Determination of oil reservoirs safe operation period in the Republic of Tajikistan. Part 1. Rate of corrosion and growth of pyrophoric corrosion deposits

Purpose. The consequence of the impossibility to meet oil demand of the Republic of Tajikistan for products using only its own oil producing enterprises is the need for imports from various countries with up to 85 % of imported raw materials coming from Russia. The quality of oil imported from different sources determines the potential not sameness of the stored product impact on the structural materials of the tanks and necessitates the selection of fire and explosion safety tanks criteria and methods for determining them. The informative criteria that determine the period of their safe operation are the layer thickness of pyrophoric products of tanks inner surface corrosion and the corrosion rate of the tank steel. The main objective of the work is to determine the fire and explosion hazardous properties of oil entering oil storage facilities in Tajikistan. Such properties of oil as provoking a tendency to form pyrophoric deposits on the inner surface of tanks and emergency perforation of tank steel as a result of corrosion processes were determined. Methods. Long-term corrosion tests were conducted in oil, ready-made water and the steam-gas space of tanks with different origins of the stored product – 3 oil samples were taken from oil fields in Tajikistan, 2 oil samples were transported from Russia (produced by PJSC «Tatneft»). Findings. The corrosion rate of tank steel in corrosive phases corresponding to oil from various fields (vapor-gas phase and ready-made water) was calculated. An assessment of the possibility of a fire and explosion hazard situation occurring at an oil and gas industry facility when the thickness of pyrophoric deposits reaches a critical thickness was made. Research application field. The results of the study can be used in planning measures to protect vertical steel oil tanks of oil and gas industry facilities in the Republic of Tajikistan from ignition. Conclusions. It was established that for oil from all fields in the Republic of Tajikistan the rate of general corrosion in the ready-made water is somewhat higher than in the steam-gas phase (with the exception of the «Patinak» field, for which the most corrosive phase is the bottom water). The occurrence of a fire and explosion hazard situation on tanks with Russian imported oil is possible six months or less after the tank is put into operation. The period of accident-free operation of tanks with oil from various fields in Tajikistan, even without special means of anti-corrosion protection of their internal surface is about three years.