PSI - Issue 36

366 Teodoziia Yatsyshyn et al. / Procedia Structural Integrity 36 (2022) 362–369 Teodoziia Yatsyshyn, Myroslava Polutrenko, Lubomyr Poberezhny et al./ Structural Integrity Procedia 00 (2021) 000 – 000 5 complex system, it is influenced and manifested by new risk factors, properties and indicators of a priori known risk factors ρq ∈ q M0 change over time. This causes a quantitative and qualitative change in set of risk factors.

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where , - the set of risk factors and the set of risk situations, respectively, at the time predicted time of operation of a complex system. 3. Investigation of the causes of ecologically dangerous situations at the facilities of the oil and gas complex The analysis calls for the study of the most environmentally dangerous situations at the oil and gas complex and for establishing the causes of their occurrence. The facilities of the oil and gas complex are located near natural recreational areas of national importance, which creates a high risk of man-made disturbance of valuable areas. Thus effects from technogenic action of objects of an oil and gas complex can acquire cross-border value. This confirms the need to use an individual approach to assessing the environmental risk of different regions, taking into account the characteristics of each to create environmentally friendly working conditions in the process of technological operations at the facilities of the oil and gas industry. The process of well construction, in particular exploratory drilling and opening of productive strata carries an increased environmental risk because it may be accompanied by the emergence of gas oil and water manifestations (GOWM) and open fountains (OF) (Yatsyshyn et al. (2019)). In Chuvilov's (2002) researches it is noted that probability of occurrence of accident with emission of formation fluid at drilling of an exploratory well is estimated by size of 9-10 -4 st./year. Some deposits may contain aggressive components (hydrogen sulfide, carbon dioxide), a mixture of which is dangerous to the population and the environment (Chudyk et al. (2019)). In the presence of such components, the need to calculate the risks is present at all stages of the life cycle of wells, because in environment like that, corrosion processes are accelerated (Poberezhny et al. (2020)). Also, all wells are characterized by their aging, violation of the integrity of the cement stone behind the columns (Khaustov et al. (2008), Chudyk et al. (2021)). Forecasting situations of accidents and their prevention is impossible without assessing the factors of accidents. Therefore, the analysis of the causes of GOWM and OF in wells that were in different conditions and at different stages of the life cycle according to the materials of Kuzmenko (2006). 100 wells were selected for the study. The main factors (Table 3) that preceded the occurrence of accidents and according to various sources could be the causes of GOWM and OF are grouped. Often there was a combination of several factors in one well, among which the key, in most cases, was the organizational (human) factor. Therefore, the given percentages reflect this picture: the sum of the shares of factors from the total number exceeds 100%. The main number of open fountains is observed in gas fields. This is due to the peculiarities of the construction of gas wells and the possible underestimation of the dangers that may accompany this process. There is also an adaptation of technology and techniques for drilling oil fields on gas. Fountains can be caused by the opening of the lower productive horizons without overlapping the upper, especially with abnormally high formation pressure. Also, the highest frequency of emergency gushing occurs during reconnaissance drilling. In the table you can see the absence of such factors as: obsolete equipment; untimely replacement of equipment that has expired; not carrying out preventive repair work. These factors were not mentioned in the sources of the accident, but for the specifics of the oil and gas industry of Ukraine, the operation of the equipment is an extremely acute problem. It is important to note the fact that equipment that has used its working life is present not only at the stages of well construction, but also at decommissioned wells (abandoned wells), which often remain without the control of responsible organizations. This state of affairs creates a high risk of emergencies, including GOWM and OF. In Khludenev's (2007) researches results of the analysis of mathematical dependences where the basic factors promoting intensive operation of the equipment are defined are resulted: temperature, pressure, material execution of the equipment, an aggregate condition of the environment. - a given or