The Application of Borehole Image Logs to Fluvial Facies Interpretation
Marinus E. Donselaar, Jasper M. Schmidt, 2010. "The Application of Borehole Image Logs to Fluvial Facies Interpretation", Dipmeter and Borehole Image Log Technology, M. Pöppelreiter, C. García-Carballido, M. Kraaijveld
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Electrical borehole image logs have the potential for the direct interpretation of lithofacies types. The challenge is to create a set of diagnostic criteria with which microresistivity variations can be translated to lithofacies characteristics such as bedding sequences, sedimentary structures, and vertical grain-size successions. Behind-outcrop logging is a method to directly validate the borehole images to real rock. In this chapter, sediments of the Huesca fluvial fan (Miocene, Ebro Basin, Spain) are used for the validation of behind-outcrop borehole image logs. The logs were recorded in two 200-m (656-ft)-deep wells behind cliff-face outcrops. In addition to the outcrop control, one well was cored. Borehole image log facies were defined from the vertical color succession and the dipmeter pattern and were correlated with the fluvial facies associations in outcrop. Four fluvial facies associations and corresponding borehole image facies were interpreted: (1) meandering rivers, (2) braided rivers, (3) crevasse deltas, and (4) crevasse splays. Vertical dipmeter successions were analyzed and yielded directional trends of the fluvial channels.
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Borehole imaging is among the fastest and most accurate methods for collecting high resolution subsurface data. Recent breakthroughs in acquisition, tool design, and modeling software provide real-time subsurface images of incredible detail, from the drill bit straight to a workstation. Associated interpretation workflows offer the high level of detail that is needed to make operational decision and to increase the predictability of subsurface models. Many exploration and production companies have acquired a wealth of dipmeter and image log data. The data are readily available and provide, for example the orientation of fractures and fluvial channels in space. Further applications of borehole imaging technology include matrix and fracture characterization, pore-type partitioning, geosteering, and in-situ stress determination. Exciting new applications are found in enhanced oil recovery, carbon dioxide sequestration, and geothermal projects. In addition, borehole image data are paramount to unlocking unconventional plays such as shale gas and coal-bed methane. AAPG Memoir 92 portrays key applications of dipmeter and image log data across the exploration and production life cycle. (Continued)