Effects of Operating Pressure on Energy-saving of Water Recycling Utilization with MVR system in Oil Extraction Fields

One of the most effective methods for the extraction of crude oil with high viscosity is injecting high temperature water vapor to the oil well. To save water consumption and achieve zero discharge, it is needed to separate and purify the water, which is mixed with oil, mud and other impurities. In this paper, the mechanical vapor recompression (MVR) system is analyzed and the parameters for analysis are based on a demonstration project on water recycling utilization in the Karamay crude oil field in northwest China. Two kinds of technological processes, high pressure and low pressure processes are proposed by the authors. The recovery work is utilized to decrease power consumption of the compression work and the energy from the high temperature purified water is used to drive an absorption refrigerator. The results show that 680 kJ/kg of energy can be saved in the high pressure process compared to a low-pressure process. For low pressure process, the saving energy is only 420kJ/kg, the material is easily corrosive, and additional 9.8t/h cooling water is needed. Compared the MVR system with TVR one, when the same pressure ratio and mass quantity of condensing water are obtained, the MVR system need use about 80 kW electrical power from compressor and the TVR system need use 3129.5 kW thermal energy from steam.