Page 225 - The Geological Interpretation of Well Logs

- IMAGE LOGS -

N E

}
E.G || ue
|

28.15 | WES
t ia
| at
| |
Soo |f 2
| Lf-
| ya \
=
99.2 || _ 4 = 5
~
| rs <

9.4 L F = 8
ee
™
22:6:|| ‘ee —S
4
| | ee
| fh
92.8 ek —
: LITHOLOGY

HL | er
=
- iene
©
3
— MARL
O02 i Z zi
a
Figure 13.23 Electrical image of a slump fold in marls. The fold is recumbent and
rests on beds with very low dips. The Jaminae above the fold also have a very low
dip suggesting infilling cover (high resistivity is dark, Schlumberger FMI tool).

13.6 Quantitative uses of thickness is apparently exaggerated (Pezard er al., 1992).
electrical images However, this evaluation is simply in terms of sand/shale
and similar to the standard thin bed analysis using
Much of the interpretation on image logs is qualitative. dipmeter curves (Anxionnaz ef a/., 1990}. It is a one
But there is a need and the possibility for quantitative dimensional analysis albeit at a scate finer than for the
methods (Serra et ai., 1993; Sullivan and Schepe], 1995). standard logs and images lend themse!ves to two dimen-
The quantitative analysis of images should use the two sional analysis.
dimesional aspects of the logs and not simply be modifi-
cations of the one dimensional, standard log analysis. — porosity and permeability
Some of the more interesting methods proposed so far A quantitative, two dimensional approach is used by
with some rather limited examples are given below. Schlumberger in the analysis of carbonate textures
(Dethomme, 1992). Carbonate textures lend themselves
— bed thickness to electrical image analysis because pores and vugs can
Electrical images can be used to quantify thin beds be large and have large electrical contrast to the matrix.
(Trouiller et a/., 1989). The fine resolution of the electri- The method proposed by Schlumberger is based on an
cal images (see resolution) allows beds down to at least analysis of the images themselves, either leading to new
5cm (2") to be accurately evaluated. Beds down to 1.0m images of selected features or new summary data.
(0.4") can be detected but from about 2.5 cm (1”), bed

215