Development of mathematical models of gas leakage and its propagation in atmospheric air at an emergency gas well gushing

Abstract

The study tackles the development of new mathematical means for determining distribution in space and time of technogenic load on atmospheric air as a result of non-burning gas well gushing. To date, modeling is the only tool for studying and solving pressing problems of environmental safety in operation of gas condensate fields. This is especially true for those issues that cannot be solved in practice, such as studying causes and predicting occurrence of emergencies with a low probability of occurrence but with heavy devastating consequences. Drawbacks of the existing mathematical models and methods which make impractical their use in modeling atmospheric pollution in the case of non-burning gas well gush were pointed out. The problem of forecasting the level and distribution of atmospheric air pollution in open gash of a gas well involves two steps: determining amount of gas releases, their parameters and composition; calculation of harmful substance scatter in the near-surface atmosphere. Physical peculiarities of the gas mixture movement through the well and distribution of pollutants in atmospheric air during non-burning well gushing were studied. Mathematical models of stationary and burst release of a mixture of gases from a well were constructed as differential equations with corresponding initial and boundary conditions. These models take into account all major factors affecting intensity of the gas mixture flow during an emergency gushing and adequately describe the process. A new mathematical model of pollutant spread in atmospheric air during release from a well has been constructed. This model, unlike the existing ones, is a set of three analytical dependences describing distribution of contaminants in space and time in the case of burst, short-term and continuous releases, respectively. The results of mathematical calculations were compared with the data of field measurements of concentration of pollutants that were part of the gas flow during emergency release at a gas condensate field in Poltava region. It was established that the modeling error did not exceed 15% for all substances under study. This comparison has confirmed high adequacy of the developed models and the possibility of their application to solving a wider (compared to existing models) class of problems related to monitoring the atmospheric air in the territories of gas wells under various release conditions, meteorological characteristics, and the drilling rig operation conditions