Research On Electric Heating Technology Of Oil Well Based On DPC

Compared with other technologies of heavy oil thermal recovery, electric heating technology gets widely application for the reason that it could be easily controlled and needs less first investments. However, most of present electric heating systems of oil well exist many problems, such as low heating efficiency, large power consumption and high cost of maintenance etc. And these problems seriously increased the cost of heavy oil recovery. Therefore, how to improve system performance and then reducing the cost of heavy oil recovery is becoming an important problem to be resolved in the field of electric heating technology of oil well.In this paper, the development level and trends as well as the relevant theories of electric heating technology of oil well were comprehensively studied and analyzed. And the main causes of low efficiency and electricity wasting of the electric heating system of oil well were found out, some corresponding methods to improve system performance were proposed.The control strategy of constant temperature of well head has been adopted by most of current electric heating systems of oil well, but the temperature of well head always can not be spot-on at the beginning and could not be corrected timely. Obviously, it must cause large wasting of electricity. To resolve this problem, a new control strategy of electric heating technology of oil well based on directed power control (DPC) was proposed. This strategy aims at ensuring the oil production and reducing the electricity consumption of unit production. In the strategy, the curve fitting technology was adopted to optimize the temperature of well head and system power, so that the total power of the system (the sum of pumping unit and heating unit) could run at the best point. Furthermore, the electric heating system of oil well is nonlinear, large delay and difficult to model, and the temperature of well head could not be controlled effectively by conventional methods. Consequently, fuzzy control combined with PID was adopted to adjust the temperature of well head so as to get excellent system performance at both transient state and steady state.The working process of the pumping unit is driving a load with gravitational potential to and fro. As the load was drived downwards, large amount of electricity energy was feedbacked to the DC bus of frequency converter, and then wasted by brake resistance conventionally. To recycle the feedbacked electricity energy, a method of DC bus interconnection, namely the DC bus of frequency converter and heating power supply were connected in a parallel form, was proposed so that the electricity energy feedbacked by pumping unit could be recycled by electric heating unit.The current electric heating systems of oil well are always without high automation level, good human machine interface and communication system. These directedly cause the site operation inconvenient and the cost of system maintenance increased. Therefore, a new control system with programmable logic controller (PLC), operation panel and field bus was designed. It offers a ideal platform to run advanced control algorithm and to improve system automation level.