RU2765950C1 - Rubber mixture for making oil-swelling products - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: invention relates to the industry of rubber products for the oil and gas industry and can be used for production of oil-swelling packers or other products for isolation of formations by increasing volume at contact with oil-containing liquid or associated petroleum gas. Rubber mixture based on a synthetic ethylene-propylene-diene polymer (EPDM), into which polyethylene with molecular weight Mn 800–1,500 is added in amount of 5–30 pts. wt. per 100 pts. wt. of EPDM rubber. Rubber mixture may contain fillers, softeners, plasticizers, antiaging agents (antioxidants, antiozonants), vulcanizing systems, anti-reversion agents, etc.EFFECT: obtaining articles having a high degree of swelling in an oil medium, while having a relatively low swelling rate.4 cl, 1 dwg, 3 tbl

Description

Technical field

The invention relates to the field of rubber products (RTI) and rubber products for the oil industry, in particular, and can be used for the production of oil-swellable packers used in oil production and well development. Also, this invention can be used to create other products for isolating formations by increasing the volume in contact with an oily liquid or associated petroleum gas. In addition, this invention can be applied to the repair of oil transportation systems and related equipment.

State of the art

In many applications, swellable packers or casing packers can provide a safer and easier means of isolating formations than cementing and perforating. Swellable packers are widely used and have a tangible positive effect in the following operations carried out in the fields: reservoir isolation, flow diversion, well induction, wells with a computer production control system, separate production from several horizons, optimization of the use of cementing, gravel environment, hydraulic fracturing , hydro- and vapor barrier of zones in the well, expanding check valve, well completion, etc.

The operating principle of a swellable packer and other swellable products is as follows. When a swellable packer or product made from a special elastomer comes in contact with downhole fluids, it swells and plugs the annulus in any open or cased hole. The absence of moving parts in the structure allows installation without tools running through the drill pipe to actuate the structure and eliminates the possibility of failure. The elastomeric compounds from which swellable packers are made react to wellbore fluids, drilling mud, well completion fluids and are able to increase in volume relative to the volume occupied when running into the well. The use of open hole elastomeric swellable packers in addition to gravel packs isolates the lateral sections from potential water intrusion.

The long-term integrity of the well is directly dependent on the cement coating of the pipeline. Failure of the cement coating can result in loss of productivity, lower well pressure and early water production. Even a good quality cement coating can be damaged by drilling and/or fluctuations in pressure and temperature during production. To restore it, an expensive overhaul of the well is required. Swellable packers are used to reduce stresses in the elastomer/cement contact zone, thus preventing failure of the cement layer. When cracks are formed in the cement layer of the annulus, the elastomer of the swellable packer interacts with fluids, which swells and clogs their path of movement. By installing swellable packers in hazardous areas, long-term ring isolation of the pipeline is guaranteed.

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

For example, patent source WO 03008756, publication date 01/30/2003, describes a method in which a rubber cylinder is placed in the well annulus, which is able to swell when in contact with water or oil, thereby cutting off the flow of water into productive formations.

Also from the patent document WO 2014062391 A1, publication date 04/24/2014, a swelling packer with a controlled swelling rate is known, which swells due to the water-absorbing additives included in the composition, namely, a copolymer of tetrafluoroethylene and propylene, a graft copolymer of starch and polyacrylate acid, a graft copolymer of polyvinyl alcohol and cyclic acid anhydride, isobutylene-maleic anhydride copolymer, vinyl acetate-acrylate copolymer, polyethylene oxide polymer, poly(ethylene oxide) poly(acrylic acid) graft polymer, carboxymethyl cellulose type polymer, starch-polyacrylonitrile graft copolymer, polymethacrylate, polyacrylamide, acrylamide-acrylic acid copolymer , poly(2-hydroxyethyl methacrylate), poly(2-hydroxypropyl methacrylate), insoluble acrylic polymer, high swelling clay mineral, sodium bentonite, sodium bentonite with montmorillonite as the main component, calcium bentonite, their derivatives or their combination inations.

Patent document RU 2685350 C1, publication date 04/17/2019, describes a water-and-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 familiar in technology RTI.

