This Interim Report is submitted in partial fulfillment of Task XX (which was modified from previous tasks) of DOE Contract No. DE-ACOl-76ETI0145 (formerly EX-76-C-Ol-2025), which requires GURC to " develop a methodology to analyze and display actual EOR field case histories and calculate EOR costs at various rates of return on invested capital" and to " prepare a special report on the GURCTCU computer model "The material in this report covers development of an analysis methodology and of a computer program to perform the above Contract Task. Several examples are provided to illustrate these capabilities. Because of the high interest in the surfactant-polymer process, and the relatively large number of field tests receiving DOE funds, this EOR method received major emphasis during the first stage of computer program development. Even though the program documentation is in terms of the surfactant-polymer process, the methodology and most of the program modules are sufficiently general that several other EOR processes also can be utilized quite easily. In this report to demonstrate model capability, surfactant polymer project cost sensitivities were estimated varying: polymer cost, surfactant slug cost, well operating cost, and recovery efficiency. Other parameters that can be varied include the usual reservoir parameters, e.g., net pay, porosity, residual oil saturation, and some of the economic parameters, including drilling and equipment. costs, injection costs, royalty, etc. At the completion of this Task, and extensions thereof, it is planned to have available for "public" access a generalized computer program that will facilitate economic sensitivity analysis of any enhanced oil recovery process whose reservoir performance can be characterized by a curve of cumulative oil recovery efficiency versus cumulative pore volues of injected fluid. At that time, a Final Report on this project will be submitted. EOR processes that can be handled with the above described curve include "multi-slug" processes like surfactant-polymer or carbon dioxide miscible (the water-alternate-gas, i.e., the WAG, method) and 1'continuous" injection processes like steam drive, in-situ combustion, or continuous carbon dioxide injection. Alternate iniect-produce-inject processes like cyclic steam injection cannot readily be handled with this program as it is now formulated.