Fracture
Modelling in a Double Porosity Volcaniclastic Reservoir: A Case Study of the
Precuyo Group in Cupen Mahuida Field,
Zubiri, Martin1, Jose
Silvestro1 (1) Repsol YPF,
The synrift deposits of the Precuyo Group
in the Cupén Mahuida gas field consist of a large succession of massive and
fragmented volcanic rocks and volcaniclastic sediments of Upper Triassic to
Lower Jurassic age. Structurally the field consists of an E-W trending
anticline, vergent to the south, developed during Upper Jurassic and Lower
Cretaceous times by oblique inversion of prior half-grabens.
Build up tests define a double porosity
system reservoir, where the pore space is divided into two distinct media: the
matrix, with high storability and low permeability, and the fractures with high
permeability and low storability. Interpretation of image logs closely relates
best productive zones with open fractures.
Open fractures tend to be organized in
clusters as they show lithology dependency. Three sub-vertical systematic sets
were defined. The most dominant appear to be aligned with the present day
tectonic stress in a NW-SE direction. The other two sets (NE-SW and E-W) seem
to respond to local fracture swarms. From seismic interpretation, three sets of
faults were recognized: E-W, N20 and N120. The fractal dimension of each set
was used to model sub-seismic faults and the associated damage zones.
A discrete fracture network was
generated, where realistic simulation is constrained to match well and seismic
data. Fracture distribution allowed the definition of new deviated wells with
an azimuth of 205° and a dip of 45° to optimize fracture frecuency.
Fracture assessment opened a new insight
to well planning. As a result new structural plays are depicted, and new well
locations pointed out. Fracture density and interception probability is
estimated to optimize best production results.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California