U.S. patent application number 12/777459 was filed with the patent office on 2010-09-02 for biocide for well stimulation and treatment fluids.
This patent application is currently assigned to KEMIRA CHEMICALS, INC.. Invention is credited to Carl Wilhelm Aften, Geoffrey Allen Monteith, Ronald Joe Starkey, II.
Application Number | 20100218950 12/777459 |
Document ID | / |
Family ID | 38895547 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100218950 |
Kind Code |
A1 |
Starkey, II; Ronald Joe ; et
al. |
September 2, 2010 |
BIOCIDE FOR WELL STIMULATION AND TREATMENT FLUIDS
Abstract
A well stimulation and or treatment fluid that includes water,
other additives, and a biocide consisting of
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount effective to
inhibit bacterial growth and minimize antagonistic reactions
between the biocide and other additives. Also disclosed are well
injection compositions, stimulations, squeezing, waterflood,
packing, cement compositions, and methods for cementing.
Inventors: |
Starkey, II; Ronald Joe;
(Canton, GA) ; Monteith; Geoffrey Allen; (Midland,
GA) ; Aften; Carl Wilhelm; (Marietta, GA) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Assignee: |
KEMIRA CHEMICALS, INC.
Kennesaw
GA
|
Family ID: |
38895547 |
Appl. No.: |
12/777459 |
Filed: |
May 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11779509 |
Jul 18, 2007 |
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12777459 |
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11497724 |
Aug 2, 2006 |
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11779509 |
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Current U.S.
Class: |
166/285 ;
106/18.33; 507/256 |
Current CPC
Class: |
C04B 28/02 20130101;
C09K 8/68 20130101; C09K 8/467 20130101; C09K 8/88 20130101; C09K
8/58 20130101; C04B 2103/67 20130101; C04B 2103/67 20130101; C04B
40/0028 20130101; C04B 2103/67 20130101; C04B 24/16 20130101; C04B
2103/67 20130101; C04B 2103/34 20130101; C04B 24/128 20130101; C09K
8/428 20130101; C04B 28/02 20130101; C09K 8/605 20130101 |
Class at
Publication: |
166/285 ;
507/256; 106/18.33 |
International
Class: |
E21B 33/00 20060101
E21B033/00; C09K 8/58 20060101 C09K008/58; C04B 24/16 20060101
C04B024/16 |
Claims
1. A method of recovering a production fluid from a subterranean
formation, comprising: displacing a well injection composition
through a wellbore down to the subterranean formation to force or
enhance the production fluid from the subterranean formation, the
well injection composition comprising an injection fluid and a
biocide comprising 3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an
amount effective to inhibit bacterial growth.
2. The method of claim 1, wherein the injection fluid comprises an
aqueous fluid.
3. The method of claim 1, wherein the injection fluid comprises
fresh water or salt water.
4. The method of claim 1, wherein the production fluid is oil and
the injection fluid is at least partially miscible with the
oil.
5. The method of claim 1, wherein displacing the well injection
composition through the wellbore down to the subterranean formation
to force or enhance the production fluid from the subterranean
formation defines a well injection process, a stimulation, a
squeeze process, a waterflood process, or a packing process.
6. A cement composition comprising: a cement; and a biocide
comprising 3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount
effective to inhibit bacterial growth.
7. The cement composition of claim 6, wherein the cement
composition is a squeeze cementing composition.
8. The cement composition of claim 6, further comprising a fluid
for making the cement composition flowable.
9. A method of cementing, comprising: injecting a cement
composition into a permeable zone of a wellbore, the cement
composition comprising a cement and a biocide comprising
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount effective to
inhibit bacterial growth; and allowing the cement composition to
set.
10. The method of claim 9, further comprising providing the cement
composition in dry form and combining the cement composition with a
fluid before said injecting.
11. The method of claim 9, wherein a cement sheath is located in an
annulus of the wellbore, and wherein a conduit is located inside
the cement sheath.
12. The method of claim 11, wherein the permeable zone is in the
cement sheath.
13. The method of claim 11, wherein the permeable zone is in the
conduit.
14. The method of claim 11, wherein the permeable zone is between
the cement sheath and the conduit.
15. The method of claim 11, wherein the set cement composition
substantially plugs the permeable zone.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 11/779,509, filed on Jul. 18, 2007; which is a
continuation-in-part application that relates to and claims the
benefit of priority to U.S. patent application Ser. No. 11/497,724,
filed on Aug. 22, 2006, all of which are incorporated herein by
reference in their entireties.
BACKGROUND
[0002] The present disclosure generally relates to biocides, and
more particularly, to the use of
3,5-dimethyl-1,3,5-thiadiazinane-2-thione (Thione) in gas and oil
field well stimulation and treatment fluids. The disclosure relates
to various forms of Thione including, but not limited to,
non-emulsified 3,5-dimethyl-1,3,5-thiadiazinane-2-thione (CB
Thione), an emulsified 3,5-dimethyl-1,3,5-thiadiazinane-2-thione
(WB Thione), and a dry
3,5-dimethyl-1,3,5-thiadiazinane-2-thione.
[0003] After a well is drilled into a subterranean geological
formation that contains oil, natural gas, and water, every effort
is made to maximize the production of the oil and/or gas. To
increase the permeability and flow of the oil and/or gas to the
surface, the drilled wells are often subjected to well stimulation.
Well stimulation generally refers to several post drilling
processes used to clean the wellbore, enlarge channels, and
increase pore space in the interval to be injected thus making it
possible for fluids to move more readily into the formation. In
addition, typical reservoir enhancement processes such as
waterflood need to utilize biocide as part of the waterflood
package.
