Shale Gas Potential in Triassic Strata of the Deep River Basin, Lee and
Chatham Counties, North Carolina with pipeline and infrastructure data
Fig. 1. Map showing the distribution of Mesozoic
basins in the eastern United States (from
Robinson and Froelich, 1985). Lee and Chatham
counties are located inside the red box.
50 Miles
Suggested citation: Reid, Jeffrey C.,
and Taylor, Kenneth, B„ 2009, Shale
gas potential in Triassic strata of the
Deep River Basin, Lee and Chatham
counties, N.C. with pipeline and
infrastructure data: North Carolina
Geological Survey, Open-file report
2009-01, 2 p.
Fig. 2. Map showing the distribution of
Mesozoic basins in North Carolina (from
Reid and Milici, 2008).
Blue Ridge
Piedmonl
Coastal Plain Triassic basins
The Deep River Basin is a 1 50-mile long northeast-trending half-graben with a steeply-dipping eastern border fault in central
North Carolina (Fig. 1 and 2). The basin is divided into three sub-basins, which are named (from north to south) the Durham
sub-basin, the Sanford sub-basin and the Wadesboro sub-basin. The three sub-basins are filled with -7,000 feet of Triassic
strata, which are divided into the following three formations in descending stratigraphic order (Figs. 3 and 4): (1) Sanford
Formation (red and gray siltstone and shale); (2) Cumnock Formation (black shale, with some beds of gray shale, sandstone and
coal); and (3) Pekin Formation (gray sandstone and shale). The Cumnock Formation includes a -800 foot thick interval of Upper
Triassic (Carnian) organic-rich black shale. This shale extends across -25,000 acres, at depths of less than 3,000 feet in the
Sanford sub-basin, Lee and Chatham counties. Organic geochemistry and thermal maturation analyses indicate that the black
shale in the Cumnock Formation is gas-prone, and that values of total organic carbon (TOC) exceed 1.4 percent in places. The
Cumnock Formation contains systematic fractures that are observable in outcrop, in drill cores and on 1:24, 000-scale geologic
maps superimposed on LiDAR data. The primary fractures trend northwest, whereas the conjugate fractures trend northeast. In
some places along the west side of the basin, the primary fractures are filled with diabase dikes (that locally heated the Cumnock
Formation), although mapping in underground coal mines (now closed) has shown that the diabase dikes do not extend far into
the basin.
Six of the 28 wells (including old coal holes) that have been drilled in the Cumnock Formation have reported natural gas and
oil shows, and two shut-in wells have reported pressures of 900 psi and 300 psi. One of these shut-in wells (Butler #3) is located
within 3.5 miles of a six-inch natural gas distribution line to an industrial park with large volume gas users (Fig. 5). Well drilling
preceded acquisition of -75 miles of seismic lines that provide 3-D control in the Sanford sub-basin and parts of the Durham sub¬
basin. Deeper parts of the Sanford sub-basin are unexplored. Preliminary seismic interpretation suggests multiple stratigraphic
and/or structural targets.
In the Deep River Basin, many families sold the mineral rights to their property to pay for taxes during the Great Depression,
and significant underground coal mining occurred during the 1930s. Information on mineral rights and deed transfers may be
found using online county land records. The North Carolina oil and gas law may be viewed online at the following Web site:
http
://
www. ncleg.net (see short cut to General Statutes). Additional information on natural gas and oil, and permitting in North
Carolina, may be found in N.C. Geological Survey Information Circular 36, available online at: www.qeoloqv.enr.state.nc.us (see
‘Publications’ at that URL).
Seismic data, drill cores, cuttings, well logs and other data from the Deep River Basin may be examined at the facilities of
the North Carolina Geological Survey in Raleigh, N.C. See contact information on the next page.
