A procedure for identifying and characterizing petrophysical flow units helps resolve some of the key challenges faced in exploration for and production of carbonate reservoirs. The application of this model reveals that one key to understanding and predicting the performance of carbonate reservoirs is to represent them as combinations of different flow units, each with uniform pore-throat size distribution and similar performance. If a relationship exists between depositional facies and flow units, one can develop a common geological and engineering zonation. Parasequences can then be characterized in terms of petrophysical flow unit types. Combining the water saturation, hydrocarbon column height, and relationships of these flow units with the interpreted sequence stratigraphy of the area provides a useful tool for mapping reservoir performance cells to predict the location of stratigraphic traps. This approach can also be useful in managing producing reservoirs to develop bypassed pay and to establish presimulation performance predictions.

To illustrate this method, we use five examples: a Middle East limestone, where the model is used to identify reservoir zones with significantly different performance that are less evident from log porosity alone; the Madison carbonate of the Williston basin,

©Copyright 1997. The American Association of Petroleum Geologists. All rights reserved.

¹Manuscript received March 23, 1995; revised manuscript received July 7, 1996; final acceptance November 11, 1996.

²Conoco Inc., P.O. Box 2197, Houston, Texas 77252.

³DJH Energy Consulting, P.O. Box 271, Fredericksburg, Texas 78624.

Thanks to Conoco Inc. for allowing publication of these examples and to all who have contributed to them. A special thanks goes to the following helpful people: Stanley Bohon, Donna Harwell, and Ginnie Murphy for providing graphics support; Dena Wagner for numerous database logistics; Sheri Gretschel and Chi Chi Coleman for typing help; Rob Pascoe for Middle East sequence stratigraphy; Tom Anderson for his historical perspective on Little Knife's discovery and appraisal; Charles Ways for guidance on the San Andres; Bill Hardie for the opportunity to work on Dagger Draw and for his technical input on the reservoir geology; André Bouchard for all of his advice on capillary pressure; Ray Mitchell for allowing us to include the B.F. 12 core description; Randy Mitchell for his talent of combining personnel; and Tim Borbas for championing the assimilation of our model to Tertiary clastics applications in the Gulf of Mexico.