An Improved Frequency-dependent AVO Inversion Method and Its Application for Fluid Detection

Sun, Shao-Han; Yue, Hangyu; Hu, Liguo; Zhang, Y.; Wang, J.; Peng, Lingli; Du, Tao; Peng, Tishun

doi:10.3997/2214-4609.20141313

Cited by 2 publications

(1 citation statement)

References 2 publications

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“…It also can reveal the occurrence state and distribution rules of subsurface fluid more intuitively and can promote the matching ratio of dissolution reservoir and fluid prediction to more than 15% (Sun et al, 2014).…”

Section: Key Issuesmentioning

confidence: 99%

Carbonate reservoirs dominated by secondary storage space: Key issues and technical strategy

et al. 2015

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Carbonate reservoirs of the Tarim Basin in China are buried deeply, with strong later diagenesis, and seldom are controlled by geologic facies. The effective storage spaces are mainly dissolution caves and fractures with few primary pores. Fluid distribution in the reservoir is extremely complicated. All these characteristics make it a world-class challenge for oil and gas exploration and production. Conventional poststack methods ignore the complexity of the reservoir medium with low accuracy of prediction results, by which the location of the dissolution cave is determined roughly. Only faults and fracture zones can be described to a certain degree instead of quantifying the fracture detection. Aiming at the key problems of the complex carbonate reservoirs in the Tarim Basin, a series of techniques has been developed to improve the successful rate of reservoir prediction, including the following aspects: the wide-azimuth and high-density data-acquisition technique to improve the quality of the original seismic data; a series of migration techniques including prestack reverse time migration; and amplitude-preserved Q migration to improve the quality of seismic gathers and the imaging precision with the matching precision of AVO gathers. The target reservoir data dominant frequency increased by more than 15% and by nearly 20 Hz. In addition, the effective DEM-Gassmann rock-physics model is proposed for velocity prediction, by which relative error of estimated shearwave velocity reaches to less than 5%. Furthermore, an advanced inversion algorithm is introduced to improve the accuracy of extracted elastic information. By using new prestack inversion and frequency-dependent AVO inversion, the tie rate of the dissolution-cave reservoir and fluid prediction increased by more than 15%. Furthermore, the fracture-prediction tie rate can be enhanced by 20% through limited-azimuth anisotropic inversion, on the basis of which the quantitative identification of fracture fluid for actual seismic data can be realized.

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Section: Key Issuesmentioning

confidence: 99%

Carbonate reservoirs dominated by secondary storage space: Key issues and technical strategy

et al. 2015

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Hydrocarbon detection for Ordovician carbonate reservoir using amplitude variation with offset and spectral decomposition

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Wang³

et al. 2016

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We have developed an example of hydrocarbon detection for an Ordovician cavern carbonate reservoir in western China with a burial depth exceeding 6600 m using amplitude variation with offset (AVO) and spectral decomposition. We selected six production wells, three prolific oil wells, and three brine wells to test the hydrocarbon detection method. The three oil wells have been producing for more than three years, and the three water wells only produce brine. We performed spectral decomposition to the angle gathers and analyzed amplitude variation patterns with incidence angles for different spectral components. Specifically, we compared the time corresponding to the peak spectral amplitude for different spectral components for the oil- and brine-saturated carbonate reservoirs. The main findings are as follows: (1) Oil-saturated cavern carbonate reservoirs show decreasing peak time with increasing frequency; i.e., the high-frequency components travel faster than do the low-frequency components. The maximum time difference between the 10 and 50 Hz spectral components could reach 35 ms. In contrast, the brine-saturated carbonate reservoirs do not exhibit conspicuous variation in the peak time, (2) AVO attributes extracted from the low-frequency spectral gathers are more robust than those extracted from the original seismic gathers, (3) oil-saturated cavern carbonate reservoirs cause strong energies in the low-frequency spectral components and severe attenuation to the high-frequency spectral components at large incidence angles. In contrast, the brine-saturated carbonate reservoirs do not produce such phenomenon. Rock physics analysis for carbonate reservoirs under different saturation conditions was conducted. The synthetic gathers were generated for carbonate reservoirs under oil- and brine-saturated conditions. The spectrally decomposed synthetic gathers are in agreement with the real gathers. The results indicate that AVO analysis of spectrally decomposed prestack gathers could be used as an effective hydrocarbon detection method for carbonate reservoirs.

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An Improved Frequency-dependent AVO Inversion Method and Its Application for Fluid Detection

Cited by 2 publications

References 2 publications

Carbonate reservoirs dominated by secondary storage space: Key issues and technical strategy

Carbonate reservoirs dominated by secondary storage space: Key issues and technical strategy

Hydrocarbon detection for Ordovician carbonate reservoir using amplitude variation with offset and spectral decomposition

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