BRPI0605005B1 - COMPOSITION AND PROCESS FOR DISSOLUTION OF ALKALINE SULPTATE INCRUSTATIONS IN SURFACE, SUB-SURFACE AND PETROLEUM FORMATION EQUIPMENT - Google Patents

Abstract

composition and process for the dissolution of alkaline sulfate scale in surface, subsurface and oil formation equipment. and a composition of alkaline sulfate encrustations on surface and oil formation, water and a 1: 1 to 1: 2.5 molar ratio of a carboxylic acid or its potassium and urea salt at a pH between 8 and 14, composition being used at temperatures between 50 and 100 ° C for a period of time necessary to effect scale dissolution. Preferred polyaminocarboxylic acids are dtpa (diethylene triamino pentaacetic acid) or its potassium salt dtpa (ethylene diamino tetraacetic acid). Also described is the process for dissolving alkaline sulfate scale using the composition of the invention.

Description

(54) Title: COMPOSITION AND PROCESS FOR THE DISSOLUTION OF ALKALINE SULPHATES INCRUSTATIONS IN SURFACE, SUB-SURFACE EQUIPMENT AND IN PETROLEUM FORMATION (51) Int.CI .: C09K 8/528; C09K 8/72; C09K 8/52; E21B 43/28 (73) Holder (s): PETROLEO BRASILEIRO S.A. - PETROBRAS (72) Inventor (s): MARIA CARMEN MOREIRA BEZERRA; FRANCISCA FERREIRA DO ROSÁRIO; ROSILENE TROYACK GOULART • · · · · · · · · · · ·

COMPOSITION AND PROCESS FOR THE DISSOLUTION OF ALKALINE SULPHATE INCRUSTATIONS IN ^- ~ SURFACE, SUB-SURFACE AND PETROLEUM FORMATION EQUIPMENT

FIELD OF THE INVENTION

The present invention belongs to the field of chemical processes and their respective compositions for the dissolution of incrustations of alkaline sulphates that are formed in the oil production process, as a result of the chemical incompatibility between sea water, containing the same concentration of sulphate, injected into the oil formation for maintaining pressure, and the formation water or conate water or aquifer water containing barium, strontium and / or calcium.

BACKGROUND OF THE INVENTION

Incrustations of barium, strontium and calcium sulfate are formed in the oil production process as a result of the chemical incompatibility between sea water, containing a high concentration of sulfate, injected into the oil formation to maintain pressure in the formation water or conata water or aquifer water containing barium, strontium and or calcium. In addition to the incrustations resulting from the mixture of formation waters and sea water, sulfate-based incrustations may also form in the condensate and gas production process as a consequence of the concentration of these salts in the aqueous phase.

These incrustations can cause obstructions in valves, equipment, columns and production lines, sand retaining screens, embossed pack and in the formation close to the producing wells and the ______25 injectors in the case of re-injection of produced water. The formation of these incrustations in the equipment compromises its operation, causing a stop for cleaning them.

Inlays prevent proper heat transfer, interfere with fluid flow, facilitate corrosive processes, and harbor bacteria.

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Inlays can occur in different places, including the production column, cannons from the well, in the area close to the well,

------------ lines, gauges, valves _e_em_o_utto_s production equipment such as engraved pack and sand retaining screens in horizontal wells.

The chemical removal of barium and strontium sulfate incrustations is considered a difficult and often impossible task due to their low solubility in the usual solvents requiring the application of more aggressive methods such as those based on mechanical removal.

US patent 5,049,297 teaches that barium sulphate encrustations are removed from pipelines in oil installations with a composition comprising an aqueous alkaline solution with a pH between 8 and 14, preferably 11 to 13, of a polyamine polycarboxylic acid, preferably EDTA or DTPA and a catalyst or synergist that comprises thiosulfate or nitriloacetate anions.

US patent 5,146,988 teaches a method for removing calcium sulfate scale from a well that comprises mixing carbon dioxide and water in a location inside the well to form an acid solution containing a balanced mixture of carbonic acid, and bicarbonate and carbonate ions that must convert the calcium sulfate scale into calcium carbonate scale and subsequent dissolution in situ of the calcium carbonate scale in the acid solution that flows in the formation around the well.

