Resource-Efficient Model of an Offshore Platform Compressor Station for the Declining Production Period of a Gas-Condensate Field

Under conditions of gradual depletion of gas-condensate field reserves and declining well production rates, one of the key challenges in operating offshore production facilities is improving the energy efficiency and reliability of process equipment, particularly compressor stations used for gas gathering, treatment, and transportation. Resource conservation and the adaptation of operating modes to changing production conditions require flexible compression systems capable of operating efficiently over a wide range of inlet flow rates and pressures. This article examines examples from three key regions where compressor stations have been adapted to declining production rates and reservoir pressures, and analyses the challenges encountered under actual operating conditions. A compressor model is proposed for the late stage of field development, during which the production rate of gas-condensate wells decreases from 5.0 million m3/day to 0.5 million m3/day over a ten-year period. The wellhead pressure and compressor suction pressure decline from 5.0 MPa to 0.1 MPa, while the discharge pressure remains at 5.5 MPa. Calculations were performed for the principal operating parameters, including gas production rate, wellhead and compressor suction pressures, the capacity of a single compressor under different configurations, the required number of compressors, and the total annual capacity of all operating compressors. The proposed compressor-unit reconfiguration scheme makes it possible to compress the produced gas for at least nine years using a single unit size, without replacing cylinders and without changing the type of compressor; over this period the number of units operating in parallel increases from three to six. Unlike a single oversized centrifugal machine, whose efficiency falls sharply once anti-surge recycling becomes necessary at part load, the proposed configuration is estimated to remain operable down to about 10% of the rated capacity of one unit. This lower limit is obtained by extrapolation of the model presented here and requires confirmation by test or manufacturer data.