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Toward a Better Definition of Haynesville Formation, Northern Louisiana Subsurface

Horn, Marty 1
1 Louisiana Geological Survey, Louisiana State University, Baton Rouge, LA.

The Haynesville formation recently emerged as an important unconventional gas play in the northern Gulf of Mexico Basin geologic province. Copious production driven by advanced drilling and completion technology has placed this stratigraphic interval among the most economically prospective in the north Louisiana and east Texas subsurface. However, definition of Haynesville within a formal regional stratigraphic model remains uncertain or ambiguous in some areas due to a history of inconsistent nomenclature, to a paucity of relevant geological data from previous exploration, and to limited communication of recently acquired data. Confusion over Haynesville definition has been a hindrance for property owners, operators, and investors, especially in recently prospective areas.

Published geological studies focused on lower Cotton Valley - upper Louark group stratigraphy emphasize facies relationships within overlying Bossier and underlying Smackover formations primarily because of their legacies as prospective intervals. Distinction between Haynesville vs. Smackover is variable in proposed models owing to similar lithologies, to limited distribution of hematitic sediments originally typed as Haynesville, and to intercalation of the Smackover - Haynesville interval. Distinction between Haynesville vs. Bossier is problematic particularly in the foreshelf facies where black shale typical of Bossier is volumetrically dominant, making regional recognition and extrapolation of the interval particularly difficult. The areal extent of the ‘Haynesville’ interval is a function of its definition parameters; one modern study concludes it to be of inadequate span for formation rank while others view it distributed over much of north Louisiana.

The present study attempts to improve definition of Haynesville over north Louisiana by examination and re-interpretation of subsurface geological data. Well log correlations constrained by detailed study of lithology samples from as many wells as available are the basis for modeling the Haynesville interval of the Louark - Cotton Valley boundary stratigraphy. The point of the modeling is to more accurately and consistently define Haynesville in a regional picture that will be useful in identifying potential plays for operators, investors, property owners, and regulators.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009