US patent 5,200,117 teaches that alkaline earth metal fouling, especially barium sulphate, is removed from pipelines in oil and other pipelines with a fouling remover that comprises an aqueous alkaline solution with a pH between 8 to 14, preferably 11 to 13, of a polyamine polycarboxylic acid, preferably EDTA or DTPA and a catalyst or synergist comprising a monocarboxylic acid, preferably a substituted acetic acid such as mercaptoacetic acid, hydroxyacetic

3/13 • · ··· • · · · · ······. · · · · ······ • · · · or aminoacetic or an aromatic acid such as saicylic acid.

US patent 5,282,995 teaches a method and composition for

------ remove deposits-of scale- from barium sulfate and strontium. The composition comprises an aqueous solution with a pH between 8 and 14, an EDTA or DTPA chelator, and a catalyst or synergistic compound. Preferred chelators are diethylene triamine pentaacetic acid (DTPA) or ethylene diamine tetraacetic acid (EDTA) or the alkaline salts thereof. Anions of organic and inorganic acids constitute the catalyst. Useful catalysts include fluoride, oxalate, persulfate, dithionate, hypochlorite and formate anions. The catalyst concentration is between 0.01 M to 0.5 M. The aqueous solution containing the composition can be directed into a well to remove barium sulfate scale that is embedded in the tubular equipment and other passages. Before being directed to the well, the composition is heated to a temperature of about 25 ° C to about 100 ° C. Once inside the pipes and passages that require treatment, the composition is kept there for about ten minutes until about 7 hours. After remaining in contact with the equipment for the desired time, the composition containing the dissolved encrustation is produced for the surface. This procedure can be repeated as often as necessary to remove scale from the equipment.

SUMMARY OF THE INVENTION

Broadly speaking, the invention deals with a process and associated composition, for the dissolution of alkaline sulphate incrustations in surface, sub-surface and oil formation equipment, the process comprising contacting inside the surface equipment, sub -surface or in oil formation, at a temperature between 50 ° C and 100 ° C, for a period of time necessary for the dissolution of the alkaline sulphate scale, a composition comprising an aqueous solution at a pH between 8 and 14, preferably between

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4/13 • ♦ · • ♦ ·· • · · · · · · · · · · · · · · · · · · · «• * and 13, of diethyl acid triamine pentaacetic acid (DTPA) or its leaves of potassium and urea as a catalyst, in the molar ratio of DTPA. urea from 1: 1 to 1: 2.50, dissolving in the presence of urea being faster than only in the presence of DTPA.

In this way, the invention provides a process for the dissolution of alkali metal sulphate incrustations based on an acid such as DTPA and a urea catalyst, where the urea decomposition releases carbon dioxide which accelerates the decomposition of the fouling material.

The invention also provides a composition based on DTPA and urea which, placed in contact with the encrustation, promotes its dissolution faster than it would without the presence of urea. BRIEF DESCRIPTION OF THE DRAWINGS

The attached FIGURE 1 is a graph illustrating the concentration of sulfates obtained according to the state of the art using an aqueous solution containing 0.5M DTPA. Curve 1 shows the effect of the DTPA solution on a clean oil scale while curve 2 shows the effect of the DTPA solution on a scale from which the oil that covered it was not removed.

The attached FIGURE 2 is a graph illustrating the percentage of decomposition of sulfates for a composition of the invention that uses 0.5M DTPA and 0.5M urea (molar ratio DTPA: urea 1: 1). Curve 1 shows the effect of said composition used on a clean oil scale while curve 2 shows the effect of said composition used on a scale where the oil that covered it was not removed. 25 The attached FIGURE 3 is a graph illustrating the percentage of ___ sulfate decomposition for a composition of the invention that uses

0.5M DTPA and 1.0M urea (molar ratio DTPA: urea 1: 2). Curve 1 shows the effect of said composition used on a clean oil encrustation while curve 2 shows the effect of said composition used on an encrustation from which the oil that covered it was not removed.

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DETAILED DESCRIPTION OF THE INVENTION

In one aspect, the invention deals with a composition in the form of an "aqueous solution at a pH between 8 and 14, said solution containing a polyamine carboxylic acid such as DTPA and urea in molar ratio between 1: 1 to 5 1: 2.5 of acid for urea, the solution being used at temperatures between and 100 ° C for the dissolution of alkali sulphate incrustations in surface, sub-surface and oil formation equipment.

In another aspect, the present invention deals with a process for the dissolution of alkaline sulphate incrustations in surface, sub-surface and petroleum formation equipment, the process comprising bringing into contact inside the surface, sub-surface or in oil formation, the temperature between 50 ° C and 100 ° C, for a period of time necessary for the dissolution of the alkaline sulfate encrustation, the composition comprising an aqueous solution at a pH between 8 and 14, preferably between 11 and 13 , of a polyamine carboxylic acid such as diethylene triamine pentaacetic acid (DTPA) or its potassium salt and urea as a catalyst, in the molar ratio of DTPA: urea from 1: 1 to 1: 2.5, dissolution in the presence of urea being more faster than only in the presence of DTPA.

