Novel Modified Acid Compositions as Alternatives to Conventional Acids in the Oil and Gas Industry

Abstract

An aqueous modified acid composition for use in oil industry activities, said composition comprising: an amino acid, an alkanolamine and strong acid wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 15:1, preferably not more than 10:1; it can also further comprise a metal iodide or iodate. Said composition demonstrates advantages over known conventional acids and modified acids.

Claims

1. An aqueous modified acid composition comprising: a mineral acid; an amino acid; and an alkanolamine; wherein the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 15:1.

2. An aqueous modified acid composition according to claim 1, wherein the amino acid:alkanolamine proportion ranges from 1%:99% to 99%:1%.

3. An aqueous modified acid composition according to claim 1, wherein the amino acid:alkanolamine proportion ranges from 20%:80% to 80%:20%.

4. An aqueous modified acid composition according to claim 1, wherein the amino acid:alkanolamine proportion ranges from 30%:70% to 70%:30%.

5. An aqueous modified acid composition according to claim 1, wherein the amino acid:alkanolamine proportion is 50%:50%.

6. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 10:1.

7. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 7.0:1.

8. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 4:1.

9. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 3:1.

10. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio ranging from 3:1 to 12:1.

11. The aqueous modified acid composition according to claim 1, wherein the mineral acid:alkanolamine/amino acid are present in a molar ratio ranging from 5:1 to 10:1.

12. The aqueous modified acid composition according to claim 1, wherein the alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine and combinations thereof.

13. The aqueous modified acid composition according to claim 1, wherein the amino acid is selected from the group consisting of: lysine, glycine, valine, arginine, histidine, threonine, methionine and combinations thereof.

14. The aqueous modified acid composition according to claim 1, wherein the alkanolamine is monoethanolamine.

15. The aqueous modified acid composition according to claim 1, wherein the alkanolamine is diethanolamine.

16. The aqueous modified acid composition according to claim 1, wherein the mineral acid is selected from the group consisting of: HCl, nitric acid, sulfuric acid, sulfonic acid, phosphoric acid, and combinations thereof.

17. The aqueous modified acid composition according to claim 1, further comprising a metal iodide or iodate selected from the group consisting of: cuprous iodide; potassium iodide; sodium iodide; lithium iodide and combinations thereof.

18. The aqueous modified acid composition according to claim 1, further comprising an alkynyl alcohol or derivative thereof present in a concentration ranging from 0.01 to 5% w/w.

19. The aqueous modified acid composition according to claim 18, wherein the alkynyl alcohol or derivative thereof is propargyl alcohol or a derivative thereof.

20. The aqueous modified acid composition according to claim 17, wherein the metal iodide is present in a concentration ranging from 0.1 to 2% by weight of the total weight of the composition.

21. The use of an aqueous modified acid composition in an oil industry activity, said composition comprising: a mineral acid; an amino acid; and an alkanolamine; wherein the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 15:1, and wherein the use comprises an activity selected from the group consisting of: stimulate formations; assist in reducing breakdown pressures during downhole pumping operations; treat wellbore filter cake post drilling operations; assist in freeing stuck pipe; descale pipelines and/or production wells; increase injectivity of injection wells; lower the pH of a fluid; remove undesirable scale on a surface selected from the group consisting of: equipment, wells and related equipment and facilities; fracture wells; complete matrix stimulations; conduct annular and bullhead squeezes & soaks; pickle tubing, pipe and/or coiled tubing; increase effective permeability of formations; reduce or remove wellbore damage; clean perforations; and solubilize limestone, dolomite, calcite and combinations thereof.

22. Method of treating a metal surface with a composition comprising a mineral acid; an amino acid; and an alkanolamine; wherein the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 15:1,: said method comprising the steps of: providing said composition; exposing said metal surface to said composition; allowing said composition a sufficient period of time to act upon said surface; and optionally, removing the acid composition when the exposure time has been determined to be sufficient for the operation to be complete or sufficiently complete.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] The invention may be more completely understood in consideration of the following description of various embodiments of the invention in connection with the accompanying figure, in which:

[0040] FIG. 1 is a graphical representation of the spend rate of two concentrations (50% and 90%) of a composition of Lysine-HCl:MEA-HCl (80:20) according to a preferred embodiment of the present invention;

[0041] FIG. 2 is a graphical representation of the spend rate of two concentrations (50% and 90%) of a composition of Lysine-HCl:MEA-HCl (70:30) according to a preferred embodiment of the present invention;

[0042] FIG. 3 is a graphical representation of the spend rate of two concentrations (50% and 90%) of a composition of Lysine-HCl:MEA-HCl (50:50) according to a preferred embodiment of the present invention;

[0043] FIG. 4 is a graphical representation of the spend rate of two concentrations (50% and 90%) of a composition of Lysine-HCl:MEA-HCl (30:70) according to a preferred embodiment of the present invention;

[0044] FIG. 5 is a graphical representation of the spend rate of two concentrations (50% and 90%) of a composition of Lysine-HCl:MEA-HCl (20:80) according to a preferred embodiment of the present invention;

[0045] FIG. 6 is a graphical representation of the wormholing efficiency of a composition according to a preferred embodiment of the present invention compared to a HCl composition, a MEA-HCl composition and two different lysine-HCl compositions; and

[0046] FIG. 7 is a graphical representation of the wormholing efficiency of a composition according to a preferred embodiment of the present invention compared to a HCl composition and a MEA-HCl composition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS AND DRAWINGS

[0047] The description that follows, and the embodiments described therein, is provided by way of illustration of an example, or examples, of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not limitation, of those principles and of the invention.

[0048] According to an aspect of the present invention, there is provided an aqueous synthetic or modified acid composition comprising: [0049] a mineral acid; [0050] an amino acid; and [0051] an alkanolamine;
wherein the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 15:1. Preferably, the mineral acid: alkanolamine/amino acid are present in a molar ratio ranging from 3:1 to 12:1.
More preferably, the mineral acid:alkanolamine/amino acid are present in a molar ratio ranging from 5:1 to 10:1.

[0052] Preferably, the proportion of amino acid:alkanolamine ranges from 1%:99% to 99%:1%. More preferably, the proportion of amino acid:alkanolamine ranges from 20%:80% to 80%:20%. Even more preferably, the proportion of amino acid:alkanolamine ranges from 30%:70% to 70%:30%. Yet even more preferably, the proportion of amino acid: alkanolamine is 50%:50%.

[0053] Preferably, the mineral acid:alkanolamine/amino acid are present in a molar ratio of not more than 10:1. More preferably, the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 7.0:1. According to a preferred embodiment, the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 4:1. According to another preferred embodiment, the mineral acid: alkanolamine/amino acid are present in a molar ratio of not more than 3:1. According to a preferred embodiment, the molar ratio of mineral acid to amino acid/alkanolamine is calculated by determining the total number of moles of mineral acid (adding up the moles from the mineral acid/amino acid blend and the moles from the mineral acid/alkanolamine blend) and adding up the moles of amino acid in the first blend to the moles of alkanolamine from the second blend. Thus, for explanation purposes a ratio of 12:1 mineral acid:aminoacid/alkanolamine means that for every 12 moles of HCl there is a combined total of 1 mole of amino acid and alkanolamine. Moreover, the % proportion of amino acid:alkanolamine is to be understood in terms of moles of the mole total of amino acid and alkanolamine. For explanation purposes, when there is a 30%/70% blend of example 1/example 2 one is to understand that there is 0.3 mol amino acid to 0.7 mol alkanolamine.

[0054] Preferably, the alkanolamine is selected from the group consisting of: monoethanolamine; diethanolamine; triethanolamine and combinations thereof.

[0055] According to a preferred embodiment, the amino acid is selected from the group consisting of: lysine, glycine, valine, arginine, histidine, threonine, methionine, glutamic acid, asparagine, glutamine and combinations thereof.

[0056] According to a preferred embodiment, the alkanolamine is monoethanolamine. According to another preferred embodiment, the alkanolamine is diethanolamine.

[0057] According to a preferred embodiment, the mineral acid is selected from the group consisting of: HCl, nitric acid, sulfuric acid, sulfonic acid, phosphoric acid, and combinations thereof.

[0058] Preferably, the aqueous modified acid composition further comprising a metal iodide or iodate. Preferably, the metal iodide or iodate is selected from the group consisting of: cuprous iodide; potassium iodide; sodium iodide; lithium iodide and combinations thereof. More preferably, the metal iodide or iodate is potassium iodide.

[0059] According to a preferred embodiment, the aqueous modified acid composition further comprises an alcohol or derivative thereof. Preferably, the alcohol or derivative thereof is an alkynyl alcohol or derivative thereof. More preferably, the alkynyl alcohol or derivative thereof is propargyl alcohol or a derivative thereof. Preferably, the alkynyl alcohol or derivative thereof is present in a concentration ranging from 0.01 to 5% w/w. More preferably, the alkynyl alcohol or derivative thereof is present in a concentration of 0.2% w/w.

[0060] Preferably, the metal iodide is present in a concentration ranging from 0.1 to 2% by weight of the total weight of the composition.

[0061] Preferably, the main components in terms of volume and weight percent of the composition of the present invention comprise an amino acid, an alkanolamine and a strong acid, such as HCl, nitric acid, sulfuric acid, sulfonic acid. An alkanolamine according to the present invention contains at least one amino group, —NH.sub.2, and one alcohol group, —OH. Preferred alkanolamines according to the present invention include, but are not limited to, monoethanolamine, diethanolamine and triethanolamine. More preferred are monoethanolamine, diethanolamine. Most preferred alkanolamine is monoethanolamine. Most preferred as amino acid is lysine monohydrochloride. When added to hydrochloric acid a Lewis acid/base adduct is formed where the primary amino group of lysine and monoethanolamine act as a Lewis base and the proton of the HCl as Lewis acid. The formed adduct greatly reduces the hazardous effects of the hydrochloric acid on its own, such as the fuming effect, the hygroscopicity, and the highly corrosive nature while also providing a distinct advantage to acid flux (wormholing) efficiency at low injection rates. Various organic acids are also contemplated according to a preferred embodiment of the present invention.

[0062] The molar ratio of the three main components (amino acid, alkanolamine and acid) can be adjusted or determined depending on the intended application, formation properties (permeability, porosity, mineralogy), along with the desired solubilizing ability. According to a preferred embodiment where the strong acid is HCl, one can increase the ratio of the HCl component to increase the solubilizing ability of the composition while still providing at least one of the following advantages: health; safety; environmental; and operational advantages over hydrochloric acid, such as low corrosion rates and thermal stability.

[0063] While an alkanolamine such as monoethanolamine is a compound known by the person of ordinary skill in the art, the latter knows that such a compound is not to be mixed with a strong acid such as HCl. In fact, the person skilled in the art will note upon review of the DOW safety data sheet for monoethanolamine LFG 85 that it indicates that one must avoid contact of this compound with strong acids.

[0064] Various corrosion inhibitors can be incorporated into a preferred composition of the present invention which comprises a strong acid and an alkanolamine to reduce corrosion on the steel which is contacted by the composition according to the present invention. According to a preferred embodiment of the present invention, the composition may further comprise organic compounds which may act as corrosion inhibitors selected from the group consisting of: acetylenic alcohols, aromatic or aliphatic aldehydes (e.g. α,β-unsaturated aldehydes), alkylphenones, amines, amides, nitrogen-containing heterocycles (e.g. imidazoline-based), iminium salts, triazoles, pyridine and its derivatives or salts, quinoline derivatives, thiourea derivatives, thiosemicarbazides, thiocyanates, quaternary amine salts, and condensation products of carbonyls and amines. Intensifiers which can be incorporated into compositions according to the present invention are selected from the group consisting of: formic acid, potassium iodide, antimony oxide, copper iodide, sodium iodide, lithium iodide, aluminium chloride, bismuth oxide, calcium chloride, magnesium chloride and combinations of these. Preferably, an iodide compound such as potassium iodide is used.

[0065] Other additives can be optionally added to a composition according to a preferred embodiment of the present invention. A non-limiting list of such common additives includes iron control agents (e.g. reducing agents), water-wetting surfactants, non-emulsifiers, de-emulsifiers, foaming agents, anti-sludging agents, clay and/or fines stabilizer, scale inhibitors, mutual solvents, friction reducers.

[0066] Alcohols and derivatives thereof, such as alkyne alcohols and derivatives and preferably propargyl alcohol and derivatives thereof can be used as corrosion inhibitor components. Propargyl alcohol itself is traditionally used as a corrosion inhibitor which works well at low concentrations. It is however a very toxic/flammable chemical to handle as a concentrate, so care must be taken when exposed to the concentrate. In the composition according to the present invention, it is preferred to use 2-Propyn-1-ol, complexed with methyloxirane, as this is a much safer derivative to handle. BASF—Basocorr® PP is an example of such a compound.

[0067] Metal iodides or iodates such as potassium iodide, sodium iodide, cuprous iodide and lithium iodide can potentially be used as corrosion inhibitor intensifier along with the composition according to preferred embodiments of the present invention. In fact, potassium iodide is a metal iodide traditionally used as corrosion inhibitor intensifier, however it is expensive, but works extremely well. It is non-regulated and safe to handle. The iodide or iodate is preferably present in a weight percentage ranging from 0.1 to 5 wt %, more preferably from 0.2 to 3 wt %, yet even more preferably from 0.25 to 2 wt %.

Process to Prepare a Composition According to a Preferred Embodiment of the Invention

Example 1

Preparation of the MEA-HCl component

[0068] Monoethanolamine (MEA) and hydrochloric acid are used as starting reagents. To obtain a 1:4.1 molar ratio of MEA to HCl, one must first mix 165 g of MEA with 835 g of water. This forms the monoethanolamine solution. Subsequently, one takes 370 ml of the previously prepared monoethanolamine solution and mixes with 350 ml of HCl aq. 36% (22 Baume). In the event that additives are used, they are added after thorough mixing of the MEA solution and HCl. For example, potassium iodide can be added at this point as well as any other component desired to optimize the performance of the composition according to the present invention. Circulation is maintained until all products have been solubilized. Additional products can now be added as required.

[0069] The resulting composition of this step is a clear (slightly yellow) liquid having shelf-life of greater than 1 year. It has a boiling point temperature of approximately 100° C. It has a specific gravity of 1.1±0.02. It is completely soluble in water and its pH is less than 1. The freezing point was determined to be less than −35° C.

[0070] The composition is biodegradable and is classified as non-corrosive to dermal tissue in a concentrate form, according to the classifications and 3.sup.rd party testing for dermal corrosion. The composition is substantially lower fuming or vapor pressure compared to 15% HCl. Toxicity testing was calculated using surrogate information and the LD.sub.50 was determined to be greater than −1300 mg/kg.

Example 2

Preparation of the Lysine-HCl Component

[0071] Lysine mono-hydrochloride is used as starting reagent. To obtain a 1:2.1 molar ratio of lysine to HCl, 370 ml of a 50 wt % lysine-HCl (also referred to as L50) solution and 100 ml HCl aq. 36% (22 Baume) are combined. In the event that additives are used, they are added after thorough mixing. For example, propargyl alcohol, and potassium iodide can be added at this point. Circulation is maintained until all products have been solubilized. Additional components can now be added as required. The process to obtain other compositions according to the present invention is similar where the only difference lies in the amount of HCl added.

[0072] The resulting composition of this step is an amber colored liquid with a fermentation like odour having shelf-life of greater than 1 year. It has a freezing point temperature of approximately minus 30° C. and a boiling point temperature of approximately 100° C. It has a specific gravity of 1.15±0.02. It is completely soluble in water and its pH is less than 1.

[0073] The composition is biodegradable and is classified as non-corrosive to dermal tissue according to the classifications and 3.sup.rd party testing for dermal corrosion. The composition is substantially low fuming/low vapor pressure compared to HCl. Toxicity testing was calculated using surrogate information and the LD.sub.50 was determined to be greater than 2000 mg/kg.

[0074] To obtain a Lysine-HCl composition where the ratio is 1:4.5, one can use the following mixing ratio: 370 ml of the L50 solution (described above)+300 ml 22Baume HCl; which leads to the following ratio: 1 mol lysine to 4.5 mol HCl.

Example 3

Blending the MEA-HCl composition and Lysine-HCl Composition

[0075] After mixing the lysine-HCl (1:4.5 ratio) composition obtained in step 2 with the MEA-HCl composition obtained in step 1, the resulting blend was left to age for at least 24 hrs to get the superior corrosion rates. It was noted that a longer aging time than 24 hours didn't increase the corrosion protection any further. This is indicative of a possible reaction between the components of the modified acids.

[0076] According to a preferred embodiment of the present invention, the composition comprising an alkanolamine and a strong acid may further comprise a corrosion inhibition package itself comprising a terpene; a cinnamaldehyde or a derivative thereof; at least one amphoteric surfactant; and a solvent.

[0077] According to a preferred embodiment of the present invention, the composition comprising an alkanolamine, an amino acid and HCl can be adapted for their intended use and/or the geological formation of interest by varying the amount of alkanolamine versus the amount of amino acid. Preferably, the proportion of alkanolamine:amino acid can vary between 1%:99% by weight to 99%:1% by weight in terms of the total combined weight of alkanolamine and amino acid. More preferably, the proportion of alkanolamine:amino acid can vary between 20%:80% by weight to 80%:20% by weight in terms of the total combined weight of alkanolamine and amino acid. Even more preferably, the proportion of alkanolamine:amino acid can vary between 40%:60% by weight to 60%:40% by weight in terms of the total combined weight of alkanolamine and amino acid.

[0078] According to another preferred embodiment, the proportion of alkanolamine:amino acid can be established based on moles and can vary between 1%:99% to 99%:1% in terms of total combined moles of alkanolamine and amino acid. More preferably, the proportion of alkanolamine:amino acid can vary between 20%:80% to 80%:20% in terms of total combined moles of alkanolamine and amino acid. Even more preferably, the proportion of alkanolamine:amino acid can vary between 40%:60% to 60%:40% in terms of total combined moles of alkanolamine and amino acid.

[0079] In other preferred embodiments of the present invention, 2-Propyn-1-ol, complexed with methyloxirane can be present in a range of 0.05-5.0 wt/wt %, preferably it is present in an amount ranging from 0.1 to 3 wt %, even more preferably from 0.5 to 2.0 wt/wt % and yet even more preferably from 0.75 to 1.5 wt/wt %. As a substitute for potassium iodide one could use sodium iodide, copper iodide and lithium iodide. However, potassium iodide is the most preferred.

Corrosion Testing

[0080] Compositions according to preferred embodiments of the present invention were exposed to corrosion testing. The results of the corrosion tests and comparative corrosion testing are reported in Tables 1 through 9. The controls used were compositions of HCl. Various steel grades were studied to the listed compositions for various periods of time at varying temperatures.

TABLE-US-00001 TABLE 1 Corrosion testing carried out for 4 hours at 150° C. on L80 steel coupons (28.0774 cm2 of surface area, 7.86 g/cc density) Corrosion Initial Final Loss mm/ Pit Fluid Package Wt. (g) wt. (g) wt. (g) Mils/yr year lb/ft2 Index  50% Ex. 1 2.25% CI-5 60.0321 59.8039 0.228 891.550 22.645 0.017 Aged −50% Ex. 2 2.25% CI-1A over night  60% Ex. 1 2.25% CI-5 60.6072 60.3521 0.255 996.645 25.315 0.019 Aged −40% Ex. 2 2.25% CI-1A over night  70% Ex. 1 2.25% CI-5 60.9507 60.6541 0.297 1158.781 29.433 0.022 Aged −30% Ex. 2 2.25% CI-1A over night Ex. 2 2.25% CI-5 59.3822 58.9717 0.410 1603.774 40.736 0.030 2.25% CI-1A Ex. 1 2.25% CI-5 60.762 60.4415 0.321 1252.155 31.805 0.023 2.25% CI-1A  40% Ex. 1 2.25% CI-5 60.2844 59.7324 0.552 2156.598 54.778 0.040 No −60% Ex. 2 2.25% CI-1A aging  30% Ex. 1 2.25% CI-5 60.2114 59.6191 0.592 2314.045 58.777 0.043 No −70% Ex. 2 2.25% CI-1A aging  30% Ex. 1 2.25% CI-5 60.7239 60.4275 0.296 1157.999 29.413 0.022 Aged −70% Ex. 2 2.25% CI-1A over weekend  50% Ex. 1 2.25% CI-5 60.1527 59.9403 0.212 829.821 21.077 0.016 Aged −50% Ex. 2 2.25% CI-1A over weekend  70% Ex. 1 2.25% CI-5 60.2004 60.0115 0.189 738.010 18.745 0.014 Aged −30% Ex. 2 2.25% CI-1A over weekend  20% Ex. 1 2.25% CI-5 59.8395 59.4999 0.340 1326.777 33.700 0.025 −80% Ex. 2 2.25% CI-1A  30% Ex. 1 2.25% CI-5 60.5763 60.3084 0.268 1046.653 26.585 0.020 −70% Ex. 2 2.25% CI-1A  50% Ex. 1 2.25% CI-5 60.1352 59.9172 0.218 851.700 21.633 0.016 −50% Ex. 2 2.25% CI-1A  70% Ex. 1 2.25% CI-5 60.191 60.0342 0.157 612.599 15.560 0.011 −30% Ex. 2 2.25% CI-1A  80% Ex. 1 2.25% CI-5 60.2361 60.0446 0.191 748.168 19.003 0.014 −20% Ex. 2 2.25% CI-1A CI-1A is a 10 wt % solution in water of potassium iodide and CI-5 is a proprietary corrosion inhibitor blend comprising: a terpene; a propargyl alcohol or derivative thereof; at least one amphoteric surfactant; and a solvent.?

