RU2365612C1 - Composition for preparation of technological liquid for completion and reparing of oil and gas wells - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to oil-and-gas producing field, is intended for completion and preparing of oil and gas wells and can be applied in conditions of anomalously high stratum pressures and high temperatures for primary and secondary opening of productive starta, for damping and carrying out different kinds of works, including works in multi-stratum wells, which have different stratum pressure and stratum permeability, as well as in presence of hydrogen sulfide in well products. Composition for preparing technological liquid for completion and repair of oil and gas wells contains, wt %: calcium chloride 13.3-21.9, calcium nitrate 13.3-21.9, zinc chloride 52.55-72.1, sodium chloride 0.5-2.35, sodium benzoate 0.80-1.30.

EFFECT: increase of technological liquid density, reduction of filtering indexes at temperatures 120°C and higher, including deposits with hydrogen chloride containing products.

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Description

The invention relates to the oil and gas industry, is intended for completion and repair of oil and gas wells and can be used in conditions of abnormally high reservoir pressures and high temperatures for primary and secondary opening of reservoirs, for killing and performing various types of work, including in multilayer wells having different reservoir pressure and permeability of the reservoirs, as well as in the presence of hydrogen sulfide in the well products.

A known composition for the preparation of high-density process fluid without a solid phase for completing and repairing oil and gas wells, containing calcium nitrate, including an organic filter reducing agent based on hydroxyethyl cellulose and a corrosion inhibitor (USSR Author's Certificate 1684308, C09K 7/04 09/13/89) .

The disadvantages of this composition and liquids based on it are increased corrosion activity, as well as a violation of stability and other technological properties at temperatures above 100 ° C and the action of hydrogen sulfide. The density of the liquid does not exceed 1.53 g / cm ³ , and therefore, with possible dilution in contact with formation water, it cannot be restored to its original value. When interacting with hydrogen sulfide, the corrosivity of such a liquid increases sharply, and the resulting solid phase significantly reduces the permeability of productive formations. In addition, with an increasing share of transportation costs in the cost estimate, transportation of liquid products is economically disadvantageous. Being a technical product, the composition often contains up to 1% of solid phase insoluble in hydrochloric acid (mainly calcium phosphates). The above disadvantages significantly narrow the scope of the composition and process fluids based on it.

The closest in essence to the claimed invention is a composition for preparing a process fluid without a solid phase for completing and repairing oil and gas wells, containing calcium nitrate, calcium chloride and a corrosion inhibitor (RF patent No. 2291181, IPC C09K 8/06, 2007 g.).

The main disadvantage of the liquid prepared on the basis of this known composition is its low density, which does not exceed 1600 kg / m ³ , which significantly narrows the scope of the composition.

The technical result of the claimed solution is to expand the scope of the composition for the preparation of process fluids by increasing its density, as well as by reducing filtration rates at temperatures of 120 ° C and higher, including in fields with hydrogen sulfide-containing products.

The specified technical result is achieved in that the composition for the preparation of process fluids for completing and repairing oil and gas wells, containing calcium nitrate, calcium chloride and a corrosion inhibitor, additionally contains zinc chloride, sodium chloride, and sodium benzoate is used as a corrosion inhibitor in the following ratios components, wt.%:

Calcium chloride 13.3-21.9 Calcium nitrate 13.3-21.9 Zinc chloride 52.55-72.1 Sodium chloride 0.5-2.35 Sodium benzoate 0.80-1.30.

Process fluids based on the claimed composition can be prepared by dissolving it in fresh water, including containing a polymer based on microbial polysaccharide in an amount of up to 0.2 wt.%.

Zinc chloride is added to the composition to increase the density of the resulting solution due to its high solubility.

Sodium chloride is added to the composition to generate a water-soluble colmatant. When dissolving the inventive composition in fresh water, including containing a polymer based on the microbial polysaccharide in an amount of up to 0.2 wt.%, All components dissolve. When the solution reaches a density of 1450-1550 kg / m ³ and above, sodium chloride begins to crystallize from the solution in the form of a fine suspension. Subsequently, the sodium chloride included in the composition does not dissolve. Thus, a water-soluble colmatant is formed in the solution, which is formed by particles of sodium chloride ranging in size from a few microns to 1-3 mm, which makes it possible to reversibly clatter productive formations of various permeabilities. An important advantage of sodium chloride is its practically temperature-independent solubility, which allows the use of the inventive composition at various reservoir temperatures.

Sodium benzoate is added to reduce the corrosion activity of solutions prepared on the basis of the claimed composition. It is known that in aqueous solutions, part of the zinc chloride molecules are hydrolyzed, as a result of which protons are formed, the solution becomes acidic and, as a result, corrosive.

Upon dissolution of sodium benzoate, the benzoate ion binds a proton with the formation of weakly dissociating benzoic acid (K _diss = 6.3 · 10 ^-5 ), as a result of which the corrosion activity of solutions is significantly reduced.

Obtaining process fluids with a density of up to 1950 kg / m ^{3 is} achieved by simultaneously dissolving in water a mixture of calcium chloride, calcium nitrate, zinc chloride, sodium chloride and sodium benzoate.

