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The disturbance of drilling mud on rock formation and a method for error elimination on acoustic log curves
Author(s) -
Wei Changjiang,
Li Jianjun,
Liu Baohua,
Xu Shizhe
Publication year - 2003
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1046/j.1365-2478.2003.00387.x
Subject(s) - geology , seismogram , well logging , sonic logging , interval (graph theory) , logging while drilling , transmitter , drilling , acoustics , transit time , seismology , computer science , geophysics , mathematics , materials science , telecommunications , physics , channel (broadcasting) , combinatorics , transport engineering , engineering , metallurgy
Errors in acoustic logs have a significant influence on the assessment of formations, the description of oil deposits and modelling using synthetic seismograms. The elimination of these errors is a problem that many researchers have been trying to solve for many years. We derive theoretical formulae for calculating the radial depth of investigation of acoustic logging, and analyse the relationship between the error in acoustic interval transit time and the altered zone thickness. We explain in detail how mud affects the acoustic interval transit time. We also describe the variation of altered zone thickness with time and a method for calculating the altered zone thickness. Finally, we present a set of new methods that can be directly applied to correct the disturbing influence on acoustic curves. Our results are obtained based on the fact that acoustic velocities in the altered zone show a small lateral variation. Examples are given of analysing the acoustic log data, which are collected from a BS well at three different times. This paper is significant both for selection of the acoustic logging device with proper transmitter‐to‐receiver distance (spacing) and improvement of the device.