TITLE:
Prediction of Tight Sand Reservoir with Multi-Wavelet Decomposition and Reconstructing Method
AUTHORS:
Lifang Cheng, Yanchun Wang, Zhiguo Li, Fuxiu Gong
KEYWORDS:
Morlet Wavelet, Matching Pursuit, Decomposition and Reconstruction, Tight Sandstone, Reservoir Prediction
JOURNAL NAME:
International Journal of Geosciences,
Vol.7 No.4,
April
25,
2016
ABSTRACT: Special reservoir or fluid
has an abnormal response to some certain frequencies, so that seismic
decomposition and reconstruction are used to highlight the seismic reflection
at certain frequencies useful to identify special geological bodies. Because seismic
wavelets are time-varying and spatial-variable in the propagation, synthetic
traces based on single wavelet make some weak but useful information lost, and
make artifacts form. However, Morlet wavelet aggregation with mathematical
analytical expression is able to fully and correctly reflect the variations of
wavelet in the propagation of underground medium. The matching pursuit
algorithm on the basis of Morlet wavelet improves the calculating efficiency in
decomposition and reconstruction greatly. This method is applied to the actual
study area to do conjoint analysis of single well and well-tie multi-wavelet
decomposition. It is found that frequencies sensitive to interest reservoirs
range from 8 to 34 Hz. Reconstructing the wavelets at those special frequencies
and analyzing the reconstructed seismic data, it is pointed out that interest
reservoirs have abnormal characteristics with respectively strong RMS amplitude
in the reconstructed data. Crossplot of gamma value at wells and reconstructed
RMS amplitude suggests that anomalies caused by interest reservoirs are well
separated from the background anomalies when the reconstructed RMS amplitude is
greater than 3650. Quantitative prediction results of interest reservoirs
distribution in the study area reveal that interest reservoirs of western and
northern study area are distributed annularly and bandedly, while most
contiguous sandstone in eastern regions appears sporadically.