Development of Directional Drilling and Survey System: Outline of the System

摘要

In Japan, the soft sedimentary rock of the Neogene Tertiary is being examined as a host rock forrnhigh level waste (HLW) disposal. In particular, the soft sedimentary rock in the coastal area is thoughtrnto be one of the best candidates, since there is little driving force from underground water.rnMeasurement and logging of boreholes to investigate the hydrogeological and geomechanicalrnconditions of the host rock are very important ways to evaluate the potential of the disposal candidatesrn(NUMO, 2004).rnSince 2000, Central Research Institute of Electric Power Industry (CRIEPI) has been conducting arnproject on directional drilling and logging/measurement technologies in its boreholes. Based on thernresults of phase 1 (2000–2004), CRIEPI has been developing drilling and logging/measurementrntechnologies for fault zone. Drilling technologies such as drilling in a fault zone, horizontal drilling,rnlong hole drilling, coring, and locality detection were developed and their applicability during drillingrnwas confirmed. A permeability/water-sampling/imaging tool was revised for application to widerrnboreholes and longer measuring section. Wire-line logging while drilling (WL-LWD) was improvedrnfor greater toughness in the hole. The borehole pressure meter and stress measurement tools werernunified. Each tool needed for the long term monitoring system was manufactured. The applicabilitiesrnof these tools and systems were verified in the borehole.rnAfter geological and geophysical surveys were conducted for the Omagari fault distributed in thernKami-Horonobe area at Horonobe in Hokkaido, the drilling site and borehole trace were chosen inrn2005. Using the planned trace, the borehole was drilled to a length of 1000 m; core recovery wasrn99.8% as of FY2011. Using borehole logging/measurement/surveying and core logging/testing,rngeological, hydrological, geomechanical, geophysical, and geochemical data were collected, and thernOmagari fault was characterized.