[0004] A typical well or field treatment process generally includes
pumping specially engineered fluids at high pressure and rate into
the subterranean geological formation. The high-pressure fluid
(usually water with some specialty high viscosity fluid additives)
exceeds the rock strength and opens a fracture in the formation,
which can extend out into the geological formation for as much as
several hundred feet. Certain commonly used fracturing treatments
generally comprise a carrier fluid (usually water or brine) and a
polymer, which is also commonly referred to as a friction reducer.
Many well stimulation fluids will further comprise a proppant.
Other compositions used as fracturing fluids include water with
additives, viscoelastic surfactant gels, gelled oils, crosslinkers,
oxygen scavengers, and the like.
[0005] The well treatment fluid can be prepared by blending the
polymer with an aqueous solution (sometimes an oil-based or a
multi-phase fluid is desirable); often, the polymer is a solvatable
polysaccharide. The purpose of the polymer is generally to increase
the viscosity of the fracturing fluid that aids in the creation of
a fracture; and to thicken the aqueous solution so that solid
particles of proppant can be suspended in the solution for delivery
into the fracture.
[0006] The polymers used in well treatment fluids are subjected to
an environment conducive to bacterial growth and oxidative
degradation. The growth of the bacteria on polymers used in such
fluids can materially alter the physical characteristics of the
fluids. For example, bacterial action can degrade the polymer,
leading to loss of viscosity and subsequent ineffectiveness of the
fluids. Fluids that are especially susceptible to bacterial
degradation are those that contain polysaccharide and/or synthetic
polymers such as polyacrylamides, polyglycosans, carboxyalkyl
ethers, and the like. In addition to bacterial degradation, these
polymers are susceptible to oxidative degradation in the presence
of free oxygen. The degradation can be directly caused by free
oxygen or mediated by aerobic microorganisms. Thus, for example,
polyacrylamides are known to degrade to smaller molecular fragments
in the presence of free oxygen. Because of this, biocides and
oxygen scavengers are frequently added to the well treatment fluid
to control bacterial growth and oxygen degradation, respectively.
Desirably, the biocide is selected to have minimal or no
interaction with any of the components in the well stimulation
fluid. For example, the biocide should not affect fluid viscosity
to any significant extent and should not affect the performance of
oxygen scavengers contained within the fluid. The oxygen scavengers
are generally derived from bisulfite salts.
[0007] Other desirable properties for the biocide are (a) cost
effectiveness, e.g., cost per liter, cost per square meter treated,
and cost per year; (b) safety, e.g., personnel risk assessment (for
instance, toxic gases or physical contact), neutralization
requirements, registration, discharge to environment, and
persistence; (c) compatibility with system fluids, e.g.,
solubility, partition coefficient, pH, presence of hydrogen
sulfide, temperature, hardness, presence of metal ions or sulfates,
level of total dissolved solids; (d) compatibility with other
treatment chemicals, e.g., corrosion inhibitors, scale inhibitors,
demulsiflers, water clarifiers, well stimulation chemicals, and
polymers; and (e) handling, e.g., corrosiveness to metals and
elastomers, freeze point, thermal stability, and separation of
components.
[0008] Current well stimulation fluids generally employ either
glutaraldehyde (Glut) or tetra-kis-hydroxymethyl)-phosphonium
sulfate (THPS) to control bacterial contamination. Glutaraldehyde
can be problematic because it is hazardous to handle and has
environmental concerns. Moreover, it has been observed that Glut
can deleteriously affect the fluid viscosity of the well treatment
fluid at elevated temperatures; temperatures that are commonly
observed during use of the well treatment fluid. This can be
problematic in fracturing applications since the higher maintained
fluid viscosity down hole could hinder flow back. In addition, Glut
has been shown to negatively impact the behavior of the oxygen
scavenger.
[0009] With regard to THPS, although it has been shown to perform
better than Glut with respect to interaction with the oxygen
scavengers, THPS has been found to interact with the polymer and
limit viscosity development when added pre-inversion and
post-inversion. That is, THPS has been observed to interact with
the polymer during shear and significantly reduce fluid
viscosity.
[0010] Thus, there remains a need for a more versatile biocide for
use in well stimulation fluids that can effectively control
bacterial contamination and have minimal interaction with the
polymer and/or oxygen scavenger.
BRIEF SUMMARY
[0011] Well injection compositions and methods of using such
compositions are also disclosed. In one embodiment, a well
injection composition comprises: an injection fluid for removing a
production fluid from a subterranean formation; and a biocide
comprising 3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount
effective to inhibit bacterial growth. In an embodiment, a method
of recovering a production fluid from a subterranean formation
comprises: displacing a well injection composition through a
wellbore down to the subterranean formation to force the production
fluid from the subterranean formation, the well injection
composition comprising an injection fluid and a biocide comprising
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount effective to
inhibit bacterial growth.
[0012] Cement compositions and methods of using such compositions
are further disclosed. In one embodiment, a cement composition
comprises: a cement; and a biocide comprising
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount effective to
inhibit bacterial growth. In another embodiment, a method of
cementing comprises: injecting a cement composition into a
permeable zone of a wellbore, the cement composition comprising a
cement and a biocide comprising
3,5-dimethyl-1,3,5,-thiadiazinane-2-thione in an amount effective
to inhibit bacterial growth; and allowing the cement composition to
set.
