Note: Descriptions are shown in the official language in which they were submitted.
~04S203
~ This application is a divisional of application S.N.
237,297 filed 8 Oceober 1975 and although it includes all o~ the principal
disclosure of S.N. 237,297 it is directed to certain aspects of the inven-
tion only, the parent application being directed to other aspects and
another divisional application S.N. ~ o ~ o O ~ filed ~u4ne ~, ~7
being directed to still further aspects.
BACKGROUND OF THE INVENTION
A technique typically employed to determine the presence of
hydrocarbons in earthformations is to electrically log boreholes drilled
in these formations. Normally, formations saturated mostly with hydro-
carbons will exhibit a high electrical reslstivity, while formations satur-
ated mostly with water or brine will exhibit a low electrical resistivity.
However, it has been determined that the presence of shale in a formation
substantially decreases the resistivity of the formation to the extent
that commercially producing reservoirs in shaly formations display a
resistivity that would otherwise indicate nonproductivity.
U.S. Patent 3,895,289 issued 15 July 1975, discloses a relation ~ ~ ~
between dielectric constant of a shaly sand formation, 100% water saturated, ~ -
and a conductivity parameter related to shaliness, and provides a method ~ ~
.
of determining if there is enough shale in a formation that it must be taken
into account when evaluating electrical logging results; but does not disclose
a method for quantitatively determining the partial hydrocarbon saturation
and partial water (brine) saturation of the formation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a schematic representation of logging equipment
arranged in a borehole and at the earth's surface to conduct e~rthmeasure-
ments in accordance with the present invention.
1. g~
.. . ~ . .
. ,
104~Z~3
FIGURES 2A and 2B illustrate side and front views of a bow
sprlng suitable for use with the apparatus of FIGURE 1.
FIGURE 3 is another schematic representation of logging
equipment arran8ed in a borehole and at the earth's surface to conduct
earth measurements in accordance with the present invention.
FIGURES 4A and 4B illustrate side and front views of a bow
spring for use with the apparatus of FIGURE 3.
FIGURE 5A is an electrical diagram, partially in schematic
and partially in block form, of electrical equipment suitable for use in
connection with the equipment of FIGURES 1, 2A, 2B, 3, 4A and 4B.
FIGURE 5B is an electrical diagram illustrating the equivalent ~ -
electrical circuit of an earth formation during an electrical resistivity
measurement in a borehole useful in understanding the operation of the
apparatus of FIGURES 1, 2A, 2B, 3, 4A, and 4B.
FIGURE 6 is a waveform diagram useful in understanding the
circuit of FIGURE 5A.
FIGURE 7 is the graphical illustration of core conductivity
(C ) as a function of equilibrating solution conductivity (C ).
FIGURE 8 is a graphical representation of the measured change
in dielectric constant with partlal water saturation for four shaly sand ;
formation samples.
SUMMARY OF THE INVENTION
The degree of water (brine~ saturation of a sub`surface for-
mation saturated partially with an aqueous saturant and partially with
electrically inert matter is determined from measurements of dielectric
constant.
It has been discovered that the dielectric constant of a
shaly sand formation changes as a function of water (brine) saturation,
snd ~hae thi~ variation is defined by the relation K/Ko = S P, where:
. .
~ - -: . :
: ,:: : . - .. .: . , ~ ,
'. : ~
, . , ~ ' ' :
~04~
K = dielectric constant
K = dielectric constant at 100% water saturation
Sw = water saturation
p = shaliness exponent
It has also been discovered that this relation is not significantly
affected by a change in salinity of the saturating aqueous solution.
When a borehole is drilled into a formation, normally the
formation fluids in the vicinity of the borehole wall will be displaced
by drilling fluids. In a formation saturated with fluids saturants, ;
10 such as water and fluid hydrocarbons, partial water saturation of the
formation can be determined from "shallow" measurements of dielectric
constant near the borehole wall, and from deeper measurements of dielectric
constants in portions of the formation not penetrated by drilling fluids,
if the value of "p" is known for the formation.
In another embodiment of the invention, partial water
saturation is determined utilizing only "deep" dielectric constant measure-
ments. In this embodiment, the conductivity relation for a partially
water saturated shaly sand formation.
