Harmonic Pulse Testing for Well and Reservoir Characterization

Abstract

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.

Cyclic soft stimulation (CSS): a new fluid injection protocol and traffic light system to mitigate seismic risks of hydraulic stimulation treatments

“…The length of MTCs depends on the number of cycles required for the initial progressive cyclic injection phase (depending on the data available from previous injections, a minimum of four to six cycles are required to determine the fracture opening pressure FOP based on a change in slope in the pressure-flow rate curve, with two or three data points below the FOP in the matrix flow-dominated regime and two or three data points above the FOP in the fracture flow-dominated regime) and the uniform cyclic injection phase (according to Fokker et al (2017), a minimum of five cycles is required for good data quality of hydraulic pulse testing analysis, if this analysis is intended to be done), and the length of the LTCs. The optimization of this and other parameters needs to be further researched.…”

“…On day 3, the same volume was planned to be injected as on day 2 with same injection schedule, except that ten short-term (6 min) cycles with alternating injection rates between 1 l/s above and 1 l/s below the equivalent constant injection rate of day 2 are added on top of each HIR phase. This is done for hydraulic pulse testing analysis (Fokker et al 2017), for evaluating the technical feasibility and to study the differences between cyclic progressive injection and cyclic progressive pulse injection.…”