CORROSION INHIBITING FORMULATION FOR DRILLING FLUID BRINES BACKGROUND OF THE INVENTION

[0001] The present invention relates to corrosion inhibition and, in particular, to mixtures of corrosion inhibitors for use in drilling fluids which fluids can contain simply water, or a brine containing water and a salt, such as, for example, chloride or formate salts.

[0002] Calcium chloride is a widely used industrial chemical. Significant volumes are used as a curing accelerator in concrete, as an additive in drilling muds to control density and clay flocculation, as a drainage aid in paper mills, as a dessicant in refrigeration plants, and as a heat transfer fluid in closed recirculating cooling systems operating at temperatures below zero °C.

[0003] Calcium chloride brines in applications such as for concrete accelerators or as additives to drilling muds create serious corrosion problems. The calcium chlo- ride in drilling muds for example causes an accelerated corrosion of well tubing and equipment used in oil drilling applications.

[0004] One effective group of corrosion inhibitor is that comprising hydroxy phosphonic acids. However, improvement is needed over that which can be provided by hydroxy phosphonic acids alone.

SUMMARY OF THE INVENTION

[0005] The disclosed technology, therefore, solves the problem of improved anti- corrosion performance by providing a synergistic blend of corrosion inhibitors.

[0006] The disclosed technology provides a corrosion inhibitor additive formulation. The formulation includes a corrosion inhibiting package containing a distilla- tion residue from the production of morpholine, and a phosphono carboxylic acid

[0007] The distillation residue from the production of morpholine can be present in the corrosion inhibiting package from about 50 to about 90% by weight. The phosphono carboxylic acid can be present in the corrosion inhibiting package from about 10 to about 50% by weight.

[0008] In an embodiment, the distillation residue from the production of morpholine can include at least one morpholine derivative. The at least one morpholine derivative can itself include at least one of [(aminoethoxy)ethyl]morpholine, [(hy- droxyethoxy)ethyl]morpholine, 3-morpholinone and 4,4'-(oxydi-2, l - ethanediyl)bis[morpholine] or mixtures thereof.

[0009] In some embodiments, the distillation residue can contain a solution of at least one morpholine derivative, and at least one glycol, such as, for example, dieth- ylene or triethylene glycol. In particular embodiments, the distillation residue can include from about 70 to about 90% by weight of a solution containing from about 50 to about 70% by weight of at least one morpholine derivative, and from about 10 to about 30 wt% of at least one glycol. In the same or different embodiments, the distillation residue can include from about 10 to about 30% by weight of a solution containing from about 10 to about 30% by weight of at least one morpholine derivative, from about 0.1 to about 2 wt% of at least one glycol, and from about 70 to about 90wt% water.

[0010] In another embodiment, the phosphono carboxylic acid can include 2-hy- droxy phosphonoacetic acid ("HPAA").

[0011] In embodiments, the corrosion inhibitor additive formulation can further contain other additives employed in drilling muds.

[0012] In an embodiment, the corrosion inhibiting package can be present in the corrosion inhibitor additive formulation at a concentration of from about 60 to about 80%) by weight of the corrosion inhibitor additive formulation.

[0013] In some embodiments, the corrosion inhibitor additive formulation can further contain from about 5 to about 15%> by weight methanol. In further embodiments, the corrosion inhibitor additive formulation can also contain from about 10 to about 30%) by weight ethylene glycol.

[0014] Another aspect of the technology is directed to a drilling fluid. The drilling fluid can contain 1) an aqueous solution, and 2) a corrosion inhibitor additive formulation, as described herein.

[0015] In an embodiment, the aqueous solution can contain freshwater, meaning water taken from the closest water source available. In another embodiment, the aqueous solution can contain a brine comprising a salt or salt mixture dissolved in water. In an embodiment, the brine in the drilling fluid brine can include at least one of calcium chloride, potassium formate, sodium formate or mixtures thereof. [0016] A further aspect of the technology is directed to a method of drilling a zone of a well. The method can include the steps of: (A) introducing a drilling fluid as described herein into the zone and (B) drilling in the zone.

