发明名称 Method and apparatus for determining the in situ larmor frequency of a wellbore NMR tool to compensate for accumulation of magnetic material on the magnet housing of the tool
摘要 A system includes a wellbore tool disposed in a wellbore and a surface apparatus disposed at a surface of the wellbore. Prior to operating the tool to take an initial measurement, the wellbore tool is first calibrated to take into account magnetic junk which is magnetically attracted to and accumulated on a magnet housing of the tool. To calibrate the tool, a new tuning frequency, called the Larmor frequency, is determined, and the tool is tuned to the new Larmor frequency before taking an initial measurement. The wellbore tool and the surface apparatus each include a processing system. Each processing system includes a memory. A first part of a tuning frequency determination software is stored in the memory of the tool, and a second part of the frequency determination software is stored in the memory of the surface apparatus. To determine the tuning frequency, the processing system in the wellbore tool initiates execution of the first part of the tuning frequency determination software. Results from this first execution are transmitted uphole to the surface apparatus. The processing system in the surface apparatus then initiates execution of the second part of the tuning frequency determination software. When this second execution is complete, the new tuning frequency, known as the Larmor frequency, is determined. The wellbore tool is then tuned to the new Larmor frequency.
申请公布号 US5451873(A) 申请公布日期 1995.09.19
申请号 US19930131644 申请日期 1993.10.05
申请人 SCHLUMBERGER TECHNOLOGY CORPORATION 发明人 FREEDMAN, ROBERT;SMAARDYK, JOHN E.;MACINNIS, JASON P.
分类号 G01V3/32;(IPC1-7):G01V3/00 主分类号 G01V3/32
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