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Hanor, Jeffrey S.1, Kathleen A. Moran2
(1) Louisiana State University, Baton Rouge, LA
(2) Florida Department of Environmental Protection, Tampa,

ABSTRACT: Spatial Variations in Formation Water Geochemistry on the Field and Reservoir Scale, Upper Wilcox, Southeastern Texas

Spatial variations in the composition of produced waters collected from the Sabine Tram field, upper Wilcox, southeastern Texas provide information on probable fluid flow paths and compartmentalization by faults at this field. Previous work (Moran and Hanor) has established that the compositional variations in Cl, Br, I, and B of the Sabine Tram waters can be explained by conservative mixing of a dilute end-member having low concentrations of these solutes with a more saline end-member. The variations in Na, Mg, and Ca with Cl can be explained by non-conservative mineral buffering. Other diagenetically-important solutes such as K and SiO2, however, show a large, non-systematic scatter with respect to chloride. Some of this scatter can be resolved by examining spatial variations in composition across the 25 km2 extent of the field. The field is situated in four extensional fault blocks lying south of a major growth fault. Some spatial variations in salinity within individual fault blocks clearly reflect density stratification, with the less saline waters situated in subtle structural highs. However, there is also general south to north increase in salinity and decrease in dissolved SiO2, K/Na ratio, and Br/Cl ratio. These variations reflect probable northward lateral migration of low salinity waters derived from a deep source and enriched in silica, K, and Br and a progressive mixing with ambient waters of higher salinity. Discontinuities in fluid composition across faults reflect partial lateral compartmentalization.


AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.