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 an alcohol or derivative thereof optionally, it may further comprise a phosphonic acid derivative.

Claims

1-28. (canceled)

29. 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; optionally, a phosphonic acid derivative; and an alcohol or derivative thereof.

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

31. The synthetic acid composition according to claim 1, wherein the urea and hydrogen chloride are in a molar ratio of not less than 0.8:1.

32. The synthetic acid composition according to claim 1, wherein the phosphonic acid derivative is aminoalkylphosphonic salt.

33. The synthetic acid composition according to claim 1, wherein the phosphonic acid derivative is amino tris methylene phosphonic acid.

34. The synthetic acid composition according to claim 1, wherein the alcohol or derivative thereof is an alkynyl alcohol or derivative thereof.

35. The synthetic acid composition according to claim 1, wherein the alcohol or derivative thereof is an alkynyl alcohol or derivative thereof is propargyl alcohol or a derivative thereof.

36. The synthetic acid composition according to claim 1, wherein the phosphonic acid derivative is present in a concentration ranging from 0.25 to 1.0% w/w.

37. The synthetic acid composition according to claim 1, wherein the phosphonic acid derivative is present in a concentration of 0.5% w/w.

38. The synthetic acid composition according to claim 1, wherein the alcohol is an alkynyl alcohol or derivative thereof present in a concentration ranging from 0.01 to 0.25% w/w.

39. The synthetic acid composition according to claim 1, wherein the alcohol is an alkynyl alcohol or derivative thereof present in a concentration of 0.1% w/w.

40. 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 0.1:1; optionally, a phosphonic acid derivative; an alcohol or derivative thereof; 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 and 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

[0046] It will be appreciated that, numerous specific details have provided for a thorough understanding of the exemplary embodiments described herein. Furthermore, this description is not to be considered so that it may limit the scope of the embodiments described herein in any way, but rather as merely describing the implementation of the various embodiments described herein.

[0047] 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.sup.− 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.

[0048] 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.sup.− 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.

[0049] Alcohols and derivatives thereof, such as alkyne alcohols and derivatives and preferably propargyl alcohol and derivatives thereof can be used as corrosion inhibitors. Propargyl alcohol itself is traditionally used as a corrosion inhibitor which works extremely well at low concentrations. It is a toxic/flammable chemical to handle as a concentrate, so care must be taken during handling the concentrate. In the composition according to the present invention, the toxic effect does not negatively impact the safety of the composition.

[0050] 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.

[0051] Amino tris (methylenephosphonic acid) (ATMP) and its sodium salts are typically used in water treatment operations as scale inhibitors. They also find use as detergents and in cleaning applications, in paper, textile and photographic industries and in off-shore oil applications. Pure ATMP presents itself as a solid but it is generally obtained through process steps leading to a solution ranging from being colourless to having a pale yellow colour. ATMP acid and some of its sodium salts may cause corrosion to metals and may cause serious eye irritation to a varying degree dependent upon the pH/degree of neutralization.

[0052] 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 order to prevent the formation of calcium carbonate scale.

[0053] According to an aspect of the invention, there is provided a synthetic acid composition comprising: [0054] 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 1:1; [0055] an alcohol or derivatives thereof, preferably alkynyl alcohol or derivatives thereof, more preferably propargyl alcohol or a derivative of; and [0056] optionally, a phosphonic acid or derivatives, preferably alkylphosphonic acid or derivatives thereof and more preferably amino tris methylene phosphonic acid and derivatives thereof.

EXAMPLE 1

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

[0057] 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. The propargyl alcohol is then added. Circulation is maintained until all products have been solubilized.

[0058] 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 60.90%  7732-18-5 Urea Hydrochloride 39.0% 506-89-8 Propargyl Alcohol 0.10% 107-19-7

[0059] 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.

[0060] 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 LD50 was determined to be greater than 2000 mg/kg.

[0061] With respect to the corrosion impact of the composition on typical oilfield grade steel, it was established that it was clearly below the acceptable corrosion limits set by industry. This is true for the compositions even when exposed to temperatures exceeding 100° C.

Corrosion Testing

[0062] 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.

[0063] Samples of J55 grade steel were exposed to various synthetic acid solutions for 6 hours at 90° C. temperatures. All of the tested compositions contained HCl and urea in a 1:1.05 ratio at a 100% concentration.

TABLE-US-00002 TABLE 2 Corrosion testing comparison between HCl-Urea and the composition of Example 1 of the present invention Initial Final Loss Surface Run Inhibitor wt. wt. wt. area Density time (%) (g) (g) (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 + 37.514 37.099 0.415 28.922 7.86 6 1049.34 26.653 0.030 propargyl @ 0.1%

[0064] 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.

[0065] The compositions according to the present invention can be used directly (ready-to-use) or be diluted with water depending on their use.

[0066] 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.

[0067] 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.