Mathematical modelling of operating modes of underground gas storage facilities
Underground gas storage facilities (UGS) are considered, which are technologically inseparable objects of a single gas transportation system (GTS) and provide reliable supply and gas transit. The system analysis of the problems arising in the process of UGS operation, as a separate technological facility, and as part of the gas transportation system, led to the search for ways to solve them. The existing methodological support, which has been transferred from gas production without changes, and metrological support does not provide high-quality information support for dispatching systems. Now most of the existing problems with the least resource costs can be solved by means of modeling and optimization. To this end, mathematical models of all the main technological objects involved in the process of injecting into reservoirs and withdrawing from gas layers are proposed. The models are adapted to real data - the values of the gas flow parameters in the area of their possible change. The process of constructing an integrated model and its analysis shows the instability of the work of the implemented methods at the junction of heterogeneous objects (instability of the process of «cross-linking» the parameters of gas-dynamic processes) to ensure, with a given accuracy, the equality of balance equations. In order to avoid this effect, new methods for solving systems with different mathematical representations of the equations are proposed, ensuring a stable obtaining of the result with guaranteed accuracy. In addition, a method for solving systems of equations is implemented, the matrix of the numerical model of the reservoir is sparse (contains a large number of zeros), which allowed to speed up the process of obtaining results by several orders of magnitude. To simulate compressor stations, an imitation (algorithmic) model is proposed. This approach makes it possible to take into account the actual state of each gas compressor unit and set optimization tasks according to the criteria for the stability of the compressor station and its optimality by the energy criterion.