Abstract:

In order to solve the problem of sedimentary cycle recognition of the middleshallow sandbodies in the northern Chexi Subsag, we proposed a geologic and seismicconstrained sedimentary cycle description method by using the Milankovitch cycle theory and wavelet transformation with well logging, constrained. Spectrum analysis of well logs shows that sedimentary cycle of sandbodies in Dongying Formation in the northern Chexi Subsag was controlled by the Milankovitch cycle. The fourth and fifthorder sequences were controlled by the cycle of 4040 ka eccentricity and 536 ka dip of earth’s axis, which is the foundation of the division and correlation of sandbody sedimentary cycle. According to the theories of Milankovitch cycle and wavelet transformation, we identified 8-10 small sedimentary fans vertically in the sandbodies of the Dongying Formation in the northern Chexi Subsag. The results show that analyses of high frequency cycles by using the Milankovitch cycle and wavelet transform can improve the quantificational level of sedimentary cycle division. The designed curves of Milankovitch cycle filters and the selected wavelet transformation coefficients correlate well with the high frequency cycles, and thus can be used to effectively recognize sedimentary cycles of sandbodies.

Key words:  , Key words： sandbody, high frequency cycle, Milankovitch cycle, wavelet transformation, continental rifted basin, Chexi Subsag, Jiyang Depression