Paper A presents a case study to look back on the performance of over 50 horizontal wells drilled in three different fields in the Mahakam Delta, offshore East Kalimantan, Indonesia. The common application of these horizontal wells is to produce! thin oil bands sandwiched between a gas cap and a bottom/edge aquifer. Based on well performance data, the lookback is mainly focused on the reservoir evaluation aspect of these horizontal wells. Reservoir and well performance is analyzed using a variety of techniques, varying from single-well analytical modelling (or decline curves) to more complex reservoir simulation. Based on statistical data resulting from the analysis of these wells, specific relations between reserves and reservoir-well parameters are identified which will be useful for predicting future well performance, especially during early prognosis.