TABLE-US-00002 TABLE 2 Corrosion testing using various compositions according to preferred embodiments of the present invention using J55 steel with an exposure time of 6 hours (steel surface area 28.922 cm2, density of 7.86 g/cc) Fluid % T CI Difference Mils/yr mm/year lb/ft2 Pit 30% 50  90 0.35% 0.081 203.799  5.176 0.006 0 50% 50  90 0.35% 0.077 194.949  4.952 0.005 0 70% 50  90 0.35% 0.085 215.430  5.472 0.006 0 30% 90 120 0.75% 0.177 447.802 11.374 0.013 1 50% 90 120 0.75% 0.137 347.167  8.818 0.010 1 70% 90 120 0.75% 0.094 238.440  6.056 0.007 0

TABLE-US-00003 TABLE 3 Corrosion testing using various compositions according to preferred embodiments of the present invention using N80 steel with an exposure time of 6 hours at 90° C. (steel surface area 28.0774 cm2, density of 7.86 g/cc) Fluid % CI Differe Mils/ mm/y lb/ft2 Pit 30% Ex. 50 0.35% CI- 0.099 257.5 6.543 0.007 3 50% Ex. 50 0.35% CI- 0.105 274.5 6.973 0.008 3 70% Ex. 50 0.35% CI- 0.096 249.2 6.331 0.007 4

TABLE-US-00004 TABLE 4 Corrosion testing using various compositions according to preferred embodiments of the present invention using P110 steel with an exposure time of 6 hours (steel surface area 28.922 cm2, density of 7.86 g/cc) Fluid % T Corrosio Differenc Mils/y mm/ye lb/ft2 Pit 30% Ex. 1 50 90 0.35% CI- 0.130 327.69  8.324 0.009 3 50% Ex. 1 50 90 0.35% CI- 0.121 304.68  7.739 0.009 3 70% Ex. 1 50 90 0.35% CI- 0.111 280.66  7.129 0.008 3 30% Ex. 1 90 12 0.75% CI- 0.101 254.37  6.461 0.007 0 50% Ex. 1 90 12 0.75% CI- 0.188 475.36 12.074 0.013 2 70% Ex. 1 90 12 0.75% CI- 0.170 430.60 10.937 0.012 0

TABLE-US-00005 TABLE 5 Corrosion testing using a various composition according to preferred embodiments of the present invention (at 90% strength) using L80 steel with an exposure time of 6 hours at 120° C. (steel surface area 28.0774 cm2, density of 7.86 g/cc) Fluid Fluid CI Difference Mils/yr mm/year lb/ft2 Pit 30% 90 0.75% 0.136 353.963  8.991 0.010 1 50% 90 0.75% 0.173 450.073 11.432 0.013 3 70% 90 0.75% 0.159 413.869 10.512 0.012 4

TABLE-US-00006 TABLE 6 Comparative Corrosion testing comparison between MEA-HCl using no additive - run time of 6 hours on 1018 steel coupons at a temperature of 110° C. having a surface area of 41.4 cm.sup.2 (coupon density of 7.86 g/cc) Initial Final Loss Temp Corrosion Wt. wt. wt. Fluid ° C. Package (g) (g) (g) Mils/yr mm/year lb/ft2 15% 110 none 74.143 48.421 25.722 45436.180 1154.079 1.273 HCl Example 110 none 74.181 62.579 11.603 20495.131  520.576 0.574 1 diluted to 50%

TABLE-US-00007 TABLE 7 Comparative Corrosion testing on J-55 steel coupons having a density of 7.86 g/ml and a surface area of 28.922 cm.sup.2 at 70° C. for a period of 6 hours Initial Final Wt Addi- wt wt loss mm/ Fluid tives (g) (g) (g) Mils/yr year lb/ft2 Lysine- None 33.2827 30.8391 2.444 6178.7058 156.939 0.173 HCl 1:4 Lysine- None 35.0081 34.4093 0.599 1514.0813  38.458 0.042 HCl 1:4 + 50% Distilled water 15% HCl None 36.7962 34.6209 2.175 5500.3023 139.708 0.154 7.5% HCl None 36.8248 35.4207 1.404 3550.3032  90.178 0.100

TABLE-US-00008 TABLE 8 Corrosion testing comparison between MEA-HCl using various additives - run time varying between 2 and 6 hours on L-80 steel coupons at various temperatures having a surface area of 28.0774 cm.sup.2 (coupon density of 7.86 g/cc) Corro- mm/ Fluid Fluid Temp sion Loss Run Mils/yr year lb/ft2 Exam- 50% 130  2.0% 0.194 6 504.248 12.808 0.014 ple 1 CI-5 Exam- 50% 130  3.0% 0.276 6 718.345 18.246 0.020 ple 1 CI-5 Exam- 50% 150  2.0% 0.243 4 950.544 24.144 0.018 ple 1 CI-5 Exam- 50% 150  3.0% 0.231 4  903.6614 22.953 0.017 ple 1 CI-5 Exam- 50% 200  7.5% 0.355 2 2775.448  70.496 0.026 ple 1 CI-5 Exam- 50% 110 1.75% 0.077 6  200.0323  5.081 0.006 ple 1 CI- The dilution of the fluid is done by using the concentrate (Example 1) composition and diluting with tap water to half the original concentration. CI-1A refers to potassium iodide; CI-5 refers to a proprietary corrosion inhibitor package comprising a terpene; a cinnamaldehyde or a derivative thereof; at least one amphoteric surfactant; and a solvent.

