Foamable composition for well development

 

(57) Abstract:

The invention relates to the oil and gas industry, in particular foaming compositions, and is intended for the call flow of the liquid from the reservoir during the development wells. Increasing the efficiency of exploration wells at the expense of gas saturation of the solution and the formation of foam on the bottom of the wells from thermal energy of the reservoir and reduce corrosion of equipment is achieved by the fact that the proposed foamable composition contains the following components: urea 3,5 - 8,8, wt.%; nitrite, an alkaline or alkaline earth metal 8,1 - a 20.2 wt.%; acetic acid 16,4 - 41,0 wt.%, the hydroxide of an alkali metal 8.6 out of 21.6 wt. % of surfactant of 0.5 - 1.0 wt.%; water - the rest. The hydroxide of the alkali metal forms with acetic acid-acetate buffer solution and allows to obtain solutions with a pH equal to from 4.0 to 6.0 and variable speed of gas saturation. Regulation of the pH of the medium helps reduce corrosion of equipment, at a pH of 4.0 is not formed corrosive product (nitrogen dioxide), at a pH of buffer solution from 4.0 to 6.0 possible thermal catalysis of gas saturation of the solution and foam formation in the temperature range from 40 to 100C. 4 Il., 5 table.

From what aceno for call flow of fluid from the formation with the well completion.

Known composition for stimulation of the reservoir fluid containing urea, aluminum sulfate, surfactant and water.

Gasanalysis solution is carried out by thermal hydrolysis of urea according to the scheme:

CO(NH2)2+H2O __ CO2+2NH3(I)

The disadvantages of this structure are:

low gasanalysis ability because of the solubility products of a chemical reaction (carbon dioxide and ammonia) in the water, especially at high pressures;

corrosion of oilfield equipment, especially from non-ferrous metals and their alloys in the presence of ammonia;

limited thermal conditions (temperature in the borehole must be above 105aboutC).

The closest technical solution to offer foamable composition is self-generating foam system containing urea, surfactant, nitrites of alkali and alkaline earth metals, acid, methenamine and water [1]

As gas agent in this composition are carbon dioxide and gaseous nitrogen, which is formed due to the interaction of initial components

NaNO2+H+Na+the rod is then, that:

in the interaction of acids and salts of nitrite at pH 4,0 highlighted brown gas, which causes corrosion of the equipment. When the temperature of the composition above the 20aboutWith nitrous acid decomposes with evolution dioxide and nitric oxide.

Nitrogen dioxide (brown gas) when interacting with water forms nitric acid according to the following scheme:

2HNO2N2O3+H2O (4)

N2O3__ NO2+NO t 20C (5)

3NO2+H2O 2HNO2+NO (6) and in the presence of an oxidant and free oxygen:

4NO2+2H2O+O24HNO3(7)

methenamine decomposes with evolution of formaldehyde and ammonia in an acid environment. The decomposition products of urotropine and the acid are corrosive agents;

foaming occurs at any positive temperature immediately after mixing the starting components and has an explosive character, therefore there are difficulties in the implementation process during the development of the well.

The aim of the invention is to increase the efficiency of exploration wells at the expense of gas saturation of the solution and foam at the bottom of the wells from thermal energy, p is Asa urea, nitrite, an alkaline or alkaline-earth metal, acetic acid, surfactant and water, additionally contains an alkali metal hydroxide in the following ratios, wt.

Urea 3,5-8,8

Nitrite, an alkaline or alkaline-

land metal 8,1-20,2

Acetic acid 16,4-41,0

The alkaline hydroxide

metal 8,6-21,6

SURFACTANT OF 0.5-1.0

Water the Rest

Gasanalysis solution and the formation of foam on the bottom of the borehole occurs spontaneously due to thermal energy of the reservoir through a number of intermediate reactions. For example, the composition further comprises sodium hydroxide, then the overall chemical equation for the interaction of initial components is as follows:

aCH3COOH+NaOH+(NH2)2CO+(a+b)NaNO2__

__ aCH3COONa+(a-b)N2+ CO2+H2O

(8)

where a and b are the stoichiometric coefficients in the chemical equation.

The stoichiometric coefficients are calculated from the graphs of the dependence of the rate of outgassing from the pH of the medium and temperature (Fig.1);

the pH of the medium and the weight ratio of acetic acid to sodium hydroxide (Fig. 3).