[0013] The disclosure may be understood more readily by reference
to the following detailed description of the various features of
the disclosure and the examples included therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Referring now to the figures wherein the like elements are
numbered alike:
[0015] FIG. 1 graphically illustrates post inversion viscosity in
centipoise (cPs) as a function of time for polymer fluid samples
containing varying amounts of biocide relative to a control not
containing the biocide;
[0016] FIG. 2 graphically illustrates pre-inversion viscosity as a
function of time for polymer fluid samples containing 500 parts per
million of biocide relative to a control not containing the
biocide;
[0017] FIG. 3 graphically illustrates pre-inversion viscosity as a
function of time for polymer fluid samples containing 1,000 parts
per million of biocide relative to a control not containing the
biocide;
[0018] FIG. 4 graphically illustrates a bar graph of post inversion
viscosity as a function of time for polymer fluid samples heated at
a temperature of 180.degree. F. for defined period of times
containing 500 parts per million of biocide relative to a control
not containing the biocide;
[0019] FIG. 5 graphically illustrates oxygen reduction potential in
millivolts for polymer samples containing 120 parts per kilion of
sodium metabisulfite buffered to a pH of 6.4 and having 500 parts
per million of biocide;
[0020] FIG. 6 graphically illustrates percent friction reduction as
a function of time for various biocides including
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in a friction loop
apparatus;
DETAILED DESCRIPTION
[0021] The present disclosure is generally directed to the use of
3,5-dimethyl-1,3,5-thiadiazinane-2-thione (also commonly referred
to as "Thione") as a biocide in gas and oil well stimulations.
Surprisingly, relative to popular biocides currently used in well
stimulation fluids, 3,5-dimethyl-1,3,5-thiadiazinane-2-thione is
much more versatile and provides a reduced interference with
friction reducers in the well stimulation fluid, a reduced
interference with oxygen scavengers, and has minimal interaction
with friction reducers at elevated temperatures relative to
conventional biocides such as Glut or THPS. The
3,5-dimethyl-1,3,5-thiadiazinane-2-thione biocide can be used in an
aqueous solution (CB Thione) or can be added to the well treatment
fluid as an emulsified fluid (WB Thione) or as a dry product.
[0022] The well treatment fluid generally comprises at least one
polymer. Preferred classes of polymers are polysaccharides or
synthesized polymers. Suitable polymers include, but are not
intended to be limited to, galactomannan polymers and derivatized
galactomannan polymers; starch; xanthan gums; hydroxycelluloses;
hydroxyalkyl celluloses; polyvinyl alcohol polymers (such as
homopolymers of vinyl alcohol and copolymers of vinyl alcohol and
vinyl acetate); and polymers (such as homopolymers, copolymers, and
terpolymers) that are the product of a polymerization reaction
comprising one or more monomers selected from the group consisting
of vinyl pyrrolidone, 2-acrylamido-2-methylpropanesulfonic acid,
acrylic acid and acrylamide, methacrylic acid, styrene sulfonic
acid, acrylamide and other monomers currently used for oil well
treatment polymers, among others. Certain polyvinyl alcohol
polymers can be prepared by hydrolyzing vinyl acetate polymers.
Preferably the polymer is water-soluble. Specific examples of
polymers that can be used include, but are not intended to be
limited to hydrolyzed polyacrylamide, guar gum, hydroxypropyl guar
gum, carboxymethyl guar gum, carboxymethylhydroxypropyl guar gum,
hydroxyethyl cellulose, carboxymethylhydroxyethyl cellulose,
hydroxypropyl cellulose, copolymers of acrylic acid and acrylamide,
xanthan, starches, and mixtures thereof, among others.
[0023] The amount of 3,5-dimethyl-1,3,5-thiadiazinane-2-thione in
the well stimulation fluid will vary, generally depending on the
polymer employed, the conditions of the water and the extent of
prior bacterial manifestation, the time period of bacterial growth,
the general environment where the biocide will be used, and the
like. Thus, it is not possible to delineate a minimal amount,
however, one skilled in the art will be able to determine the
minimal amount with undue experimentation. There is no maximum
amount, although large excesses may not be desirable for economic
reasons.
[0024] The 3,5-dimethyl-1,3,5-thiadiazinane-2-thione can be added
directly as an emulsification, solid, or solution to the fluid used
to make the well stimulation fluid, to a concentrated polymer
solution, and/or may be made on a slug dose basis. The present
disclosure is not intended to be limited to a particular method for
making the well stimulation fluid.
[0025] Examples of bacteria to which the
3,5-dimethyl-1,3,5-thiadiazinane-2-thione is effective and are
commonly found in oil and gas field fluids and waters include, but
are not intended to be limited to, aerobic, anaerobic, and
facultative bacteria, sulfur reducing bacteria, acid producing
bacteria, and the like. Specific examples include, but are not
limited to, pseudomonad species, bacillus species, enterobacter
species, serratia species, clostridia species, and the like. It
should be noted that it is expected that the use of
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in the well stimulation
fluid will be effective to inhibit algae and fungi formation at the
same biocidal concentrations for bacterial effectiveness.
[0026] Well stimulation and completion (treatment) fluid
compositions of the present disclosure can further comprise other
additives. Additives are generally included to enhance the
stability of the fluid composition itself to prevent breakdown
caused by exposure to oxygen, temperature change, trace metals,
constituents of water added to the fluid composition, and to
prevent non-optimal crosslinking reaction kinetics. The choice of
components used in fluid compositions is dictated to a large extent
by the properties of the hydrocarbon-bearing formation on which
they are to be used. Such additives can be selected from the group
consisting of water, oils, salts (including organic salts),
crosslinkers, polymers, biocides, corrosion inhibitors and
dissolvers, pH modifiers (e.g., acids and bases), breakers, metal
chelators, metal complexors, antioxidants, wetting agents, polymer
stabilizers, clay stabilizers, scale inhibitors and dissolvers, wax
inhibitors and dissolvers, asphaltene precipitation inhibitors,
water flow inhibitors, fluid loss additives, chemical grouts,
diverters, sand consolidation chemicals, proppants, permeability
modifiers, viscoelastic fluids, gases (e.g., nitrogen and carbon
dioxide), and foaming agents.
