High Resolution Geo-Cellular Modeling of the Upper Morrow “a” Sands from Postle Field, Texas County, Oklahoma

Jobe, Tiffany D.¹; Wiley, Mark ²; Heris, Ayyoub E.^3
1 Department of Geology, Colorado School of Mines, Golden, CO.
² Department of Geophysics, Colorado School of Mines, Golden, CO.
³ Department of Petroleum Engineering, Colorado School of Mines, Golden, CO.

Postle Field, Texas County, OK produces from the Upper Morrow “A” sands and has over 300 million barrels of original oil in place. Today only 40% of the OOIP has been produced. The relatively poor recovery on waterflood and CO2 miscible flooding over part of the field is due to the extreme heterogeneity in the field.

It is often very difficult to create realistic geo-cellular models in complex reservoirs because of issues with data resolution, upscaling computation time. At Postle Field maintaining the lateral and vertical heterogeneity is particularly important and therefore a high resolution geo-cellular model which incorporated cores and vertical proportion curves for vertical resolution and seismic data for lateral resolution was created.

The study area within Postle Field is the Hovey Morrow Unit over which a 6.25 square mile multi-component 3-D seismic survey was shot in March of 2008. The area includes 63 wells from which log data were available as well as 4 cored wells. Detailed core descriptions and facies determinations as well as well-log correlations were integrated with seismic interpretation for modeling. The model was created using a very fine grid, with vertical cell dimensions of 2 feet.

Smaller cell size has reduced the amount of data that must be averaged within each cell. Also, integration of different scales of data, such as core and seismic data has proved to maintain the vertical and lateral heterogeneity seen in the field, yielding a more accurate distribution of facies and reservoir properties throughout the model. This resulted in better matches as the model was upscaled and history matched.

Starting with the finer grid allowed for more appropriate and realistic population of facies and reservoir properties throughout the model, and helped to maintain some of the higher resolution features during the upscaling process. This type of approach is critical for better fluid flow simulation and will lead to increased recovery and efficiency within the field.

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009