Geothermal resource assessment of the Gueydan salt dome and the adjacent southeast Gueydan field, Vermilion Parish, Louisiana

Abstract

The fluids heated by the high thermal conductivity and vertical geometry of salt domes in South Louisiana have the potential to be an economic source of geothermal energy. The Gueydan dome is a piercement salt diapir in Southwest Louisiana lying along the Vermilion and Acadia Parish border. Isotherms indicate a thermal anomaly at the crest of the dome with formation temperatures of 62 ˚C recorded at 1346 m, which is too cold for a geothermal prospect. The shallowest salt encountered is at a depth of 1475 m, and the surrounding strata are Cenozoic sand and clay deposits. Previous geothermal assessments in the vicinity conducted in 1979 by Gruy Federal selected prospect locations off the east and south flanks of the dome for the Frio Formation. This study assesses the shallower, brine saturated Camerina A sand of the Frio Formation to the southwest of the dome where existing uneconomic oil and gas wells are shut in. Kehle corrected formation temperatures for the Camerina A range between 129 to 153 ˚C. The regional geothermal gradient for South Louisiana is 23 ˚C/km. Using shallow temperatures as a constraint, numerical modeling of the thermal regime and a temperature depth slice interpretation from well data indicates that the salt does not aid in increasing the thermal gradient for the Camerina A but instead regionally depresses isotherms because heat transport through the salt dome is more efficient. A hingepoint in the geothermal gradient at the top of overpressure reflects an increase in geothermal gradients through the Camerina A. However, limited well control to the north and west requires conservative reservoir volumetric estimates. Therefore, the Camerina A of Southeast Gueydan Field cannot be deemed a potential prospect based on proposed minimum bulk reservoir volumetric requirements of 1 km3 (Griggs, 2004). Numerical modeling of temperature fields around salt at deeper burial depths suggests that minimum temperatures required for binary power production can be reached through the heat focusing effect of salt domes when the rest of the dome is within the 100 ˚C to 120 ˚C range of the regional temperature regime.