic sensing (DAS) system. The method may include determining a signal strength from a first Raman Pump in the DAS system, sweeping a laser pulse output from a transmitter; wherein the sweeping is an incremental increase of a power of the laser pulse output from a minimum pulse power to a maximum pulse power, and measuring a first signal-to-noise-ratio (SNR) for each of the incremental increase of the power of the laser pulse output. The method may further comprise selecting a maximum SNR from the first SNR for each of the incremental increase of the power of the laser pulse output and configuring the first Raman Pump and the laser pulse output based at least in part on the maximum SNR.

Abstract: A fiber optic sensing (FOS) system and method. The system may include one or more interrogator units and a proximal wavelength division multiplexer (WDM) and a distal WDM optically connectable to the one or more interrogator units, an upgoing transmission fiber, a down-going transmission fiber, and one or more downhole sensing fibers. The method may include transmitting one or more light pulses from an interrogator unit, multiplexing the one or more light pulses from the interrogator unit with a proximal WDM into an upgoing transmission fiber and a down-going transmission fiber, and receiving the one or more light pulses with a distal WDM. The method may further include multiplexing the one or more light pulses from the upgoing transmission fiber and the down-going transmission fiber into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.

Abstract: An active fiber stretcher assembly can be used for data acquisition systems. A time-break signal can be detected that coincides with a seismic event emitted from a seismic controller. A predetermined waveform can be generated in response to detecting the time-break signal. The predetermined waveform may be encoded onto a fiber optic cable using a fiber stretcher. A data acquisition system connected to the fiber optic cable may detect the predetermined waveform on the fiber optic cable and initiate acquisition operations including: receiving, during the seismic event, light signals returning from a portion of the fiber optic cable in a subterranean environment; determining one or more characteristics of the subterranean environment from the light signals; and storing the one or more characteristics.

Abstract: Distributed sensing systems and methods with spatial location correlation of a reflection produced along an electromagnetic (EM) waveguide. A distributed sensing system comprises an EM waveguide, a distributed sensing interrogator, and a processor. The distributed sensing interrogator comprises a transmitter coupled to the EM waveguide and generates an interrogation pulse through the EM waveguide. The distributed sensing interrogator also comprises a receiver coupled to the EM waveguide and responsive to backscattered EM waves propagating through the EM waveguide. The processor determines a spatial location associated with a reflection produced along the EM waveguide using a return signal generated from the reflection by the interrogator and an interrogation signal including the interrogation pulse.

Abstract: A method and system for a fiber optic sensing (FOS) system. The system may include an interrogator that is marinized to be disposed on a sea floor, a fiber optic cable optically connected to the interrogator, and one or more downhole sensing fibers optically connected to the fiber optic cable. The method may include disposing the interrogator on the sea floor and connecting the interrogator to a fiber optic cable. The method may further include connecting one or more downhole sensing fibers to the fiber optic cable and taking one or more measurements using the interrogator.

Abstract: A method for tuning a distributed acoustic sensing (DAS) system. The method may include determining a signal strength from a first Raman Pump in the DAS system, sweeping a laser pulse output from a transmitter; wherein the sweeping is an incremental increase of a power of the laser pulse output from a minimum pulse power to a maximum pulse power, and measuring a first signal-to-noise-ratio (SNR) for each of the incremental increase of the power of the laser pulse output. The method may further comprise selecting a maximum SNR from the first SNR for each of the incremental increase of the power of the laser pulse output and configuring the first Raman Pump and the laser pulse output based at least in part on the maximum SNR.

Abstract: A fiber optic sensing (FOS) system and method. The system may include one or more interrogator units and a proximal wavelength division multiplexer (WDM) and a distal WDM optically connectable to the one or more interrogator units, an upgoing transmission fiber, a down-going transmission fiber, and one or more downhole sensing fibers. The method may include transmitting one or more light pulses from an interrogator unit, multiplexing the one or more light pulses from the interrogator unit with a proximal WDM into an upgoing transmission fiber and a down-going transmission fiber, and receiving the one or more light pulses with a distal WDM. The method may further include multiplexing the one or more light pulses from the upgoing transmission fiber and the down-going transmission fiber into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.

Abstract: A distributed acoustic system (DAS) may comprise an interrogator and an umbilical line attached at one end to the interrogator, a downhole fiber attached to the umbilical line at the end opposite the interrogator. The interrogator may further include a proximal circulator, a distal circulator connected to the proximal circulator by a first fiber optic cable, and a second fiber optic cable connecting the proximal circulator and the distal circulator.

Abstract: A fiber optic sensing (FOS) system may include a Brillouin Optical Time Domain Analyzer (BOTDA) unit, a first fiber optical cable optically connected to the BOTDA interrogator unit at a first end, and an optical feedthrough system (OFS) optically connected the first fiber optical cable at a second end of the first fiber optical cable. The FOS system may further comprise a fiber optic cable forming a loop within a wellbore that is optically connected to the first fiber optical cable at the OFS and a second fiber optical cable optically connected to the loop at the OFS and wherein the second fiber optical cable is optically connected to the BOTDA interrogator unit.

Abstract: A wellbore system includes a logging unit having a retrievable logging cable coupled to a downhole tool within a wellbore and a depth correlation unit in the downhole tool that provides current depth data for the wellbore through the retrievable logging cable for recording of a current depth by the logging unit. The wellbore system also includes a distributed acoustic sensing unit that includes a seismic processing unit and a seismic profiling unit connected to a separate optical cable of the retrievable logging cable having distributed acoustic sensing channels, wherein an assignment of the distributed acoustic sensing channels along the separate optical cable is determined by an offset distance between the current depth of a formation reference region within the wellbore and a previous reference depth of the formation reference region within the wellbore. A distributed acoustic sensing method is also included.

