Geothermal Patterns of Louisiana Salt Domes

Madhurendu Bhushan Kumar

Seven salt domes of Louisiana, in the shallow to intermediate depth ranges, were selected for the investigation of geothermal patterns associated with them. Equilibrium geotemperatures were determined from the bottom hole temperatures of wells drilled in the salt dome areas. Isothermal contour mapping was attempted for various depth levels, namely, 8,000, 9,000, 10,000, 12,000, and 14,000 ft. Limited availability of data permitted construction of isothermal contour maps on some of the depth horizons for each of the domes.

The shallow salt domes (above a depth of 4,000 ft) geothermally mapped for the present study are Minden, Jefferson, and Calcasieu Lake. At the 8,000-ft level, the Minden dome is characterized by a thermal low over the stock, circled by a pronounced thermal halo. At the 10,000-ft level, the Jefferson dome has a thermal high over the southern spine without cap rock and a thermal low over the northern spine with cap rock. At the 8,000-ft level, the Calcasieu Lake dome has two geothermal halos separated by an east-west-trending thermal low.

The intermediate salt domes (between a depth range of 4,000 and 10,000 ft) geothermally mapped are Bay Junop, Plumb Bob, Bayou Des Allemads, and West Bay. The Bay Junop dome is characterized by a geothermal high on the three mapped levels of 10,000, 12,000, and 14,000 ft. The Plumb Bob dome has geothermal lows over the stock surrounded by thermal highs on the 9,000- and 10,000-ft levels. For the Bayou Des Allemands dome, on the 8,000- and 9,000-ft levels, thermal lows are located over the stock and highs are toward the periphery; on the 12,000-ft level, the dome is characterized by a distinct high. The West Bay dome has a thermal low on the 9,000-ft level and thermal highs on the deeper levels of 10,000 and 12,000 ft.

The thermal highs observed in the relatively deep sections of the salt domes and their flanks in the immediate vicinity of salt stocks are attributable to the thermal conduction type of heat-transfer mechanism dominating the subsurface. Nonetheless, the thermal lows observed over the summits of the salt domes of salt stocks on shallow depth horizons are suggestive of a distinct influence of the circulating groundwater system operating through the fault network of the graben system characteristic of the shallow sections of the domal structure. Certain localized thermal halos observed on the shallow horizons over the dome may have been caused by younger and hotter "spines" of the salt diapir.

AAPG Search and Discovery Article #91029©1989 AAPG GCAGS and GC Section of SEPM Meeting, October 25-27, 1989, Corpus Christi, Texas.