View
222
Download
0
Category
Preview:
Citation preview
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 1/22
Presented By:
Ali Hameed and Muhammad Zubair Idrees
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 2/22
` Introduction
` History
` Spontaneous Potential (SP) Log
` Operation
` Principle
` Log Presentation
` Tools
` Applications
` Reference
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 3/22
Spontaneous potential(SP),
or self potential, is a naturally
occurring electric potential
difference in the earth,
measured by an electrode
relative to a fixed reference
electrode.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 4/22
` The first electric log was recorded in 1927 in a well in the small oil field of
France.
` In 1929, electric resistivity logging was introduced on a commercial basis
in Venezuela, the United States, and Russia.
` In 1931 the spontaneous potential measurement was included with the
resistivity curve on the electric log.
` In 1931 the Schlumberger brothers, Marcel and Conrad perfected a
method of continuous recording.Its usefulness has been realized for over 50 years
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 5/22
The spontaneous potential log
measures the natural or
spontaneous potential differences
that exists between the borehole
and the surface in the absence of
any artificially applied current.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 6/22
` An electrode (usually lead) is
lowered down the well and an
electrical potential is registered at
different points in the hole with
respect to surface electrode.
` In order to record a potential the
hole must contain conductive mud,
as it cannot be recorded in air or oil-
base mud.
` Logging rate is approximately
1500m per hour and recordings are
continuous.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 7/22
` Mudcake Potential
Movement of charged ion through mudcake into permeable formation
` Shale wall Potential
Flow of fluids from borehole into shale formation.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 8/22
Electro chemical potential is
sum of Liquid junction and
membrane potential.
Fig1: Electrochemical Potential:
Liquid junction & membrane
potential
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 9/22
Liquid Junction:The greater the contrast in salinitybetween mud filtrate and formationwater, the larger is the potential
E J = K1 log10(aw /amf )
Membrane Potential:Na+ ions penetrates through theshale from the saline formationwater to the less saline mudcolumn, a potential is set up.
EM = K2 log10(aw /amf )
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 10/22
SP is presented in :
Track 1
mnemonic of SP.
No absolute scale.
Small bar represents a change of
10 mV.
Linear Scale
Recorded in the leftmost track of
the log suite, together with the GR
log.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 11/22
` In sand A, Rw is less than Rmf;i.e., formation water is saltier than
the mud filtrate.
` In sand B, the SP deflection is
less than in sand A, indicating a
fresher formation water.
` In sand C, the SP is reversed,indicating formation water that is
fresher than the mud filtrate (Rw >
Rmf).
` We may guess that, at about 7000
ft, Rmf and Rw are equal.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 12/22
` Electrodes
` A galvanometer
` Small 1.5 V battery
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 13/22
Calibration:
` A small battery and a potentiometer is placed in series between the two
electrodes.
` The logging engineer can adjust the potentiometer so that the SP
appears in track 1.
` Remove all extraneous potentials to the membrane potential, the SP
needs to be normalised in a computing centre so that there is no
potential (SP=0.0MV) opposite shale beds.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 14/22
` Lithological Indicator
` Detection of Permeable beds
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 15/22
The relationship between the SP and the
resistivities of the mud filtrate and the
formation water are determined
SP = -K log (Rmfe/Rwe)
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 16/22
` When mud filtrate salinities are
lower than connate water
salinities (i.e., Rmf is > Rw), the
SP deflects to the left (the SP
potential is negative). This is
called a normal SP.
` When the salinities are reversed
(i.e., salty mud and fresh
formation water, Rmf < Rw), the
SP deflects to the right. This is
called a reverse SP.
` Other things being equal, there is
no SP at all when Rmf = Rw.
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 17/22
V shale = (SPclean ± SPlog)/(SPclean-SPshale)
Vshale: shale volume
SPclean: maximum Sp deflection from clean wet zone
SPlog: Sp in the zone of interest (read from the log)
Spshale: SP value at the shale baseline (often considered to be zero)
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 18/22
The Sp is used primarily as a lithology indicator and as a correlation tool.It
has other uses as well:
` Detecting permeable beds
` Rw determination
` Correlation from well to well
` Shale Volume Indicator
` Geological Information
` Detecting bed boundaries
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 19/22
`GEOLOGICAL INFORMATION
`SHALE VOLUME CALCULATION
` Correlation and Facies
` Permeable Beds
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 20/22
` Geological interpretation of Well Logs by Malcolm Rider
` http://en.wikipedia.org/wiki/Spontaneous_potential
` http://en.wikipedia.org/wiki/Spontaneous_potential_logging
` http://www.kaskus.us/showthread.php?t=899212&page=165
` http://www.petrolog.net/webhelp/Logging_Tools/sp/sp.html
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 21/22
THANK YOU!
8/3/2019 3.SP LOGs1
http://slidepdf.com/reader/full/3sp-logs1 22/22
QUESTIONS?
Recommended