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 apparatus comprises a distributed acoustic sensing (DAS) optical fiber, a DAS interrogator coupled to the DAS optical fiber, and a connector. The connector couples the DAS interrogator, a first digitizer, and a second digitizer, wherein the first digitizer is to generate a first digitized DAS signal based on an analog DAS signal from the DAS interrogator, and the second digitizer is to generate a second digitized DAS signal based on the analog DAS signal. The apparatus also comprises one or more processors and a machine-readable medium having program code executable to cause the apparatus to simultaneously generate a first set of values that correlate with a first physical property based on the first digitized DAS signal and generating a second set of values that correlate with a second physical property based on the second digitized DAS signal.

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: A system for processing DAS VSP surveys in real-time is provided. The system includes a DAS data collection system coupled to at least one optical fiber at least partially positioned within a wellbore and configured to repeatedly activate a seismic source of energy. The system further includes an information processing system connected to the DAS data collection system. A seismic dataset is received from the DAS data collection system. The seismic dataset includes a plurality of seismic data records. Two or more of the plurality of seismic data records are combined into a stack. A quality metric indicative of a desired signal-to-noise ratio or incoherence of the stack is determined for each processed seismic dataset collected from a repeated source. Instructions are sent to the DAS data collection system to stop activating the seismic source, in response to determining that the quality metric has reached a predefined threshold.

Abstract: A system for downhole measurements. The system may comprise a fiber optic cable that further comprises a transmission fiber and a return fiber. Additionally, the system may comprise a passive optical device optically connected to the transmission fiber and the return fiber, a first wavelength division multiplexer (WDM) optically connected to the transmission fiber, and a second WDM optically connected to the return fiber. The system may further comprise a transmitter and a first Raman pump optically connected to the first WDM and a receiver and a second Raman pump optically connected to the second WDM.

Abstract: A distributed acoustic system may comprise an interrogator which includes a single photon detector, an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator, and a downhole fiber attached to the umbilical line at the end opposite the interrogator. A method for optimizing a sampling frequency may comprise identifying a length of a fiber optic cable connected to an interrogator, identifying one or more regions on the fiber optic cable in which a backscatter is received, and optimizing a sampling frequency of a distributed acoustic system by identifying a minimum time interval that is between an emission of a light pulse such that at no point in time the backscatter arrives back at the interrogator that corresponds to more than one spatial location along a sensing portion of the fiber optic cable.

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 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 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 system and method for synchronizing a data stream. The system may include one or more acoustic sources, an information handling system disposed on a platform, a GPS module connected to the information handling system, and a fiber optic cable connected to the information handling system. The method may include transmitting one or more acoustic waves from one or more acoustic sources, sensing the one or more acoustic waves with a fiber optic cable to form a data stream, sending the data stream to an information handling system through the fiber optic cable, communication a time and a location to a GPS module attached to the information handling system with one or more global positioning system (GPS) devices, and modulating the time and the location to the data stream with a fiber optic phase modulator.

Abstract: A distributed fiber sensing system and method of use. The system may comprise an interrogator configured to receive a Brillouin backscattered light from a first sensing region and a second sensing region, a first fiber optic cable optically connected to the interrogator, a proximal circulator, and a distal circulator, and a second fiber optic cable optically connected to the interrogator, the proximal circulator, and the distal circulator. The system may further comprise a downhole fiber optically connected to the first fiber optic cable and the second fiber optic cable and wherein the first sensing region and the second sensing region are disposed on the downhole fiber. The method may comprise generating and launching a light pulse from an interrogator and through a first fiber optic cable to a downhole fiber and receiving a Brillouin backscattered light from a first sensing region and a second sensing region.

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: To mitigate zigzag noise and increase the quality of data provided from DAS VSP in wells with significant vertical sections, zigzag noise characteristics are identified and quantified. The zigzag noise properties can be extracted from an analysis of an autocorrelation of DAS VSP traces. The zigzag noise has a characteristic time period or repeat time delay that is the time period for the noise to propagate along the wireline through a zone of the wellbore with poor acoustic coupling between the fiber optic cable and formation. This period can be identified from analysis of the autocorrelation referred to herein as a crosswise lag summation function. The crosswise lag summation function identifies groups of DAS data traces containing zigzag noise and outputs zigzag noise periodicity for each group of traces. Once it has been identified, the zigzag noise can be removed from the VSP data and improve formation evaluation.

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 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: 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: 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: The subject technology relates to an in-line amplifier assembly for distributed sensing system. The subject technology includes deploying a distributed sensing tool into a wellbore, and logging the wellbore using the distributed sensing tool. The distributed sensing tool includes a first optical amplifier and a first optical filter coupled to a first single-mode optical fiber. The first optical amplifier is coupled to a first single-mode circulator for amplifying a single-mode optical signal, and the first optical filter is coupled to the first optical amplifier for filtering the amplified single-mode optical signal. The first single-mode circulator is coupleable to an interrogator for routing the single-mode optical signal to a second single-mode optical fiber and routing a reflective optical signal from a second single-mode optical fiber to the interrogator. The reflective optical signal may traverse a second optical amplifier and a second optical fiber between the first and second single-mode circulators.

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) 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.