3-D Static and Dynamic Modeling
of a Carbonate
Reservoir: The Lower Cretaceous La Tosca Unit (Huitrín Formation,
Neuquén Basin, Argentina)
The Lower Cretaceous Huitrín formation of the
Neuquén Basin (Argentina) consists of mixed clastic-carbonate-evaporite
sediments of shallow marine to continental settings. The unit is subdivided
into three lithostratigraphic members Chorreado, Troncoso and La Tosca, all of
which are hydrocarbon bearing in varying locations of the basin. This work
presents the integrated 3D static and dynamic reservoir characterization and
modeling
of La Tosca unit. The main structure in the area is an East-verging
basement anticline with ElPichanal, PataMora and PuestoMolina fields all being
located on its western flank. Both a High Resolution Sequence Stratigraphic
model and a Discrete Fracture Network model, were built through the integration
of
seismic
, core, well cuttings, borehole imaging and log data, and validated
by well tests and dynamic simulations. La Tosca depositional sequence consists
of a third order transgressive-regressive 30m-thick cycle accumulated on a
shallow carbonate platform. Main deposits comprise low- to high-energy subtidal
to intertidal facies including skeletal banks, ooid-skeletal shoals, peloidal
platform interior, algal mats and sabkha deposits. The facies stacking pattern
allows further subdivision of the unit into possible fourth and fifth order
accommodation cycles. Fourth order cycles show evident facies partitioning,
with overall argillaceous-carbonates dominating transgressive hemicycles and
clean carbonates (ranging from skeletal and oolitic grainstones to algal-mat boundstones) dominating regressive hemicycles. Fifth order cycles also show
similar facies partitioning, with transgressive hemicycles bearing argillaceous limestones and regressive cycles characterized by oomoldic and skeletal grainstones. Two types of fractures,diagenetic and tectonic, were identified,
with diagenetic fractures showing preferential occurrence within the regressive
portions of the 5th order cycles mainly in oomoldic grainstones due to enhanced
cementation and in algal mats due to desiccation. Tectonic fractures are
ubiquitous and their intensity is related to fault distance. We propose a model
of dual porosity where matrix acts as hydrocarbon storage and fractures provide
production mechanism. The best matrix reservoir intervals occur within 5th order
regressive hemicycles where permeability of oomoldic and algal mat facies is
enhanced by a network of centimeter-scale diagenetic fractures.
AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California