New Engineering Solutions in the Production of Laminated Composite Pipes for the Oil Industry
The oil industry of Russia currently needs innovative development projects intended for a radical improvement of the performance of material resources and a decrease of their consumption. One of the most promising trends in corrosion protection is the production and use of pipes made of laminated composite materials. There are several principal ways of producing them by metal forming processes. World practice shows that lining technology is reasonable for oil well tubing. Lining consists of simultaneous expansion of pipes made of dissimilar materials, which possess different properties. A pipe of the kind manages to combine high corrosion resistance and mechanical strength, and this makes its service life more than four times higher than that of pipes made by conventional methods. However, previous foreign experience of manufacturing and using these pipes prompts the necessity of improving some pipe-making processes. This paper discusses new engineering solutions in the production of lined pipes, as well as in situ testing results.
KeywordsOil well tubing Lining Lined pipes Bimetal pipes Oil production Field conditions Service life
Russia is one of the world leaders in oil production and the largest participant in the world energy market. Since the 2000s, oil production in Russia had been growing steadily before this growth slowed down some time ago. Note that the conditions for oil production in Russia have changed since the early 2000s. Thus, the development of new oil fields shifts to more and more unfavorable regions in terms of geological and climatic conditions, whereas oil extraction in regions discovered and developed 30–50 years ago is characterized by high water cut and intensive corrosive attack of downhole equipment. Due to the simultaneous effect of such factors as the presence of dissolved H2S and СO2 gases in the fluid to be extracted, abrasive wear and tensile stresses, pump-compressor pipes (PCP) suffer the hardest conditions. This is verified by the analysis of the reasons for the failure of downhole pumping equipment, which demonstrates that the contribution from the failure of PCP into malfunction is predominant, and it amounts to about 60%. The experience of operating corrosive wells shows that the service life of PCP in them sometimes does not exceed 4 months [1, 2, 3, 4, 5, 6, 7]. The operation of such a well is extremely difficult and involves considerable costs for the restoration of the efficiency of the pump-compressor column. The restoration costs for each well amount to about 350,000 RUB, annual emergency failures of pump-compressor columns, including those in oil industry, are numbered in thousands, and expenditures for failure elimination amount to hundreds of millions RUB.
To replace PCP that have exhausted their service life, the pipe industry of Russia annually provides oil companies with about 250,000 ton of new pipes. Medium-carbon manganese steels (30G2, 35G2S, etc.) and chromium-molybdenum steels (30KhMA) are more often used as pipe material; however, they are not corrosion resistant enough.
The analysis of the scientific and technical documentation for PCP [8, 9] shows that the Russian standards do not provide any sufficient requirements in terms of resistance to corrosive attack, and this, to some extent, restrains the improvement of the quality of pipe products. The world practice of oil production pays much attention to the resistance of PCP to attack by aggressive media. Thus, PCP made of various groups of stainless steels and corrosion-resistant alloys, namely, austenitic stainless steels, ferritic stainless steels, and martensitic stainless steels, has found a wide application under conditions of complicated oil extraction. A number of Russian and foreign studies deal with an efficient choice of steel or alloy grades and formulation of the matrix of choice for the pipe material depending on specific conditions of oil production, namely, on temperature and the content of the CO2 and H2S components in the well [1, 2, 3, 4, 5, 10, 11, 12].
21.2 Trends in Increasing the Durability of Pump-Compressor Pipes
The main trends in solving the problem of increasing the life of downhole pumping equipment  used by oil-producing companies are (1) corrosion inhibition by feeding a chemical reagent to the pump intake and to the hole clearance, (2) downhole treatment by periodic pumping of a chemical reagent, (3) use of corrosion protectors against electrochemical corrosion (sacrificial anodes), (4) introduction of PCP made of high-alloy steels in the anticorrosion version, and (5) application of special anticorrosion coatings onto the inner surface of PCP. These measures require extra costs. Another line of increasing the life of PCP is the application of repair technologies, service companies having been created for this purpose. The current repair technology consists of cleaning the inner surface of pipes from deposition and cutting out defective areas; however, the lifetime of repaired pipes is reduced due to the retention of defects and corrosion pits intensifying the processes of corrosion in the second stage of pipe operation. The performance, reliability, and lifetime of pipes can be radically increased through making them from laminated composite materials. In the world practice, these materials have found application in many industries. Laminated composite pipes can be produced in several principally different ways, namely, longitudinal welding of bimetal sheets, producing pipes by simultaneous expansion, liquid diffusion welding along interfaces, explosion welding, centrifugal casting, and hot isostatic extrusion [14, 15, 16, 17, 18]. In oil and gas industry, there is a positive experience of testing experimental-industrial batches of laminated composite pipes in oil wells in the Netherlands, the USA, Indonesia, New Zealand, Norway, the UK, the Philippines, Malaysia, Japan, and Russia. Among the known methods of manufacturing pipes from laminated composite materials, lining should be distinguished. Lining consists of simultaneous expansion of a pipe made of conventional carbon or low-alloy steel (external shell) and a thin-wall pipe made of corrosion-resistant high-alloy steel (internal shell), the pipes being joined due to compressive residual stresses on the interlayer boundary .
