The relationiship between sedimentary undation and hydrocarbon distribution in the formations above the mid-Miocence in northern and central deep-sea area of Kutei Basin

Indonesia

was idnetified through Milankovitch cycles da-ting of single wells

construction of chronostratigraphic framework

and calculatin of sedimentation rates in the study area.Four major undation periods(about 6

3.7

1.85 and 0.4 Ma)that had important relationships with hydrocarbon reser-voiring and distribution were recognized on fine sedimentation rate curves by using geological wave filtering methods.The undation period during 6 Ma was considered to control the formation of two plays(upper and lower).The upper play had the lower Pliocene-the Upper Miocene sandstone as the reservoirs and the bottom Lower Pleistocene-the middle Pliocene mudstone as the caprocks.And the lower play had the lower Upper Miocene-the top Middle Miocene as the reseservoirs and the middle Upper Miocene mudstone as the caprocks.Other undation periods also contributed to the development of reservoirs and caps controlled by the 6 Ma period.The undation period of 0.4 Ma was the long-eccentricity cycles among Milankovitch cycles and the major controlling factor for the formation of high-frequency sedimentary cycles.The study also shows that hydrocarbon distribution was controlled by the caprocks in the study area.All areas where favorable caprocks jointly controlled by the undation periods of 6 Ma and 3.7 Ma superimpose have oil/gas discoveries or abnormal seismic reflections.