Tubing string

FIELD: oil and gas industry.

SUBSTANCE: invention is referred to tubing string having silicate enamel coating at inner surface. At outer surface of the string ends there is a tool for tubes connection made as threaded sections. At that according to the invention silicate enamel coating at inner surface of tubes is modelled at substrate. Substrate is formed with area having removed layer of metal surface with depth from 60 mcm up to 80 mcm. At that substrate length exceeds length of threaded section at outer surface of the tube 2.1-2.3 times.

EFFECT: increase of the string service life.

1 cl, 1 dwg

 

The invention relates to the field of oil production, in particular the design of pump-compressor pipes (tubing), which are used for oil extraction from wells.

Recently there has been a significant deterioration of operating conditions of downhole equipment. The main factors for this are the high content in the reservoir of liquid water and gas, the high salinity of the reservoir fluid, the high content of hydrogen sulfide, the presence of mechanical impurities, salts and paraffin. High aggressiveness of the reservoir fluid leads to intense corrosion submersible equipment and tubing and, as a result of the exit tubing failure. The latter leads to a significant decrease in oil production.

One of the ways to solve this problem is to protect the inner surface of the tubing.

Known bimetallic tubing, formed by two layers: the outer - hot rolled pipe, the inner pipe with anti-corrosive properties, and between them is placed a sealing material to ensure its polymerization (Patent RF 2344266, IPC F16L 9/18, 2009). This tubing has high strength characteristics, but it is complicated to manufacture, requires the use of an inner tube with anti-corrosive properties, which increases its value, however, the security problem, the persons of the NGOs in the area of the connection tubing, this design isn't resolved.

Known tubing having on the inner surface of the body polyurethane coating, and on the outer surface of the ends - means for connecting pipes between the threaded sections (RF Patent 2362942, F16L 58/02, 2009, and the Patent of the Russian Federation 2395666, EV 17/01, F16L 58/02, 2010). Data tubing are protected its inner surface from the high aggressiveness of the reservoir fluid, but not reliable. This is because the permeability of polyurethane coatings for corrosive environments is quite high, which starts subcortical corrosion of metal pipes, disrupt the adhesion of the coating to the metal and causing it to peel. The polyurethane coating has a coefficient of thermal expansion (CTE)that is substantially different from the CTE of the metal. The latter even with a slight fluctuations in the temperature of the transported medium in the direction of its increase leads to cracking of the coating and damage the tubing.

In addition, the polyurethane coating is characterized by low abrasion resistance, which also reduces the service life of the tubing.

Known tubing having on the inner surface of the body diffusion coating, and on the outer surface of the ends - means for connecting pipes between the threaded sections. The protective coating contains, wt%: is elesa 6-15, zinc 84,1-93,4, copper 0,4-6, aluminum of 0.2-0.3. The coating is produced by aging in the diffusion of the mixture during 1,0-3,0 hours at a temperature of 440°C and subsequent cooling in air (RF Patent 2284368, F16L 58/08, 2006). This tubing is characterized by corrosion resistance of the inner surface, but since the surface diffusion coating is not smooth and has no gloss, there are formed various mineral deposits of calcium carbonate, various sulfates, wax deposits, waxes, etc. in Addition, the diffusion protective coating like polyurethane, has a different KTR with metal pipes. This circumstance results in short lifetime of tubing with a change in temperature of the transported medium to loss of coating adhesion to the metal and, consequently, the delamination of the coating from the metal and as a result, corrosion of pipes and malfunction. At temperatures the same operation more tubing 70-80°C, the corrosion resistance of the coating drops sharply, because under the action of mineral salts transported medium, it begins to dissolve. Moreover, in the composition of the diffusion coatings is dominated by zinc, copper and aluminum. These components are gentle enough for abrasive inclusions that are transported in the environment, so that the floor is unstable to abrasive wear. All of the above Zn is considerably shorten the life of this tubing.

The closest analogues of is tubing having on the inner surface of the body silicate enamel coating, and on the outer surface of the ends - means for connecting pipes between the threaded sections (RF Patent 31256, EV 17/01, 2003). This design ensures thanks silicate enamel coating good cross aggressive reservoir fluid due to good adhesion and a smooth surface coverage, as well as good protection from the inside of the pipe body due to the proximity of CTE coating and metal, except for the end sections of the NKR. Indeed, when cutting the threaded sections, which is carried out after deposition of silicate enamel coating, and subsequent naveriani couplings with a force of 50-100 kg/m due to the compressive effort is the chipping of the coating with the end sections of the pipe, appear rough unprotected areas, leading to corrosion and output tubing failure.

The present invention is to improve the construction of the tubing by forming a special substrate under the coating on the inner surface of the pipe, resulting in increased service life of the pipe.

