Outcrops and Subsurface: An Example of Geologic and Seismic Modeling of the La Jardinera Turbidites, Neuquén Basin - Argentina

Faccion, Jose E.¹; Silveira, Ariane ²; Moriss, Mathieu ³; Carbone, Osvaldo ⁶; Leanza, Hector ⁴; Paim, Paulo ²; Andrade-Ramos, Antonio ¹; D'Ávila, Roberto ⁵; Santos, Saulo ⁵
(1)Research Center - PDEXP, PETROBRAS, Rio de Janeiro, Brazil. (2) Geociências, UNISINOS, São Leopoldo, Brazil. (3) PARADIGM, Rio de Janeiro, Brazil. (4) Facultad de Ciencias Naturales, Univ Nacional de La Plata, La Plata, Argentina. (5) E&P-EXP, PETROBRAS, Rio de Janeiro, Brazil. (6) EPRO/EXPL, PETROBRAS ARGENTINA, Neuquén, Argentina.

Outcrop analogues can be converted into three-dimensional numerical models by a proper combination of geologic modeling and synthetic seismic modeling. These models are usefull quantitative tools for the comparison between surface and subsurface models.

The studied area is located near the southernmost border of the Neuquén Basin, Argentina; sedimentation spans from the Pliensbachian to the Early Callovian (Leanza, 1992). A thick marine succession of deep-marine strata was deposited in the region succeeded by shallow-marine facies. They are unconformably overlain by continental facies. From base to top, eight depositional sequences were identified. The first two depositional sequences are bounded by a major unconformity surface that delineates the abrupt deposition of a relatively thick (up to 400 m.), sandy turbiditic succession (Gulisano & Pleimling, 1995) over fine-grained, deep-water deposits as a result of gravity flows (Paim et al, 2008).

Geologic profiles were surveyed using the classic approach of facies, facies associations and depositional environments; all information was referred to a stratigraphic datum and loaded into appropriate software for stratigraphic correlation and interpretation. Sequence boundaries and other related features were interpreted. Geologic/geometric objects and facies distribution within them were refined by geostatistics for each sequence. The resultant geologic model was converted into a synthetic seismic cube using Wicker-type wavelets.

The oldest sequence, Mo10, corresponds to the initial transgressive phase of the basin, characterized by facies associations of basin floor shales alternated by some thin layers of fine grained sandstones interpreted as lobe fringe facies. The seismic synthetic model exhibits a low amplitude set of parallel layers. The Mo20 sequence contains an association of lobe fringes and distal lobes and its model shows a set of parallel to sub-parallel thin horizons. The Mo30 sequence represents a set of medium to coarse grained sandy lobes and associated interlobes; the synthetic model shows a set of sub-parallel horizons and some characteristic cut-and-fill structures due to scarce channels. Finally, Mo40 sequence exhibits facies and geometries interpreted as channel-fill deposits and associated lobes and interlobes; the equivalent modelled seismic image corresponds to a set of high amplitude sub-parallel layers interrupted by the cut-and-fill pattern of the channels.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.