Fuhrmann, Andreas¹, Rolando di Primio¹, Brian Horsfield¹
(1) GeoForschungsZentrum Potsdam, D-14473 Potsdam, Germany

ABSTRACT: Predicting Petroleum Phase and Composition in Undrilled Prospects

The prediction of reservoir fluid properties prior to drilling is one of the most important tasks for prospect risk reduction in frontier exploration areas. The newest vintage of basin modeling software allows the calculation of petroleum phase behaviour given detailed compositional kinetic models of hydrocarbon generation. Available kinetic schemes correctly predict bulk GOR, however, the analytical methods used predict much wetter gas compositions than observed in natural fluids, resulting in erroneous phase predictions. Experimental results indicate that this effect is strongly influenced by the experimental heating rate, primary cracking mechanisms and the presence or absence of catalysts in the pyrolysis experiments.
We focus on the correct determination of hydrocarbon phase properties from pyrolysis lab experiments using immature source rock samples by tuning the determined compositional data to PVT data of well documented reservoir fluid maturity sequences. We have thus developed compositional kinetic models of hydrocarbon generation for marine Type II and mixed Type II/III source rocks. The data format selected is compatible with the compositional resolution used in reservoir engineering, allowing a direct comparison of predicted compositions and phase behavior to PVT data of natural fluids. The integration of tuned compositional kinetic models and phase behaviour calculation in 2D and 3D basin models resulted in the predition of GOR, phase state, saturation pressure and composition with an error margin of 10 to 20%. The suggested approach is applicable to various source rock types and can be used for determination of hydrocarbon phase properties in undrilled prospects under various geologic conditions.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.