Research On The ELF Communication Technology Inside And Outside The Oil And Gas Pipeline And Its Application

With the increase in the service life of oil and gas transportation pipelines,the demand for various types of PIG for pipeline inspection,flaw detection,sealing,cleaning,etc.has also increased dramatically.In the case of long distance fixed point operation inner the pipe for PIG,it is impossible to carry out real-time data transmission by means of cables and can only be operated according to the preset control program,so it is difficult to deal with sudden failures and risks timely and effectively.It will bring greater operational risks and operating costs.Conventional electromagnetic waves cannot be wirelessly transmitted due to the shielding effect of the metal pipe.This paper has studied an ELF two-way communication system suitable for oil and gas pipelines by using the strong penetrating ability of ELF electromagnetic waves.It can enable the PIG to receive operation instructions outside the pipe and transfer important data to the control terminal outside the pipeline timely when performing fixed-point operations in the pipe.In this paper,the 23 Hz and 26 Hz electromagnetic waves are modulated by 2FSK to transmit the data.Based on the scheme,the hardware circuit and software driver of the whole system are designed in the paper.The AD9959 chip is used as the signal source,and the STM32F405 is used as MCU.Since the traditional DFT result does not contain time components,it cannot reflect the occurrence and disappearance of the carrier frequency over the entire time period.This paper uses DSTFT to achieve accurate demodulation of ELF signals and symbol synchronization.In order to ensure the reliability of the communication data,the paper uses the error detection and retransmission mechanism to verify,which greatly improves the reliability of data transmission.After completing the design and manufacture of the whole system software and hardware,each functional module was tested.The results show that they all meet the design requirements.Then,the system's two-way communication was tested in a metal pipe with a thickness of 10 mm.The test results show that the system has high reliability when the distance from the pipe wall is less than 1 m and the symbol rate is not more than 0.8bps and meet the requirements of data transmission inside and outside the pipe when the PIG working in a fixed place.