Research On Key Points In The Circuits Of Electromagnetic Logging And Induction Logging Instruments

Petroleum is the most important natural resource in the world. All the time, research of petroleum exploration technology has never been stopped. With the improvement of electronic technology, especially the semiconductor device and manufacture technology, electromagnetic wave logging and induction logging have become the core technology in the field of electrical logging.In China, the research on electrical logging started later, electromagnetic wave and induction logging suffered long-term monopoly and technical blockade of foreign logging company. Under the new situation, domestic electrical logging field is facing the strategic requirements of getting rid of foreign pressure and exploiting the overseas market, so the research of electromagnetic wave and induction logging, which have proprietary intellectual property rights, is now an imminent important task.This paper discusses the application of electromagnetic wave logging in logging while drilling(LWD) system, so it has higher requirements on the circuits. Due to the requirements of measuring in multi scale and multi dimension, the design and structure of the coils and the circuits have become more complex. The receiving circuit is one of the core circuit of an electromagnetic wave logging instrument, which has a direct influence on the accuracy of measurement. In the paper, the design of receiving circuit adopts the Zero-IF receiver structure, which could simplify the circuit structure, reduce the power consumption and decrease the circuit size. A new method to realize DPSD algorithm based on FPGA is designed, which could effectively reduce the logic resource occupation and improve the efficiency of the algorithm. Finally, the rationality and validity of software and hardware designed by these methods are verified by experiment and test, which meet the design requirements.Direct coupling restraining is an important step in the installation of induction logging instrument, and could be very complicated because of the large amount and complex construction of coil. In this paper, a improved method is raised to greatly simplify the process of direct coupling restraining, to improved the precision and stability, and to realized the on-line and automatic direct coupling restraining. he results show that the modified method can effectively meet the design requirements.