The preparation of the claimed composition is made by mixing the components. Preparation of process fluids is carried out by dissolving the dry salt composition of the obtained composition in fresh water or in a solution of the microbial polysaccharide in an amount of up to 0.2 wt.% In fresh water.

For comparison with the claimed composition below are examples of the preparation of liquids known from the prototype without a solid phase.

Example 1

980.7 g of calcium nitrate, 15.50 g of hydroxyethyl cellulose and 3.80 g of corrosion inhibitor IKB-4H were dissolved in 550 ml of fresh water. Received 1000 ml of liquid with a density of 1.55 g / cm ³ . The obtained liquid was measured filtration rate immediately after preparation and after temperature control of the samples at 130 ° C for 72 hours

Example 2

640 g of calcium chloride, 320 g of calcium nitrate, 10 g of a divalent metal compound, for example magnesium oxide, 10 g of a filtration reducing agent, for example polyanionic cellulose, and 20 g of a corrosion inhibitor, for example hexamethylenetetramine, were mixed in a mechanical stirrer. The resulting 1000 g of the composition was dissolved in 488 ml of fresh water. The resulting 930 ml density brine

1.60 g / cm ^{3 was} tested analogously to example No. 1.

The following are examples of the preparation of process liquids without a solid phase based on the inventive salt composition.

Example 3. In a mechanical stirrer mixed 133 g (13.3 wt.%) Calcium chloride, 133 g (13.3 wt.%) Calcium nitrate, 721 g (72.1 wt.%) Zinc chloride, 5 g (0 5 wt.%) Sodium chloride and 8 g (0.8 wt.%) Sodium benzoate. The obtained 1000 g of the composition was dissolved in 272 ml of fresh water. The resulting 669 ml of brine with a density of 1.90 g / cm ^{3 was} tested analogously to example No. 1.

Example 4. In a mechanical stirrer mixed 219 g (21.9 wt.%) Calcium chloride, 219 g (21.9 wt.%) Calcium nitrate, 525.5 g (52.55 wt.%) Zinc chloride, 23, 5 g (2.35 wt.%) Sodium chloride and 13 g (1.3 wt.%) Sodium benzoate. The resulting 1000 g of the composition was dissolved in 252 ml of fresh water. The resulting 642 ml of brine with a density of 1.95 g / cm ^{3 was} tested analogously to example No. 1.

Example 5. In a mechanical stirrer mixed 176 g (17.6 wt.%) Calcium chloride, 176 g (17.6 wt.%) Calcium nitrate, 623.25 g (62.325 wt.%) Zinc chloride, 14.25 g (1.425 wt.%) Sodium chloride and 10.5 g (1.05 wt.%) Sodium benzoate. The resulting 1000 g of the composition was dissolved in 252 ml of fresh water. The resulting 642 ml of brine with a density of 1.95 g / cm ^{3 was} tested analogously to example No. 1.

Example 6. In a mechanical stirrer mixed 219 g (21.9 wt.%) Calcium chloride, 219 g (21.9 wt.%) Calcium nitrate, 525.5 g (52.55 wt.%) Zinc chloride, 23, 5 g (2.35 wt.%) Sodium chloride and 13 g (1.3 wt.%) Sodium benzoate. The resulting composition was dissolved in 252 ml of fresh water, in which 0.45 g of the microbial polysaccharide was previously dissolved. The resulting 642 ml of brine with a density of 1.95 g / cm ^{3 was} tested analogously to example No. 1.

The test results are shown in the table.

The composition of the process fluid Process Fluid Properties Density, g / cm ³ Conditional viscosity T, s Filtering index at 20 ° C cm ^3/30 min Filtering index at 130 ° C and? P = 3 MPa after heating at 130 ° C for 72 h in cm ^3/30 min one 1,53 40 35 unlimited 2 1,60 fifty 26 unlimited 3 1.90 110 12 12 four 1.95 250 5 5 5 1.95 450 0 one

From the tabular data it is seen that the introduction of dry sodium salt into the composition of the dry salt composition, especially in combination with a thickener, for example, based on the microbial polysaccharide, significantly expands the scope of application of process fluids prepared on its basis.

Filtration is an indicator characterizing the ability of process fluids to filter under a certain pressure drop (penetrate into the reservoir).

Filtration seek to maintain at a minimum level to eliminate the decline in reservoir productivity and prevent the loss of expensive fluids.

In particular, the rate of filtration of the prepared solutions sharply decreases at a temperature above 120 ° C.

Claims (1)

Composition for the preparation of process fluids for the completion and repair of oil and gas wells, containing calcium nitrate, calcium chloride and a corrosion inhibitor, characterized in that it additionally contains zinc chloride, sodium chloride, and sodium benzoate is used as a corrosion inhibitor in the following ratios of components, wt.%:
Calcium chloride 13.3-21.9 Calcium nitrate 13.3-21.9 Zinc chloride 52.55-72.1 Sodium chloride 0.5-2.35 Sodium benzoate 0.80-1.30