Biodegradation in Numerical Basin Modelling: A Case Study from the Gifhorn Trough, N-Germany

I.O. Blumenstein¹, B.M. Krooss¹, R. di Primio², W. Rottke³, E. Müller^4,a, C. Westerlage⁴, and R. Littke^1,*
1Institute of Geology and Geochemistry of Petroleum and Coal, RWTH Aachen University, Lochnerstr. 4-20, 52056 Aachen, Germany
²GFZ Potsdam, Telegrafenberg, 14437 Potsdam, Germany
³IES GmbH, Ritterstr. 23, 52072 Aachen, Germany
⁴RWE Dea, Überseering 40, 22297 Hamburg, Germany
apresent address: Hydro Oil & Energy, Global Exploration, 0246 Oslo, Norway
*[email protected], Tel.: +49 241 80 95748, Fax: +49 241 80 92152

A mass balance concept based on a petroleum compositional description using 14 individual compound groups has been developed to reproduce the process of in-reservoir petroleum biodegradation. Individual compound groups have been attributed different "biodegradablilities" and biodegradation rates to account for observed differences in their susceptibility to biodegradation. Petroleum compositional information is derived from basin modelling, in addition to temperature histories, filling rates and volumetric information. This new method has been subsequently applied to model the biodegradation processes in a petroleum system in the North German Basin. The case study area is situated in the Gifhorn Trough, where Jurassic reservoirs contain oils of variable API gravity (24° to 33°), although present depth and temperature are similar. Numerical modelling revealed, however, that the filling histories of the individual reservoir structures differ considerably. Neither the Biodegradation Index (BDI) approach by Yu et al. (2002) nor an improved version (BDIpro) by Wilhelms et al. (2004) reproduced the different biodegradation levels in the two investigated fields. Taking into account filling and temperature history of the reservoir structures the newly developed "Biodexx" algorithm predicted compositional data and API gravities similar to those observed in the study area.

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands