Foamable composition for well development

 

(57) Abstract:

The invention relates to the oil and gas industry, in particular foaming compositions for completion. Foamable composition for development of wells containing urea, nitrite, alkaline or alkaline-earth metal, surface-active substances (surfactants), water, a foam stabilizer (flotation) and hydrolittoral or ammonium hexafluorosilicate, and as a foam stabilizer (flotation reagent) contains a water-soluble polymer compound carboxymethylcellulose (CMC) or polyacrylamide (PAA). Introduction to foam system a water-soluble polymer compounds contributes to the improvement of the characteristics of the foam and its carrying capacity with borehole bottom solids, sand, asphalt-parapanamerican substances and corrosion products on the surface due to the foam flotation forces.

The invention relates to the oil and gas industry, in particular foaming compositions for well development.

Known for well stimulation fluid from the reservoir containing urea, sulfate of aluminum, surface-active substance (surfactant) and water [1]

Gasanalysis solution is to cut the tsya:

limited thermal conditions over the course of a chemical reaction, hydrolysis of urea occurs at temperatures above 100oC;

gaseous products of the hydrolysis of urea into ammonia and carbon dioxide are soluble in water, especially in situ, therefore, a low degree of gas saturation of the solution.

Known self-generating foam system containing urea, surfactants, nitrite, alkaline or alkaline-earth metal, an acid, methenamine and water [2]

As gasanalysis agent in this composition are carbon dioxide and the inert gas is nitrogen, resulting from the interaction of initial components:

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The disadvantages of this system are: low foam stability, low efficiency of recovery of the formation permeability and the high cost of development wells.

The aim of the invention is to reduce costs and increase the effectiveness of development wells due to depression on a layer with simultaneous mud acid and thermal treatment of bottom-hole formation zone, as well as flushing and cleaning of the bottom hole from the solids, corrosion products and asfaltoprugnacam substances and removing them on the surface for the Fes system for well completion, contains urea, nitrite, alkaline or alkaline-earth metal, a surfactant, an acid and water, further comprises pinacolato hydrolittoral or ammonium hexafluorosilicate, foam stabilizer (flotation) carboxylmethylcellulose (CMC) or polyacrylamide (PAA) under the following ratios of the starting components, mass.

urea 1,3-5,2

nitrite, an alkaline or alkaline-earth metal 5,4-20,8

acid 0,4-1,6

hydrofloric or ammonium hexafluorosilicate 1,9-7,4

CMC or PAA of 0.1 to 1.9

SURFACTANTS OF 0.04 TO 0.9

water the rest.

Gasanalysis and foaming occurs spontaneously upon mixing the starting components for any positive temperature.

The General scheme of interaction of the reagents without the addition of acid:

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and in the presence of acids in the initial ratio of components a chemical reaction occurs with the additional formation of gaseous products:

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or General chemical reaction equation can be written:

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where IU alkaline or alkaline-earth metal;

and the ratio of chemical equations;

m index the chemical formula of a molecule of a substance.

The reaction of formation of gaseous products fully offset the education gaseous products, water and poorly soluble in water fluorides of alkali and alkaline-earth metals, in addition to potassium fluoride. The solubility of these salts in 100 g of water are presented in table. 1.

Additionally introduced hydrolittoral or ammonium hexafluorosilicate as a result of hydrolysis or interaction with the acid to form hydrofluoric acid, which reacts and dissolves carbonate and clay-containing rock formation.

In table. 2 shows the results of laboratory tests showing the ability of an aqueous solution of hydrovhloride ammonium dissolving clay-containing rock and bentonite clay at a temperature of 20oC. a More concentrated aqueous solution of hydrovhloride ammonium react with samples of rocks dissolves and destroys them due to disjoining pressure. Use in combination with hydrovhloride ammonium volatile acids (hydrochloric, formic, and so on) in the foamable composition can increase permeability for gas, and thus it is possible to cover the foam composition layer with a large radius of influence.

For example, physico-chemical properties of hydrogen chloride (hydrochloric acid), which has a critical temperature 51,4oAnd critical is>Additionally introduced into the composition hydrolittoral or ammonium hexafluorosilicate when exposed to nitrites of metals produces nitrogen gas and emit thermal energy.

The chemical interaction of these compounds has the following form:

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Location azotistogo ammonium almost instantly. Thus, to improve the effectiveness of development wells due to mud acid and heat treatment of bottom-hole zone stoichiometric ratio of initial components should be calculated according to the following generalized chemical equation:

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where IU alkaline or alkaline-earth metal;

and the ratio of chemical equations;

m index the chemical formula of a molecule of a substance.

but 4.0; m 1,0, when IU alkali metal;

a 2,0; 2,0 m, when IU alkaline-earth metal.

