Publications

The Dayung field is a major gas reservoir located in the Corridor block in South Sumatera. The field produces from various reservoir facies including sandstone and Pre-Tertiary (PRT) Basement, consist of marble, limestone, hydrothermally altered granite, granite breccia, and granite wash. Three years after the field was put on production in 1998, water was breakthrough at a flank well. Subsequently the second and the third well which are located also at the flank, started to water out either. However, as production continued, some additional wells were breakthrough from location that appeared to be in a random fashion. Understanding this complex water breakthrough behavior is critical to predict future field performance. To get more insight into the water behavior of the field, a comprehensive, multi-year reservoir surveillance program was put in place. The program included the measurement of water rates, water salinity sampling, PLT data, tracer injection and pressure surveillance. Tests were taken regularly and actively analyzed to obtain the information regarding the movement of the gas-water-contact in the reservoir. Based on the data collected, a dynamic model has been built. The model integrates surveillance data with geologic information and resulted in a history match which explains the apparent complex water breakthrough behavior through a simple single gaswater contact interpretation. The dynamic model also provided insight into the distribution of fracture density (and therefore gas) in the system. This paper will describe the comprehensive reservoir surveillance program and the interpretation of the collected data. It will discuss how the data was used to build and history match the dynamic model, and the geologic insights gained. It will also discuss the lessons learned about the management of fractured basement gas reservoir with water influx, including gas and water management, and the long-term production strategy optimization.