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:
Nov. 24, 1998
Filed:
Feb. 19, 1997
Christian Stoller, Kingwood, TX (US);
Nihal I Wijeyesekera, Stafford, TX (US);
Urmi DasGupta, Houston, TX (US);
Donald C McKeon, Katy, TX (US);
Peter D Wraight, Ridgefield, CT (US);
Schlumberger Technology Corporation, Houston, TX (US);
Abstract
The present invention is an improved method and tool for determining formation density by using an array of gamma-ray detectors. This invention can correct for large standoffs encountered in abnormally shaped boreholes and in particular for the increased standoffs typically encountered by mandrel tools. In this invention, the collimated detectors have varying depths of investigation into the formation. At small standoffs a short spaced (SS) detector investigates mainly the mud and mudcake and a shallow layer of the formation. Unlike the SS, a mid spaced (MS) detector has a deeper depth of investigation and is sensitive to borehole and formation even at increased standoffs. A long spaced (LS) detector is mainly sensitive to the formation density and its density reading is corrected by using the standoff information from the MS and SS detectors. In addition to measuring density, this invention can measure the photo-electric factor (PEF) of the formation. Because photo-electric absorption preferentially removes low energy gamma-rays, the tool housing needs to allow passage of low energy gamma-rays. This can be accomplished through the use of a window of a material with a low atomic number (Z) or through the use of a low-Z housing material like titanium. Typical window materials are beryllium and titanium. Housing materials can be titanium or for lower pressure requirements graphite or high-strength carbon compounds.