SU1505959A1 - Composition of fluid for perforating production formations - Google Patents

Abstract

The invention relates to the oil and gas industry, in particular, to perforation of the formation. The goal is to increase the dissolving capacity of the composition with respect to clay minerals while maintaining its high density. The composition contains the following ingredients with their ratio, wt.%: Hydrochloric acid 2.5-15.0

hydrofluoric acid 0.5-6.0

aluminum chloride 0.5-6.0

calcium chloride 5.0-30.0, water the rest. The mechanism of action of these substances is based on the ability of aluminum ions to bind fluorine ions into complex compounds of varying composition from [ALF] ⁺² to [ALF ₆ ] ^-3 . Complexes are easily formed by simply mixing the starting components. Aluminum fluoride complexes, formed directly in a sulfuric acid solution of calcium chloride, prevent the formation of insoluble calcium fluoride and are sources of free fluoride ions. The concentration of the latter is maintained at a constant low level according to the dissociation of the complex, which increases the dissolving capacity of the composition. 2 tab.

Description

31505

easily formed by simply mixing the starting components,

Aluminum fluoride complexes, formed directly in a hydrochloric acid solution of calcium chloride, prevent the formation of insoluble calcium fluoride, and also are sources of free fluoride ions, the concentration of which is maintained at a constant low level according to the dissociation process of the complex, which leads to an increase in dissolving composition abilities.

The perforation fluid is obtained in the following manner. Mix the calculated amount of hydrochloric, hydrofluoric acids and water, add the calculated amount of aluminum chloride, mix until complete dissolution, then add calcium chloride, adjusting the density of the solution to the desired value. For example, to prepare 1 m of a composition with a density of 1175 kg / m, containing hydrochloric acid, 1% of ferric acid, 1% aluminum chloride, 15% calcium chloride, 75.5% water, 0.325 m of 24% should be taken. hydrochloric acid, add 0.026 m of D0% hydrofluoric acid and 0.422 m of water, mix, pour 11.75 kg of dry aluminum chloride, mix until the salt is completely dissolved, then add 347.9 kg of calcium chloride cojiH .

Other formulations are prepared in a similar manner.

The effectiveness of the compositions is assessed in the laboratory using the weight method by decreasing the weight of 1 g of bentonite after treatment with its compositions (25 ml).

In tab. 1 shows the results of determining the solubility of bentonite with compositions at 60 ° C and a duration of 6 hours.

From tab. 1, it follows that the positive properties of the composition are manifested at all the indicated contents of the ingredients.

/ The optimal ratio of hydrofluoric acid additives and aluminum chloride, which prevents the formation of calcium fluoride, is determined experimentally with an average content of components.

In tab. Figure 2 shows the results of determining the amount of calcium fluoride precipitate that is formed in the acid composition when the ingredients are mixed.

From Table 2 it can be seen that adding to the known composition of hydrofluoric acid without aluminum chloride leads to the fact that it interacts with calcium chloride and forms an insoluble precipitate of calcium fluoride.

The addition of aluminum chloride leads to a decrease in the amount of sediment, with a 1: 1 mass ratio of hydrofluoric acid and aluminum chloride, practically no precipitate is formed. Such a ratio is assumed to be optimal.

The lower concentration limit of the content of hydrochloric and hydrofluoric acids is due to the insufficient dissolving ability of the composition. The upper limit of the hydrochloric acid content is limited by the high corrosivity of the composition. The upper limit of the content of hydrofluoric acid, and therefore of aluminum chloride, is determined by the properties of the composition: when the content of aluminum chloride is 0.25-1%, the addition of calcium chloride

does not cause complications, with 2-6% aluminum chloride after the addition. Calcium chloride forms a gel, which is easily destroyed when heated, with a higher content of aluminum chloride, a stable step is formed, which makes the composition not workable. The lower limit of the content of calcium chloride is due to the insufficient density of the composition, the upper limit to the limited solubility of calcium chloride.

The order of the technological operations during the processing of the near-wellbore zone of the reservoir during its secondary opening by perforation does not change as compared with the known one.

The application of the proposed composition makes it possible to combine secondary perforation of the formation with perforation and acid treatment into a single technological process and, therefore, exclude measures to restore the permeability of the bottomhole zone, usually carried out after perforation.

The use of the proposed composition as a perforation fluid improves the efficiency of work in conditions of clayed collectors. The expected increase in oil production will be -6 tons / day.

Claims (1)

Claim The composition of the perforation fluid of productive formations, including hydrochloric acid, calcium chloride and water, characterized in that, in order to increase its dissolving ability with respect to clay minerals while maintaining high density, it additionally contains hydrofluoric acid and aluminum chloride at the following ratio Dientov, May 2: Hydrochloric acid 2.5 - 15.0 Hydrofluoric acid 0.5 - 6.0 Aluminum chloride 0.5 - 6.0 Calcium chloride 5 - 30 Water Rest Table 1 Component Content, May 2 Density, kg / m * The amount of dissolved bentonite, May .2 Hydrochloric acid Hydrofluoric acid Aluminum chloride Calcium chloride Water 5 - - fifteen 80.0 1146 11.0 5 - - thirty 65.0 1305 10.9 7.5 - - fifteen 77.5 1,160 11.6 fifteen - - 5 80.0 1 109 11,4 fifteen - - fifteen 70.0 1204 11.1 1,5 0.25 0.25 5 96.0 1045 12.1 2,5 0.5 0.5 thirty 66.5 1296 28.6 5,0 1,0 1,0 fifteen 78.0 1160 35.0 7.5 1,0 1,0 fifteen 75.5 1175 36.3 15.0 1,0 1,0 fifteen 68.0 1220 36.1 15.0 6.0 6.0 5 68.0 1,196 31,0 table 2 Component Content, May 2 The mass of sediment, g Hydrochloric acid Hydrofluoric acid Aluminum chloride Calcium chloride Water 10 3 0 fifteen 72.0 1,334 10 3 0.25 fifteen 71.75 0.680 10 3 0.5 fifteen 71.5 0.361 10 3 1 fifteen 71.0 0.257 10 3 2 fifteen 70.0 0.158 10 3 3 fifteen 69.0 0.002 10 3 4 fifteen 68.0 0,027 10 3 5 fifteen 67.0 0,020 10 3 6 fifteen 66.0 0.010