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Geological reservoir characterization and performance assessment of unconventional Niobrara and Codell wells from the Hereford oil field, Weld County Colorado
Taylor, Chad E.
Taylor, Chad E.
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2023
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2024-12-24
Abstract
The Hereford Field lies in the north-central Colorado portion of the Denver Basin, approximately sixty miles northeast of the prolific Wattenberg Field. Hereford gained notoriety in 2009 when the 18-stage Niobrara completion of the EOG Resources Jake #2-01H produced more than 49 MBO during the first three months of production. Such a large volume of oil production in a short period proved that chalk lithofacies within the Niobrara Formation had significant potential as a viable unconventional resource play in the Denver Basin.
Drilling and completion methodologies employed in the Hereford Field have quickly evolved since the completion of the Jake well in 2009. The post-2015 development operations incorporate cemented pad-drilled laterals (XRL and SRL) utilizing high-volume plug and perf completions, mirroring designs employed in the contemporary generation of unconventional Niobrara and Codell wells drilled and completed with great success in the Wattenberg Field.
Niobrara and Codell reservoir quality within the Hereford Field appears regulated by the abundant fracturing associated with the adjacent E / NE trending paleo structure, the Morrill County High, which bounds the northern extent of the Hereford Field area. Fracture development and reservoir fluid dynamics appear linked to episodic reactivation of shear-driven faults and the extensive layer-bound normal fault system formed during the deposition of the overlying Pierre Shale. Furthermore, the structural complexity combined with the area’s complicated depositional and compactional histories has added an extra layer of reservoir heterogeneity observed in well-produced fluids throughout the Hereford Field.
The Niobrara B (B2) Chalk lithofacies and the Codell Sandstone are the primary reservoir targets within the Hereford area. As of October 2020, cumulative production from all unconventional wells within the Hereford Field study area exceeded 13.3 MMBO, 18.6 BCF, and 12.7 MMBW.
This study incorporates both vertical and horizontal well petrophysical data, fluid/sample geochemistry, lateral formation image logs, petrographic analysis, and legacy well production data located throughout the greater Hereford Field area to facilitate an integrated interpretation of controlling properties that govern unconventional reservoir quality and deliverability in the Hereford Field.
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