Wafra First Eocene Reservoir Characterization Study to Assess Water Encroachment and Remaining Resource Potential, Partitioned Neutral Zone, Saudi Arabia and Kuwait

Kera Gautreau, W. Scott Meddaugh, Jim McAuliffe, Stewart Griest, and Niall Toomey
Energy Technology Company, Chevron, Houston, TX

A multi-disciplinary approach to reservoir characterization of the Wafra First Eocene reservoir was used to assess the distribution of water and the remaining resource potential throughout the reservoir, particularly as related to implementation of a steamflood. Previous studies, which have relied largely on static data, were not able to quantitatively predict water cut and water saturation trends within the reservoir.

Characterization of remaining resource utilizes a workflow in which full-field saturation maps representing reservoir conditions at the end of the current year are generated using production attribute mapping techniques. These saturation maps are then combined with the original porosity-thickness (PhiH) maps to produce remaining hydrocarbon pore volume (HCPV) maps for the end of the current year. ROIP can be estimated from the HCPV maps. The predictions made from production mapping are compared to OOIP estimates and results of layer average Sw for newly drilled steamflood pilot wells.

Water encroachment assessment is more complex due to the long production history, large number of wells, and “dump flooding” from a shallower zone in which formation waters of variable salinity were introduced into portions of the producing reservoir. An integrated workflow was developed to assess the potential water encroachment throughout the reservoir. This workflow includes: (1) an investigation of water cut through time using the earliest producing wells in order to identify trends of high water cut; (2), use of static and dynamic data to map the variability in thickness of the transition zone; and, (3) a map-based workflow that tracks the temporal and spatial changes in produced water salinity, in combination with layer average reservoir property maps, to quantitatively identify the areas of the reservoir where “dump flooding” has occurred.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas