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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
ABSTRACT: Subsurface Imaging with
VSP
and Ocean Bottom
Seismometers (OBS): Novel Acquisition Designs
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Recording of ocean‐bottom seismometer (OBS) data
has several advantages over conventional near‐surface recording. Because of
their deployment on the sea floor, OBS are less vulnerable to noise and disturbances in the water column and thus have a relatively
higher signal‐to‐noise ratio. OBS also offers wide‐azimuth (WAZ) and full‐azimuth (FAZ) geometries, which are important for imaging
the complex structures such as salt domes. Vertical seismic profile (
VSP
) reflection surveys help to define a salt‐sediment interface
near a wellbore by using offset sources.
VSP
with circular shooting has been using for
3D
imaging near the borehole.
VSP
itself,
however, still has some limitations such as poor offset and angular coverage per bin and limited total bin fold. This imaging limitation
in the
VSP
can be lessened by combining ocean‐bottom seismometers on the sea floor with the
VSP
borehole survey. We show a
number of model examples using combined borehole and ocean‐bottom recordings to improve azimuth, offset and fold distribution.
Survey designs were created in OMNI
3D
to compare and examine.
We use 10 concentric circles separated by 200m and 50m shot interval to create circular shooting geometry. Same shooting geometry
was used to create joint VSP
and OBS survey. The results show that the joint
VSP
and OBS survey has better fold, offset and azimuth
distribution than
VSP
itself.