HU203383B - Process for stabilizing iron compounds during well treating processes - Google Patents

Abstract

In order to keep Fe ions in soln. as part of well treatment, the following cpds. are added to the treating fluid (all kmol/m3): 5-sulpho-salicylic acid, 0.001-0.04 citric acid and 0.01-0.15 acetic acid and/or their alkali and/or ammonium salts.

Description

The present invention relates to a process for stabilizing iron (IH) and iron (II) ions which can be used in acidification operations to prevent precipitation of iron hydroxide and asphaltenes initiated by iron ions.

It is known that in the acidic stimulation of productive layers, significant amounts of iron can be dissolved in the acid to form fcrrifFe '' or ferroFe '

The pH of the acidic solution used is constantly increasing during contact with the storage rock. The precipitation of iron (III) ions begins at about pH 2, while the iron (II) ions are precipitated in the form of hydroxide at about pH 7. Because the pH of the reacted acid does not rise well above 6, precipitation of iron (II) ions seldom causes problems divestment. It is therefore advisable to use iron stabilizing additives in the treatment fluids.

The primary consideration when selecting stabilizers is that the conditions set by the treatment conditions [temperature, iron (IU) ion content, etc.] are fully met. Given the importance of the problem, there are numerous references in the literature to the composition of stabilizing agents. Thus, SMITH C.F. - CROWE C.W., "Secondary Deposition of Writer Compounds Following Acidizing Treatments" (September 1969, 1121-1129), summarizes the knowledge of secondary iron precipitation during acidification. During their experiments, laboratory studies were carried out on the applicability of various complexing agents during acid coatings. According to the results, citric acid, EDTA and NTA are the most suitable stabilizers above 3000 ppm iron content and above 80 'C

In the USSR, acetic acid is used as an iron salt stabilizer in oil wells, as is evident from Chemical Abstracts Ref 107.42703q. This solution is only applicable up to 70 'C because at higher temperatures the system becomes unstable and precipitation occurs. A further disadvantage of this solution is that acetic acid has to be used in very high quantities, which is not only expensive but also presents a risk of corrosion.

The development of low-cost and high-efficiency stabilization systems has resulted in the recognition of the synergistic effects of complexing agents on one another.

A number of patents also address the use of complexing agents to prevent precipitation of iron hydroxide formed during well stimulation, such as in U.S. Patent No. 3,142,335. U.S. Pat. Such compositions may be prepared by a mixture of citric acid, acetic acid and formic acid or salts thereof in appropriate proportions.

Λ No. 3,150,081 U.S. Pat. This composition is cheaper and more effective than the two components alone.

No. 4,137,972. U.S. Patent No. 5,123,125 discloses the advantageous properties of 5-sulfosalicylic acid in preventing the precipitation of both iron asphaltene and iron hydroxide.

No. 4,167,214. U.S. Pat. The problem with this method, besides the later disadvantages of the prior art methods, is that relatively large amounts of expensive additives can only achieve satisfactory results.

The solutions known so far did not allow the iron to be precipitated for a longer time.

Our aim was to develop a process that allows the iron (III) compounds to be kept in solution during well treatment and stratification operations requiring longer (e.g., 24 hours) well treatment time, thus preventing the storage of iron compounds. especially delayed-action and / or in-situ systems.

Our laboratory tests also confirmed the fact that Ewing B.C., Pabley A.S. and Callaway R.E. (SPE 11795) - that the protection of productive (eg hydrocarbon storage) layers is best ensured by the synergistic action of chelating complexes.

In our experiments, it has been found that when a composition comprising 5-sulfosalicylic acid and / or its alkali metal and / or ammonium salt and citric acid and / or its alkali metal / ammonium salt and acetic acid and / or its alkaline and / or ammonium salt is dissolved in the fluidizing agent, it is capable of holding several iron (III) ions in solution as when the components used are dissolved therein in the same amount in the composition without changing the parameters.

Verification tests were performed as follows:

FeCl ₃ .6H ₂ O was dissolved in 100 ml of 15% hydrochloric acid, and the mixture was stirred until complete dissolution, after the addition of stabilizing agents. The pH change, which is created by the addition of a marble shavings with increasing tendency between the acid mixture and the layer, to pH 3.5, when iron (III) ions are quantitatively precipitated from the fluid in the absence of stabilizing additives. The mixture was warmed to 98 ° C using a high-power light source and visualized for precipitation. The precipitate was analyzed chemically. The procedure is illustrated by the following examples.