In the case when glyoxylate in the proposed composition is ammonium hexafluorosilicate, the General scheme of interaction of gas-emitting components has the following form:

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where IU alkaline or alkaline-earth metal;

m index the chemical formula of a molecule of the substance;

a 0.8 coefficient khimicheskogo the deposits of the mass content of the acid in the foamable composition should be increased, then the General scheme of interaction (8) takes the form:

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where A; B; C; D are the coefficients of a chemical equation;

m index the chemical formula of a molecule of a substance.

The coefficients of a chemical equation depend on the mass content of acid and glyoxylate and the weight ratio between them. Stoichiometric coefficients And before metal nitrite and urea are determined from the following relations

BUT 2C + D;

Then the General scheme (10) is:

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The weight ratio of acid to glyoxylate when carbonate inclusions in a productive reservoir tend to zero and must be less than the value of 4.76.

Consider the special case when 0; D 2; m 1; Me Na, then the chemical equation is written

(NH2)2CO+2NaNO2+2H2+_

Introduction the proposed composition of the surfactant and water-soluble polymeric compounds of the type CMC or PAA increases the stability and flotation properties of the foam. These physico-chemical properties of the foam are significantly improved when the content in the foam composition of polymer compounds in amounts of 0.5 to 1.5 mass. when the surfactant concentration 0.1-0.5 mass. [3]

Technology is the practical application of the foam composition provides OS is Les repairs.

Example. Foamable composition is prepared in the form of two solutions, and test it in a laboratory setup, which is a model of the well, at a temperature of 20oC.

Prepare a water solution of N 1, containing urea, sodium nitrite and surfactants (OP-10) with a density of 1.06 to 1.35 g/cm3.

A solution of N 2 in the form of a finely dispersed suspension with a density of 1.02 to 1.15 prepared by dissolving hydrovhloride ammonium in aqueous acid solution and CMC concentration from 1.0 to 3.0%

The stoichiometric ratio of initial components are calculated according to chemical equation (8).

The obtained solutions are sequentially injected into the model of the well, filled with 10-15% of its height oil with a density of 0,86 g/cm3or kerosene with a density of 0.82 g/cm3. The results of laboratory tests are shown in table. 3, which shows the ratio of the foam, the temperature change of the solution.

The boundary of the ratio of initial components depend on the solubility of the nitrites of metals in water and the density of the aqueous solution of N 1, and the degree of dilution of its components in real conditions. For example, the solubility of sodium nitrite with 100 g of water at 20oWith 82,9 g or 45.3 per cent and potassium nitrite, respectively 3 the different metals in a solution of N 1 are given in table.4.

The bottom boundary conditions are found from the conditions of completeness gravitational drop of the solution of N 1 and the degree of dilution of its components. The concentration of sodium nitrite should meet not less than 8.0% (density 1.06 g/cm3in the proposed structure, then gasanalysis and foam satisfactorily to achieve this goal. The composition containing nitrite potassium less than 12.0 percent (density of 1.09 g/cm3), has unsatisfactory performance.

The boundary conditions below which the performance of the composition (solution No. 1) unsatisfactory, are also given in table. 4.

A solution of N 2 in the form of a finely dispersed suspension contains stoichiometric ratio according to equation (8) hydrolittoral ammonium or ammonium hexafluorosilicate by the equation (9), acid and CMC or PAA.

The solubility of hydrovhloride of ammonia in 1000 ml of water 434 g or 30.3 per cent and ammonium hexafluorosilicate respectively to 187.5 g or 15.8% to obtain a solution of N 2 in the form of a suspension based on water-soluble polymeric compounds of the type CMC or PAA concentration of 1.0 to 3.0 wt. pinacolato injected into a solution of N 2 to 30% in excess of the maximum solubility of these components in water. Volume ratio of solutions N 1 pilotnosti solutions and mass content of the source components in these solutions (see a specific example of the work).

In table. 6 shows the boundary conditions of the ratio of initial components in the foamable composition in the preparation of his solutions of N 1 and N 2, which contains the boundary of the ratio of components in the mixtures, the weight ratio of these solutions in the proposed structure.

On the basis of the obtained results of the proposed foamable composition for well completion method of gravitational fall of solutions to the borehole bottom is easy to perform technological operations, cost-effective and suitable with the same intensity of foaming with other known methods.

Specific example

For call flow of fluid from the low-permeability layers of the production well equipped 168 mm production column a depth of 1900 m, pump-compressor pipe with a diameter of 63 mm, at the end of which hung a pump with a check valve at a depth of 1200 m and a perforation interval 1850-1860 m, it is necessary to determine the amount of the proposed foaming composition and amount of each source component in it to receive the gaseous products with a volume equal to 10 volumes of SLE is I well involves:

1. Replacement of the well fluid in the annulus of oil to the pump intake.

The volume of oil in the inter-space is determined by the following formula:

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where 3,14

D diameter of the production string, m;

d the diameter of the tubing, m;

h is the depth of the suspension pump, m;

V the volume of the annulus, m3:

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2. Sequential injection into the annulus of two types of solutions foaming composition with shutter speeds of 0.5-1.0 hours between feeding into the well of these solutions;

3. The closure of the well and its exposure for 1.0-1.5 hours with the purpose of implementing technological and chemical processes. The process of gas saturation of the solution is controlled by growth pressure at the wellhead, after stabilization which the well is put on the well-springs in the annular space;

4. Run well on production with research on the flow of a liquid.

Note. During the development of production wells operated by the fountain in the manner and without non-return valves and injection wells in and out drilling or after repair work flow and displacement in the layer of foamable composition is performed on tubing.

