Prediction of Triassic gypsum cap rocks in Tongnanba region of Northeast Sichuan Basin

Based on detailed stratigraphic correlation,gypsum-salt rock petrophysical analyses and forward mo-deling,it was identified in this paper the seismic response characteristics of gypsum-salt cap rocks in Tongnanba region of the Northeast Sichuan Basin.With neural network seismic facies analysis method,the beneficial facies distribution of cap rocks was figured out.Using 3-D seismic attribute analysis,wavelet frequency interpretation and density inversion technologies,a set of prediction method suitable for the gypsum-salt cap rocks in the region was proposed.The relationship between cap rocks and petroleum in the region was analyzed.There were 3 suits of gypsum-salt cap rocks in the region,among which the gypsum-salt cap rocks from the 4th,5th Members of the Jialingjiang Formation to the 1st Member of the Leikoupo Formation were the best beneficial regional cap rocks due to big thickness,well crawling and self-sealing to faults;however,the sealing conditions were affected by fault activities.Fault activities increased from south to north,resulting in more risks for fault-sealing in the north.