Applying Gamma Ray and Azimuthal Density LWD Images in ... · PDF fileApplying Gamma Ray and...
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Applying Gamma Ray and Azimuthal Density LWD Images in Well-
to-Well Correlation and Homogeneous Reservoir Characterization
Constantin Ciuperca
May 07, DEVEX 2014, ABERDEEN
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Geological setting
Independenţa oilfield structure belongs geologically to the North
Dobrogea headland platform on the border of Scytian and Moesian
Platform.
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Reservoir lithology description
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Azimuthal Gamma Ray
Geiger–Müller tubes
Output:
– Total GR
– Up / Down GR
– Up / Down / Left / Right quadrant curves
– 4-Bin Borehole Image (Real Time)
– 8-Bin Borehole Image (Recorded)
4-3/4” Insert
10 tubes (5 x 2)
6-3/4” Insert
16 tubes (8 x 2)
8-1/4 & 9-1/2” Insert
18 tubes (6 x 3)
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Azimuthal Density
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As the tool rotates, X- and Y-
axis magnetometers track the
orientation of the detector
blade.
Count rates are recorded every
25 milliseconds, and sorted into
16 azimuthal bins.
RHOB, DRHO, and Pe are
computed for each of the 16
bins.
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Well B Design
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Real Time Well to Well Corelation
Reservoir tops were correlated using offset gamma ray and resistivity
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Real Time Well to Well Corelation
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Real Time 6” Density Image Interpretation for
Geosteering
Difficult geosteering environment with a lack of obvious geologic
markers
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Real Time Density Image Interpretation for
Geosteering
Cross section illustrating bedding planes parallel to the borehole
trajectory
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Density vs Gamma Ray Memory Image
Despite a homogeneous reservoir, a density variation does exist
allowing for some structural interpretation
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Azimuthal Density Standoff and Caliper
The density standoff and caliper
values are derived from the
spread of the compensated and
short-spaced density values,
nomalized by the difference
between formation density and
mud density.
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Borehole Quality Plot
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Conclusions
Geosteering is required in the Independenta field because
of the necesity to keep the trajectory above OWC
However, it appears to be difficult because of a lack of
geologic markers
Total gamma ray alone would not allow for sufficient
geosteering information
When combined with an azimuthal density, geosteering
decisions were still possible
Azimuthal density also allowed the proper placement of
the liner centralizers via the caliper measurement