U.S. patent application number 14/560172 was filed with the patent office on 2015-03-26 for gas hydrate inhibitors and methods for making and using same.
The applicant listed for this patent is Clearwater International, LLC. Invention is credited to Olusegun Matthew Falana, Michael Morrow, Frank G. Zamora.
Application Number | 20150087561 14/560172 |
Document ID | / |
Family ID | 47559587 |
Filed Date | 2015-03-26 |
United States Patent
Application |
20150087561 |
Kind Code |
A1 |
Falana; Olusegun Matthew ;
et al. |
March 26, 2015 |
GAS HYDRATE INHIBITORS AND METHODS FOR MAKING AND USING SAME
Abstract
Nitrate brine compositions reduce hydrate formation in flowlines
under conditions conducive for hydrate formation in the absence of
the nitrate brines, where the nitrate brines include compatible
anti-corrosion system.
Inventors: |
Falana; Olusegun Matthew;
(Houston, TX) ; Morrow; Michael; (Larkspur,
CO) ; Zamora; Frank G.; (Fort Worth, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Clearwater International, LLC |
Houston |
TX |
US |
|
|
Family ID: |
47559587 |
Appl. No.: |
14/560172 |
Filed: |
December 4, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13348279 |
Jan 11, 2012 |
8932996 |
|
|
14560172 |
|
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|
|
Current U.S.
Class: |
507/102 ;
507/135; 507/202; 507/259 |
Current CPC
Class: |
C09K 2208/32 20130101;
C09K 2208/22 20130101; C09K 8/38 20130101; C09K 8/52 20130101 |
Class at
Publication: |
507/102 ;
507/135; 507/259; 507/202 |
International
Class: |
C09K 8/38 20060101
C09K008/38; C09K 8/52 20060101 C09K008/52 |
Claims
1. A downhole fluid composition comprising: a base fluid comprising
a nitrate brine, and an inhibiting amount of a corrosion system
including: at least one compatible anti-corrosion and/or
neutralization additive is selected from the group consisting of
mono carboxylic acids, dicarboxylic acids, poly carboxylic acids,
hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid,
sulfonic acids, sulfinyl acids, phosphoric acid, polyphosphoric
acid, and mixtures or combinations thereof, where the downhole
fluid comprises a drilling fluid, a completion fluid, or a
production fluid, where the base fluid reduces or inhibits
hydrocarbon gas hydrate formation under conditions conducive to
hydrocarbon gas hydrate formation in the downhole fluid, and where
the additives reduce or prevent corrosion by the base fluid.
2. The composition of claim 1, wherein the downhole fluid further
include: an effective amount of a foaming system and a gas to form
a foamed downhole fluid having desired foam properties, where the
foamed downhole fluid comprises a foamed drilling fluid, a foamed
completion fluid, or a foamed production fluid.
3. The composition of claim 1, wherein the nitrate brines are
selected from the group consisting of alkali metal nitrate brines,
alkaline earth metal nitrate brines, transition metal nitrate
brines, and mixtures or combinations thereof.
4. The composition of claim 3, wherein: the alkali metal nitrate
brines are selected from the group consisting of lithium nitrate
brines, sodium nitrate brines, potassium nitrate brines, rubidium
nitrate brines, cesium nitrate brines, and mixture or combinations
thereof, the alkaline earth metal nitrate brines are selected from
the group consisting of magnesium nitrate brines, calcium nitrate
brines, and mixture or combinations thereof, and the transition
metal nitrate brines are zinc nitrate brines.
5. The composition of claim 1, wherein: the mono-, di- and
polycarboxylic acids are selected from the group consisting of
saturated carboxy acids having from 1 to about 20 carbon atoms,
unsaturated carboxy acids having from about 2 to about 20 carbon
atoms, aromatic acids having from about 5 to about 30 carbon atoms,
saturated dicarboxy acids having from 1 to about 20 carbon atoms,
unsaturated dicarboxy acids having from about 2 to about 20 carbon
atoms, aromatic diacids having from about 5 to about 30 carbon
atoms, saturated polycarboxy acids having from 1 to about 20 carbon
atoms, unsaturated polycarboxy acids having from about 2 to about
20 carbon atoms, aromatic polyacids having from about 5 to about 30
carbon atoms, or mixtures and combinations thereof, and the
sulfonic acids include, without limitation, alkyl sulfonic acids,
alkenyl sulfonic acids, aryl sulfonic acids, where the alkyl groups
include 1 to about 20 carbon atoms, the alkenyl groups include 2 to
about 20 carbon atoms and the aryl groups include 5 to about 30
carbon atoms.
6. The composition of claim 1, wherein the corrosion system further
includes: a quaternary salt selected from the group consisting of
quaternary ammonium salts
(R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+A.sup.-), quaternary
phosphonium salts (R.sup.1R.sup.2R.sup.3R.sup.4P.sup.+A.sup.-),
amines (R.sup.1R.sup.2R.sup.3N), phosphines
(R.sup.1R.sup.2R.sup.3P), and mixtures or combinations thereof,
where the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different and are carbyl groups having between 1 and about 20
carbon atoms selected from the group consisting of saturated,
unsaturated, cyclic, acyclic, aromatic, or mixed carbyl groups and
sufficient hydrogen atoms to satisfy the valence, where one or more
carbon atoms may be replaced by a hetero atom or group selected
from oxygen, sulfur, amido, boron, or mixtures thereof, and one or
more of the hydrogen atoms can be replace by halogens, alkoxides,
or mixtures thereof, where A.sup.- is a counterion selected from
the group consisting of hydroxide ion (OH.sup.-), a halogen ion
including F.sup.-, Cl.sup.-, Br--, and I--, a sulfate ion
(SO.sub.4.sup.2-), a nitrate ion (NO.sub.3.sup.-), or mixtures
thereof.
7. A drilling fluid composition comprising: a base fluid comprising
a nitrate brine, and an inhibiting amount of a corrosion system
including: at least one compatible anti-corrosion and/or
neutralization additive is selected from the group consisting of
mono carboxylic acids, dicarboxylic acids, poly carboxylic acids,
hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid,
sulfonic acids, sulfinyl acids, phosphoric acid, polyphosphoric
acid, and mixtures or combinations thereof, where the base fluid
reduces or inhibits hydrocarbon gas hydrate formation under
conditions conducive to hydrocarbon gas hydrate formation in the
base fluid, and where the additives reduce or prevent corrosion by
the base fluid.
