This paper presents the retrofit of the two-flow heat-exchange system with utility paths in order to optimize the heat recuperation capacity under the technical limitation conditions. Analytical dependences of heat load of the existing heat exchangers and utilities on the surface area of the new heat exchanger are obtained. The work shows that the determination of technological parameters for existing heat exchangers during the retrofit of the heat exchange system is an important task because they affect the cost of retrofit. For case study, two streams problem for heat transfer in heat network at the crude and gas separation units is considered in this paper. The existing system has three heat exchangers. The temperature measurements were fulfilled for all heat exchangers and the heat loads for heat exchangers and utility were calculated. The installation of one heat exchanger at the cool side of the system is proposed in retrofit. The dependences of the temperature changes for the hot and cold process stream from the value of the additional surface were obtained for each heat exchanger. Utility capacity and capacity recovery of thermal energy in the system is also analyzed.