RESERVOIR DYNAMICS FOR MEGASYSTEMS IN GEOCHEMISTRY: FORMATION OF BASE MODELS OF PROCESSES AND ALGORITHMS FOR SIMULATION

Using thermodynamic-potential minimization as a base, an approach to the formation and investigation of simulations of dynamic megasystems has been developed. By dynamic megasystems are meant natural and geoengineering systems, or reservoirs, which interact chemically and are connected with each other by direct, reverse, and through flows of matter and energy. The structure of a simulation model is formed by combining basic constituents and directive parameters. The user can choose diverse variants of aggregating systems and flow connecting the system to a single physicochemical object, i.e., into a megasystem. The evolution of megasystems can be calculated by two algorithms. In the first algorithm, two operations are performed in a unit of time: calculation of the equilibrium for all systems at a time and then transfer of matter by flows in accordance with a given matrix of macrokinetic coefficients of transfer. In the second algorithm, the megasystem evolution in time and space proceeds cyclically. In each cycle, calculation of the equilibrium for the systems and transfer of the matter by flows are performed consecutively from system to system in accordance with the number of system and matrix of macrokinetic coefficients. The number of time units is equal to the number of systems in a megasystem. The cycle of the second algorithm ends in the system with the greatest number, and the next cycle begins with the first system. The most important trait of both algorithms is separation of the flows into groups of mobile phases. The flows of aqueous solutions, gas mixture, solid materials (eolian dust, furnace charge, mineral suspensions in water), liquid hydrocarbons, organic material, etc. can be transferred from system to system. Each group of mobile phases has a matrix of macrokinetic coefficients. If required, the macrokinetic coefficients can be recalculated by built-in algorithmic operators in the intervals between time units. The proposed approach is illustrated by two examples. In the first, the tolerance of Lake Imandra (north of the Kola Peninsula) for pollution with nepheline – apatite production waste was investigated by an integral physicochemical index – pH of water, depending upon the sewage volume. In the second example, the redistribution of material in the megasystem Al₂O₃ –SiO₂–H₂O was studied. The redistribution is caused by an external energetic effect, production of a stationary nonisothermal profile at T = 300–440 °C and at P = 3 kbar. The simulation results are compared with Vidal’s experimental data. The formation procedures and simulation algorithms for dynamic megasystems were realized in the form of the “Reservoir dynamics” module, included into the program complex Selektor-C designed in 1997. It can be employed for solving scientific problems, for engineering, and education.