Print this pageAAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Stratigraphy and Depositional History of the First Eocene Reservoir from Wafra Field, Partitioned Neutral Zone (PNZ), Saudi Arabia and Kuwait
(1) Chevron, Houston, TX.
The Paleocene/Eocene aged First Eocene reservoir at Wafra Field in the PNZ (Saudi Arabia and Kuwait) is a dolomitized, heavy oil (18-22°API) carbonate reservoir. The 40 acre Large Scale Pilot (LSP) is located in the southern portion of the field and contains 56 producers, injectors, and temperature observation wells. Additionally, four cores were taken from the LSP area. The high well density and variety of data types (Core, FMI, wireline logs) provides a unique opportunity to examine the stratigraphy and depositional history of this complex carbonate system. This study focuses on the EOC500 to EOC700 interval, which is the zone targeted for initial enhanced oil recovery.
The carbonates of the First Eocene were deposited in shallow subtidal to supratidal environments on a low to moderate energy inner shelf or ramp. Based on core observations, facies are dominantly dolomitized peloidal wackestone to packstone, dolomitized algal wackestone, dolomitized mudstone, and carbonate mudstone. Based on a combination of core, wireline (especially gamma ray), at least 11 shallowing upward cycles were identified in the study interval and correlated across the LSP area. A typical cycle consists of subtidal dolomitized peloidal wacke/packstone overlain by algal wackestone or mudstone. These shallowing upward cycles form the basis of paloegeographic maps which when combined with modern analogs can be used to estimate facies distribution across the LSP area. Detailed paleogeogaphic maps and 3-D models can also be used to help understand the impact of stratigraphy and paleo-topography on production. In this case, it appears that higher production occurs closer to subtidal/intertidal facies and lower production occurs in wells located closer to supratidal facies.