8. The composition of claim 7, wherein the drilling fluid further
include: an effective amount of a foaming system and a gas to form
a foamed drilling fluid having desired foam properties, where the
foamed downhole fluid comprises a foamed drilling fluid, a foamed
completion fluid, or a foamed production fluid.
9. The composition of claim 7, wherein the nitrate brines are
selected from the group consisting of alkali metal nitrate brines,
alkaline earth metal nitrate brines, transition metal nitrate
brines, and mixtures or combinations thereof.
10. The composition of claim 9, wherein: the alkali metal nitrate
brines are selected from the group consisting of lithium nitrate
brines, sodium nitrate brines, potassium nitrate brines, rubidium
nitrate brines, cesium nitrate brines, and mixture or combinations
thereof, the alkaline earth metal nitrate brines are selected from
the group consisting of magnesium nitrate brines, calcium nitrate
brines, and mixture or combinations thereof, and the transition
metal nitrate brines are zinc nitrate brines.
11. The composition of claim 7, wherein: the mono-, di- and
polycarboxylic acids are selected from the group consisting of
saturated carboxy acids having from 1 to about 20 carbon atoms,
unsaturated carboxy acids having from about 2 to about 20 carbon
atoms, aromatic acids having from about 5 to about 30 carbon atoms,
saturated dicarboxy acids having from 1 to about 20 carbon atoms,
unsaturated dicarboxy acids having from about 2 to about 20 carbon
atoms, aromatic diacids having from about 5 to about 30 carbon
atoms, saturated polycarboxy acids having from 1 to about 20 carbon
atoms, unsaturated polycarboxy acids having from about 2 to about
20 carbon atoms, aromatic polyacids having from about 5 to about 30
carbon atoms, or mixtures and combinations thereof, and the
sulfonic acids include, without limitation, alkyl sulfonic acids,
alkenyl sulfonic acids, aryl sulfonic acids, where the alkyl groups
include 1 to about 20 carbon atoms, the alkenyl groups include 2 to
about 20 carbon atoms and the aryl groups include 5 to about 30
carbon atoms
12. The composition of claim 7, wherein the corrosion system
further includes: a quaternary salt selected from the group
consisting of quaternary ammonium salts
(R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+A.sup.-), quaternary
phosphonium salts (R.sup.1R.sup.2R.sup.3R.sup.4P.sup.+A.sup.-),
amines (R.sup.1R.sup.2R.sup.3N), phosphines
(R.sup.1R.sup.2R.sup.3P), and mixtures or combinations thereof,
where the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different and are carbyl groups having between 1 and about 20
carbon atoms selected from the group consisting of saturated,
unsaturated, cyclic, acyclic, aromatic, or mixed carbyl groups and
sufficient hydrogen atoms to satisfy the valence, where one or more
carbon atoms may be replaced by a hetero atom or group selected
from oxygen, sulfur, amido, boron, or mixtures thereof, and one or
more of the hydrogen atoms can be replace by halogens, alkoxides,
or mixtures thereof, where A.sup.- is a counterion selected from
the group consisting of hydroxide ion (OH), a halogen ion including
F.sup.-, Cl.sup.-, Br--, and I--, a sulfate ion (SO.sub.4.sup.2-),
a nitrate ion (NO.sub.3.sup.-), or mixtures thereof.
13. A completion fluid composition comprising: a base fluid
comprising a nitrate brine, and an inhibiting amount of a corrosion
system including: at least one compatible anti-corrosion and/or
neutralization additive is selected from the group consisting of
mono carboxylic acids, dicarboxylic acids, poly carboxylic acids,
hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid,
sulfonic acids, sulfinyl acids, phosphoric acid, polyphosphoric
acid, and mixtures or combinations thereof, where the base fluid
reduces or inhibits hydrocarbon gas hydrate formation under
conditions conducive to hydrocarbon gas hydrate formation in the
completion fluid, and where the additives reduce or prevent
corrosion by the base fluid.
14. The composition of claim 13, wherein the completion fluid
further include: an effective amount of a foaming system and a gas
to form a foamed completion fluid having desired foam properties,
where the foamed downhole fluid comprises a foamed drilling fluid,
a foamed completion fluid, or a foamed production fluid.
15. The composition of claim 13, wherein the nitrate brines are
selected from the group consisting of alkali metal nitrate brines,
alkaline earth metal nitrate brines, transition metal nitrate
brines, and mixtures or combinations thereof.
16. The composition of claim 15, wherein: the alkali metal nitrate
brines are selected from the group consisting of lithium nitrate
brines, sodium nitrate brines, potassium nitrate brines, rubidium
nitrate brines, cesium nitrate brines, and mixture or combinations
thereof, the alkaline earth metal nitrate brines are selected from
the group consisting of magnesium nitrate brines, calcium nitrate
brines, and mixture or combinations thereof, and the transition
metal nitrate brines are zinc nitrate brines.
17. The composition of claim 13, wherein: the mono-, di- and
polycarboxylic acids are selected from the group consisting of
saturated carboxy acids having from 1 to about 20 carbon atoms,
unsaturated carboxy acids having from about 2 to about 20 carbon
atoms, aromatic acids having from about 5 to about 30 carbon atoms,
saturated dicarboxy acids having from 1 to about 20 carbon atoms,
unsaturated dicarboxy acids having from about 2 to about 20 carbon
atoms, aromatic diacids having from about 5 to about 30 carbon
atoms, saturated polycarboxy acids having from 1 to about 20 carbon
atoms, unsaturated polycarboxy acids having from about 2 to about
20 carbon atoms, aromatic polyacids having from about 5 to about 30
carbon atoms, or mixtures and combinations thereof, and the
sulfonic acids include, without limitation, alkyl sulfonic acids,
alkenyl sulfonic acids, aryl sulfonic acids, where the alkyl groups
include 1 to about 20 carbon atoms, the alkenyl groups include 2 to
about 20 carbon atoms and the aryl groups include 5 to about 30
carbon atoms.
