M. Gonfalini
AGIP S.p,A.
H. Anxionnaz
Schlumberger Italiana Sp.A.
ABSTRACT
Interactive Computer Aided Analysis and Interpretation of borehole images can provide a large amount of information suitable for Formation Evaluation and structural studies.
In carbonate reservoir rocks it is possible, by means of these techniques, to locate, classify and orient in the space a certain number of structural and sedimentary events such as fractures, bed boundaries, stylolites and vugs.
Orientation and dipping of fractures and bed boundaries can yield information about the present stress conditions and tectonic history of the formation and also an accurate definition of the main permeability directions, if the oriented events are related to open and hydraulically conductive fractures.
A rather complete study of such events is carried out on borehole images derived from Formation MicroScanner microconductivity mapping of three different carbonate formations.
The large number of fractures, bed boundaries and stylolites oriented using a Geological Workstation, allowed a structural interpretation based on stereonet and histogram analysis.
Since the patterns of poles of fractures on a Schmidt plot are, at least for one of the geological formations investigated, clearly lying on two conjugate great circles, whose angle is measured on the stereoplot itself, it is possible to define the field of stress orientation and part of its tectonic history.
These results are consistent with well known tectonic events recognized for the Alpine orogen, derived from surface structural and geological data.