--> Abstract: Woodford Reservoir Quality in the Western Arkoma Basin, Jack Breig, West Kubik, #90097 (2009)

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Woodford Reservoir Quality in the Western Arkoma Basin

Jack Breig1,   Ciro Perez2,  West Kubik3

1Newfield Exploration ,  2Newfield Exploration , 3Newfield Exploration

The Woodford formation is a highly siliceous, organic rich source rock, currently under development as an oil, condensate, or gas reservoir in various parts of the Arkoma, Ardmore, and Anadarko basins of Oklahoma.

Although commonly referred to as a ‘shale’, the Woodford of the western Arkoma Basin is more properly described as a siliceous mudstone, comprised of thin, alternating beds of chert and fissile shale. Both facies contain organic carbon, with elevated TOC concentrated in the fissile beds.

The reservoir in general, and chert layers in particular, contain an extensive network of micro-fractures, attributed to stresses associated with hydrocarbon generation and expulsion. Most fractures are now completely healed by quartz or dolomite cement.

Geomechanical tests on core samples, in combination with observations on mechanical instability in certain horizontal wells and hydraulic fracture treatments, suggest that microfractures are reactivated during changes in reservoir stress state.

Hydraulic well stimulation appears to create a highly ‘shattered’ region in the vicinity of a well completion.

In spite of matrix permeability measurements in the nanodarcy range, the stimulated, fine-scale, fracture system can yield in hydrocarbon recovery factors of 50 – 80% of gas in place, as observed by reservoir simulation and production studies.

 

 

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