The west block of Semanggi field is more productive than in east block. Stratigraphycally, from the ten layers of I until X, the producing layers is IIIB, VII and VIII. The producing layers thickness is between 5 to 13 meter. The 9 MFS datum has devide lithostratigraphy of area as follow: Tawun formation (Layers IX & X), Ngrayong (IV until VIII), Wonocolo ((III), and Bulu (I to II) until depth 875 meter. Regionally, MFS9 from Semanggi correlated to eastward in Nglobo field. The age of reservoir is between N8 to N9 (early of Mid Miocene). The seismic interpretation and acoustic impedance analysis is used to sub surface mapping reveals the west to eastward anticline, with double plunging upthrust. There are 10 normal fault between them with NNE-SW directly and downdip to eastward. The fourth compartment is separate productive wells, SO2 with SO4 and SO2 with S03. The Ngrayong formation is deposited in inner to middle neritic with strongly influenced to sea level fluctuation. The geological models is transgressive (aggradasi) sheet sand in shallow marine.
Key words: Reservoir Ngrayong formation, Layers IIIB, VII and VIII, transgressive sheet sand model.
Authors : Premonowati, Carolus Prasetyadi, Sigit Rahardjo, Jonli Sinulingga, Yayan Sulistiyana & Dadang Rukmana