Ct = F* (C~ S~ + BQv S~ P)
is employed, where:
Ct = specific conductivity of the shaly sand formation,
mho cm 1,
F* = formation resistivity factor for shaly sands
C~ = specific conductivity of the aqueous saturant, mho cm 1
S~ = partial water saturation
n = desaturation exponent
B = equivalent conductance of clay exchange cations as a
function of C~ at 25C, mho cm2meq 1
Qv = cation exchange capacity per unit pore volume, meq ml 1
p = shaliness exponent
- - . ~ . . - :
.. ~ , , :. . : :
~045ZiO3
The value of Ct, F*, C~ are obtained from routine well logging methods.
Although the value of "n" varies somewhat for different types of shaly
sand, it has been determined that a value of 2 can be used for "n"
without introducing excessive error. The quantity BQv S~ P, a conductivity
parameter related to shaliness, has been found to be related to dielectric
constant, and the value thereof is directly determined by correlating
the measured dielectric constant with the relation between dielectric
constant and BQv S~ P. From the information thus obtained, S~ , the aqueous
portion of formation saturants, can be calculated.
A primary advantage of this invention is that it permits a
determination of the probable productivity of a hydrocarbon reservoir
located in a shaly sand formation from well logging information.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The conductivity equation for shaly sands, 100% saturated with
an aqueous solution, is as follows:
CO = F* (C~ + BQV )
The paper entitled "Electrical Conductivities in Oil Bearing Shaly Sands"
by M.H. Waxman and L.J.M. Smits, Society of Petroleum Engineers Journal,
June 1968, page 107 describes the theoretical basis for this equation.
In the equation, the terms have the following meanings:
CO = specific conductivity of shaly sand, 100% saturated
with aqueous solution, mho cm 1,
F* = formation resistivity factor for shaly sand, which
has been found to be related to porosity, ~ by what
is known as Archie's first empirical equation
F* = ~-m
(See Archie, G.E., "The Electrical Resistivity Log
as an Aid in Determining Some Reservoir Characteristics",
Trans., AIME (1942), Vo. 146, p. 54-67. The constant,
3~ m, has a value of approximately 2, but varies somewhat
~ depending on the saDd characteristics.)
:
1045Z03
C ~ = speclfic conductivity of the saturating aqueous
solution, mho cm 1
Q v = cation exchange capacity per unit pore volume,
meq ml 1
B = equivalent conductance of clay exchange cations
as a function of C~ at 25C, mho cm2 meq 1
It is known that a relationship exists between dielectric constant, measured
at frequencies less than about 50 KHz, of a 100% brine saturated shaly sand
formation and the term BQ v , the conductivity parameter related to shaliness.
lQ By determining the BQ vvalue of a number of shaly sand earth samples at
100% water saturation and the corresponding value of dielectric constant
for each sample, a correlation can be prepared that permits a determination
of the BQv value of a portion of an earth formation from a measurement of
dielectric constant.
We have determined experimentally that the dielectric constant
of a shaly sand formation also varies as a function of water saturation.
The dielectric constant of shaly sand formation samples measured at water
saturation less than 100% has been found to be related to dielectric
constant measured at 100% water saturation, by the relation:
K = KoS~ P
where:
K = dielectric constant
Ko = dielectric constant at 100% water saturation
S ~ = partial water saturation
p = shaliness exponent -
FIGURE 8 is a graphical representation of the change in dielectric
constant with a change in water saturation for a particular set of shaly
sands. This graph indicates a value for "p" of about 0.8, but the value
of "p" may be different for other formations having different textures
cIay d~tribution, or other characteristics. From information available
at this time it-appears that the value of "p" can vary from 0.7 to 1.3.
5.
. - ~ . , . . ~ ... .
104S203
It has also been determined experimentally that this relatlon
is not substantially affected by a change in salinity of the water. This
discovery is of particular significance because it permits partial water
saturation to be determined from measurements of dielectric constant.
The measured dielectric constant does, however, change as a
function of the frequency of the electrical signal used for measuring
dielectric constant. Dielectric constant has been observed to decrease with
increasing frequency. At frequencies above about 50 KHz, dielectric
constant resulting from shaliness may not be great enough to be useful in
practicing the invention.
During normal well drilling operations, native formation
fluids adjacent the wellbore will be displaced by drilling fluids. If
water based drilling fluids are used a portion of the formation adjacent
the wellbore will become nearly 100% water saturated. Values for K
can then be determined by measuring dielectric constant in said portion
of a formation adjacent the borehole. By measuring dielectric constant in
substantially the same portion of the formation, but at a depth from the
borehole surface not penetrated by drilling fluids, the partial water (brine)
saturation of the formation can be determined for any sand formation
2a having a known value of "p".
