Unconformity trap reservoir lithology prediction method based on prestack seismic ray impedance inversion

Abstract

The invention discloses an unconformity trap reservoir lithology prediction method based on prestack seismic ray impedance inversion. A common image point gather subjected to prestack offset is converted into a radial parameter domain from an offset distance domain; after all common image point gathers are converted, data of a constant radial parameter is extracted and the part of the data is stacked to form a co-radial parameter profile; a high precision seismic reflection coefficient sequence is acquired by iterative inversion; after a relative amplitude value on a reflection coefficient profile is converted into an actual reflection coefficient value, a generalized linear inversion algorithm is used for performing inversion on the reflection coefficient value to acquire radial wave impedance; and radial impendence capable of reflecting the characteristic that the lithology parameter changes along with frequency is used and combined with the exploratory area reservoir physical property and geologic feature to achieve lithology prediction of the unconformity trap reservoir. The radial impendence used by the method is less affected by the range of incidence angle, and the method is more applicable to the unconformity trap reservoir with strong anisotropism, large lithological changes and complex reservoir physical property, and can predict the lithology more accurately.

Description

technical field [0001] The invention belongs to geophysical exploration technology, and relates to a more reliable ray impedance inversion and lithology prediction method for describing unconformity trap reservoirs. Background technique [0002] Conventional elastic impedance inversion technology is suitable for lithology discrimination of gas-bearing sandstone reservoirs with little difference in impedance from surrounding rocks, and has high accuracy in small angle ranges. Although the elastic impedance inversion process is relatively easy to implement, key technologies such as accurate pre-stack seismic angle gather construction, mixed-phase wavelet estimation, and high-precision reflection coefficient sequence inversion often play a decisive role in the inversion results. In addition, the application of actual data shows that when elastic impedance inversion is used to predict the lithology of oil and gas reservoirs with strong heterogeneity and complex reservoir physica...

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Problems solved by technology

In addition, the application of actual data shows that when elastic impedance inversion is used to predict the lithology of oil and gas reservoirs with strong heterogeneity and complex reservoir physical properties, it often faces problems such as drastic changes in values ​​with angles, insufficient accuracy in the range of large incident angles, and poor prediction accuracy. The results are sensitive to inherent parameters (ratio of shear wave to longitudinal wave velocity) etc.

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