18. The composition of claim 13, wherein the corrosion system
further includes: a quaternary salt selected from the group
consisting of quaternary ammonium salts
(R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+A.sup.-), quaternary
phosphonium salts (R.sup.1R.sup.2R.sup.3R.sup.4P.sup.+A.sup.-),
amines (R.sup.1R.sup.2R.sup.3N), phosphines
(R.sup.1R.sup.2R.sup.3P), and mixtures or combinations thereof,
where the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different and are carbyl groups having between 1 and about 20
carbon atoms selected from the group consisting of saturated,
unsaturated, cyclic, acyclic, aromatic, or mixed carbyl groups and
sufficient hydrogen atoms to satisfy the valence, where one or more
carbon atoms may be replaced by a hetero atom or group selected
from oxygen, sulfur, amido, boron, or mixtures thereof, and one or
more of the hydrogen atoms can be replace by halogens, alkoxides,
or mixtures thereof, where A.sup.- is a counterion selected from
the group consisting of hydroxide ion (OH), a halogen ion including
F.sup.-, Cl.sup.-, Br--, and I--, a sulfate ion (SO.sub.4.sup.2-),
a nitrate ion (NO.sub.3.sup.-), or mixtures thereof.
19. A production fluid composition comprising: a base fluid
comprising a nitrate brine, and an inhibiting amount of a corrosion
system including: at least one compatible anti-corrosion and/or
neutralization additive is selected from the group consisting of
mono carboxylic acids, dicarboxylic acids, poly carboxylic acids,
hydrochloric acid (HCl), hydrobromic acid (HBr), sulfuric acid,
sulfonic acids, sulfinyl acids, phosphoric acid, polyphosphoric
acid, and mixtures or combinations thereof, where the base fluid
reduces or inhibits hydrocarbon gas hydrate formation under
conditions conducive to hydrocarbon gas hydrate formation in the
production fluid, and where the additives reduce or prevent
corrosion by the base fluid.
20. The composition of claim 19, wherein the production fluid
further include: an effective amount of a foaming system and a gas
to form a foamed production fluid having desired foam properties,
where the foamed downhole fluid comprises a foamed drilling fluid,
a foamed completion fluid, or a foamed production fluid.
21. The composition of claim 19, wherein the nitrate brines are
selected from the group consisting of alkali metal nitrate brines,
alkaline earth metal nitrate brines, transition metal nitrate
brines, and mixtures or combinations thereof.
22. The composition of claim 21, wherein: the alkali metal nitrate
brines are selected from the group consisting of lithium nitrate
brines, sodium nitrate brines, potassium nitrate brines, rubidium
nitrate brines, cesium nitrate brines, and mixture or combinations
thereof, the alkaline earth metal nitrate brines are selected from
the group consisting of magnesium nitrate brines, calcium nitrate
brines, and mixture or combinations thereof, and the transition
metal nitrate brines are zinc nitrate brines.
23. The composition of claim 19, wherein: the mono-, di- and
polycarboxylic acids are selected from the group consisting of
saturated carboxy acids having from 1 to about 20 carbon atoms,
unsaturated carboxy acids having from about 2 to about 20 carbon
atoms, aromatic acids having from about 5 to about 30 carbon atoms,
saturated dicarboxy acids having from 1 to about 20 carbon atoms,
unsaturated dicarboxy acids having from about 2 to about 20 carbon
atoms, aromatic diacids having from about 5 to about 30 carbon
atoms, saturated polycarboxy acids having from 1 to about 20 carbon
atoms, unsaturated polycarboxy acids having from about 2 to about
20 carbon atoms, aromatic polyacids having from about 5 to about 30
carbon atoms, or mixtures and combinations thereof.
24. The composition of claim 19, wherein the corrosion system
further includes: a quaternary salt selected from the group
consisting of quaternary ammonium salts
(R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+A.sup.-), quaternary
phosphonium salts (R.sup.1R.sup.2R.sup.3R.sup.4P.sup.+A.sup.-),
amines (R.sup.1R.sup.2R.sup.3N), phosphines
(R.sup.1R.sup.2R.sup.3P), and mixtures or combinations thereof,
where the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different and are carbyl groups having between 1 and about 20
carbon atoms selected from the group consisting of saturated,
unsaturated, cyclic, acyclic, aromatic, or mixed carbyl groups and
sufficient hydrogen atoms to satisfy the valence, where one or more
carbon atoms may be replaced by a hetero atom or group selected
from oxygen, sulfur, amido, boron, or mixtures thereof, and one or
more of the hydrogen atoms can be replace by halogens, alkoxides,
or mixtures thereof, where A.sup.- is a counterion selected from
the group consisting of hydroxide ion (OM, a halogen ion including
F.sup.-, Cl.sup.-, Br--, and I--, a sulfate ion (SO.sub.4.sup.2-),
a nitrate ion (NO.sub.3.sup.-), or mixtures thereof.
Description
RELATED APPLICATIONS
[0001] This application is divisional of U.S. patent application
Ser. No. 13/348,279 filed 11 Jan. 2012 (Jan. 11, 2012)(Nov. 1,
2012).
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of this invention relates to methods for using
phosphate and/or nitrate brines to reduce hydrate formation in
flowlines under conditions conducive for hydrate formation in the
absence of the phosphate and/or nitrate brine. In certain
embodiments, the phosphate and/or nitrate brines may include
compatible anti-corrosion additives. 2. Description of the Related
Art
[0004] Gas hydrate is a solid comprising a mixture of water and
hydrocarbon gas such as methane. Such mixtures are predominantly
water with occluded gaseous hydrocarbons such as methane, ethylene,
propylene, etc., normally present in minor amounts. The hydrates
may also include other gas components or gas contaminants such as
carbon dioxide and hydrogen sulfide. Gas hydrate formation is
ubiquitous in offshore drilling for and transportation of resources
such as gas and/or crude oil, because subsea temperature and
pressure conditions are favorable for or conducive to hydrate
formation. In certain environments, the temperature is at or below
about 35.degree. F. Thus, wellheads, drilling and production annuli
or control lines may become plugged or blocked with an accumulation
of gas hydrate. Consequently, drilling fluids may lose their
functionality, because hydrate formation may lead to an imbalance
in composition of the fluid (less water than originally
formulated), increased loss of circulation due to the changes in
fluid properties, increased flow back, sudden exposure of the
fluids at well surface conditions, which may lead to implosions,
and great concern in flow-assurance, as well as real potential of
abandoning a well or halting an operation operation are problems
familiar to those knowledgeable in the art.
