APPLICATION OF RESERVOIR PREDICTION TECHNIQUE IN ROLL EXPLORATION IN GUANG'AN AREA

Guangan area in the central Sichuan is a seismic exploration block with rich experiences, previous seismic exploration results indicate that gas reservoir of Xujiahe formation in the upper Triassic belongs to lithologic and structural-lithologic complex gas reservoir, and the reservoir is characterized by low porosity, low permeability and strong heterogeneity laterally and vertically. The drilling successful rate is not high though gas is accumulated in this area, and no breakthrough has been made in a long time, so roll explorations were performed on the basis of joint-patches seismic data processing and interpretation in 2004. According to high resolution sequence stratigraphy theory, strata correlation, division and seismic facies analysis were performed, and sedimentary facies zones and favorable prospects zones were delineated in T3x4 and T3x6L. Moreover, we summarized the logging and seismic response patterns of the effective reservoirs in the pay formation, including sandstone layers in T3x6 and T3x4, and applied poststack seismic attribute analysis and high precision inversion technique which is aimed at thin interbedding reservoirs to predict the effective reservoir distribution rule in T3x4 and T3x6L. There were 8 cycles of poststack reservoir inversion and fine interpretation performed to meet the requirements for the roll exploration. Up to April, 2007, 31 wells were drilled on the basis of the prediction results, among them, 10 wells encountered commercial gas in T3x6, and 14 wells encountered commercial gas in T3x4, which confirmed the validity of the foresaid methods, and developed a set of match techniques and ideas for reservoir prediction of Xujiahe formation.