Abstract: A system for calculating the radius of investigation of a radial, composite reservoir has a processor with a clock, a display, and an electronic input coupled to the processor. The system divides the reservoir into a predetermined number (n) of concentric regions, and the processor is programmed to calculate periodically the radius of investigation based a starting time or elapsed time, and data relating to the reservoir rock, fluids, and geometries of each of the n regions. The processor computes the radius of investigation using at least one of Equations (1), (2), and (6) through (12) set forth in the specification, if using the System of U.S. Oilfield Units, or using an equivalent equation if using other units. These equations account for the effects of variations of both permeability and storativity in composite reservoirs on the radius of investigation with elapsed time.

Abstract: Disclosed is a method for transient testing of an oil well to determine the individual, distinct skin factor components of an apparent skin factor, which includes opening the well to a first predefined choke setting to allow the reservoir fluid to flow through the well for a first predefined period of time, and measuring a production rate of the reservoir fluid through the well, when the first predefined period of time expires. The method further includes performing a shut-in of the well for a first predefined build-up period, and repeating, when the first predefined build-up period expires, the steps of the flowing, the measuring, and the performing for at least two additional choke settings. The distinct skin factor components of the apparent skin factor are determined using a graphical relationship between the determined apparent skin factors and the measured production rates.

Abstract: A system for calculating the radius of investigation of a radial, composite reservoir, comprises a processor; a memory and, preferably, a clock electronically coupled to the processor; a display electronically coupled to said processor; and an electronic input coupled to said processor. The processor is programmed to calculate the radius of investigation, at any given time, in the reservoir based upon a plurality of user inputs including the number of concentric regions n into which the reservoir is to be divided, a starting time or elapsed time, and data relating to the reservoir rock, fluids, and geometries of each of the n regions. The processor computes the radius of investigation using at least one of Equations (1), (2) and (6) through (12) set forth in the specification, if using the System of U.S. Oilfield Units, or using an equivalent equation if using other units.