With increasing availability of real-time downhole measurements in completions, more and more uses of these data are evolving. A deepwater field in the Gulf Of Mexico (GOM) consisting of numerous wells with permanent bottomhole gauges has been on a surveillance and diagnostic program for over 3 years. Pressure transient analysis of shut-ins give key performance indicators (KPIs) such as permeability-height (kh), skin (s) and current average reservoir pressure (Pave); the KPIs are summarized on a quarterly basis and compared with historical trends to check well performance. For the fields studied, the KPIs have proved valuable not only for production monitoring, but also as an investigative tool for larger-scale problems such as compaction, subsidence, depletion, and fines migration. This paper summarizes case histories from two fields where reduction in kh over time, and increasing skin over time led to a more in-depth study of the reservoir geomechanics. The geomechanical characterization of the reservoir allows for further insight into the behavior, increased knowledge of the production history, and allows for estimation of subsidence and compaction effects during future pressure transient tests.