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© 2014 Weatherford. All rights reserved. © 2014 Weatherford. All rights reserved.

Applying Gamma Ray and Azimuthal Density LWD Images in Well-

to-Well Correlation and Homogeneous Reservoir Characterization

Constantin Ciuperca

May 07, DEVEX 2014, ABERDEEN

© 2014 Weatherford. All rights reserved.

Geological setting

Independenţa oilfield structure belongs geologically to the North

Dobrogea headland platform on the border of Scytian and Moesian

Platform.


Reservoir lithology description


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)


Azimuthal Density

5

1

2

3

4

5

6

7 8 9

10

11

12

13

14

15

16

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.


Well B Design


Real Time Well to Well Corelation

Reservoir tops were correlated using offset gamma ray and resistivity


Real Time Well to Well Corelation


Real Time 6” Density Image Interpretation for

Geosteering

Difficult geosteering environment with a lack of obvious geologic

markers


Real Time Density Image Interpretation for

Geosteering

Cross section illustrating bedding planes parallel to the borehole

trajectory


Density vs Gamma Ray Memory Image

Despite a homogeneous reservoir, a density variation does exist

allowing for some structural interpretation


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.


Borehole Quality Plot


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

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