--> Direct Hydrocarbon Assessment in the Santos Basin by the Integration of Oil Slicks, Piston Core and Gas Chimneys, Schmitt, Priscila; Mello, Marcio; Bender, Andre A.; Elias, Vladimir; Brooks, Paul J., #90100 (2009)

Datapages, Inc.Print this page

Direct Hydrocarbon Assessment in the Santos Basin by the Integration of Oil Slicks, Piston Core and Gas Chimneys

Schmitt, Priscila1
 Mello, Marcio1
 Bender, Andre A.1
 Elias, Vladimir1
 Brooks, Paul J.1

1HRT & petroleum, Rio de Janeiro, Brazil.

Until four years ago, most of the exploration activity in the
Santos basin was in shallow waters, but recent giant hydrocarbon discoveries, in the pre-salt sequences, in deep and ultra-deep water areas of Santos basin prove to be the most important area for new reserves in the Brazilian coast. The thick evaporitic layer is an important seal for the new giant hydrocarbon discoveries in the sub-salt sequences, but the detection of oil slicks in the same area reveals a more complex and variable sealing system. Natural oil seeps and oil slicks and oil presence in piston core samples indicate petroleum actively migrating upward to the sea floor. Detection of offshore seepages can be detected by satellite radar technique (SAR) that evaluate the smoothing effect of natural oil slicks on the sea surface. Owing to the fact this technique is only a snapshot of the present day seepage, multiple images covering different times are required to increase the chance of observing a seep, which often occur episodically. An effective way to investigate seeps is coupling the satellite images with piston core, in which the locations are selected from seismic data interpretations, and with gas-chimneys detection technique. The standard seismic response in chimneys is chaotic, with low energies and low trace-to- trace similarity. Several seismic attributes in these chaotic zones, such as similarity, curvature, energy and dip variance, allow the detection of hydrocarbons pathways. The technique is not completely automatic since it needs to be assisted by a seismic interpreter to indicate the unfaulted background seismic characteristics. These way neural network algorithms are able to select the best faulted / fractured areas permeated by hydrocarbons. In many locations the gas chimneys coincide with upward migrating oil slicks. Other result of this work, based on Radarsat-1 images, is distribution of 39 major oil slicks in the offshore Santos Basin area, in water depth areas ranging from 400m to 3,000m covering 700 km2. The piston core sampling sites were selected using 3D geophysical data integrated with geological information. The 25 piston cores were analyzed by geochemical and diamondoids analyses and the results were compared to regionally-produced oils from the Santos Basin. They were identified as mixed oils belonging to at least two different petroleum systems: a marine siliciclastic- carbonate type and a lacustrine saline type.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil