Abstract: 3-D Seismic Stratigraphic Inversion: A Tool for High-Resolution Stratigraphic Analysis and Reservoir Characterization.

Johann, Paulo - Petrobras/E&P; Frederique Fournier - lFP

A new methodology for a 3-D reservoir description is applied to a pilot area, a turbidite giant oil field in Campos basin (passive margin of eastern Brazil). This methodology requires the integration of different data types to define a more detailed and realistic interpretation of reservoir architecture. Geological knowledge, well logs and 3-D poststack seismic data were integrated in a target-oriented approach based in a seismic stratigraphic inversion (Fig. 1).

The turbidite giant oil field is located in the central part of Campos basin. The production reservoir is characterized by an important stratigraphic control. It is consists of composite turbidites sands that were deposited during the Cenomanian/Turonian and are intercaled to with marls and shales. Oil accumulation is controlled by turbidite sandstone pinchout and by structural features. The individual sands bodies are lenticular and elongated northwest-southeast coalesce to form a thick sandbody.

The methodology of 3-D seismic inversion is carried out in six main steps: a) well-to-seismic quantitative calibration; b) zero-phase deconvolution; c) structural and stratigraphic regional interpretation; d) 3-D acoustic impedance modeling; e) seismic stratigraphic inversion; f) detailed seismic stratigraphic interpretation of inversion images (acoustic impedance and reflectivity).

The well-to-seismic quantitative calibration?s purpose is to extract a target-oriented single calibration operator from well-to-seismic tie. Three main parameters are quantified and analyzed in this step: correlation coefficient, time shift and operator amplitude at each well. The second main step inversion is the deconvolution zero-phase of 3-D seismic data based in the operator defined in the first step. The third main step is carried out by a regional structural and stratigraphic seismic interpretation based on the time positions of the wells markers and 3-D seismic deconvolved data. The fourth step is built to introduce and validate the structural and stratigraphic knowledge, and provide a 3-D coherent initial acoustic impedance model. The fifth main step, the stratigraphic inversion will go to integrate and to exploit seismic amplitude variations. The sixth main step is carried out by an interpretation over the 3-D optimal acoustic impedance and over the 3-D reflections coefficients associated. This step to exploit the improve of recognizability and resolution of reflected events after stratigraphic inversion (Figures 2 and 3).

The successful application of this new methodology for 3-D reservoir architecture characterization makes it an interesting integrated seismic stratigraphic interpretation approach for other turbites fields and can be used to aid the understanding of seismic stratigraphy and sequence stratigraphy on the turbidites systems.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil