RU2759301C1 - Method for reducing water content of wells and eliminating intra-and inter-layer water flows - Google Patents

Abstract

FIELD: oil industry.SUBSTANCE: invention relates to the field of elastomeric materials, in particular to the field of elastomeric materials used in oil production to isolate formations and reduce waterlogging of oil and gas condensate wells. Proposed id the method in which a tampon mixture containing a finely dispersed water-swelling rubber fraction is injected into the reservoir under pressure. After pumping the tampon mixture, the well is closed to wait for the swelling of the water-swelling fraction, the time of which is from 24 to 48 hours. At the same time, the grinding size of the applied fraction particles is 60-70% of the average size of the crack in the formation for tamponing. A finely dispersed water-swelling rubber fraction obtained from a rubber mixture based on hydrogenated butadiene–nitrile rubber (HBNR) containing polymer alcohol(s) in the amount of 10.00-30.00 pts. wt. per 100 pts. wt. HBNR and a spatially crosslinked polycondensation copolymer(s) of polyatomic alcohol(s) and acrylic acid in the amount of 25.00–100.00 wt. is used as a tamponing agent .h. per 100 pts. wt. HBNR, as well as a vulcanizing system and technological additives. At the same time diesel fuel is used as a transporting fluid in the tampon mixture.EFFECT: increase in the degree of swelling of the finely dispersed water-swelling rubber fraction in highly mineralized media while preserving the swelling properties in conditions of small mineralization and in low mineralized media, increasing resistance to the action of petroleum products and increasing the efficiency of eliminating intra- and inter-layer water flows, reducing the water content of wells.5 cl, 4 dwg, 4 tbl

Description

Technology area

The invention relates to the oil industry and can be used in oil production and well development. In particular, the invention relates to the field of elastomeric materials, namely, to the field of elastomeric materials used in oil production to isolate formations and reduce water cut in oil and gas condensate wells, eliminate in-situ and inter-reservoir water flows.

State of the art

In the oil industry, swelling materials are widely used to isolate formations and reduce the water cut of oil and gas condensate wells, eliminate in-situ and inter-reservoir water flows. Such materials are packers, seals and various compositions based on elastomeric swellable materials.

The principle of operation of swelling materials is as follows. When a swellable material made from a special elastomer comes into contact with wellbore fluids, it swells, resulting in plugging of the annulus in any open or cased boreholes, in-situ and in-situ. The elastomeric compounds from which the swellable materials are made react to borehole fluids, drilling mud, well injection fluids and are able to increase in volume relative to the volume occupied when running into the well.

Currently, there are many developments in this area and there are many patented developments.

So, for example, patent source WO 03008756, publication date 01/30/2003, describes a method in which a rubber cylinder is placed in the annulus of a well, which is capable of swelling on contact with water or oil, thereby cutting off the flow of water into productive formations.

Patent document RU 2685350 C1, publication date 04/17/2019, describes a water-oil-swellable elastomeric composition based on butadiene-α-methylstyrene rubber and containing a water-swellable reagent - sodium carboxymethylcellulose in an amount of 25.0 - 70.0, as well as components that are customary in technology RTI.

One of the solutions in this area is the patent US 9540501 B2, published on 01.10.2017, which describes a water-swellable rubber compound consisting of a non-swellable rubber base and a hydrophilic elastomer based on ethylene oxide containing from 0 to 20 mol.% Of vulcanizable functional groups, and also water-swellable non-elastomeric material.

Close to the proposed solution in terms of technology, in our opinion, is the method according to the patent RU 2465446 C1, published on October 27, 2012, which includes the injection of a displacing agent through injection and oil production through production wells before watering the well production, leading to unprofitable operation, subsequent injection into wells with a water-insulating composition containing water-swelling particles with an initial size smaller than the flow area of watered cracks, abandoning wells for the time of composition structuring, development and commissioning of wells. At the same time, crumb from an elastomer based on rubber from crushing the profile of a swelling rubber "AQUASTOP" or polyurethane from crushing a sealing gasket "Plow", with an initial particle size smaller than the flow area of watered cracks, is pumped into the production and injection wells as a water-insulating composition in the carrier fluid. but a large flow area of the pores of oil-saturated blocks of the formation, limited swelling in water by at least 300% in 24 hours, with a concentration in the carrier fluid of 3-40 wt.%, the carrier fluid is used on a water basis, thickened with a polymer and containing a viscosity destructor, providing destruction and release of injection water into the reservoir, after injection it is pushed into the reservoir with fresh water.

