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Meddaugh, William S.1, J. Saul Moros2, Wendell Olivier2
(1) ChevronTexaco Exploration & Production Technology Co, Bellaire, TX 
(2) ChevronTexaco Global Technology Services Company, Maracaibo, Venezuela

ABSTRACT: Stochastic Reservoir Modeling and Workflow Evaluation, C3-C4 Interval, Central Fault Block (CFB), LL-652 Reservoir, Venezuela

The LL-652 field is located in central Lake Maracaibo and produces from the Middle Eocene Misoa Formation which contain numerous transgressive-regressive sequences deposited in a shallow, tidally-dominated marine embayment with a central estuarine mud flat. The 300 m interval modeled includes only the C3 and C4 reservoirs. 
Reservoir model workflows of varying complexity were evaluated quantitatively. The fluid flow characteristics of models generated using a complex workflow based on detailed sequence stratigraphy and seven lithofacies were found to be the same as obtained from models generated using a simple stratigraphic framework and two lithofacies (reservoir, non-reservoir or RnR). For the final, full field model the RnR lithofacies were distributed using sequential indicator simulation (SIS) constrained by semivariograms and well data for 12 major stratigraphic intervals within the C3-C4 reservoir zone. Porosity was added using sequential Gaussian simulation (SGS) constrained by interval and lithofacies. Permeability and water saturation were distributed by collocated cokriging with SGS using the porosity as the secondary data constraint. 
The semivariogram models have ranges of ~1000 m and a N50E trend. The effect of semivariogram range on fluid flow characteristics was evaluated by comparing results obtained for the data-driven model with models created using ranges of +25% to –100% compared to the base case. The recovery factor for the base case was 46.2%; the recovery factors for the other cases ranged between 46.3-46.7%. These results suggest that uncertainty in the connectivity as governed by semivariogram parameters is a minor concern over the range of parameters investigated.


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