Abstract:The characterization of a reservoir is a process which starts from the beginning of the field (oil or gas) discovery and continuous to the field's abandonment. It quantitatively or qualitatively describes the characteristics of the reservoir using data available. In the determination of key well and reservoir parameters for reservoir characterization, it is very vital to understand the flow phases and how to adequately identify them to prevent the challenge of obtaining the require parameters from a wrong phase. Thus, to successfully interpret a well test result either manually or by the use of computer aided software, we need to understand the well, reservoir and boundary models to actually match the field data. This success depends on the range and quality of pressure and rate data available and also the approach adopted for the analysis. This study adopted the method of pressure transient analysis, PTA to determine key well and reservoir parameters. A general well test work flow and the procedure for buildup test is presented. Data were obtained from Agba 8 and Ukot wells in the Niger Delta region of Nigeria and analyzed using well test analysis software 'saphir' to generate the damage and flow parameters around the wellbore. Result shows that Agba 8 well is a candidate well for stimulation operation due to positive skin.