The main disadvantage of the known method is the use of a water-based carrier fluid, which allows the composition to swell regardless of where it is in the formation - if the injected particle is injected into the interval of the productive formation from which oil is produced, then when the composition swells, access to this area is the reservoir will be limited, which entails limiting oil production from the well. In addition, fresh water entering the oil-containing pores and fractures of the productive formation limits the movement of oil through the formation, since the permeability to water is higher than the permeability to oil in most oil-containing reservoirs.

The closest to the proposed solution in terms of the composition of the material used is the water-swellable rubber material described in document CN 103570985 A, published on 12.02.2014, which consists of 100 pbw. nitrile butadiene rubber, 30-100 parts of superabsorbent resin, 2-10 ionic retention component, 0.5-2.5 parts of a hard softener, 0.5-3.5 pbw. dye, 5-20 parts of a plasticizer, 0.1-2.6 parts of a vulcanizing agent and 5-45 parts of a mixture of polyethylene glycol and diphenylmethane diisocyanate in a molar ratio of 1: 1.

The main disadvantage of this solution is the need to use a highly toxic diisocyanate, insufficient resistance to swelling in the environment of oil and oil products, and high sensitivity to water salinity.

List of drawings

Figures 1-4 are graphs showing the dependence of the change in the volume of the sample on the exposure time in the medium.

FIG. 5 schematically shows an algorithm for calculating the particle size of the rubber fraction.

Disclosure of invention

The purpose of the proposed solution is to overcome the disadvantages of the prior art and develop a rubber composition that effectively operates both in an oil-water emulsion and separately in water and oil media, and provides selective shut-off of water inflow while maintaining oil access from the formation.

The technical result is the development of a rubber composition with an increased degree of swelling in highly mineralized environments, while maintaining the properties of swelling in conditions of low mineralization and in low-mineralized environments, as well as having increased resistance to the action of petroleum products. The degree of swelling of the proposed material in conditions of low mineralization and in low-mineralized environments is sufficient to eliminate in-situ and inter-reservoir water flows, reduce water cut in wells and ensure selective shut-off of water inflow while maintaining oil access from the reservoir.

To solve these disadvantages and achieve the set technical problem, a technology is proposed for eliminating in-situ and inter-reservoir water flows and reducing water cut, in which a finely dispersed water-swelling rubber fraction (water-swelling elastomer crushed into crumbs) is used as a plugging agent, and diesel fuel is used as a transporting fluid. The grind size of the particles used is 60-70% of the average fracture size in the formation for plugging. After the injection of the plugging mixture into the formation under pressure, the well is closed pending the swelling of the water-swellable fraction, the time of which is from 24 to 48 hours, depending on the chemical composition of the produced water.

It is proposed to use a rubber mixture containing as a polymer base hydrogenated nitrile butadiene rubber (GBNKS), polymer alcohols (alcohol) (polyallyl, polyvinyl, poly-1-hydroxymethylethylene, poly-3-phenyl-2-propen-1-ol etc.) in the amount of 10.00-30.00 mass.h. per 100 mass. GBNKS and spatially cross-linked polycondensation copolymers (copolymer) of polyhydric alcohols (a) and acrylic acid in an amount of 25.00-100.00 mass.h. per 100 mass. GBNKS. Additionally, the proposed mixture may contain functional and conventional processing aids, such as softeners, fillers, dispersants, colorants, antioxidants, and also contains a vulcanizing system.