[0027] For well stimulation, the fluid containing the
3,5-dimethyl-1,3,5-thiadiazinane-2-thione biocide can be injected
directly into the wellbore to react with and/or dissolve substances
affecting permeability; injected into the wellbore and into the
formation to react with and/or dissolve small portions of the
formation to create alternative flowpaths; or injected into the
wellbore and into the formation at pressures effective to fracture
the formation.
[0028] In an additional embodiment, the
3,5-dimethyl-1,3,5-thiadiazinane-2-thione can be employed as a
biocide in a well injection composition. The well injection
composition can comprise an injection fluid for removing a
production fluid such as oil from a subterranean formation and a
biocide comprising 3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an
amount effective to inhibit bacterial growth. The injection fluid
can be any fluid suitable for forcing the production fluid out of
the subterranean formation and into a production wellbore where it
can be recovered. For example, the injection fluid can comprise an
aqueous fluid such as fresh water or salt water (i.e., water
containing one or more salts dissolved therein), e.g., brine (i.e.,
saturated salt water) or seawater. The biocide described previously
in relation to well stimulation fluids is appropriate for this
application as well.
[0029] The foregoing well injection composition can be used in a
flooding operation (e.g., secondary flooding as opposed to a
primary recovery operation which relies on natural forces to move
the fluid) to recover a production fluid, e.g., oil, from a
subterranean formation. The flooding operation entails displacing
the well injection composition through an injection well (or wells)
down to the subterranean formation to force or drive the production
fluid from the subterranean formation to a production well (or
wells). The flooding can be repeated to increase the amount of
production fluid recovered from the reservoir. In subsequent
flooding operations, the injection fluid can be replaced with a
fluid that is miscible or partially miscible with the oil being
recovered.
[0030] The injection well can include a cement sheath or column
arranged in the annulus of a wellbore, wherein the annulus is
disposed between the wall of the wellbore and a conduit such as a
casing running through the wellbore. Thus, the well injection
composition can pass down through the casing into the subterranean
formation during flooding. The biocide present in the well
injection composition can serve to reduce bacterial growth on the
cement sheath and the conduit therein without significantly
affecting the materials with which it comes in contact, including
the components of the well injection composition.
[0031] In yet another embodiment, the
3,5-dimethyl-1,3,5-thiadiazinane-2-thione can be employed as a
biocide in a cement composition, particularly a cement composition
used for squeeze cementing. The cement composition can comprise a
cement and a biocide comprising
3,5-dimethyl-1,3,5-thiadiazinane-2-thione in an amount effective to
inhibit bacterial growth. The cement can be, for example, hydraulic
cement, which comprises calcium, aluminum, silicon, oxygen, and/or
sulfur, and which sets and hardens by reaction with water. Examples
of suitable hydraulic cements include but are not limited to
Portland cements, pozzolana cements, gypsum cements, high alumina
content cements, silica cements, high alkalinity cements, and
combinations comprising at least one of the foregoing cements. More
specific examples of cements are class A, C, G, and H Portland
cements. The cement composition can be stored in dry form until it
is desired to place it in a wellbore, making the cement composition
particularly useful in sub-zero condition. The cement composition
can be combined with a fluid for rendering it flowable when it is
desired to pump it into a wellbore. The fluid can comprise, for
example, fresh water, salt water such as brine or seawater, or a
combination comprising at least one of the foregoing types of
water.
[0032] As deemed appropriate by one skilled in the art, additional
additives may be included in the cement composition for improving
or changing its properties. Examples of such additives include but
are not limited to set retarders, fluid loss control additives,
defoamers, dispersing agents, set accelerators, and formation
conditioning agents. The additives can be pre-blended with the dry
cement composition before the addition of a fluid thereto.
Alternatively, the additives can be introduced to the cement
composition concurrent with or after the addition of a fluid
thereto.
[0033] The foregoing cement composition can be utilized in a
remedial cementing operation such as squeeze cementing, which is
performed after the primary cementing operation. In squeeze
cementing, the cement composition can be combined with an aqueous
solution and then forced under pressure into permeable zones
through which fluid can undesirably migrate in the wellbore.
Examples of such permeable zones include fissures, cracks,
fractures, streaks, flow channels, voids, high permeability
streaks, annular voids, and so forth. A permeable zone can be
present in the cement sheath residing in the annulu of the
wellbore, in the wall of the conduit inside the cement sheath,
and/or in a microannulus between the cement sheath and the conduit.
The transition time of the cement composition can be relatively
short such that the amount of gas migration into the composition is
limited. The cement composition is allowed to set within the
permeable zone to form an impermeable mass that plugs the zone and
prevents fluid from leaking therethrough. The biocide present in
the cement composition can serve to inhibit microbiological induced
corrosion of the cement sheath and the conduit therein without
significantly affecting the materials with which it comes in
contact, including the components of the cement composition. That
is, the biocide can attack bacteria present on the cement sheath
and the conduit to reduce the growth of the bacteria.
EXAMPLES
[0034] In the following examples, an in-house constructed Inversion
Loop was modified with a Grace M3500 viscometer for periodically
measuring fluid viscosity as a function of time. The ORP apparatus
included a HACH sensION pH meter with a combination ORP electrode.
