Brine Chemistry Database and the Geostatistical Analysis of NORM-Related Measurements Joel Kuszmaul & Clayton McKay Department of Geology and Geological Engineering University of Mississippi

Database Configuration Brine samples – Mississippi Interior Salt Basin –219 Black Warrior Basin – 31 Wilcox Trend – 25 Total – 275 Chemical analysis –Ra activity, pH, TDS, anions, and cations Oil and Gas Board data

Database Status

Study Area i counties # NORM sample locations 0200Kilometers N Sample locations in Mississippi

Significant Findings from Texas 1)Barite scale is the most likely NORM host 2)Reservoir temperature ↑, potential for barite scale to precipitate ↑ 3)Radium activity >200 pCi/L only if TDS > 35,000 mg/L 4)Radium activity of barite scale is predicted to vary widely over Texas basins. Fisher, 1995

Significant Findings from Texas 5) No strong correlations between Ra activity and location within the state 6) Relation between Ra activity and ionic composition may exist but have no useful predictive ability 7) The most useful predictive factor for NORM in Texas: Radium activities > 100pCi/L found only in waters with > 20,000 mg/L chloride Fisher, 1998

Mississippi Findings to Date Relationships examined – 226 Ra and Cl־ concentration –Depth of production –pH, 226 Ra, and Cl־ concentration –Average chemical properties of fields and formations were compared

Plot of 226 Ra vs. Cl ־ concentration (Fisher, 1998)

Plot of 226 Ra and Cl ־ concentration in Mississippi

Plot of 226 Ra and 228 Ra (Fisher,1998)

Plot of 226 Ra and 228 Ra in Mississippi r 2 = 0.54

Increase in chloride with depth in Mississippi

Box plots of 226 Ra TDS with depth

Plot of 226 Ra, Cl ־ concentration, and pH by formation

Spatial Analysis 226 Ra and BaSO 4 saturation –Statewide –Basin –Formation Created NORM prediction –Low – depleted levels of both –Medium – elevated levels of one or the other –High – elevated levels of both

Low Cl ֿ Medium Clֿ High Clֿ County boundaries Statewide MISB Basin Eutaw Formation

Low 226 Ra County boundaries Medium 226 Ra High 226 Ra Statewide MISB Basin Eutaw Formation

Statewide MISB Basin Eutaw Formation No scale former Intermediate scale former Scale former County boundaries

Low - NORM Medium - NORM High - NORM County boundaries Estimation of NORM Problem

GroupFormationSample Numbers SelmaSelma Chalk F-1,2 II-HED-21 TIN-2-6,8,9 Eutaw II-HED-1,4-6,7,9-13,14 HE-1-12 BRN-2 EP-1-3 LRL-7 EU-3-14,16 OVT-7-9 GZ-2-7 RC-8 H-1-3 SND-1-4 TIN-7,10,12,16 EU-2 Upper Tuscaloosa Tuscaloosa GZ-1 OVT-4,6 PK-2 RC-2 II-HED-3 Series Gulfian Lower Tuscaloosa DV-5 EU4-12 HE-6 LRL-5 TIN LUX-1 LCRK-1-7 II-HED-2,15 BAX-1-15 DV-1 EU-1 OVT-1-3,5,10 SO-1 STC-1 WYC-5 Separation of wells into populations by formation (does not represent the entire section)

Establishing Homogenous Populations Analysis of variance 226 Ra and BaSO 4 saturation – similar means –Populations for spatial analysis Eutaw (34) Lower Tuscaloosa – Upper Tuscaloosa (35) Washita-Fredericksburg – Mooringsport (31) –Mean concentrations differ across most formations Selma Chalk – Eutaw (44) Hosston – Cotton Valley (10)

Geostatistics Create variograms – 226 Ra and BaSO 4 saturation –Spatial variation –Wells close together should have more similar characteristics than wells farther apart –Use in prediction of NORM

Opportunities for Feedback Help in identifying documented scale and NORM problems Chemical and statistical analysis vs. known problem areas –Scale problems –NORM problems

Questions