DETAILED DESCRIPTION OF THE INVENTION

[0017] Various preferred features and embodiments will be described below by way of non-limiting illustration.

[0018] The technology relates to a corrosion inhibitor additive formulation. The formulation includes a corrosion inhibiting package comprising, consisting essentially of, or consisting of at least one distillation residue from the production of mor- pholine, along with a phosphono-carboxylic acid and mixtures thereof.

[0019] Morpholine can be produced by the reaction of diethylene glycol and ammonia. To obtain the morpholine, the reaction product of the diethylene glycol/am- monia reaction is distilled. In fact, the reaction products can go through numerous distillations. Each distillation produces residues. These residues from the morpho- line production process likewise can be further processed and distilled to produce further residues. All of the residues prepared in the various distillation steps of both the diethylene glycol/ammonia reaction products and residues can contain morpholine derivatives, as well as other compounds, including residual glycols, such as, for example, diethylene or tri ethylene glycol.

[0020] The morpholine derivatives within the distillation residues are generally obtained as a clear, dark-amber liquid composed primarily of a mixture of aliphatic and heterocyclic mono- and di -amines having a morpholinyl ring being the dominant heterocyclic group present, with oxyethyiene linkages appearing frequently in the various compounds present. The morpholine derivatives can also include morpho- line, per se. In an embodiment, morpholine derivatives suitable for use in the corrosion inhibiting package can be obtained from the distillation residue left from the various distillations of the diethylene glycol/ammonia reaction products, as well the various distillations of the resultant residues.

[0021] In general the morpholine derivatives, obtained as distillation residues, can include, for example, at least one of [(aminoethoxy)ethyl]morpholine, [(hydroxyeth- oxy)ethyl]morpholine, 3-morpholinone and 4,4'-(oxydi-2, l -ethanediyl)bis[morpho- line], i.e. compounds of the formulas A-D:

and mixtures thereof.

[0022] In some embodiments, the corrosion inhibitor additive formulation can contain from about 50 to about 90% by weight of the distillation residues from the production of morpholine, or from about 52 to about 85%> by weight, or from about 55 to about 80%> by weight of the distillation residues.

[0023] In some embodiments, the distillation residue can contain from about 70 to about 90%), or from about 71 to about 89%> by weight, or from about 72 to about 88%o by weight, or about 73 to about 87 wt%>, or about 74 to about 84 wt%>, or even from about 75 to about 85 wt%>, of a solution containing from about 50 to about 70% by weight of at least one morpholine derivative, or from about 52 to about 68 wt%>, or from about 55 to about 65 wt%> of at least one morpholine derivative. The solution can also contain about 10 to about 30 wt%> of some form of glycol, such as di ethylene or triethylene glycol, for example. In some embodiments, the glycol can be present at from about 12 to about 28wt%> glycol, or even from about 15 to about 25wt%> glycol.

[0024] In some embodiments, the corrosion inhibitor additive formulation can contain from about 10 to about 30wt%>, or from about 1 1 to about 25wt%>, or even from about 12 to about 20% by weight of a solution containing from about 10 to about 30%) by weight, 12 to about 28wt%>, or from about 15 to about 25wt%> morpholine derivatives. Such a solution can also contain about 0.1 to about 2 wt%> some form of glycol, such as di ethylene or triethylene glycol, for example. In some embodiments, the glycol can be present at from about 0.2 to about 1.5wt%>, or from about 0.3 to about lwt%, or even from about 0.4 to about 0.8 wt%. Such a solution can also be diluted in about 70 to about 90 wt% water, or from about 72 to about 88wt% water, or from about 75 to about 85wt% water.

[0025] The corrosion inhibitor additive formulation also includes a phosphono- carboxylic acid. The phosphonocarboxylic acid may be of the formula:

or a water-soluble salt thereof, in which R ₂ is C0 ₂ H, P(=0)(OH) ₂ , CH ₂ P(=0)(OH) ₂ , CH ₂ CH ₂ P(=0)(OH)2 or NR5R6 in which R5 and R ₆ are the same or different and each is, hydrogen-methyl, or C(R ₇ ) ₂ C0 ₂ H in which R ₇ is hydrogen or methyl; R ₃ is hydrogen, Ci-C ₆ alkyl, CH ₂ C0 ₂ H or CH ₂ CH ₂ C0 ₂ H; and R ₄ is hydrogen, hydroxyl, C0 ₂ H, P(=0)(OH) ₂ , CH2CO2H or CH2CH2CO2H.

[0026] In one example embodiment, R ₂ is C0 ₂ H or P(=0)(OH) ₂ ; R ₃ is hydrogen or methyl; and R ₄ is hydroxyl. Other examples of compounds of the phosphonocar- boxylic acid can include, for example: phosphonoacetic acid; 2-phosphonopropionic acid; 2-phosphonoheptanoic acid; 2-hydroxy phosphonoacetic acid ("HPAA"); 2-hy- droxy-2-methyl phosphonoacetic acid; 2-hydroxy-2-butyl phosphonoacetic acid; 3- phosphono-3 -hydroxy butyric acid; 2-phosphonoethane-l,2-dicarboxylic acid; 2- phosphono-butane-l,2,4-tricarboxylic acid; methane diphosphonic acid; 1,2- ethanediphosphonic acid; 1,3-propanediphosphonic acid; hydroxymethyl diphosphonic acid; hydroxyethyl diphosphonic acid (HEDP); 2-amino-phosphonoacetic acid; 2-amino-2-methyl phosphonoacetic acid; nitrilo-tris-methylene phosphonic acid; methylamino-bis-methylene phosphonic acid; phosphonomethyl glycine; bis- phosphonomethyl glycine; phosphonomethylimino diacetic acid; and 1 -aminoethyl- 1, 1 -diphosphonic acid.

[0027] Water-soluble salts of compounds of the phosphonocarboxylic acid can include, for example, alkali metal salts, such as sodium or potassium salts; alkaline earth metal salts such as calcium or magnesium salts; ammonium salts; Ci-C ₈ alkyl- amine salts such as methylamine, ethylamine, n-propylamine, trimethylamine, tri- ethylamine, n-butylamine, n-hexylamine or n-octylamine salts; alkanolamine salts such as ethanolamine, di- or tri-ethanolamine salts; or heterocyclic amine salts such as morpholine salts.

[0028] In some embodiments, the corrosion inhibitor additive formulation can contain from about 10 to about 50wt% of the phosphonocarboxylic acid. In other embodiments, the corrosion inhibitor additive formulation can contain from about 1 1 to about 40wt% of the phosphonocarboxylic acid, or from about 12 to about 30wt%, or about 13 to about 20wt% of the phosphonocarboxylic acid.

[0029] The corrosion inhibiting package, i.e., the morpholine derivative or mixture thereof and the phosphonocarboxylic acid or mixture thereof, can be present in the corrosion inhibitor additive formulation from about 60 to about 80% by weight. In an embodiment, the corrosion inhibiting package can be present in the corrosion inhibitor additive formulation from about 65 to about 75% by weight.

[0030] The corrosion inhibitor additive formulation can additionally contain other additives generally included in drilling fluid formulations.

[0031] In an embodiment, the corrosion inhibitor additive formulation can further include from about 5 to about 15%, or from about 8 to about 12% by weight methanol.

[0032] Separately, or in addition to the methanol, the corrosion inhibitor additive formulation can further include from about 10 to about 30%, or from about 15 to about 25% by weight ethylene glycol.

[0033] The technology described herein also relates to a drilling fluid comprising, consisting of, or consisting essentially of 1) an aqueous solution, and 2) a corrosion inhibitor additive formulation as described hereinabove. The aqueous solution may comprise freshwater, simply meaning water taken from the closest water source, such as a pond, lake, municipal water system, etc., containing the ordinary minerals and sediments generally included in such sources. The aqueous solution may also comprise a brine comprising a salt or salt mixture dissolved in the aqueous solution.

