Publications

Challenges and lessons learned can be unique for different carbonate reservoirs. In Rawa carbonate reservoir, one of the main challenges is how to quantitatively translate the complexity of secondary porosity observed in core and image logs to well and field performance. Other challenges are how to model reservoir performance and eventually produce a reliable dynamic model given the subsurface uncertainties for forecasting purposes. This paper presents an approach and workflow to tackle those challenges by areal history matching. Rawa carbonate reservoir has been penetrated by vertical and horizontal wells. Structurally, the field consists of two culminations, northern and southern, separated by a saddle. The culminations consist of reef carbonate facies and the flanks by platform carbonates. Pressure data analysis suggests the entire field is in pressure communication but different production behaviors have been observed in different areas. Water and gas breakthrough in the North and South areas show differences as a function of structure, reservoir property variation, and aquifer size. To achieve a history match, the full field reservoir simulation model was divided into different areas based on the observed production behavior and then history matching was done within each of those areas. Uniqueness and connectivity between areas are valuable information for history matching strategy. In Rawa field, the strategy was divided into two stages. Stage 1 included history matching of field production rate and reservoir pressure. Material balance analysis was also performed to diagnose drive mechanisms and total volume. Stage 2 included data analysis for well performance behaviors and areal history matching which was applied to areas with different production behaviors. Focused well history match was performed only if required. The use of this history matching workflow in Rawa field has improved speed and accuracy of the history match through prevention of time-consuming and redundant iterative work in typical history matching. The process has also resulted in new development and production optimization opportunities in Rawa field.