Method for acquiring stratum rock brittleness property through radial change of borehole elastic wave velocity

Abstract

The invention discloses a method for acquiring stratum rock brittleness property through radial change of the borehole elastic wave velocity. The method comprises following steps: performing well logging in a depth interval to obtain full wave data when monopoles and dipoles in the depth interval are triggered as well as a stratum density curve respectively; obtaining the longitudinal wave velocity vp and the transverse wave velocity vs of the stratum; calculating travel time of waves of N receivers according to the longitudinal wave velocity; extracting a longitudinal wave arrival time curve changing with the depth, and defining the longitudinal wave arrival time curve as an actually measured longitudinal wave travel time curve; obtaining a radial profile of the longitudinal wave velocity of the stratum; minimizing an objective function to obtain change of a radial velocity of the transverse wave; obtaining a radial profile of the stratum transverse wave velocity continuously changing in the depth interval; and obtaining a brittle fracture index of the stratum through integral of the velocity and the radial distance according to obtained radial change of the longitudinal wave velocity and the transverse wave velocity of the borehole wall rock, and indicating brittleness and cleavability of the rock by comparing the index change. With the adoption of the method, the technical problems about effective evaluation of current situation of rock cleavability and the like can be solved.

Description

technical field [0001] The invention belongs to the technical field of geophysical well logging and its application in oil and natural gas fracturing, and relates to a petrophysical theory and an acoustic logging processing method, in particular to a technology for extracting the radial variation of well logging wave velocity and analyzing it. A method for assessing the brittle and fractured nature of formation rocks associated with fracking. Background technique [0002] The practice of fracturing production of unconventional oil and gas has proved that the brittleness and crackability of formation rocks are the key factors controlling the fracturing effect. In the well-brittle loaded rock, when the applied load exceeds the fracture strength of the rock, the rock will crack immediately and the expansion of the crack does not require additional energy. Relatively speaking, rocks with poor brittleness undergo plastic yielding, and fracture initiation needs to continue to abs...

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to provide a method for obtaining the brittleness of formation rock from the radial change of elastic wave velocity in the well, so as to comprehensively estimate the brittleness and crackability of the rock by solving the change of wave velocity produced by the rock near the well wall during the drilling process , effectively evaluating the status quo of rock fracturing and other technical issues

Images