Synthetic Acid Compositions Alternatives to Conventional Acids in the Oil and Gas Industry

Abstract

A synthetic acid composition for use in oil industry activities, said composition comprising: urea and hydrogen chloride in a molar ratio of not less than 0.1:1; and a metal iodide or iodate. Optionally, a phosphonic acid derivative may be added.

Claims

1-27. (canceled)

28. A synthetic acid composition for use in oil industry activities, said composition comprising: urea and hydrogen chloride in a molar ratio of not less than 0.1:1; a metal iodide or iodate; and optionally, a phosphonic acid derivative.

29. The synthetic acid composition according to claim 28, wherein the urea and hydrogen chloride are in a molar ratio of not less than 0.5:1.

30. The synthetic acid composition according to claim 29, wherein the urea and hydrogen chloride are in a molar ratio of not less than 1.0:1.

31. The synthetic acid composition according to claim 28, wherein the phosphonic acid derivative is aminoalkylphosphonic salt.

32. The synthetic acid composition according to claim 31, wherein the aminoalkylphosphonic salt is amino tris methylene phosphonic acid.

33. The synthetic acid composition according to claim 28, wherein the metal iodide or iodate is cuprous iodide.

34. The synthetic acid composition according to claim 28, wherein the metal iodide or iodate is potassium iodide.

35. The synthetic acid composition according to claim 28, wherein the metal iodide or iodate is sodium iodide.

36. The synthetic acid composition according to claim 31, wherein the aminoalkylphosphonic salt is present in a concentration ranging from 0.25 to 1.0% w/w.

37. The synthetic acid composition according to claim 36, wherein the aminoalkylphosphonic salt is present in a concentration of 0.5% w/w.

38. The synthetic acid composition according to claim 28, wherein the metal iodide is present in a concentration ranging from 100 to 1000 ppm.

39. The use of a synthetic acid composition in oil industry activities, said composition comprising: urea and hydrogen chloride in a molar ratio of not less than :1; a metal iodide or iodate; optionally, a phosphoric acid derivative; 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.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Urea-HCl is the main component in terms of volume and weight percent of the composition of the present invention, and consists basically of a carbonyl group connecting with nitrogen and hydrogen. When added to hydrochloric acid, there is a reaction that results in urea hydrochloride, which basically traps the chloride ion within the molecular structure. This reaction greatly reduces the hazardous effects of the hydrochloric acid on its own, such as the fuming effects, the hygroscopic effects, and the highly corrosive nature (the Cl— ion will not readily bond with the Fe ion). The excess nitrogen can also act as a corrosion inhibitor at higher temperatures. Urea & Hydrogen chloride in a molar ratio of not less than 0.1:1; preferably in a molar ratio not less than 0.5:1, and more preferably in a molar ratio not less than 1.0:1. However, this ratio can be increased depending on the application.

[0045] It is preferable to add the urea at a molar ratio greater than 1 to the moles of HCl acid (or any acid). This is done in order to bind any available Cl— ions, thereby creating a safer, more inhibited product. Preferably, the composition according to the present invention comprises 1.1 moles of urea per 1.0 moles of HCl. The urea (hydrochloride) also allows for a reduced rate of reaction when in the presence of carbonate-based materials. This again due to the stronger molecular bonds associated over what hydrochloric acid traditionally displays. Further, since the composition according to the present invention is mainly comprised of urea (which is naturally biodegradable), the product testing has shown that the urea hydrochloride will maintain the same biodegradability function, something that hydrochloric acid will not.

[0046] Metal iodides or iodates such as potassium iodide, sodium iodide and cuprous iodide can potentially be used as corrosion inhibitor intensifier. 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 friendly to handle.

[0047] Phosphonic acids and derivatives such as amino tris methylene phosphonic acid (ATMP) have some value as scale inhibitors. In fact, ATMP is a chemical traditionally used as an oilfield scale inhibitor, it has been found, when used in combination with urea/HCl, to increase the corrosion inhibition. It has a good environmental profile, is readily available and reasonably priced.

[0048] Amino tris (methylenephosphonic acid) and its sodium salts belong to the ATMP category in that all category members are various ionized forms of the acid. This category includes potassium and ammonium salts of that acid. The properties of the members of a category are usually consistent. Moreover, certain properties for a salt, in ecotoxicity studies, for example, can be directly appreciated by analogy to the properties of the parent acid. Amino tris (methylenephosphonic acid) may specifically be used as an intermediate for producing the phosphonates salts. The salt is used in situ (usually the case) or stored separately for further neutralization. One of the common uses of phosphonates is as scale inhibitors in the treatment of cooling and boiler water systems. In particular, for ATMP and its sodium salts are used in to prevent the formation of calcium carbonate scale.

