Orthogonal Geologic Modeling and Its Application in a Slope Channel Turbidite Environment, West Africa

Orthogonal modeling allows for the construction of a homogeneous grid where the angle between the vertices within the cell-blocks is ~ 90 degrees. The difference in our process is that we take into account the structure to build the grid employing fewer active cells than conventional orthogonal grids. This methodology preserved the same exact grid throughout the modeling process without having to generate a new grid as the project evolved and interpretations changed. The methodology also reduces the risk of numerical simulation miscalculation based on irregular cell shapes (such as triangle shapes) and is computationally less burdensome for the same given cell count as the traditional methodologies. For a complex structural and stratigraphic model, we generated a statistically significant seismic sampling into the grid and maintained the use of a very simple grid which was preserved in the simulator. The modeled scenario that we present is characterized by multiple main slope-channel, turbidite complexes that display multiple oil water contacts while remaining connected toward the crest of the structure. Detailed depositional facies domains (AXIS, OFF-AXIS, and MARGIN) were identified using seismic-attribute-grid-properties. Petrofacies, based on flow energy were also identified and distributed within each depositional domain. Selected seismic attributes allowed us to interpret the extent of depositional fairways and to use patterns as trends within the complexes for the distribution of properties. The main benefits of this process are: 1) the ability to preserve complex geology in the simulator while reducing simulator run times, 2) reduction in the use of multipliers; and 3) specifically to our case the ability to model complex geology that accounts for multiple contacts in a connected system corroborated by MDT pressure data. The goal was to develop a process by which modifications in the simulation model are made by the Reservoir Engineer and the Geologist on the static model and tested through iteration (RE-to-G&G loop) in the simulator thus maintaining geologic integrity and reducing the need for multipliers.

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California