Research On Wireless Energy Transmission System Of Ultrasonic Wave Through Casing

Oil and gas have always been China's strategic resources,which is very important for the monitoring of oil Wells and the production of crude oil.In the process of oil production,people obtain downhole temperature,flow rate,water holdup and other parameters by means of regular logging,in order to adjust the mining strategy,formulate the optimal mining plan,and provide a basis for further high and stable production.At present,the mainstream production logging method still uses wireline logging,its disadvantage is that the cost of logging is high,so it is not realistic to carry out regular logging(such as once a month).In view of this,logging engineers put forward the measurement method of downhole permanent sensors,which are used to monitor downhole temperature,pressure and various physical parameters,continuously working under battery-powered conditions and recording downhole information can not only provide continuous logging data,but also save logging costs.But now the technology of storage for permanent downhole sensor power battery capacity is always limited,if a wireless charging system through casing can be designed with the characteristics of no pollution,detachable and no damage to the casing structure,the charging problem of the battery outside the casing will be solved.Therefore,it is of great engineering significance to study the wireless energy transmission system through casing.In view of the above problems,this paper introduces the principle of ultrasonic energy transmission,analyzes the relationship between energy transmission efficiency and frequency,discusses the influence of impedance matching on energy transmission system,puts forward a solution based on ultrasonic wireless energy transmission,gives the technical indicators of the instrument,and expounds the hardware circuit and timing logic of the instrument in detail.The specific contents of hardware circuit implementation and timing logic are as follows:(1)FPGA is used as the main control unit of the circuit to complete functions such as excitation frequency,power control,current protection,status display and adjustment.(2)In order to drive the transmitter transducer,two half bridge drive chips and four MOSFET components are used to form the bridge drive circuit(3)In order to reduce the energy loss and make the transmitter and receiver circuits show the pure impedance,a dual port impedance matching circuit is designed.(4)In order to measure the received power of the receiving end energy,a test circuit composed of high-power LED lights is designed.In the test part,the energy transfer experiments of steel plate with different thickness and the energy transfer experiments under different conditions of receiving end impedance are tested.The experimental circuit was made through the above scheme,and related experiments were carried out.The research results show that:(1)Ultrasonic waves can be used to achieve wireless energy transmission through the casing,and the maximum power that can be received on this experimental device is 1.55 W.(2)The energy transfer efficiency is related to the load impedance of the receiving end.In the range of0-3k?,the relationship between the transfer efficiency and the impedance increases monotonously.