Shale gas identification method based on fluid inversion of pre-stack precise equation of fastest step-down

Abstract

The invention discloses a shale gas identification method based on deepest descent prestack precise equation fluid inversion. The method is characterized in that an objective function based on fluid identification parameters is constructed through the Zoeppritz equation and a porous medium rock-physics model, and an iterative equation is obtained through deduction and inversion. The method has theadvantages that prestack inversion is directly carried out through the Zoeppritz equation, so that limitations for small angles caused by a Zoeppritz approximate expression can be avoided, and large-angle seismic materials can be better utilized; through the deepest descent algorithm, the convergence efficiency can be improved, and the calculation load can be reduced; and the deepest descent inversion is carried out through the non-simplified Zoeppritz equation, so that estimated values of the fluid identification parameters can be accurately and rapidly obtained, and a more reliable basis can be further provided for shale gas identification.

Description

technical field [0001] The invention discloses a shale gas identification method based on the fluid inversion of the pre-stack precise equation of the fastest step-down, and belongs to the technical field of oil and gas exploration. Background technique [0002] Although the usual post-stack seismic inversion technology can solve the problem of spatial distribution of reservoirs under certain conditions, it is obviously insufficient for the prediction and description of complex oil and gas reservoirs with thin vertical thickness and large lateral changes. The seismic data obtained after stacking will make the AVO characteristic of reflected wave amplitude disappear, and may also cause many artifacts in amplitude interpretation; the rich amplitude and travel time information contained in pre-stack data and some subtle stratigraphic features will be weakened and disappeared, especially But when the thickness of the reservoir itself is much smaller than the seismic resolution a...

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Problems solved by technology

[0016] Disadvantages of prior art 1: post-stack inversion method theory and practical application are very mature, although under certain geological conditions, post-stack inversion can solve the problem of lateral prediction of reservoirs, but it also has certain limitations :

Considering that pre-stack seismic inversion is the main method to extract basic elastic parameters, the reliability of elastic parameters can be improved by improving the inversion method; in addition, affected by the inherent uncertainties such as "ill-conditioned solutions" of seismic inverse problems, based on Indirectly combined fluid factors inevitably lead to cumulative errors

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