Abstract
The organic reef is a special type of carbonate reservoir which always dominates the spatial distribution, reserves and accumulations of natural gas. However, it is difficult to determine the organic reef’s internal structure and gas reservoirs due to numerous adverse factors such as the low resolution of seismic data, depth of burial, strong anisotropy, irregular spatial distribution and complex internal structure. A case study of wavelet decomposition and reconstruction technology applied to elucidate the features of organic reef reservoirs in the Changxing formation from Yuanba gas field shows that the seismic record reconstructed by high frequency signal can adequately describe the internal properties of organic reef reservoirs. Furthermore, the root mean square amplitude ratio of both low and high frequency data obtained from the reconstructed seismic data clearly show spatial distribution of gas and water in reef reservoirs.
Highlights
Marine carbonate reservoirs are widely distributed in China
The growth scale and distribution of reef reservoirs are mainly controlled by carbonate sedimentary facies in the Changxing formation in Yuanba gas field (Ma et al 2007, Bi et al 2007)
In the reef reservoirs of Changxing formation in Yuanba gas field, the reef body is generally composed of reef base, reef core, and reef cap (Cai 2011)
Summary
Marine carbonate reservoirs are widely distributed in China. these carbonate reservoirs are deeply buried, and there is strong vertical and horizontal heterogeneity, which contribute to increased difficulty in hydrocarbon detection. Many geophysicists are optimistic about the use of the time-frequent seismic signal, which probes the response characteristics in both time and frequency domains (Castagna et al 2003, Cohen 1995) Most of their search has focused on the frequency, energy, amplitude, and attenuation properties ascertained through time-frequency analysis to obtain the low-frequency shallows and high-frequency attenuation of the gas reservoirs rather than to reconstruct seismograms in different frequencies (Burnett et al 2003, Reine et al 2009, Xu et al 2011, Xue et al 2013). Since these wavelets’ attributes are closely related to geologic features and the properties of reservoirs, the method reconstructs the atoms in terms of the information associated with the gas reservoirs, with certain targeted objectives in mind, and a new seismic trace can be reconstructed with a selected subset of wavelets, which is found to be highly informative for seismic data interpretation and reservoir characterization (An 2006)
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