RU2355740C1 - Grease used for sealing threaded connections - Google Patents

Abstract

FIELD: engineering industry.

SUBSTANCE: invention refers to operating greases, and namely to grease used for sealing threaded connections of pump-and-compressor pipes and casing pipes. Grease consists of fat base - industrial oil, "LKS-M" complex metallurgical lithium grease and graphite, as well as fine copper powder having small flake structure, with pure copper content of 99.1%-99.7%.

EFFECT: use of proposed grease provides uniform increase of torque moment from engagement of first turns of thread, which allows increasing the number of screwings/unscrewings by many times.

1 cl, 1 tbl, 4 ex

Description

Lubricant for sealing threaded joints refers to operational lubricants and can be used for screwing up threaded joints of tubing and casing pipes with threaded joints with metal-metal seal, including gas-tight joints of the VAM type and harmonized joints of VGAT, SECFR , SPMS2 for the operation of pipes in hydrogen sulfide-containing fields. The grease can also be used as a preservative.

One of the most important problems in the construction and operation of oil, gas and gas condensate wells is to ensure reliable tightness of the threaded joints of the columns (production, elevator, etc.), since the violation of the tightness often leads to serious complications: annular and annular gas showings, gas flows into overlying horizons, griffins, etc.

To ensure the tightness of threaded joints, the above types of threads (VAM and harmonized joints VGAT, SECFR, SPMS2) were developed, thus, the primary tasks of the lubricant used in this type of joint are:

- reduced wear of the threaded connection (weight loss of parts after repeated screwing-unscrewing);

- an increase in the resource of a threaded connection (an increase in the number of screwing-unscrewing threads without deterioration of operational and technical characteristics);

- protection of a threaded connection against corrosion;

- increase of turnaround time;

- uniform filling of all threads in order to prevent the formation of "dry" friction zones;

- with planned wear and aging of the threaded joint, compensation for the loss of tightness, laid down by the type of thread, due to its sealing ability;

- not to prevent the formation of gas-tight compounds and metal-metal compounds, but to ensure lubrication of the surfaces forming these compounds;

- not cause internal stress on the threads of the pipe and coupling due to the specific content of metal powders and their finely divided fractions.

In general, lubricants for pipe threaded joints, such as oil gauges, must meet the following international requirements of API 5A3, Recommended Practice for Lubricants for Casing, Tubing and Pipe Threads: and ISO 16738:

- easy to apply on the surface of the thread (brush, spatula);

- volatility in 24 hours at a temperature of 212 ° F (100 ° C) should not exceed 3.75% of the volume;

- The dropping point, which defines the upper limit for the use of lubricants, must be at least 300 ° F (149 ° C);

- volume of gas evolution (chemical stability at elevated temperature according to recommended practice API 5A3, Appendix F, should not exceed 20 cm ³ for 120 hours at 150 ° F (66 ° C);

- the maximum loss of oil release (an indicator of physical / chemical stability at elevated temperature relative to the base grease / liquid lubricant) should be 10% by volume when tested using a nickel mesh funnel for 24 hours at 212 ° F (100 ° C) ;

- penetration (permeability - characterizes the stability of a grease: how easy the lubricant is distributed over the thread and how long it remains on it; how long it does not delaminate during storage) at a temperature of 77 ° F (25 ° C) without stirring, should be in the range of 320 ... 380 units;

- the specific gravity range for a specific thread lubricant (an indicator of the constancy of production) should not differ by more than 5% from the average value set by the manufacturer (specific gravity, g / cm ³ , determined by the components used in the lubricant composition);

- weight loss during water leaching of thread lubricants (indicator of physical / chemical stability) should not exceed 5% for a duration of exposure of 2 hours at 66 ° C.

Threaded connections work under conditions of high variable pressures, as a rule, of corrosive media. Typically, greases made from mineral oils (types P-416, P-113, P-402) are washed out of the threaded joints, and the threaded joint is in direct contact with corrosive fluids. This invariably leads to a partial or even complete loss of their working capacity (depressurization, mechanical corrosion, fretting corrosion).

Known metal-clad lubricating composition (D. N. Garkunov. Tribotechnology. M.: Mechanical engineering. 1989, p.139, 144). Powders of copper or brass obtained by dispersing a liquid metal by chemical or electrochemical reduction, etc. are used as a cladding additive for lubricating oil or glycerin. The use of oil with copper or brass powder can reduce wear due to the formation of a metal film on the surface of friction pairs.

When applying this lubricating composition, a high coefficient of friction is observed under variable and alternating loads.

