Cerro Fortunoso Field: Static and Dynamic Modelling of a Complex Faulted and Thrusted Reservoir (Malargue Fold and Thrust Belt, Argentina)

Vocaturo, Griselda N.¹; Consoli, Vanesa; Garriz, Abel; Giampaoli, Pablo; Manestar, Gaston; Thompson, Anthony; and Massaferro, Jose Luis
¹[email protected]

The Cerro Fortunoso field is an east-verging anticline located in the Malargue fold and thrust belt (central-west Argentina). The anticline geometry varies along strike, affected by low and high angle east-verging inverse faults generating a sub-vertical flank (up to 80°) dissected by igneous intrusions. The reservoir consists of 500m thick Upper Cretaceous siliciclastic continental sediments (Neuquén group). This includes prograding alluvial fan deposits (Rio Limay Formation) and aggrading-prograding channel and flood-plain deposits (Rio Neuquén and Rio Colorado Formations) separated by a 1st order maximum flooding surface. Stratigraphically these units could be separated into higher order cycles correlatable across the field. A 3D static model representing the structural complexity and the high order cycle correlation was needed to justify the expansion of the current 15 well secondary recovery pilot to a 200 well full field development. RFT data demonstrated that flow in the reservoir was controlled by multiple thin sandstones (~ 2m) that are isolated from each other. To determine the secondary recovery potential of the field it was critical to understand the areal extent and connectivity of these highly heterogeneous bodies. This was challenging as these sandstones, due to their heterogeneity, do not show consistent log responses between wells. Additionally the very high angle of dip meant that a sandstone body could plausibly connect with a number of different sandstones on a neighboring well. To determine which ones correlated to each other, multiple correlation scenarios were constructed and subsequently evaluated by dynamic testing against production and pressure data. To capture the vertical distribution of the sandstones, modelling had to be completed on a fine scale in a reservoir with a thickness of 500 meters; therefore cell size needed to be optimized and sector models used to ensure realistic simulation times.

The geological understanding developed showed that sandstone throughout the field had similar connectivity and petrophysical characteristics to those in the waterflood pilot area. It was also seen that if the sandstones were to be more discontinuous or to have a lower net-to-gross than modeled (potential risks to waterflooding), historical production could not be matched in dynamic simulation. This methodology has demonstrated the potential to recover significant incremental hydrocarbons by waterflooding the whole field.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013