Method and system for inverting elastic parameters of multi-wave AVO reservoir based on reflectivity method

Abstract

The invention provides method and system for inverting elastic parameters of multi-wave AVO reservoir based on the reflectivity method. The method comprises the steps of acquiring a seismic prestack gather, log data and an actual seismic gather of an angle area beside the well; determining seismic wavelet and amplitude extension factors according to the eismic prestack gather, the log data and the actual seismic gather of the angle area beside the well; acquiring statistical model parameters of the log data; determining model parameter prior distribution functions meeting the working area according to the statistical model parameters; acquiring seismotectonics interpreting data; building an initial elastic parameter model of a depth area according to the seismotectonics interpreting data and the log data; determining inversion residuals of PP wave and PS wave according to the initial elastic parameter model; creating the inversion target function under the maximum posterior probability significance; determining an optimal elastic parameter model according to the inversion target function and the inversion residuals of PP wave and PS wave. According to the scheme, the method meets the requirements on inversing to recognize the characterization of a seismic prestack oil and gas reservoir, in particular a shale gas reservoir.

Description

Technical field [0001] The present invention relates to the field of geophysical exploration technology, especially to the processing technology of oil and gas fields, shale gas seismic exploration and reservoir parameters. Specifically, it is a method and system for inversion of elastic parameters of multi-wave AVO reservoirs based on reflectivity method . Background technique [0002] Seismic inversion is an effective method to obtain internal images of underground media and to finely describe the reservoir. It is also the final form of high-resolution seismic exploration. Seismic data inversion greatly improves the value of reservoir characterization. [0003] As the focus of seismic research gradually shifts from exploration to development, from conventional oil and gas to unconventional oil and gas, especially shale gas, seismic inversion and other methods are used to reveal the fine distribution characteristics of underground oil and gas reservoirs to refine the oil and gas r...

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Problems solved by technology

[0006] 1. The traditional pre-stack AVO inversion method generally only considers P-wave PP wave data. PP-wave data mainly contains P-wave velocity information, but is not sensitive to model velocity and density. Using PP seismic AVO data alone to invert S-wave velocity information and density has a large uncertainty

[0007] 2. There is a large difference in travel time between PP wave and shear wave PS wave, and it is difficult to match time

[0008] 3. The accuracy of the amplitude is very critical for pre-stack inversion, but the traditional pre-stack AVO inversion does not consider the transmission loss and other wave propagation effects, so the amplitude of the simulated data at deep positions does not match the actual

[0009] 4. The most common structure of oil and gas reservoirs, especially shale gas reservoirs, is the thin interbedded structure of shale and sandstone. Under such geological conditions, interlayer multiple waves develop, and the reflected waves of each layer interfere and superimpose each other, which greatly changes the The AVO inversion method based on the Zoeppritz equation or its approximate expression is no longer suitable for this kind of reservoir because of the pre-stack AVO response characteristics

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