Dull, Dennis W.¹
(1) ChevronTexaco, Bellaire, TX

ABSTRACT: Similar Workflow, Unique Solutions – Integrating the Cores and Well Logs in Constructing the Sequence Stratigraphic Framework of Three Carbonate Reservoirs at Wafra Field

Wafra field is located in the Partitioned Neutral Zone between Kuwait and Saudi Arabia. The field has produced over 1 billion barrels of oil from 5 reservoir intervals. Earth models were constructed for fluid flow simulation to evaluate the potential of three, shallow heavy oil, dolomite reservoirs: First Eocene, Second Eocene, and Maastrichtian.
The construction of the sequence stratigraphic framework involved a similar workflow for all three reservoirs. The workflow consisted of : (1) establishing the depositional setting, (2) constructing the sequence stratigraphic framework by defining the cycle, cycle set, high frequency sequences, maximum flooding surfaces, and system tracts using the core, (3) transferring lithofacies and stratigraphic picks of the cores to well logs.
The uniqueness arises in integrating the sequence stratigraphic framework with the well logs. Even though all three reservoirs were deposited on a restricted shallow ramp or shelf setting correlation using well logs is difficult because of the influence of paleotopography, no highly contrasting lithology (almost all dolomite) except for the lower part of the Maastrichtian which is limestone, and porosity between reservoir and non-reservoir is not solely definitive.
Constructing the 3D sequence stratigraphic framework for each reservoir entailed a different approach to integrate the interpretation to the non-cored wells. The sequence stratigraphic focus is important for use in determining which stratigraphic surfaces are important for fluid flow simulation and correlate these throughout the entire reservoir. The First Eocene and Second Eocene reservoirs have been through fluid flow simulation and have been successfully history matched.
In all three cases the sequence stratigraphic framework established from the core has been instrumental in identifying barriers and baffles to flow, oil-water relationships, and development potential, a combined 30 billion barrels of oil-in-place.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.