These improved properties have a positive effect on safety when launching equipment, since the rubber fraction swells relatively slowly, as can be seen from graphs 1-3. In addition, the proposed rubber compound has significantly improved swelling properties in highly mineralized environments, which ensures performance in such environments, and the rubber is resistant to the action of oil products. This implies another technical result - versatility, since the proposed rubber fraction can be used in any type of wells, formations or any systems where swelling and stability are required.

The grind size of the particles used is selected in accordance with the size of the cracks and pores in the oil-bearing reservoir - the grind should be less than the flow area of the existing isolated fractures, but larger than the pore size of the reservoir containing oil. Because the crack in a simplified representation has the shape of an equilateral triangle, then the grinding size is selected based on the requirement to block 2/3 of the triangle, thus the recommended particle diameter is 60-70% of the crack size (Fig. 5).

The use of diesel fuel as a transport fluid is due to the preservation of the reservoir properties of the formation - it does not reduce the productivity of the well, at the same time it reacts more slowly with the injected water-swellable composition and allows more successful completion of the operation to reduce the water cut on the well before the moment when the ordered fine elastomer begins to swell.

After the injection of the plugging mixture into the formation under pressure, the well is closed pending the swelling of the water-swellable fraction, the time of which is from 24 to 48 hours, depending on the chemical composition of the produced water. Selective shut-off of the water inflow while maintaining the access of oil from the formation is achieved due to the increased water permeability of the formation, thus pushing the water out of the pores into the depth of the formation crossflow and blocking the water inflow to the oil rim.

The quantitative content of functional additives depends on the quantitative content of the main components and the algorithm for selecting these amounts is an operation well known to those skilled in the art. The selection of a suitable curing system is also well known to those skilled in the art. Additional ingredients are selected based on the specific operating conditions and manufacture of the rubber fraction and do not affect the essence of the invention.

The choice of the ratio of the main polymer components depends on the expected operating conditions of the rubber fraction and can vary within specified limits to achieve the required properties.

For example, the amount of polymeric alcohol (alcohols) can be 11.00, 13.00, 15.00, 20.00, 25.00 parts by weight, the amount of crosslinked polycondensation copolymers (copolymer) of polyhydric alcohols (a) and acrylic acid can be 25.00, 30.00, 40.00, 50.00, 70.00, 90.00 mass. per 100 mass. GBNKS. However, the quantitative ratio of the components is not limited only to the values shown and may include any intermediate values included in the originally indicated ranges.

The choice of the quantitative content of polymeric alcohol and spatially crosslinked polycondensation copolymer of polyhydric alcohols and acrylic acid is due to the achievement of optimal physical and mechanical properties of the rubber mixture. So, when the content is in concentrations above 30 and 100 mass parts, respectively, the strength characteristics of rubbers sharply drop and the withstanding pressure likewise sharply decreases to a level unacceptable in this application. When the concentration of polymers is below the minimum permissible level (10 and 25 mass parts), the effect of the introduction of polymers is not satisfactory and is hardly noticeable.

Hydrogenated nitrile butadiene rubber (NBRB), i.e. hydrogenated (crosslinked with peroxide), belongs to the family of nitrile rubbers and, as the name suggests, is obtained by partial or complete hydrogenation (hydrogenation) of nitrile butadiene rubber (NBR). The resulting rubber significantly outperforms BNK in durability and mechanical properties, while maintaining a relatively low cost.

The properties of GBNKS depend on the content of acrylonitrile and residual double bonds: with an increase in the content of acrylonitrile, the resistance to temperature and oil products increases, but the properties deteriorate at low temperatures. GBNKS exhibits resistance to low and better resistance to high temperatures, and, depending on the brand, has an operating range from -45 to + 165 ° C. HBNKS shows good resistance to ozone, weathering and aging, and is also resistant to hot water and steam up to 150 ° C. GBNKS exhibits good abrasion resistance. HBNKS is resistant to aliphatic hydrocarbons (propane, butane, oil, diesel fuel, fuel oil), vegetable and mineral oils and greases, non-flammable hydraulic fluids (HFA, HFB and HFC). Also resistant to dilute acids, alkalis and salt solutions at medium temperatures. HBNKS shows some resistance to fuels with a high (up to 40%) content of aromatic hydrocarbons. Certain grades of HBNKS with a high acrylonitrile content are also resistant to biofuels and oxygen-containing fuels.

