The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 23, 1996
Filed:
Aug. 15, 1994
Robert Freedman, Houston, TX (US);
Christopher E Morriss, The Woodlands, TX (US);
Schlumberger Technology Corp., Houston, TX (US);
Abstract
When a pulsed nuclear magnetic resonance (NMR) well logging tool is traversing a wellbore, a NMR well logging method includes magnetizing the hydrogen nuclei in a formation traversed by the tool with a static magnetic field, waiting for a first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a first plurality of spin echo signals, waiting a second period of time W.sub.2 which is different from the first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a second plurality of spin echo signals, waiting a third period of time W.sub.3 which is different from both the second period of time W.sub.2 and the first period of time W.sub.1, energizing the formation with oscillating RF pulses, collecting a third plurality of spin echo signals, etc. The first, second and third, etc. plurality of spin echo signals corresponding to the different wait times are input to a signal processing apparatus disposed in the tool. Window sums of spin-echo signals are computed and transmitted uphole to a surface oriented signal processing apparatus. In response to the window sums, the surface signal processing apparatus determines an apparent formation T.sub.2 -distribution for each wait time in the multi-wait time pulse sequence. The apparent T.sub.2 -distributions are used to construct a cost function. When the cost function is minimized, the surface oriented signal processing apparatus determines estimates of the true T.sub.1 /T.sub.2 ratios and intrinsic T.sub.2 -distributions of the formations being logged. The surface signal processing apparatus uses the new T.sub.2 -distribution to generate new, more accurate, output record medium.