U.S. patent application number 11/998331 was filed with the patent office on 2014-03-06 for method of analysis of polymerizable monomeric species in a complex mixture.
The applicant listed for this patent is Robert E. Hermes. Invention is credited to Robert E. Hermes.
Application Number | 20140060818 11/998331 |
Document ID | / |
Family ID | 40985807 |
Filed Date | 2014-03-06 |
United States Patent
Application |
20140060818 |
Kind Code |
A1 |
Hermes; Robert E. |
March 6, 2014 |
METHOD OF ANALYSIS OF POLYMERIZABLE MONOMERIC SPECIES IN A COMPLEX
MIXTURE
Abstract
Method of selective quantitation of a polymerizable monomeric
species in a well spacer fluid, said method comprising the steps of
adding at least one solvent having a refractive index of less than
about 1.33 to a sample of the complex mixture to produce a solvent
phase, and measuring the refractive index of the solvent phase.
Inventors: |
Hermes; Robert E.; (White
Rock, NM) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hermes; Robert E. |
White Rock |
NM |
US |
|
|
Family ID: |
40985807 |
Appl. No.: |
11/998331 |
Filed: |
November 28, 2007 |
Current U.S.
Class: |
166/244.1 |
Current CPC
Class: |
C09K 8/40 20130101; G01N
21/4133 20130101; G01N 2021/7776 20130101; G01N 21/41 20130101 |
Class at
Publication: |
166/244.1 |
International
Class: |
C09K 8/40 20060101
C09K008/40; G01N 21/41 20060101 G01N021/41 |
Goverment Interests
STATEMENT OF FEDERAL RIGHTS
[0001] The United States government has rights in this invention
pursuant to Contract No. DE-AC52-06NA25396 between the United
States Department of Energy and Los Alamos National Security, LLC
for the operation of Los Alamos National Laboratory.
Claims
1. A method of selective quantitation of a polymerizable monomeric
species in well spacer fluid, said method comprising adding at
least one solvent having a refractive index of less than about 1.33
to a sample of the well spacer fluid to produce a solvent phase,
measuring the refractive index of the solvent phase, and thereafter
using the well spacer fluid with a drilled well.
2. The method of claim 1, wherein the solvent is a simple
alcohol.
3. The method of claim 2, wherein the simple alcohol is
methanol.
4. The method of claim 1, wherein the solvent is substantially free
of methanol.
5. The method of claim 1, wherein the polymerizable monomeric
species is an acrylate monomer.
6. The method of claim 1, wherein the polymerizable monomeric
species is selected from the group consisting of methyl acrylate,
methyl methacrylate, methacrylic acid, acrylamide, n-vinyl
pyrrolidone, N-butylurethane-O-ethyl acrylate, methyl ether
polyethylene glycol monomethacrylate, 2-hydroxyethyl methacrylate,
styrene, and mixtures thereof.
7. The method of claim 6, wherein the polymerizable monomeric
species is methyl methacrylate.
8. The method of claim 1 wherein the well spacer fluid further
comprises a polymer comprised of the polymerizable monomeric
species, wherein said polymer is substantially insoluble in the
solvent phase.
9. The method of claim 8, wherein the polymer is selected from the
group consisting of poly(methylmethacrylate), poly(methacrylic
acid), polystyrene, and mixtures thereof.
10. The method of claim 9, wherein the polymer is
poly(methylmethacrylate).
11. The method of claim 1 wherein the well spacer fluid is a
shrinking spacer fluid comprising at least one additional component
selected from the group consisting of an initiator, an inhibitor,
an emulsifier, a viscosifier, a weighting agent, and combinations
thereof.
12. The method of claim 1, wherein the well spacer fluid is a water
control fluid.
13. The method of claim 1, wherein the refractive index of the
solvent phase is from about 1.33 to about 1.43.
14. The method of claim 1, wherein the refractive index is measured
by means of a handheld refractometer.
15. A method of selective quantitation of a polymerizable monomeric
species in well spacer fluid, said method comprising a) adding at
least one solvent having a refractive index of less than about 1.33
to a first sample of the well spacer fluid to produce a first
solvent phase; b) adding the same solvent to a second sample of the
well spacer fluid to produce a second solvent phase; c) measuring a
first refractive index of the first solvent phase at a first
timepoint; d) measuring a second refractive index of the second
sample at a second timepoint; e) using the first refractive index
and the second refractive index to calculate a rate of
polymerization of the monomeric species, and thereafter f) using
the well spacer fluid with a drilled well.