[0005] In prior art, gas hydrate is prevented or managed by a
number of different methods. One method involves the use of salts
and alcohols (glycols, methanol, etc.) (see, e.g., Sloan, E. D. et.
al., JPT, December 2009; pp 89-94) to lower a freezing point
temperature of the fluid. Other methods involve using low doses of
hydrate inhibitors capable of altering hydrate formation kinetics
(delaying the rate of hydrate formation) or capable of reducing or
preventing hydrate precipitation by keeping hydrate in solution,
so-called anti-agglomerants (see, e.g., Proceedings of the 6th ICGH
2008, Vancouver, BC, CA, Jul. 6-10, 2008). Other methods involve
managing hydrate agglomeration mechanically by shearing (see, e.g.,
U.S. Pat. No. 6,774,276; Published International Application No.
WO/2007/095399 & United States Published Application
2004/0129609). Other methods involve insulating and heating
pipelines to reduce hydrate formation (see, e.g., U.S. Pat. No.
6,070,417). Another method uses high cost organic brines that have
a low pour point temperature to reduce or inhibit hydrate formation
such as formate brines.
[0006] While there are many different methods to address hydrate
formation, there is still a need in the art for fluids that reduced
or inhibit hydrate formation under conditions conducive to hydrate
formation in the absence to the fluids and that are environmentally
benign and less costly than fluids known to reduce or inhibit
hydrate formation such as expensive formate brines.
SUMMARY OF THE INVENTION
[0007] Embodiments of the present invention provide methods for
inhibiting hydrate formation, where the methods include using a
phosphate brine and/or a nitrate brine as a base fluid in downhole
operations under conditions conducive for hydrate formation. In
certain embodiments, a fluid including a phosphate brine and/or a
nitrate brine may also include capable anti-corrosion additives
and/or neutralization additives. The fluid will also include other
components depending on the application to which the fluids are
being applied. For example, in the case of drilling fluids, the
fluids may include capable drilling additives such as foaming
agents for underbalanced or pressure managed drilling.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The invention can be better understood with reference to the
following detailed description together with the appended
illustrative drawings in which like elements are numbered the
same:
[0009] FIG. 1 depicts a plot of hydrate equilibrium curves showing
a phosphate brine and a nitrate brine compared to conventional
brines.
[0010] FIG. 2 depicts a hydrate dissociation point plot at the
point 63.1.degree. F. and 8,612 psig for a nitrate brine having a
SG of 1.35.
[0011] FIG. 3 depicts a hydrate dissociation point plot at the
point 57.8.degree. F. and 5,534 psig for a nitrate brine having a
SG of 1.35.
[0012] FIG. 4 depicts a hydrate dissociation point plot at the
point 49.9.degree. F. and 1,728 psig for a nitrate brine having a
SG of 1.35.
[0013] FIG. 5 depicts a hydrate dissociation point plot at the
point 65.8.degree. F. and 8,824 psig for a phosphate brine having a
SG of 1.78.
[0014] FIG. 6 depicts a hydrate dissociation point plot at the
point 64.7.degree. F. and 5,740 psig for a phosphate brine having a
SG of 1.78.
[0015] FIG. 7 depicts a hydrate dissociation point plot at the
point 63.2.degree. F. and 1,810 psig for a phosphate brine having a
SG of 1.78.
DEFINITIONS OF THE INVENTION
[0016] The term "substantially" means that the value or effect is
at least 80% of being complete. In certain embodiments, the term
means that the value of effect is at least 85% of being complete.
In certain embodiments, the term means that the value of effect is
at least 90% of being complete. In certain embodiments, the term
means that the value of effect is at least 95% of being complete.
In certain embodiments, the term means that the value of effect is
at least 99% of being complete.
[0017] The term "about" means that the value or effect is at least
90% of being complete. In certain embodiments, the term means that
the value of effect is at least 95% of being complete. In certain
embodiments, the term means that the value of effect is at least
99% of being complete.
[0018] The term "ppg" means pounds per gallon (lb/gal) and is a
measure of density.
[0019] The term "SG" means specific gravity.
[0020] The term "under-balanced and/or managed pressure drilling
fluid" means a drilling fluid having a hydrostatic density
(pressure) lower or equal to a formation density (pressure). For
example, if a known formation at 10,000 ft (True Vertical
Depth--TVD) has a hydrostatic pressure of 5,000 psi or 9.6 lbm/gal,
an under-balanced drilling fluid would have a hydrostatic pressure
less than or equal to 9.6 lbm/gal. Most under-balanced and/or
managed pressure drilling fluids include at least a density
reduction additive. Other additive many include a corrosion
inhibitor, a pH modifier and a shale inhibitor.
DETAILED DESCRIPTION OF THE INVENTION
[0021] The inventors have found that gas hydrate inhibiting fluids
can be formulated to reduce or inhibit hydrate formation under
conditions conducive for hydrate formation, where the fluids
include an effective amount of a phosphate and/or nitrate brine.
The brine reduces or inhibits hydrates formation. A small
concentration of a composition of this invention introduced into a
brine fluid changes a freezing point temperature of the brine fluid
eliminating the formation of hydrates. The fluids may be foamed or
unfoamed. For foamed fluid, an effective amount of a foaming system
and a gas is added to the fluid to form a foam having desired
properties.
[0022] Current teaching provides a novel non-halide brines designed
to lower a pour point temperature of a fluid rending the fluid
unsusceptible to hydrate formation. In addition, brine-compatible
corrosion inhibiting additives may be used when needed. Instead of
contending with highly expensive formate (sodium, potassium or
cesium) brines, sodium, potassium, calcium or zinc (or their
blends) phosphate brines or nitrate brines maybe used. As such,
activity of using the brine sources or systems has no significant
impact on the environment, because the brines are easy to handle
and maybe disposed indiscriminately. Unlike when alcohols,
amphipathics or oleophilic inhibitors are employed, brine-produced
fluid separation is facile.
