PSI - Issue 59

V. Grudz et al. / Procedia Structural Integrity 59 (2024) 757–762

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V. Grudz et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction Prospective planning of the development of the gas supply system, as a rule, is carried out in conditions of uncertainty of information. At the same time, it is necessary to apply a probabilistic approach to the structure of gas supply of gas resources, which basically uses the probabilistic characteristics of gas reserves by Muwei et al. (2018) and by Grudz et al. (2018). Along with information about reserves, the need for fuel is also uncertain and plays the role of a disturbing influence on the gas supply system. Forecasting the future demand for gas, its accounting during planning will bring the mathematical model closer to the real future conditions of fuel supply. The economic indicators, on the basis of which the plan for the long-term development of the gas supply system is evaluated, are also not strictly defined. The assessment of the inaccuracy of economic indicators can be reduced to the determination of the area of economic uncertainty of the structural scheme of gas supply. Finally, failures of elements of the gas supply system can affect the determination of flow rates, production volumes, volumes of injection (withdrawal) into underground storage facilities, the structure of gas distribution to consumers, etc. Given that it is difficult to take all factors into account at the same time, let's focus on the main factor – the uncertainty of information about gas reserves. Forecasting gas reserves is associated with some difficulties, especially when determining the reliability of forecasted reserves. This reliability is characterized by the coefficient of industrial discoveries (the share of productive structures, including internal ones), as well as the value of confirmation when converting promising reserves into industrial ones. The most reliable are the reserves of deposits with completed exploration and additional exploration. In the developed fields, reserves of categories C are found together with reserves of categories A and B , and the reliability of all three categories is sufficiently close. However, significant errors are possible in the calculations of reserves for category C 1 at newly discovered deposits (when reserves are assessed in an operational manner). All this must be taken into account when optimizing the structure of the gas supply system, so that in the event that gas reserves are not confirmed, it is possible to reorient the development of the gas supply system in accordance with the new situation. At the same time, it is necessary to provide for reserves. The amount of possible damage and methods of its compensation differ depending on the location of the considered gas-bearing area (field) in the gas supply system of the country as a whole by Su et al. (2020) and Molenda (1974). The least favorable sources of gas or other types of fuel can be used as a reserve. The main requirement for such reserves is the possibility of rapid development with relatively low capital investments and correspondingly increased operating costs. Taking into account the above, the task of optimizing the structure of the gas supply system in the conditions of random values of gas resources can be presented as follows by Kryzhanivskyi et al. (2006), by Mingfei et al. (2019) and by Su et al. (2019). There are n gas supply districts. The reserves of the i -th district are probabilistically determined and characterized by the mathematical expectation of i M and variance 2 i  . The resources of gas supply districts are used to meet the gas needs of economic districts. The need for gas j B for the j -th district is established as a result of fuel and energy management optimization. Reserves are provided for each district 1 t jr j r z k    to compensate for possible gas shortages associated with the probabilistic nature of production volumes (reserve 1 t jr r z   ) and with changes in reserves of gas producing districts (reserve j k ). Under the specified conditions, it is necessary to determine the optimal structure and technical characteristics of the gas supply system. 2. Research methodology The objective function of optimizing the structure of the gas supply system includes the component of costs for production, transport, as well as the overspending of funds due to the use of the national economic reserve in the j-th district (in case of gas shortage), and then the optimization task in the matrix formulation can be written as follows by Coelho and Pinho (2007). It is necessary to find the value of the functional