16. The method of claim 15, wherein the solvent comprises
methanol.
17. The method of claim 15, wherein the polymerizable monomeric
species is methyl methacrylate.
18. A method of selective quantitation of a polymerizable acrylate
monomer in a complex mixture comprising a polymer comprised of the
acrylate monomer, comprising adding at least one solvent having a
refractive index of less than about 1.33 to a sample of the complex
mixture to produce a solvent phase, measuring the refractive index
of the solvent phase, and thereafter using the well spacer fluid
with a drilled well.
19. The method of claim 18, wherein the complex mixture is well
spacer fluid, a water control fluid, or a combination thereof.
20. The method of claim 18, wherein the solvent comprises
methanol.
21. The method of claim 1, wherein the step of using the well
spacer fluid with a drilled well comprises inserting the well
spacer fluid into a well shaft.
22. The method of claim 1, wherein the step of using the well
spacer fluid with a drilled well comprises trapping the well spacer
fluid in well casing below a well head.
23. The method of claim 15, wherein the step of using the well
spacer fluid with a drilled well comprises inserting the well
spacer fluid into a well shaft.
24. The method of claim 15, wherein the step of using the well
spacer fluid with a drilled well comprises trapping the well spacer
fluid in well casing below a well head.
25. The method of claim 18, wherein the step of using the well
spacer fluid with a drilled well comprises inserting the well
spacer fluid into a well shaft.
26. The method of claim 18, wherein the step of using the well
spacer fluid with a drilled well comprises trapping the well spacer
fluid in well casing below a well head.
Description
FIELD OF THE INVENTION
[0002] The present invention relates to a method of analysis of a
polymerizable monomeric species in a complex mixture, for example
well spacer fluid, by means of refractive index measurements.
BACKGROUND OF THE INVENTION
[0003] A major concern in drilling wells is that the lining of the
shaft (the "casing") has the potential to collapse or rupture. When
drilling a well, individual lengths of tubes often are secured
together to form a casing string. Each section of the casing string
may be cemented within the wellbore before a next smaller diameter
portion is drilled and cased. The concentric casings form annuli
which may or may not extend the full length of the well. Fluids,
often referred to as spacer fluid or drilling fluid, typically are
inserted between the top of the cement and the wellhead within the
annular spaces. When these fluids are heated by oil pumped from
deep within the ground and having a relatively high temperature,
thermal expansion can create high pressures in the spacer fluid and
result in collapse or rupture of the casing. This is commonly known
as "annular pressure buildup." When this occurs, the well may
become inoperable and another well must be drilled at a significant
cost. In addition, contaminants may be leaked into the
environment.
[0004] One solution to this problem is described in U.S. Patent
Application 2007/0114033 (Hermes et al.), which describes a spacer
fluid that decreases in volume as the temperature of the fluid is
increased, thus reducing pressure build-up as high-temperature oil
is pumped through the production tubing. The spacer fluid comprises
a monomer which undergoes polymerization and decreases the volume
of the fluid as the reaction proceeds. Just prior to inserting the
spacer fluid into the well, the proper amount of initiator is
added. Thus, it is of critical importance to know the amount of the
monomer in the fluid, both at the time of mixing the fluid and
prior to inserting the fluid into the well shaft.
[0005] Additionally, spacer fluids containing polymerizable
monomers may be used for water control and/or shut-off applications
in the drilling industry. During drilling, geological formations
may be encountered which allow ingress of water (for example,
underground aquifers) or egress of drilling fluid (for example,
cavernous formations). In either case, the addition of spacer
fluids containing polymerizable monomers can seal the geological
formation when applied according to the teachings of U.S. Pat. No.
6,187,839. In these cases, it would also be important to know the
amount of monomer in the fluid prior to application in the
well.
[0006] Several factors complicate the determination of the amount
of monomer in the fluid. First, the spacer fluid is a complex
mixture that has a color and consistency similar to mud. Second,
the spacer fluid may be prepared on land, and subsequently shipped
by boat to an off-shore drilling rig, which may take several days
and be subject to weather and/or drilling schedule delays. Thus,
analysis may need to occur on the boat, which requires analytical
instrumentation that is robust, compact (due to space constraints),
accurate and relatively simple to use. A need exists, therefore,
for a method of determining the concentration of a polymerizable
monomeric species in well spacer fluid which meets the
aforementioned criteria.
