This article continues and extends the topic addressed at the last conference held in Moscow in 2011 – prospects of aluminum tubes in well construction in the Arctic1. In addition to well-known successful practices of using aluminum drill pipes, it highlights the results of manufacturing and application of tubing and casing, as well as risers made of structural aluminum alloy tube semis (SAA). Attention is also paid to the fact that though there are some obvious and proven SAA advantages in comparison with conventional tube semis, application of aluminum tubular products remains rather limited. This circumstance can be explained by certain conservatism of the engineering community that still relies on generally accepted dogmas of aluminum alloy deficiencies. These include low hardness contributing to increased wear of the surface in contact with rock or other material and limited corrosion resistance in some conditions, for example, with increased chloride content. Many experts believe that these negative circumstances prevail over such advantages as hydrogen sulfide corrosion resistance, stability of properties at low temperatures and, finally, a huge advantage in strength-to-weight ratio of the tubular structure – a freely suspended SAS string is almost twice as long as the string made of steel. Such approach, subject to a wide offering of advanced high-strength steel tubes and special alloy tubes resistant to hydrogen sulfide corrosion, helps to solve current problems in a traditional conservative way. However, increasingly difficult conditions of field development result in substantially higher costs of well drilling, completion and operation, and the Artic is one of the brightest examples of this tendency. This is precisely why the authors again offer to consider alternative "aluminum" solutions of the problems. The article describes the results of using advanced techniques for SAA surface treatment that enable to minimize low strength and wear problems. Among them are ultrasound treatment and different coatings. Also, the examples of solutions are given that enabled adaptation of SAA tubes for use in corrosive environment – 7" production casing installed in the well with more than 18 % hydrogen sulfide content in the produced oil; 22" offshore drilling riser operated at the water depth of more than 2,000 meters. Business success by enjoying SAA advantages is possible when a comprehensive multidisciplinary approach is used to design tubular or other structures for operations in extreme conditions whether these are drilling pipes, tubing or casing, risers or pipelines. The experience in other industries, for example, in shipbuilding, demonstrates the possibilities for solving great challenges by combining the efforts of experts in the sphere of materials science, metallurgy, machine building and structural design in this industry. In view of the tasks that are set, in particular, in arctic field development, building of specialized expert teams on the base on well-known research centers and scientific communities will allow making effective innovative decisions promptly and with the required reliability.

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This paper introduces the experience in development of drilling riser made of aluminum alloys (ADR). The first commercial ADR string was qualified for 2000 m operational depth. The submerged weight of the aluminum alloys for riser manufacturing is only 80-85% greater than the weight of water. The development of ADR was made possible by many years experience in operating of high-strength aluminum alloy drillpipes and different marine systems in Russia. Number of tests was conducted to study the alloy chosen for the manufacturing of the main riser tube. The samples were tested for static and fatigue strength in different media, impact elasticity and fracture toughness in seawater. The test agenda also involved metallographic examination, corrosion and wear resistance study. The full-scale ADR prototypes were tested for tensile strength, fatigue life and internal pressure. Strong consideration was given to assembling of the extruded tubes and flanges into a 75' long ADR joint. The finite-element analysis was used to provide a thorough strength evaluation of the riser and riser components. The experience in the ADR development shows that high-strength aluminum alloys and available manufacturing technology can be successfully applied in the development of ultra-deep water drilling risers with a variety of coupling designs, high-pressure riser, production risers and other offshore oil and gas systems. Introduction The world's hydrocarbon reserves are basically concentrated in the subsea areas. The depth of offshore exploration has been increasing in the past thirty years. The water depth of 1,000 m was overcome in an exploratory well drilled in 1975 but only in 1995 in a production well. Today the deepwater riser drilling record is set at a water depth of 2,956 m, while it is expected that the number of oil fields to be developed in ultra deep waters ranging from 1,500 to 3,000 m will increase. Currently, oil and gas production depths range from 1,000 to 1,500 m with the record depth of 7,208 ft (2,197 m). The qualified fields are found at 10,000 ft water depth and the production systems for 9,000 ft (2,743m) have been designed. [1, 2]. Increased depths required specific equipment for drilling, development and operation of fields. The current technologies provide the use of metal tubular structures (risers) for deepwater applications for all stages of field development. Deepwater risers have extraordinary stringent requirements for the strength, reliability and service life, that is why they are basically fabricated of steel tubes. However, the major limitation to the use of steel is its relatively high density or its low specific strength, i.e. the ratio of strength to the specific weight (syield/?) has the value being rather low as compared with other known structural materials. This characteristic places limitations on the potential riser extension. In the early of 1990s the researchers focused on titanium alloys and composites as structural materials in developing of the production risers design. Today the production prototypes of such risers are being tested [3].