The best known, commonly used and available polymeric alcohols are polyvinyl alcohol and polyallyl alcohol.

Polyvinyl alcohol (C ₂ H ₄ O) _x is an artificial, water-soluble, thermoplastic polymer. The synthesis of PVA is carried out by the reaction of alkaline / acid hydrolysis or alcoholysis of polyvinyl esters. The main raw material for PVA production is polyvinyl acetate (PVA). Unlike most polymers based on vinyl monomers, PVA cannot be obtained directly from the corresponding monomer, vinyl alcohol (VS). Polyvinyl alcohol is an excellent emulsifying, adhesive and film-forming polymer. It has high tensile strength and flexibility. These properties depend on the humidity of the air, since the polymer absorbs moisture. Water acts as a plasticizer on the polymer. At high humidity, PVA decreases tensile strength, but elasticity increases. The melting point is in the region of 230 ° C (in nitrogen atmosphere) and the glass transition temperature is 85 ° C for the fully hydrolyzed form. In air at 220 ° C, PVA decomposes irreversibly with the release of CO, CO ₂ , acetic acid and a change in the color of the polymer from white to dark brown. Glass transition temperature and melting point depend on the molecular weight of the polymer and its tacticity. Polyvinyl alcohol is stable against oils, fats and organic solvents.

Polyallyl alcohol has the structural chemical formula (-CH ₂ -CH (CH ₂ OH) -) _x . Polyallyl alcohol can be obtained in the same way as polyvinyl alcohol by polymer-analogous conversion of polyallyl esters. Polyallyl alcohol is water-soluble. Polyallyl alcohol, like polyvinyl alcohol, readily reacts with aldehydes to give polyacetals. Like polyvinyl alcohol, it absorbs moisture. In general, its properties are sufficiently studied and do not require a detailed description.

Polyvinyl alcohol and polyallyl alcohol are given as examples of polymeric alcohols used and as the most readily available on the market, however, these examples do not limit the use of other representatives of polymeric alcohols, such as poly-1-hydroxymethylethylene, poly-3-phenyl-2-propene -1-ol and similar alcohols. It is possible to use one polymer alcohol or a mixture of several alcohols.

Crosslinked polycondensation copolymers of polyhydric alcohols and acrylic acid are also not new compounds. These compounds are well known and are produced in commercial volumes, for example, according to patents JP 2004018389 and JP 2008184434. These compounds can be obtained by polymerizing acrylic acid with polyhydric alcohols (for example, erythrol, propylene glycol, glycerin, pentaerythritol, butanediol, etc.) in the presence of alkaline catalysts. It is possible to use several copolymers, as well as copolymers with one or more polyhydric alcohols. The indicators of such variants of rubber compounds do not fall and vary within acceptable limits.

Functional additives used in the invention such as softeners, dispersants, fillers, accelerators, curative systems, antioxidants, colorants and the like. are well known to those skilled in the art and require no special disclosure. Suitable additives are disclosed, in particular, in the book "Functional Fillers for Plastics" ed. M. Xanthos, 2010

As for the mechanism for achieving the technical result, this issue has not been fully investigated by us, however, the increased swelling of the proposed rubber mixture is most likely associated with the nature of the polymers themselves, since the backbone of each polymer contains a sufficient number of polar atoms (eg oxygen) that can form hydrogen bonds, thereby causing swelling. Also, it is believed that there is a synergism from the combined use of polymeric alcohols and spatially crosslinked polycondensation copolymers of polyhydric alcohols and acrylic acid, expressed in increased swelling when these two ingredients are used together. This effect is most likely associated with the formation of polyvinyl alcohol copolymer percolation structures due to van der Waals forces, hydrogen and chemical bonds. The stability of all used polymers in relation to oils, fats and organic solvents allows to increase the resistance of rubber powder in oily environments.