[0034] The drilling fluid may be a totally aqueous or a partly aqueous system. [0035] The salt used in the brine of the drilling fluid can be any salt generally used in drilling fluids, such as, for example, chloride and formate salts. In an embodiment, the salt can include at least one of calcium chloride, potassium formate, sodium formate or mixtures thereof.

[0036] The amount of the corrosion inhibiting additive formulation added to the drilling fluid can be from about 0.1 to about 50,000 ppm (i.e., about 0.00001 to 5% by weight), or even from about 1 to about 500 ppm (i.e., about 0.0001 to about 0.05% by weight), based on the weight of the drilling fluid.

[0037] Another aspect of the present technology relates to a method of drilling a zone of a well. The method can comprise, consist of, or consist essentially of the steps of: (A) introducing a drilling fluid into the zone; and (B) drilling in the zone; the drilling fluid being that as described above, i.e., having (i) an aqueous solution being at least one of freshwater or a brine comprising a salt or salt mixture dissolved in an aqueous solution, and (ii) a corrosion inhibitor additive formulation as described herein.

[0038] The amount of each chemical component described is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, that is, on an active chemical basis, unless otherwise indicated. However, unless otherwise indicated, each chemical or composition referred to herein should be inter- preted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade.

[0039] It is known that some of the materials described above may interact in the final formulation, so that the components of the final formulation may be different from those that are initially added. For instance, metal ions (of, e.g., a detergent) can migrate to other acidic or anionic sites of other molecules. The products formed thereby, including the products formed upon employing the composition of the present invention in its intended use, may not be susceptible of easy description. Nevertheless, all such modifications and reaction products are included within the scope of the pre- sent invention; the present invention encompasses the composition prepared by admixing the components described above. [0040] As used herein, the term "about" means that a value of a given quantity is within ±20% of the stated value. In other embodiments, the value is within ±15% of the stated value. In other embodiments, the value is within ±10% of the stated value. In other embodiments, the value is within ±5% of the stated value. In other embodiments, the value is within ±2.5% of the stated value. In other embodiments, the value is within ±1% of the stated value.

[0041] The invention herein is useful for inhibiting corrosion of equipment used in down-hole drilling operations, which may be better understood with reference to the following examples.

EXAMPLES

[0042] Several corrosion inhibiting formulations were tested for corrosion inhibition efficiency according to the Linear Polarization Resistance (LPR) test method according to ASTM Gl 70-06, using a Rotating Cylinder Electrode (RCE) in a brine pre- pared by mixing 32% by weight CaCb in deionized water.

[0043] The samples tested were:

Sample 1 - brine alone; no inhibitor

Sample 2 - distillation residues from the production of morpholine via the reaction of ammonia and di ethylene glycol, containing from about 58 to about 62wt% morpholine derivatives and about 21 to about 23wt% glycol

Sample 3 - distillation residues from the production of morpholine via the reaction of ammonia and di ethylene glycol, containing from about 18 to about 22wt% morpholine derivatives and about 0.4 to about 0.8wt% glycol in about 78 to about 82wt% water

Sample 4 - HPAA

Sample 5 -ammonium bisulfite.

[0044] Ammonium bisulfite was added to several samples to scavenge dissolved oxygen in the brines due to the high shear rate of the test at atmospheric pressure. Ammonium bisulfite accelerates corrosion and therefore would not contribute to the corrosion inhibiting results, but would most likely have a detrimental effect to corrosion inhibition.

