Publications

Reservoir modeling efforts were initiated to optimize reservoir management and field development of Kotabatak Field, Central Sumatra. This reservoir characterization project has yielded important new insights into the distribution of reservoir facies and will contribute significantly to the recovery of hydrocarbons in this field.Sequence stratigraphic correlations, core studies, log analysis and facies mapping were integrated with production and injection plots to accomplish this characterization. The study has identified two distinct areas that exhibit significantly different reservoir characteristics (channelized and non-channelized lithofacies). The channel systems are a stacked complex of estuarine and intertidal lithofacies which occur mainly in the northwestern part of Kotabatak Field. These channelized reservoirs have an average permeability of 800 md, while the non-channelized lithofacies, which are thicker and more continuous, have an average permeability of less than 100 md.The reservoir characterization project at Kotabatak has added significant value by focusing EOR activity on areas with the highest potential. Prior to the current study, Caltex Pacific Indonesia (CPI) had planned to implement a field-wide pattern waterflood. However, in order to increase the value of the waterflood project and to reduce the associated risks, it was decided to implement a phmed pattern waterflood project using a ",high-grade", approach. The selection of this ",highgrade", area was based on criteria which include: reservoir continuity, vertical heterogeneity, facies distribution, reservoir pressure, potential remaining oil, production decline, and water cut variation.By utilizing all geological and engineering data, we were able to develop a geologic model that explains known anomalies in production and provides a sound basis for field management decisions. This effort clearly shows that for a complex field such as Kotabatak, no single reservoir management strategy can be applied field-wide.