The sodium nitride with a density of 1.2 the Oia prepare the first part foamable composition (solution No. 1).

Solution No. 2 is prepared in the form of a finely dispersed suspension by dissolving the calculated amount of hydrovhloride ammonium in 24% hydrochloric acid containing 1.5% polyacrylamide.

Based on chemical equations (8) are the stoichiometric ratio of initial gas-forming components:

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Determine the molecular mass of the reacting substances:

2(NH2)2CO 2[(14+2)2+12+16] 120 g/mol

3NH4HF23(14+4+1+2h19) 171 g/mol

HCl 35,5 + 1 36.5 g/mol

7 NaNO27(23+14+2x16) 483 g/mol.

Under normal conditions, 1 g/mol of gas occupies a volume of 22.4 l, then the amount of emitted gases:

V 22,4 (7+2) 201,6 l

or 1 g source of blowing agents:

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To find the mass of the contents of the source components in the foamable composition are the ratio of molecular mass relative molecular mass of urea:

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Taking into account the initial concentration of sodium nitrite 28.00 masses. and when the mass content of surfactant (OP-10) 0,50% solution of N 1 component ratio of the will of the masses.

Urea 6,47

Sodium nitrite date 26,06

OP-10 0,46

Water the rest.

Prepare a solution of N 2 on the basis of polyacrylamide, hydrovhloride ammonium, the components, mass.

Hydrolittoral ammonium 24,98

Hydrochloric acid 5,34

PAA 1,0

Water the rest.

Taking into account that the weight percent in solution N 1 urea 6,47% in solution N 2 hydrovhloride ammonium 24,98% and the ratio of the molecular masses of hydrovhloride ammonium and urea 1,43, the weight ratio of the solutions of N 1 and N 2 must be:

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N 1 N 2 1,00 2,70.

When preparing foamable composition of the obtained solutions in the indicated weight ratios of the proposed structure will have a ratio of initial components, mass.

Urea 4,72

Sodium nitrite 19,02

Hydrolittoral ammonium 6,75

Hydrochloric acid 1,44

PAA 0,27

SURFACTANTS 0,34

Water the rest.

The volume of gases emitted by 1.0 t solution with the same ratio of components will be:

Q (47,2+190,2+67,5+14,4)x0,2487 79,41 m3< / BR>
The problem, in order to receive gaseous products with a volume equal to 10.0 volume well, you foamable composition:

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where n is the required number of foamable composition, t;

3,14;

D diameter of the production string, m;

H is the depth of descent of the production string, m;

Q the volume of gas produced per ton comp is kg:

solution a solution of N1 - 3870,3 or 3870,3/1< / BR>
a solution of N2 - 1433,4 or 1433,4/2< / BR>
where1and2the density of solutions of N 1 and N 2

Urea 250,16

Sodium nitrite 1008,06 or 3.0 m328%

Hydrolittoral ammonium 357,75

Hydrochloric acid 76,32 or 0.30 m324%

OP-10 18,02

PAA 14,31

Water the rest.

Instead of sodium nitrite can be used nitrites other alkaline or alkaline-earth metals, instead of hydrovhloride ammonium ammonium hexafluorosilicate, and instead of hydrochloric acid any acid.

The formation of foam in these cases is no different.

Examples of preparation and use foam composition is not fundamentally different, the difference is only in quantitative proportions of the interacting components.

The proposed method of producing a foaming composition for well development easy and does not require special equipment that can be used for obtaining foam, foam, light weight drilling fluids and cement slurries, the intensification of other processes of oil and gas.

1. Foamable composition for development of wells containing ureas further comprises hydrolittoral or ammonium fluorosilicate preparation and dispersant-foam stabilizer in the following ratio of components, wt.

Urea 1,3 5,2

Nitrite, an alkaline or alkaline-earth metal 5,4 20,3

Acid 0,4 1,6

Hydrolittoral or ammonium fluorosilicate preparation 1,9 7,4

The foam stabilizer (dispersant) 0,1 1,9

The foaming agent 0,04 0,9

Water the Rest

2. Composition under item 1, characterized in that the dispersant is a foam stabilizer used is a water-soluble high-molecular compound sodium salt of carboxymethyl cellulose.

 

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