Publications

Non-matrix features (karst and fractures) can have a significant impact in hydrocarbon bearing carbonate reservoirs on in-place volumes, recovery factor, and reservoir performance. The Banyu Urip field, currently the largest contributor to Indonesia; oil production, has multiple lines of evidence for the presence of non-matrix including drilling data, wellbore images, wireline logs, seismic and field performance. The question now is whether we can characterize the size and density of the non-matrix features in the field and be predictive about where those features are located vertically and laterally across the field. Here we present a novel approach to non-matrix characterization by integrating a complete set of data from 46 wells, including the drilling data, image, wireline logs, dynamic data (PLT, well tests) and a newly reprocessed 3D seismic volume. Wells drilled throughout the exploration and development phases of Banyu Urip experienced frequent lost circulation events. By integrating lost circulation zones (LCZs) with image and wireline logs, we found that most of the LCZs are related to non-matrix features. The amount of fluids lost to these features can be significant (up to 20,000 bbls) which suggest they are volumetrically relevant features and have a potential impact on in-place volumes. A significant number of karst features were observed. Penetrated karst ranged in height with an average of 1.5 m accumulate near the sequence boundaries. Integration with the seismic data revealed that some of the karst features have a seismically detectable response (geobody). These seismic geobodies allow us to get a sense of karst density and distribution away from well control. Well and seismic data, in combination with a paleo-topography reconstruction, suggest that there is a higher likelihood of having karst in the vicinity of the paleo-highs, the old reefs. This approach has provided the technical basis for re-assessing in-place volumes and excess permeability in Banyu Urip. Early results support an increase in hydrocarbon pore volume and has had a direct impact on reservoir surveillance, performance, and simulation strategies.