TABLE-US-00009 TABLE 9 Corrosion testing comparison between MEA-HCl and DEA-HCl using various additives - run time varying between 2 and 6 hours on various steel coupons at a temperature of 110° C. having a surface area of 28.0774 cm.sup.2 (coupon density of 7.86 g/cc) Initial Final Loss Run Corrosion Wt. wt. wt. Time mm/ Steel Fluid Package (g) (g) (g) (hours) Mils/yr year lb/ft2 N80 Example 1.75% 61.2451 61.137 0.108 6 281.5558 7.152 0.008 1 diluted CI-5 1% to 50% CI-1A L80 50% 1.75% DEA:HCl CI-5 1% 60.5502 60.3834 0.167 4 651.6676 16.552 0.012 1:4.1 CI-1A N80 50% 1.75% DEA:HCl CI-5 1% 60.3421 60.236 0.106 4 414.52 10.529 0.008 1:4.1 CI-1A

TABLE-US-00010 TABLE 10 Corrosion test results for acid exposure of 4 hours at 150° C. of L80 steel coupons of 7.86 g/cc steel density (with a surface are of 28.0774 cm.sup.2) Corrosion Wt loss Mm/ Fluid % Package (g) Mils/yr year Lb/ft2 50% 90 2.25% CI-5 0.228 891.550062 22.645 0.017 Ex. 2 - 2.25% CI-1A 50% Ex. 1 40% 90 2.25% CI-5 0.255 996.6451394 25.315 0.019 Ex. 2 - 2.25% CI-1A 60% Ex. 1 30% 90 2.25% CI-5 0.297 1158.780668 29.433 0.022 Ex. 2 - 2.25% CI-1A 70% Ex. 1 Ex. 2 90 2.25% CI-5 0.410 1603.774323 40.736 0.030 2.25% CI-1A Ex. 1 90 2.25% CI-5 0.321 1252.155105 31.805 0.023 2.25% CI-1A 60% 90 2.25% CI-5 0.552 2156.597871 54.778 0.040 Ex. 2 - 2.25% CI-1A 40% Ex. 1 70% 90 2.25% CI-5 0.592 2314.045143 58.777 0.043 Ex. 2 - 2.25% CI-1A 30% Ex. 1 70% 90 2.25% CI-5 0.296 1157.999292 29.413 0.022 Ex. 2 - 2.25% CI-1A 30% Ex. 1 50% 90 2.25% CI-5 0.212 829.8213548 21.077 0.016 Ex. 2 - 2.25% CI-1A 50% Ex. 1 30% 90 2.25% CI-5 0.189 738.0096701 18.745 0.014 Ex. 2 - 2.25% CI-1A 70% Ex. 1 80% 90 2.25% CI-5 0.340 1326.776516 33.700 0.025 Ex. 2 - 2.25% CI-1A 20% Ex. 1 70% 90 2.25% CI-5 0.268 1046.653206 26.585 0.020 Ex. 2 - 2.25% CI-1A 30% Ex. 1 50% 90 2.25% CI-5 0.218 851.6998839 21.633 0.016 Ex. 2 - 2.25% CI-1A 50% Ex. 1 30% 90 2.25% CI-5 0.157 612.5988156 15.560 0.011 Ex. 2 - 2.25% CI-1A 70% Ex. 1 20% 90 2.25% CI-5 0.191 748.1675586 19.003 0.014 Ex. 2 - 2.25% CI-1A 80% Ex. 1

TABLE-US-00011 TABLE 11 Corrosion test results for acid exposure of 6 hours at 90° C. of variuos steel coupons of 7.86 g/cc steel density Steel Fluid Corrosion Wt loss Surface Mm/ type Fluid % Package (g) area (cm2) Mils/yr year Lb/ft2 J55 70% 50 0.35% CI-5 0.081 28.922 203.7991858 5.176 0.006 Ex. 2 - 0.15% CI-1A 30% Ex. 1 N80 70% 50 0.35% CI-5 0.099 28.0774 257.5936346 6.543 0.007 Ex. 2 - 0.15% CI-1A 30% Ex. 1 P110 70% 50 0.35% CI-5 0.130 28.922 327.6969538 8.324 0.009 Ex. 2 - 0.15% CI-1A 30% Ex. 1 J55 50% 50 0.35% CI-5 0.077 28.922 194.9493452 4.952 0.005 Ex. 2 - 0.15% CI-1A 50% Ex. 1 N80 50% 50 0.35% CI-5 0.105 28.0774 274.5234488 6.973 0.008 Ex. 2 - 0.15% CI-1A 50% Ex. 1 P110 50% 50 0.35% CI-5 0.121 28.922 304.6873683 7.739 0.009 Ex. 2 - 0.15% CI-1A 50% Ex. 1 J55 30% 50 0.35% CI-5 0.085 28.922 215.4304048 5.472 0.006 Ex. 2 - 0.15% CI-1A 70% Ex. 1 N80 30% 50 0.35% CI-5 0.096 28.0774 249.2589569 6.331 0.007 Ex. 2 - 0.15% CI-1A 70% Ex. 1 P110 30% 50 0.35% CI-5 0.111 28.922 280.6663725 7.129 0.008 Ex. 2 - 0.15% CI-1A 70% Ex. 1

TABLE-US-00012 TABLE 12 Corrosion test results for acid exposure of 6 hours at 120° C. of variuos steel coupons of 7.86 g/cc steel density Steel Fluid Corrosion Wt loss Surface Mm/ type Fluid % Package (g) area (cm2) Mils/yr year Lb/ft2 J55 70% 90 0.75% CI-5 0.177 28.922 447.801933 11.374 0.013 Ex. 2 - 0.5% CI-1A 30% Ex. 1 J55 50% 90 0.75% CI-5 0.137 28.922 347.1666031 8.818 0.010 Ex. 2 - 0.5% CI-1A 50% Ex. 1 J55 30% 90 0.75% CI-5 0.094 28.922 238.4399903 6.056 0.007 Ex. 2 - 0.5% CI-1A 70% Ex. 1 L80 70% 90 0.75% CI-5 0.136 28.0774 353.9633463 8.991 0.010 Ex. 2 - 0.5% CI-1A 30% Ex. 1 L80 50% 90 0.75% CI-5 0.173 28.0774 450.0725992 11.432 0.013 Ex. 2 - 0.5% CI-1A 50% Ex. 1 L80 30% 90 0.75% CI-5 0.159 28.0774 413.8688427 10.512 0.012 Ex. 2 - 0.5% CI-1A 70% Ex. 1 P110 70% 90 0.75% CI-5 0.101 28.922 254.3697033 6.461 0.007 Ex. 2 - 0.5% CI-1A 30% Ex. 1 P110 50% 90 0.75% CI-5 0.188 28.922 475.3628651 12.074 0.013 Ex. 2 - 0.5% CI-1A 50% Ex. 1 P110 30% 90 0.75% CI-5 0.170 28.922 430.607957 10.937 0.012 Ex. 2 - 0.5% CI-1A 70% Ex. 1

TABLE-US-00013 TABLE 13 Corrosion test results for acid exposure of 6 hours at 110° C. of J55 steel coupons of 7.86 g/cc steel density (coupon surface area is 28.0774 cm.sup.2) Fluid Concentration Wt loss Mils/yr Mm/year Lb/ft2 70% 90 No 4.522 11433.23546 290.404 0.321 50% 90 No 4.451 11253.45727 285.838 0.315 30% 90 No 4.609 11653.72292 296.005 0.327 15% No 3.815 9647.084783 245.036 0.270 Ex.2 90 No 4.094 10351.78494 262.935 0.290 Ex. 1 90 No 6.524 16495.59712 418.988 0.462

