--> Abstract: Use of High-Resolution Core Description Data to Risk Net Pay from Log-Based Petrofacies for Thinly-Bedded Deepwater Channel Co; #90063 (2007)

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Use of High-Resolution Core Description Data to Risk Net Pay from Log-Based Petrofacies for Thinly-Bedded Deepwater Channel Complexes, Zafiro Field, Equatorial Guinea

 

Lukas, Theodore C.1, Peter Schwans2 (1) Consultant, Houston, TX (2) Devon Energy Company, Houston, TX

 

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