Seismic-geometric facies model of lacustrine carbonates of Morro do Chaves Formation, Sergipe-Alagoas Basin

Abstract

Recent hydrocarbon discoveries in lacustrine car-bonate reservoirs of the Campos Basin pre-salt section have motivated geophysicists and geologists to make more detailed studies of the relationship of geometric and faciological variations of similar outcrop rocks with conventional seismic data. The Seismic-Geometric Facies Model of the Pedreira Atol relates the facies association of the coquinas outcrops of the Morro do Chaves Formation, Sergipe-Alagoas Basin, to the seismic facies of a high-resolution seismic section (outthrust-1) from the same outcrop
This model was based on the interaction of three models: the Integration Facies Model; Stratigraphic-Structural Facies Model and Velocity Facies Model. The first relates the gamma-rays, sonic velocity, porosity and geometry information with the kinds of facies associations. The second is the result of the integration of the first model with the outcrop 3-D Laser-scanner topographic image and the structural-geometric observations. The last is the representation of the substitution of the facies associations of the second model for their respective sonic velocities. This last model was the input parameter to the 2-D acoustic model, which produced a synthetic seismic section of the outcrop of a similar standard to the high-resolution section of outthrust-1.
The outthrust-1 high-resolution seismic section interpretation, based on the Seismic-Geometric  Facies Model, demonstrated that the facies associa-tions found in the shallow drill hole S-217 and well FU-107, both 50m from the seismic line, correlate in the same seismic-stratigraphic level. More importantly, the geometries of the seismic facies found in the stratigraphic and structural positions were consistent with those observed in the outcrop geological structural analysis. This evidence indicates that the seismic model of the coquinas outcrop, Morro do Chaves Formation, may be used as an analogue model in hydrocarbon exploration and production activities, particularly in the coquinas facies reservoirs of the Lagoa feia  Formation, Campos Basin.