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8/10/2019 3D OBC Seismic Survey Geometry Optimization Offshore Abu Dhabi_Jan 2012
3D OBC seismic survey geometry optimizationoffshore Abu Dhabi
T. Ishiyama,1,2* G. Mercado2 and K. Belaid2
IntroductionFor 3D seismic survey design, it is essential to understand the
geophysical requirements for achieving the business objectives
in the exploration, appraisal, and development of oil and gas
fields. We have to select survey parameters such as nominal
fold, bin size, and maximum and minimum offsets to meet
the required signal-to-noise ratio, signal frequency bandwidth,
and sharpness of focusing, as discussed by several authors
(e.g., Berkhout et al., 2001; Volker et al., 2001; Vermeer, 2002;
Galbraith, 2004). Furthermore, we must find a practical survey
geometry to meet the geophysical requirements. When we hunt
for it, we have to consider operational constraints imposed byequipment capability and productivity, which in turn affect the
survey time and cost. We naturally seek higher survey efficiency
within the operational constraints. Therefore, it is important to
optimize the survey geometry to satisfy not only the geophysi-
cal requirements but also the operational constraints.
Ocean bottom cable (OBC) seismic surveys are commonly
acquired offshore Abu Dhabi, United Arab Emirates due to
the shallow water depths and numerous scattered produc-
tion facilities. OBC seismic surveys have several advantages
(Bouska, 2008). One of them is that the receivers and airgun
sources are independently deployed, allowing acquisition
of high-fold, long-offset, wide-azimuth data. The flexibility
enables a variety of survey parameters and geometries to meetthe geophysical requirements.
Offshore Abu Dhabi, the main reservoirs are in the Lower
Cretaceous and Upper Jurassic successions, and are all carbon-
ate formations. It is not always easy to image the reflectors,
especially in the Upper Jurassic succession, due to the very low
acoustic impedance contrast.
Ishiyama et al. (2010) discussed the choice of 3D OBC seis-
mic survey parameters that would meet the geophysical require-
ments effectively and efficiently for a specific survey in the
region, based on the results of a feasibility study and a pilot sur-
vey. For an orthogonal geometry with receiver point and source
point intervals of 25 m, receiver line and source line intervals of
200 m, and wide-azimuth sampling, the nominal fold is 240 for
the natural bin size of 12.5 × 12.5 m2 with a maximum inline
offset of 3200 m and a maximum crossline offset of 3000 m.
This geometry was designated OR2B in Table 1 of Ishiyama et
al. (2010). For an areal geometry with parallel swath shooting,
receiver point interval of 25 m, source point interval of 50 m,receiver line interval of 400 m, source line interval of 50 m,
and wide-azimuth sampling, the nominal fold is 480 for the
natural bin size of 12.5 × 25 m2 with a maximum inline
offset of 3200 m and a maximum crossline offset of 3000 m.
This geometry was designated AR4A in Table 1 of Ishiyama
et al. (2010). Longer maximum offsets may be required when
survey targets are deeper, resulting in a higher nominal fold.
For example, the nominal fold changes to 300 for the geometry
OR2B and to 600 for the geometry AR4A in the natural bin size
if the maximum inline offset is increased to 4000 m.
Whilst retaining these fundamental survey parameters,
we have further analysed several geometry options to solve
limitations in equipment capability, in particular the limita-tions in the maximum number of receivers and length of
cables, and to pursue higher productivity. We then tried to
optimize the survey geometry. In this paper, we start with a
discussion about OBC seismic survey geometry, introduce a
methodology to analyse geometry options, and then discuss
several geometry options.
AbstractThe flexibility of 3D ocean bottom cable (OBC) seismic survey design allows a variety of survey geometries. Among the
infinite variations, we naturally seek higher survey efficiency within operational constraints whilst satisfying the geophysical
requirements. We have analysed several geometry and shooting options, such as zippers between panels, source line inter-
leave, flip-flop shooting, outboard shooting, and distance-separated simultaneous shooting (DS3), to show how the survey
geometry may be optimized to yield higher productivity within the limitations of the available equipment.
1 INPEX, Akasaka 5-3-1, Minato-ku, Tokyo 107-6332, Japan. Present address: Delft University of Technology, Faculty of Civil
Engineering and Geosciences, PO Box 5048, 2600 GA Delft, The Netherlands.2 ADMA-OPCO, PO Box 303, Abu Dhabi, UAE.* Corresponding author, E-mail: [email protected]
8/10/2019 3D OBC Seismic Survey Geometry Optimization Offshore Abu Dhabi_Jan 2012
technical article first break volume 30, January 2012
Figure 13 (a) Crossplots of productivity versus aspect ratio for i-roll-j receiver
line roll of OR2B with source zipper, source line interleave and DS 3 options.
