The article deals with data on production of aluminum drilling pipes, as well as on their usage in drilling of deep wells in oil production. Properties of aluminum drilling pipes are considered.
Keywords: drilling pipes, drilling, bending, casing, specific gravity.
Nowadays the high operational reliability of drilling strings is of great importance when drilling horizontal wells and deep wells with large incline from vertical axe. The measures necessary to achieve this require reducing their stress-strain state and ensuring of trouble-free operation under extreme loads, as well as under high temperatures (Basovich et al. 2002).
Aluminum drilling pipes are currently made of three types of aluminum alloys, the most common of which are duralumin, high-strength corrosion resistant alloy, and special temperature resistant alloy. Structurally stable aluminum drilling pipes are produced with external-upset-ends and an equal-pass section with an internal-upset-ends (Balaba, 2018).
Justification of expediency of using of aluminum drilling pipes made in Russia, wide organization of production and introduction of aluminum drilling pipes are presented below (Aizuppe, 2007).
With the launch of their manufacturing in Russia, an increase in volume of drilling of oil and gas wells is observed, as well as the development of directional and offshore wells on the continental shelf began. Considerable experience of operation of aluminum drilling pipes with high technical and economic indicators helps to increase the using of aluminum pipes in practice of oil and gas production; they are used as tubing, drilling pipes for exploration drilling, as well as for intra-field communications (Basovich et al. 2003).
The greatest efficiency of using of aluminum drilling pipes is achieved during drilling of wells with the designed depth of more than 3,000 meters. The time taken to deepening of bottom hole decreases, while the time spent on down-hole operations increases with the growth of depth of well within the drilling cycle. Difficulties of elimination of complications and emergency operations increase as well. A row of important tasks arises during the development of wells for exploration and exploitation of oil and gas fields on the shelf. In some cases, drilling of elongated slanted wells from the coastal zone is more effective (Gelfgat et al. 2003).
For drilling of slanted, horizontal wells and wells with large incline from vertical axe, it would be more logical not to increase the requirements, but to decrease the rigidity of drilling strings. This can be achieved only by lowering of the modulus of elasticity of pipe material while maintaining the geometric parameters of pipes (Saushin, 2018).
At the same time, bending stresses arising in the string, as well as the pressure force of the drilling string on the wellbore and casing, and therefore the resistance force, are reduced proportionally (Kudinov, 2007).
Thus, it becomes possible to increase the design depth of wells in comparison to the ones drilled with the use of steel drilling strings under similar conditions.
Using of aluminum drilling pipes, which are made of special aluminum alloys and which have certain physical and mechanical properties due to the special material they made of, is especially actual nowadays (Aizuppe, 2007).
The main properties of aluminum drilling pipes are the following:
– low specific weight;
– high weight reduction in muds of different density;
– high specific strength;
– reduced value of modulus of elasticity;
– vibration damping;
– corrosion resistance;
– easy drilling ability.
These properties set the efficiency of using of aluminum drilling pipe as a part of drilling strings during wells boring (Serebryakov, 2017).
Low specific weight is the main parameter defined the weight of linear meter of pipe and the weight of a drilling string as a whole. Such property of aluminum drill pipes as weight reduction in a drilling mud contributes to the reduction of the weight of drilling strings and therefore helps to increase the effect of reducing their stress-strain state. Although the specific strength properties of aluminum drilling pipes are not so high as of steel ones, their using becomes more effective, as the maximum of strength goes to the loads formed by own weight of strings (Zaytseva, 2014).
Modules of longitudinal elasticity and shear define such parameters of physical and mechanical properties of the material as plasticity, the level of active stresses, and metallic resistance. Corrosion resistance defines the capacity of aluminum drilling pipes to operate stable within various corrosive environments with different pH values of drilling fluid.
One example is the usage of aluminum pipes in drilling mud to drill wells with a bottom hole super-inclined from the vertical axe. Drilling pipes with an increased flotation in the drilling mud contribute to reducing of weight of the drilling string. Drilling pipes made of high-strength aluminum alloy provides a buoyancy effect (Balandin, 2011).
Thus, it can be noted that aluminum drilling pipes should be used in drilling of wells under the presence of restrictions on the load-carrying capacity of the drilling rig. They should be also used in case of need of reduction of values of tensile loads, torque and complexity in bringing of the axial load on the bit while drilling horizontal wells through areas with an intense curvature of the borehole of a small radius, as well as with an increased corrosive aggressiveness of the mud, and especially in the presence of hydrogen sulfide and carbon dioxide in the mud.
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