href="#ulink_6c7df7a6-c1cf-5448-a760-6d939fd5ef35">Figure 1.18 The left‐hand panel shows a single shot of raw acoustic data; th...Figure 1.19 Comparison of DAS performance with SM and MM optical fiber.Figure 1.20 Directionality of DAS response: The left and central panels repr...Figure 1.21 3D VSP: Two intersecting images processed from DAS seismic data ...Figure 1.22 DAS hydraulic fracture monitoring in the treatment well with a f...Figure 1.23 DAS hydraulic fracture monitoring in the offset (a) with a fine ...Figure 1.24 DAS with standard fiber and engineered fiber with precision brig...Figure 1.25 Optical fiber with defined scatter center zones and the correspo...Figure 1.26 Acoustic measurements using DAS with precision engineered fiber:...Figure 1.27 Comparison of DAS with engineered fiber spectral response for sp...Figure 1.28 Ultimate SNR spectral response of DAS with standard and engineer...Figure 1.29 Displacement noise comparison of DAS (with and without engineere...Figure 1.30 Maximum strain comparison of first and second order algorithms f...Figure 1.31 Comparison of DAS with Rayleigh scattering [(a) and (b)] and eng...Figure 1.32 Comparison of DAS noise spectrums with Rayleigh scattering (a) a...Figure 1.33 Microseismic event in observation well detected by DAS with engi...Figure 1.34 Example of low frequency (down to millihertz level) “slow strain...Figure 1.35 Comparison of geophones (left panel) and DAS with engineered fib...2 Chapter 2Figure 2.1 Options for acquiring DAS VSP data in a well.Figure 2.2 (Left) Conceptual diagram of an IU (inside the dotted black line)...Figure 2.3 (Top) Location of first spectral notch for a range of gauge lengt...Figure 2.4 Recommended pulse width as a function of gauge length.Figure 2.5 (Top) I (blue) and Q (orange) traces; (middle) corresponding rela...Figure 2.6 Strain rate VSP data collected with a vibrator – (top row) uncorr...Figure 2.7 (a) single sweep using Frequency 1 – note the prominent fading at...Figure 2.8 (Left) Strain rate record showing common‐mode noise; (right) same...Figure 2.9 Angular response of the fiber to P waves (left) and S waves (righ...Figure 2.10 Relationship among the various products created from a DAS data ...
3 Chapter 3Figure 3.1 Schematic principle of the fiber optic DAS system.Figure 3.2 Schematic of DMOF.Figure 3.3 Simulated intensity distribution along fiber when the intensity o...Figure 3.4 The block diagram of the continuous online DMOF fabrication syste...Figure 3.5 Comparison between the DMOF and the SMF: (a) Spectra of the backs...Figure 3.6 Working principle of DMOF‐DAS: (a) System configuration and (b) p...Figure 3.7 Sensing performance of the DMOF‐DAS system: (a) Photograph of the...Figure 3.8 Field test in the Fushan oil field: (a) Schematic of the zero‐off...Figure 3.9 Recorded seismic data in well using DMOF‐DAS: (a) DMOF‐DAS VSP da...
4 Chapter 4Figure 4.1 Principle of PGC‐DAS system with an unbalanced MI.Figure 4.2 Setup of PGC‐DAS system.Figure 4.3 Phase noise of PGC‐DAS system on Channel #4750: (a) Time series a...Figure 4.4 Intensity map of demodulation magnitude of each channel: (a) Wate...Figure 4.5 Time domain and STFT spectrogram of sweeping frequency signal.Figure 4.6 Amplitude response curve of PGC‐DAS system.Figure 4.7 Field trial of near‐surface seismic experiment. (a) Plan view of ...Figure 4.8 Initial data of DAS system and geophone array for x‐component at ...
5 Chapter 5Figure 5.1 (a) Map of the Lafarge‐Conco mine (presented with permission of L...Figure 5.2 (a) Sketch of a cross‐section showing the emplacement of co‐locat...Figure 5.3 Waveforms and spectra for different source locations recorded on ...Figure 5.4 Ambient noise records at Location E (left column) and Location H ...Figure 5.5 (a) Wavefield for all three cable loops for the source at Locatio...Figure 5.6 (a) Amplitude decay curves for Loop 1. Crosses show the amplitude...Figure 5.7 (a) Time vs. channel number plot for Loop 1 for the blast execute...Figure 5.8 (a) Stacked traces for Loop 1 for the ESS source at Location B. B...Figure 5.9 (a) Sample ray paths for surface wave tomography using the ESS so...Figure 5.10 (a) Example waveforms and first arrivals from channel pair 390 a...Figure 5.11 P‐wave differential travel‐time tomogram.
6 Chapter 6Figure 6.1 Absolute depth calibration using DAS receiver scalars (red and bl...Figure 6.2 Relative depth calibration between time‐lapse DAS VSP vintages (i...Figure 6.3 The impact (before/after) of relative depth calibration on 4D att...Figure 6.4 Ray contributions in deviated well – directionality consideration...Figure 6.5 3D/4D DAS VSP from flowing wells: (a) Geometry of 2017 simultaneo...Figure 6.6 Repeatability of DAS VSP images from flowing wells: (a) From Well...Figure 6.7 4D signals obtained from DAS VSP in Well W2 (2015–2017) compared ...
7 Chapter 7Figure 7.1 Three types of DAS‐VSP optical fiber deployment in a borehole. (a...Figure 7.2 DAS‐VSP data received by optical fibers freely suspended in the c...Figure 7.3 Comparison of VSP single‐shot record received from (a) flexible o...Figure 7.4 Diagram of cable resonance interference.Figure 7.5 The denoising effect of cable resonance. (a) Record before denois...Figure 7.6 DAS‐VSP recording before (a) and after (b) F‐X denoising.Figure 7.7 Before and after improved