SUITABLE REAGENTS
Phosphate Brines
[0023] Suitable phosphate brines for use in the present invention
include, without limitation, phosphoric acid brines, polyphosphoric
acid brines, alkali metal brines, alkaline earth metal phosphate
brines, transition metal phosphate brines, and mixtures or
combinations thereof. Exemplary examples alkali metal phosphate
brines include mono lithium hydrogen phosphate brines, mono
hydrogen phosphate brines, mono potassium hydrogen phosphate
brines, mono rubidium hydrogen phosphate brines, mono cesium
hydrogen phosphate brines, di-lithium hydrogen phosphate brines,
di-hydrogen phosphate brines, di-potassium hydrogen phosphate
brines, di-rubidium hydrogen phosphate brines, di-cesium hydrogen
phosphate brines, and mixture or combinations thereof. Exemplary
examples of alkaline earth metal phosphate brines include magnesium
phosphate brines, calcium hydrogen phosphate brines, and mixture or
combinations thereof. Exemplary examples of transition metal
phosphate brines include zinc phosphate brines, and mixture or
combinations thereof.
[0024] It should be recognized that if one wants to form a mixed
phosphate brine, then one would use a suitable hydrogen phosphate
and a suitable base. For example, if one wanted to prepare a
potassium-cesium mixed phosphate brine, then one could start with a
potassium hydrogen phosphate and cesium hydroxide or cesium
hydrogen phosphate and potassium hydroxide. One can also start with
cesium, potassium hydrogen phosphate and neutralize with either
potassium or cesium hydroxide depending on the brine to be
produced. It should also be recognized that the phosphate brines
can include more than two metals as counterions by using a mixture
of hydrogen phosphates and/or a mixture of bases.
Nitrate Brines
[0025] Suitable nitrate brines useful in the present invention
include, without limitation, alkali metal nitrate brines, alkaline
earth metal nitrate brines, transition metal nitrate brines, and
mixtures or combinations thereof. Exemplary examples of alkali
metal nitrate brines include lithium nitrate, sodium nitrate,
potassium nitrate, rubidium nitrate, cesium nitrate, and mixture or
combinations thereof. Exemplary examples of alkaline earth metal
nitrate brines include magnesium nitrates, calcium nitrates, and
mixture or combinations thereof. Exemplary examples of transition
metal nitrate brines include zinc nitrate brines, and mixture or
combinations thereof.
Brine Specific Corrosion Inhibitors
[0026] Suitable neutralizing agents for neutralizing phosphate
brines include, without limitation, acids, anhydrides, other
compounds capable of neutralizing basic phosphate brines, or
mixtures or combinations thereof. Suitable acids include, without
limitation, organic acids, organic acid anhydrides, inorganic
acids, inorganic acid anhydrides or mixtures and combinations
thereof. Exemplary acids include, without limitations, carboxylic
acids (mono, di or poly), halogen containing acids such as
hydrochloric acid (HCl), hydrobromic acid (HBr), etc., sulfur
containing acids such as sulfuric acid, sulfonic acids, sulfinyl
acids, etc., phosphoric containing acids such as phosphoric acid,
polyphosphoric acid, etc. or mixtures and combinations thereof.
Exemplary carboxylic acids include, without limitation, saturated
carboxy acids having from 1 to about 20 carbon atoms, unsaturated
carboxy acids having from about 2 to about 20 carbon atoms,
aromatic acids having from about 5 to about 30 carbon atoms,
saturated dicarboxy acids having from 1 to about 20 carbon atoms,
unsaturated dicarboxy acids having from about 2 to about 20 carbon
atoms, aromatic diacids having from about 5 to about 30 carbon
atoms, saturated polycarboxy acids having from 1 to about 20 carbon
atoms, unsaturated polycarboxy acids having from about 2 to about
20 carbon atoms, aromatic polyacids having from about 5 to about 30
carbon atoms, or mixtures and combinations thereof. Exemplary
sulfonic acids include, without limitation, alkyl sulfonic acids,
alkenyl sulfonic acids, aryl sulfonic acids, where the alkyl groups
include 1 to about 20 carbon atoms, the alkenyl groups include 2 to
about 20 carbon atoms and the aryl groups include 5 to about 30
carbon atoms. In all of these structures, one or more of the carbon
atoms may be replaced by hetero atoms including boron, nitrogen,
oxygen, sulfur, or mixtures thereof and one or more of the required
hydrogen atoms to complete the valency may be replaced by a halogen
including fluorine, chlorine, or bromine, a hydroxyl group, an
ether group, an amine, an amide, or mixtures thereof. Exemplary
anhydrides include, without limitation, anhydrides prepared from
one or more of the acids listed above. In certain embodiments, the
acids include methane sulfonic acid (Lutropur MSA--LMSA) from BASF
Corp. USA, benzoic acid from Sigma-Aldrich Co. USA, hydrochloric
acid, glycolic acid, formic acid, polyphosphoric acid, or mixtures
and combinations thereof.
[0027] Suitable quaternary salts and amine for use in the additive
systems as corrosion inhibitors of this invention include, without
limitation, quaternary ammonium salts
(R.sup.1R.sup.2R.sup.3R.sup.4N.sup.+A.sup.-), quaternary
phosphonium salts (R.sup.1R.sup.2R.sup.3R.sup.4P.sup.+A.sup.-),
amines (R.sup.1R.sup.2R.sup.3N), phosphines
(R.sup.1R.sup.2R.sup.3P), and mixtures or combinations thereof,
where the R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are the same or
different and are carbyl groups having between 1 and about 20
carbon atoms (saturated, unsaturated, cyclic, acyclic, aromatic, or
mixed) and sufficient hydrogen atoms to satisfy the valence, where
one or more carbon atoms may be replaced by a hetero atom or group
selected from oxygen, sulfur, amido, boron, or mixtures thereof,
and one or more of the hydrogen atoms can be replace by halogens,
alkoxides, or mixtures thereof and where A.sup.- is a counterion.
Exemplary examples of counterions include hydroxide (OH.sup.-),
halogens (F.sup.-, Cl.sup.-, Br--, I--), sulfate (SO.sub.4.sup.2-),
nitrate (NO.sub.3.sup.2-), other counterions or mixtures thereof.
Exemplary examples of quaternary and amines include other additive
such as CORSAF SF (CSF) available from Tetra Technologies, Inc.
USA, OxBan HB.TM. (OBHB) available from Tetra Technologies, Inc.
USA, CorrFoam.TM. 1 (CF-1) available from Weatherford
International, USA, Triaminononane Crude (TAN) available from NOVA
Molecular Technologies, Inc. USA and BARDAC.RTM. LF, a quaternary
biocides, available from Lonza Inc. Allendale, N.J.
