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8/3/2019 Channel Tracing25 05

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Channel tracing using seismic

attribute data

By Schlumberger DCS Moscow team: Mikhail Gostev,Mikhail Kourenko, Veronica Grabskaya


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Starting point The initial data was structure map(based on seismic interpretation)and log response curves, clearly

identifying channel section. Thethickness of body (22 m) anddepth (2450 m) suggest, thatobject fits within lower marginvertical seismic resolution.


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Starting point Seismic amplitude sectionprovided clear signal (blue

phase) in the interval ofinterest.


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Starting point But it didnt give much hints onthe spatial distribution of the

body.


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Workflow Series of seimic mapsbetween surfaces

confining the interval ofinterest were built then (aprimitive Petrel workflowwas used to generate apack of maps of the sameinterval, but different

summing formula to assesthe differences insumming method & thenchoose the mostrepresentative one)

Still no major insights.So we started looking forattribute to visualize thedimensions and locationof channel body.

Seismic map: interval average amplitude (minimum)


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Attribute analysis -EnvelopeSome signal in the interval of

interest (though too wide).


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Attribute analysis -Envelope Interval average attributemaps: it can be seen here,that best signal comes fromzones of structrural high,which is not appropriateposition for the channel*.*In the platform environment like the one we have, there is noevidences, that structrural style was inverted so much that itcannot serve as qualitative representation of paleotopography

Seismic map: interval average envelope (arithmetic)


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Attribute analysis - Variance didnt give any signal in interval of interest at all.

Relative Acoustic ImpedanceGave clear signal in the vicinity of well tops, so we shifted to attribute maps


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Attribute analysis- RelativeAcoustic

ImpedanceThe geometric summinggave first clues (see zonewith zero-signal)


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Attribute analysis- RelativeAcoustic

ImpedanceMininum summing(remember, that onsection, the bottom of thechannel was marked withnegative blue phase)gave us picture that weassumed satisfactory andshifted to modeling.


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ModelingThe latter workflow wasordinary wed builtpolygons marking thechannel belt margin andpresumable axis.


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ModelingThen, used Channelsoption Artificial

Algorithms in Make/Edit

Surface process to drawan artificial grossthickness map of channelbody. The requestedinput parameters likewidth and thickness ofchannel were decidedfrom regional geologicdata and then adjusted tofit in observed data.

The resulting artificial

isohore map was thenused in Make Zonesprocess*

*the goal of the modeling was to get a zonewith separate layering scheme in already builtmodel with non-alterable number of horizons,so we didnt try to model it as horizon, though

realizing that modeling channel based onartificial isohore map isnt the most effectivetechnique.


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Notes

Spectral decomposition (isofrequency analysis)didnt give much result (at least in GGshands), although wed extracted a waveletaround the object interval & scanned theeffective frequency interval with 3 hz increment.

Unfortunately, there will be no chance to validatethe model in the near future, for no drilling isplanned in the area now.

The overall workflow starting with log data andhorizon interpretation and finishing withcomplete structural model, took ~1 week.


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Thanks

Wed like to thank everyone who gavefeedback on PetrelBB inquiry: Sergei Filin ,Alexis Carrillat , Andy MacGregor , JayantaRay , Mohamed Sobhy and Dr. LotharSchulte .

Special thanks to Gaston Bejarano for

pointing out Rel. Ac. Impedance attribute andexpress seismic processing & handlingworkshop he conducted with us exactly atthe right moment.

channel tracing25 05

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