Static Reservoir-Analog Modeling of Focused-Flow and Dispersed-Flow Resedimented Deepwater Carbonate Deposits: Upper Miocene, Agua Amarga Basin, Southeast Spain

The Agua Amarga basin in Southeast Spain consists of Upper Miocene interstratified Deepwater sediment gravity flow deposits and hemipelagic-pelagic deposits that overlie shallow-water ramp deposits. This study focuses on the Deepwater (few hundred meters) deposits, and documents a comprehensive outcrop-to-model workflow that included collection of field and lab data, processing and interpretation of the data, and construction of a 3-D static model in Petrel™. Of particular significance is the recognition of two distinct resedimented systems in the basin: a ‘focused-flow’ system that was controlled by the presence of a paleotopographic focusing feature, and a ‘dispersed-flow’ system that lacked sediment focusing. Aside from changes in relative sea level, the architectures of these two systems were controlled by paleotopography.

Reservoir units for both systems are composed of graded fine- to very coarse-grained skeletal packstone facies (high-density turbidites), and breccias with fine- to very coarse-grained matrices (debrites). Baffle units for both systems are composed of foraminiferal-, volcaniclastic foraminiferal-, and skeletal foraminiferal wacke-packtone facies (hemipelagic-pelagic sediments and low-density turbidites). Results of the reservoir-analog model highlight the quantitative differences between the two Deepwater systems and their controls. Focused-flow reservoir units in the basin have greater bulk volume (46.5 million m3 in focused flow and 18.6 million m3 in dispersed flow) and greater pore volume (14.6 million m3 in focused flow and 5.7 million m3 in dispersed flow) than dispersed-flow reservoir units. This difference was controlled by a number of factors, but in this case, it is predictable on the basis of linear dimension of shelf margin sourcing the focused-flow system (5 km) versus that of the dispersed-flow system (2 km). Finally, the focused-flow system has volume ratio of reservoir to baffle units of 0.7 and the dispersed-flow system has volume ratio of reservoir to baffle units of 0.1. Thus, paleotopographic focus leads to less heterogeneity.

Reservoir-analog models are important tools that can better define the input parameters in dynamic subsurface reservoir simulations. The systems documented in this study provide an important outcrop analog for assessing subsurface potential of resedimented Deepwater carbonate deposits, particularly those which may have undergone similar mechanisms of sediment focusing.
 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California