GEOMECHANICS OF THE SOUTH FURIOUS FIELD - AN INTEGRATED APPROACH TOWARDS SOLVING COMPLEX STRUCTURAL GEOLOGICAL PROBLEMS, INCLUDING ANALOG AND FINITE-ELEMENT MODELING
Da. Nieuwland et Jv. Walters, GEOMECHANICS OF THE SOUTH FURIOUS FIELD - AN INTEGRATED APPROACH TOWARDS SOLVING COMPLEX STRUCTURAL GEOLOGICAL PROBLEMS, INCLUDING ANALOG AND FINITE-ELEMENT MODELING, Tectonophysics, 226(1-4), 1993, pp. 143-166
The South Furious oil field, offshore Sabah (Malaisia), is an asymmetr
ic anticline bounded on the steep southern flank by a series of steep
E-W-striking reverse faults and affected by intense E-W crestal normal
faulting immediately next to and contemporaneous with the reverse fau
lts. In spite of the very good sand development and a high sand percen
tage, the reservoir performance is very poor. A study was undertaken t
o describe and understand the development and the mechanics of this ty
pe of structure and to explain their presence in almost undisturbed se
diments around them. The regional tectonic development was studied to
provide a basis for a geological model of the structure. A structural
geological model was necessary to be able to predict the type of fault
s and fractures and their location in the structure. The proposed stru
ctural development was modelled with analogue sandbox experiments and
numerically simulated with a finite-element program (GEOFEP). The resu
lts indicate that basement faulting related to the closing of the Sout
h China Sea, induced differential sediment loading, triggering asymmet
ric clay diapirism in the core of the anticline. The asymmetry resulte
d in contemporaneous formation of steep reverse faults at the leading
edge of the migrating anticline and normal faults in a crestal collaps
e system. The reverse faults and associated shear fractures (as seen i
n cores) have a sealing cataclastic fabric. This explains the severe c
ompartmentalisation of the reservoir with consequently poor production
behaviour, in particular in the reverse faulted part of the field.