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regimes. If the flow regime characterized by a specialized plot is present then when the <br /> derivative calculated from that plot is displayed on the log-log plot, it will appear as a <br /> "flat spot"during the portion of the falloff corresponding to the flow regime. <br /> • Typical flow regimes observed on the log-log plot and their semilog derivative patterns <br /> are listed below: <br /> Flow Regime Semiloa Derivative Pattern <br /> Wellbore Storage ................. Unit slope <br /> Radial Flow ......................... Flat plateau <br /> Linear Flow ......................... Half slope <br /> Bilinear Flow ....................... Quarter slope <br /> Partial Penetration ............... Negative half slope <br /> Layering .............................. Derivative trough <br /> Dual Porosity ....................... Derivative trough <br /> Boundaries .......................... Upswing followed by plateau <br /> Constant Pressure ................ Sharp derivative plunge <br /> Characteristics of Individual Test Flow Regimes <br /> • Wellbore Storage: <br /> 1. Occurs during the early portion of the test and is caused by the well being shut-in <br /> at the surface instead of the sandface <br /> 2. Measured pressure responses are governed by well conditions and are not <br /> representative of reservoir behavior and are characterized by both the pressure and <br /> semilog derivative curves overlying a unit slope on the log-log plot <br /> 3. Wellbore skin or a low permeability reservoir results in a slower transfer of fluid <br /> from the well to the formation, extending the duration of the wellbore storage <br /> period <br /> 4. A wellbore storage dominated test is unanalyzable <br /> • Radial Flow: <br /> 1. The pressure responses are from the reservoir, not the wellbore <br /> 2. The critical flow regime from which key reservoir parameters and completion <br /> conditions calculations are performed <br /> 3. Characterized by a flattening of the semilog plot derivative curve on the log-log <br /> plot and a straight line on the semilog plot <br /> • Spherical Flow: <br /> 1. Identifies partial penetration of the injection interval at the wellbore <br /> 2. Characterized by the semilog derivative trending along a negative half slope on <br /> the log-log plot and a straight line on the 1/square root of time plot <br /> 3. The log-log plot derivative of the pressure vs 1/square root of time plot is flat <br /> A-7 <br />