This paper presents a case history study that demonstrates a method to monitor wellhead-deliverability performance for flowing oil wells in a manner similar to gas wells. Separator test data measured for production allocation are used along with the material-balance relationship and multiphase-flow analysis to develop a wellhead backpressure curve for flowing oil wells. An equivalent wellhead static pressure for flowing oil wells is described and shown to be a function of reservoir depletion and multiphase-flow rate. Determination of the equivalent wellhead static pressure extends our understanding of wellhead backpressure analysis for both flowing oil and gas wells. A case history example demonstrating the application of the methods described in the paper is developed with the separator test data from Point Arguello field wells. The resulting wellhead backpressure curves clearly defined individual well deliverability and proved to be valuable diagnostic tools to monitor well performance and to quantify production potential. We show that the procedures developed in this paper are directly equivalent to procedures applied to conventional gaswell wellhead backpressure analysis commonly used in the industry to monitor gaswell performance. By monitoring flowing oilwell performance with the methods described in this paper, operators can address the challenge of maintaining well productivity and field production plateau.