ABSTRACT: Cyclostratigraphy, Lithostratigraphy and Geostatistical Modeling of the Upper Jurassic Smackover and Norphlet Formations, Hatter’s Pond Field, Mobile County, Alabama
The Hatter’s Pond Field, Mobile County, southwestern Alabama, produces wet gas from the Upper Jurassic Norphlet and Smackover Formations. The Norphlet consists of eolian and reworked shallow marine sandstones. The overlying Smackover is comprised of dolomitized, peloidal wackestones, packstones and grainstones interbedded with anhydrite deposited on a restricted carbonate ramp, during a regressive phase of the Smackover transgression. The field consists of a ~11 km long NS trending anticline bounded on the east by a major normal fault that forms the updip seal where Smackover and Norphlet reservoirs are in contact with the Buckner evaporates.
Petrographic analysis and lithofacies from six cores were used to establish a cyclostratigraphic framework for the Smackover. High frequency cycles correspond to gamma-ray well log cycles that correlate across the field providing a detailed cyclostratigraphic framework.
Cyclostratigraphic and lithostratigraphic geostatistical earth models, utilizing data from 39 wells (gamma-ray logs and core-derived porosity), were constructed. Sequential Gaussian Simulation was used to distribute porosity by layer. Porosity semivariogram range parameters are 4-7 km with a SE trend. Permeability was added using layer specific porosity-permeability transform equations. In both models the Norphlet was treated as a massive unit. The aggradational and progradational nature of the Smackover at Hatter’s Pond was best captured by cyclostratigraphy.
The earth model is being used to construct a compositional fluid flow simulation model for the Smackover and Norphlet reservoirs. Objectives of the simulation include improved understanding of reservoir performance and reserve estimation. Results from the simulation will be incorporated into a depletion plan.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.