Inversion method of stratum shear wave velocity radial sections

Abstract

The invention relates to an inversion method of stratum shear wave velocity radial sections. The inversion method includes: performing acoustic logging while drilling and while drilling stratum density and well diameter logging in a depth interval, and obtaining while drilling monopole and quadrupole array acoustic full wave train data, a while drilling stratum density logging curve and a while drilling well diameter logging curve; obtaining stratum longitudinal wave velocity and shear wave velocity at the position of processing depth through calculation, and extracting phase velocity frequency dispersion data of while drilling quadrupole wave; calculating a theoretical while drilling quadrupole wave frequency dispersion curve at the position of the processing depth; constructing an inversion objective function in a combined mode; outputting equivalent alteration velocity and thickness; calculating continuously variable stratum shear wave velocity radial sections; and repeating the steps until processing of the whole depth interval is finished, and obtaining the stratum shear wave velocity radial sections changing continuously along with logging depth. The inversion method of stratum shear wave velocity radial sections has the advantages of obtaining changes of mechanics / acoustic parameters nearby a well in real time, solving the problem of ununiqueness of inversion, and improving reliability of inversion results.

Description

technical field [0001] The invention belongs to the field of applied geophysical acoustic well logging, and in particular relates to a method for inverting the radial profile of formation shear wave velocity. Under the condition of acoustic logging while drilling, the radial change profile of formation shear wave velocity is inverted by using the dispersion curve of quadrupole mode wave while drilling. Background technique [0002] Due to ground stress, mud invasion and mechanical damage caused by drilling, etc., the mechanical / acoustic parameters of the formation near the wellbore can change, such as the radial change of the formation shear wave velocity. Determining the change of formation radial properties is very important for evaluating wellbore stability, estimating in-situ stress and optimizing reservoir production. [0003] So far, all inversion techniques of formation radial velocity variation profile are aimed at wireline acoustic logging. Sinha et al. (Sinha B.K...

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Problems solved by technology

[0004] 1. Due to the high cost and high risk of wireline logging in highly deviated wells, horizontal wells, and deep-sea drilling, the use of high-end dipole shear wave logging tools is severely restricted, and formation shear wave velocity profiles cannot be obtained

[0005] 2. Wireline logging is greatly affected by mud invasion, and the formation shear wave velocity profile inverted by cable dipole bending wave cannot truly reflect the original state of the formation

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