A large carbonate gas field in the Central Luconia geological province, offshore Sarawak, Malaysia, is being operated by Sarawak Shell Berhad (SSB) and partners Petronas Carigali and Nippon Oil.
After more than 8 years of production, a full understanding of the field is required to assess near-term WRFM opportunities and to evaluate the remaining future development potential. The aims are to ensure the delivery of gas at a sustained level of gas volumes and with a manageable water level and at the same time improving the ultimate hydrocarbon gas recovery.
Predicting and preventing water breakthrough at the existing producers currently forms the challenge for the WRFM.
To deal with the above challenges and opportunities, the integrated methodologies employed include:
Reservoir surveillance through timely data acquisition of fluid movement measurement in the observation well and time-lapse (4D) seismic, i.e. monitoring contact movement
Together with the historical well performance, a continuous integrated subsurface-surface study is performed with the aims to improve the field hydrocarbon gas recovery through optimization of WRFM, reservoir models, in-fill identification and near future field development
Continued optimization between subsurface and surface facilities
A reservoir surveillance program has been in place since first gas with one of the deviated wells being dedicated to monitor the fluid contacts on a yearly basis. To complement this, two time-lapse (4D) seismic surveys have been successfully acquired in 2008 and 2012 to provide a field wide image of fluid movements and contacts. In spite of only two narrow swaths acquired around the platform area, the 2008 4D seismic has assisted in drilling two in-fill producers granting production to maintain a constant level. In 2012, a much larger 4D swaths were acquired covering the majority of the field. The high quality 4D data provides more crucial information, including indication that gas has likely been produced from a much wider area including the southern area.
The two 4D time lapse data enable to constrain the dynamic (and also static) modeling significantly and monitoring the dynamic behavior of different reservoir geobodies (reef margins, karst, faults) through production lifetime of the reservoir units.