The colour classifies i of i-roll-j, and the bubble size indicates required length
of cables. Plots with required length of cables more than 75 km are excluded.(b) Crossplots of productivity (on left vertical axis) and operations time per
patch (on right vertical axis) versus aspect ratio for 6-roll-j receiver line roll of
OR2B with these options. Colours indicate receiver effort in blue, source effort
in red, and consequent effort in green.
Figure 14 (a) Crossplots of productivity versus aspect ratio for i-roll-j receiver
line roll of AR4A with source zipper, flip-flop shooting, outboard shooting
and DS 3 options. The colour classifies i of i-roll-j, and the bubble size indicates
required length of cables. Plots with required length of cables more than75 km are excluded. (b) Crossplots of productivity (on left vertical axis) and
operations time per patch (on right vertical axis) versus aspect ratio for 8-roll-j
receiver line roll of AR4A with these options. Colours indicate receiver effort
in blue, source effort in red, and consequent effort in green.
Figure 16 Crossplots of productivity versus aspect ratio for i-roll-j receiver line
roll of OR2B with source zipper, source line interleave, and DS 3 options. The
colour classifies i of i-roll-j, and the bubble size indicates required length of
cables.
Figure 15 Bin attributes of (top) OR2B with 6-roll-3 receiver line roll, source
zipper, source line interleave and DS 3 options and of (bottom) AR4A with
8-roll-1 receiver line roll, source zipper, flip-flop shooting, outboard shooting
and DS 3 options. (a) Nominal fold in typical boxes. (b) The rose diagram in
a typical box (200 × 200 m 2 ). (c) Nominal fold in typical boxes. (d) The rose
diagram in a typical box (50 × 400 m 2 ).
8/10/2019 3D OBC Seismic Survey Geometry Optimization Offshore Abu Dhabi_Jan 2012
Cooper, N. [2004a] A world of reality – Designing land 3D programs for
signal, noise, and prestack migration – Part 1 of a 2-part tutorial. The
Leading Edge, 23, 1007–1014.
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1230–1235.
Galbraith, M. [2004] A new methodology for 3D survey design. The Leading
Edge, 23, 1017–1023.
Ishiyama, T., Painter, D. and Belaid, K. [2010] 3D OBC seismic survey param-
eters optimization offshore Abu Dhabi. First Break, 28(11), 39–46.
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[2010] Land seismic super-crew unlocks the Ara carbonate play of the
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Received 12 June 2011; accepted 27 October 2011.
doi: 10.3997/1365-2397.2011036
aspect ratio of 0.75 and uniform nominal fold of 300 in
the natural bin size of 12.5 × 12.5 m 2 with a maximum
inline offset of 4000 m and a maximum crossline offset
of 3000 m.
(b) AR4A with 8-roll-1 receiver line roll, source zipper, flip-
flop shooting, outboard shooting and DS3 options, pro-
viding an aspect ratio of 0.8 and uniform nominal fold of
640 in the natural bin size of 12.5 × 25 m 2 with a maxi-
mum inline offset of 4000 m and a maximum crossline
offset of 3200 m.
The bin attributes of these survey geometries (Figure 15)
show that these survey geometries satisfy the fundamental
survey parameters.
Figure 16 again shows crossplots of productivity versus
aspect ratio for i-roll- j receiver line roll of OR2B with source
zipper, source line interleave, and DS3 options. It should be
remembered that, in general, a larger number of i in i-roll- j
improves the productivity, and a larger number of j increasesthe aspect ratio. However, the limitation in the available
length of cables, which is about 75 km in the industry today,
makes it difficult to apply larger numbers of i and j. Some
desirable geometries are impractical due to this limitation. If
the availability of cables increases, more extensive receiver
spread can be allowed and practical survey geometries with
higher survey efficiency can be considered. We really look
forward to an increase in the available length of cables for
OBC seismic surveys.
Conclusions
As flexibility of 3D OBC seismic survey design allows avariety of survey geometries, the geometry should be selected
in such a way that it satisfies the geophysical requirements,
meets operational constraints, and produces higher survey
efficiency. We have analysed several geometry and shooting
options to deal with limitations in receive cable length, to
achieve higher productivity, and thus to optimize the survey
geometry. Whereas survey equipment and operations vary
field-to-field, contractor-to-contractor and time-to-time, this
exercise brings insights into achieving higher survey effi-
ciency within operational constraints.
Acknowledgements
We thank the managements of ADMA-OPCO and theshareholders, ADNOC, BP, Total, and INPEX, for their
support and permission to publish this paper. We also thank
Andreas Cordsen, Derrick Painter, and Jack Bouska for their
discussions on this study.
ReferencesBeasley, C.J. [2008] A new look at marine simultaneous sources. The
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Berkhout, A.J., Ongkiehong, L., Volker, A.W.F. and Blacquiere, G. [2001]
Comprehensive assessment of seismic acquisition geometries by focal
beams – Part I: Theoretical considerations. Geophysics, 66, 911–917.
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