Variation of Methane and Ion Concentrations in the Wilcox Aquifer among several Neighborhoods near Bossier City, Louisiana

Douglas Carlson and Marty Horn
[email protected]

Underlying geologic parameters are impacting Wilcox Aquifer water chemistry for five different neighborhoods in southern Bossier Parish in northwest Louisiana as revealed by variation of ion and methane head space (MHS) concentrations. There is a statistically significant difference of MHS concentrations between study area neighborhoods with the highest median MHS concentration (11,870µg/L) in Longhorn-Bobbie neighborhood and the lowest median HSM concentration (2,960µg/L) in Cane Bend neighborhood. All five of the study neighborhoods are in or close to the Sligo Field. This indicates is smaller than field scale properties are important for impacting MHS concentrations. This study considers the properties that may cause these differences. In addition to MHS, concentrations of other ions in the Wilcox aquifer among various neighborhoods within the study area vary significantly. Other parameters considered (barium, bromide, calcium, chloride, magnesium, sodium, strontium, and total dissolved solids) show major differences among the five neighborhoods where the average concentrations vary by a factor of 2 or more among the neighborhoods. Elevated concentrations of barium, sodium, and chloride could indicate upward movement of waters from oil and gas fields into overlying aquifers, but, other ions (bromide, calcium, magnesium, and strontium) also vary significantly, often by factors over three. Hence, there must be other factors influencing ion and methane concentrations beyond which field lies under an area.

AAPG Search and Discovery Article #90167©2013 GCAGS and GCSSEPM 63^rd Annual Convention, New Orleans, Louisiana, October 6-8, 2013