ION MALUREANU
I. P. G. Ploiesti
THE INFLUENCE OF INVASION DIAMETER ON AMPLITUDE
OF SPONTANEOUS PONTENTIAL (SP) CURVE
(Abstract)
The qualitative and quantitative evaluation of invasion zone influence of
SP curve are studied in the paper.
In the interpretation of SP logs, the physical model used assumes the presence
of double-electric layers on the borehole-formations limit, and, also, at the
limits of porous-permeable rocks with surrounding formations.
Due to mud filtrate invasion of reservoir rocks, the double-electric layers
formed by diffusion-adsorption processes are dependent of the invasion zone
diameter, with a direct influence on record SP values.
The paper includes: physical model description, evaluation of point measuring
electrode potential M located on the borehole axis in the presence of the invasion,
correction coefficient of recorded SP, practical applications and conclusions.
From the analysis made in the paper there results that mud filtrate invasion
affects both amplitude and configuration of SP curve. So, recorded SP curve
must be corrected for the invasion diameter influence. Both analytical formulae
and SP correction plot are presented in the paper, with direct practical implications
for the correct interpretation of SP logs.
Key words: Spontaneous Potential (SP), invasion zone diameter.