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The AAPG/Datapages Combined Publications Database

GCAGS Transactions


Gulf Coast Association of Geological Societies Transactions
Vol. 52 (2002), Pages 99-110

Exploration-Scale Predrill Previous HitReservoirNext Hit-Quality Prediction Strategies for Gulf of Mexico Basin Sandstones and Carbonates

Brown, Alton A.


Predrill estimates of Previous HitreservoirNext Hit quality (Previous HitporosityNext Hit, permeability, and net thickness) aid prospect risk assessment. Four approaches can be used to predict Previous HitsandstoneNext Hit and carbonate Previous HitreservoirNext Hit quality: seismic detection, analog/statistical prediction, petrological analysis, and numerical modeling.

In favorable settings, seismic records can detect lateral variations in Previous HitreservoirNext Hit quality. Because lithology variation causes a response similar to Previous HitporosityNext Hit variation, local calibration is necessary for successful application.

Statistical prediction methods are based on databases that incorporate Previous HitreservoirNext Hit-quality uncertainty with predictive variables such as depth or burial history. Previous HitPorosityNext Hit is usually the Previous HitreservoirNext Hit quality of interest, but permeability may be predicted from Previous HitporosityNext Hit and fabric where properly calibrated. Previous HitReservoirNext Hit quality risk is estimated from cumulative probability curves. Analog/statistical predictions are only as good as the analogs; where analogs are poorly chosen, results are poor.

Petrological approaches characterize diagenetic patterns and aid prediction of permeability from Previous HitporosityNext Hit. Specific depositional and diagenetic controls on Previous HitreservoirNext Hit quality can only be identified by this approach. Once Previous HitreservoirNext Hit-quality controls are identified, process and statistical models can extrapolate these results to other locations.

Numerical Previous HitreservoirNext Hit-quality process modeling is used where no good analogs are available, such as deep, rank-wildcat wells. The most successful models are based on quartz cementation in quartzose Previous HitsandstoneNext Hit. The burial diagenetic models available for Previous HitpredictingNext Hit average carbonate Previous HitporosityNext Hit are not yet reliable. Available numerical models for permeability prediction are complex and unreliable, reflecting the many controls on permeability evolution.

The real strength of Previous HitreservoirNext Hit-quality predictive technology comes from convergence of different approaches to the same answer. Two examples (a Cretaceous limestone and a Miocene shelf Previous HitsandstoneNext Hit) are examined to illustrate how these Previous HitreservoirTop-quality prediction techniques can be used.

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