The water used in making the polyamine carboxylic acid and urea solution is an industrial water that has a low concentration of calcium, barium and strontium and can have up to 20 mg / L of calcium and values below 0.5 mg / L of barium and strontium. .

Polyamino carboxylic acid or its preferred potassium salt in the pre-treated diet is diethylene triamine pentaacetic acid (DTPA). The sodium salt can also be used. Also useful, it is onacid ^- diafilino tetraacetic (EDTA). Polyamino carboxylic acid or its potassium salt is associated with a catalyst or synergistic compound to facilitate the dissolution of the alkaline sulfate encrustation. Alternatively, the potassium salt of polyamine carboxylic acid is obtained by synthesis.

6/13 «· ··» p · · • · * · • · · · * • * · ·· · *. «« ···· • ··· »» · ··· · · * · »· · ··· * • · · · *« «· ······« · · · · · ♦ · ···· * • · · *

The urea used in the composition is commercial grade, soluble in water, with a melting point of 132.7 ° C. The product has the chemical formula 1MH ₂ CONH ₂ , and can be <x> considered as an amide of the carbonic acid (NH ₂ COOH) or a carbonic acid diamide (HOCOOH).

Both in the aqueous solution of DTPA alone (state of the art solution, used as a control) and in the compositions of the invention containing DTPA and urea, the components are dissolved in water. /

Alkaline sulphates that are liable to be dissolved by contacting the composition of the invention at temperatures between

50 ° C and 100 ° C are barium, strontium and / or calcium sulphates.

A typical sulfate dissolution temperature is between 80 ° C and

90 ° C.

The pH between 8 and 14, preferably between 11 and 13, is obtained by adding KOH to the medium.

The solution of polyamino carboxylic acid and urea is prepared by dissolving the proportion of urea in water, with stirring, and adding, always with stirring, the desired proportion of the potassium salt of ethylene triamine carboxylic acid (DTPA). The contact time of the aqueous polyamine carboxylic acid solution with the scale to be treated is between 2 and 28 hours. In general, DTPA is found to be more efficient at dissolving barium sulfate than EDTA.

The treatment of the sample to be solubilized with the descaling solution of the invention is carried out according to the procedure described below. For comparison purposes, the same procedure is performed _ for a sample treated only with DTPA.

The sample of residue or encrustation is collected from the medium ^- ~ rnãisT homogeneous as possible.

The sample is subjected to dissolution in the presence of DTPA alone or in the presence of the composition of the invention in two ways: clean of oil or without being cleaned.

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In order to carry out the fouling dissolution test with the clean residue sample, cleaning is carried out with the aid of an aromatic organic solvent -like toluene-or _xiiene_ at room temperature until the sample is oil-free.

When this condition is reached, the sample is oven dried at 6065 ° C for 4-5 hours.

The dissolution test for both the clean oil sample and the oil coated sample comprises the following steps:

a) homogenize the sample mass by maceration;

b) for each contact time of the sample with the descaling solution, weigh the sample so homogenized in plastic bottles, and add to the said bottles the descaling solution preheated to the test temperature;

c) stir the sample and descaling solution mixture and take it to an oven at the temperature determined for the test;

d) after the determined reaction time for each bottle, it is removed from the oven, shaken and a 5 ml aliquot is collected with the aid of a syringe;

e) filter the syringe contents over a 0.45 micron millex filter, 20 collecting the filtrate in a plastic tube;

f) when the filtered solution is at room temperature, remove the known aliquot with an automatic pipette, transferring it to another plastic bottle, diluting with Mille-Q water. and

g) perform the determination of the metal in spectrophotometry by ICP-25- -OES- (plasma) .______ _________

Without being linked to any particular theory, the Applicant believes that the greater speed of dissolution of the barium sulfate scale in the presence of the composition described and claimed here can be attributed to the greater surface contact promoted by the release of carbon dioxide resulting from the decomposition. of urea.

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The invention will be illustrated below by Examples and corresponding attached Figures, which should not be considered limiting.