TABLE-US-00014 TABLE 14 Corrosion test results for acid exposure of 3 hours at 190° C. of L80 steel coupons of 7.86 g/cc steel density (coupons surface area is 28.0774 cm.sup.2) Fluid % Corrosion Wt loss Mils/yr Mm/year Lb/ft2 30% 90 5.0% CI-5 2.020 10523.57251 267.299 0.147 50% 90 5.0% CI-5 2.455 12789.56303 324.855 0.179 70% 90 5.0% CI-5 1.992 10376.1529  263.554 0.145

[0081] With respect to the corrosion impact of the composition on typical oilfield grade steels, it was established that the compositions according to preferred embodiments of the present invention were clearly well below the acceptable corrosion limits set by industry for certain metals, such as L80 and typical coiled tubing grades of metal.

[0082] In light of the corrosion tests carried out at 90/120/150° C., one notes a positive synergistic effect in the use of the amino acid and an alkanolamine with a mineral acid. This means that the corrosion rate of the hybrid is lower than the educts, but it's also lower with a higher amino acid (in the case of the tests, lysine) content. This is special as the corrosion rates of the Lysine-HCl are higher than those of MEA-HCl on its own.

[0083] The composition according to a preferred embodiment of the present invention should show superior corrosion rates in sour conditions, as the MEA acts as a H.sub.2S scavenger in conditions up to temperature of 110° C.

[0084] The corrosion testing carried out helps to determine the positive impact of the use of such modified acid compositions according to the present invention compared to the industry standard HCl blends with full additive loadings when exposed to a variety of temperatures. The results obtained using HCl and Lysine-HCl and MEA-HCl were used as a baseline to compare with the compositions according to preferred embodiment of the present invention. In addition, the temperatures of some of the testing was above 90° C., the temperature at which urea decomposition into ammonia and carbon dioxide begins to occur.

[0085] Additionally, compositions according to preferred embodiments of the present invention will allow the end user to utilize an alternative to conventional acids that have the many down-hole performance advantages, transportation and storage advantages as well as the health, safety and environmental advantages. Enhancement in corrosion control is an advantage of the present invention versus the use of HCl at temperatures above and below 90° C. The reduction in skin corrosiveness, the controlled spending nature or proton donation, and the higher spent pH, salinity tolerance are other advantages depending on the preferred embodiments of the compositions according to the present invention.

Dissolution Testing

[0086] In order to assess the effectiveness of the modified acid according to a preferred embodiment of the present invention, dissolution testing was carried out to study the dissolution power of various compositions upon exposure to calcium carbonate and crushed dolomite. The tests were carried out at a temperature of 23° C. and were compared to the efficacy of a solution of 15% HCl and 28% HCl. The results are reported in Table 15 and 16 below.

TABLE-US-00015 TABLE 15 Dissolution results for various acid compositions and total solubility of calcium carbonate Acid Total Initial Final Weight Solubility Solubility- Fluid Weight Weight Loss/g % kg/m.sup.3 HCl 15% 20.0142 9.3023 10.7119 53.52 214 HCl 15% 25.0018 15.4885 9.5133 38.05 190 HCl 28% 20.0032 0.9922 19.011 95.04 380 HCl 28% 25.0024 3.84442 21.15798 84.62 423 MEA:HCl 1:5.8 15.0432 3.5958 11.4474 76.10 229 MEA:HCl 1:3.5 15.0434 5.9654 9.078 60.35 182 MEA:HCl 1:3.8 15.0422 5.0306 10.0116 66.56 200 MEA:HCl 1:4.1 15.0134 4.1962 10.8172 72.05 216 MEA:HCl 1:4.7 15.0513 3.5523 11.499 76.40 230 MEA:HCl 1:6.4 15.0328 1.4028 13.63 90.67 273 MEA:HCl 1:7 15.00576 0.2064 14.79936 98.62 296 MEA:HCl 1:9.9 18.5574 6.4458 18.5594 74.22 371 DEA:HCl 1:3.5 15.0222 5.6072 9.415 62.67 188 DEA:HCl 1:4 15.0356 4.0526 10.983 73.05 220 Lysine HCl 1:2 15.001 8.851 6.15 41.00 123 Lysine HCl 1:3 15.032 5.2723 9.7597 64.93 195 Lysine HCl 1:4 15.007 2.1423 12.8647 85.72 257 Lysine HCl 1:5 15.024 1.5857 13.4383 89.45 269 Lysine HCl 1:6 20.014 4.8421 15.1719 75.81 303 Lysine HCl 1:7 20.052 2.7721 17.2799 86.18 346 Lysine HCl 1:9 20.0023 2.2158 17.7865 88.92 356 Lysine HCl 1:9 25.0012 6.8558 18.1454 72.58 363 Lysine HCl 1:12.5 20.0015 0.1516 19.8499 99.24 397 70% Ex. 2 - 15.0123 2.827 12.1853 244 30% Ex. 1* 50% Ex. 2 - 15.0064 3.0999 11.9065 238 50% Ex. 1* 30% Ex. 2 - 15.0071 3.5441 11.463 229 70% Ex. 1* *indicates that the dissolution was performed at 20° C.

TABLE-US-00016 TABLE 16 Acid Solubility Test with Crushed Dolomite (at 23° C.) using a volume of 50 ml of composition Acid Total Initial Final Weight Solubility Solubility - Fluid Weight Weight Loss/g % kg/m.sup.3 Example 1 15.032 5.5323 9.4997 63.20 190 Example 1 10.0318 5.198 4.8338 48.18 97 diluted at 50% 30% Ex. 2 - 14.9963 9.4408 5.5555 111.11 70% Ex. 1* 50% Ex. 2 - 14.9925 9.247 5.7455 114.91 50% Ex. 1* 30% Ex. 2 - 15.0071 9.0923 5.9148 118.30 70% Ex. 1* *indicates that the dissolution was performed at 20° C.

[0087] The above dissolution test confirms that the compositions according to a preferred embodiment of the present invention provide comparable dissolution performance in comparison to a mineral acid of similar concentration and modified acids as well.

[0088] As well, wormholing/acid flux efficiency testing has shown a far superior property of the composition comprising a 50% content of MEA-HCl and 50% content of Lysine-HCl over 15% or 28% HCl at various injection rates

Spend/Reaction Rate (Hydrogen Proton Donation)

[0089] Tests were conducted to assess the reactivity of the compositions according to preferred embodiment of the present invention.

[0090] Determination of Reaction Rate of Modified Acid at 60° C.

[0091] A predetermined amount of modified acid was heated to 60° C. in a water bath. The solution was then placed on a balance and a pre-weighed calcium carbonate sample was submerged in the heated solution. The weight was recorded at every 1 minute interval for 30 minutes. From the recorded weight, the weight loss percentage was calculated and plotted as a function of time.