Also known "Lubricant for sealing threaded joints" according to the patent of the Russian Federation 2032712 from 03/27/90, publ. 04/10/95, bull. No. 10, containing wt.%: Calcium grease 7-15; graphite 30-40; water 0.5-8; mineral oil - the rest

To ensure the tightness of threaded connections, grease-based thread-sealing greases with fillers in the form of powders (graphite, vermiculite, zinc, lead, aluminum, etc.) are widely used.

The closest analogue in technical essence and the achieved effect is thread grease R-402, which incorporates a fat base, lead powder, zinc dust, copper powder and graphite, containing, wt.%: PSA - 29 lead and PCV zinc powders - 14, LiSt - 6, AlSt - 1, copper powder - 5, a mixture of industrial oil I-50A and polysiloxane liquid - 132-24 or PES-5 (1: 2) - the rest (Sinitsyn V.V. Plastic greases in the USSR. Handbook, Moscow: Chemistry, 1984, p. 164, pl. 51).

With a high content of metal powder, especially low dispersion, including lead, there is a high probability of deterioration of the properties of the lubricant. This is manifested in the uneven filling of the turns after make-up due to extrusion of the dispersion medium of the lubricant. This effect can be explained by the fact that when screwing up the threads, the lead powders introduced into the lubricant do not have time to evenly distribute in the inter-turn space. Additionally, internal stress and deformation of the threaded joint occur. In turn, these shortcomings of known lubricants can violate the technologically inherent properties of threaded joints, as well as lead to premature wear and failure.

Taking into account that some fat-based threaded compounds may have high sealing properties (this is confirmed by short-term bench tests), the main disadvantage of these and similar compounds is to be noted. It lies in the fact that the fat base of known compositions is exposed to a hydrocarbon medium, and the compositions themselves can gradually be squeezed out of threaded joints over time. This in turn leads to the occurrence of leaks and gas flows.

The likelihood of galling and jamming occurs at the initial stage of thread make-up, as there are high loads, and the time during which the make-up operation (engagement of the first turns) is not sufficient for the implementation of additives having a surface-active or chemically modified principle of action.

In this case, the lubricant is extruded from the contact surface and, accordingly, high thread wear, the appearance of scoring.

One of the main disadvantages of such a lubricant is the presence of deficient and toxic fillers in the composition of lead-containing fillers.

The main function of metal powders is to prevent seizure when connecting - disconnecting casing, drill and tubing. The consumption of such lubricants is high due to the high density and specific gravity. Each of these thread sealing greases has a certain limit of use and has both positive and negative properties.

The objective of the proposed technical solution is to create a lubricant that is convenient to use and provides thermal resistance during repeated screwing-unscrewing over a wide temperature range, corrosion inertness, sealing, preventing wear, scoring and seizing of threaded joints in corrosive hydrogen sulfide-containing environments.

The problem is solved due to the fact that the lubricant for sealing threaded joints containing a fat base and graphite is characterized in that it additionally contains lithium complex lubricant metallurgical LKS-M and copper in the form of powder having a finely scaly structure, high dispersion, with a clean content copper 99.1% -99.7%, with the following ratio of ingredients, wt.%: oil IGP-18 24-30; LKS-M 8-19; copper 8-10; GLS graphite rest.

With the introduction of copper in the form of a powder having a finely scaly structure, high dispersion with a pure copper content of 99.1% -99.7%, in conjunction with LKS-M, the following effect was discovered.

LKS-M provides the formation of an additional three-dimensional framework, in the matrix of which the components of the main substance (fat base) and fillers (graphite, zinc dust) are located. When copper powder containing finely dispersed particles of a scaly form with 99.1% -99.7% pure copper content is introduced into this system, the particles of copper powder are evenly distributed throughout the lubricant volume along the fibers of the LKS-M three-dimensional skeleton.

Moreover, the particles are located on the outer surface of the matrices when the remaining components are inside. Thus, the mechanical properties of the lubricant are improved, and due to the high content of pure copper, the anticorrosive effect is realized, however, in combination with LKS-M, the effect is more pronounced than when using these components separately.

It is especially important to note that the combined use of LKS-M and copper powder in the above ratios is the most rational both in terms of providing lubrication and protecting the threaded surface, as well as economic.

When components are introduced in the optimal ratio, copper flakes are located on the surface of the fibers of the LKS-M framework. Only the ratios indicated in the formula allow the following effect to be realized: when applying lubricant to the thread, copper flakes with LKS-M fibers are located along the sliding surface of the thread turns in an amount of 5-10 layers. This number of layers eliminates the likelihood of metal-metal contact with the formation of scoring, allows you to fully control the moment of makeup, as it occurs smoothly without jerking, and allows you to control the quality of assembly of the connection. Also, at the first turns of the thread there remains a sufficient amount of working lubricant, which can provide an anticorrosive effect and prevents the entry of aggressive media containing H ₂ S and CO ₂ , and their inhibition.