[0028] Suitable bases include, without limitation, alkali metal
hydroxides, alkaline earth metal and mixtures or combinations
thereof. Exemplary examples include lithium hydroxide, sodium
hydroxide, potassium hydroxide, rubidium hydroxide, cesium
hydroxide, magnesium hydroxide and mixtures or combinations
thereof.
Suitable Drilling Fluid Components
[0029] Suitable aqueous base fluids includes, without limitation,
seawater, freshwater, saline water or such makeup system containing
up to about 30% crude oil.
[0030] Suitable foaming agents for use in this invention include,
without limitation, any foaming agent suitable for foaming aquesous
based drilling fluids. Exemplary examples of foaming agents
include, without limitation KleanFoam.TM., DuraFoam.TM.,
FMA-100.TM., TransFoam.TM. (all available from Weatherford
International) or mixture or combinations.
[0031] Suitable polymers for use in this invention include, without
limitation, any polymer soluble in the aqueous base fluid.
Exemplary polymers include, without limitation, a polymer
comprising units of one or more (one, two, three, four, five, . . .
, as many as desired) polymerizable salts of mono-olefins or
di-olefins. Exemplary examples includes, without limitation,
natural polymers (starch, hydroxymethyl cellulose, xanthan, guar,
etc.) and derivates; co-polymerizable monomers such as acrylates
(acrylic acid, methyl acrylate, ethyl acrylate, etc.),
methacrylates (methacrylic acid, methyl methacrylate, ethyl
methacrylate, etc), 2-acrylamindomethylpropane sulfonic acid,
vinylacetate, acrylamide, or the like, provided of course that the
resulting polymer is soluble in the water base fluid.
Gases
[0032] Suitable gases for foaming the foamable, ionically coupled
gel composition include, without limitation, nitrogen, carbon
dioxide, or any other gas suitable for use in formation fracturing,
or mixtures or combinations thereof.
Other Types of Corrosion Inhibitors
[0033] Suitable corrosion inhibitor for use in this invention
include, without limitation: quaternary ammonium salts e.g.,
chloride, bromides, iodides, dimethylsulfates, diethylsulfates,
nitrites, bicarbonates, carbonates, hydroxides, alkoxides, or the
like, or mixtures or combinations thereof; salts of nitrogen bases;
or mixtures or combinations thereof. Exemplary quaternary ammonium
salts include, without limitation, quaternary ammonium salts from
an amine and a quaternarization agent, e.g., alkylchlorides,
alkylbromide, alkyl iodides, alkyl sulfates such as dimethyl
sulfate, diethyl sulfate, etc., dihalogenated alkanes such as
dichloroethane, dichloropropane, dichloroethyl ether,
epichlorohydrin adducts of alcohols, ethoxylates, or the like; or
mixtures or combinations thereof and an amine agent, e.g.,
alkylpyridines, especially, highly alkylated alkylpyridines, alkyl
quinolines, C6 to C24 synthetic tertiary amines, amines derived
from natural products such as coconuts, or the like,
dialkylsubstituted methyl amines, amines derived from the reaction
of fatty acids or oils and polyamines, amidoimidazolines of DETA
and fatty acids, imidazolines of ethylenediamine, imidazolines of
diaminocyclohexane, imidazolines of aminoethylethylenediamine,
pyrimidine of propane diamine and alkylated propene diamine,
oxyalkylated mono and polyamines sufficient to convert all labile
hydrogen atoms in the amines to oxygen containing groups, or the
like or mixtures or combinations thereof. Exemplary examples of
salts of nitrogen bases, include, without limitation, salts of
nitrogen bases derived from a salt, e.g.: C1 to C8 monocarboxylic
acids such as formic acid, acetic acid, propanoic acid, butanoic
acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid,
2-ethylhexanoic acid, or the like; C2 to C12 dicarboxylic acids, C2
to C12 unsaturated carboxylic acids and anhydrides, or the like;
polyacids such as diglycolic acid, aspartic acid, citric acid, or
the like; hydroxy acids such as lactic acid, itaconic acid, or the
like; aryl and hydroxy aryl acids; naturally or synthetic amino
acids; thioacids such as thioglycolic acid (TGA); free acid forms
of phosphoric acid derivatives of glycol, ethoxylates, ethoxylated
amine, or the like, and aminosulfonic acids; or mixtures or
combinations thereof and an amine, e.g.: high molecular weight
fatty acid amines such as cocoamine, tallow amines, or the like;
oxyalkylated fatty acid amines; high molecular weight fatty acid
polyamines (di, tri, tetra, or higher); oxyalkylated fatty acid
polyamines; amino amides such as reaction products of carboxylic
acid with polyamines where the equivalents of carboxylic acid is
less than the equivalents of reactive amines and oxyalkylated
derivatives thereof; fatty acid pyrimidines; monoimidazolines of
EDA, DETA or higher ethylene amines, hexamethylene diamine (HMDA),
tetramethylenediamine (TMDA), and higher analogs thereof;
bisimidazolines, imidazolines of mono and polyorganic acids;
oxazolines derived from monoethanol amine and fatty acids or oils,
fatty acid ether amines, mono and bis amides of
aminoethylpiperazine; GAA and TGA salts of the reaction products of
crude tall oil or distilled tall oil with diethylene triamine; GAA
and TGA salts of reaction products of dimer acids with mixtures of
poly amines such as TMDA, HMDA and 1,2-diaminocyclohexane; TGA salt
of imidazoline derived from DETA with tall oil fatty acids or soy
bean oil, canola oil, or the like; or mixtures or combinations
thereof.
Other Additives
[0034] The drilling fluids of this invention can also include other
additives as well such as scale inhibitors, carbon dioxide control
additives, paraffin control additives, oxygen control additives, or
other additives.
