Publications

The Pertamina Hulu Energi Offshore North West Java (ONWJ) Block is well known as an oil and gas producer. The northwest Java basin province consists of volcanic clastic, siliciclastic and carbonate sediment filled with half-graben basins formed on the southern edge of the Sunda Shelf plate or craton during the Tertiary period. The Gazeta Field is part of PHE ONWJ located 120 KM northeast of Jakarta. The Gazeta field has produced from major reservoirs, including the main Massive Interval Upper Cibulakan Formation in Early-Middle Miocene which is a shallow marine deposit with the tidal sand ridge. This study focuses on the main interval and seeks to understand the characteristics, internal details and sedimentation process of the tidal sand ridge deposit using core description. Detailed interpretation of the sandstone body reservoir is necessary to get a better understanding of the reservoir behavior and can improve the future development strategy which has the same character as other intervals in the ONWJ Basin. Core description is significant to identify the sand ridge sub facies association (SFA). Those stages are embryonic stage (SFA 1) accretion stage (SFA 2) abandonment stage (SFA 3) (Lopez et al., 2016). The detailed description uses two wells (RR-4 and RR-15) including RR-22, RR-23, RR-27, and RR-29 Reservoir zones consisting of sandstone, claystone, siltstone, limestone and shale with sediment structures of flaser, lenticular, wavy, tight limestone, clean sandstone and bioturbation and then coarsening upward pattern which are characteristics of tidal sand ridge. Embryonic stage is an early stage deposit of tidal sand ridge with clay, silt, shale lithology, then the accretion stage is main sand body with flaser, clean sand-dominated, and the abandonment stage with clay, shale, and tight limestone. Tidal sand ridge becomes a good reservoir because in the bottom and top it has the impermeable deposit and the main sand body can therefore be classified as a good reservoir.