This embodiment of the invention, therefore, permits the
partial water saturation of a shaly sand formation saturated partially by
water and partially by an electrically inert fluid to be dete~rmined. The
electrically inert fluid portion of such formation saturants, which may be
fluid hydrocarbons, is therefore equal to l-S~ . Partial hydrocarbon
saturation is hereafter referred to as S H.
It is understood that if the electrically inert saturant is
comprised of solid matter that will not be displaced by the aqueous drilling
fluid, the "shallow" dielectric constant measurement as described hereinabove
may not determine an accurate value for K . However, values for K can
also be determined for a portion of a formation by measuring dielectric
6,
. ~ . . . .
1~)45203
,
constant in an ad~acent zone in sald formatLon that is water saturated,
if such a water leg exists.
In a second embodiment of the invention, only the deep
dielectric constant measurement is employed. Although additional
well-logging information must be known in order to practice this second
embodiment, it can also be employed for determining partial water saturation
in formation zones partially saturated by a solid electrically inert satur-
ant, such as kerogen when no water leg is present in said formation. The
following discussion should be of assistance in understanding the second
embodiment of the invention.
In 1942, Archie (see Archie, G.E., supra) proposed that the
resistivity index of clean (nonshaly) sandstone partially saturated with
water follows the relation:
Rt = 1 (1)
R S t-
where:
Rt = resistivity of a partially water saturated
formation ohm -m
Ro = resistivity of a 100% water saturated
formation ohm -m
I = resistivity index
S~ = partial water saturation
r~ = desaturation exponent (equal to about 2 for
nonshaly sandstone formations)
Rewriting this equation in terms of conductivity:
Ct = COS ~ (2)
Another parameter which has been found to be useful is
the formation factor F. Formation factor for nonshaly sands is ~
defined as: -
, .
.
-
104S203 , ~,,
R (3)
where:
R = resistivity of a 100% water saturated formatlon,
ohm -m
R~ = resistivity of the saturating water, ohm -m
Rewriting equation (3) in terms of conductivity:
C = 1 C (4)
and substituting the value of CO from equation (2) into equation (4):
Ct = F C ~S ~n (5)
which is the equation of conductivity of a partially brine saturated
nonshaly sandstone formation.
By using the relationship that has been found to exist between
dielectric constant at partial water saturation, and dielectric constant
at 100% water saturation, shaliness effects on the conductivity of partially .
water saturated formations can be taken into account. As stated above,
dielectric constant in a 100% water saturated formation, Ko~ is proportional
to the shaliness conductivity parameter, BQ v , from the relation: -
C = _ (C ~ + BQ v) (6)
As stated hereinabove, dlelectric constant, K, also changes with decreasing
water saturation according to the relation:
. K = KoS~ P (7)
It follows, therefore, that since dielectric constant changes with water
saturation by the factor, S~ P, the conductivity due to shaliness, also
changes with water saturation by this same factor, Therefore, the complete
equation for the conductivity of shaly sand, Ct, partially saturated with
brine and partially saturated with an electrically inert saturant can be
written in the form:
t -F* (C~ S~ + B~v S~ ) (8)
. . .
: . ' ~ :,
"'','', ' . " ~ ~ . ' 1~, ,
104SZ03
In order to use this equation, certain inEormation routinely
obtained from well logs is necessary. lhe value of C ls obtained from
resistivity logs. The value of F* is determined from porosity which is
routinely determined for each reservoir. The value of C ~ , the water
conductivity, is determined from actual measurements of the brine that is
present in the reservoir, or from the s.p. (self potential) log. The
value of " ~" has beén experimentally determined to be approximately
equal to 2 in shaly sandstone formations.
As stated above, BQv S~ P is proportional to dielectric constant.
As also disclosed in U.S. Patent 3,895,289 dielectric constant at 100%
water saturation, K , is related to the conductivity parameter, BQ v ;
that is Ko BQ v . Since it has been established that K = KoS~ P, it
follows that K ~ BQ v S ~ P, and that K is related to BQ v Sw P in the
same manner that Ko is related to BQ . Therefore, the graphical relation
between K and BQ v which can be determined as described hereinafter also de-
fines the relation between K and BQv S ~P, and a value for BQ v S ~ P is
determinable by correlating the measured value of dielectric constant with
said graphical relation.
