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Oryx Energy, Dallas, Texas, USA

Abstract: Revisiting Pennsylvanian Reservoir Architecture: Chitwood, Norge and NE Verden Fields, Caddo and Grady Counties, Oklahoma

Pennsylvanian-aged, Mid-Continent reservoir sandstones have, historically, been interpreted to have originated in fluvial channel to fluvially-dominated deltaic settings. In recent years, re-examination of cored intervals and outcrop analogs of many of these reservoir units has modified the original depositional models to include incised valley fills, tidally influenced estuarine to tide-dominated deltaic and shallow marine shoal settings. Incorporating these modified reservoir architectures into field development strategies has led to improved secondary recovery and maximized daily production volumes and ultimate cum.

In particular, the original geologic models for the 30-year-old Chitwood, Norge and Northeast Verden fields in Caddo and Grady counties, Oklahoma, have been substantially modified by re-examination of old field development cores and the recent acquisition of new cores and FMI datasets. Stacked, fluvial channels within the Huddleston Sandstone of Chitwood Field have been recognized as early transgressive valley fill with pronounced tidal channel/shoal reworking. Similarly, initial fluvial deltaic models in the Missourian Marchand Sandstone now reflect dramatic tidally-influenced to tide-dominated shoal flow units. With no abrupt seaward shifting of facies present, a prograding highstand deltaic setting is envisioned for the Marchand Sandstone in Norge and NE Verden fields.

By revisiting such fundamental geologic information, producers can better understand reservoir architecture for optimal well placement and more efficient design of secondary recovery technologies. This is especially true where the geologic data is utilized in current, reservoir engineering flow models.

AAPG Search and Discovery Article #90921©1999 AAPG Mid-Continent Section Meeting, Wichita, Kansas