| Abstrakt: |
Dip effect on induction-tool response is a well-documented and well-understood environmental effect that produces increased shoulder effect at moderate dip and a complete scrambling of multiarray induction logs at high dip. Although techniques such as maximum-entropy inversion allow a full correction of the logs, these remain computer-center products that are somewhat time-consuming. Wellsite inversion to correct for dip effect has remained elusive, waiting on more computer power. In the mid-1960s, Pierre Grimaldi discovered an induction measurement technique that had the remarkable property of returning the same reading in a "thin" bed that it gave in an infinite, homogeneous medium of the same conductivity. The only requirement to satisfy this condition was that the instrument sensors were all in the thin bed. The instrument configuration was such that the voltage measured was a direct solution to Maxwell's equations. Although this was a breakthrough, the instrument configuration was difficult to realize in hardware, particularly with the well-logging technology of the 1960s, and the idea was never published. The Grimaldi configuration was independently rediscovered in the early 1980s and studied with new modeling codes. It was found that the "remarkable property" of having no shoulder effect was also approximately true at any dip angle. Again, the hardware was deemed to be impractical. More recently, it was discovered that the array configuration of the AIT* Array Induction Imager family of tools was such that the raw array-measurements data could be processed to be the same as those from a Grimaldi configuration. This led to a real-time algorithm, and a set of Grimaldi curves is now available at the wellsite. This algorithm produces synthetic arrays equivalent to a Grimaldi coil... [ABSTRACT FROM AUTHOR] |
