Numerous steps are involved in evaluating enhanced oil recovery (EOR) methods for field application. Technical screening guides are consulted for initial determination of applicability. This is followed by a comprehensive analysis of fluid, rock, and rockfluid interactions. Prior to displacement studies, decisions concerning type of core, core size, and experimental apparatus are made considering scaling laws, dispersive effects, duplication of reservoir conditions, and the unique parameters of the particular process being utilized. Experimental flooding techniques and interpretation of subsequent results are discussed for each type of EOR method. These tests are based on those found in the published literature and experience at this laboratory.
EOR methods discussed include polymer, surfactant-polymer, alkaline flooding, thermal, and miscible and immiscible gas displacement. The critical flow study parameters are considered for each method. What can be learned from each type of coreflood experiment is described and limitations are given. Specific techniques used in carrying out each type of coreflood experiment are presented. The coreflooding aspects of emerging EOR technologies, such as microbial methods and emulsion blocking in steamflooding, are examined.
Classic scaling criteria and dispersive constraints indicate core lengths of about 4-ft are necessary to linearly scale reservoir conditions. Composite cores are often constructed from available field material to meet scaling constraints. In immiscible displacements, the introduction of multiple capillary discontinuities significantly alters oil saturation distribution. Berea sandstone and sandpacks, widely used in petroleum research, are found to be more heterogeneous than is commonly believed. To accurately address the problems of laboratory evaluation of individual EOR methods, appropriate laboratory apparatus and techniques should be designed and utilized. Concurrently, a realization of the limitations of the laboratory model is necessary for accurate interpretation of results obtained.