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Architectural reinterpretation and acoustic facies of the lower portion of the Apiúna unit (Cambrian deep-water depositional system, Santa Catarina State, Brazil)

2004; Sociedade Brasileira de Geologia; Volume: 34; Issue: 3 Linguagem: Inglês

10.25249/0375-7536.2004343335346

2177-4382

Giorgio Basílici, Jorge Leonardo Martins,

Hydrocarbon exploration and reservoir analysis

An architectural model of an ancient sand-rich and mixed mud-sand ramp deep-water sedimentary environment, outcropping near Apiúna, Santa Catarina State, Brazil, is presented. This research contributes in the following way to the exploration sector of the petroleum industry: i) with a conceptual model of reservoirs in ramp deep-water systems and ii) with synthetic seismograms, based on the outcrops. Two types of ramp are recognized. One type, sand-rich, is characterized by extensive sandy-sheet reservoirs, not linked to proximal channels and showing an apparent casualness of construction. The mechanisms that generated the sandy-sheets were bipartite: a granular flows (debris flows s.l.), in the lower part, and a turbulent flow (turbidity currents), in the upper part. The different velocity and efficiency of the two flows produced a distinct lithological and architectural distribution of the resultant deposits: medium grain size, amalgamated and thick sandstone in the proximal part: fine - very fine grain size and thin sandstone in the distal part. (2) The second type, mixed sand-mud, is characterized by a channel-levee complex and overbank deposits. The two ramp systems represent a vertical variation of the depositional environment, controlled probably by tectonic-morphologic factors. Linked to the architectural model we produced synthetic. seismograms. The properties needed for constructing the synthetic seismograms (densities and P-wave velocities) are evaluated from theoretical petrophysical tables. The synthetic seismograms allow defining a seismic forward model and characterizing the acoustic facies of ramp systems.