Geological Environment and Oil Systems Characterized by X Ray Fluorescence Tool

Schiuma, Mario F.¹ and Larriestra, Claudio N.
¹[email protected]

The aim of this paper is to show the application of x ray fluorescence tool to adjust geological correlations, to recognize depositional environments and by using the anomalies in the amount of metal and metalloids characterize the oil system.

Crossing chemical elements abundance with the rock composition it is possible to generate models that reflect the relative abundance of certain elements associated to rock types and depositional environment. It is possible using the statistical distribution of key elements to distinguish rock types and depositional environment using a geochemical signature of them. Interesting results were obtained in a field in the Golfo def San Jorge basin. It was possible to generate a geochemical model for each formation, and also to know the relationship between shales, tuffs and the cleaner sands (containing less tuffs).

Good results were obtained also in Cañadón Asfalto basin using this method by combining data collected in Cuttings, cores and outcrop samples, was possible to establish the geochemical signature of the formations present in the area and establish which wells and outcrops were more closely related.

On top of that, in measurements made in different basins of Argentina was found that the source rock of continental origin had anomalies of sulfur, arsenic, molybdenum and lead, associated with the facies richer in organic matter. While on a marine origin source rock anomalies of vanadium, chromium, nickel and molybdenum were found. Also the rocks filled by oil are characterized by anomalies of the same elements of those source rocks related with them.

The presence of metals is closely related to the genesis of the source rocks and in consequence with the oils that they have generated. Different origins are mentioned for the presence of these metals. One of them are the metalloporphyrins that have their origin in the plants chlorophyll. Another source are the humic substances that have the capacity to capture environmental metals and may have been kerogen precursors. The third possible source is that metals are present in the source rock and finally is mentioned that could be loaded by formation water.

Concluding with this method it is possible to obtain chemostratigraphic models and use it to adjust the geological correlation. Also the presence of metals associated with source rocks and oils can be a key to knowing the distribution of generating facies and the petroleum reservoirs.

AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013