Initial electrical submersible pump (ESP) designs for the Stag oil field on the Australian Northwest Shelf were based on a low gas/oil ratio (GOR) and a high-viscosity 19degreesAPI crude oil. Higher-than-forecasted gas rates and gas/oil separation in the 3,300-ft-long horizontal production section resulted in slugs of gas and oil. With the onset of water production, high volumes of produced sand compounded, the problems. The full-length paper reviews in detail the evolution of the ESP design, which initially ran for only 191 days, but now averages 511 days.