RU2486226C1 - Viscoelastic composition for sealing influx of water into well - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to oil and gas industry, particularly viscoelastic compositions used to seal influx of water into a well. The viscoelastic composition for sealing influx of water into a well contains, wt %: polyvinyl alcohol - 5-7, surfactant Polyfos- 0.5-2.0, Protectol GA 50 - 0.2-0.5, water - the balance.

EFFECT: improved processing properties due to controlled gelling time and viscosity which enables the composition to penetrate into a porous medium, high adhesion to metal pipes, improved insulation properties which enable to form a reliable insulating shield.

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Description

The invention relates to the oil and gas industry, in particular to viscoelastic compositions (WCS) used to isolate water inflows into the well.

Analysis of the current level of technology showed the following:

- known viscoelastic grouting mortar, the formulation of which has the following ratio of ingredients, wt.%:

2% solution of polyacrylamide (PAA) 49.3-97.3 Technical formalin 1.2-2.7 5% solution of KMTS-600 1,5-49,5

(see USSR AS No. 933948, declared. 09/26/1980 according to class E21B 33/138, publ. 07/07/1982).

The disadvantage of this solution is the following: PAA, which has a molecular weight of the order of 10 ⁵ -10 ⁶ D, is used as the polymer ingredient in the solution, therefore, the aqueous solution of the specified polymer will have a high viscosity. The joint use in the formulation of a solution of two PAA and KMC-600 polymers gives it high viscosity values. As a result, the scope of this solution will be limited only by highly permeable and fractured reservoirs.

The gelation time, equal to 1-20 days (see the description table for the invention), is technologically unjustified, as it leads to unproductive costs and the cost of insulation work.

Crosslinking of PAA macromolecules with formaldehyde is known to occur at low pH values. The absence of a pH-reducing ingredient in the formulation of the solution will lead to the formation of an insufficiently strong viscoelastic cement slurry that is not resistant to dilution with produced water, the use of which will not provide a reliable insulating screen, that is, it is not possible to effectively use this solution to isolate water inflows into the well. Viscoelastic cement slurry has a low adhesion to the pipe metal. This is due to the release of water from the gel structure (syneresis), which will help weaken the bonds between the viscoelastic cement slurry and the pipe metal surface in contact with it;

- as a prototype taken viscoelastic composition to isolate water inflows into the well, the formulation of which has the following ratio of ingredients, wt.%:

PAA 0.3-0.5 Formalin 0.4 Polyaminomethylphosphonic acid PAF-13A brands 0.3-2.0 Water rest

(see USSR AS No. 1789664, declared March 26, 1990, according to class Е21В 33/138, С09К 3/00, published January 23, 1993).

The disadvantages of this WCS are the following: as a water-soluble polymer, PAA is used, which has a molecular weight of the order of 10 ⁵ -10 ⁶ D, therefore, an aqueous solution of this polymer will have a high viscosity. In addition, when a PAF-13A grade scaling inhibitor is introduced into the mixture of a PAA solution and an α-formalin structurant, a rapid increase in the composition viscosity will occur. As a result, the scope of this solution will be limited only by highly permeable and fractured reservoirs. The high viscosity of the WCS makes it difficult to download.

It is known that crosslinking of PAA macromolecules with formaldehyde occurs at low pH values. The introduction of a scaling inhibitor of the PAF-13A grade, exhibiting acidic properties, into a mixture of PAA and formalin solutions will lead to accelerated crosslinking, as a result of which the composition will not have an adjustable gelation time and will not ensure its sufficient penetration into the porous medium.

This WCS also has reduced adhesion to the metal of the pipes, and therefore it is not possible to use it effectively to isolate water inflows into the well. This is due to a change in the initially formed structure with the conformation of polymer macromolecules as a result of the influence of the used crosslinking system. In this case, weakening of the bonds between the WCS and the pipe metal surface in contact with it occurs. Similar phenomena will occur at the boundary of the contact "rock - VUS". A decrease in adhesion will in turn lead to re-inflow into the well, which will require additional work to isolate the inflow into the well and, accordingly, additional costs for the work. Creating a reliable insulating screen will not happen.

