SEISMIC FACIES ANALYSIS OF TURBIDITE COMPLEX IN NGRAYONG FORMATION, EAST TUBAN AREA, EAST JAVA BASIN, INDONESIA

摘要

Ngrayong Formation is one of the most prolificrnhydrocarbon reservoirs in East Java Basin. Inrngeneral this formation is renowned for its richrncoarse quartz sandstone, widespread in East JavarnBasin during Middle Miocene. But studies signifyrnthe existent of three distinct main units in NgrayongrnFormation which indicate the regressive andrntransgressive phase of the depositional cycle. EastrnTuban Area represents the deposits of NgrayongrnFormation Unit II & III which comprise the fullrnpackage of turbidite complex associated facies.rnThis study in East Tuban encompassed an area ofrnapproximately 165 km2 covered with 2D seismicrnfrom several vintages along with data from twornwells. Detailed seismic facies analysis distinguishedrneach sedimentary unit with its unique seismicrncharacteristic guided by well data within the area ofrnstudy. Interpreters were able to identify differentrntypes of seismic character related to four highrnenergy depositional systems in bathyalrnenvironment: mounded (fan complex), chaotic fill,rnsheet drape, and channel fill feature.rnThe existence of hemiplegic layers which could berntraced in well-log and seismic data is an importantrnkey to separate each phase/cycle of turbiditernassociated facies.rnBased on the interpretation, Ngrayong FormationrnUnit II & III in East Tuban Area can be separatedrninto three different cycles of turbidite deposition.rnEach cycle ended with hemiplegic depositionrnspreading laterally throughout the area, thenrnpartially/locally eroded during the next tubiditerndeposition cycle. Facies seismic modelingrndefined mass transport complex, continuousrnsheet-like deposits, and channel-levee features which are present inrnsubmarine fans today. The study has identifiedrnseismic facies related to paleogeography ofrnNgrayong formation during the time of depositionrnin East Tuban Block. This information will enablerncompletion of the previous turbidite complex modelrnand can be used for future exploration purposes inrnEast Tuban Area, East Java Basin, Indonesia.