Integration of 3D Migration Modelling and Seismic Facies Analysis – Danish North Sea

M. Hertle¹, M. De Lind Van Wijngaarden², A. Kauerauf², A.G. Schmidt¹, D. Schwarzer¹, R.O. Thomsen¹, and A. Uldall^1
1Maersk Oil and Gas, Copenhagen, Denmark
²IES GmbH, Aachen, Germany

Petroleum systems modelling technology has advanced significantly in the recent years. Although the simulators have become more sophisticated, allowing for various hydrocarbon migration options (flow path, darcy, hybrid, invasion percolation) and the integration of advanced PVT calculation of the hydrocarbon phases, one of the critical issues in modelling is the actual model building itself, especially regarding the facies (lithology) distribution. Usually most of the detailed information from the seismic interpretation is lost during the model building process. Furthermore cell based Darcy simulators have limitations in the amount of cells they can calculate, which again results in rather coarse petroleum systems models.

The seismic data can provide high resolution lithological and petrophysical details. Relative clay and sand contents of clastic rocks can be obtained from seismic attribute analysis, together with suitable log data, and converted into the corresponding fine scale facies cube. In principle, there are two methods to obtain the high resolution migration properties: A) lithology impedance (clay content and porosity) based on seismic attribute analysis converted to permeabilities and capillary entry pressures, and B) Statistical distribution of low resolution (default lithologies) based on the seismic fabrics.

The finer scale rock properties can then be used in a local grid refinement approach. Compaction, temperature, pressure, hydrocarbon generation and expulsion are being calculated on a coarse grid, while hydrocarbon migration is being calculated on a high resolution grid in relevant areas (carrier, reservoir).

We will present the applied workflow and the resulting best practices. In addition, different migration methods such as invasion percolation, flow path and hybrid modeling will be compared.

These results are also compared and integrated with a chimney cube over the same area of interest. A 3D chimney cube is produced using an assemblage of directive, multi-trace seismic attributes, neural network technology. Structures in the seismic that are probable fluid migration paths are enhanced selectively while other features are muted. This technology provides additional input and calibration for the 3D petroleum systems model.

A petroleum system study with focus on hydrocarbon generation and migration in the Middle Jurassic in the Danish sector of the North Sea is used to illustrate workflow and methodology.

 

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