Research On The Method Of Electromagnetic Induction Data Tansmission In Downhole

In oil-gas exploration and well drilling industry, the traditional mud pulse telemetry is the industrial standard of the measurement while drilling data acquisition, the typical transmission speed is 3~6bit/s, under the perfect condition can achieve 12bit/s. But, this speed is too low for high resolution data acquisition and high density data work, such as the earthquake while drilling or the downhole image formation. The existing other technologies of measurement while drilling include: the plug method, the wet attachment method, the wireless electromagnetic method and so on, these methods all have the limitation of their own.The electromagnetic induction data transmission is a new technology for data transmission while drilling. It based on the principle of electromagnetic induction and achieved a high-speed data, real-time transmission by installing induction coil at both end of the drill pipe,which is used for inducing the electrical signal. This article is in the purpose of establishing an experiment system to simulate the work process of the real electromagnetic induction data transmission while drilling system. It is to discover and solve some kinds of technical difficulties and build the foundation of this technology applied in practice, by studying on the experiment system application.The main tasks of this article include: the overall scheme design of the experiment system, the characteristic analysis and the parameter design of induces coupler's the design of modem, the design of relaying circuit and the correlative application program.This experiment system achieves the maximum data transmission rate of 57600 bit per second and can simulate the surface and downhole communication modules for half-duplex communication. The signal can pass through 4 simulation drill pipes and the data transmission accuracy is higher than 99.9%, without the relaying circuit. This article uses the induces coupler simulate drill pipe's induction attachment to couple the signal, and use the binary frequency-shift keying (BFSK) method modulate or demodulate the signal, with a carrier's center frequency is about 240 kHz.. The relaying circuit can repeat the weaken signal and change the signal channel by analog switches. Therefore, the data can be transmitted in two-way.