Characterizing tight sand gas reservoirs using 3D3C seismic data in Sulige gas field

Abstract

The Sulige is the largest discovered gas field in China. The reservoir is characterized by low porosity, low permeability and strong heterogeneity. Meanwhile single sand body is superimposed each other and the composite sand bodies are contiguous, whereas the distribution of gas reservoirs is dispersed. Consequently, traditional method for sand body prediction is difficult to meet the need for gas reservoir prediction that is the one of key problems of reservoir prediction in Sulige area. P-wave seismic technology has played an important role in exploration and development of Sulige gas field. But with the expanding edge of exploration and the fineness of development, using PP seismic data alone has shortcoming for the prediction of effective thin reservoir and spatial distribution of gas and water reservoirs. Beginning with the first full digital 3D3C seismic data acquisition in Sulige area in 2003, it gradually sets up a work flow and related methods of using multicomponent seismic data to identify gas reservoir. In this paper, we present a practical application of using 3D3C seismic data. Considering the feature of tight gas reservoir in Sulige area, characteristics of rock physics parameters being sensitive to gas reservoir are set up on the basis of rock physics analysis. Through the co-analysis of seismic modeling and joint PP/PS pre-stack inversion, elastic parameters including P-impedance, S-impedance and Vp/Vs ratio etc are got from joint PP/PS pre-stack inversion. Finally, the methods of elastic parameters crossplot and facies/fluid probability analysis are employed to interpret the inversion result, thus improving the accuracy of gas reservoir prediction.