For accurate and stable monitoring of the oil/gas and fluid distributions in the reservoir during the EOR (Enhanced Oil Recovery) operation even if the well distance exceeds a thousand meter, JOGMEC (Japan Oil, Gas and Metals National Corporation) is developing a crosswell electromagnetic survey system with applying a super-sensitive magnetic sensor "SQUID" (Superconducting Quantum Interference Device). In this study, we have developed the component technologies of borehole SQUID magnetometer and powerful transmitter coil. The SQUID sensor performs in the temperature condition of 77 K, where the liquid nitrogen is available for cooling. To deploy the SQUID sensor in the deep borehole safely, we designed and trial fabricated pressure- and heat-resistant vessel which contains the glass Dewar of liquid nitrogen, release tubes of vaporized nitrogen gas, electrical circuits, and other devices to control the SQUID sensors. The developed transmitter coil has magnetic moment of 27,500 Am2, which will satisfy the intensity for our purpose. We demonstrated the stable operations of the prototype models of borehole SQUID magnetometer and transmitter systems with using the research wells of the JOGMEC field, of which maximum depth is 300 m and cased with conductive tube. The SQUID magnetometer has the ability to be deployed in the environment of 3,000 ~ 4,000 m deep boreholes by the laboratory experiments. At the next stage, we will demonstrate the systems at the actual borehole, whose typical depth is greater than 1,000 m. On the other hand, we have been developing the algorithms to interpret and correct the effects of conductive casing tubes, and three-dimensional modeling of underground structure. For the demonstration of their performance, we will also conduct the crosswell measurement with using the test wells.

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