TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn recent years, HSE concerns have been a driving force pushing towards emission-free well testing. Several methods have been proposed in order to attain that objective, the two most known being closed-chamber testing and downhole production/reinjection. With closed-chamber testing being of limited interest because of the reduced radius of investigation it offers, and harmonic testing being impractical due to time requirements, downhole production/reinjection appears as the only way of fully replacing conventional well testing.Planning such a test requires greater care than for a conventional test because the selection of an adequate injection interval is of major importance to the success of such an operation. The injected fluids must be contained within the disposal zone so as to avoid surface leakage but also so that the test data are not affected by an interference effect due to the injection process. There is also a great concern regarding the quality of the data because of hard downhole conditions. But if these challenges can be overcome, downhole production/reinjection can provide the same information as a conventional well test but with improved safety, no direct emission of pollutants and at reduced cost and test duration.