Scale Control
[0035] Suitable additives for Scale Control and useful in the
compositions of this invention include, without limitation:
Chelating agents, e.g., Na.sup.+, K.sup.+ or NH.sub.4.sup.+ salts
of EDTA; Na, K or NH.sub.4.sup.+ salts of NTA; Na.sup.+, K.sup.+ or
NH.sub.4.sup.+ salts of Erythorbic acid; Na.sup.+, K.sup.+ or
NH.sub.4.sup.+ salts of thioglycolic acid (TGA); Na.sup.+, K.sup.+
or NH.sub.4.sup.+ salts of Hydroxy acetic acid; Na.sup.+, K.sup.+
or NH.sub.4.sup.+ salts of Citric acid; Na.sup.+, K.sup.+ or
NH.sub.4.sup.+ salts of Tartaric acid or other similar salts or
mixtures or combinations thereof. Suitable additives that work on
threshold effects, sequestrants, include, without limitation:
Phosphates, e.g., sodium hexamethylphosphate, linear phosphate
salts, salts of polyphosphoric acid, Phosphonates, e.g., nonionic
such as HEDP (hydroxythylidene diphosphoric acid), PBTC
(phosphoisobutane, tricarboxylic acid), Amino phosphonates of: MEA
(monoethanolamine), NH.sub.3, EDA (ethylene diamine),
Bishydroxyethylene diamine, Bisaminoethylether, DETA
(diethylenetriamine), HMDA (hexamethylene diamine), Hyper
homologues and isomers of HMDA, Polyamines of EDA and DETA,
Diglycolamine and homologues, or similar polyamines or mixtures or
combinations thereof; Phosphate esters, e.g., polyphosphoric acid
esters or phosphorus pentoxide (P.sub.2O.sub.5) esters of: alkanol
amines such as MEA, DEA, triethanol amine (TEA),
Bishydroxyethylethylene diamine; ethoxylated alcohols, glycerin,
glycols such as EG (ethylene glycol), propylene glycol, butylene
glycol, hexylene glycol, trimethylol propane, pentaerythritol,
neopentyl glycol or the like; Tris & Tetra hydroxy amines;
ethoxylated alkyl phenols (limited use due to toxicity problems),
Ethoxylated amines such as monoamines such as MDEA and higher
amines from 2 to 24 carbons atoms, diamines 2 to 24 carbons carbon
atoms, or the like; Polymers, e.g., homopolymers of aspartic acid,
soluble homopolymers of acrylic acid, copolymers of acrylic acid
and methacrylic acid, terpolymers of acylates, AMPS, etc.,
hydrolyzed polyacrylamides, poly malic anhydride (PMA); or the
like; or mixtures or combinations thereof.
Carbon Dioxide Neutralization
[0036] Suitable additives for CO.sub.2 neutralization and for use
in the compositions of this invention include, without limitation,
MEA, DEA, isopropylamine, cyclohexylamine, morpholine, diamines,
dimethylaminopropylamine (DMAPA), ethylene diamine, methoxy
proplyamine (MOPA), dimethylethanol amine, methyldiethanolamine
(MDEA) & oligomers, imidazolines of EDA and homologues and
higher adducts, imidazolines of aminoethylethanolamine (AEEA),
aminoethylpiperazine, aminoethylethanol amine, di-isopropanol
amine, DOW AMP-90.TM., Angus AMP-95, dialkylamines (of methyl,
ethyl, isopropyl), mono alkylamines (methyl, ethyl, isopropyl),
trialkyl amines (methyl, ethyl, isopropyl), bishydroxyethylethylene
diamine (THEED), or the like or mixtures or combinations
thereof.
Paraffin Control
[0037] Suitable additives for Paraffin Removal, Dispersion, and/or
paraffin Crystal Distribution include, without limitation:
Cellosolves available from DOW Chemicals Company; Cellosolve
acetates; Ketones; Acetate and Formate salts and esters;
surfactants composed of ethoxylated or propoxylated alcohols, alkyl
phenols, and/or amines; methylesters such as coconate, laurate,
soyate or other naturally occurring methylesters of fatty acids;
sulfonated methylesters such as sulfonated coconate, sulfonated
laurate, sulfonated soyate or other sulfonated naturally occurring
methylesters of fatty acids; low molecular weight quaternary
ammonium chlorides of coconut oils soy oils or C.sub.10 to C.sub.24
amines or monohalogenated alkyl and aryl chlorides; quanternary
ammonium salts composed of disubstituted (e.g., dicoco, etc.) and
lower molecular weight halogenated alkyl and/or aryl chlorides;
gemini quaternary salts of dialkyl (methyl, ethyl, propyl, mixed,
etc.) tertiary amines and dihalogenated ethanes, propanes, etc. or
dihalogenated ethers such as dichloroethyl ether (DCEE), or the
like; gemini quaternary salts of alkyl amines or amidopropyl
amines, such as cocoamidopropyldimethyl, bis quaternary ammonium
salts of DCEE; or mixtures or combinations thereof. Suitable
alcohols used in preparation of the surfactants include, without
limitation, linear or branched alcohols, specially mixtures of
alcohols reacted with ethylene oxide, propylene oxide or higher
alkyleneoxide, where the resulting surfactants have a range of
HLBs. Suitable alkylphenols used in preparation of the surfactants
include, without limitation, nonylphenol, decylphenol,
dodecylphenol or other alkylphenols where the alkyl group has
between about 4 and about 30 carbon atoms. Suitable amines used in
preparation of the surfactants include, without limitation,
ethylene diamine (EDA), diethylenetriamine (DETA), or other
polyamines. Exemplary examples include Quadrols, Tetrols, Pentrols
available from BASF. Suitable alkanolamines include, without
limitation, monoethanolamine (MEA), diethanolamine (DEA), reactions
products of MEA and/or DEA with coconut oils and acids.
Oxygen Control
[0038] The introduction of water downhole often is accompanied by
an increase in the oxygen content of downhole fluids due to oxygen
dissolved in the introduced water. Thus, the materials introduced
downhole must work in oxygen environments or must work sufficiently
well until the oxygen content has been depleted by natural
reactions. For system that cannot tolerate oxygen, then oxygen must
be removed or controlled in any material introduced downhole. The
problem is exacerbated during the winter when the injected
materials include winterizers such as water, alcohols, glycols,
Cellosolves, formates, acetates, or the like and because oxygen
solubility is higher to a range of about 14-15 ppm in very cold
water. Oxygen can also increase corrosion and scaling. In CCT
(capillary coiled tubing) applications using dilute solutions, the
injected solutions result in injecting an oxidizing environment
(O.sub.2) into a reducing environment (CO.sub.2, H.sub.2S, organic
acids, etc.).