SUMMARY OF THE INVENTION
[0007] The present invention meets this need by providing a method
for quantitation of a polymerizable monomeric species by use of a
refractive index detector (refractometer). Refractometry
instrumentation is robust, relatively straightforward to use, and
is available in a hand-held unit. One challenge in the application
of refractometry as described herein, however, is finding a
suitable solvent. The polymerizable monomeric species must be
soluble in, and selectively partition into, the solvent. The
remaining components of the complex mixture should be either
insoluble in the solvent or, if soluble, should not appreciably
contribute to a refractive index reading. In addition, the solvent
must have a sufficiently low refractive index to provide maximum
sensitivity, and must provide a sufficiently broad dynamic range.
The latter is important when the spacer fluid is a shrinking spacer
fluid, as a relatively large amount of the monomer may be required
to sufficiently decrease the volume of the spacer fluid.
Specifically, it has been found that the neat solvent should have a
refractive index of 1.33 or lower. It has further been found that
certain alcohol solvents meet the above criteria. It is further to
be understood that the present invention may be applicable not only
to well spacer fluid analysis, but to analysis of other complex
mixtures that require quantitation of a monomeric species.
[0008] The following describe some non-limiting embodiments of the
present invention.
[0009] In accordance with the purposes of the present invention is
provided in one embodiment a method of selective quantitation of a
polymerizable monomeric species in well spacer fluid, said method
comprising adding at least one solvent having a refractive index of
less than about 1.33 to a sample of the well spacer fluid to
produce a solvent phase, and measuring the refractive index of the
solvent phase.
[0010] A method of selective quantitation of a polymerizable
monomeric species in well spacer fluid, said method comprising
adding at least one solvent having a refractive index of less than
about 1.33 to a first sample of the well spacer fluid to produce a
first solvent phase; adding the same solvent to a second sample of
the well spacer fluid to produce a second solvent phase; measuring
a first refractive index of the first solvent phase at a first
timepoint; measuring a second refractive index of the second sample
at a second timepoint; using the first refractive index and the
second refractive index to calculate a rate of polymerization of
the monomeric species.
[0011] In yet another embodiment, a method of selective
quantitation of a polymerizable acrylate monomer in a complex
mixture comprising a polymer comprised of the acrylate monomer,
comprising adding at least one solvent having a refractive index of
less than about 1.33 to a sample of the complex mixture to produce
a solvent phase, and measuring the refractive index of the solvent
phase.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 depicts a graph of the concentration of methyl
methacrylate in the solvent phase of a sample of shrinkable well
spacer fluid. The y-axis represents the last 3 digits of the
refractive index units (1.3YYY) and the x-axis depicts time during
which the methyl methacrylate is depleted by polymerization.
[0013] FIG. 2 depicts a graph of the change in concentration of
methyl methylacrylate over time, where the primary y-axis (for
curve 1) represents the pressure trace of the spacer fluid
containing polymerizable monomer, the secondary y-axis (for curve
2) represents the percent conversion of methyl methacrylate monomer
to polymer (calculated from the refractive index readings in FIG.
1), and the x-axis represents time in minutes.
[0014] FIG. 3 depicts a graph of the stability of the methyl
methacrylate polymerizable monomer in a spacer fluid containing a
polymerization inhibitor as a function of time. The y-axis
represents the refractive index, and the y-axis depicts time in
weeks.
DETAILED DESCRIPTION OF THE INVENTION
[0015] All documents cited in the Detailed Description of the
Invention are, in relevant part, incorporated herein by reference;
the citation of any document is not to be construed as an admission
that it is prior art with respect to the present invention. To the
extent that any meaning or definition of a term in this document
conflicts with any meaning or definition of the same term in a
document incorporated by reference, the meaning or definition
assigned to that term in this document shall govern.
[0016] "Selective quantitation," as used herein, means determining
the concentration of a polymerizable monomeric species absent
significant interference from other species present in the
sample.
[0017] "Polymerizable monomeric species," as used herein, means a
chemical moiety capable of polymerization in the presence of a
suitable initiator under suitable reaction conditions, as would be
understood by one skilled in the art. Polymerization of a monomeric
species is understood to result in a polymer comprised of the
covalently bonded monomeric species.