After the value of the term BQ v S~ P is determined from a
dielectric constant measurement, the value of all the terms in the equation:
C = 1 (C ~." S ~ + BQVS,~, ) (9) : ~
t F
are now known except for S ~ , the partial water saturation, which can now
be calculated. The fractional portion of the saturants composed of
electrically inert matter is equal to l-S ~ . For a formation saturated
with water and hydrocarbon, the foregoing method provides a method of quanti-
tatively determining the amount of hydrocarbons present in the formation.
In order to practice this invention, it is necessary to measure
the dielectric constant of a formation. One embodiment of the invention
requires the making of a "deep" and "shallow" dielectric constant measure-
ment. The second e~bodiment of this invention requires only the "deep"measurement, but the relation between dielectric constant and the conductivity
1045Z03
parameter, BQ vS ~P, must have been determined, and other routine well
logging information must be known.
FIGURE 1 illustrates apparatus Por making shallow dielectric
constant measurements. The apparatus is comprised of an elongated housing 1
to which is affixed in the usual manner a number of bow springs 5 each of
which carries a plurality of electrode contacts 7A and 7B (see FIGURES 2A
and 2B) positioned on the bow springs so as to be urged into contact
with the walls of a borehole 3. The housing 1 is suspended from a logging
cable 11 which is wound on a reel drum 15 which extends over a sheave
13 in the usual manner so as to be suitably positioned in the borehole.
- Electrical leads within the logging cable 11, that conduct electrical
signals from the downhole equipment contained in housing 1, are connected
to electrical leads within an electrical conduit 17, which in turn,
connect to the surface electrical equipment package 18. Electrical
equipment package 18 may include, among other things, suitable recording
and display apparatus.
The electrodes 7A and 7B on the bow springs 5 are supported
by electrical insulators and are spaced apart a sufficient distance so that
electrical currents and flux lines flowing therebetween will penetrate
the desired distance into the earth formation. This spacing may preferably
be about 5 inches. Electrodes 7A and 7B are connected to electrical leads
9 which are electrically insulated from any borehole fluids. Leads 9
connect, into the downhole electronic equipment contained in housing 1. ~
FIGURE 3 illustrates apparatus for making "deep" dielectric ~ -
constant measurements, in a portion of the formation not penetrated by
drilling fluids. This apparatus is identical to the apparatus in FIGURE 1
except that the electrode contacts are spaced further apart. Each of the
Bow springs (see FIGURES 4A and 4B) contains only one of the electrodes of
an electrode pair. Electrical currents and flux lines will flow between
electrade ~A located on an upper bow spring and electrode 8B positioned on
a lower bow spring. The spacing between the electrodes of an electrode
pair may preferably be about 5 feet.
lQ.
-
104SZ~3
FIGURE 5A illustrates an electrical schematic diagram, partially
in block form, of apparatus suitable for use with the apparatus previously
described for measuring capacitance in a borehole, from which dielectric
constant is determined. The appara~us shown in FIGURE 5A is divided into
two sections, the surface equipment and the downhole equipment. The
surface equipment is connected to cable 17 (shown in FIGURES 1 and 3)
and interconnected with the downhole equipment through cables 17 and 11, and
electrical leads inside housing 1. The surface equipment includes power
supply 21 which preferably is a DC supply, recording oscillograph 23 and
recorder 25 for making a time recording of a voltage derived from the
downhole equipment. Power supply 21 is electrically connected through
the cables 17 and 11 to rectangular wave generator 27 within the housing
1. Rectangular wave generator 27 may be a multivibrator. The output of
the generator is connected by lead 37 to contact member 7A (assuming that
the configuration of FIGURE 1 is used), and through resistor 39 of low
resistance to contact member 7B. Contact electrodes 7A and 7B are designed ~ ~
to have a very large contact area with the earth formation so that the -
contact impedance will be quite low. The contact electrodes may be
platinized electrodes having sufficient diameter to minimize contact im- ;
pedance by making the contact resistance and the contact impedance as
- low as possible. (The combination of the contacts and the borehole wall
is the equivalent of a resistor and a capacitor in parallel.)
The voltage appearing across resistor 39 is applied to the
input of gated amplifier 29. A gating signal is derived from lead 37 of
generator 27 so that, in effect, the output voltage of generator 27 switches ;-
the amplifier 29 on and off. The output signals of the gated amplifier
are applied through leads 31 to the recording oscillograph 23 in the surface
equipment. The output signals from the gated amplifier are the gated signal
as ~hown in FIGURE SD and a signal equal to the generator 27 output as shown
in FIGUR~ 6A. The voltage appearing across resistor 39 is also trans~itted
11 .
