Publications

Offshore North West Java (ONWJ) is a mature area, it has been explored and exploited for almost 45 years. All large conventional prospects that target the Parigi, Main, Massive, Baturaja and Talang Akar formations have been drilled and produced. New concepts and ideas are therefore needed to find new and large resources in ONWJ. The objective of this study was to reconstruct new tectonostratigraphy of the North West Java Basin and find new petroleum system plays in the Pre-Talang Akar Formation (Pre-TAF). This study examined 315 wells, 43 cores, 35 age dating, and 3D and 2D regional seismic data. Based on the regional chronostratigraphic correlations, we have concluded that there was a new sedimentary sequence deposited during the Eocene time, named the Pre-TAF Formation. The sequence consists of carbonate, interbedded calcareous sandstone and shale, a thin coal seam and tuffaceous material, indicating a marine sediment environment. The carbonate below the Talang Akar Formation in KL Field has proven to be a gas bearing reservoir that has produced a cumulative 11 BCF of gas since 2011. In the past it was classified as the basement, but in 2014, strontium age dating confirmed that it was from the Eocene age and it was re-classified as Pre-TAF carbonate. The carbonate has a dual porosity system (intergranular and fractured) ranging from 8-25%, which makes this rock an excellent Pre-TAF reservoir target. This conclusion may also lead to the new interpretation that the top basement horizon is deeper than estimated before. As a consequence, the E-15 Graben area is suspected as being a new sub-basin that could potentially be a new hydrocarbon kitchen that directly charges the hydrocarbon into the basement and pre-TAF reservoir target. This new concept highlights the possibility that significant hydrocarbon resources can still be found in ONWJ.