Rossetti, Enio Luiz - Petrobras/E&P
A new developed methodology aimed to help the integration of geological and geophysical data sets was tested in some Brazilian sedimentary basins. Conventional seismic data, either 2D and 3D, after digital imaging processing, has the potential to reveal subtle aspects of the seismic data, not readily available on conventional plots and on-screen seismic displays. The methodology uses PC-based commercial digital-imaging software, like Photopaint®, to unravel seismic stratigraphic features hidden in high resolution seismic data.
The research strategy was to process the seismic data as pixel-based, grayscale images instead of a set of digital, trace-organized seismic samples. Disguised by the gray shades of on-screen displays are hidden information that represents geological complexities regarding the stratigraphic architecture, like subtle stratal truncations, prograding clinoform geometry, channels, turbidites, unconformities, or downlap surfaces that may help to correlate 4th or even 5th order stratigraphic sequences, or to infer lithologic variations and depositional environments.
By enhancing the contrast, and after the application of some filters in seismic images from conventional 10-60 Hz seismic data, it was possible to discriminate seismic stratigraphic details such as prograding clinoforms, unconformities and channels that help to define 4th order stratigraphic sequences in the Neocomian rift sequence of the Apodi Graben.
Fig. 01 shows a zoomed portion of a 3D seismic line from the Apodi Graben. Fig. 1a is a variable-density standard image, after digital imaging processing, like contrast, brightness and intensity. The final effect is a better image of the seismic data. Fig. 1b shows another version of the same data, after the application of a contour filter, resulting in a less diffused presentation of the image. Fig. 2a shows a line-drawing version of the same data set (dashed lines). This drawing plot has been superimposed over original plots (Fig. 2b) which indicates that this methodology does not create anything new on the original data, since that the drawn lines involve perfectly the original seismic reflectors.
This methodology may be applied to reservoir analyses as well as to exploratory purposes, extracting potentially hidden information of most of conventional seismic data.
AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil