Patent Grant
12139662
The present invention relates to methods and compositions for inhibiting the corrosion of metal surfaces that are in contact with fluids, and more particularly relates to methods and compositions for inhibiting the corrosion of metal surfaces that are in contact with oil and gas production fluids in equilibrium with such acid gases as CO2 and H2S where the composition includes a synergistic blend of two components. The invention in principle should be applicable to inhibit the corrosion of metal surfaces in contact with a brine or composite fluid containing brine that is in equilibrium with acid gases such as carbon dioxide.
The exploitation of petroleum reserves includes the recovery, transport, and processing operations of the hydrocarbon fluid (oil and raw natural gas). During oil and gas production, the metal surfaces of tubing and in some instances, casing can come in contact with acid gases such as carbon dioxide (CO2) and hydrogen sulfide (H2S). These acid gases are in equilibrium with oil, natural gas and brine. These fluids cause corrosion of well tubing and casing especially if the material is made of low alloy carbon steel. Corrosion can lead to severe damage, affecting the life span of the tubing, and that can have an impact in operational safety and the environment.
Thus, it is desirable to develop new compositions and methods for inhibiting the corrosion of metal surfaces exposed to oil and gas production fluids containing acid gases. It is also desirable if the compositions and methods are relatively environmentally friendly.
There is provided, in one form, a method for inhibiting corrosion of a metal surface in contact with an fluid containing a corrosive component selected from the group of acid gases consisting of carbon dioxide and hydrogen sulfide, where the method involves contacting the metal surface with the fluid comprising an effective amount to inhibit corrosion of a corrosion-inhibiting blend of two components, where the blend includes, but is not necessarily limited to, the following blends: glycolipids and quaternized amines, glycolipids and phosphate-containing compounds, quaternized amines and imidazoline-like compounds, quaternized amines and phosphate-containing compounds, and combinations of these blends. The method further includes that each of the two components of the blends are present in an amount effective to synergistically inhibit the corrosion of the metal surface with the blend having an improved performance greater than the sum of the inhibition the components achieved singly. In another non-limiting embodiment, the four types of blends noted above are blends of binary components as listed; i.e., they are “binary blends”. Further the fluid is a mixture of brine with oil and/or natural gas in contact with a metal surface that is carbon steel and the oil or natural gas production fluid is equilibrium with the acid gases.
There is additionally provided, in another non-restrictive version, an oil or gas production fluid that contains a hydrocarbon selected from the group consisting of oil, natural gas, and combinations thereof, brine, at least one acid gas in equilibrium with the hydrocarbon and the brine where the acid gas is selected from the group consisting of carbon dioxide and hydrogen sulfide, and a synergistic corrosion-inhibiting binary blend selected from the group consisting of glycolipids and quaternized amines, glycolipids and phosphate-containing compounds, quaternized amines and imidazoline-like compounds, and/or quaternized amines and phosphate-containing compounds.
There is further provided, in a different non-restrictive form, synergistic corrosion-inhibiting blends that include, but are not necessarily limited to, the following binary blends: glycolipids and quaternized amines, glycolipids and phosphate-containing compounds, quaternized amines and imidazoline-like compounds, quaternized amines and phosphate-containing compounds, and combinations of these blends.
Highly synergistic, environmentally friendly corrosion inhibitor binary blends have been discovered. By “environmentally friendly” is meant that the blends are expected to be readily biodegradable in sea water. These blends are important because they potentially provide a new generation of “green” corrosion inhibitor products for sensitive environmental regions such as Norway, the North Sea, Asia Pacific, Australia, Brazil, Ecuador, and West Africa.
In particular, the higher the synergy for a particular blend of corrosion inhibitors, the less amount or concentration of the blend is necessary for a particular application while still maintaining a high corrosion inhibition performance.
To discover promising corrosion inhibitor blends, synergy factors, Sθ, were calculated using Equation 1 below which is taken from J. ARAMAKI et al., “Inhibition Mechanism of Medium-Sized Polymethyleneimine,” Journal of Electrochemical Society: Electrochemical Science, May 1969, Vol. 116, No. 5, pp. 568-574:
where:
θ1+2=(θ1+θ2)−(θ1θ2) (2)
and θ1 and θ2 are the surface coverage for corrosion inhibitors 1 and 2 at their respective concentrations in separate tests under identical conditions. θ′1+2 is the surface coverage of the inhibitor blend.
Surface coverage was assumed to be equal to the inhibitor efficiency. θ1+2 in equation 1 represents the surface coverage of the blend after taking the interaction of components 1 and 2 (θ1*θ2) from the addition of the surface coverages of the individual components (θ1+θ2). In general, Sθ<1 implies an antagonistic behavior, whereas Sθ>1 implies synergistic effect. The larger the synergy factor is above 1 the stronger the synergy is between the components. Determining the synergy factor effectively allowed ranking the strength of the synergistic interactions across the tested binary blends. Details about the application of the determination of the synergy factors are given in the Examples.
Synergy is critical for enhanced corrosion inhibitor performance in the field. Field dosages often vary considerably from laboratory testing dosages because of the impact of inhibitor availability in field systems. Since many corrosion inhibitors are surfactants, they can be parasitically lost to a number of factors and processes. These factors include but are not limited to the presence of sand, the presence of emulsions, the presence of entrained scales, changes in brine chemistry that impact solubility, loss of pumping capabilities, plugged corrosion inhibitor injection lines, interference from other oil and gas production chemicals, etc. When corrosion inhibitor residual concentrations drop to low values, synergies such as those discussed herein are key to maintaining system integrity. The low concentration synergies explained herein will allow the system to maintain higher surface coverage even when the inhibitor levels drop to residual concentrations close to 5 ppm.
More specifically with respect to the components of the synergistic blends described herein, when the blend includes at least one glycolipid, suitable glycolipids include, but are not necessarily limited to, sophorolipids, rhamnolipids, and combinations thereof. In one non-limiting embodiment, suitable sophorolipids are those described in U.S. Pat. No. 9,683,164 B2 to Baker Hughes incorporated herein by reference in its entirety. In a more specific non-restrictive embodiment, a suitable sophorolipid is that shown in the acid form of structure (I) below in equilibrium with the lactonic form of structure (II).
In a different non-limiting embodiment, suitable rhamnolipids are those described in U.S. Pat. No. 9,884,986 B2 to Baker Hughes incorporated herein by reference in its entirety. In a more specific non-restrictive embodiment, a suitable sophorolipid is that shown in the acid form of structure (III) below.
In another non-limiting embodiment, when the blend includes at least one quaternized amine, the quaternized amine has ester and alkoxy functional groups. Further, suitable quaternized amines include, but are not necessarily limited to, di(dimethyl(alkyl)ammonium chloride) ethanoyloxy-oxo, methyl quaternized N-methyl dialkanolamine and fatty acid diacid copolymers, esterified diquaternary amines, and combinations thereof. Suitable polyalkylene glycol diester diquats have the structure (IV):
and suitable polyalkylene glycol monoester quat have the structure (V):
where X is Cl or Br; each R is independently a C16-C18 alkyl group; and n is within the range of 8 to 50.
In a different, non-restrictive version, when the blend includes at least one phosphate-containing compound, suitable phosphate-containing compounds include, but are not necessarily limited to, phosphate esters, ethoxylated phosphate esters, sodium hydroxypropylphosphate laurylglucoside crosspolymers, sodium laurylglucoside hydroxy propyl phosphates, sodium cocoglucosides hydroxypropyl phosphates, and combinations thereof. Suitable phosphate esters include, but are not necessarily limited to those of formula (VI), where m and n each independently range from 2 to 20 and R1 is C6 to C18 and R2 C6 to C18:
In an alternate, non-limiting embodiment when the blend includes at least one imidazoline-like compound, suitable imidazoline-like compounds include, but are not necessarily limited to, ethoxylated quaternized imidazolines, ethoxylated imidazolines, naphthenic acid imidazolines, imidazolines that are reaction products of tall oil fatty acid and diethylenetriamine, and combinations thereof. Suitable ethoxylated quaternized imidazolines include, but are not necessarily limited to, those of formula (VII) where R1 is a fatty acid residue, R2 is an alkyl, aromatic, or combined alkyl-aromatic group, and n ranges from 3 to 25:
Other suitable imidazolines include, but are not necessarily limited to, those of formula (VIII) and (IX):
In formula (VIII), R describes the hydrophobic tail portion of the molecule and J describes the pendant group of the molecule, R is the fatty or naphthenic acid residue. The Pendant group, J, may be selected from a group consisting of (CH2—CH2)—X, (CH2—CH2—O)nH, CH2—CH2—(NH—CH2—CH2)y—Z, where X can be NH2, OH or NH—CO—R1, n can be 3 to 25 and where Z can be NH2 or NH—CO—R2 and y is greater than 2. In formula (IX) n can be 1 to 5.
With respect to the proportions of the two components of the binary blends discovered to have synergistic effects when used in the fluid herein, this will depend on which component types are used together. Abbreviations for the classes of components are given below in Table I. Table II provides a broad range of proportions for each component and a narrow range of proportions for each component, for the binary blends given. It will be appreciated that the endpoints of the ranges in each row may be independently combined to give a suitable alternative range. For example, in the blend of SB/EQ-A, the SB component may be present from 2 to 500 ppm, and the EQ-A component may be used in a proportion from 0.1 to 20 ppm.
In another non-restrictive version, the blend has a weight ratio of components ranging from about 20:1 independently to about 1:20; alternatively from about 19:1 independently to about 1:19; in a different non-limiting embodiment from about 10:1 independently to about 1:10; in another non-restrictive version from about 9:1 independently to about 1:9; alternatively from about 5:1 independently to about 1:5; in another non-limiting embodiment from about 3:1 independently to about 1:3; and finally at a ratio of about 1:1, which about 1:1 ratio may be a suitable endpoint for any of the previous proportion ranges. Where the word “independently” is used with respect to a range, it will be understood that any of the endpoints mentioned may be used together with any other of the endpoints to give a suitable alternative range.
The effective amount of the corrosion-inhibiting blend in the aqueous fluid ranges from about 1 ppm independently to about 500 ppm; alternatively, from about 2 ppm independently to about 200 ppm. The corrosive fluid may be any oilfield fluid in contact with a metal surface. Suitable specific fluids include, but are not necessarily limited to, oil and natural gas production fluids that are in contact with metal tubulars in general, and in a non-restrictive specific case, carbon steel tubing and casing. To further define the fluids in a non-limiting embodiment, the fluid is oil and/or natural gas containing brine where acid gases such as CO2 and H2S are in equilibrium therewith.
In one non-limiting embodiment of the method and compositions herein, the blend has a corrosion efficiency of at least 85% (or 0.85 fractional surface coverage); alternatively, at least 90% (or 0.90 fractionally surface coverage); in a different non-restrictive version at least 95% (or 0.95 fractionally surface coverage); and in an alternate non-limiting embodiment at least 97% (or 0.97 fractionally surface coverage), where inhibition efficiency is defined as blank corrosion rate minus inhibited corrosion rate with the result divided by the blank corrosion rate. This fraction is multiplied by 100 to get the percent inhibition or corrosion efficiency. Corrosion efficiency in both fractional and percent inhibition forms will be used interchangeably to describe corrosion inhibitor blend performance.
The invention will now be described with respect to particular embodiments which are not intended to limit the invention in any way, but which are simply to further highlight or illustrate the invention. All percentages (%) given below are weight percentages unless otherwise noted and all ratios are weight ratios unless otherwise noted.
Table III shows the synergy factors calculated for blends of SB with EQ-A at ratios of 3:1 and 9:1, respectively.
An example is provided below on the use of the J. Aramaki et. al. equation for calculating the synergy factors. In this case one of the two components did not exhibit surface coverage when tested as a single chemistry. From Table III the calculation of the synergy factor for the data point at 0.25 weight fraction of EQ-A is as follows:
where:
θ1=0.505 and is the surface coverage for SB at 3.75 ppm
θ2=0 and is the surface coverage of EQ-A at 1.25 ppm
θ1*θ2=(0.505*0)=0
θ′1+2=0.949 is the surface coverage of the blend at 5 ppm.
Table IV shows the synergy factors calculated for SB and EQ-B with ratios of 9:1, 3:1, 1:1, and 1:3, respectively.
Another example is provided below on the use of the Aramaki et. al. equation for calculating the synergy factors. In this case both components exhibited surface coverage when tested individually. From Table IV, calculation of the synergy factor for the data point at 0.25 weight fraction of EQ-B is as follows:
where:
θ1=0.505 and is the surface coverage for SB at 3.75 ppm
θ2=0.901 and is the surface coverage of EQ-B at 1.25 ppm
θ1*θ2=(0.505*0.901)=0.455
θ′1+2=0.96
Table V shows the synergy factors calculated for the SB and PEQ-A with ratios of 9:1 and 3:1, respectively.
Table VI shows the synergy factors calculated for the SB and PEQ-B mixtures ratios of 9:1 and 3:1, respectively.
Table VII shows the synergy factors calculated for the SB and EQI blends with ratios of 9:1, 3:1, and 1:1.
Note: There are no data for RB together with EQI, but one of ordinary skill in the art would expect synergies based on the SB results above.
Table VIII shows the synergy factors calculated for the RB and EQ-A blend with the ratio of 19:1 and 9:1.
Another example is provided below on the use of the Aramaki et. al. equation for calculating the synergy factors. In this case neither component exhibited surface coverage when tested individually. From Table VIII the calculation of the synergy factor for the 0.1 weight fraction of EQ-A will be as follows:
where:
θ1=0 and is the surface coverage for RB at 4.5 ppm
θ2=0 and is the surface coverage of EQ-A at 0.5 ppm
θ1*θ2=(0*0)=0
θ1+2=0.925 where θ′1+2 is the surface coverage of the inhibitor blend.
It will be appreciated that the other reported synergy factors were similarly calculated even though the calculations will not be explicitly shown herein for each case.
Table IX shows the synergy factors calculated for the RB and EQ-B blend with the ratio of 9:1.
Table X shows the synergy factor calculated for the RB and PEQ-A blend with the ratio of 3:1.
Table XI shows the synergy factor calculated for the RB and PEQ-B blends with the ratios of 19:1 and 9:1.
Table XII shows the synergy factors calculated for the PE-A and EQ-B blends with the ratios of 9:1 and 5:1.
Table XIII shows the synergy factor calculated for the PE-B and EQ-B blends with ratio 9:1 and 3:1.
Table XIV shows the synergy factor calculated for the LGC and EQ-B blend with ratio 20:1.
Note: No data are available for EQ-B with CGHP but synergy is expected because of the similarities between the structures of LGHP and CGHP. This same logic applies for mixtures of EQ-A with LGHP and CGHP.
Table XV shows the synergy factor calculated for the LGHP and EQ-B blend with ratio 100:1.
Table XVI shows the synergy factors calculated for the SB and LGC blends with ratios of 3:1 and 1:1.
Table XVII shows the synergy factors calculated for the SB and LGHP blends with ratios of 20:1 and 10:1.
Table XVIII shows the synergy factors calculated for the SB and PE-A blends with ratios of 9:1, 3:1, 1:1, 1:3, and 1:9.
Table XIX shows the synergy factors calculated for the SB and PE-B blends with ratios of 9:1, 3:1, 1:1, 1:3, and 1:9.
Table XX shows the synergy factor calculated for the EQI and EQ-B blend with a ratio of 9:1.
Table XXI shows the synergy factors calculated for the EI and EQ-B blends with ratios of 19:1 and 9:1.
Table XXI shows the synergy factors calculated for the EI and EQ-A blends with ratios of 19:1 and 9:1.
Note: No data are available for these other Imidazolines. However, these imidazolines are included herein based on the structural similarities between these imidazolines and EQI which showed a strong synergy with EQ-B.
The Examples thus demonstrate how blends of two certain specific components can give unexpectedly synergistic corrosion inhibition improvement of a metal surface in contact with an aqueous fluid.
In the foregoing specification, the invention has been described with reference to specific embodiments thereof, and has been described as effective in providing methods and compositions for directly inhibiting corrosion of a metal surface in contact with an aqueous fluid, in particular one containing corrosive components including, but not necessarily limited to, acid gases such as H2S and CO2. However, it will be evident that various modifications and changes can be made thereto without departing from the broader scope of the invention. Accordingly, the specification is to be regarded in an illustrative rather than a restrictive sense. For example, specific glycolipids, quaternized amines, phosphate-containing compounds, imidazoline-like compounds, proportions of the compounds in the blends, weight ratios, and other components and procedures falling within the claimed parameters, but not specifically identified or tried in a particular method or composition, are expected to be within the scope of this invention.
The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. For instance, there may be provided a method for inhibiting corrosion of a metal surface in contact with an aqueous fluid containing a corrosive component, where the method comprises, consists essentially of, or consists of contacting the metal surface with the aqueous fluid comprising an effective amount to inhibit corrosion of a corrosion-inhibiting blend of two components, where the blend is selected from the group consisting of:
There may also be provided synergistic corrosion-inhibiting binary blends comprising, consisting essentially of, or consisting of:
The words “comprising” and “comprises” as used throughout, are to be interpreted to mean “including but not limited to” and “includes but not limited to”, respectively.
As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As used herein, the term “about” in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
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| Entry |
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