Patent document RU 2686202 C1, publication date 04/24/2019, describes a rubber compound that contains nitrile butadiene rubber with a NAC content of 17-20%, SKD butadiene rubber, sevilen 11808-340, sulfur, 2,2'-dibenzthiazole disulfide, guanide F, zinc white, stearic acid, acetonanil N, carbon black P 514, rosil 175, talc, finely ground mineral powder from shungite, rosin, Oksipan needle-punched cloth, polyacrylamide AK 639, Kometa-R reagent and sodium salt of polyacrylic acid PAN-1.

Known oil-swellable packer, described in the application CN 101824973 A, publication date 09/08/2010, made from a rubber compound containing styrene-butadiene rubber, acrylonitrile-butadiene rubber, neoprene rubber, carbon black, zinc oxide, stearic acid, stabilizing agent, inorganic filler , material with high oil absorption.

There is also a rubber compound for sealing elements described in patent RU 2688512 C1, publication date 05/21/2019, which contains nitrile butadiene rubber with an acrylic acid nitrile content of 17-20%, SKI-3 isoprene rubber, sevilen 11808-340, N, N'-dithiodimorpholine, thiuram D, sulfenamide C, zinc white, stearic acid, N-nitrosodiphenylamine, carbon black T 900, rosil 175, talc, chalk, petroleum polymer resin Sibplast.

Patent RU 2615520 C1, publication date 04/05/2017, describes an oil-absorbing rubber compound based on a combination of nitrile-butadiene rubber grade BNKS-40AMN and synthetic isoprene grade SKI-3, as well as additionally containing a vulcanizing agent - sulfur, vulcanization accelerators - captax and altax , vulcanization activator - zinc white, antioxidant - naphtham-2, fillers - carbon black P 324, rosil-175 and zinc stearate, plasticizers - norman-346 and rosin.

The closest analogue of the proposed solution is a composite oil-swellable material described in patent RU 2625108 C1, published on 07/11/2017, characterized in that it includes nitrile rubber with an acrylic acid nitrile content of 17-20%, isoprene rubber SKI-3, sulfur, sulfenamide C, N, N'-dithiodimorpholine, thiuram D, antiscorching "ZPR", zinc oxide, zinc stearate, stearic acid, naphtham-2, carbon black H 220, taurite TS-D, resin "Shinplast", oxanol TsS-100, dibutyl phthalate, industrial oil I-12A, trans-polynorbornene. This decision was taken as a prototype.

The disadvantages of the prototype include: the complexity of the technology (the need for preliminary "soaking" of trans-polynorbornene and the multicomponent composition), the need for additional equipment, as well as the insufficient degree of swelling at a fairly high speed.

List of drawings

The figure 1 presents a graph showing the dependence of the change in sample volume from the exposure time in the environment.

Disclosure of invention

The aim of the proposed solution is to overcome the shortcomings of the prior art and to develop a rubber compound having improved swelling properties and working effectively in an oil-in-water emulsion environment, preferably used for the manufacture of packers.

The technical result of the invention consists in the development of a rubber compound from which products are made that have the most effective combination of swelling properties, namely, a slower volume change in oil-containing media with simultaneous increased swelling in such media. Also, the mixture manufacturing technology is simpler, faster and cheaper due to the fact that the component composition is much simpler and more accessible, and the preparation of the mixture requires correspondingly less time and operations.

With regard to packers and other swellable products, these improved mechanical properties have a positive effect on safety when lowering the equipment, since the packer (or product) swells more slowly in an oily environment. In addition, the proposed solution has significantly improved swelling properties in the oil environment, which ensures greater reliability and performance of the packer in these conditions.

The technical result is achieved by providing a rubber mixture based on a synthetic ethylene-propylene (diene) polymer (hereinafter referred to as EPDM), while polyethylene with a molecular weight (Mn) 800-1500 is additionally introduced into the composition in an amount of 5 - 30 wt.h . per 100 wt.h. rubber EPDM. Such polyethylene oligomers can be both liquids and solid, plastic substances under normal conditions.

In addition to the above components, the rubber compound may include ingredients that are commonly used in the rubber industry: fillers, softeners, plasticizers, dispersants, anti-aging agents (antioxidants, anti-ozonants), vulcanizing systems, anti-scorching agents, anti-reversing agents, etc. Additional ingredients are selected based on the specific conditions of operation and manufacture of the product, 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 product from a given rubber compound and may vary within specified limits to achieve the required properties.