[0092] Based on the data obtained, the two varying concentrations (50% and 90%) of the same composition according to a preferred embodiment of the present invention had their spend rates plotted for five ratios of Lysine-HCl: MEA-HCl (80:20, 70:30, 50:50, 30:70 and 20:80). The graphical representation of the testing is illustrated in FIGS. 1 to 5.

[0093] Although this invention exhibits a more methodical reaction rate when compared to 15% HCl, it is more reactive than most typical modified, complexed or synthetic acids at concentrations from 33% to 90%, coming very close to the reaction rate of a 15% HCl at even a 33% dilution. Having a safer modified acid system that reacts substantially faster than other safer modified acid systems is advantageous in a spearhead application where the purpose of the acid is to clean up residual cement from perforations and assist in reducing the breakdown or reduce pressure during the early stages of a stimulation treatment (frac or matrix water-based). It is advantageous to have an acid system that can be stored on location as a concentrate (providing a high level of safety even in concentrate form) that can then be deployed and diluted or blended to the desired concentration on the fly with fresh or produced (high salinity) water. When difficult areas of the well treatment are encountered (high breakdown pressures nearing the maximum allowable pressure of the treating equipment) the concentration can be increased, thereby reducing the time it takes to achieve the desired injection rate of the following fluid system.

Wormholing Testing

[0094] Numerous studies of the wormholing process in carbonate acidizing have shown that the dissolution pattern created by the flowing acid can be characterized as one of three types (1) compact dissolution, in which most of the acid is spent near the rock face; (2) wormholing, in which the dissolution advances more rapidly at the tips of a small number of highly conductive micro-channels, i.e. wormholes, than at the surrounding walls; and (3) uniform dissolution.

[0095] The dissolution pattern that is created depends on the interstitial velocity, which is defined as the acid velocity flowing through the porous medium. Interstitial velocity is related to the injection rate (interstitial velocity=injection rate/(area of low porosity). Compact dissolution patterns are created at relatively low injection rates, wormhole patterns are created at intermediate rates and uniform dissolution patterns at high rates.

[0096] This interstitial velocity at the wormhole tip controls the wormhole propagation. The optimal acid injection rate is then calculated based on a semi-empirical flow correlation. At optimal injection rate, for a given volume, acid penetrates the furthest into the formation, resulting in the most efficient outcome of the acid stimulation. Wormhole structures change from large-diameter at low interstitial velocity to thin wormholes at optimal velocity conditions, to more branched patterns at high interstitial velocity.

[0097] This series of experimental testing study examined a comparative composition having a lysine:HCl molar ratio of 1:4.5 (see example 2). This composition is designed as a low-hazard/low-corrosion aqueous synthetic acid enhanced through the addition of proprietary oilfield chemistry to replace standard HCl blends, especially for high to ultra-high temperature and/or safety critical applications (i.e. offshore applications). This was compared to a composition comprising 90% (by volume) of lysine:HCl molar ratio of 1:4.5 and 50% of MEA-HCl in a molar ratio of 1:4.1 (example 3).

[0098] The acid system according to the present invention was compared to 15% HCl under the exact same testing conditions. The wormhole efficiency curve (pore volume to breakthrough vs interstitial velocity) was determined for both acid systems for comparison. One of the observations which stems from FIG. 6 is that the MEA-lysine:HCl composition (in a 50-50 mixture by volume) has similar optimal pore volume of breakthrough at a 40% lower of optimal interstitial velocity compared with HCl. This allows one to perform matrix acidizing with a composition according to the present invention rather than have recourse to a fracking operation and associated equipment when using HCl. Of course, the ratio of MEA and Lysine may be adjusted to suit various conditions determined by the geological formations in order to consistently provide optimal velocities.

Test Parameters

[0099] Two series of matrix acidizing experiments were conducted in order to evaluate the performance of above mentioned composition according to the present invention (composition of example 3 at a 90% concentration) vs lysine:HCl in a 1:4.5 molar ratio (at a 90% concentration)) and vs 15% HCl (see FIG. 6).

[0100] Another series of matrix acidizing experiments of the composition according to the present invention (composition of example 3 at 90% concentration) vs MEA-HCl in a 1:4.1 molar ratio (at a 90% concentration) and vs 15% HCl (see FIG. 7)

[0101] Each one of the compositions used in the experiments comprised 0.3 vol % common commercial corrosion inhibitor, and the other set of experiments utilized a 15% solution of HCl with 0.3 vol % of a corrosion inhibitor. The experiments were conducted utilizing Indiana limestone cores.

[0102] All cores were 1.5-inch in diameter and 8-inch in length. The average porosity of the core samples was 14% and the average permeability was 13 mD. The back pressure used in these experiments was 2000 psi. The testing temperature was 180° F. (82° C.). The limestone cores were selected as they help in simulating the geology encountered most commonly in oilfields in North America.

Test Procedure

[0103] The matrix acidizing apparatus consists of a pumping system, an accumulation system, a core containment cell, a pressure maintaining system, a heating system and a data acquisition system. A Teledyne Isco® syringe pump was used to inject water and acid at constant rates. A back-pressure regulator was used to maintain the desired minimum system pressure at 2000 psi.

[0104] Confining pressure was set to 400-500 psi higher than the injection pressure to avoid fluid leaking. Two heating tapes were used to heat the core holder and the injection fluid for the high-temperature tests. During the experiment, the system was first pressurized by injecting water, once the flow reached a steady state; permeability was calculated from the measured pressure differential across the core containment cell. The system was then heated to the experiment temperature. When the full system; fluid, core containment cell and core reached the target temperature, water injection was ceased and acid injection commenced.

[0105] Injection was ceased when wormholes breach the core and acid injection time was recorded for the breakthrough pore volume calculation. For each experimental condition, 4-6 individual tests were performed with the same temperature and pressure parameters. The only condition that changed was the injection rate. The rate varied in a range until the optimal condition was identified. The Buij se and Glasbergen (2005) model was utilized to generate the wormhole efficiency relationship by fitting the experimental data obtained.

Core Properties

[0106] The cores utilized for testing were 1.5 inches in diameter and 8 inches long. Indiana limestone samples were obtained from one sample of outcrop to ensure linear properties.

Experimental Results

[0107] The experimental results for HCl are listed in Table 12 below. The experimental results for the composition of Example 3 are listed in Table 13 and the experimental result for Example 2 are listed in Table 14.

