--> Abstract: Source Rock Prediction from Seismic Part II: Identifying and Mapping Source Rocks Claystones on Seismic Data, by Helge Løseth, Lars Wensaas, Marita Gading, and Kenneth Duffaut; #90124 (2011)

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AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Source Rock Prediction from Seismic Part II: Identifying and Mapping Source Rocks Claystones on Seismic Data

Helge Løseth1; Lars Wensaas1; Marita Gading1; Kenneth Duffaut1

(1) Statoil ASA, Trondheim, Norway.

The ability to identify a source rock in the subsurface and quantify its parameters has a significant impact on prospect risking assessment of a petroleum play. Traditionally, the risking is based on geochemical analyses of hydrocarbons or source rock samples. Here, we present for the firs time a new way of identifying, characterizing and mapping spatial distributions and variations of thick source rocks based on seismic data. The method has been used with success over a number of years.

We have established a relationship between rock properties of organic rich claystones and acoustic parameters. Low densities, low velocities and strong anisotropy give the top and the base of organic-rich claystone layers a characteristic seismic expression. Consequently, the presence, thickness and basin wide spatial distribution of a source rock can be mapped based on seismic data. We demonstrate how the source rock can be mapped out basin-wide (screening phase) and how thickness of the source rock layer can be identified and mapped in more detail. Not only the amount of total organic carbon, but also its vertical stacked distribution, a parameter we term the ‘organic profile’, influences the seismic expression of the organic rich claystones. Seismic expressions of typical organic profiles will be presented.

We conclude that the new results presented here will change the way basin analysis is done because the source rock, which is the first and foremost element of the geological system required to produce a petroleum play, now can be mapped based on seismic data only.