[0045] The inhibitors were added to the experimental brine in various formulations. Formulation 1 (Fl) - Sample 2 at 4500 ppm in the brine, providing a total of about 2610 to about 2790ppm morpholine derivatives to the brine;

Formulation 2 (F2) - Sample 3 at 4500 ppm in the brine, providing a total of about 810 to about 990ppm morpholine derivatives to the brine;

Formulation 3 (F3) - Sample 2 at 2250 ppm in the brine + Sample 3 at 2250 ppm in the brine, a total of about 1710 to about 1890ppm morpholine derivatives to the brine;

Formulation 4 (F4) - Sample 4 at 2250 ppm;

Formulation 5 (F5) - Sample 2 at 3500 ppm + Sample 4 at 250ppm + Sample 5 at 30ppm, providing a total of about 2030 to about 2170ppm morpholine derivatives to the brine;

Formulation 6 (F6) - Sample 2 at 2450 ppm + Sample 3 at 500ppm + Sample 4 at 250ppm + Sample 5 at 30ppm, providing a total of about 151 1 to about 1629ppm morpholine derivatives to the brine;

[0046] The formulations along with the test results are shown in Table I below.

Table 1

Comparison

Test duration Sample 1

Fl F2 F3 F4 F5 F6 (hrs.) - Control

0.0 116.8 7.1 8.0 6.1 8.5 8.0 1.1

0.2 34.6 7.2 7.2 6.5 16.6 8.9 1.1

0.3 34.3 7.6 10.0 6.6 15.3 6.0 1.1

0.5 83.2 7.4 8.7 6.9 8.6 5.2 1.1

0.7 45.7 7.5 8.0 7.2 19.1 2.9 1.1

0.8 42.5 8.3 6.9 7.2 9.2 5.8 1.0

1.0 39.4 8.3 8.2 7.2 18.3 3.7 1.0

1.2 47.3 8.1 6.7 7.0 6.6 6.3 1.1

1.3 34.8 7.9 7.0 7.3 18.0 3.1 1.1

1.5 40.7 8.2 6.6 7.3 14.7 2.7 1.0

1.7 30.9 8.6 9.2 7.5 14.2 3.9 1.1 1.9 33.7 8.4 9.6 7.6 6.8 3.2 1.1

2.0 36.5 8.6 10.2 7.6 17.0 2.5 1.1

2.2 68.6 9.0 8.6 7.7 12.7 3.3 1.1

2.3 93.1 8.6 7.3 7.4 10.2 2.7 1.0

2.5 53.8 8.9 8.1 7.6 8.2 1.2 1.0

2.7 96.7 8.9 6.7 7.5 12.4 3.6 1.1

2.8 74.7 9.1 8.7 7.5 10.0 2.8 1.1

Avg Corrosion

56.0 8.2 8.1 7.2 12.6 4.2 1.1 Rate (mpy)

Efficiency (%) - 85.3% 85.5% 87.1% 77.5% 92.5% 98.1%

[0047] The results show that the concentration of morpholine derivatives in a formulation, on its own, has a negligible effect on corrosion inhibition. The results also show that the use of HPAA on its own does not perform as well as the morpholine derivatives. However, it is shown that the use of the morpholine derivatives along with HPAA provides a synergistic effect that increases the level of corrosion inhibition. The results also show that the use of varying distillation residues provides an even further synergy.

[0048] Each of the documents referred to above is incorporated herein by reference, including any prior applications, whether or not specifically listed above, from which priority is claimed. The mention of any document is not an admission that such document qualifies as prior art or constitutes the general knowledge of the skilled person in any jurisdiction. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word "about." It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention can be used together with ranges or amounts for any of the other elements.

[0049] As used herein, the transitional term "comprising," which is synonymous with "including," "containing," or "characterized by," is inclusive or open-ended and does not exclude additional, un-recited elements or method steps. However, in each recitation of "comprising" herein, it is intended that the term also encompass, as alternative embodiments, the phrases "consisting essentially of and "consisting of," where "consisting of excludes any element or step not specified and "consisting essentially of permits the inclusion of additional un-recited elements or steps that do not materi- ally affect the essential or basic and novel characteristics of the composition or method under consideration.

[0050] While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without de- parting from the scope of the subject invention. In this regard, the scope of the invention is to be limited only by the following claims.