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: A segregated flow mechanism of oil and water usually takes place in the presence of strong gravity forces in subsurface environments, having specific geometrical and petrophysical properties undergoing simultaneous flow of multiphase fluids. The segregated flow of oil and water is modeled as a two-layer reservoir system, based on the observed data. Accurate estimates or measures of the values of phase mobility of oil and water, in addition to the actual flow capacity of the formation are provided. Reliable reservoir characterizations and reserve estimations are provided based on the in-situ conditions of oil and water in the reservoir.

Abstract: Crossflow between two adjacent reservoir layers through leaky cement sheaths in offset wells during transient-pressure tests in one of the two reservoir layers is diagnosed and quantified. The obtained measures are determined based on individual well and layer properties. The pressure drawdown in the reservoir layer in which pressure transient testing is being performed is measured as a function of time. The longitudinal conductivity of a leaky cement sheath in an offset well and the pressure drawdown in the tested reservoir layer simultaneously control the crossflow rate to the tested reservoir layer from the adjacent reservoir layer at a given time.

Abstract: A measure of inter-reservoir cross flow rate between adjacent reservoir layers which are productive of hydrocarbons is determined. With passage of time, pressure differentials between reservoir layers can grow due to continuous production from an active layer. In addition, the flow area between an active layer and adjacent layers can grow with time for a given reservoir system. These changing pressure and flow conditions with time can contribute to substantial amounts of cross flow rates, which need to be accounted for when characterizing the commercial producibility of the active layer. The inter-reservoir cross flow rate is based on a measure of specific permeability and of cross flow rate within a reservoir layer which is obtained from pressure transient tests of the reservoir formations.

Abstract: A measure of the hydraulic conductivity, FC, is obtained to characterize the leaky medium behind well casing between adjacent hydrocarbon producing layers is a subsurface reservoir. The value of FC can be utilized in estimating the rate of flow from a secondary reservoir layer contributing to the total production through the wellbore based on the respective well pressures at a given time. The well pressures are calculated from a model based on the individual properties of and the amounts of fluid produced from these layers. Once there is a reasonable match between the calculated pressures and the measured pressures during a transient test, the parameters that have been used in calculating the model pressures are stored as characteristic parameters of the reservoir system. Such characteristic parameters are utilized in assessing the commercial producibility of the reservoirs.

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.