--------- EXAMPLE 1_____ ··· ·· • · • · · · · · · · · »·· • · τ

This is a comparative example, in which the sample is treated 5 according to the state of the art procedures, that is, an aqueous solution of 0.5M DTPA. For comparison purposes, a clean sample of oil was used and another one treated under the same conditions, other than (impa.

The results obtained are tabulated in Table 1A below for the 10 clean sample and illustrated in Figure 1 curve 1.

TABLE1A

Solution descaler Contact time (hours) Cone. BaSO ₄ (mg / L) 0.5 M DTPA 2 2778.6 4 2853.3 6 2854.8 8 2882.2 12 3405.7 21 4129.6 24 5100

And the results for the sample without being cleaned are tabulated in Table 1B below and illustrated in Figure 1 curve 2.

TABLE 1B

Solution descaler Contact time (hours) ConcrBaSOj (mg / L ·) - 0.5 M DTPA 2 2547.4 4 2824.5 6 2826.8

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It can be seen from the data in Tables 1A and 1B and Figure 1 that the isolated DTP A used as a solution to dissolve the scale requires about 21 hours of contact to dissolve about 4300 mg / L of barium sulfate present in the sample. .

EXAMPLE 2

This Example illustrates the sample treated according to the procedures of the invention, that is, an aqueous composition of DTPA and urea at 0.5M: 0.5M (molar ratio 1: 1).

For comparison purposes, a clean sample of oil 10 was used and another one treated under the same conditions, without being cleaned.

The results obtained are tabulated in Table 2A below for the clean sample and illustrated in Figure 2 curve.

TABLE 2A

Solution fouling Contact time (hours) Cone. BaSO ₄ (mg / L) 0.5 M DTPA + 0.5 M Urea 2 3823.7 4 4248.6 6 4461 8 4546 _____ 42 ---- 4588.5 21 5310.7 24 5395.7

And the results for the sample other than timpa are tabulated in the

Table 2B below and illustrated in Figure 2 curve 2.

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TABLE 2B

Descaling solution

0.5 M DTPA + 0.5 M Urea

Contact time (hours) Cone. BaSO ₄ (mg / L) 2 4248.6 4 4376 6 4418.5 8 4439.8 12 4546 21 5098.3 24 5140.8

It can be seen from the data in Tables 2A and 2B and Figure 2 that in the presence of urea the dissolution capacity of the sample containing encrustation reaches levels around 4300 mg / L of barium sulfate after a much shorter time than only in presence of DTPA, _this_time being around 6 to 8 hours of contact of the solution with the sample.

EXAMPLE 3

This Example illustrates the sample treated according to another embodiment of the procedures of the invention, that is, an aqueous composition of DTPA and 0.5M urea: 1.0M (1: 2 molar ratio). For comparison purposes, a clean sample of oil was used and another one treated under the same conditions, without being cleaned.

The results obtained are tabulated in Table 3A below for the clean sample and illustrated in Figure 3 curve 1. ________________

TABLE 3A

Solution descaler Contact time (hours) Cone. BaSO ₄ (mg / L) 0.5 M + DTPA 2 3696.3

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Urea 1 Μ

4 5098.3 6 5523.2 8 5608.1 12 5820.6 21 5863 24 5948

And the results for the sample other than I mpa are tabulated in Table 3B below and illustrated in Figure 3 curve 2.

TABLE 3B

Solution descaler Contact time (hours) Cone. BaSO ₄ (mg / L) 0.5 M DTPA + 1 M Urea 2 3271.4 4 4673.4 6 4885.9 8 5098.3 12 5268.2

It can be seen from the data in Tables 3A and 3B and Figure 3 that in the presence of DTPA and urea in a molar ratio of 1: 2, the dissolution capacity of the sample containing scale reaches levels around 4300 mg / L of barium sulfate after a much shorter time than just in the presence of DTPA, or in the presence of DPTA: urea in a 1: 1 molar ratio, this time being around 3 hours of contact

1Õ ~ “dOlution with the sample.- - - __________________

It can be seen from the Examples above that the concentration of DTPA employed ensures relatively low-cost scale dissolving operations while maintaining the kinetics of the reaction of DTPA with alkaline salts at appropriate levels.

Much lower concentrations can reduce the efficiency of the process, • ·

12/13 · «· ··· · · · ···· · · · · * · · ······ ···« ··········· as very high concentrations, in addition of influencing the cost, they can alter the kinetics, impairing the desired dissolution of the - 4ncru $ tation. - _ _______

Thus, it should be made clear to experts that, although the invention has been described for certain molar concentrations of polyamine carboxylic acid (DTPA) and urea, it is evident to experts that other concentrations, close to those that have been employed, are also understood in the scope of the invention as long as the 1: 1 to 1: 2.5 molar ratios DTPA: urea are maintained.

