PRODUCED WATER CHEMISTRY AS A GUIDE TO RESOURCE DEVELOPMENT IN THE MID-CONTINENT MISSISSIPPIAN PLAY NORTHEAST OKLAHOMA: OSAGE AND KAY COUNTIES

Unlike most conventional oil and gas resource plays, the Mid-Continent Mississippian play is characterized by copious amounts of produced waters. Understanding the spatial variability of produced water chemistry can be a significant tool to guide resource development and production within this and other unconventional opportunities. Major ion, select trace element and stable isotopic chemistry of produced waters was assessed for samples collected from oil and gas wells in Osage and Kay Counties, Oklahoma, located on the Cherokee Platform, with an overall goal of characterizing the three dimensional spatial variance of the hydrochemistry of the produced waters. Thirty six samples were collected from the surface tree of oil wells and sent for analysis to Green Country Testing, an Oklahoma Department of Environmental Quality (DEQ) and National Environmental Laboratory Accreditation Program (NELAP)-certified laboratory. The produced waters were collected from both vertical and horizontal well completions within the Western Interior Plains (WIP) aquifer system, which include the lower Mississippian units of interest. Additional samples were taken from the overlying Pennsylvanian producing section to more fully determine the variability of the produced water of the Western Interior Plains (WIP) aquifer system in the study area. In all, 29 samples were collected from units defined as Mississippian Lime, 4 from Mississippian Chat, and 3 from the overlying Pennsylvanian section. Spatial variation of water chemistry may result from several mechanisms including 1) varying formation permeability, 2) varied lithology within the formation, 3) diagenetic and post-diagenetic alteration, and 4) mineralization resulting from migrating fluids including hydrothermal alteration. Understanding the mechanisms responsible for spatial variation of produced water chemistry is critical in these high water yield systems to help minimize exploration costs, and optimize development and production of oil from the reservoir.