With a lower content of LKS-M with copper powder, seizures and seizures are likely at the initial stage of thread make-up, since there are high loads when the first turns are engaged. The formed three-dimensional skeleton is not enough for the entire volume of fat mass and filler to be evenly distributed in its matrix. This is accompanied by a heterogeneous structure, a chaotic arrangement of components, including copper powder, throughout the lubricant.

And a larger content is not only economically inexpedient, but can also lead to complete displacement of the fat base and complete destruction of the skeleton formed by LKS-M.

The combination of features is new and leads to a technical result consisting in the creation of a lubricant that is convenient to use and provides thermal resistance during repeated screwing-unscrewing over a wide temperature range, corrosion inertness, sealing, preventing wear, scuffing and seizing of threaded joints in corrosive hydrogen sulfide-containing environments due to the fact that it additionally contains lithium complex lubricant metallurgical LKS-M and copper in the form of powder having finely scaly with structure, high dispersion, with a pure copper content of 99.1% -99.7%.

With the claimed composition and ratio of ingredients, the proposed lubricant for sealing threaded connections has such a combination of properties that is not inherent in any of its ingredients or other known lubricants, which allows it to be used for the specified purpose in various climatic conditions, including conditions Far North and at the equator. Lubrication is made as follows.

With constant stirring, IGP-18 oil is introduced into the reactor in an amount of 24-30%, 8-19% of lithium complex lubricant metallurgical LKS-M is added. When dispersing, the formation and distribution of the three-dimensional framework of the LKS-M throughout the volume occurs. After the addition of graphite HFS during dispersion, the distribution of graphite within the framework occurs. Copper powder in the form of a fine-flaked powder in the amount of 8-10% is introduced and homogenized.

When copper powder containing finely dispersed particles from 0.045-0.1 mm is introduced into this system, flake-shaped with pure copper content of 99.1% -99.7%, the particles of copper powder are evenly distributed throughout the lubricant along the fibers of the three-dimensional framework LKS-M . Moreover, the particles are located on the outer surface of the matrices when the remaining components are inside.

The following effect was discovered.

LKS-M provides the formation of an additional three-dimensional skeleton, in the matrix of which the components of the main substance — the fat base and fillers — graphite are located, and with the optimum ratio, copper flakes are on the surface of the fibers of the LKS-M skeleton.

Only the ratios indicated in the formula allow the following effect to be realized: when applying lubricant to the thread, copper flakes with LKS-M fibers are located along the sliding surface of the thread turns in an amount of 5-10 layers. This number of layers eliminates the likelihood of metal-metal contact with the formation of scoring and allows you to fully control the moment of makeup, which occurs smoothly, without jerking, and allows you to control the build quality of the connection. Also, at the first turns of the thread there remains a sufficient amount of working lubricant, which can provide an anticorrosive effect and prevents the entry of aggressive media containing H ₂ S and CO ₂ and their inhibition.

It is especially important to note that the combined use of LKS-M and copper powder in the above ratios is the most rational both in terms of providing lubrication and protecting the threaded surface, as well as economic.

In this case, the mechanical properties of the lubricant are improved due to the high content of pure copper, the anticorrosive effect is realized.

Experimental batches of the claimed lubricant called RUS-Premium were delivered to the Seversky Pipe Plant in Noyabrsk, Chelyabinsk, Kamensk-Uralsky, and others.

As numerous observations and experimental studies have shown, this grease is ointment-like, uniform in composition, without impurities, consists of the main component, solid particles and special additives in proportions corresponding to the formulation.

The lubricant inherent in the claimed performance:

- penetration at 25 ° C without stirring, mm · 10 - 325

- dropping point, not lower - +190

- temperature range of application, ° С - -50 + 200

- allowable specific pressure during hydrotesting of at least 70 MPa;

- corrosive effects on metals (steel 40, 45, 50) were not detected;

- complete filling of the inter-turn threaded spaces, which contributes to the complete sealing of threaded joints;

- when screwing-unscrewing, there are no scuffing, seizing and welding of threaded joints.

The following are examples of lubricant properties at extreme component levels.

Example 1. The components are loaded into the reactor in the following ratios in%: industrial oil like IGP-18 24-30, grease like LKS-M 8, copper 8, graphite - the rest.

With the lowest content of LKS-M and copper powder, the following are observed. Due to the small amount of LKS-M in the total lubricant volume, the formation of a durable additional three-dimensional skeleton does not occur. The result is an uneven distribution of copper powder, a slight decrease in the mechanical properties of the lubricant. Wear also increases and there is a chance of scoring.

