--> Reservoir Modeling and Provenance Analyses of the Campanian M1 Sandstone, Eastern Ecuador

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Reservoir Modeling and Provenance Analyses of the Campanian M1 Sandstone, Eastern Ecuador

Abstract

The Campanian M1 Sandstone of the Napo Formation is one of the main reservoirs of the Oriente Basin of eastern Ecuador, with reserves estimated at nearly one billion barrels. However, in some oil fields it presents strong variations in permeability and porosity, affecting the oil production. The reservoir characterization of the M1 Sandstone is based on an integrated study, which includes core description, electric log analyses and seismic interpretation. Location of the source area of sediment was determined by provenance analysis, including LA-ICPMS U-Pb detrital zircon dating. The model defines the geometries of the M1 Sandstone and describes the lateral and vertical heterogeneities, helping to reduce the risk during well planning and drilling engineering. Sedimentological core descriptions show that M1 Sandstone records a heterogeneous shallowing-upward succession, prograding from prodelta turbidites to delta-front mouth bars. The succession reflects deltaic progradation rather than the backstepping pattern typically displayed by transgressive deposits from the underlying Albian to Santonian sandstones of the Napo Formation. Seismic attributes were performed to define the geometry of the sands; RMS amplitude shows clinoform geometries with sigmoidal sand bodies prograding from northeast to southwest. This is consistent with thickness maps of the M1 Sandstone, which present lobate shapes that thin rapidly southwestwards. Radiometric dating was performed on detrital zircons recovered from the reservoir sands of the delta front. The U-Pb detrital ages cluster in a population that ranges from 1.4 to 1.6 billion years. These ages indicate that sands of the M1 Member were derived from the erosion of the lithotectonic Rio Negro-Juruena province, located to the northeast of the studied area. The time of delta progradation coincides with the start of the Andean orogeny, and may correlate with the collision of fragments of the Caribbean Plateau against the continental margin of northwestern South America. The importance of defining a delta system for the M1 reservoir is that this type of reservoir is among the world largest in areal extent. The potential for stratigraphic traps within deltaic systems is very high, due to the compartmentalization of the individual sandstone clinoforms. Reservoir modeling combined with provenance analyses allowed to define the geometries and lateral continuity of the reservoir, but also to understand large-scale basin processes.