[0018] "Well spacer fluid," as used herein, means a fluid suitable
for use in a drilled well, and which may be in contact with the
well casing, for example trapped in well casing annuli above the
top-of-cement and below the wellhead. "Shrinking spacer fluid," as
used herein, means a spacer fluid that decreases in volume upon
reaction of chemical species present in the fluid, for example, a
polymerization reaction.
[0019] "Water control fluid," as used herein, means a well spacer
fluid suitable for use in a drilled well to plug geological spaces
which either ingress water, or egress drilling fluid during the
drilling process.
[0020] "Solvent phase" as used herein means the portion of the
sample which comprises the bulk of a solvent and the species,
dissolved therein, and which results from mixing the solvent with
the sample and subsequently allowing the sample to partition into
at least two physically discernable phases. For example, if
methanol is added to a well spacer fluid, the solvent phase will
comprise methanol and a relatively clear methanol-soluble fraction;
measurement of the solvent phase by a refractometer will produce a
resultant refractive index.
[0021] "Substantially insoluble," as used herein, means that a
substance in a sample (e.g., well spacer fluid) substantially fails
to partition into the solvent phase upon mixing with the sample.
Any amount that may be soluble in the solvent is insufficient to
significantly affect the quantitation of a polymerizable monomeric
species in that solvent. In one embodiment, substantially insoluble
means that at least 99% of the substance is insoluble in the
solvent.
[0022] "Refractive Index," as used herein, means a refractive index
measured according to the method described herein by means of a
refractometer, one suitable example of which is a Palm Abbe.TM.
digital refractometer, model PA202 or PA203, manufactured by
Misco.TM., (Cleveland Ohio). The refractometer preferably has an
accuracy and/or precision of about +/-0.0001 units and electronic
temperature compensation capability.
Method
[0023] The method of the present invention comprises the step of
adding at least one solvent as described herein to a sample of well
spacer fluid to produce a solvent phase, and measuring the
refractive index of the solvent phase. The sample may contain any
amount suitable for measurement by a refractometer, but typically
is on the order of 10.0 ml. The data obtained from the refractive
index measurements may be used to quantitate the amount of a
polymerizable monomeric species ("monomer") present in a sample,
for example, by comparison to a calibration curve constructed from
refractive index measurements of multiple samples containing known
quantities of monomer. For example, a calibration curve may be
constructed by plotting the refractive index obtained by measuring
at least three refractive indices of at least three solvent phases
comprising known amounts of monomer to produce a range of
refractive indices, for example of from about 1.34 to at least
1.45. Alternatively, measurements of the refractive index of
multiple samples held under the same thermal conditions may be made
at given time intervals, the measurements converted to
concentration of monomer or percent conversion to polymer, and
plotted vs. time to produce information relating to the kinetics of
the polymerization reaction (i.e., "kinetic data"). An example of
kinetic data is depicted in FIG. 2, with additional information
obtained from a pressure vessel experiment with the same
formulation, that is, when shrinkage occurs within the vessel due
to the polymerization of the methyl methacrylate monomer.
Additionally, measurements of the refractive index of multiple
samples held under the same thermal conditions may be made at given
time intervals, and may provide information relating to the
stability of the well spacer fluid (i.e., "stability data"). An
example of stability data is depicted in FIG. 3.
[0024] In one non-limiting example, a chosen volume of
polymerizable spacer fluid is added to a test tube and weighed. The
same volume of a solvent is added, the test tube sealed with a
screw cap, and shaken vigorously to mix the components. The spacer
fluid components that do not dissolve in the solvent fraction
settle out, usually within 5 minutes. The test tube is opened, and
2-3 drops are placed in the sample well of the portable
refractometer. The refractive index reading is then compared to
samples of known concentration, such as a calibration curve, a
prepared spacer fluid at time zero, a percent conversion to
polymer, or other convenient indicator of monomeric species left in
the spacer fluid. The method is generally performed at a standard
temperature of about 20.degree. C.
Refractometer
[0025] For the purposes of the present invention, any instrument
capable of measuring the refractive index of a liquid sample may be
used. The instrument may be the size of a benchtop model, a
handheld model, or of a size therebetween. In one embodiment, the
refractometer is a hand-held refractometer. In one embodiment, the
refractometer is capable of measuring refractive indices of from at
least 1.3 to about 1.5, and more preferably from about 1.3330 to
about 1.5040. One example of a commercially available refractometer
suitable for this purpose is a MISCO.TM. Model PA202 Palm Abbe.TM.
Digital Refractometer, calibrated and used in accordance with the
original instructions.