Due to the low content of copper powder, there is no uniform distribution of layers of flakes on the thread. High probability of scoring on the first turns of the thread. The anti-corrosion effect is very weak.

Example 2. The components are loaded into the reactor in the following proportions in%: industrial oil of the type IGP-18 24-30, grease of the type LKS-M 24, copper 10, graphite - the rest.

With the highest content of LKS-M and copper powder, the following are observed. Due to the large amount of LKS-M in the total lubricant volume, a strong, coarse additional three-dimensional skeleton is formed. The result is an uneven distribution of copper powder, significant hardening of the lubricant, and the formation of lumps. Difficulty in applying grease especially at low temperatures. Wear also increases and there is a chance of scoring.

Due to the high content of copper powder, there is no uniform distribution of layers of flakes on the thread. There is a high probability of stratification of the lubricant due to the deposition of copper during long-term storage or after transportation, which prevents the formation of a gas tight connection. A tension appears in the thread, which leads to the appearance of scoring on the first turns of the thread due to extrusion of the fat base with a metal filler.

Example 3. The components are loaded into the reactor in the following ratios in%: industrial oil of the type IGP-18 24-30, grease of the type LKS-M 8, copper 10, graphite - the rest.

With the lowest content of LKS-M and a high content of copper powder, the following are observed. Due to the small amount of LKS-M in the total lubricant volume, the formation of a durable additional three-dimensional skeleton does not occur. The result is an uneven distribution of copper powder, a slight decrease in the mechanical properties of the lubricant. Wear also increases and there is a chance of scoring.

Due to the high content of copper powder, there is no uniform distribution of layers of flakes on the thread. There is a high likelihood of stratification of the lubricant due to the deposition of copper during long-term storage or after transportation, the appearance of scoring on the first turns of the thread due to extrusion of the grease base with a metal filler, which prevents the formation of a gas tight connection, contributes to the appearance of tension in the thread.

Example 4. The components are loaded into the reactor in the following ratios in%: industrial oil of the type IGP-18 24-30, grease of the type LKS-M 24, copper 8, graphite - the rest.

With the highest content of LKS-M and the lowest content of copper powder, the following are observed. Due to the large amount of LKS-M in the total lubricant volume, a strong, coarse additional three-dimensional skeleton is formed. The result is an uneven distribution of copper powder, significant hardening of the lubricant, and the formation of lumps. Difficulty in applying grease especially at low temperatures. Wear also increases and there is a chance of scoring.

Due to the low content of copper powder, there is no uniform distribution of layers of flakes on the thread. High probability of scoring on the first turns of the thread. The anti-corrosion effect is very weak.

comparison table Indicators RUS-PREMIUM
TU 0254-008-540044229-2005 R-416
TU 301-04-020-92 P-402
TU 301-04-020-92 P-113
TU 301-04-020-92 Drop temperature, ° С not lower 190 130 130 125 Colloidal stability, pressure. oil,%, no more 7.0 7.0 7.0 7.0 Penetration at 250 ° C without stirring, mm · 10 ^-1 325 130-180 250-330 270-330 Corrosion on metals (steel 40, 45, 50) No effect Withstands Withstands Withstands Mass fraction of water,%, no more 0.1 0.1 Evaporation in 24 hours,% at 100 ° С 3,5 2.0 Application temperature range, ° С - 50 + 200 - 30 + 200 - 30 + 200 Appointment Fastening of threaded joints of tubing and casing pipes with threaded joints with metal-to-metal seal, including for gas tight joints of the VAM type and harmonized joints of VAGT, SEC FR, SPMS2 when operating pipes in hydrogen sulfide-containing fields. The grease can be used as a preservative. Sealing of threaded joints of drill pipe tool joints with working temperatures in the bottom from -30 to + 100 ° С and pressure up to 30 MPa. Sealing threaded joints of casing and tubing of any diameter, subjected to repeated screwing and working in wells with temperatures from - 40 to + 200 ° С. Sealing threaded joints of downhole motors, sub, chisels, drill pipe tool joints of deep and super deep wells. It is efficient from - 40 to + 200 ° С.

Claims (1)

A lubricant for sealing threaded joints containing a fat base - industrial oil, lithium complex lubricant metallurgical “LKS-M” and graphite, characterized in that it additionally contains highly dispersed copper powder having a finely scaly structure, with a pure copper content of 99.1-99, 7% in the following ratio of ingredients, wt.%:
industrial oil "IGP-18" 24-30 lithium complex lubricant metallurgical "LKS-M" 8-24 specified copper powder 8-10 graphite "GLS" rest