Publications

Ngrayong Formation is one of the most prolific hydrocarbon reservoirs in East Java Basin. In general this formation is renowned for its rich coarse quartz sandstone, widespread in East Java Basin during Middle Miocene. But studies signify the existent of three distinct main units in Ngrayong Formation which indicate the regressive and transgressive phase of the depositional cycle. East Tuban Area represents the deposits of Ngrayong Formation Unit II & III which comprise the full package of turbidite complex associated facies. This study in East Tuban encompassed an area of approximately 165 km2 covered with 2D seismic from several vintages along with data from two wells. Detailed seismic facies analysis distinguished each sedimentary unit with its unique seismic characteristic guided by well data within the area of study. Interpreters were able to identify different types of seismic character related to four high energy depositional systems in bathyal environment: mounded (fan complex), chaotic fill, sheet drape, and channel fill feature. The existence of hemiplegic layers which could be traced in well-log and seismic data is an important key to separate each phase/cycle of turbidite associated facies. Based on the interpretation, Ngrayong Formation Unit II & III in East Tuban Area can be separated into three different cycles of turbidite deposition. Each cycle ended with hemiplegic deposition spreading laterally throughout the area, then partially/locally eroded during the next tubidite deposition cycle. Facies seismic modeling defined mass transport complex, continuous sheet-like deposits, and channel-levee features which are present in submarine fans today. The study has identified seismic facies related to paleogeography of Ngrayong formation during the time of deposition in East Tuban Block. This information will enable completion of the previous turbidite complex model and can be used for future exploration purposes in East Tuban Area, East Java Basin, Indonesia.