The Perla Gas Field, Gulf of Venezuela: Geological Model of an Oligo-Miocene Carbonate Bank
Borromeo, Ornella1; Miraglia, Salvatore; Reali, Sandro; Sartorio, Dario; Ortega, Solange; Villalobos, Rosemary; Castillo, Veronica; Esteban, Mateu; and Benkovics, Laszlo
The PERLA gas field is located offshore in the Gulf of Venezuela. The reservoir is an Oligo-Miocene carbonate bank developed upon a basement high. The integration of 3D seismic data and sedimentary analysis of two cored wells allows the definition of a working geological model and the identification of the major depositional and diagenetic controls on the reservoir quality.
The reservoir is composed of limestones, with minor sandstones and dolomitic-silty limestones in the lower part. Dominant components are branching red algae, rhodoliths and large benthic foraminifera (LBF), secondary but locally important components include finger corals, mollusks, barnacles, green algae, bryozoans and planktonic foraminifera.
Seismo-stratigraphic analysis indicates that the overall architecture of the reservoir consists of three main units, whose thickness seems locally controlled by syn-sedimentary faults. Flat to mounded geometry of internal reflectors suggests a complex facies mosaic. Possible outcrop analogues in the Mediterranean region show distally steepened ramp geometry with facies distribution controlled by physical and biological processes.
The 200-m-thick section of rhodalgal carbonates is divided into three units bounded by flooding surfaces. Facies analysis indicates an overall deepening-upward stacking pattern. Shallower middle ramp facies, composed of grainstone with LBF and red algal debris grade upward to deeper outer ramp facies dominated by rhodolith floatstone-rudstone and lastly to fine bioclastic grainstone containing planktonic foraminifera and glaucony, marking a drowning event.
The lower and intermediate units are characterized by secondary biomoldic and primary intraparticle porosity, whereas the upper unit is dominated by primary inter- and intra-particle pores. In general these deposits show moderate to high porosity and low permeability due to the small size (<50microns) of pore space.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013