21.3 Developing a Technology for Producing Lined Pump-Compressor Pipes
Incoming inspection and preparatory operations
Calibration of the inner surface of the PCP by expansion on a mandrel
Preparation of the PCP ends and the liner for expansion
Installation of the PCP and the liner with a sealant applied to its outer surface
Simultaneous expansion of the PCP and liner on a mandrel
Polymerization of sealant of the lined pipe
The internal thin-wall liner made of high-alloy steel is responsible for corrosion resistance, the external shell (pump compressor pipe) being responsible for structural strength.
Low content of harmful impurities in the liner metal contacting with the aggressive environment in a well.
Higher plasticity of the liner metal than that of the seamless pump-compressor pipe, which makes lined pipes reparable, reliable, and durable.
The smoothness of the inner surface of the liner Ra of 0.5–0.6 μm.
The presence of a sealant on the interlayer boundary, which prevents electrochemical corrosion between the shells made of dissimilar metals and increases the reliability of adhesion between them.
Feasibility of heat treatment under different conditions for the internal and external shells, depending on the purpose (ensuring good mechanical property for the external shell and high corrosion resistance for the internal one).
The proposed technology of manufacturing lined corrosion-resistant pipes is pioneered in the Russian and world practice of pipe production, and this is validated by the analytical survey of the literature discussing only some theoretical results concerning the process of manufacturing lined pipes. Therefore it is necessary to develop requirements for billets and performing individual technological operations of making lined pipes. To produce high-quality lined pump-compressor pipes, it is required that (1) reliable adhesion between the liner and the pump-compressor pipes be ensured and (2) the lined pipes meet the requirements of the Russian and world standards in terms of size precision , the level of mechanical properties, and corrosion resistance.
In view of the features of expanding laminated composite materials on a mandrel, a mandrel design has been developed, and the dimensions of the mandrel ensuring the adhesion between the initial round billets have been calculated.
21.4 Testing Lined Pump-Compressor Pipes Under Field Conditions
Pilot models of a composite pipe were made from six pieces of worn PCP, 1700 to 1900 mm long. Before lining, on three of the six worn PCP with more than 1.9 mm deep defects, 3 mm diameter through holes were additionally made in the midsection (four on each). The worn PCP was lined by expansion with 47 × 1.5 mm electrically welded pipes made of steel 10. The interlayer clearances and thread connections of the fabricated pipe were sealed with a sealant. The pieces were joined on the thread by sockets. The fabricated bimetal pipes were tested on a “Brocker” hydraulic press in pipe-making department No 4 of the Pervouralskiy Novotrubniy Zavod JSC (Pervouralsk New Pipe Plant). The hydraulic pressure was changed in six steps from 14.7 to 56.9 MPa with a 60 s hold. The test results have demonstrated that the fabricated 9500 mm long bimetal pipe withstands a test under pressure exceeding by 13% the standard value according to the Russian standard GOST R 52203–2004 for conventionally made PCP of the D strength group. No depressurization of the interlayer clearances and thread connections with complete preservation of the carrying capacity along the entire bimetal pipe, including the portions with 3 mm diameter through holes drilled in body of the PCP, is observed.
Pilot batches of bimetal PCP made by lining from worn 73 × 5.5 mm pipes with 1.9–3.4 mm deep defects have been tested under field conditions on four facilities the “Tatneft” JSC. The PCP service conditions on all the facilities are estimated as severe. Thin-wall electrically welded liner pipes were made of steel 22GYu according to the Russian standard specifications TU 1373-021-05757850-07. The lined PCP from the pilot batch have been operated since March 4, 2009 (for more than 2000 days), and there is no criticism about the quality and efficiency of repaired pipes. Regular inspection of the quality of PCP by visual examination and hydrotesting, both involving pipe lifting from the wells, has not revealed any quality faults. The inspected pipes continue being operated in the normal mode.
The creation of the process of producing lined PCP and bringing it to commercial level is aimed at increasing the engineering and economic performance of oil production in Russia and multiply decreasing power inputs for the maintenance and operation of oil wells, and this corresponds to the national and global scientific and technological priorities, the state program “Energy Efficiency and Energy Sector Development” approved by Russian Federation Government Regulation No 321 dated April 15, 2014, the priority lines of research, technology and engineering, and the list of critical technologies approved by RF Presidential Edict No 899 dated July 7, 2011.
The cost-effectiveness of the production and consumption of lined pump-compressor pipes results from lower maintenance costs of pump-compressor columns due to longer service life of lined PCP than that of new pipes. The restoration of PCP by lining offers a more than four times increase in durability and a multiple decrease in the expenditure of material and financial resources for buying new pipes (instead of lined), repairing, and maintenance of PCP and oil wells.
The study was made within the basic part of the state job in the field of scientific activity No. 11.9538.2017/8.9; it was supported by Act 211 of the Government of the Russian Federation (agreement No. 02.A03.21.0006).
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