The technical result that can be obtained by implementing the invention is reduced to the following:

the improvement of technological properties due to the controlled gelation time and viscosity, which ensure the penetration of the composition into the porous medium, increased adhesion to the metal of the pipes, high insulating properties, which ensure the creation of a reliable insulating screen.

The technical result is achieved using the well-known WCS for isolating water inflows into a well, including a water-soluble polymer, an alkyl phosphate compound, an aldehyde-containing substance and water, which contains polyvinyl alcohol as a water-soluble polymer, and the surface-active substance Polyphos as an alkyl phosphate compound, and as a polyphosphate compound aldehyde-containing substances - Protectol GA 50 in the following ratio of ingredients, wt.%:

Polyvinyl alcohol 5-7 Surface active agent Polyphos 0.5-2.0 Protectol GA 50 0.2-0.5 Water rest.

The inventive WMC meets the condition of "novelty."

Polyvinyl alcohol according to TU 6-05-313-85, polyphos surface-active substance according to TU 2439-016-714-62031-2008, Protectol GA 50 from BASF (Germany) is a 50% aqueous glutaraldehyde solution. The interaction of the ingredients used in the WCS in the indicated amounts is as follows: as a result of the polycondensation of polyvinyl alcohol with glutaraldehyde, which is part of Pretectal GA 50, a crosslinked polymer structure is formed. In this case, one aldehyde group of the glutaraldehyde of the reagent Protectol GA 50 reacts with two hydroxyl groups that are part of one polyvinyl alcohol chain, and the other aldehyde group binds to the neighboring polyvinyl alcohol macromolecule to form a complex compound of the following structure

Glutaraldehyde reacts with polyvinyl alcohol at low pH values. The role of the pH regulator is performed by the polyphos surfactant, which is a mixture of mono- and dialkyl phosphates in the acid form of the following formula

ROPO (OH) ₂ and (RO) 2POOH,

where R is the primary alkyl fraction of C ₈ -C ₁₀ .

The ether groups of -OR alkyl phosphates are able to hydrolyze in time, forming alkyl phosphoric and phosphoric acids, which are stronger than mono- and dialkyl phosphates, which makes it possible to control the gelation time of WCS (the process of crosslinking of polymer macromolecules), which leads to an improvement in its technological properties.

The formation of the spatial structural framework of chemically crosslinked gels based on polyvinyl alcohol and glutaraldehyde proceeds in time. After mixing the ingredients for some time, the liquid sol externally remains unchanged, then there is a rapid and pronounced increase in the viscosity of the solution, which ends with quasi-curing. According to the statistical theory of gelation, a gel point is characterized by the appearance of an infinite cluster in the reaction system. Increasing the concentration of the crosslinking agent above the gel point leads to gel hardening. The duration of the induction period is determined by the rate of diffusion of glutaraldehyde molecules surrounded by hydration shells into the interglobular space of the polymer molecules. According to the theory of percolation, the formation of chemically crosslinked gels is a critical phenomenon and is characterized by a gel point at which the rheological properties of the system change dramatically. The appearance in the system of an infinite cluster of coupled structural elements is preceded by a rapid increase in viscosity due to the formation and growth of ordered regions of the microgel — finite clusters, whose correlation radius tends to infinity as it approaches the gel point. Above the gel point, an increase in gel strength occurs over time, as a result of which the proposed WCS is characterized by high insulating properties, which allow for complete blockage of the pores of the insulated formation and ensure the creation of a reliable insulating screen.

Improving the technological properties of WCS is also due to viscosity values, which provide, along with the controlled gelation time, the penetration of the composition into a porous medium.

In addition, during the hydrolysis of mono- and dialkylphosphates, C ₈ -C ₁₀ heavy alcohols are released, which, due to their hydrophobicity, increase their resistance to formation water.