[0039] Options for controlling oxygen content includes: (1)
de-aeration of the fluid prior to downhole injection, (2) addition
of normal sulfides to product sulfur oxides, but such sulfur oxides
can accelerate acid attack on metal surfaces, (3) addition of
erythorbates, ascorbates, diethylhydroxyamine or other oxygen
reactive compounds that are added to the fluid prior to downhole
injection; and (4) addition of corrosion inhibitors or metal
passivation agents such as potassium (alkali) salts of esters of
glycols, polyhydric alcohol ethyloxylates or other similar
corrosion inhibitors. Exemplary examples oxygen and corrosion
inhibiting agents include mixtures of tetramethylene diamines,
hexamethylene diamines, 1,2-diaminecyclohexane, amine heads, or
reaction products of such amines with partial molar equivalents of
aldehydes. Other oxygen control agents include salicylic and
benzoic amides of polyamines, used especially in alkaline
conditions, short chain acetylene diols or similar compounds,
phosphate esters, borate glycerols, urea and thiourea salts of
bisoxalidines or other compound that either absorb oxygen, react
with oxygen or otherwise reduce or eliminate oxygen.
Salt Inhibitors
[0040] Suitable salt inhibitors for use in the fluids of this
invention include, without limitation, Na Minus Nitrilotriacetamide
available from Clearwater International, LLC of Houston, Texas.
EXPERIMENTS OF THE INVENTION
Introduction
[0041] In preparation for this hydrate dissociation evaluation, two
brine solutions were submitted to Intertek Westport Technology
Center, Houston, ex.X USA. Each fluid was then evaluated for
hydrate dissociation temperatures at varying pressures using a
synthetic gas supplied by Intertek Westport (Green Canyon Gas).
These tests were performed in a high pressure Autoclave mixing
cell.
Test Procedures
[0042] Approximately 175 mL of a test fluid were poured into an
open Autoclave cell. The cell was sealed, evacuated, and purged
using the test gas to remove the possibility of interference due to
air contamination. The pressure was increased to test conditions.
The fluid was then allowed to become gas saturate with mixing. Upon
completion of the saturation process, the pressure was shut in and
the cell temperature was reduced at approximately 10.degree. F. per
hour to minimum test conditions. The temperature was then
maintained at minimum test conditions for an extended period of
time to ensure a significant amount of hydrate formation had
occurred. A temperature ramp is conducted back up to the initial
starting temperature at approximately 6.degree. F. per hour.
Temperature and pressure data were collected using a data
acquisition system. Three dissociation points were measured on each
sample using this procedure at varying pressures to define the
hydrate equilibrium curves.
[0043] Table I list the composition of the test gas.
TABLE-US-00001 TABLE I Test Gas Composition ID Component Mole %
N.sub.2 Nitrogen 0.14 C.sub.1 Methane 87.48 C.sub.2 Ethane 7.58
C.sub.3 Propane 3.08 i-C.sub.4 Isobutane 0.51 n-C.sub.4 N-Butane
0.80 i-C.sub.5 Isopentane 0.20 C.sub.5 Pentane 0.20
[0044] Table II tabulates the hydrate equilibrium test results for
a nitrate brine and a phosphate brine.
TABLE-US-00002 TABLE II Hydrate Equilibrium Curve by High Pressure
Autoclave Method Nitrate (K.sub.2NO.sub.3) Brine Phosphate
(K.sub.2HPO.sub.4) Brine SG = 1.35 SG = 1.78 Temp (.degree. F.)
Press (psig) Temp (.degree. F.) Press (psig) 63.1 8,612 65.8 8,824
57.8 5,534 64.7 5,740 49.9 1,728 63.2 1,810
[0045] Referring to FIG. 1, a plot of hydrate equilibrium curves
for seven commercial hydrate inhibitors are shown along with the
three point curves for a nitrate brine and a phosphate brine of
this invention. The nitrate brine is a potassium nitrate
(KNO.sub.3) brine having an SG of 1.35. The phosphate brine is a
dipotassium hydrogen phosphate (K.sub.2HPO.sub.4) brine having an
SG of 1.78. The curves show that the nitrate and phosphate brines
behave similar to zinc bromide, formate and sodium chloride brines
as opposed to calcium chloride and calcium bromide brines and
organic hydrate inhibitors monoethylene glycol (MEG) and
methanol.
[0046] Referring to FIG. 2, a plot of a hydrate dissociation point
for the nitrate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at
63.1.degree. F. and 8,612 psig.
[0047] Referring to FIG. 3, a plot of a hydrate dissociation point
for the nitrate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at
57.8.degree. F. and 5,534 psig.
[0048] Referring to FIG. 4, a plot of a hydrate dissociation point
for the nitrate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at 49.9
.degree. F. and 1,728 psig.
[0049] Referring to FIG. 5, a plot of a hydrate dissociation point
for the phosphate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at
65.8.degree. F. and 8,824 psig.
[0050] Referring to FIG. 6, a plot of a hydrate dissociation point
for the phosphate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at
64.7.degree. F. and 5,740 psig.
[0051] Referring to FIG. 7, a plot of a hydrate dissociation point
for the phosphate brine of this invention using the High Pressure
Autoclave Method to determine hydrate equilibrium curve at
63.2.degree. F. and 1,810 psig.
[0052] The data presented in the tables and figures clearly
demonstrates that the phosphate and nitrate brines are ideal
candidates for preparing fluid for use under condition conducive
for hydrate formation. The phosphate and nitrate brines show
hydrate equilibrium curves similar to zinc bromide, potassium
formate and sodium chloride brines, which are currently used as
hydrate inhibitors. The phosphate and nitrate brines are lower cost
and are relatively non-corrosive. In certain embodiments, the
brines may include compatible anti-corrosion additives and/or
neutralization additives to further reduce any corrosive propensity
of the brines. The phosphate and nitrate brines of this invention
may be added to drilling fluids, foamed drilling fluids, completion
fluids, foamed completion fluids, production fluid or foamed
production fluids at concentration sufficient to reduce or inhibit
hydrate formation. Additionally, the drilling, completion or
production fluids, foamed or unfoamed, may use the phosphate and
nitrate brines of this invention as the base fluid.
[0053] All references cited herein are incorporated by reference.
Although the invention has been disclosed with reference to its
preferred embodiments, from reading this description those of skill
in the art may appreciate changes and modification that may be made
which do not depart from the scope and spirit of the invention as
described above and claimed hereafter.
* * * * *