Harmonic Pulse Testing for Well and Reservoir Characterization

For decades, well tests have been widely used in the oil industry for evaluation of well productivity and reservoir properties, which provide key information for field development and facilities design. In conventional well tests equilibrium conditions are required in the reservoir before the test. Furthermore, a single well only can be produced at a time, inducing one or more pressure draw-down periods followed by a final pressure build-up which are the object of the interpretation. Harmonic testing has been developed as a form of well testing that can be applied during ongoing production or injection operations, as a pulsed signal is superimposed on the background pressure trend. Thus no interruption of well and reservoir production is needed before and during the test. If the pulsed pressure and rate signal analysis is performed in the frequency domain, a strong similarity exists between the derivative of the harmonic response function versus the harmonic period and the pressure derivative versus time, typical of conventional well testing. Thus the interpretation of harmonic well tests becomes very straightforward. In this paper, we present the derivation of type curves for the most commonly encountered well and reservoir scenarios and we validate the type-curves developed for horizontal wells against real data of a harmonic test performed on a gas storage well in Italy.