In Example 7, a friction loop apparatus was employed
Example 1
[0035] In this example, the post inversion viscosity of a polymeric
fluid having a biocide at different concentrations was analyzed
relative to a control that did not include a biocide. The biocides
analyzed included 50% Glut, 35% THPS, 24% caustic based Thione (CB
Thione), and a 20% water based Thione (WB Thione). A 0.1% aqueous
stock solution of polyacrylamide-co-acrylic acid, was made and
allowed to age for about 30 minutes. For each of the samples
tested, 1,500 grams of the stock solution was first added to the
inversion loop, recirculated, and the viscosity measured. After 2
minutes, the biocide was added at an initial concentration of 250
parts per million (ppm) and allowed to recirculate for 2 minutes at
which time the viscosity was recorded. Additional 250 ppm
increments of the biocide were added and the viscosities measured
after recirculation in the inversion loop for an additional 2
minutes.
[0036] The test results are graphically illustrated in FIG. 1. As
shown, polymer shear is observed as a function of recirculation in
the Inversion Loop apparatus (see control). For post inversion,
both Glut and WB Thione exhibited minimal effect on viscosity, even
at the higher concentrations. CB Thione, exhibited a slight
reduction in polymer viscosity as a function of increasing
concentration whereas a significant viscosity reduction was
observed with THPS.
Example 2
[0037] In this example, pre-inversion viscosity was measured for
the various biocide/polymer fluids and control of Example 1, which
were prepared in accordance with Example 1. In those samples
containing the biocide, the biocide concentrations examined were
500 ppm and 1,000 ppm. The results are shown in FIGS. 2 and 3,
respectively.
[0038] The results clearly show that THPS interacts with the
polymer resulting in a significant decrease in viscosity. In
contrast, the Glut and the samples containing CB Thione and WB
Thione showed minimal interaction relative to the control sample.
Interestingly, the WB Thione exhibited an increase in viscosity
relative to the control. While not wanting to be bound by theory,
the components used to form the emulsion are believed to react with
or interact with the polymer.
Example 3
[0039] In this example, the effect of heat on the biocide/polymer
fluids and control of Example 1 was analyzed. THPS was not analyzed
because of its observed interaction at room temperature in the
earlier examples. For each of the samples that were tested, 500 ppm
of the biocide was added to 1,000 grams of the polyacrylamide stock
solution of Example 1. The samples were added to the inversion
loop, recirculated for 1 minute, and the viscosity measured. The
samples were then placed into an oven at 180.degree. F. for 4
hours, and were allowed to cool to room temperature (77.degree.
F.). Once the samples were at room temperature, the viscosity was
measured and then return to the oven for an additional 4 hours at
which the time sample was cooled to room temperature and the
viscosity measured. The results are shown in FIG. 4.
[0040] From the results above, it can be noted that polymer
viscosity degrades with heat over time. For each test, the initial
viscosity measurement shows only the effect of the biocide on the
polymer viscosity. CB Thione is the only one to give a significant
reduction from that of the control after the first heating cycle,
which was expected given the results seen in the previous
post-inversion viscosity testing. After four hours at temperature,
however, the viscosities of the control, CB Thione, and WB Thione
are essentially the same, while the viscosity of the Glut test
sample has maintained nearly all its viscosity. This same effect is
seen at the eight-hour mark, with the Glut sample showing only
slightly reduced viscosity. While not wanting to be bound by
theory, it is believed that the glutaraldehyde slightly crosslinked
the polymer at elevated temperature, thus allowing the polymer
viscosity to persist above that of the polymer alone. Reactions
between dialdehyde and acrylamide are quite well documented. This
effect could be considered problematic in fracturing applications
since the higher maintained viscosity down hole could potentially
hinder flow back.
Example 4
[0041] In this example, the effect of CB Thione, WB Thione, THPS
and Glut on the oxygen scavenger was examined. To a beaker
containing 500 milliliters of deionized water, a 120 ppm dose of
sodium metabisulfite (SMBS) was added and the pH and oxygen
reduction potential (ORP) were recorded. Once stabilized, phosphate
buffer was added to increase the pH to 6.4 and the ORP recorded.
Finally, the particular biocide tested was added at a concentration
of 500 ppm. The ORP was recorded initially and after a period of 10
minutes. The results are shown in FIG. 5.
[0042] From these results, it can be noted that there is a
significant difference in ORP response upon addition of each
respective biocide. ORP is an indication of a solution's ability to
oxidize or reduce another solution/species. Theoretically, the
lower the ORP, the higher the ratio of reduced species to oxidized
species. Glut does not significantly impact ORP upon initial
addition, and after 10 minutes of residence time the ORP actually
increases nearly to the level of the DI H.sub.2O alone. This would
indicate a negative impact on the bisulfite scavenger. The
reactions between aldehydes and bisulfite are well documented and
are often used for melting point determinations. Similar results
were observed with THPS. In contrast, upon addition of the CB
Thione, the ORP of the solution is lowered significantly. The lower
value given by the CB Thione solution would indicate a more
preferable environment for O.sub.2 scavenging to occur. WB Thione
also indicated a more preferable environment for O.sub.2
scavenging.
Example 5
[0043] In this example, a friction loop apparatus was employed to
assess the compatibility of biocide formulations with an anionic
friction reducer. The biocides analyzed included 50% Glut, 35%
THPS, 24% caustic based Thione (CB Thione), and a 20% water based
Thione (WB Thione).
[0044] A commercial anionic friction reducing polymer was dosed at
0.5 gallons per thousand gallons of water. The friction loop
determined the effect of the polymer on the differential pressure
across a 5 foot test section of 0.5'' nominal stainless steel pipe.
