SYSTEM AND METHOD FOR MEASURING BOREHOLE GEOMETRY WHILE DRILLING

摘要

A method and system for determining a geometry of a borehole includes forming an nuclear magnetic resonance (NMR) caliper with a plurality of coils and coupling the NMR caliper to a borehole assembly. The NMR caliper may be calibrated for porosity and the T2 of the drilling mud, prior to drilling, at the surface. After drilling commences, scans of the borehole may be conducted with each coil of the NMR caliper. Each scan may include propagating RF energy across a range of frequencies with each coil in order to excite a NMR signal at varying depths. Borehole wall distances from the NMR caliper may be determined by reviewing a plurality of T2 distributions from CPMG measurements derived from the scans. In some embodiments, borehole wall distances from the NMR caliper may be determined by reviewing porosity values derived from the scans.