A new, alternative method, referred to as "direct synthesis", is proposed for interpretation of pressure tests in naturally fractured reservoirs.
Direct synthesis utilizes the characteristic intersection points and slopes of various straight lines from a log-log plot of pressure and pressure derivative data. Values of these points are linked directly to the exact, analytical solutions to obtain reservoir or well parameters. The direct synthesis method offers the following advantages: (1) accurate results from using the analytical equations to calculate reservoir parameters, (2) independent verification is frequently possible from a third unique point, and (3) useful information is obtained when not all flow regimes are observed, as a direct result of the additional characteristic values developed by the method.
Application of this technique is presented for single-well pressure tests in an infinite-acting naturally fractured reservoir with pseudosteady state interporosity flow, including the effects of wellbore storage and skin. New analytical and empirical expressions were developed as a result of this work. These expressions are an integral part of the technique, providing the desired accuracy and versatility.
Several field examples are given to clarify the technique and also illustrate the accuracy of the method. When possible, a comparative analysis with other methods is included.