--> Abstract: Fracture Modelling in a Double Porosity Volcaniclastic Reservoir: A Case Study of the Precuyo Group in Cupen Mahuida Field, Ne; #90063 (2007)

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Fracture Modelling in a Double Porosity Volcaniclastic Reservoir: A Case Study of the Precuyo Group in Cupen Mahuida Field, Neuquen, Argentina

 

Zubiri, Martin1, Jose Silvestro1 (1) Repsol YPF, Neuquen, Argentina

 

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