Solvent
[0026] For the purposes of the present invention, "solvent" is
understood to mean a single solvent or a mixture of two or more
solvents wherein the solvent or mixture of solvents has a
refractive index which is less than purified water. In other words,
when two or more solvents are present, an individual solvent may
have a refractive index of greater than that of purified water,
however, if the refractive index of the combination of solvents is
less than that of purified water, then the combination is
considered a suitable solvent for the purposes of the present
invention. It is further known that mixtures of alcohols and water
produce higher refractive indices than either of the two neat
liquids alone, as discussed in A. E. Leach and H. C. Lythgoe, "The
detection and determination of ethyl and methyl alcohols in
mixtures by the immersion refractometer", J.A.C.S. 27, 964 (1905),
and J. V. Herraez and R. Belda, "Refractive indices, densities, and
excess molar volumes of monoalcohols+water", J. Solution Chem. 35,
1315 (2006). Both references note that when methanol is present in
the mixture, the refractive index is raised to a lesser degree than
other alcohols (for example, water has a refractive index of
1.3326, and methanol has a refractive index of 1.3264, whereas a
0.333 mixture (by mole fraction) of the two produces a refractive
index of 1.3396. Thus, methanol would provide a larger dynamic
range for the determination of polymerizable monomeric species in
the spacer fluid composition.
[0027] In one embodiment, the refractive index the solvent is about
1.4 or less, alternatively is about 1.34 or less, and alternatively
is from about 1.32 to about 1.34. The solvent should be immiscible
in the well spacer fluid, i.e. when mixed with the well spacer
fluid and allowed to stand for a period of time, the solvent should
form a separated solvent phase that is distinguishable on the basis
of color, opacity, or other physical criteria. The polymerizable
monomeric species should be substantially soluble in the solvent,
whereas the corresponding polymer should be substantially
insoluble. Preferably, the components of the well spacer fluid,
other than the polymerizable monomeric species, also are
substantially insoluble in the solvent, or if soluble, do not
substantially interfere with refractive index measurements.
[0028] In one embodiment, the solvent is a simple alcohol,
understood herein to mean a C.sub.1-C.sub.4 alcohol, for example,
methanol, ethanol, propanol, butanol, and combinations thereof. In
an alternative embodiment, the solvent is methanol. In yet another
embodiment, the solvent is substantially free of methanol.
Well Spacer Fluid
[0029] The well spacer fluid may be any fluid comprising a
polymerizable monomeric species that is inserted into a drilled
well shaft, for example an oil well shaft, and which may be placed
in contact with the well casing or with a geological formation. In
one embodiment the well spacer fluid is a shrinkable well spacer
fluid. In an alternative embodiment, the well spacer fluid is a
water control fluid. One example of a shrinkable well spacer fluid
is described in U.S. Patent Application 2007/0114033 (Hermes et
al.). The well spacer fluid is a complex mixture that may comprise
a plurality of components, including but not limited to water, a
thickening agent (or "viscosifier"), barite, emulsifiers, defoamer,
polymerization inhibitor, polymerization initiator, a base, a
dispersant, the polymerized monomeric species (i.e., the
"corresponding" polymer of the polymerizable species), and
combinations thereof. In one embodiment, the well spacer fluid
comprises an additional component selected from the group
consisting of an initiator, an inhibitor, an emulsifier, a
viscosifier, a weighting agent, and combinations thereof. The
additional components preferably are insoluble in the added solvent
and do not significantly partition into the solvent upon mixing
with the sample. To the extent that an additional component is
soluble in the added solvent, the component should interfere
minimally with the determination of the refractive index.
Preferably, any interference with the refractive index
determination would produce a change in refractive index that is
within the margin of error of the instrument.
Polymerizable Monomeric Species
[0030] The polymerizable monomeric species may be any species
suitable for use in well spacer fluid and capable of undergoing
polymerization under suitable reaction conditions. The monomer
should be substantially soluble in the solvent which is added to
the well spacer fluid and should produce a detectable difference in
the refractive index when present in the solvent. One preferred
class of polymerizable monomeric species suitable for use in the
present invention is acrylate polymerizable monomers, understood
herein to include acrylate- and methacrylate-containing monomers.