For example, the amount of polyethylene with a molecular weight (Mn) of 800-1500 may be 6, 7, 10, 15, 20, 25 mass. per 100 wt.h. SKEPT. However, the quantitative ratio of the component is not limited only to the given values and may include any intermediate values included in the initially specified intervals.

At the same time, the choice of the quantitative content of polyethylene is due to the achievement of optimal physical and mechanical properties of products. So, when the content is in concentrations above 30 wt.h., the degree of swelling of the product and the strength characteristics of rubber unexpectedly drop, which is unacceptable in this application. When the concentration of polyethylene is below the minimum allowable level (5 wt.h.), the effect of its introduction is not satisfactory and is hardly noticeable.

At the same time, the use of low molecular weight polyethylene (with a molecular weight of 800-1500) was due to the fact that the “classic” polyethylene polymer swells extremely limitedly in the environment of petroleum products at temperatures below 80 ° C, and this swelling is so insignificant that polyethylene can be used as oil pipelines (see Yu, K.; Morozov, E.; Ashraf, MA; Shankar, K. A review of the design and analysis of reinforced thermoplastic pipes for offshore applications. J. Reinf. Plast. Compos. 2017, 36, pp. 1514-1530). As for polyethylene with a molecular weight of less than 800, its processing is difficult from a technological point of view, and sometimes impossible, due to the instability of properties and state of aggregation. As is known, the properties of oligomers strongly depend on the change in the number of repeating units in the molecule. From the moment when the chemical properties cease to change with increasing chain length, the substance is called a polymer. It was experimentally found that polyethylene with a molecular weight of 800-1500, when used to produce rubber products, has the best set of swelling and workability properties, as well as the stability of properties in oil-containing media. These polymers are essentially polyethylene waxes.

Ethylene propylene diene rubbers (EPDM) are synthetic elastomers. They are ternary copolymers with 1-2 mol. % diene, for example 2-ethylidene-5-norbornene, dicyclopentadiene. They dissolve in many hydrocarbons and their chlorine derivatives. EPDM is produced by copolymerization of ethylene with propylene and a diene on a Ziegler-Natta catalyst in a solution or excess of polypropylene. Not plasticized. Vulcanized with sulfur, phenol-formaldehyde resins. EPDM have excellent weather and ozone resistance, high thermal, oil and wear resistance, but also high air permeability, are stable in aggressive environments, have good dielectric properties; tensile strength 20-28 MPa, relative elongation 400-600%, rebound elasticity 40-52%.

The functional additives used in the invention, such as fillers, emollients, plasticizers, anti-aging agents (antioxidants, antiozonants), dispersants, curing systems, anti-scorching agents, anti-reversing agents, etc., are well known to specialists and do not require special disclosure. Suitable additives for use are disclosed, in particular, in the book "Functional fillers for plastics" Ed. Marino Xanthos, 2010

As for the mechanism for achieving a 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 low molecular weight polyethylene. This effect is most likely associated with the formation of a spatial structure of the polymer in the composite.

It should also be noted that the manufacture of oil-swellable packers is not the only area of application of the proposed rubber compound and it can be used in any area that requires the use of materials with oil- or oil-swellable properties. In particular, this invention can be applied to the repair of oil transportation systems and related equipment.

Implementation of the invention

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

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

Synthetic rubber ethylene-propylene-norbornene (Vistalon by ExxonMobil), zinc oxide (GOST 208-84) - accelerator activator, sulfur (Polsinex by Grupa Azoty) - vulcanizing agent, stearic acid (GOST 6484-84) were used as components of the rubber mixture. - activator of vulcanization accelerators, dispersant of fillers, softener (plasticizer), organic peroxide - vulcanizer, carbon black H 220 - reinforcing filler, industrial oil I-12A - plasticizer, low molecular weight polyethylene Marcus M300 with a molecular weight of approximately 900-1100 (Marcus Oil & Chemical ).

