Roy David Nurmi1
(1) Borehole Geoscience & Technology, Houston, TX
Abstract: Predicting structure and reservoir features away from a well using borehole resistivity imagery or dipmeter surveys
Dipmeters and borehole imagery define geology characteristics of the sequence drilled as well as provide information about where to drill the next well. The early dipmeter logging service 50 years ago only provided the dip magnitude and azimuth from the depth stations measured and nothing else. Gradually dipmeter technology evolved, providing more and more resistivity measurements with progressively higher vertical resolution that this data itself became value. Approximately 10 years ago it was realized that by a still greater increase of high resolution measurements it would be possible to have actual images of many of the geological characteristics of the formations logged.
With the evolution from dipmeters to borehole imagery no geological applications have been lost while the greater formation details which aid in predicting the geology away from the logged well have been gained. A better definition and certainty of structural dip aids in how to drill the next well along anticline, fault or salt structure. The improved characterization of fractures and their attributes improves the ability to target a trajectory to either intersect or avoid fractures depending on the situation, especially with the use of horizontal wells. Imagery has greatly improved the analysis of faults and their associated deformation which has dramatically impacted the understanding of many reservoir fracture systems throughout a reservoir. While dipmeters allowed explorationists to follow individual channels, borehole imagery has been used to intersect a number of channels using horizontal wells. Such interpretations require the interpretation of sedimentary structures not defineable by dipmeter data.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana