Old Oil and Gas Field Properties That Maybe Influence Methane Concentration in the Overlying Wilcox Aquifer in Northwest Louisiana

Douglas Carlson and Marty Horn
[email protected]

Does current oil and gas development have a significant impact on methane concentration in the overlying Wilcox Aquifer? There are studies that indicate oil and gas development has a significant influence on overlying groundwater quality, but there are other studies that indicate oil and gas development has no significant influence. In northwest Louisiana (southern Bossier, southern Caddo, and northern De Soto Parish) the Wilcox Aquifer appears to be impacted mainly by methane released from underlying oil and gas plays of certain fields. However, is it a result of the field's development or a natural property of these fields? Which is more important? For six fields (Bethany-Longstreet, Caspiana, Elm Grove, Greenwood-Waskom, Holly, and Sligo) in the study area comparisons between fields yield significant differences of methane concentration between first to second ranked field, second to third ranked field, fourth and fifth ranked field, and fifth and sixth ranked field in terms of methane concentrations. The question is what field parameter is causing these differences? For this study a number of field parameters are examined to determine which could possibly be causing these differences. The properties considered are: density of oil and gas wells, both total and those spudded prior to 1970, i.e. before many environmental regulations on oil and gas development, depth of fields developed, depth of older versus total wells, total production of dry natural gas, and average density of natural gas production for each field considered.

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