Publications

Pliocene limestone is well expose in the flank of anticlinal structure of Situbondo area. The limestone is belongs to Menuran Formation and Pacalan member. The Menuran Formation consists of marl and fine grained calcareous sandstone with tuff intercalation. Whereas Pacalan Member is generally consist of globigerinid limestone and gradually change to reefal limestone toward shallower setting.Field observation revealed that globigerinid limestone and chalky reef limestone showing good porosity and thus potentially become a hydrocarbon reservoir. The globigerinid limestone porosity are formed by primary inter and intra particle porosity within and between sand sized planktonic foraminifera. Oyong, Maleo and Wortel fields have productive hydrocarbon reservoir from this unit. Another reservoir potential is observed within chalky reef limestone, which generally has a good porosity such as in the NSO field in Malaka strait.Field observation indicates that the reefal carbonate can be observed in the northern of the anticline, while in the southern is composed of marl and fine grained turbiditic limestone. This situation reflect that during their deposition the northern part of the area was located the carbonate factory and gradually deepening toward to south. The Pacalan reefal carbonate has thickness about 100m and possibly going thicker toward the north.Petrography analysis showing that globigerinid limestone consists mainly of bioclasts, detrital siliciclastic grains and volcanic lithics. Fragments are cemented by spar calcite and show point to long contact texture. Bioclasts are predominated by benthic and planktonic foraminifers, fragmented bivalve tests, echinoids, trace amounts of red algae, and other unidentified ossils. Bioclast internal chambers are filled by spar calcite, glauconite or brown muddy clay.Primary porosity can identified as intra and inter particle occurs as isolated intraskeletal pores. And secondary porosity occurs as dissolution of matrix and locally as discontinued fractures in matrix that stop at grain boundaries.