~04s~ao3 "
to the earth's surface to be recorded by recorder 25. If desired, and
if the recording oscillograph is provided with sufficient input circuits,
the signal appearing across resistor 39 may be simultaneously recorded
by recording oscillograph 23.
Because of the capacitive reactance between the contacts 7A
and 7B resulting from the effective capacitor produced by the contacts and
the formation in contact therewith, the current passing through resistor 39
will lead the voltage produced by generator 27. The contact impedance of
contacts 7A and 7B is very low and will not introduce significant errors
into the measurements. The capacitive reactance will be produced almost
entirely by the effective capacity, Cf, of the earth. The dotted lines
in FIGURE 6B illustrate the wave form that would be produced were there no
capacitive reactance in the circuit. The solid rule line represents the
current wave form that will typically be produced.
The electrical characteristics of the formation sample can be
represented by a capacitive component Cf and a resistive component Rf
in parallel as illustrated in FIGURE 5B. The current from generator 27
flows through the formation sample and through resistor 39. Designating
the pulsed voltage amplitude across resistor 39 as V and the resistance
value of resistor 39 as R, it is apparent that I = Vr . If the pulsed
voltage amplitude produced by generator 27 is designated as E , then
the formation sample resistance Rf is given by:
E _ V (E V )R
Rf = o I = o - r ~ (10)
Vr
From the above it can be seen that the effective resistance of
the formation can be determined from the recordations of the voltage
generated by generator 27, from the voltage produced across resistor 39,
and the resistance of resistor 39.
Manifestly, the time integral "T" of each voltage pulse appearing
at the output of generator 29 and illustrated by the wave form of FIGURE 4D
is given by the formula:
12.
.
;'. ~ - '. '
~04s:ao3
T = IR(ReffCf) (ll)
where
R = R R
eff f (12)
Rf+R
so that:
Cf = T = TE
IRReff V R(E - Vr~ (13)
From the above it is apparent that the capacitance of an earth sample can
be measured using the apparatus described above.
The instrument may be calibrated to measure dielectric constant
directly. Initially a number of earth samples having a wide range of
dielectric constants are obtained. The samples may have been previously
obtained from coring operations in the earth, or they may be specially ~ ~
obtained for thç purpose of calibrating the instrument. The dielectric ;~ ~;
constant of each of the samples is then obtained by techniques well known
to the art such as described in the texts: "Solids State Magnetic and
Dielectric Devices", Library of Congress Catalog Card Number 59-6769, John
Wiley & Sons, New York, 1959; and "Theory of Dielectrics" by a. Frohlich,
University Press, Oxford, 1958. For example, an earth sample may be
placed between conductive plates of known dimensions and the capacitive
reactance of the capacitor resulting therefrom can then be measured. The `
dielectric constant of the earth sample can be calculated from the area of
the plate and the spacing between the plates. Such techniques have been
well known to the art for many years and will not be further discussed ;
herein.
After the dielectric constant of the various earth samples have ~ -
been obtained, these samples or earth samples obtained from the same forma-
tions, having the same dielectric constant, are placed in contact with the
contacts 7A and 7B. The thickness of each formation sample should be
great enough so that the electric lines of force between the pairs of contacts
. .
13.
, ~, .
10~SZ03
will pass only through the formation sample. The equipment illustrated
in FIGURE 3A ls then actuated so that a substantially rectangular
wave pulse train with a frequency spectrum predominantly less than 50 KHz,
as illustrated in FIG~RE 4A, is generated by generator 27.
A number of earth samples of known dielectric constant are
successively placed in contact with the electrodes and the area of the
lntegrated signal (which is the time integral "T") recorded by oscillograph
23 is measured for each sample. Thus there is obtained a relationship
between the integral of the gated signal and the dielectric constant of
the earth samples placed between the electrodes. The dielectric constant
of any unknown earth sample can be obtained by measuring the parameters
described above and correlating with the calibration curve. As stated
hereinabove, the dielectric constant of shaly sand formation samples has
been observed to vary with frequency; therefore, waveforms having substan~
tially the same frequency spectrum must be used for all dielectric con-
stant measurements made in calibrating instruments, preparing calibra-
tion curves, and measuring formation dielectric constant.
