Publications

The Oligo-Miocene distributary to estuarine sandstones of the informally named Gabus Massive is the primary reservoir units for several offshore Natuna Sea Block B fields, including the Kerisi field. The Gabus Massive has contributed over half of the total oil production to date, and recovery factors suggest more production potential is possible, given an increased understanding of the reservoir connectivity and properties. Therefore, a higher resolution understanding of the depositional setting and reservoir architecture which integrates sedimentology, seismic stratigraphy and production data into a combined predictive reservoir properties distribution model is required to optimize field development. Datasets used in this analysis include approximately 170 ft. whole core data for sedimentology, standard well log data, 3D seismic data, and dynamic production data. Seventeen wells with standard logs were used in this study. The available 3D seismic data (Line 24.375 km and Trace 12.125, Width 295 km2) was used in interpreting reservoir element geomorphology. The Gabus Massive member is interpreted as a distributary system exposed to autocylic avulsion related floods. The lowest facies assemblage in the section consists of interbedded sandstone with planar and trough cross-bedding, ripple cross-lamination and bioturbated shale. The occurrence of Planolites trace fossils and syneresis cracks supports a delta plain with marine influence depositional setting interpretation. The primary distributary-estuarine sandstones consist of a basal unit with cross-bedded sandstone distributary channel facies, thin, massive sandstones and parallel laminated sandstones. These deposits are overlain by rapidly deposited, stacked cross-bedded sandstone, thin which increase in frequency and thickness upward. Climbing ripples and Teichichnus trace fossils indicate floods occurred. The flooding was recorded by biostratigraphy data with an increased palynosignal, which indicates paleo environment ranging from marshes of upper intertidal to lagoon of lower intertidal. Seismic data provided insight to the geometry of the distributary channel complex and limited individual channel dimensions. The channel complex is approximately 2 km wide and 40 ms thick with 200-250 m wide individual channels inside it. As a result of the study, an estuarine depositional model has been interpreted for Gabus Massive zones in the Kerisi field for input to rebuild the full field simulation model.