Digital Point Receiver Seismic Acquisition and Pre-stack Reservoir Characterization at Sulige Gas Field, China

Sulige gas field (Ordos basin, Inner Mongolia) is the largest onshore gas field in China with proven gas reserves of 1.1 trillion cubic meters. This thin multi-layered deltaic reservoir of lower Permian age is very heterogeneous which prevents development drilling from high success rate (less than 60%). With respect to these characteristics and to the depth of the reservoir (3000 m), an improvement in surface seismic was mandatory more efficiently detect the sweet spots. This has been accomplished using point source - point receiver dense 2D acquisition based on explosive and digital 1C MEMS accelerometers. Data processing as well was revisited to better preserve amplitude of the CDP gathers used as input of pre-stack inversion and AVO analysis. Digital sensors proved to be more effective in preserving far offset amplitude than the conventional arrays of geophones. The resulting lithological and gas content predictions, confirmed by 30 new wells, demonstrate their effectiveness in delineating sweet spots. Success have improved by 50% and Sulige gas field has now tripled its natural gas output capacity, helping PetroChina to meet surging domestic energy demand: the field’s annual capacity reached 4 billion cubic meters by end 2007 from 1.3 billion the previous year.