Chemistry of hydrocarbon compounds – Hydrate or production thereof
Reexamination Certificate
2001-02-20
2003-07-22
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Hydrate or production thereof
C585S002000, C585S004000, C585S950000, C095S153000
Reexamination Certificate
active
06596911
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and a composition thereof for inhibiting the formation of hydrocarbon hydrates. This invention particularly related to a method and a composition thereof for inhibiting the formation of hydrocarbon hydrates during the production of oil and gas.
2. Background of the Invention
A number of hydrocarbons, especially lower-boiling light hydrocarbons, in formation fluids or natural gas are known to form hydrates with the water present in the system under a variety of conditions—particularly at a combination of lower temperature and higher pressure. The hydrates usually exist in solid forms that are essentially insoluble in the fluid itself. As a result, any solids in a formation fluid or natural gas liquid are at least a nuisance for production, handling and transport of the same. If the hydrate solids (or crystals) are concentrated enough, large enough themselves, and/or forming large agglomerates, it is not uncommon for them to cause plugging and/or blockage of pipelines or transfer lines or other conduits, valves and/or safety devices and/or other equipment, resulting in shutdown, loss of production and risk of explosion or unintended release of hydrocarbons into the environment either on-land or off-shore. Accordingly, hydrocarbon hydrates have been of substantial interest as well as concern to many industries, particularly the petroleum and natural gas industries.
Typically, the hydrocarbon hydrates are considered to be clathrates, also referred to as inclusion compounds. Clathrates are formed between a host molecule and a guest molecule. A hydrocarbon hydrate generally has crystals formed by having water host molecules surrounding the hydrocarbon guest molecules. The smaller or lower-boiling hydrocarbon molecules, particularly C
1
(methane) to C
4
hydrocarbons and their mixtures, tend to have more serious problems because it is believed that their hydrate or clathrate crystals are easier to form. For instance, it is believed that ethane would form hydrates at as high as 4° C. at a pressure of about 1 MPa. If the pressure is about 3 MPa, ethane hydrates can form at as high a temperature as 14° C. Even certain non-hydrocarbons such as carbon dioxide and hydrogen sulfide also are known to form hydrates under certain conditions.
There are two broad approaches to overcome or control the hydrocarbon hydrate problems, namely the thermodynamic approach and the kinetic approach. For the thermodynamic approach, there are a number of reported or attempted methods, including water removal, increasing temperature, decreasing pressure, addition of “antifreeze” to the fluid and/or a combination of these. The kinetic approach generally attempts (a) to prevent the smaller hydrocarbon hydrate crystals from agglomerating into larger ones; (b) to inhibit the hydrocarbon hydrates from being formed in the first place; (c) to slow down crystal formation or growth under a particular set of conditions; and/or a certain combination.
Efforts to control hydrates have included use of different materials as inhibitors. For instance, U.S. Pat. Nos. 5,460,728 and 5,648,575 disclose a number of onium compounds with at least four carbon substituents which are used to inhibit the plugging of conduits by gas hydrates. U.S. Pat. No. 5,880,319 discloses additives such as polymers with lactam rings to control clathrate hydrates in fluid systems.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a method for inhibiting formation of hydrocarbon hydrates, the method comprising: providing a mixture comprising water and a hydrocarbon; and contacting a composition comprising a first amount of an onium compound and a second amount of an amine salt with the mixture under conditions effective to form the hydrocarbon hydrates in the absence of the composition, wherein the first amount of the onium compound and the second amount of the amine salt in the composition are effective in inhibiting the formation of the hydrocarbon hydrates under the conditions.
In another aspect, the present invention is a method for inhibiting formation of hydrocarbon hydrates, the method comprising: providing a mixture comprising water and a hydrocarbon; and contacting a composition comprising a first amount of an onium compound, a second amount of an amine salt and a third amount of a solvent with the mixture under conditions effective to form the hydrocarbon hydrates in the absence of the composition, wherein the first amount of the onium compound is in the range of from about 5 volume % to about 75 volume %; the second amount of the amine salt in the range of from about 10 volume % to about 95 volume %, and the third amount of solvent is the range of from 0 volume % to about 85 volume %, all based on total volume of the composition.
In yet another aspect, the present invention is a composition for inhibiting formation of hydrocarbon hydrates from a mixture comprising water and a hydrocarbon, the composition comprising a first amount of an onium compound and a second amount of an amine salt, wherein the amine salt comprises a cation moiety and an anion moiety, the cation moiety is derived from an amine selected from group consisting of amines having the general formula:
(a) R
a
R
b
R
c
N, and
and mixtures thereof, wherein R
a
, R
b
, R
c
, and R
d
are independently selected from the group consisting of H, C
1
-C
3
alkyls and OH substituted C
1
-C
3
alkyls; R
e
is selected from the group consisting of —(CH
2
)
m
— and —(CH
2
)
n
—Z—(CH
2
)
p
—, wherein Z is selected from O, S and CHR
f
and m is selected from 3 to 7; n, from 1 to 3; and p, from 1 to 4; R
f
is selected from H, C
1
-C
3
alkyls and OH substituted C
1
-C
3
alkyls.
In still another aspect, the present invention is a hydrocarbon composition inhibited against hydrocarbon hydrate formation in the presence of water, wherein a mixture comprising the hydrocarbon and water is contacted with a composition of the previous paragraph.
DETAILED DESCRIPTIONS OF THE INVENTION
This invention relates a method and a composition used therein for inhibiting, retarding, mitigating, reducing, controlling and/or delaying formation of hydrocarbon hydrates or agglomerates of hydrates. The method may be applied to prevent or reduce or mitigate plugging of conduits, pipes, transfer lines, valves, and other places or equipment where hydrocarbon hydrate solids may form under the conditions.
The term “inhibiting” is used herein in a broad and general sense to mean any improvement in preventing, controlling, delaying, reducing or mitigating the formation, growth and/or agglomeration of hydrocarbon hydrates, particularly light hydrocarbon gas hydrates in any manner, including, but not limited to kinetically, thermodynamically, by dissolution, by breaking up, other mechanisms, or any combinations thereof.
The term “formation” or “forming” relating to hydrates is used herein in a broad and general manner to include, but are not limited to, any formation of hydrate solids from water and hydrocarbon(s) or hydrocarbon gas(es), growth of hydrocarbon hydrate solids, agglomeration of hydrocarbon hydrates, accumulation of hydrocarbon hydrates on surfaces, any deterioration of hydrate solids plugging or other problems in a system and combinations thereof.
The present method is useful for inhibiting hydrate formation for many hydrocarbons and hydrocarbon mixtures. The method is particularly useful for lighter or low-boiling, C
1
-C
5
, hydrocarbon gases or gas mixtures at ambient conditions. Examples of such gases include methane, ethane, ethylene, acetylene, propane, propylene, methylacetylene, n-butane, isobutane, 1-butene, trans-2-butene, cis-2-butene, isobutene, butene mixtures, isopentane, pentenes and mixtures thereof. Other examples include various natural gas mixtures that are present in many gas and/or oil formations and natural gas liquids (NGL). The hydrates of all of these low-boiling hydrocarbons are also referred to as gas hydrates. The hydrocarbons may also comprise other compounds including, but n
Przybylinski John L.
Rivers Gordon T.
Baker Hughes Incorporation
Griffin Walter D.
Madan Mossman & Sriram P.C.
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