Development Of Data Acquisition System For The Resistivity Distribution In Array Induction Well

The array induction tool overcomes the shortcomings of the conventional resistance tools, such as:the small detection range, the low resolution, the insufficient information, the low accurate, the low efficiency in logging and etc. Therefore, it can realize the high precision measurement in resistively distribution of inhomogeneous reservoir, low resistance strata and fresh mud. The extraction process for the induction signal is very complicate because the signal getting by the theory of the electromagnetic induction is very weak and the interfering factors are relatively complex. In order to extract much more precisely sensing signal to reflect the formation resistivity distribution information more accurately, a series of processing should be execute on measurement signal.Firstly, the overall design of preprocessing module and data acquisition processing system in the array induction logging system has been studied. The system selects DSP chip of TI’s TMS320F2812 as the core control devices, and it combines the front-end preprocessing module and analog to digital conversion module to achieve a logging instrument data acquisition program. Secondly, the signal preprocessing hardware circuit is designed. Differential circuit is the main part of reamplifier circuit and the reamplifier circuit is designed based on the method of combining integrated circuits and discrete components. The second-order high-gain multiple negative feedback active bandpass filter circuit also is designed and it includes preamplifier, band-pass filtering, gain control, differential amplifier and high-precision A/D converter circuit. In addition, data acquisition-control system is designed and signal processing algorithms are researched. Data acquisition and control system use multi-DSP architecture. The main DSP communicates with the ground system by using the CAN bus. The data between DSP and the main DSP is transmitted by SPI bus.At the same time, data phase-sensitive detection algorithm also is researched. Finally, the data acquisition system’s software flow diagram of array induction logging tool is drawn.The results of simulation and testing experiment in front-end preprocessing circuit and signal processing algorithms show that the system meets the performance indicators in real-time sampling rate, measurement accuracy, data stability and other aspects.