Borehole Informatics: Data Integration Challenges of Scientific Drilling

Abstract

The ultimate goal of scientific drilling is to precisely understand the dynamic nature of the Earth. Thus we need to investigate why and how the subsurface materials (rock and fluid including microbial community) exist under what environmental conditions. This requires sample collection and data measurement at borehole in an excellent quality. Then all of the data from cores, cuttings, mud logging, geophysical logging, drilling parameters, and exploration geophysics are integrated to obtain the comprehensive picture of our scientific target, e.g. seismogenic fault zones and the Moho discontinuity surface. We call this approach ‘borehole informatics’. The input data of borehole informatics consist of various kinds and scales, thus the gap between these datasets needs to be filled. Among several challenges, one of the most important issue is depth matching. All of the data to be integrated must represent exactly the same subsurface point, otherwise combination of data from different depths will produce misunderstanding of underground nature. We are now measuring CT values on all core samples immediately after core recovery, using an X-ray CT scanner on our drillship ‘Chikyu’, and determine the core depth in centimeter accuracy by comparing the pattern of the core-CT log with density logging data. The effort of precise depth determination makes it possible to produce cross plots of core analysis data with geophysical logging data, then with geophysical datasets. We are also developing methodology to extract more information from currently available data (mostly geophysical logging and seismic data) to bridge the gap between different scales of the data. In this presentation we will introduce our approach of borehole informatics and current achievements at two areas offshore Japan where seismic, borehole data and core data are all available. One area is situated in a hydrocarbon bearing basin where continuous coring was conducted through a coal layer zone. The other is a plate subduction margin where mega-earthquakes have repeatedly occurred.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016