WATER-SALINITY VARIATIONS IN THE IVISHAK AND SAG RIVER RESERVOIRS AT PRUDHOE BAY

More than 2,000 chloride-concentration measurements made on extracted water from oil-base-mud cores show areal and vertical variations in th e salinity of Ivishak and Sag River reservoir brines. These data compa re favorably with compositional analyses of produced and extracted wat er, spontaneous-potential (SP) analyses, and resistivity-log calculati ons. In calculating water saturations with the Archie equation, it was critical that variations in resident water resistivity be recognized. This paper describes the variations observed and the work done to val idate the extent and magnitude of the salinity variations.