Abstract: Modelling Diagenetic Reservoir Modifications During Basin Evolution, Off-Shore Norway

Dorothy F. Payne, Anthony J. Park, Peter Ortoleva

The diagenetic history during the basin evolution of a portion of off-shore Norway is simulated using the CIRF.B reaction-transport-mechanical modelling code, in order to predict reservoir properties. The code models basin diagenesis and fluid flow generated from chemical compaction using a fully integrated kinetic, thermodynamic, pressure solution, and fluid flow model. Using burial history, stratigraphic, structural, and lithologic data as input, the model predicts compaction rates, porosity, permeability, and fluid pressures and flow paths.

Chemical compaction is an important diagenetic process in controlling reservoir properties, particularly at depths greater than approximately 1 km in a sedimentary basin. Increasing chemical compaction causes reduction in porosity by dissolution at grain contacts and precipitation at grain free-faces. Generic simulations show that decreasing grain size and increasing lithologic stress and rate of burial result in greater chemical compaction; mineralogy has a more complex relation to chemical compaction. Grain size has the most significant effect.

Using available data, a section of off-shore Norway was modelled in order to predict reservoir properties. Porosity, permeability, and fluid pressure are calculated and compared with field data. Results show that chemical compaction affects both the magnitude and geometry of reservoir properties. Important conclusions are: (1) diagenetic modification due to chemical compaction can affect reservoir properties in predictable ways; (2) lithologic properties strongly affect chemical compaction, and thus sedimentary facies is an important consideration in basin diagenesis; and (3) CIRF.B can be used to study the evolution of sedimentary basins.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994