Canadian Natural Resources Limited (CNRL) owns and operates a heavy crude oil treating facility near Elk Point, AB. This facility currently uses four horizontal heater treaters to effectively reduce the basic sediment and water content of the produced crude oil. In recent years, there has been a decline in the overall performance of the heater treaters. The goal of this project is to optimize the heater treaters and improve their operating efficiencies by determining both the optimum treating sizes and operating temperatures of the vessels.