Possible Hydrothermal Dolomite Reservoir(s) in the Swan Creek Field, Tennessee
Bailey, Jeffrey R. 1, Evenick, Jonathan C. 2,. Hatcher, Robert D Jr. 2, and Weyland, H. Virginia 3
1Tengasco, Inc., Knoxville, Tennessee
2Department of Earth and Planetary Sciences, University of Tennessee, Knoxville
3U.S. Department of Energy, National Petroleum Technology Office, Tulsa, OK
A possible subsurface hydrothermal dolomite reservoir has
recently been identified in the Swan Creek field, northeastern Tennessee. Swan
Creek field is in a blind
, faulted anticline located beneath the shallow-dipping
Clinchport thrust wherein small-displacement duplex imbricates partly localize
production. A structural low is superposed on the northwestern flank of an
anticline that contains a pronounced increase in dolomite in the lower and
middle Stones River (Black River) Group, but hydrocarbon production from
surrounding wells is from the top of the Stones River (Carters Limestone). The
structural low is evident in maps contoured from top of the Lebanon Limestone
downward into the Knox Group, but is not present in younger horizons.
Dolomitization probably occurred prior to Alleghanian folding and faulting, but
deformation may have localized the hydrothermal zone and hydrocarbons, and did
not breach and drain the reservoir. Production probably results from secondary
enhanced porosity not cemented by late-stage, pre-Alleghanian fluid migration
and mineralization. Trends in hydrothermal fluid migration related dolomite
porosity have long been recognized in the zinc districts in Tennessee. For
hydrothermal dolomite plays, drilling off structure may be better than drilling
on structure. Locating this
structure in Swan Creek was as a result of secondary target development, with
the Knox Group the original primary target. Oil shows are widespread in Swan
Creek in the Stones River and Nashville Groups, but most oil production here is
from these dolomites. Wells associated with this hydrothermal event and
proximity to their off-structure locations, and disproportionate high cumulative
volumes, warrant special economic considerations and investigation.