Lost River - Karst Information Portal

New Albany Shale Gas Wells: A natural gas resource
that can impact karst features
Another aspect of the Harrison County
area is the presence at depths below about
900 feet of the natural gas-bearing New Albany
Shale. Since about 1995, much of southern
Indiana underlain by the blanket-like New
Albany Shale has been the focus of extensive
leasing of gas rights, exploration drilling, and
increasing production of natural gas from the
Ohio River northward past Indianapolis. The
New Albany is considered an “unconventional
reservoir” as it is not a more typical oil and gas
producing limestone or sandstone (Figure 28).
The presence of the historic Laconia Gas
Field in southern Harrison County has driven
greatly renewed modern interest. Natural gas
seeps were known to the American Indians and
early pioneers and commercial shale gas wells
have existed in Harrison County for nearly 150
years (Collett, 1878). As part of the modern
drilling wave Jet/Lavaway of Michigan drilled
three gas wells and one saltwater disposal well
on the property, along with many other wells
in the vicinity. These particular gas wells are
productive of modest amounts of gas, but gas
is likely to be produced for many years into the
future. The gas wells are about 1,425 feet deep
with the New Albany about 916–1012 feet
deep. As part of the long-term gas production
process, the shale must be dewatered of the
naturally occurring connate salt water to allow
the gas to escape from the shale. This water
must be disposed of per USEPA rules of the
Underground Injection Control Program,
which is administered in Indiana by the
Division of Oil and Gas of the Indiana Dept.
of Natural Resources.
An unavoidable but difficult to predict
aspect of drilling oil and gas wells within karst
areas is the penetration of the near surface
karsted limestone by the drilling process.
Eventually, a cave passage of some size could
logically be hit (known in the drilling business
Geology Field Trip
By Kevin Strunk
as a “lost circulation zone”), and the cave
environment could be impacted based upon
the nature of the drilling process. Besides the
physical borehole penetration, gas wells must
have steel casing cemented in place to act both
as a long-term groundwater protection barrier
and as a gas production conduit. Cement is
installed via pumping the slurry down the
inside of the casing which then travels back to
the surface on the outside of the casing within
the borehole. Of course, if a cave passage of any
size had been encountered, cement will flow
into that passage until or unless some barrier
becomes established which keeps the cement
within the borehole, including simply filling up
the void. The drillers may or may not know if a
smaller cave passage or conduit has been hit, or
may choose to ignore it. especially if there are
no subsequent problems.
Anecdotal rumors from geologists
familiar with caves or feeder passages being
supposedly encountered by gas wells drilled
in the mid-1990s in the Harrison County
area led the Indiana Karst Conservancy in
1998 to work with the Division of Oil and
Gas of the Indiana Department of Natural
Resources to develop a “Non-Rule Policy
Document” entitled “Drilling Procedures for
Karst Prone Areas.” This document called for
several precautionary measures to be taken by
drillers and cavers. There are several technical
considerations asked of the drillers, and the
Indiana Department of Natural Resources
asked the caving community to provide cave
location and system data so that obvious
large or otherwise significant caves could
be protected by being a within the area of
a designated “excluded cave.” To date, the
Indiana caving community has not been
able to determine protocols for releasing
cave location and map data in such a fashion
as to allow Indiana Department of Natural
125