The field of interest was discovered in late eightees. The main productive zone 1 obtained oil. The reservoir 2 is uplift basement located in the center of the field, to which reservoir 1 is pinched out and confined to reservoir 2 from east and west. The reservoir 1 has a gas cap and production is characterized by high GOR with no signs of any decline despite the long production period. Therefore, all the available information of geology, production and pressure transient analysis were reviewed. There has been no production from the basement and just one well has been observing reservoir pressures for last ten years. These data were plotted bringing to unexpected result. The plot showed stable declining trend. So, there was a question – how does it happen when pressures are continuously decreasing while there is no production from the reservoir 2? Thus, gas sampling was performed on all three parts, pressure buildup and interference tests were conducted, geological data were reviewed and analyzed.
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