Some values of the stoichiometric coefficients in the chemical urval forms with acetic acid-acetate buffer solution (pH Adjuster), and also influences the rate of gas saturation of the solution. At low pH values, the environment, the composition of the more intense forms a foam.

Regulation of the pH of the medium helps reduce corrosion of equipment, at pH>4,0 corrosive nitrogen dioxide (brown gas) is not allocated.

Reducing the corrosiveness of the proposed structure in comparison with the known confirmed by experimental data, are presented in table. 2.

Acetate buffer solution is a mixture of solutions of weak acids, salts of this acid and strong bases.

CH3COOH+NaOH CH3COONa+H2O (9)

The concentration of hydrogen ions (pH) in the solution of acetic acid depends on its concentration and the degree of dissociation.

The degree of dissociation of weak acetic acid is reduced if you add a salt of this acid. The higher the salt concentration, the lower is the concentration of hydrogen ions. Thus, by changing the concentration of acetic acid and the amount of sodium acetate (alkali metal hydroxide), it is possible to obtain solutions with different pH.

The mechanism of action of the hydroxide of an alkali metal and its impact on the changing pH of the composition is explained by the following about the major water molecules. The loss of hydrogen ions disturb the equilibrium of dissociation of acetic acid and will shift it to the right, towards the formation of new hydrogen ions in a chemical reaction (9). However, this increases the salt concentration and the degree of dissociation of acetic acid is slightly reduced. But all these changes are minor and after equilibrium pH will change slightly. So, when added to 1 l of acetate buffer solution (CH3COOHCH3COONa) 100 ml of 0.1 M NaOH solution and the pH will change from 4.73 to 4,82, i.e. less than 0.1. If you add lye to water, the concentration of hydroxide ions increases, the concentration of hydrogen ions decreases and the pH of the solution will change significantly (from 7 to 11,95).

Thinning proposed foamable composition of water has virtually no effect on the change in pH of the medium. The interaction of the initial components of foam formulations occurs with the formation of water soluble compounds and gaseous products.

The dependence of the rate of outgassing temperature for some values of pH of the medium of the composition shown in table. 3, which shows that gasanalysis solution and foam formation occurs at relatively low temperatures.

Laboratory tests composition for well development was carried out on the installation represents the model of the borehole when the heating system with a speed of 3-5aboutWith over 1 min.

To obtain a foam system serves two solution of 20.0 g, containing the first solution of sodium nitrite, and the second the remaining components of the composition so that when the mixing weight ratio of initial components in a mixture, as well as for the prototype correspond to the given values in the table.3.

For example, under item 5, to obtain a foam system when the pH of the medium is equal to 5.5, are two solutions: the first solution of 2.3 g of sodium nitrite dissolved in water so that the total weight was 20.0 g, and prepare a second solution, with thorough stirring for 15-20 min, 0.2 g of sulfinol NP-3, 1.0 g of urea, 3.3 grams of sodium hydroxide and 6.7 ml of 100% acetic acid (or in terms of dry residue 7.0 g) in water so that so the total weight was 20.0 g

Freshly prepared solutions are combined and experience obtained composition for foaming ability when heated.

From the results ispita (brown gas), and at a pH of 6.0, the reaction gas is feasible at temperatures above 100aboutC. Further increase in temperature promotes thermal hydrolysis of urea (1).

Thus, to reduce corrosion of equipment and depth of the course of chemical interaction between gas-emitting components of the composition, the pH of the buffer solution must correspond to values not less 4,0, but not more than 6,0.

The upper boundary conditions of the ratio of initial components, wt. in the proposed structure determines the solubility of sodium nitrite in water, equal to 44.9% at a temperature of 20aboutC.

When the pH of the medium buffer solution is 4.0 and 6.0, these boundary conditions are given in table.4.

The bottom boundary conditions are based on the results of laboratory tests of the proposed structure on the unit with temperature control system temperature 80aboutC.

The results of the experiment are given in table.5 and show that the formation of foam is quite active and foamable composition is operable, when the content of the source, wt. it in 2.0-2.5 times lower from the maximum possible values.

For example, at pH 5 (table.4) lubricate the other gas-emitting components in stoichiometric proportions (table. 5) you can get the foam with a multiplicity higher than 5,0.

Offer foamable composition for exploration wells with a volume of 1 m3allows you to get to the bottom hole foam with adjustable speed gas saturating solution, and 30 and above litres per one cycle (0.5-1.5 h).

