Improving the tools and mathematical methods to diversify the portfolio of oil and gas assets in the face of limited investment, high market volatility, increasing risks and uncertainties at the current level of technology development is a very urgent task. In order to form an effective investment portfolio, the authors proposed asset diversification using cluster analysis, which implies grouping sample objects according to a set of specific features. The method under consideration involves five stages of asset valuation in order to consider those assets in a three-dimensional space, taking into account the specifics of the oil and gas business, including determination of individual asset trajectory, performing spatial approximation, calculating the clustering coefficient, ranking the resulting pairs, and directly solving the portfolio formation optimization problem. This paper provides a reasonable set of metrics for diversification of the investment portfolio based on cluster analysis: main criterion - ∆PV, additional criteria - ∆Production, ∆OPEX/toe, ∆CAPEX/toe, characterized geological, environmental, social and economic aspects. Thus, the proposed methodology provides an opportunity to identify the most attractive investment projects, thereby allowing large oil and gas companies to diversify their business with minimal risk and maximum return on invested capital.

Influence of grain size on the mechanical and performance properties of metallic materials is analyzed. Methods for grain refining- equal channel angular extrusion (ECAE) is reviewed in the article. The method of equal channel angular pressing is described. Experimental data on the effect of sub-micron structures on hardness after ECAE samples of copper, aluminum and steel used in the manufacture of mining cutters (35HGSA) is presented.

The article presents an approach to determining the electric drive’s operability based on an asynchronous motor with a short-circuited rotor and a two-link frequency converter. Mathematical description of the frequency-controlled electric drive is performed, in particular, selection of criteria taking into account an electric and mechanical part. The harmonic current distortion coefficient as a component of the power coefficient is used for the determination of the energy criterion. The mechanical criterion is the coefficient of the electromagnetic moment pulsation, on the value of which the conjugated equipment depends. The operability field is represented as a function of three variables: (а) rotor speed, (b) current harmonic distortion coefficient, and (c) electromagnetic moment pulsation coefficient. The obtained surface makes it possible to determine the actual state of the electric drive and to estimate the reserve of operability, which allows reducing the operating costs in terms of repair and maintenance.