Technical Screening Guides for the Enhanced Recovery of Oil

Abstract

Members SPE-AIME Abstract The technical screening guides which are used to select enhanced oil recovery methods are described. The background and logic behind the various criteria are covered, and a brief description of each method is included. Economics are discussed, but the emphasis is on the technical guidelines. A distinction is made between the oil properties and reservoir characteristics required properties and reservoir characteristics required for each process. Generally, steamflooding is applicable for viscous oils in relatively shallow formations. At the other extreme, CO2, nitrogen, and hydrocarbon miscible flooding work best with very light oils at depths great enough for miscibility to be achieved. Both steamflooding and in-situ combustion require reservoirs of fairly high permeability. Chemical flooding processes (polymer, alkaline or surfactant) are applicable for low-to-medium viscosity oils where depth is not a major consideration. However, at great depths, the higher temperature may present problems in the degradation or consumption of some of the chemicals. Current values of the technical Screening guides for the more common enhanced recovery procedures are given in tabular and graphical form. procedures are given in tabular and graphical form. By the use of a simple graphical technique, it is shown that there is a complete spectrum of enhanced oil recovery methods available for all oils, ranging from the very lightest to the heaviest oil or tar sand. Introduction Screening guides or criteria are among the first items considered when a petroleum engineer evaluates a candidate reservoir for enhanced oil recovery (EOR). The source most often quoted for screening criteria is the 1976 National Petroleum Council (NPC) report on Enhanced Recovery, which lists the criteria for six enhanced recovery methods. The NPC report will continue to be the authority on technical screening criteria, especially when the new edition is published within the next year. other guidelines have been suggested for the application of a range of enhanced recovery methods and for individual processes. processes. Most companies have their own technical screening criteria for enhanced recovery. The company guidelines are often a combination of the NPC values and parameters which have been adjusted to include the latest data from the laboratory and field. After the technical screening guides have been applied to a given prospect, the more stringent economic screening process must take place before the final decision is made. place before the final decision is made. Experienced engineers may be adept at utilizing both kinds of screening guides; however, newer engineers often need a systematic presentation of the technical screening criteria. This paper is our attempt to fulfill this need and provide the reasons for the specific parameters which are listed. Our approach is to present the technical screening criteria in tables and graphs along with discussion of the principles or basic recovery mechanisms which limit the technical success of each method. we draw a distinction between the criteria which are related to oil properties and to those which depend on reservoir characteristics. In the literature, the desired oil or reservoir values are usually given as either an upper or lower limit for each characteristic. However, these values are not absolute; a number of field projects are underway with oil or rocks which are projects are underway with oil or rocks which are outside the published limits. Therefore, to give a more realistic picture, we have developed graphs which show a desired range of values for some of the more important characteristics such as oil viscosity. The figures show that there is a variety of enhanced recovery methods available for all oils, from the very lightest to the heaviest oil or tar sand.