The giant Arun gas field has estimated recoverable reserves on the order of 18 to 20 Tcf and has 78 producers, 11 injectors, and 4 observation; wells. Approximately 100 well tests have been performed. Analysis and interpretation of these well-test data suggest that there is condensate accumulation near wellbores and there are well-interference effects caused by competing production wells. A two-zone, radial composite reservoir model was found to diagnose condensate accumulation effectively. A new approach was developed for well-test-data analysis of multiwell-reservoir systems that treats well-interference effects as a "regionaI pressure decline" and accurately represents well-interference effects observed in Arun held.