Abstract: A fiber optic sensing (FOS) system may include a Brillouin Optical Time Domain Analyzer (BOTDA) unit, a first fiber optical cable optically connected to the BOTDA interrogator unit at a first end, and an optical feedthrough system (OFS) optically connected the first fiber optical cable at a second end of the first fiber optical cable. The FOS system may further comprise a fiber optic cable forming a loop within a wellbore that is optically connected to the first fiber optical cable at the OFS and a second fiber optical cable optically connected to the loop at the OFS and wherein the second fiber optical cable is optically connected to the BOTDA interrogator unit.

Abstract: A distributed acoustic system (DAS) may include an interrogator that includes two or more lasers, a pulser module disposed after and connected to each of the two or more lasers, a wavelength division multiplexer (WDM), wherein each of the pulser modules are connected to the WDM as inputs, and a downhole fiber attached to the WDM as an output and wherein the downhole fiber includes at least one sensing fiber. A method for increasing a sampling frequency may include identifying a length of a downhole fiber connected to an interrogator, generating and launching a light pulse from each of the two or more lasers the pulser module, and delaying an output from the pulser module into the downhole fiber by k N seconds, where k is a pulse repetition interval of the pulser module and N is equal to the two or more lasers.

Abstract: A distributed acoustic system (DAS) may include an interrogator that includes two or more lasers, a pulser module disposed after and connected to each of the two or more lasers, a wavelength division multiplexer (WDM), wherein each of the pulser modules are connected to the WDM as inputs, and a downhole fiber attached to the WDM as an output and wherein the downhole fiber includes at least one sensing fiber. A method for increasing a sampling frequency may include identifying a length of a downhole fiber connected to an interrogator, generating and launching a light pulse from each of the two or more lasers the pulser module, and delaying an output from the pulser module into the downhole fiber by k N seconds, where k is a pulse repetition interval of the pulser module and N is equal to the two or more lasers.

Abstract: Systems and methods relate to borehole seismic studies. Traditionally, borehole seismic studies are conducted using geophones. Seismic acquisition can be performed using fiber optic Distributed Acoustic Sensing (DAS). Because DAS measures dynamic relative displacement over a gauge length, which is different from particle velocity, DAS data can be converted into an equivalent geophone output response. Operations include converting DAS data into distributed velocity, and then, converting the velocity output into an equivalent geophone response. Various aspects include separating the data into interleaving subsets, integrating each subset along the spatial coordinates, selecting a window width over which the median of each subset will be calculated and subtracted from the data, performing a spatial average or low-pass filtering over contiguous values, performing a time-domain low-pass filtering, and performing the velocity-to-geophone conversion operation.

Abstract: A method and system for fiber optic communication and sensing (FOCS) may include transmitting one or more measurement signals from an interrogator unit that is optically connected to a proximal wavelength division multiplexer (WDM), transmitting one or more communication signals from an information handling system that is optically connected to a proximal wavelength division multiplexer (WDM), multiplexing the one or more measurement signals and the one or more communication signals with the proximal WDM into a first fiber optic cable, and receiving the one or more measurement signals and the one or more communication signals with a distal WDM that is optically connected to the first fiber optic cable. The method may further include multiplexing the one or more measurement signals from the first fiber optic cable into one or more downhole sensing fibers and receiving backscatter light from at least one of the one or more downhole sensing fibers.

Abstract: A distributed acoustic system (DAS) method and system. The system may comprise an interrogator and an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator. The DAS may further include a downhole fiber attached to the umbilical line at the end opposite the interrogator and a light source disposed in the interrogator that is configured to emit a plurality of coherent light frequencies into the umbilical line and the downhole fiber. The method may include generating interferometric signals of the plurality of frequencies of backscattered light that have been received by the photo detector assembly and processing the interferometric signals with an information handling system.

Abstract: A distributed acoustic system (DAS) method and system. The system may comprise an interrogator and an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator. The DAS may further include a downhole fiber attached to the umbilical line at the end opposite the interrogator and a light source disposed in the interrogator that is configured to emit a plurality of coherent light frequencies into the umbilical line and the downhole fiber. The method may include generating interferometric signals of the plurality of frequencies of backscattered light that have been received by the photo detector assembly and processing the interferometric signals with an information handling system.

Abstract: Embodiments disclosed herein include components, devices, systems, and operations and functions for generating a seismic profile. An optical signal is generated in an optical signal medium disposed in proximity to a formation. A seismic source induces seismic signals within the formation. A backscatter response corresponding to the seismic signals from the optical signal medium is detected and quadrature modulated to generate a quadrature trace. A seismic response is generated by determining phase differences in the backscatter response based on the quadrature modulated backscatter response. Portions of the seismic response above or below a response threshold are removed to generate a threshold seismic response. The threshold seismic response is correlated with at least one of the seismic signals to generate a correlated seismic response.

Abstract: A distributed acoustic sensing (DAS) system for determining an acoustic event may include an interferometer and an acoustic event detection processing device. The interferometer may measure DAS data from sensed signals from a sensing fiber deployed in a wellbore. The acoustic event detection processing device may determine an acoustic event in the wellbore from an out-of-band signal using the DAS data by performing operations. The operations can include determining a first acoustic event and a second acoustic event from the DAS data. The operations can include determining a first set of aliased frequencies from the first acoustic event and a second set of aliased frequencies form the second acoustic event. The operations can include determining, using an intersection of the first set of aliased frequencies and the second set of aliased frequencies, a frequency or amplitude of out-of-band signals that are usable to determine the at least one acoustic event.