The friction loop was operated at a flow rate of 24 gallons per
minute, a temperature of about 85.degree. Fahrenheit, and a
Reynolds number of about 120,000. Differential pressure was
continually measured across the test section at one-second
intervals for a period of 10 minutes. The first minute of the test
was used to establish a baseline pressure drop. The friction
reducer was injected into the system 1:00 minute after the test was
started. The respective biocides were injected into the system at a
500 ppm dosage 3:00 minutes into the test, and an additional 500
ppm dosage was injected 5:00 minutes into the test.
[0045] The pressure drop data was used to calculate a percent
friction reduction in accordance with equation (1) below,
% FR = .DELTA. P solvent - .DELTA. P solution .DELTA. P solvent , (
1 ) ##EQU00001##
wherein % FR is the percent friction reduction,
.DELTA.P.sub.solvent is the pressure drop across the test section
for pure solvent (water), and .DELTA.P.sub.solution is the pressure
drop across the test section for the solution of water, friction
reducer, and biocide. The results are shown in FIG. 6.
[0046] In FIG. 6, a control was included where no biocide was
injected into the system. In samples where biocide was added, the
biocide injection points are represented by vertical lines at 30
seconds and 150 seconds, which correspond to times of 3:00 minutes
and 5:00 minutes after the initiation of the test. As shown in FIG.
6, the % FR data from 0 to 30 seconds represent the friction
reduction performance of the pure polymer solution, which increases
slightly with time due to continued inversion in the loop.
[0047] The introduction of 500 ppm of each respective biocide
sample had no negative effect on the performance of the friction
reducer. As shown in FIG. 6, after slight differences in inversion
from 30 to 90 seconds, the results of each experiment appear nearly
identical from 90 seconds to 120 seconds.
[0048] Additional biocide was introduced to bring the total biocide
loading level to 1000 ppm. The % FR results for WB Thione did not
significantly deviate from the performance of the control sample
during the 150 to 420 second time interval. Similarly, the % FR for
Glut remained even with that of the blank sample over the same time
interval. These data indicate that WB Thione and Glut do not have
an adverse impact on friction reducer performance at this dosage
range (1000 ppm).
[0049] The performance of the friction reducer in the presence of
CB Thione declines relative to the performance of the blank from
150 to 420 seconds. This effect is verified by comparing the % FR
data through the last 10 seconds of the test. These data indicate a
% FR of 46.7% for the control sample and 43.5% for the CB Thione,
respectively.
[0050] However, the introduction of the THPS biocide sample
resulted in severe performance degradation of the friction reducer.
After an initial drop in % FR, the friction reduction performance
plateaus, then continues to drop with increasing time. The final %
FR results were 46.7% for the control sample, and 27.8% for the
THPS sample. The results showed that the WB Thione and Glut had no
effect on the performance of the polymer at the prescribed dosage
amount. It was also shown that CB Thione had a relatively minor
detrimental effect on polymer performance when dosed at 1,000 ppm,
causing a 3.2% drop in absolute friction reduction. THPS caused a
19.9% decline in absolute friction reduction at a 1,000 ppm dosage,
which eliminated over 40% of the original friction reduction
capacity of the polymer.
Example 6
[0051] In this example, the biocidal effectiveness on sulfate
reducing bacteria (SRB) and acid producing bacteria (AB) for
biocide formulations containing CB Thione and WB Thione to Glut and
THPS was examined.
[0052] A one gallon sample was separated from a five gallon sample
of frac pond water for these studies. The frac pond water sample
included SRB and AB. Ten mL of a 10.sup.9 cfu/mL inoculum of SRB
grown in anaerobic API broth containing an O.sub.2 scavenger and 10
mL of a 10.sup.9 cfu/mL inoculum of AB grown in anaerobic phenol
red (anPR) broth containing an O.sub.2 scavenger were added to the
one gallon frac pond water sample, mixed well and allowed to
incubate for a period of time sufficient to achieve a desired
number of SRB and AB. All broth media for inoculum and serial
dilution counts in this study was made at 4% salinity to match the
salinity of the original frac pond water measured by total
dissolved solids testing. To increase nutrient value and to emulate
on-site friction reducing additives, a 30 weight % acrylic acid,
70% acrylamide copolymer was added to the inoculated gallon of frac
pond water sample at 300 ppm and then referred to as the spiked
frac pond water sample. The spiked sample was then divided into
99.0 g aliquots for testing the effect of various biocides at
various concentrations on the SRB and AB over a 180 day contact
time. One spiked aliquot would serve as the control sample to which
no biocide would be added. Challenges were made to all aliquots
using 0.5 mL of 10.sup.8 SRB and 0.5 mL of 10.sup.8 AB at 14, 28,
and 129 days contact time.
[0053] The biocides included a 20% water based Thione (WB Thione),
a 24% caustic based Thione (CB Thione), a 25% Glut, and a 35% THPS.
Stock biocide solutions of various concentrations were made from
these biocides as described below.
[0054] The WB Thione stock solutions were prepared by adding 3.0 g
of the biocide to 17.0 g of sterile distilled water to form an
intermediate solution, followed by combining each intermediate
solution with water in the amounts shown in Table 1 below to make
the descending concentrations as shown in Table 1.
TABLE-US-00001 TABLE 1 Stock WB Thione Intermediate Water Total
Solution Concentration Solution Added Amount Sample (ppm) (g) (g)
(g) AA 25000 1.67 8.33 10.00 AB 50000 3.33 6.67 10.00 AC 100000
6.67 3.33 10.00 AD 150000 20.00 0.00 20.00
[0055] The CB Thione stock solutions were prepared by adding 3.0 g
of the biocide to 17.0 g of sterile distilled water to form an
intermediate solution, followed by combining each intermediate
solution with water in the amounts shown in Table 2 below to make
the descending concentrations as shown in Table 2.
