Foinaven was the first oil field discovery in the deep waters west of the Shetland Islands. The field was (re)discovered in deep water sands of Late Paleocene age in 1992 by Well 204/24a-2, and from late 1993 was the subject of an accelerated appraisal programme leading to field development approval in November 1994. Production started in November 1997 through a subsea system connected to a floating production, storage and offloading (FPSO) vessel with shuttle tanker export.Continual improvement in the quality of the seismic data across the field coupled with the large amount of well data acquired during the appraisal and development programmes has reduced much of the static uncertainty associated with estimates of the STOIIP (oil initially in place) and reservoir geometry. However, significant issues relating to channel inter-connectivity, the field’s connected reserves, well production decline and pressure maintenance have only been able to be addressed through the acquisition of dynamic data. The key to these data has been an extended well test (EWT) performed on a horizontal appraisal well in Panel 3.With 42 × 106BBL of reserves, the Panel 3 segment of Foinaven is the second largest of the five segments identified in the field to date. The principal reservoir zone is made up of two separate seismically-identifiable channels, which may or may not be in good communication. For either outcome we planned to achieve good recovery efficiency by appropriate placement of the two pre-drilled horizontal producers. The seismic geometry of the channels, combined with the analysis of a pressure build up (PBU) following a short clean-up flow on one of the wells, indicate the presence of a potential barrier between the two targeted channels. Recent longer-term data from down-hole gauges shows similar 15 psi depletion in the both wells as a result of the extraction of 437016 BBL during the EWT. These data have indicated there is some communication between the channels and have been invaluable in maximizing understanding prior to field start-up.