Crack based on non-linear algorithm and method for identifying fluid in crack

Abstract

The invention provides a crack based on a non-linear algorithm and a method for identifying fluid in the crack. The method provided by the invention is based on a trinomial Ruger reflection coefficient equation, and a non-linear equation containing a third member (sin<2>[theta]tan<2>[theta] member) of the Ruger equation and Thomsen anisotropic parameters are deduced out by a different position subtraction method. A non-linear algorithm-particle swarm algorithm is utilized for solving out the crack density, the Thomsen anisotropic parameters and the like from the deduced equation. A crack fluid indicating factor expression is deduced by utilizing the solved crack density and the Thomsen anisotropic parameters. In actual application, the crack density obtained on the basis of the provided non-linear equation is much closer to a theoretical value than the crack density obtained through conventional linear AVOZ inversion; anisotropic parameter values of the inversion are very close to the theoretical value; the crack fluid indicating factor obtained by using the solution of the non-linear equation is used for perfectly identifying the types of the crack fluid; and the feasibility of the method is sufficiently shown.

Description

technical field [0001] The invention belongs to the field of petroleum exploration, and relates to a method for predicting fractures and fluid types in the comprehensive evaluation of fractured reservoirs, in particular to a non-linear inversion method for fracture parameters using three Rüger equations. Background technique [0002] Fractures are not only oil and gas storage spaces, but also fluid migration channels, which can connect the scattered pore storage spaces in the reservoir. Therefore, identifying fractures and fluids in fractures is of great significance for oil and gas exploration. When fractures develop in the reservoir, they appear anisotropic to the outside. For vertically arranged parallel fractures, they can be equivalent to HTI medium (Horizontal Transverse Isotropy, that is, transversely isotropic medium with horizontal symmetry axis) model to study. Thomsen parameters are commonly used to characterize the anisotropic characteristics of HTI media (Thoms...

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Problems solved by technology

[0020] Based on the above theories, although many people have done research on how to identify fluid types in fractures, most of them are only qualitative descriptions

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