Abstract：In the depletion exploitation process for the gas field only the reservoir pore pressure was generally decreased,leading to the weak 4D seismic effect,which restricts the application of 4D seismic technology in the exploitation management of the gas field. Regarding the difficult problem,two 3D seismic surveys in large gas field A in South China Sea were utilized to conduct 4D seismic monitoring test. Based on the detailed modeling studies,fine consistent amplitude compensation and careful selection of seismic parameters,it was found that some amplitude attribute for the top of the reservoir decreased 5 percent after 5 years of exploitation,showing the existence of 4D seismic effect for the depletion exploitation gas field. Therefore 4D seismic technique can be used to monitor the production performance of the oilgas reservoir,and provide basis for oilgas field development deployment.
