METHOD FOR OPTIMISING THE PROCESS OF GAS INJECTION TO AND WITHDRAWAL FROM AN UNDERGROUND GAS STORAGE FACILITY

摘要

The invention concerns a method for optimising the process of gas injection to and withdrawal from an underground gas storage facility connected to at least one gas pipeline, controlled by means of a control system, consisting of above-ground equipment for gas processing prior to being transferred to the storage facility, underground equipment and above-ground equipment for gas processing after being withdrawn from the storage facility, where input parameters of the gas storage facility equipment are being changed, and by means of the control system signals that control the change of gas storage facility equipment parameters are transmitted, characterised in that:- at the start of the process of gas injection to and withdrawal from the gas storage facility, in the gas storage facility operation optimisation system (16) located on the optimisation system server (15), the expected/forecast input data of the gas storage facility operation are being set in an assumed prediction horizon, such as external temperature, gas pressure in at least one gas pipeline (12, 12a, 12b) separately for each connection to the gas pipeline (12, 12a, 12b), for gas injection to the storage facility gas temperature and gas composition in at least one gas pipeline (12, 12a, 12b), separately for each connection to the gas pipeline (12, 12a, 12b), prices of electrical energy and fuel gas, the direction of gas flow and the gas flow volume at each connection to at least one gas pipeline (12, 12a, 12b), availability of at least one cavern (7a, 7b, 7c, 7d, 7e) and at least one compressor (4a, 4b, 4c), measurement data on gas storage facility state are acquired from the control system, such as current gas flows, gas composition, and the temperature of gas stored in the storage facility, based on which the gas storage facility underground part model state is being updated for the period from the last update up to present time, data updates are saved in the database (20) of the gas storage facility operation optimisation system (16), and by means of a calculation module (18) and the underground part simulation module (19):- at least one used cavern is selected (7a,7b,7c,7d,7e) and gas flow $V_h^{\mathit{sum}}\mathop{\mathrm{image}}$ is split between the caverns in use (7a,7b,7c,7d,7e);- the connections of each cavern in use (7a,7b,7c,7d,7e) are allocated to one of the transfer manifolds (6, 6a,6b);- the connections of each compressor (4a,4b,4c) are allocated to gas pipelines (12,12a,12b) and manifolds (6,6a,6b);- optimal operating parameters for each compressor (4a, 4b, 4c), are determined so that for a single battery of compressors (4a, 4b, 4c) the operation cost of each of the compressors (4a, 4b, 4c) is determined according to gas flow for each operating mode the compressor (4a, 4b, 4c) can operate under specific conditions, and for a cascade of two batteries of compressors (4a, 4b, 4c) an optimal pressure between batteries of compressors (4a, 4b, 4c) is selected so that for any evaluated pressure the operation cost of each of the compressors (4a, 4b, 4c) is determined according to gas flow for each of the operating modes the compressor (4a, 4b, 4c) can operate under specific conditions, then gas flow is optimally split between compressors (4a, 4b, 4c) from the first battery of compressors (4a, 4b, 4c) for each possible set of operating modes of compressors (4a, 4b, 4c) from the first battery, gas flow is optimally split between the compressors (4a, 4b, 4c) from the second battery of compressors (4a, 4b, 4c) for each possible set of operating modes of compressors (4a, 4b, 4c) from the second battery, optimal operating modes of the compressors (4a, 4b, 4c) are selected for a specific time horizon;- as a result of calculations from the previous steps value vectors of all output variables are determined in the calculation module (18) of the gas storage facility operation optimisation system (16), which describe the optimal parameters of the gas storage facility equipment in terms of optimisation and the module transmits data to the control system (13) via an interface for communication with the control system (21);- based on these optimal results received from the gas storage facility operation optimisation system (16) and saved in the control system (13), optimal signals that control the change of equipment operating parameters, selected according to the structure of the storage facility system from the following: states of cut-off valves (5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, 51, 5m, 5n, 5o, 5p, 5q, 5r, 5s, 5t, 5u, 5v, 5w , 5x, 5y, 5z), which select the used caverns (7a, 7b, 7c, 7d, 7e) and compressors (4a, 4b, 4c), flow setpoints for FCV valves (8a, 8b, 8c, 8d, 8e, 8f , 8g), setpoints of flow through compressors in use (4a, 4b, 4c), operating modes of compressors in use (4a, 4b, 4c), pressures between the levels of compressors (4a, 4b, 4c) for compressors (4a, 4b, 4c) connected in cascade, are transmitted via the control system (13);- the above operations shall be repeated with a period no longer than the calculation horizon.