--> Abstract: Widuri Field, West Java Sea: Analysis of a Giant Structural and Stratigraphic Trap, by R. Young, W. E. Harmony, G. Juniarto, and B. Thomas; #91015 (1992).

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ABSTRACT: Widuri Field, West Java Sea: Analysis of a Giant Structural and Stratigraphic Trap

YOUNG, RAYMOND, WILLIAM E. HARMONY, GUNAWAN JUNIARTO, and BUDIYENTO THOMAS, Maxus Southeast Sumatra Inc., Jakarta, Indonesia

At the time of its discovery in April 1988, Widuri field was Indonesia's largest oil find since 1974. The field is a faulted anticline located in a Tertiary back-arc basin in the west Java Sea. The discovery well was drilled to depth of -3735 ft and penetrated 170 ft of oil pay in late Oligocene and early Miocene sandstones. Eight delineation wells and 42 development wells have confirmed a giant oil field over an area of approximately 500 ac. The oil is trapped in six separate reservoirs over a vertical interval of 350 ft. The individual oil columns often exceed structural closure and stratigraphy plays an important part in the trapping.

The lowermost reservoir is a thick, immature, fluvial sandstone with multistorey/multilateral stacking and a sheet geometry; the uppermost reservoir is a thin, 2,000 ft wide, distributary channel sandstone associated with a tide-dominated delta. The intermediate reservoirs show a complete gradiation in sandbody geometry between these two extremes. The systematic, upward decrease in sandbody width is accompanied by a change in the trapping mechanism from structural in the two sheet-like reservoirs at the base, to stratigraphic in the upper four reservoirs which have a restricted lateral extent and a favorable orientation with respect to structure. The stratigraphic trapping significantly enhances the structural closure and accounts for approximately 75% of the total recoverable reserve .

The geological models led to efficient field development and emphasizes the stratigraphic trapping potential in the area.

 

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)