It should also be noted that reducing the water cut of wells and eliminating in-situ and inter-reservoir water flows in oil production is not the only area of use for the proposed rubber compound and it can be used in any area requiring the use of materials with water-swelling properties. In particular, this invention can be used to create packers, to create waterproofing materials in construction (between slabs of houses), systems for protecting pipes from leaks, sealing rubbers for swimming pools, for repairing water injection equipment, etc.

Implementation of the invention

To confirm the possibility of carrying out the invention and achieving the technical result, a number of studies and experiments were carried out. The experimental results are presented below.

The rubber mixture was made on laboratory rolls LB 320 150/150 (manufactured by JSC "Plant named after Krasin") with a total load of 1200, according to the recipe below.

The components of the rubber mixture were, in particular, hydrogenated nitrile butadiene rubber (Therban from Arlanxeo), zinc oxide (GOST 208-84) - an accelerator activator, sulfur (Polsinex from Grupa Azoty) - a vulcanizing agent, stearic acid (GOST 6484- 84) - activator of vulcanization accelerators, filler dispersant, softener (plasticizer), dibenzthiazole disulfide (thiazole 2MBS) - vulcanization accelerator (GOST 7087-75), trioctyltrimellitate (TOTM plasticizer), polyvinyl alcohol (GOST 10779-78), organic vulcanizer.

As a spatially cross-linked polycondensation copolymer of polyhydric alcohols and acrylic acid, a copolymer of propylene glycol, erythrol and acrylic acid with a molecular weight of 30,000, polymerized in the presence of alkaline catalysts, produced by NOF Corporation (Japan) under the brand name MODIPER® G SERIES.

The ratios of the components of the proposed solution and the prototype are shown in Table 1:

Table 1

Compositions of rubber compounds

Proposed solution Prototype Nitrile butadiene rubber - 100,00 Hydrogenated Nitrile Butadiene Rubber 100,00 - Sulfur 0.20 0.50 Dibenzothiazyl disulfide 1.00 2.00 Hydrophilic resin - 80,00 TOTM softener 3.00 5.00 Zinc oxide 5.00 5.00 Stearic acid 5.00 2.00 Polyvinyl alcohol 20,00 - Carbon black Н 220 - 40,00 Mixture of diphenylmethane diisocyanate and polyethylene glycol - 40,00 Copolymer of polyhydric alcohols and acrylic acid 40,00 - Organic peroxide 7.00 -

Samples were vulcanized from the rubber compounds made on an LP 600kN vulcanization press (f. Montech). After curing for 24 hours, the samples were tested in accordance with GOST ISO 1817-2016 “Rubber and thermoplastic elastomers. Determination of resistance to liquids ". The test conditions are shown in Table 2.

table 2

Mineralization, g / l Temperature, ° С Conditions 1 (Fig. 1) 5.00 60,00 Conditions 2 (Fig. 2) 30,00 60,00 Conditions 3 (Fig. 3) 100,00 60,00

The test results are shown in FIG. 1-3

As can be seen from the graphs, the proposed solution surpasses the prototype in terms of the degree of swelling in highly mineralized environments and acts identically in low mineralization conditions. The proposed solution is somewhat inferior to the prototype in low-mineralized environments, but the degree of swelling of the proposed solution is sufficient to shut off the wellbore and maintain the pressure drop.

Additionally, tests were carried out to determine the resistance to the action of petroleum products. Diesel fuel (density 820 g / ml, pour point -7 ° C) was used as a model liquid.

The test results are shown in FIG. 4.

From the presented data, it can be seen that the proposed solution has greater resistance to the action of petroleum products than products made from a rubber compound according to the prototype.

In order to assess the effect of the content of active components, additional tests were additionally carried out, rubber mixtures were made according to the formulation shown in Table 1 with a change in the amount of active components. The test conditions are shown in Table 3.

