Basic developments in the gas sphere:

• fundamental work has been carried out to create mathematical models, devise methods and algorithms of solving scientific and technical problems in the field of gas dynamics and gas filtrations;
• study of technological, gas-dynamic and filtration processes of gas transportation and storage;
• development of original application software to solve problems of finding technological mode, which have been tested in operation;
• training highly qualified experts in all spheres related to the problems of modelling and optimization of gas transportation and storage .

Fundamental research has been carried out in the following spheres:

• modelling of gas movement for all technological facilities involved in gas transportation and storage;
• development of methods and algorithms for solving   direct and reverse problems in mathematical physics, studying conditions for their convergence, evaluation of speed of method convergence and evaluation of algorithm complexity;
• development of optimization methods for complex nonlinear systems with the distributed parameters;
• development of algorithms for optimum gas flow control;
• development of process automation system solving technological problems and problems of finding the optimum mode.

Major achievements: 

• the graphical user interface for both designing technological schemes for gas transport system (GTS), compressor stations (CS), underground gas storage facility (UGSF) and providing their parametrical and model description;
• the designing of anall-inclusive set of the technological schemes of Ukraine’s gas transportation system, and the designing of a set of the algorithms for operating it;
• integrated planning environment (IPE), enabling for GTS engineers to find the optimum directions and rates of the gas flows, serving as a technological schemes design workstation, valves log book and welding log book, and making use of book logs from all levels (IPE is being implemented);
• models and methods of thermo-hydraulic calculation of steady and unsteady gas flows according to technological schemes of different complexity degrees;
• calculation methods for finding optimum parameters of operating modes of work of GTS, UGS and multi-shopCS with gas-compressor units of different types;
• models and methods of calculation of parameters of work of gas reservoirs with non-uniform filtration and reservoir properties;
• application software modelling compounds of UGS and gas mains;
• algorithms for finding the optimum parameters of gas flow control in hardly predictable program input conditions (some parts of the system are currently being developed and tested).

OPTIMAL GTS MODES PLANNING

The software description. The mathematical model of the Ukrainian GTS involves models of all production components present in the piping and instrumentation diagrams. The method of finding the parameters of a gas flow aims at ensuring observing fine-resolutionbalance conditions and does not depend on what mathematical model of objects is being used. The model of the GTS provides for adding objects with discrete characteristic functions, for example a back-pressure valve.Due to the high convergence rate of the method, it is capable of performing calculation for tens of thousands of component starting from zero input values. This makes it possible to model the way the GTS works without simplification.

Results:

• hydraulic calculation of a multi-shopCS with gas-compressor units of different types, which provides for taking into consideration each gas-compressor unit‘s characteristics and analyses how alteration to its operating parameters affects the work of compressor station;
• algorithm for finding the optimal operating parameters of gas flows, given the amount of the natural gas in Ukraine’s gas transportation system and its sybsystems;
• identification of models’ parameters and their components’ technological states, which ensures a high degree of accuracy despite the indetermination of conditions of their operation

Key Points of Our Software:

• the method of calculation can deals with tens of thousands of gas transportation system’s components, which provides for processing its detailed pipeline flowsheets;
• the actualization of pipeline flowsheet takes a few seconds;
• the method forhigh-level calculation is capable of making use of however exact underlying component’s representation;
• convergence of the algorithm is ensured assuming that algorithm starts from zero input values; non-gradient procedures for solving non-linear combined equations has been devised;
• the calculation of Ukraine’s gas transportation system takes a few seconds, which provides for optimization based on all main optimization criteria.

MODELLING NON-STATIONARY OPERATING MODES OF GAS TRANSPORTATION SYSTEM

Methods and algorithms for modelling non-stationary modes are able to be adapted for actual operating object’s parameters and accordingly modify the piping and instrumentation diagrams to ensure methods convergence as well as required speed and accuracy.

Description of the application software. The non-stationary mathematical model of Ukraine’s gas transportation system involves models of all production components present in detailed versions of the piping and instrumentation diagrams. High processing speed and stability of the method is possible owing to their shrinkage algorithm, which still ensures given accuracy. The accuracy of the calculation of non-stationary operating parameters is commensurate with the accuracy of reading off operating parameters from pipelines running through sharp relief. Conducting the modelling of the GTS expects prior non-stationary identification of component’s parameters. All main control parameter of compressor station (like compressor output, rate of supercharger, natural gas characteristics at both its ends) are available for alteration by an engineer in manual control mode.

Main software modules:

• creating the non-stationary model of Ukraine’s gas transportation system or its subsystem;
• adaptation of models, methods and algorithms for actual parameters of gas-dynamic processes, schedules of operating procedure, geometric parameter of pipeline sections.

FINDING PARAMETERS OF GAS FLOW CONTROL

The problems of optimal control of non-linear gas-dynamic processes with the discretely and continuously distributed parameters were defined. It is worth mentioning that the general theory for these problems is under development. Methods for solving combined non-linear equations of mathematical physics, having boundary condition being formed in the course of modelling gas-dynamic processes in Ukraine’s gas transportation system and meeting the criterion of optimality, were devised.

Results:

• optimal control concepts take into account the fact that expected, hydraulic, technological and technical parameters may change;
• system models of operating object groups, which include underground gas storage facilities as well, are validated;
• adaptive methods and algorithms for finding operating modes of gas transportation systems are capable of using piping and instrumentation diagrams without their simplification;
• algorithms for optimal control of gas flows can deal with complex piping and instrumentation diagrams;
• algorithms for optimal control of pumping into and out of underground gas storage facilities.

It has been a successful trial for

• automation algorithms for drawing up schedules of operating procedure for Ukraine’s gas transportation system and its components, which provides for optimal gas flow control in the way of minimal fuel and energy resources.

UNDERGROUND GAS STORAGE FACILITY MODELLING

The program provides:

• planning and optimization of UGS operation;
• finding operating parameters of a technological chain composed of
• a bed and gas-main towards and backwards the direction of gas movement (direct and reverse problems);
• research into facility capacity (searching for bottlenecks);
• optimization of UGSs’ joint operation within the GTS;
• modelling of processes of gas-gas miscible displacement;
• carrying out gas-hydrodynamic researches on beds and wells;
• finding of the nonlinear distributed characteristics of beds and borehole bottom areas;
• research on effect of parameter values of perforation channels and wells with open borehole bottom on UGS operation;
• research on effect of geometrical, collecting, filtration and other parameters on technological modes of wells and beds operation.

The basis of software development is the achievements in the investigations carried-out in such directions:

• study of gas movement processes (an energy and mass transfer, including diffusion processes) in multiply connected heterogeneous multidimensional porous environments provided (distributed or concentrated) outflows and inflows (weight or energy) are available;
• developing methods for finding initial and boundary conditions for mathematical physics problems on domains with indistinctly defined borders using parameters of concentrated inflows and outflows;
• developing robust adaptive methods for solving mathematical physics problems of mass transfer in multiply connected heterogeneous multidimensional porous environments;
• creation of the mathematical models which describe interrelation between non-stationary nonlinear gas filtration processes in multiply connected heterogeneous multidimensional porous environments and gas diffusion in liquid present in porous environments;
• research on environment inhomogeneity (porosity, permeability) using measured hydrodynamic properties of concentrated inflows and outflows during non-stationary filtration regime; solving inverse problems of UGS parameter identification and adaptation of developed mathematical models to actual operating conditions; devising identification methods