Print this pageAbstract: Development of Cost-effective Geothermal Probes for Use in Offshore Exploration and Environmental Work
NAGIHARA, SEIICHI
Department of Geosciences,
University of Houston, Houston, TX;
Institute for Geophysics, University of Texas at Austin,
Austin, TX
We have developed a cost-effective technique to obtain geothermal profiles
of the bottom sediments in relatively shallow (< 500 m) seas and lakes.
Information on the geothermal regime is important in offshore hydrocarbon
exploration, particularly in maturation analyses and detection of oil/gas
seeps. Geothermal measurements in estuaries and lakes are also important
in understanding their heat budgets. However, the techniques previously
available for underwater geothermal measurements are costly and time consuming.
The equipment is heavy, and its deployment requires a large ship equipped
with a heavy-duty winch and good station-keeping capability for which operational
costs are high. This requirement also precludes making measurements in
small inland lakes. We have developed a new geothermal probe that significantly
reduces these technical, logistical, and economical difficulties. The new
probe utilizes a thin (1-inch diam.), long (> 20-ft.) steel tube which
contains a number of thermistors. It free-falls through the water column
and, with its momentum, penetrates into the sediments. It can be easily
transported and deployed from a very small (i.e., inexpensive) ship. In
the current design, the probe transmits the temperature data to the surface
through a thin electrical cable. We tested the probe successfully in Lake
Travis, Texas in early June and mid-August of 1997. It was deployed in
the deepest (~55 m) part of the lake and recorded temperature profiles
down to 3 m subbottom. These data are currently analyzed for the regional
geothermal heat flow and the annual heat budget.
AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas