Use of
High-Resolution Core Description Data to Risk Net Pay from Log-Based
Petrofacies for Thinly-Bedded Deepwater Channel Complexes,
Lukas, Theodore C.1, Peter
Schwans2 (1) Consultant, Houston, TX (2) Devon Energy Company,
Log-based facies or petrofacies contain
thin-beds at or below log-resolution. Individual beds range from 2 - 0.01 feet.
As a result of thickness variations and stacking densities, estimates of thin
bed net pay are associated with significant uncertainty. Cores from Zafiro
Field, Equatorial New Guinea, were used to define thin bed types and the ranges
of uncertainties associated with the beds identified via logs and cores.
The Zafiro Field of Equatorial Guinea
comprises a series of stacked channel complexes of Miocene-Pliocene age
deposited in the mid to lower slope position of the Niger Delta. Thin bed
environments in channel complexes include crevasse splays, avulsion related
lobes, lobes associated with overbank channels, levees, and indeterminate
remnants of near-channel overbank. High-resolution core description data (100 samples/ft) from proximal to distal overbank deposits
were compared to log-based petrofacies computations. Data from the two methods
were compared as a function of hydrocarbon saturation, bed thickness,
lithology, and grain size and used to condition the computations. This was
compared to the pay computed and predicted from the petrofacies probability
curves. A set of confidence levels are applied to a range of So
cutoffs to better define the uncertainty range. The described approach allows
better benchmarking and risking of log-based thinbed calculations and can be
used in geostatic models.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California