Sequence Stratigraphy, Depositional Environments, and Production Fairways of the Haynesville Shale-Gas Play in East Texas
The upper Jurassic (Kimmeridgian) Haynesville shale is an important shale-gas resource play in East Texas and Louisiana. Estimated recoverable reserves are as much as 60 Tcf, with each well producing on the average of 6.5 Bcf. Haynesville carbonates are known for their excellent production from carbonate shoals and pinnacle reefs in the East Texas Salt Basin. However, sequence stratigraphy and depositional setting of the Haynesville shale is not well documented. Therefore, a sequence stratigraphic model of basinal shale to shelfal carbonate sequences was established to determine the extent of the shale-gas play and reservoir characteristics of the Haynesville shale-gas formation using wireline logs, seismic, and cores. We also estimated TOC from a petrophysical log model and calibrated to cores.
The upper Jurassic Smackover-Buckner-Cotton Valley Lime-Haynesville-Bossier Formations make up parts of two second-order supersequences (SS1 and SS2). The Haynesville composes the transgressive systems tract of the SS2 second-order sequence above the 144-m.y. sequence boundary, part of a supersequence from the lower Kimmeridgian to Berriasian (144 - 128.5 m.y.), where carbonates formed on the shelf and preexisting, salt-cored highs and organic-rich shales were deposited in the basin. Four to five regionally correlative third-order sequences compose the transgressive systems tract of the second-order supersequence. These cycles were correlated from basin to shelf, reflecting smaller-scale, sea-level fluctuations within the overall second-order transgression. Typically, each third-order sequence is characterized by a condensed section with TOC higher than the more calcite-rich shale intervals toward the top of each cycle. A marine condensed section marks the top of the Haynesville shale, coinciding with the second-order maximum flooding surface. Upper Bossier shale highstand deposits represent distal parts of the overlying Cotton Valley siliciclastic wedge that downlaps this maximum flooding surface. The upper Bossier is less organic rich, containing less TOC than the Haynesville. This study will define the extent, and sweet spots, of the Haynesville shale-gas play in East Texas.
AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009