Abstract

Up-to-date status of CRIEPI's development of hydro-fracturing stress measurement unit is presented. It is adopted in the CRIEPI Directional Drilling and Survey System (DDSS). This HF stress measurement unit needs to be developed so that it is applicable to the Directional Drilling and Survey System. The unit is connected via flexible cable to surface controller. The cable contains copper lines and optical fibers for the power supply and signal transmission. Since water for the hydro-fracturing cannot be supplied from the surface in the DDSS, the unit contains water tanks and pumps. For the purpose of observing the operation in the hole, a set of camera and AE sensors are installed. And the unit needs to be applicable to a horizontal borehole.

In this paper, the back ground of this development, the structure and the specification of the hydro-fracturing stress measurement unit, and an example of its verification test are presented. The CRIEPI DDSS is supposed to be applied in Preliminary Investigation for the site selection for high level radioactive waste disposal, when the candidate site is in a coastal region of sedimentary soft rock. In such cases, the presumed depth of the disposal is expected to be around 500m or so. The specifications, such as pressure, flow rate, etc., of the hydro-fracturing unit have been set considering such conditions. The unit has been applied to a few on site tests for its evaluation. The results of the tests, including the handling performance at the drill tower, will be presented.

This study was done under contracts awarded from the Agency for Natural Resources and Energy (ANRE), the Ministry of Economy, Trade and Industry (METI), and in-situ drilling and surveying was conducted in collaboration with the Horonobe Underground Research Center of the Japan Atomic Energy Agency (JAEA).

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