The problem is solved by the fact that in the pump-compressor pipe having on the inner surface of the body silicate-amale the second floor, and on the outer surface of the ends - means for connecting pipes in the form of threaded sections, according to the invention, the end sections of the pipe silicate enamel coating of the inner surface of the pipe is formed on the substrate formed by the area with the removed layer of the metal surface a depth of 60 μm to 80 μm, the length of the substrate is greater than the length of the threaded section on the outer surface of the pipe 2.1-2.3 times.

Declare the parameters obtained experimentally. In the process of selection of parameters of the substrate, it was found that when the exit offer its limits in the direction of decreasing was observed chipping of the coating when cutting the threaded sections and navorachivaya couplings, and the increase in the parameters leads to an increase in unnecessary costs to the production tubing.

The difference of the pipe from the closest of the analogues is executing on the body of the pipe, special substrates, characterized by the specified parameters.

The technical result from the application of the proposed tubing compared to the closest analogy is the increase of life, and consequently the achievement of the possibility of increasing oil production.

This is because the proposed special underlay can increase the reliability of the coating on the end parts and thus virtually the ski to achieve equality of life of the coating and the pipe body by increasing the adhesion of the coating to the metal end sections by providing a reaction between the coating and the metal in the zone of the substrate.

The drawing shows the proposed design of the tubing.

The inventive design of the tubing includes a metal pipe 1, having on the inner surface of the body silicate enamel coating 2 and on the outer surface of the ends - means for connecting pipes in the form of threaded sections 3, at end sections of the pipe silicate enamel coating 2 internal pipe surface is formed on the substrate 4 formed by the area with the removed layer of the metal surface depth h from 60 μm to 80 μm, the length of the substrate is greater than the length of the threaded section on the outer surface of the pipe 2.1-2.3 times.

Examples of specific performance tubing.

At the ends of seamless hot rolled steel tubes. GS 73 mm diameter with a wall thickness of 5.5 mm strength group E (GOST R-2004) was carried out of the substrate by removing a layer of metal on the end parts and a depth of 60 μm to 80 μm with a length of the substrate greater than the length of the threaded section on the outer surface of the pipe 2.1-2.3 times. To remove a layer used axial grinding machine with a diameter abrasive disc 50 mm, After which the pipe was subjected to blasting treatment and subsequent deposition on the inner surface of the mixture of silicate enamels ECT-2 TU 3.17-04637622-172-95 and ECT-7 according to TU U 23371749-005-96. After drying and firing the obtained smooth, reflective surface coating. Strength n the kick coverage end sections amounted to more than 10 j (10 j - the maximum limit of measurement-1A (GOST 4765-73)), while the rest of the inner surface it was 3-3,8 j.

It was made 1000 pieces of pipe have been successfully cutting threaded sections and navertyvanija couplings with the necessary force, and chipping silicate enamel coating was not observed across the length and end parts. The term columns of these tubing without repair for more than two years.

Tubing with a diameter of 73 mm and a wall thickness of 5.5 mm are manufactured according to GOST R-2004 are representatives in sortimente range, so when determining the parameters specified in the claims, were used in these pipes.

The results of determination of the parameters is given in Table 1.

Table 1
№ p/pThe geometric dimensions of the pipes according to GOST (diameter, wall thickness, mmThe number of pipe piecesThe wall thickness of the pipe end sections, mcmThe wall thickness of the pipe after processing sifma bus, mcmThe thickness of the removed layer of metal, mcmThe length of the zone of the substrate with the removed metal layer, μmQuality is in the covering on the end parts after testing
173×5,5835175510272,4143,6Smooth, shiny, without cracks and chips
273×5,575469539574,3120Radial fractures in the transition zone of the captured layer on the rough surface
373×5,595366531452,6140,9Microcracks, point injections along the length of the zone
473×5,52153655269for 95.2160,2Smooth, shiny, without cracks and chips

Note

1. In the parameters table contains the averaged data.

2. The coating thickness was in the range of 260-320 μm (average of 290 μm), b is La similar for all options selection of the parameters of the substrate and provided rheological characteristics of the slurry.

In the process of selection of parameters of the substrate, it was found that when the exit offer its limits in the direction of decreasing was observed chipping of the coating when cutting the threaded sections and navorachivaya couplings, and the increase in the parameters leads to an increase in unnecessary costs to the production tubing.

The design of tubing made in accordance with the closest analogues due to corrosion of tubing on the end parts because of the radical chips, has failed already after 5-6 months.

Thus, the proposed design of the tubing is characterized by increased 4-5 times a lifetime.

Tubing, having on the inner surface of the silicate enamel coating, and on the outer surface of the ends - means for connecting pipes in the form of thread, characterized in that the end sections of the pipe silicate enamel coating of the inner surface of the pipe is formed on the substrate formed by the area with the removed layer of the metal surface a depth of 60 μm to 80 μm, the length of the substrate is greater than the length of the thread on the outer surface of the pipe 2.1-2.3 times.



 

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