Figure 1.

Schematic showing relative positions of geological formations in the Milne Point and/or Prudhoe Bay fields, Alaskan North Slope. Formations extend over many miles of the Milne Point and/or Prudhoe Bay fields and may tilt in regions, so depth range averages were used to depict the relative positions of the formations; the depth of each formation is not to scale. Prince Creek Formation water is used as make-up water supporting secondary recovery from Schrader Bluff and Kuparuk Formations. Prince Creek water is also used for artificial lift of Sag River produced fluids. Seawater injection is used to support secondary recovery from the Ivishak reservoir. Wells sampled for this study are labeled according to the formation from which they produce.