TABLE-US-00002 TABLE 2 Stock CB Thione Intermediate Water Total
Solution Concentration Solution Added Amount Sample (ppm) (g) (g)
(g) BA 25000 1.67 8.33 10.00 BB 50000 3.33 6.67 10.00 BC 100000
6.67 3.33 10.00 BD 150000 20.00 0.00 20.00
[0056] The Glut stock solutions were prepared by adding 1.0 g
biocide to 19.0 g of sterile distilled water to form an
intermediate solution, followed by combining each intermediate
solution with water in the amounts shown in Table 3 below to make
the descending concentrations as shown in Table 3.
TABLE-US-00003 TABLE 3 Stock Glut Intermediate Water Total Solution
Concentration Solution Added Amount Sample (ppm) (g) (g) (g) CA
5000 1.00 9.00 10.00 CB 10000 2.00 8.00 10.00 CC 20000 4.00 6.00
10.00 CD 50000 20.00 0.00 20.00
[0057] The THPS stock solutions were prepared by adding 1.0 g of
the biocide to 19.0 g of sterile distilled water to form an
intermediate solution, followed by combining each intermediate
solution with water in the amounts shown in Table 4 below to make
the descending concentrations as shown in Table 4.
TABLE-US-00004 TABLE 4 Stock THPS Intermediate Water Total Solution
Concentration Solution Added Amount Sample (ppm) (g) (g) (g) DA
5000 1.00 9.00 10.00 DB 10000 2.00 8.00 10.00 DC 20000 4.00 6.00
10.00 DD 50000 20.00 0.00 20.00
[0058] Next, 1 g of each biocide stock solution was added to the
appropriately labeled 99.0 g aliquot. Also, 1.0 g of sterile water
was added to the control aliquot. The concentrations of the
biocides present in each aliquot are provided below in Table 5.
TABLE-US-00005 TABLE 5 WB Thione CB Thione Glut THPS Control
Concentra- Concentra- Concentra- Concentra- (ppm) tion (ppm) tion
(ppm) tion (ppm) tion (ppm) 0 AA 250 BA 250 CA 50 DA 50 AB 500 BB
500 CB 100 DB 100 AC 1000 BC 1000 CC 200 DC 200 AD 1500 BD 1500 CD
500 DD 500
[0059] The aliquots were then incubated at room temperature in the
dark for the entire study, i.e., 6 months. During the 6 month
period, each aliquot was tested to determine the log quantity of
SRB and AB in each aliquot at each of the following contact times:
7 days, 14 days, 21 days, 28 days, 35 days, 42 days, 56 days, 90
days, 136 days, and 180 days. Using sterile syringes, this testing
was performed by serial diluting the aliquots into sealed 9.0 mL
anaerobic API broth and anaerobic PR broth bottles, both media
containing an O.sub.2 scavenger, in the appropriate labeled set of
SRB bottles (6 for each aliquot) and AB bottles (6 for each
aliquot) until a color change occurred, indicating the log quantity
of organisms present in each aliquot. The control sample was serial
diluted in 9 media bottles for a possible 10.sup.9 count. The SRB
bottles that did not undergo a color change were examined for 21
days, and the AB bottles that did not undergo a color change were
examined for 14 days. As shown in Tables 6-9 below, at 180 days
contact time, the control contained >10.sup.9 cfu/mL of both
types of bacteria, whereas the aliquots treated with WB Thione and
CB Thione biocides contained no or low levels of SRBs or ABs in
most cases and maintained that control through three substantial
challenges with native organisms. However, the aliquots treated
with Glut lost all control of SRB and AB after the 2.sup.nd
challenge on day 28 and the aliquots treated with THPS depending on
treatment concentration, lost all control of SRB and AB from 1 to
21 days contact time particularly after the 1.sup.st challenge on
day 14. Thus, the Thione proved to be much more effective at
inhibiting SRB and AB growth in frac water than the Glut and THPS
treatments.
[0060] Acid producing bacterial counts (AB) in the control
increased one log value from 10.sup.8 to >10.sup.9 over the
course of the 180-day study. Two versions of Thione chemistries
were tested against THPS and Glut with excellent comparable results
using the WB Thione and the CB Thione. Both short term and
especially long term control were exceptional with the Thione
chemistries in comparison with industry standards of Glut and THPS.
Control was also maintained with all concentrations of the Thione
chemistries through three substantial challenges with the exception
of 250 ppm CB Thione which failed after the third challenge at 129
days as compared with treatment at all levels of Glut and THPS
which failed with early challenges. In particular, treatment with
four levels of THPS failed after challenging once at 14 days
contact time and with all concentrations of Glut after challenging
twice at 14 and 28 days contact time. All testing stopped when
failure to control AB occurred.
[0061] Sulfate Reducing bacterial counts (SRB) in the control
decreased from 10.sup.9 to 10.sup.8 over the 180-day course of the
study. As above with AB, both formulations of Thione chemistries
provided exceptional control over both the short and long term for
SRB through 3 substantial challenges at all concentrations tested
except the 250 ppm treatment of CB Thione which lost control after
the third challenge on day 129. Comparatively, THPS failed
completely after challenging once at 14 days contact time at all
concentrations and Glut failed completely at all concentrations
after challenging twice at 14 and 28 days contact time. All testing
stopped when failure to control SRB occurred.