The ratio of the components of the proposed solution and the prototype are shown in table 1:

Table 1
Compositions of rubber compounds Suggested Solution Prototype Ethylene Propylene Diene Rubber Vistalon 100.00 - Nitrile butadiene rubber with 17-20% acrylic acid nitrile - 50.00 Isoprene rubber SKI-3 - 50.00 Sulfur 0.20 0.50 Sulfenamide C - 2.00 N,N'-dithiomorpholine - 2.00 Tiuram D - 2.00 Antiscorching "ZPR" 0.50 zinc oxide 5.00 3.00 zinc stearate - 5.00 Stearic acid 5.00 2.00 Naftam 2 - 2.00 Technical carbon H 220 10.00 30.00 Taurit TS-D - 15.00 Resin "Shinplast" - 5.00 Oksanol TsS-100 - 2.00 dibutyl phthalate - 3.00 Industrial oil I-12A 3.00 24.00 trans-polynorbornene - 6.00 Polyethylene Marcus M300 25.00 - organic peroxide 7.00 -

Samples were vulcanized from the manufactured rubber compounds on the LP 600kN vulcanization press (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. Oil with a temperature of 60-70°C is used as a test medium.

table 2 Test results Suggested Solution Prototype Volume change after 12 hours, % 35 98 Volume change after 24 hours, % 55 122 Volume change after 48 hours, % 80 137 Volume change after 72 hours, % 101 152 Change in volume after 96 hours, % 125 167 Volume change after 120 hours, % 142 172 Volume change after 144 hours, % 160 178 Volume change after 168 hours, % 189 182 Volume change after 336 hours, % 270 185 Volume change after 504 hours, % 320 186

The test results are graphically depicted in figure 1.

It can be seen from the image that the proposed solution makes it possible to achieve high degrees of swelling, which predicts the possibility of using the invention under conditions of high differential pressures.

The influence of the amount of low molecular weight polyethylene (with a molecular weight of 800-1500) on the swelling of the composition was also experimentally studied, since it is known that “classical” polyethylene swells extremely limitedly in the environment of petroleum products at temperatures below 80°C.

As an indicator for comparison, the values of "Change in mass after 500 hours of stay in the test liquid" were used. The test conditions are similar to those of figure 1. The formulation of the elastomeric material is similar to table 1, except for varying the amount of the "Marcus M300 Polyethylene" component:

The test results are presented in table 3

Table 3 Change in sample weight after 500 hours of exposure to the test liquid (petroleum) 1 option Option 2 3 option 4 option 5 option 6 option The content of PE, wt.h. 0 10 twenty thirty 45 60 Δm 500 h, % 170 300 337 370 220 150

As can be seen from the data in the table, the change in mass is disproportionate to the content of polyethylene, and has an extreme character. The increase in the degree of swelling with the introduction of polyethylene cannot be explained from the point of view of the additivity principle, since as mentioned above, polyethylene does not have sufficient swelling. We assume that the low molecular weight of polyethylene prevents its crystallization, and it forms amorphous regions in the elastomeric material, which are more susceptible to the migration of oil products into the material. A decrease in the swelling mass with a further increase in the content of polyethylene can be associated with the fact that a large proportion of amorphous regions facilitates the migration of oil products both into and out of the composite.

Polyethylene with even lower molecular weight is too plastic (almost liquid), it is unstable, difficult to process and poorly molded, and therefore the use of such oligomers in this invention is not possible.

These tests allow us to conclude that the use of low molecular weight polyethylene (with a molecular weight of 800-1500) in the amount of 5-30 mass.h. together with EPDM rubber to produce oil-swellable products with a high degree of swelling in an oil and oil environment, while having a relatively low swelling rate.

The rubber compound is easy to prepare, the recipe is relatively simple.

Claims (4)

1. Rubber mixture for the manufacture of oil-swellable rubber products based on synthetic ethylene-propylene-diene rubber (EPDM), containing a vulcanizing system and technological additives, characterized in that polyethylene with a molecular weight of Mn 800-1500 is additionally introduced into the mixture in an amount of 5- 30 wt.h. per 100 wt.h. rubber EPDM. 2. The rubber compound according to claim 1, characterized in that the rubber product is a packer. 3. A rubber compound according to claim 1 or 2, characterized in that Marcus M300 polyethylene with a molecular weight Mn of about 900-1100 is used. 4. The rubber compound according to one of paragraphs. 1-3, characterized in that fillers, softeners, plasticizers, dispersants, antioxidants - antioxidants, antiozonants, antiscorching agents, antireversing agents and dyes are used as processing aids.

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