Application of inlet fogging for power augmentation of mechanical drive turbines in the oil and gas sector

The use of inlet fogging systems to boost the power for gas turbine engines is well known and extensively applied in the power generation field. In this paper the application of inlet fogging of gas turbine engines utilized in the oil and gas sector for mechanical drive applications is covered. Extracting oil from a well is often limited by the rate of gas extraction, and consequently by the gas turbine power and efficiency. In hot and dry air climates, such as desert areas of the gulf countries, gas turbine engine power output is dramatically reduced because of the reduction in gas turbine air mass flow. This effect is even more predominant with aeroderivative units that are commonly used in this sector. Cooling the air to the wet bulb temperature, will increase the density of the air, increase the air mass flow, and boost the power and efficiency. Consequently the amount of extracted gas, and therefore oil, will be substantially increased. With such a cooling potential, and the current trend in oil prices, inlet fogging can have a very rapid payback. In this paper, the behavior of gas turbines with and without fog injection will be analyzed in detail based on actual field data. Critical parameters such as the power turbine inlet temperature, exhaust temperatures, compressor discharge pressure, the gas generator and power turbine speeds, as increasing stages of fogging are applied are covered. Furthermore, specific issues relating to the design and control of fogging as applied to aeroderivative engines will be discussed.