Non-limiting examples of suitable polymerizable monomeric species
include, but are not limited to, methyl acrylate, methyl
methacrylate, methacrylic acid, acrylamide, N-methyl acrylamide,
N-methyl methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl
methacrylamide, ethyl acrylate, ethyl methacrylate, N-ethyl
acrylamide, N-ethyl methacrylamide, N,N-diethyl acrylamide,
N,N-diethyl methacrylamide, N,N-diethylaminoethyl acrylate,
N,N-diethylaminoethyl methacrylate, 2-methoxyethyl acrylate,
2-methoxyethyl methacrylate, N-(2-methoxyethyl) acrylamide,
N-(2-methoxyethyl) methacrylamide, n-propyl acrylate, 2-propyl
acrylate, n-propyl methacrylate, 2-propyl methacrylate,
N-(n-propyl) acrylamide, N-(n-propyl) methacrylamide, N-(2-propyl)
acrylamide, N-(2-propyl) methacrylamide, n-butyl acrylate, n-butyl
methacrylate, N-(n-butyl) acrylamide, N-(n-butyl methacrylamide),
ethoxyethyl acrylate, ethoxyethyl methacrylate, N-(ethoxyethyl)
acrylamide, N-(ethoxyethyl methacrylamide), 4-ethoxyethyl styrene,
ethoxyethoxyethyl acrylate, ethoxyethoxyethyl methacrylate,
N-ethoxyethoxyethyl acrylamide, N-ethoxyethoxyethyl methacrylamide,
glycidyl acrylate, glycidyl methacrylate, N-(glycidyl) acrylamide,
N-glycidyl methacrylamide, hexoxyethyl acrylate, hexoxyethyl
methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
N-(2-hydroxyethyl acrylamide), N-(2-hydroxyethyl methacrylamide),
2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
N-(2-hydroxypropyl acrylamide), N-(2-hydroxypropyl methacrylamide),
polyethylene glycol monoacrylate, polyethylene glycol
monomethacrylate, N-(polyethylene glycol) monoacrylamide,
N-(polyethylene glycol) monomethacrylamide, methyl ether
polyethylene glycol monoacrylate, methyl ether polyethylene glycol
monomethacrylate, methyl ether N-(polyethylene glycol)
monoacrylamide, methyl ether N-(polyethylene glycol)
monomethacrylamide, polyethylene glycol diacrylate, polyethylene
glycol dimethacrylate, N,N-(polyethylene glycol) diacrylamide,
N,N-(polyethylene glycol) dimethacrylamide, 4-vinyl pyridine,
N-vinyl pyrrolidone, cyanoethyl acrylate, cyanoethyl methacrylate,
ethoxytriethylene glycol acrylate, ethoxytriethylene glycol
methacrylate, N-(ethoxytriethylene glycol) acrylamide,
N-(ethoxytriethylene glycol) methacrylamide, N,N-methylenebis
acrylamide, N,N-methylenebis methacrylamide, vinyl acetate, vinyl
chloride, vinyl acrylate, vinyl methacrylate, vinyl azlactone,
acrylonitrile, 2-acetamidoacrylic acid, methyl
2-acrylamido-2-methoxyacetate, styrene, benzyl acrylate, benzyl
methacrylate, N-(benzyl) acrylamide, N-(benzyl) methacrylamide,
cyclohexyl acrylate, cylcohexyl methacrylate, N-(cyclohexyl)
acrylamide, N-(cyclohexyl) methacrylamide, and
N-butylurethane-O-ethyl acrylate (commercially available as
CL-1039). In one embodiment, the polymerizable monomeric species is
selected from the group consisting of methyl acrylate, methyl
methacrylate, methacrylic acid, acrylamide, n-vinyl pyrrolidone,
N-butylurethane-O-ethyl acrylate, methyl ether polyethylene glycol
monomethacrylate, 2-hydroxyethyl methacrylate, and mixtures
thereof.
[0031] The present invention is more particularly described in the
following examples that are intended as illustrative only, as
numerous modifications and variations will be apparent to those
skilled in the art.
