Publications

The Talang Akar reservoir facies in the Jatibarang sub-basin along the northern border fault are made up of heterogeneous, coarse-grained sandstones to sandy mudstones deposited in a coarse-grained fluvial-delta setting. These deposits were historically regarded as alluvial-fan facies including highly anisotropic braided-stream fill and debris flows. Accurate geological models for reservoir performance forecasting were difficult to develop due to a general lack of adequate geological data that describe the frequency of various reservoir attributes for these types of deposits.More recent analysis of sedimentology and ichnology was used to re-interpret these deposits as coarsegrained fluvial-deltaic to marginal marine with deposition along the northern border fault related to changes of base level or relative sea level that includes tectonic movements. Facies in this depositional setting locally have dynamic range of textures, composition and relatively short-distance bed lengths commonly assigned to alluvial-fan deposits. However, recognition of cyclical brackish to marine deposits provided a stratigraphic framework that better. accommodates the reservoir-scale heterogeneity of this complex depositional system and improves the predictive models for spatial distribution of reservoir and barriers.The new stratigraphic model was used in combination with the 3-D seismic data over the Talang Akar section to better interpret spatial variations in lithology. The seismic data in the offshore northern Jatibarang sub-basin is relatively low resolution, in part a consequence of rock properties and the complex arrangement of rock types. However, amplitude maps based on a series of horizon slices from a reference reflection and lithology calibrations using seismic synthetics describe an evolution from elongate and relatively smaller lobate morphologies characteristic of low-sinuosity meanderbelts and delta complexes to predominately lobate and irregular, patchily distributed morphologies characteristic of transgressed delta deposits.