The objective of this work is to make a simulation to be possible to reproduce and to optimize the operating conditions of the Natural Gas Processing Unit, which belongs to PETROBRAS (Brazilian Petroleum Limited Company). The unit process is the refrigerated absorption and it has been studied its energetic optimization and the reduction of absorption oil molecular weight. The simulation has been built in a unique computer file. To bring near the column internal flows and temperatures to the real values, column stage efficiencies have been incorporated using a method, developed in this work, beginning with O’Connell global efficiency. For optimization, two aspects have been studied. Firstly, it is proposed to reduce the molecular weight of the oil, until the molecular weight of the natural gasoline (C-5+). This has resulted in a possible reduction of the fuel gas in 30.7% and 5.8% in the total absorved power. Secondly, the application of PINCH technology has shown that it is possible to economize until 16.4% of the fuel gas, making a new lay-out of the process.