FIELD EXAMPLE

This Example is a case that illustrates the excellence of the invention when used in the field.

Thus, a heat exchanger on a platform had such an amount of encrustation that the crane's capacity was not sufficient to remove it and perform cleaning. All the

- procedures known in the art have been used previously in order to dissolve the scale of barium sulfate, calcium sulfate, strontium sulfate and iron oxide.

These alkaline sulfates and iron oxide 20 were then removed using the composition of the invention in the DTPA: urea ratio

1: 2.

The process data are: 13.66 tons of fouling, with the following proportions of dissolved salts: 44, 5 g / L barium sulfate,

38.9 g / L of calcium sulfate, and 87.4 g / L of strontium sulfate. The total dissolved mass was 170.8 g / L.

The total volume of descaling solution used, at a temperature of around 80-90 ° C, was 80 m ³ and the contact time of the solution with the encrustation was about 6 hours.

Therefore, it is demonstrated that incrustations containing alkaline salts 30 such as barium sulfate are capable of dissolving in the presence of

13/13 ·· «aqueous composition containing DTPA: urea in molar ratio from 1: 1 to 1: 2.5, the time required for the dissolution of alkaline salts being significantly shorter in the presence of the compositions of the invention than in the presence of state-of-the-art aqueous solutions containing only DTPA.

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Claims (17)

1. Composition for the dissolution of alkaline suffate incrustations in surface, sub-surface and petroleum formation equipment, characterized by comprising water at a pH between 8 and 14 and, dissolved in it, a polyamino carboxylic acid or its potassium salt and urea as a catalyst, in a molar ratio between 1: 1 and 1: 2.5 of polyamine carboxylic acid: urea. 2. Composition according to claim 1, characterized by being applied to incrustations in valves, miscellaneous equipment, columns and production lines, sand retaining screens, embossed pack and in the formation close to the producing wells and the injection wells in the case of reinjection of produced water. Composition according to claim 1, characterized in that the alkaline salts comprise barium sulphate, calcium sulphate and / or strontium sulphate. Composition according to claim 1, characterized in that the polyamino carboxylic acid is diethylene triamine pentaacetic acid (DTPA). Composition according to claim 1, characterized in that the polyamino carboxylic acid is ethylene diamino tetracetic acid (EDTA). Composition according to claim 1, characterized in that the pH of said aqueous solution is between 11 and 13. Composition according to claim 1, characterized in that the molar ratio of DTPA: urea is 1.2. Composition according to claim 1, characterized in that it is applied over an oil-covered scale sample. Composition according to claim 1, characterized in that it is applied to a fouling sample from which the oil has been removed by washing with aromatic solvent. Composition according to Claim 1, characterized in that it is applied to an encrustation sample at temperatures between 50 and 100 ° C. Composition according to Claim 10, characterized in that it is applied to an encrustation sample at temperatures between 80 and 90 ° C. 12. Composition according to claim 1, characterized in that it dissolves the incrustations in contact times shorter than the times 2/2 contact required for similar dissolution levels when state of the art solutions are used. 13. Process for the dissolution of alkaline sulphate incrustations in surface, sub-surface equipment and in oil formation with the aid of the composition according to claim 1, characterized by being carried out by putting in contact inside the surface equipment, sub-surface surface or in oil formation, the temperature between 50 ° C and 100 ° C. 14. Process according to claim 13, characterized in that it is applied to incrustations in valves, miscellaneous equipment, columns and production lines, sand retaining screens, embossed pack and in the formation close to producing wells and injection wells in the case of reinjection of produced water. Process according to claim 13, characterized in that the alkaline salts comprise barium sulphate, calcium sulphate and / or strontium sulphate. Process according to claim 13, characterized in that the temperature during contact of said composition with the encrustation is between 80 and 90 ° C. Process according to claim 13, characterized in that the period of contact of said composition with the encrustation is between 2 and 28 hours. 1/3 ·· · • · · · · · · ♦ · · · · · · · · · · · · · · · · · · · · · · · · ··· • · · 2/3 * · ·· • · · • · · · · · · · * · • * ·· · · ··· ··· ♦ · ·; ϊ «• · ·····« ·· «« · · »· · ·» ········· • · · · · · Time (hours) 3/3 ♦ · · • · • * • · « • ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Time (hours)