[0049] According to an aspect of the invention, there is provided a synthetic acid composition comprising: [0050] urea & hydrogen chloride in a molar ratio of not less than 0.1:1; preferably in a molar ratio not less than 0.5:1, more preferably in a molar ratio not less than 1.0:1; [0051] optionally, a phosphonic acid or derivatives, preferably alkylphosphonic acid or derivatives thereof and more preferably amino tris methylene phosphonic acid and derivatives thereof; and [0052] metal iodide or iodates, preferably cupric iodide, potassium iodide, lithium iodide or sodium iodide.

[0053] The metal iodide or iodates should be present in an amount sufficient to have an effect but also to be reasonably acceptable with respect to safety. Preferably, they should be present in a concentration ranging from 100 to 1000 ppm.

EXAMPLE 1

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

[0054] Start with a 50% by weight solution of pure urea liquor. Add a 36% by weight solution of hydrogen chloride while circulating until all reactions have completely ceased. Potassium iodide is then added. Circulation is maintained until all products have been solubilized. Additional products are added now as required (corrosion inhibitor, demulsifier, etc.).

[0055] Table 1 lists the components of the composition of Example 1 including their weight percentage as compared to the total weight of the composition and the CAS numbers of each component.

TABLE-US-00001 TABLE 1 Composition of a preferred embodiment of the present invention Chemical % Wt Composition CAS# Water 60.95% 7732-18-5 Urea Hydrochloride  39.0% 506-89-8 Potassium Iodide 0.050% 7681-11-0

[0056] The resulting composition of Example 1 is a clear, odourless liquid 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.

[0057] The composition is biodegradable and is classified as a mild irritant according to the classifications for skin tests. The composition is non-fuming and has no volatile organic compounds nor does it have any BTEX levels above the drinking water quality levels. BTEX refers to the chemicals benzene, toluene, ethylbenzene and xylene. Toxicity testing was carried out on rats and the LD.sub.50 was determined to be greater than 2000 mg/kg.

[0058] With respect to the corrosion impact of the composition on typical oilfield grade steel, it was established that it was clearly well below the acceptable corrosion limits set by industry. This is true for the compositions even when exposed to temperatures exceeding 100° C.

[0059] Corrosion Testing

[0060] The composition according to the present invention of Example 1 was exposed to corrosion testing. The results of the corrosion tests are reported in Table 2.

[0061] Samples of J55 grade steel were exposed to various synthetic acid solutions for periods of time ranging up to 24 hours at 90° C. temperatures. All of the tested compositions contained HCl and urea in a 1:1.05 ratio.

TABLE-US-00002 TABLE 2 Corrosion testing comparison between HCl-Urea and the composition of Example 1 Surface Run Initial Final Loss area Density time Inhibitor (%) wt. (g) wt. (g) wt. (g) (cm2) (g/cc) (hours) Mils/yr Mm/year Lb/ft2 HCl-Urea 37.616 34.524 3.092 28.922 7.86 6 7818.20 198.582 0.222 HCl-Urea 37.616 31.066 6.550 28.922 7.86 24 4140.46 105.168 0.470 HCl-Urea + KI 37.568 36.275 1.293 28.922 7.86 6 3269.384 83.042 0.092 @ 500 ppm HCl-Urea + KI 37.568 34.887 2.681 28.922 7.86 24 1694.744 43.047 0.190 @ 500 ppm

[0062] This type of corrosion testing helps to determine the impact of the use of such synthetic replacement acid composition according to the present invention compared to the industry standard (HCl blends or any other mineral or organic acid blends). The results obtained for the composition containing only HCl and urea were used as a baseline to compare the other compositions. Additionally, the compositions according to the present invention will allow the end user to utilize an alternative to conventional acids that has the down-hole performance advantages, transportation and storage advantages as well as the health, safety and environmental advantages. Enhancement in short/long term corrosion control is one of the key advantages of the present invention. The reduction in skin corrosiveness, the controlled spending nature, and the high salt tolerance are some other advantages of compositions according to the present invention.

[0063] The compositions according to the present invention can be used directly (ready-to-use) or be diluted with water depending on their use.

[0064] The uses (or applications) of the compositions according to the present invention upon dilution thereof ranging from approximately 1 to 75% dilution, include, but are not limited to: injection/disposal in wells; squeezes and soaks or bullheads; acid fracturing, acid washes or matrix stimulations; fracturing spearheads (breakdowns); pipeline scale treatments, cement breakdowns or perforation cleaning; pH control; and de-scaling applications.

[0065] 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.