As stated earlier, it has been determined that the dielectric
constant of a brine saturated formation, measured at frequencies less
than about 50 KHz, is proportional to cation exchange capacity. `~
For the purpose of establishing the relationship between
dielectric constant and cation exchange capacity, ~v , earth samples whose
dielectric constant has been determined are subjected to laboratory analysis
for the purpose of determining the cation exchange capacity per unit pore
volume of these samples. The particular laboratory analysis to which the
earth samples are subjected is not part of the invention and may be any
standard known prior art type of analysis such as has been described and
shown to he useful in the paper entitled "Electrical Conductivities in Oil
Bea~i~g Shaly Sands" by M.H. Waxman and L.J.M. Smits, Soclety of Pe-troleum
,
14.
.
~45Z~3
Engineers Journal, June, 1968, page 107. One particular method commonly
used in the prior art comprises repeated equilibration of crushed rock
samples with concentrated barium chloride solutions, washing to remove
excess barium ions, followed by conductometric titration with standard
MgS04 solution. The latter procedure is also described in the article
"Conductometric Titration of Soils for Cation Exchange Capacity" by
M.M. Mortland and J.L. Mellor, Proc. Soil Science Society of America
(1954), Column 18, page 363. Another technique that may be used involves
chromatographic measurements using ammonium acetate solutions as described
in the artlcle "Effect of Clay and Water Salinity on Electro-Chemical
Behavior of Reservoir Rocks" by H.J. Hill and J.D. Millburn, appearing in
Transactions of the AIME, (1956), Volume 207, pages 65-72.
As stated earlier, the conductivity equation for 100% brine sat-
urated shaly sands is:
Co F* (C", ~ BQ V )
FIGURE 7 graphicslly illustrates this relation, showing the change in the
conductivity of a brine saturated shaly earth sample with increasing
conductivity of the saturating solution. It is evident from FIGURE 6 that
except for very low salinity levels the relationship between CO, the sat-
urated core conductance, and C~ , the saturating solution conductance, is
linear, and the value of B in this range is a constant. Subsequently the
~ .
value of B will be treated as a constant sinCe this introduces very little ~ -~
error.
Since dielectric constant, measured at frequencies less than
about 50 KHz, is proportional to Qv , the cation exchange capacity per unit
pore volume, with B being treated as a constant, dielectric constant is
also proportional to BQv .
The conductivity of a number of 100% water saturated shaly
sample8~ having known values for Qv , is determined at different levels of
salinity. The relationship between the conductivity of the saturating
15-
104S21~3
solution alone and the conductivity of a water saturated shaly sample will
appear similar to FIGURE 6. The pro~ection of the straight portion of
the line on the hori~ontal axis represents the value of BQv . The values of
BQ vvs Qvfor each sample are plotted and from this graph, the value of BQv
for the earth formations of ~nterest can be obtained as a function of
Q v , the cation exchange capacity, thereby permitting the value of BQ v
as a function of dielectric constant to be determined.
As an alternative to the preceding method of determining a
value of BQv as a function of dielectric constant, the initial step of
determining the value of Qv , alone, can be skipped, and the process for
determining the value of BQv can be employed on each of the samples after
the value of dielectric constant is measured. Thus there is obtained a
relationship between dielectric constant at 100% brine saturation, K , and
the conductivity parameter, BQv . It will be noted that this method requires
only one laboratory analysis rather than two for determining a value of
BQv ;
As explained earlier, the conductivity parameter related to
.
shaliness in partially water saturated shaly sands, BQVS~P, is related to
dielectric constant K, the same way that the conductivity parameter
related to shaliness in 100% water saturated shaly sands, BQv is related to
the dielectric constant of 100% water saturated shaly sands, K ;
therefore, the graphical relationship that permits BQv to be determined
from a measurement of Ko, also permits BQVSWP to be determined from a
measurement of K.
The foregoing description of a preferred embodiment of the in~
vention discloses a method of determining the aqueous portion of formation
saturants. The remainder of the formation saturants, comprised of
electrically inert matter, is therefore equal to l-S~ . The electrically ~ -
inert formation can be hydrocarbons or other matter such as sulfur.
16.
-',' '`' '
1~4S2~
Coring operations or other forma~ion testing will indicate the nature of
the electrically inert matter. If tests indlcate the presence of
hydrocarbons, the foregoing disclosure is a very useful method of ob-
taining quantitative evaluation of the aqueous and hydrocarbon phases of for-
S mation saturants.
It is understood that if oil based drilling fluids are
employed, the foregoing methods for obtaining partial water saturation
of a formation may not be practical. Under such circumstances, it would be
necessary to determine the value of K by measuring dielectric constant
on cores in the laboratory.
: ~.
-
;:. , ~ . : -
,, . : . , : : ::, . , .
:':: :-. . .. , ,.. ,, . ~
