Part 4 - Berg - Hughes Center

gray shale. In southern North Louisiana and East Texas, it is characterized by porous,
oolitic, and fossiliferous or fossiliferous-fragmental limestone.
Hermann (1976) described the James as reef-like deposits within an arcuate trend in
Winn and Natchitoches Parishes, Louisiana. His description of the James is as follows:
The principal limestone varieties within this trend are light-colored, pelletal-miliolid
calcarenite, pelletal calcarenite, pelmicrite, and caprinid biosparite. On well logs the
limestone is characterized by a leftward excursion of the spontaneous-potential curve
giving the zone the massive look of a reef section as much as 300 ft (91 m) thick in one
test well. However, the limestone appears to be nonreef in origin. Isopach studies have
shown that the James is a detrital deposit that accumulated in low areas. The trend
probably contains local patch-reef developments as indicated by the presence of a few
caprinid zones, but it does not appear to be a true reef trend as generally defined.
Southwest, south, and east of the main trend the James consists principally of interbedded
gray argillaceous micrite and gray shale, and on the north and northwest it consists of
some combination of interbedded gray micrite, oomicrite, oosparite, quartz sandstone,
and gray shale.
The James Limestone produces from numerous fields from east Texas, through
Louisiana to southern Mississippi. Production is mainly from rudist-coral-stromatoporoid
reef facies on salt-related structural highs in the interior salt basins of east Texas, north
Louisiana (Chatham field), and Mississippi (Hermann, 1976). When Chatham field was
discovered in 1960, original estimates were 400 million bbl oil in place, of which at least
230 million bbl are recoverable. The few test wells that have cored the James massive-
limestone interval indicate that porosity ranges from 10 to 15%, but is generally less than
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