P R I m m e R. For call flow of fluid from the reservoir of the production well with the repair depth of 1600 m, equipped with 168 mm production column and 50 mm tubing, opened the seams of 7.0 m and the temperature at the bottom hole 65aboutTo learn well, we offer foam composition. You must determine the volume of the composition and amount of each source of reagent gas saturating solution at the well bottom and bottom-hole formation zone; the amount of squeezing liquid with a radius of penetration of the composition into the reservoir of 0.5 m

For a composition containing urea, sodium nitrite, acetic acid, sodium hydroxide, surfactants (sulfinol NP-3) and water, are found from the graphs of the dependencies:

the rate of gas release (Fig.1) from the pH of the medium and temperature, to obtain the maximum amount of foam at a temperature of 65aboutWith a pH buffer mixture should be 4,0;

the pH of the medium from the weight ratio of acetic acid to the popular masses of these components:

acetic acid CH3COOH: (12+3)+12+2x16+1=60,0 g/mol;

sodium hydroxide NaOH: 23+16+1=40,0 g/mol.

Then the stoichiometric coefficients in the chemical equation (8) with V= 1,0:

a 5,0

General chemical equation outgassing:

5CH3COOH+7NaOH+2(NH2)2CO+4NaNO2__ 2,50

sodium hydroxide: sodium hydroxide: 0,33

sodium nitrite: sodium nitrite: 2,30

urea: urea: 1,0

Under normal conditions, 1 g/mol of gas occupies a volume of 22.4 l, then the volume of the gas: V=(4+2)x22,4=RUR 134.4 l or 1 g/mol initial substances are formed:

182,6 ml/g

The maximum solubility of sodium nitrite at 20aboutFrom 44.9% in water weight ratio gas-emitting components and water will be:

Urea 1,00

Sodium nitrite 2,30

Acetic acid 2,50

Sodium hydroxide 0,33

Water water 5,12

The volume of the reservoir or the foaming composition is found from the expression

QKr2h, where 3,14

To the average coefficient porosity of the reservoir rock, 0.3;

r is the radius of penetration, m;

h opened the thickness of the layer, m

Q=0,3x3,14x0,52x7,0=1649,3 l

When the content of surfactant in the composition is 0.2 wt. the amount of each component should be kg:

Urea/ Krist. Urea/ Krist. 146 the oxide sodium/ Krist. The sodium hydroxide/ Krist. 48,4

Water water: 749,1 or mass content of these reagents in part,

Urea 8,9

Sodium nitrite 20,4

Acetic acid 22,2

Sodium hydroxide 2,9

SURFACTANTS 0,2

Water 45,4

If 1 g of the original gas-emitting components forms 182,6 ml of gas at normal conditions, 1646,0 kg of solution form: (89+ 204+ 222+29) x1,h,1826= 163,5 m3gases or about 45,0 l/sec, provided that the reaction gas at reservoir conditions will be fully completed within one hour.

Prepare for a solution consistent with the dissolution of the estimated number of components, pump series pump-compressor pipe (tubing) 3-5 m3oil foamable composition is forced into the reservoir oil with a volume of not less than:

q H

q the amount of squeezing liquid or tubing, m3;

d the diameter of the tubing, m;

N the depth of the hole (perforation), m;

3,14

q 3,14 m3< / BR>
Well close to the reaction and incubated for 0.5-1.5 h, then gradually release the pressure through the annulus or tubing, exercise the call flow of fluid from the reservoir.

Instead of sodium nitrite can be used nitrites other alkaline or alkaline-zemulator case is no different from the interaction of these agents with other components.

Examples of preparation and use when it is not fundamentally different, the difference is only in quantitative proportions of interacting components, which are calculated using the General equation of the reaction (8).

In Fig.2 and 4 are graphs of the pH environment of the buffer solution from the weight ratio of potassium hydroxide to acetic acid and speed of gas saturation of the solution depending on the pH of the medium and the temperature of the solution.

The proposed method for foaming solution for well development is not time consuming and does not require special techniques and equipment that can be used for obtaining foam, foam cements, penopolimer, lightweight drilling fluids and cement slurries, the elimination of sand plugs in wells, well completion and stimulation of other processes of oil and gas.

FOAMABLE COMPOSITION FOR DEVELOPMENT of WELLS containing urea, nitrite, alkali or alkaline earth metal, acetic acid, surface-active substance (surfactant) and water, characterized in that it additionally contains an alkali metal hydroxide in the following ratio, wt.

Mohawked alkali metal 8,6 21,6

SURFACTANTS 0,5 1,0

Water The Rest

 

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