Abstract

Application of integrated sequence stratigraphic techniques, utilizing detailed well log correlations, biostratigraphic data, core descriptions and seismic data, has resulted in a new stratigraphic framework for the Upper Talang Akar Formation in the Offshore Northwest Java (ONWJ) PSC. The Upper Talang Akar Formation comprises non-marine to deltaic and marginal marine sediments deposited during the Upper Oligocene to Lower Miocene. The studied interval is approximately 1000 feet of interbedded shale, limestone, coal, and sandstone deposited in an overall transgressive sequence. The traditional stratigraphic framework, which was based strictly on lithostratigraphic correlation of similar depositional fades, has proven inadequate to address many correlation problems on field and basin-wide scales. New stratigraphic correlations, based on integrated sequence stratigraphic techniques, have aided in the identification of specific chronostratigraphic intervals and depositional settings which contain most of the major oil and gas reservoirs discovered within the formation.

The key to this technique was the identification and correlation of regionally-extensive flooding events and their associated surfaces on a well to well basis. On the basis of these flooding events, several major sedimentary cycles were identified. Core data were used to interpret depositional environments and to subdivide the sedimentary cycles into sequence systems tracts. Well log correlations on a basin-wide scale, integrated with biostratigraphic and seismic data, were used to construct the sequence stratigraphy model for the central ONWJ area.

The establishment of an Upper Talang Akar sequence framework was critical in determining the stratigraphic controls on hydrocarbon accumulations within this formation, as well as the identification of undrilled stratigraphic plays in the basin. Utilization of similar techniques could provide an alternative method for chronostratigraphic and lithostratigraphic correlations and mapping in similar non-marine to marginal marine sediments throughout Indonesia.