Example 1

To the solutions containing 0.0895 km / m ^{3 of} iron (HI) was added a stabilizing additive, which was made from 5-sulfosalicic acid (0.030 km / m ³ ), citric acid (0.0036 km / m ³ ) and acetic acid (0.069 km / m ³ ). we put it together. No precipitation was observed after 24 hours. (Concentration of Fe 2 O: 5000 ppm = 0.0895 km / m ³ , concentration of total complexing agent 0.1020 km / m ^3. )

HU 203 383 Β

Example 2

To the solution used in Example 1 was added an additive containing 0.0714 km / m ³ citric acid and 0.0833 km / m ³ acetic acid. Calcium citrate precipitated immediately from solution (concentration of Fe ^u 5000 5000 ppm = 0.0895 km / m ³ , total complexing concentration 0.11547 kmAn ³ ).

Example 3

The solution described in Example 1 was mixed with a two-component additive containing 0.059 km / m ^{3 of} 5-sulfosalicylic acid and 0.0833 km / m ^{3 of} acetic acid. The precipitation of iron (III) hydroxide started after an hour. (Concentration of Fe ³⁺ : 5000 ppm = 0.0895 km / m ³ , total complexing concentration 0.1423 km / m ³ ).

Example 4

The stabilizing composition of Example 1 was added to the solutions of 0.1343 km / m ³ iron (III) and it was found that the stabilizing effect was still adequate after 14 hours (Fe ³ * concentration: 5000 ppm = 0, 0895 km / m ³ , concentration of total complexing agent 0.1026 km / m ³ ).

Example 5

Concentrated solution is 0.1343 kmol / m ³ iron (iii) 0.0407 kmol / m ^3, 5-sulfo-salicylic acid, 0.0080 kmol / m ³ of citric acid and 0.0634 kmol / m ³ of acetic acid was added. After 24 hours, the material was found to show no precipitation at all. (The concentration of Fc ^3t is 7500 ppm = 0.1433 km / m ³ and the concentration of total complexing agent is 0.1121 km / m ³ ).

Example 6

For comparison, 0.059 km / m ^{3 of} 5-sulfosalicylic acid and 0.0833 km / m ^{3 of} acetic acid were added to the liquid of Example 5. The stabilization time was only 30 minutes. (The concentration of Fe ³⁺ is 7500 ppm = 0.1433 km / m ³ and the total complexing concentration is 0.1423 km / m ³ ).

Example 7

To a solution of 0.179 km / m ^{3 of} iron (III) ion was added a stabilizing mixture of 0.0462 km / m ^{3 of} 5-sulfosalicylic acid, 0.0212 km / m ^{3 of} citric acid and 0.1379 km / m ^{3 of} acetic acid. contained. No precipitation was observed during the 24 hour test period and the solution retained the purple coloration of the iron complex.

(The concentration of Fc ³ * is 10,000 ppm = 0.179 km / m ³ and the total complexing concentration is 0.2053 km / m ³ ).

Example 8

The stabilizer composition described in Example 5 was added to a solution of iron (III) ion (0.179 km / m ³ ) and it was observed that after 12 hours brown iron (hydroxy) hydroxide was precipitated from the solution. (The concentration of Fe ³⁺ is 10,000 ppm = 0.179 km / m ³ and the total complexing concentration is 0.1121 km / m ^3. )

Example 9

As defined in Example 1 iron (in) ion concentration of the solution 0.0900 kmol / m ^3, 5-sulfo-salicylic acid was added. Raising the pH to the described level, above pH = 2, precipitated the iron (III) hydroxide precipitate, which was completed by reaching pH 3.5 and heating the solution.

Example 10

For further examination of the individual components, iron (III) was added to the mixture of the solution of Example 1 in an amount of iron (III) ion in an amount of 0.33333 km / m ^{3 of} acetic acid at pH = 2.5 at a temperature of 98 ° C. Hydroxide precipitate appeared immediately in large quantities At higher pH values, precipitation occurred even at lower temperatures

Example 11

For two-component systems, 0.0240 km / m ^{3 of} citric acid and 0.700 km / m ^{3 of} 5-sulfosalicylic acid were added to the solution of iron (II) in Example 1. No precipitation was observed in the mixture so stabilized (Fe ³⁺ concentration 5000 ppm = 0.0895 km / m ³ , total complexing concentration 0.094 km / m ³ ).

Example 12

0.1433 km / m ³ for a solution containing iron (III) ion. Citric acid and 5-sulfosalicylic acid were added in the same amounts as described in Example 1b. When the pH was raised to 3.5, precipitation of ferric hydroxide as a brown precipitate was observed at room temperature.

The experiments clearly demonstrated that the effect of our inhibitor composition was significantly better than that of the two component products.

Patent Claim Point

Claims (1)

PATIENT PERSONALITY A method for stabilizing iron compounds in a well treatment operation using a complexing compound, characterized in that 5-sulfonic acid, 0.01-0.04 km / m ³ of citric acid and 0-0.0 km / m ^{3 as} stabilizing agents for well treatment solutions is present. Acetic acid in either the free acid and / or in the form of their alkali metal salts and / or ammonium salts is added in an amount of from 0.1 to 0.15 km / m ³ .