In-situ Permeability Estimation:
A Comparison between Acoustic and NMR Logs
by
Wei Chen
Submitted
to the Department of Earth, Atmospheric, and Planetary Sciences on January 1999
in partial fulfillment of the requirements for the
degree of Master of Science
ABSTRACT
The estimation of formation permeability from full waveform acoustic and
nuclear magnetic resonance (NMR) logs in petroleum well logging has improved
significantly in recent years. In this thesis, we review the methods of permeability
estimation from Stoneley waves and provide permeability comparisons between
acoustic and NMR logs. When a Stoneley wave travels along a permeable formation,
hydraulic exchange between the Stoneley wave and formation will occur. As
a result, Stoneley wave travel time will be delayed and the Stoneley wave
attenuation will increase, causing a centroid frequency shift. Therefore,
these two wave attributes can be used to estimate formation permeability.
NMR logging data can also be used to estimate permeability. Permeability estimates
using Stoneley waves and NMR logging were tested using data from a section
consisting of sandstone and shale beds. The permeability results show very
good correlation for these two different methods. Data from a gas zone that
is analyzed shows high permeability values from acoustic data and low values
from NMR. The difference between these two permeability results can be used
as a gas zone indicator.
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April, 1999
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