EXAMPLES
Example 1
[0032] A 12.8 pounds per gallon (ppg) water based spacer fluid
containing methyl methacrylate at a predetermined concentration was
obtained. A portion of the fluid was placed within a pressure
vessel containing a standard pressure gauge, and heated in a
boiling water bath. Pressure developed within until polymerization
proceeds to a sufficient level to start decreasing the pressure due
to shrinkage during the polymerization process. In addition,
several test tubes were charged with 10.0 mL (15.4 grams) of the
same fluid, and placed into a boiling water bath. At selected
intervals, a test tube was removed and quenched in an ice water
bath. Methyl alcohol (10.0 mL) was added, with the test tube shaken
for about 15 seconds to afford complete mixing. Within about 5
minutes, the solids settled out, leaving a clear to slightly opaque
supernatant on top. Centrifugation, although possible, was found to
be unnecessary. The supernatant contained methyl alcohol, water,
surfactant, and monomer. Two to three drops were analyzed using the
portable refractometer. For convenience, the last three digits of
the refractive index (1.3 YYY) were used for the graphical
representation depicted in FIG. 1. FIG. 2 shows the data after
mathematically converting the refractive index measurements to
percent conversion of methyl methacrylate to poly(methyl
methacrylate), and includes the pressure trace obtained from the
pressure vessel as well. This composite graph clearly shows that at
about 38% conversion, the pressure in the vessel has been totally
compensated for by the shrinkage obtained during
polymerization.
Example 2
[0033] An 11.0 pounds per gallon (ppg) water based spacer fluid
containing methyl methacrylate at a predetermined concentration was
obtained. Several test tubes were charged with 10.0 mL (13.2
grams), capped, and placed into a constant temperature water bath
at 50.degree. C. At selected intervals, a test tube was removed and
quenched in an ice water bath. Methyl alcohol (10.0 mL) was added,
with the test tube shaken for about 15 seconds to afford complete
mixing. Within about 5 minutes, the solids settled out, leaving a
clear to slightly opaque supernatant on top. Centrifugation,
although possible, was found to be unnecessary. The supernatant
contained methyl alcohol, water, surfactant, and monomer. Two to
three drops were analyzed using the portable refractometer. The
amount of the methyl methacrylate in the spacer fluid over a five
week period at elevated temperature was shown to be very stable, as
shown in FIG. 3. This graph also demonstrates the practical
accuracy of the method, that is, readings are consistent within
about +/-0.0003.
Example 3
[0034] The monomers listed in Table 1 were analyzed in a method
similar to Example 2: eleven parts (by weight) of the water based
spacer fluid was added to a sufficient number of test tubes to test
the monomers in Table 1 in duplicate. Two parts of the appropriate
monomer was added, with the addition of an azo-type free radical
initiator solution in water (0.4 parts of a 25 wt. % solution). A
duplicate set of blank control test tubes without monomer was
prepared. Each tube was shaken to dissolve and/or evenly distribute
the monomer within the spacer fluid. The first tube in each series
was not heated, but immediately treated with 10 mL methanol (no
polymerization), and shaken to afford complete mixing. The second
tube in each series was heated in a boiling water bath for 90
minutes, and, for the purposes of this invention, was assumed to
have complete polymerization. After quenching in an ice water bath,
each tube was treated with 10 mL methanol as before. The contents
generally settled out to form two layers, one barite rich layer,
and one supernatant containing the methanol soluble fraction.
Analysis with the refractometer provided refractive indices (R.I.)
of the monomeric methanolic supernatant (first tube in each
series), and the refractive indices of the polymerized methanolic
supernatant (second tube in each series). The data clearly
indicates the utility of the invention as shown by the last column
(the "dynamic range").
TABLE-US-00001 R.I. difference First Second (range- Monomer Tube
R.I. Tube R.I. three digits) Methyl methacrylate 1.3557 1.3470
0.0087 (87) Methyl acrylate 1.3545 1.3484 0.0061 (61) Methacrylic
acid 1.3576 1.3572 0.0004 (4) N-vinylpyrrolidone 1.3648 1.3620
0.0028 (28) N-butylurethane-O-ethyl acrylate 1.3591 1.3480 0.0111
(111) methyl ether polyethylene glycol 1.3597 1.3504 0.0093 (93)
monomethacrylate 2-hydroxyethyl methacrylate 1.3579 1.3496 0.0083
(83) acrylamide 1.3610 1.3479 0.0131 (131) Control (no monomer)
1.3477 1.3477 0.0000 (0)
[0035] The method in Example 2 to convert last three digits of
refractive index to % conversion to monomer:
100(%)/original refractive index-final refractive index=% per R.I.
unit (1)
(original refractive index-"found" refractive index at time
increment).times.(% per R.I. unit)=% conversion of monomer to
polymer (2) [0036] For example: 100/548-478=1.428, then at the 40
minute value of 518 the result is (548-518).times.1.428=42.8%
conversion of monomer to polymer
* * * * *