Chemistry of Waters in the Geopressured Zone from Coastal Louisiana -- Implications for the Geothermal Development

Abstract

Detailed chemical analysis of 27 formation water samples from 7 oil and gas field in the Lafayette area, Louisiana, show the salinity of water in the geopressured zone ranges from about 22,000 to 275,000 mg/L dissolved solids. The large difference in the salinity of water in the geopressured zone from different field result mainly from interaction of water with salt beds. The concentration of H2S (<1 mg/L), silica (<114 mg/L), and a number of toxic trace metals are low in the geopressured geothermal waters. The relatively high salinity of these waters, however, and the moderately high concentration of environmentally toxic components (boron, up to 69 mg/L, and ammonia, up to 100 mg/L, for example) are unfavorable to geothermal development. The chemical data indicated that careful evaluation of the compatibility of the spent geothermal waters and the waters in the formation used for injection will be required to minimize loss of porosity due to precipitation of carbonates and sulfates of Ca, Sr, and Ba.