Identification of Thin-Bed Tuning and Gas Charged Reservoir Based on Seismic Spectral Decomposition
- Wei Liu (Geophysical Department under China Oil-field Services Limited) | Zheng Wang (Geophysical Department under China Oil-field Services Limited) | Siyuan Cao (State Key Laboratory of Petroleum Resource and Prospecting; University of Petroleum)
- Document ID
- World Petroleum Congress
- 20th World Petroleum Congress, 4-8 December, Doha, Qatar
- Publication Date
- Document Type
- Conference Paper
- 2011. World Petroleum Council
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- 58 since 2007
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The identification of true and false bright spots is the key of success of lithologic oil-gas reservoir exploration. The false 'bright spots' which are caused by thin-bed tuning effect are often present in post-stack seismic data. The essence of these false 'bright spots' is different from that of those real bright spots associated with gas charged reservoir. Based on petrophysical parameters of real reservoir, the geological models for wedge and thin-bed are designed, the thin-bed tuning effect is simulated, and the relations between thin-bed tuning and gas charged reservoir with frequency are studied. The result of processed marmousi?model indicates that the high amplitude caused by thin-bed tuning can be distinguished from that caused by gas charged reservoir by analyzing the differences between normalized different single frequency sections obtained by using TFCWT processing of the seismic data. This provides a new method for identification or distinguishing of true and false bright spots in post-stack seismic data. At last, the field example illustrates that this method proposed in this paper can be used to identify gas charged reservoir effectively, and it can reduce risk of lithologic oil & gas reservoir exploration and development.
With the development of oil & gas reservoir exploration, those complicated geological anomalous bodies such as lithologic reservoir, subtle reservoir, carbonatite reservoir have already become the main targets of the exploration and development nowadays (Zhang et al., 2006; Yang L, 2008). The thin interbed reservoirs will undoubtedly become the focus of exploration in the later development stage of oilfields. Therefore, the conventional geophysical techniques will encounter greater challenges in the future. Fortunately, some research results are present about thin interbeded reservoirs. Xu et al. (2006) used spectral decomposition technique to predict thin reservoir. High resolution inversion based on tuning frequency and spectral decomposition was discussed by Yang et al. (2006). Zhao et al. (2006) analyzed the impact of thin interbed tuning effect on AVO. Castagna et al. (2002, 2003 and 2005) used spectral decomposition to detect low-frequency shadows associated with hydrocarbon. However, not all of thin interbed reservoirs are the reservoirs associated with hydrocarbon. It is well known that those reservoirs associated with hydrocarbon can cause high amplitude on post-stack sections. However, the high amplitude called bright spots can be also caused by thin-bed tuning effect in post-stack seismic data (Partyka, 1999; Marfurt, 2001). If the two kinds of bright spots are present simultaneously in post-stack seismic data, the conventional geophysical techniques will not distinguish the real bright spots associated with hydrocarbon from that false bright spots relevant to thin-bed tuning because of the same seismic response.
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