OVERVIEW

Halliburton FiberVSP™ service is one of the latest technologies in our family of fiber-optic services. Our FiberVSP service uses a Distributed Acoustic Sensing (DAS) technology for Vertical Seismic Profile (VSP) data acquisition. It provides a cost-effective complement to conventional VSP acquisition, and is ideally positioned for time-lapse VSP studies. This service also includes data processing and interpretation for a wide range of borehole seismic applications, such as surface seismic calibration, structural imaging, reservoir characterization and surveillance, steam-assisted gravity drainage (SAGD) reservoir monitoring, and microseismic monitoring.

APPLICATIONS

» Calibrate surface seismic (average/interval/RMS velocities, acoustic log calibration, synthetic seismograms)

» Validate surface seismic attributes (true wavelet tie using phase, frequency, time/depth; multiple identification, prediction beneath bit, Q estimation)

» Acquire complex high-resolution 2D and 3D P- and S-wave imaging of reservoir boundaries, fault identification, time-lapse 4D studies, fluid-movement mapping

EXAMPLES OF FIBERVSP APPLICATIONS

Standard VSPBasic FiberVSP products include time-depth calibration, interval velocities, corridor stack, and zero-offset and offset reflection images. These products can be produced from various types of FiberVSP acquisitions at lower costs and using less rig time than conventional VSP surveys with geophones. The products provide high-resolution solutions that bridge the gap between surface seismic and the wellbore to improve reservoir analysis.

Fig. 1 shows near-offset and mid-offset shot records acquired using vertical vibrators with a linear source sweep of 6 to 96 Hz. The fiber-optic cable was cemented behind casing. The data set also includes far-offset source and shear-source records. Fig. 1c illustrates P- and S-wave interval velocities as well as Vp/Vs ratios for surface seismic time-depth conversion, velocity model calibration, and seismic inversion for reservoir characterization. Fig. 1d compares P-wave corridor stack and CDP transform of mid- and far-offset reflection images.

FiberVSP™ Applications DISTRIBUTED ACOUSTIC SENSING (DAS) FOR VSP

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Fig. 1. FiberVSP™ waveform of near-offset (a) and mid-offset (b) records, interval velocities (c), and correlation of corridor stack with mid- and far-offset reflection images (d).

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LEVEL 1 CAPABILITY | Level 2 Capability (if applicable)FORMATION EVALUATION | Geophysics Borehole Seismic Services

Anisotropy Measurement and Structural ImagingSeismic anisotropy in shales and shaly sands is common for conventional and unconventional oil and gas reservoirs. A FiberVSP™ survey with walkaway source offsets (or multiple offsets) provides spatial and angle coverage for estimating vertical transverse isotropy (VTI). This type of survey also provides lateral and depth coverage for high-resolution imaging around the well.

Fig. 2 illustrates a multi-offset FiberVSP survey geometry. Data include four source offsets from near to far offsets. The fiber-optic cable was cemented behind casing, and the data was acquired using vertical vibrators with a linear source sweep of 6 to 96 Hz. The recorded data were converted to strain rate and then processed using standard procedures for single-component VSP to extract reflected P-waves.

A 1D blocky velocity model was obtained from the near-offset data. A 2D layered model with VTI was created from direct P-wave traveltimes of all four shot records. The traveltimes picked from the horizontal part of the DAS channels helped constrain the VTI model. The target interval around the lateral well was imaged using the upgoing P-waves with this VTI model.

The image demonstrates the feasibility of extending the image to cover a lateral well with FiberVSP data. The VTI model and structural image provide subsurface insight for hydraulic stimulation planning and microseismic monitoring.

Time-Lapse 4D ApplicationsThe ability to access and interrogate the fiber-optic cable without well intervention affords the opportunity to perform 4D time-lapse reservoir imaging. Large-scale 3D VSP can be reacquired frequently at greatly reduced costs and with increased repeatability as a benefit of permanently installed fibers. In addition, monitoring hydraulic fracturing operations can be performed in a rapid time-lapse capacity, using compression or shear vibrator sources. As an answer product, this may enable direct seismic detection of fracturing efficiency and estimation of the stimulated reservoir volume.

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Fig. 2. Multi-offset FiberVSP survey geometry (a), P-wave vertical interval and blocky velocities from zero-offset data (b), waveform of four shot records acquired with vertical vibrators (c), layered VTI model (d), and P-wave reflection image in depth (e).

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LEVEL 1 CAPABILITY | Level 2 Capability (if applicable)FORMATION EVALUATION | Geophysics Borehole Seismic Services

For more information, contact your local Halliburton representative or visit us on the web at www.halliburton.com/FiberVSP

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