TABLE-US-00017 TABLE 12 Wormholing Experiment #1 - Experimental Results for HCl Acid injection Interstitial rate Velocity Pore Volume to Core# (ml/min) (cm/min) Breakthrough IC2 10 6.39 0.52 IC1 8 4.53 0.60 IC3 7 4.97 0.60 IC5 5 3.47 0.51 IC6 3 2.10 0.47 IC16 2 1.56 0.64 IC18 0.8 0.62 2.93

TABLE-US-00018 TABLE 13 Experimental Results for the Lysine-HCl - MEA-HCl composition (Example 3) Acid injection rate Interstitial Velocity Pore Volume Core# (ml/min) (cm/min) to Breakthrough IC101 2 1.3 0.58 IC102 5 3.27 0.61 IC201 1 0.64 0.78 IC202 0.8 0.5 1.34

TABLE-US-00019 TABLE 14 Experimental Results for the MEA-HCl composition of Example 1 Acid Interstitial injection rate Velocity Pore Volume Core# (ml/min) (cm/min) to Breakthrough IC111 10 6.37 0.63 IC108 5 3.01 0.46 IC112 3 1.92 0.49 IC109 2 1.2 0.57 LDA16 1 0.57 2.11

[0108] The optimal condition for two sets of experiments with Buij se and Glasbergen equation are listed in Table 15. The CT scans for both acid systems under the same conditions of 3 ml/min and a (2.1 cm/min) interstitial velocity were done. The CT scans reveal that the wormholing followed conventional pattern. The wormholes are more branched at low interstitial velocity and are more uniform and straight at high interstitial velocity. Thus, low interstitial velocity is more desirable as it provides a more spread wormholing pattern and, in practice, will unlock more hydrocarbon from hydrocarbon-bearing formations.

[0109] The optimal condition for the experiments are listed in Table 15.

TABLE-US-00020 TABLE 15 Optimal Condition Obtained from Experimental Results Optimal Condition Lys-HCl - HCl MEA-HCl MEA-HCl PVbt-opt 0.46 0.41 0.47 Vi-opt 1.97 1.62 1.17 PVbt-opt difference 11%  2% Vi-opt difference 18% 40%

[0110] Preliminary observations of wormhole efficiency tests: the optimal interstitial velocity for the composition of Example 1 is lower by 18% compared to HCl providing a potential advantage over conventional HCl acid systems, the composition of Example 3 was lower by 40% compared to the same HCl content. The objective is to obtain fast wormhole propagation (high stimulation efficiency) without being limited by injection rate in the field and the Example 3 composition exhibits this effect; and the optimal pore volume to breakthrough for the Example 3 composition is similar to the one from the 15% HCl composition. With retarding or corrosion prevention features, other acid systems usually have increased pore volume to breakthrough because of reduced reaction rates.

Dermal Testing

[0111] Each one of the two components (Lysine-HCl and MEA-HCl) has been extensively studied for dermal irritation. The results consistently show that they have advantageous properties to minimize skin irritation compared to the mineral acid counterpart (i.e. HCl alone). The combination of the two components (in a 50:50 proportion by volume) according to a preferred embodiment of the present invention (Example 3) was tested on human skin.

[0112] A few drops of the composition of Example 3 were placed on the back of the hand of an individual, visual assessment was done by looing at the skin with the drops at time intervals of 15, 30, 45 and 60 minutes. Visual analysis of the skin during and after the dermal test showed no redness at any time during the testing and at the end of the testing (time=60 minutes).

Uses of Compositions According to Preferred Embodiments of the Present Invention

[0113] While the compositions according to preferred embodiment of the present invention can be used at full strength (undiluted) for a wide range of application, the uses (or applications) of the compositions according to the present invention upon dilution thereof ranging from approximately 1 to 90% dilution, include, but are not limited to: injection/disposal well treatments; matrix acid squeezes or stimulations, scale treatment soaks or bullheads; acid fracturing, acid washes; fracturing spearheads (breakdowns); pipeline scale treatments, cement breakdowns or perforation cleaning for abandonment or remedial purposes; pH control; and de-scaling applications, high temperature (up to 190° C.) cyclical steam scale treatments and steam assisted gravity drainage (SAGD) scale treatments (up to 190° C.). The various potential applications are summarized in Table 16. As would be understood by the person skilled in the art, the methods of use generally comprise the following steps: providing a composition according to a preferred embodiment of the present invention; exposing a surface (such as a metal surface) to the aqueous modified acid composition; allowing the aqueous modified acid composition a sufficient period of time to act upon said surface; and optionally, removing the acid composition when the exposure time has been determined to be sufficient for the operation to be complete or sufficiently complete. Another method of use comprises: injecting the aqueous modified acid composition into a well and allowing sufficient time for the aqueous modified acid composition to perform its desired function, subsequently removing the acid composition from the well to stop the acid exposure. Yet another method of use comprises: exposing the aqueous modified acid composition to a body of fluid (typically water) requiring a decrease in the pH and allowing sufficient exposure time for the aqueous modified acid composition to lower the pH to the desired level.

TABLE-US-00021 TABLE 16 Applications for which compositions according to the present invention can be used as well as proposed dilution ranges Suggested Application Dilution Benefits Injection/Disposal 10-75% Compatible with mutual solvents and solvent blends, Wells very cost effective. Squeezes & Soaks 33%-75% Ease of storage & handling, cost effective compared - Bullhead to conventional acid stimulations. Ability to leave - Annular pump equipment in wellbore. Acid Fracs/matrix 50%-90% Decreased shipping and storage compared to treatments. conventional acid, no blend separation issues, Produciton well and comprehensive spend rate encourages deeper pipeline scale formation penetration. treatments Frac Spearheads 33%-90% Able to adjust concentrations on the fly. Decreased (Break-downs) shipping and storage on location. Cement Break-downs 20-90% Higher concentrations recommended due to lower temperatures, and reduced solubility of aged cement. pH Control  0.1%-10.0% Used in a variety of applications to adjust pH level of water based systems. Liner De-Scaling,  1%-75% Continuous injection/de-scaling of slotted liners, Heavy Oil typically at very high temperatures.

[0114] The main advantages of the use of the modified acid composition included: the reduction of the total loads of acid, and the required number of tanks by delivering concentrated product to location and diluting with fluids available on location or close to location (with fresh or low to high salinity production water). Other advantages of the composition according to the present invention include: operational miscibility efficiencies which can lead to the elimination of having to periodically circulate tanks of HCl acid due to chemical separation of the corrosion and surfactant and other components; reduced corrosion to downhole tubulars and surface equipment; temperature corrosion protection up to 190° C., less facility disruptions due to iron precipitation, high thermal stability of a modified acid, and reduced hazardous HCl acid exposure to personnel and environment by having a low hazard, low fuming acid (lower vapour pressure) on location.

[0115] A modified acid composition according to a preferred embodiment of the present invention, can be used to treat scale formation in SAGD or CSS (cyclical stream) operations at high temperatures (up to 190° C.) while achieving acceptable corrosion limits set by industry. This also eliminates the need for the SAGD operation to be halted for a “cool down prior to a scale treatment and said modified acid is injected into said well to treat scale formation inside said well at high temperatures greatly reducing down-time and lost revenue for the operator.

[0116] While the foregoing invention has been described in some detail for purposes of clarity and understanding, it will be appreciated by those skilled in the relevant arts, once they have been made familiar with this disclosure that various changes in form and detail can be made without departing from the true scope of the invention in the appended claims.