TABLE-US-00006 TABLE 6 Log 10 Anaerobic Sulfate Reducing
Bacteria/mL* Bioc. Conc. 7 14 21 28 35 42 56 90 136 180 in ppm "as
is" Days Days Days Days Days Days Days Days Days Days 0 ppm
.gtoreq.9 6 14 .gtoreq.9 .gtoreq.9 28 .gtoreq.9 .gtoreq.9 .gtoreq.9
.gtoreq.9 129 .gtoreq.9 .gtoreq.8 (Control) WB Thione DAY DAY DAY
250 ppm 0 1 CHALLENGE 0 0 CHALLENGE 0 0 0 0 CHALLENGE 1 0 (AA) AT
AT AT 500 ppm 0 0 10.sup.8 0 0 10.sup.9 0 0 0 0 10.sup.9 0 0 (AB)
1000 ppm 0 0 0 0 0 0 0 0 0 0 (AC) 1500 ppm 0 0 0 0 0 0 0 0 0 0 (AD)
CB Thione 250 ppm 1 1 0 0 0 0 0 0 .gtoreq.3 .gtoreq.3 (BA) 500 ppm
0 0 0 0 0 0 0 0 1 0 (BB) 1000 ppm 0 0 0 0 0 0 0 0 0 0 (BC) 1500 ppm
0 0 0 0 0 0 0 0 0 0 (BD)
TABLE-US-00007 TABLE 7 Log 10 Anaerobic Sulfate Reducing
Bacteria/mL* Bioc. Conc. 7 14 21 28 35 42 56 90 136 180 in ppm "as
is" Days Days 14 Days Days 28 Days Days Days Days Days Days Glut 50
ppm 0 0 DAY 0 0 DAY .gtoreq.3 .gtoreq.6 .gtoreq.6 .gtoreq.6
DISCONTINUED (CA) CHALLENGE CHALLENGE 100 ppm 0 0 AT 0 0 AT
.gtoreq.3 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (CB) 10.sup.8
10.sup.9 200 ppm 0 0 0 0 .gtoreq.3 .gtoreq.6 .gtoreq.6 .gtoreq.6
DISCONTINUED (CC) 500 ppm 0 0 0 0 .gtoreq.3 5 .gtoreq.6 .gtoreq.6
DISCONTINUED (CD) THPS 50 ppm .gtoreq.6 .gtoreq.6 .gtoreq.6
.gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (DA)
100 ppm 5 5 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6
.gtoreq.6 DISCONTINUED (DB) 200 ppm 0 0 .gtoreq.6 .gtoreq.6
.gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (DC) 500 ppm 0
0 4 3 3 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (DD) *Six serial
dilution bottles were used for each treated sample and 9 bottles
for the untreated control.
TABLE-US-00008 TABLE 8 Log 10 Anaerobic Acid Producing Bacteria/mL*
Bioc. Conc. 7 14 21 28 35 42 56 90 135 180 in ppm "as is" Days Days
Days Days Days Days Days Days Days Days 0 ppm 8 6 14 .gtoreq.9
.gtoreq.9 28 .gtoreq.9 .gtoreq.9 .gtoreq.9 .gtoreq.9 129 .gtoreq.9
.gtoreq.9 (Control) WB Thione DAY DAY DAY 250 ppm 2 1 CHALLENGE 1 1
CHALLENGE 1 0 1 0 CHALLENGE 2 1 (AA) AT AT AT 500 ppm 1 1 10.sup.9
0 0 10.sup.8 0 0 0 0 10.sup.6 0 0 (AB) 1000 ppm 0 0 0 0 0 0 0 0 0 0
(AC) 1500 ppm 0 0 0 0 0 0 0 0 0 0 (AD) CB Thione 250 ppm 1 1 1 1 1
1 1 1 .gtoreq.3* .gtoreq.3* (BA) 500 ppm 1 1 1 1 1 0 0 0 1 0 (BB)
1000 ppm 1 0 1 0 1 1 1 0 1 0 (BC) 1500 ppm 0 0 0 1 0 0 0 0 0 0 (BD)
*Dilutions were made to 10.sup.3 only
TABLE-US-00009 TABLE 9 Log 10 Anaerobic Acid Producing Bacteria/mL*
Bioc. Conc. 7 14 21 28 35 42 56 90 136 180 in ppm "as is" Days Days
14 Days Days 28 Days Days Days Days Days Days Glut 50 ppm 0 0 DAY 1
0 DAY .gtoreq.3 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (CA)
CHALLENGE CHALLENGE 100 ppm 0 0 AT 0 0 AT .gtoreq.3 .gtoreq.6
.gtoreq.6 .gtoreq.6 DISCONTINUED (CB) 10.sup.9 10.sup.8 200 ppm 0 1
0 0 .gtoreq.3 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (CC) 500
ppm 0 0 0 0 .gtoreq.3 4 .gtoreq.6 .gtoreq.6 DISCONTINUED (CD) THPS
50 ppm 5 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6
.gtoreq.6 .gtoreq.6 DISCONTINUED (DA) 100 ppm 5 5 .gtoreq.6
.gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 DISCONTINUED (DB)
200 ppm 1 0 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6 .gtoreq.6
.gtoreq.6 DISCONTINUED (DC) 500 ppm 0 0 4 3 4 3 .gtoreq.6 .gtoreq.6
DISCONTINUED (DD) *Six serial dilution bottles were used for each
treated sample and 9 bottles for the untreated control.
[0062] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to make and use the invention. The patentable
scope of the invention is defined by the claims, and may include
other examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims if they
have structural elements that do not differ from the literal
language of the claims, or if they include equivalent structural
elements with insubstantial differences from the literal languages
of the claims.
* * * * *