Table 3

Content, phr Option 1 Option 2 Option 3 Option 4 Polyvinyl alcohol 30.0 25.0 10.0 0.0 Copolymer of polyhydric alcohols and acrylic acid 10.0 50.0 75.0 100.0

Samples were made according to the procedure described above.

The indicator "Change in mass after 500 h of exposure to liquid" was selected as an indicator. As model fluids, we used water with a salinity of 30 g / l, 100 g / l and diesel fuel similar to the test in FIG. 4. The results of the tests carried out are shown in table 4.

Table 4

Weight change after 500 h,% Option 1 Option 2 Option 3 Option 4 Water, 30 g / l 47 264 310 270 Water, 100 g / l 12 243 297 48 Diesel fuel eleven 0.2 0.1 15

As can be seen from the data shown in Table 4, the proposed solution shows the best result in terms of resistance to oil products and immunity to changes in mineralization, and also confirms that the claimed ratio of the components is optimal. This is most likely due to the emergence of percolation structures of polyvinyl alcohol copolymer due to van der Waals, hydrogen and chemical bonds.

Additionally, an attempt was made to manufacture rubber compounds containing polycondensation copolymers of polyhydric alcohols and acrylic acid of linear structure (spatially uncrosslinked). These copolymers are highly polar liquids. Apparently, the polarity of these liquids is much higher than the polarity of the base rubber, and therefore the manufacture of a rubber compound containing these two components is impossible from a technological point of view.

Similar tests were carried out with other quantitative ratios of components, which showed an improvement in properties compared to the prototype in the entire declared range of values.

Next, the rubber mixture was ground to a predetermined size, based on the principles shown in FIG. 5.

Industrial tests were carried out on an operating well. A crushed water-swellable rubber fraction of the above chemical composition was used as a plugging agent, and diesel fuel was used as a transporting fluid. The composition was pumped into the formation under pressure. After the injection of the plugging mixture into the formation, the well was closed while waiting for the swelling fraction to swell, the time of which in this well was approximately 37 hours. The degree of mineralization of the medium in the well was not established, since the effectiveness of the proposed mixture has already been confirmed in any conditions of mineralization.

Well studies have shown that its productivity has not been reduced. At the same time, the water cut was reduced by selectively shutting off the water inflow while maintaining oil access. Water was pushed out of the pores into the depth of the reservoir crossflow, blocking the water flow to the oil rim.

Claims (5)

1. A method of reducing the water cut of wells and eliminating in-situ and inter-reservoir water flows, in which a plugging mixture containing a finely dispersed water-swelling rubber fraction is injected into the formation under pressure, and after the plugging mixture is injected, the well is closed to await the swelling of the water-swelling fraction, the time of which is from 24 up to 48 h, characterized in that the size of the used particles of the fraction 60-70% of the average size of the fracture in the reservoir for plugging, a finely dispersed water-swellable rubber fraction obtained from a rubber mixture based on hydrogenated nitrile butadiene rubber (GBNKS ) containing polymer alcohol (s) in the amount of 10.00-30.00 wt.h. per 100 parts by weight HBNKS and spatially crosslinked polycondensation copolymer (s) of polyhydric alcohol (s) and acrylic acid in an amount of 25.00-100.00 parts by weight. per 100 parts by weight HBNKS, as well as a vulcanizing system and technological additives, while diesel fuel is used as a transporting fluid in the plugging mixture. 2. The method according to claim 1, characterized in that the rubber composition contains polyallyl and / or polyvinyl alcohol as the polymer alcohol (s). 3. The method according to claim 1 or 2, characterized in that a copolymer of propylene glycol, erythrol and acrylic acid with a molecular weight of 30,000 was used as a spatially crosslinked polycondensation copolymer of polyhydric alcohols and acrylic acid. 4. The method according to one of paragraphs. 1 or 2, characterized in that softeners, dispersants, fillers, antioxidants and colorants are used as processing aids. 5. The method according to claim 3, characterized in that softeners, dispersants, fillers, antioxidants and colorants are used as processing aids.

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