The inventive WCS is characterized by increased adhesion to the metal of the pipes, which is due to the following: polyvinyl alcohol and Polyphos are pronounced hydrophilic compounds that well wet the metal surface of the pipes, which also has hydrophilic properties, resulting in close contact between the molecules and functional groups of polyvinyl molecules alcohol, surfactants and metals. Next, there is a direct interaction of the crosslinkable polymer and the metal surface, which is caused by various forces - from Van der Waals to chemical. Such intermolecular interaction of the contacting phases leads to increased adhesion, which corresponds to the minimum interfacial energy. The course of the described processes leads to the formation of a durable fluid-tight sealing frame, reliably adhered to the surface of the pipes, eliminating water inflow into the wells.

The content in the WCS of polyvinyl alcohol in an amount of more than 7 wt.%, Substances of the surface-active "Polyphos" in an amount of more than 2.0 wt.%, Protectol GA 50 in an amount of more than 0.5 wt.% Is impractical, since the technological properties are deteriorating - viscosity indicators increase, gelation time is reduced below the technologically necessary for the delivery of WCS to an isolated interval, resulting in complications when pumping during use.

The content of polyvinyl alcohol in the HCL in an amount of less than 5 wt.%, The substances of the surface-active Polyphos less than 0.2 wt.%, Protectol GA 50 less than 0.5 wt.% Is impractical, since the insulation and adhesive properties of the WCS are deteriorating.

Thus, according to the above, the SCC ensures the achievement of the claimed technical result.

Not identified, according to available sources of fame, technical solutions having features that match the distinctive features of the invention according to the claimed technical result.

The inventive VAS meets the condition of "inventive step".

In more detail, the essence of the claimed invention is described by the following examples.

Examples (laboratory).

Example 1. To prepare 1000 g of WCS in 943 ml (94.3 wt.%) Of water, 50 g (5.0 wt.%) Of polyvinyl alcohol are dissolved in a water bath. 4.66 ml (0.5 wt.%) (Ρ = 1.074 g / cm ³ ) of the surfactant Polyphos substance, 1.77 ml (0.2 wt.%) (Ρ = 1.129 g / cm ³ ) Protectol GA 50. The gelation time is determined, and after 24 hours the properties of the WCS are determined.

Technological properties of WCS: gelation time τ _g = 210 min, conditional viscosity of the composition HC = 190 s, water permeability: before treatment - 3.8 μm ² , after processing - 0.011 μm ² , blockage coefficient K = 99.7%. Adhesion to metal P _m = 0.13 MPa.

Example 2

Prepare 1000 g of VUS, g / wt.%:

Polyvinyl alcohol 70 / 7.0 Surface active agent Polyphos 20 / 2.0 (use 18.6 ml ρ = 1074 kg / cm ³ ) Protectol GA 50 5.0 / 0.5 (use 4.4 ml ρ = 1,129 g / cm ³ ) Water 905 / 90.5

All operations are carried out as described in example 1.

Technological properties: τ _g = 45 min, HC = 363 s, water permeability: before treatment - 4.1 μm ² , after processing - 0 μm ² , K = 100%. Adhesion to metal P _m = 0.16 MPa.

Example 3

Prepare 1000 g of VUS, g / wt.%:

Polyvinyl alcohol 60 / 6.0 Surface active agent Polyphos 12.5 / 1.25 (use 11.6 ml ρ = 1074 kg / cm ³ ) Protectol GA 50 3.5 / 0.35 (use 3.1 ml ρ = 1,129 g / cm ³ ) Water 924 / 92.4

All operations are carried out as described in example 1.

Technological properties: τ _g = 125 min, HC = 278 s, water permeability: before treatment - 3.5 μm ² , after processing - 0 μm ² , K = 100%. Adhesion to metal P _m = 0.15 MPa.

Thus, the claimed technical solution meets the conditions of "novelty, inventive step, industrial applicability", that is, is patentable.

Claims (1)

A viscoelastic composition for isolating water inflows into a well, including a water-soluble polymer, an alkyl phosphate compound, an aldehyde-containing substance and water, characterized in that it contains polyvinyl alcohol as a water-soluble polymer, the polyphos surface-active compound and the aldehyde as an aldehyde substances - Protectol GA 50 in the following ratio of ingredients, wt.%:
Polyvinyl alcohol 5-7 Surfactant Polyphos 0.5-2.0 Protectol GA 50 0.2-0.5 Water Rest