G.R. Coates, M. Miller, M. Gillen, and C. Henderson
NUMAR Corporation
ABSTRACT
Nuclear magnetic resonance technology is one of the frontiers of physics available to well logging that has intrigued researchers for more than 25 years. A new MRIL logging system is now available which employs the magnetic resonance imaging technology principles that have been evolving most noticeably in the medical world.
The tool introduces the first spin echo logging system, which features a proprietary gradient static magnetic field in combination with a RF magnetic field. This results in eliminating the need for any special borehole treatment and allows measurements of NMR information an order of magnitude in time earlier than previously possible. Such a system also allows a unique DC determination of fluid diffusion coefficient which can be used to characterize the type of fluids present and their mobilities.
The new MRIL system provides a new “sand-size” porosity, a bulk volume of irreducible porosity utilizing the free-fluid concepts, and a link to the permeability of the rock. The values are independent of the common, non-clay size minerals as will be shown by examples from the Conoco research characteristics.
This paper reviews some of the tool’s measurement principles and their link to these petrophysical properties. It then shows the log’s repeatability qualities and other measurement attributes followed by an in depth comparison to the other will logs on this well as well as to the core information.
Petrophysics, Geologists, and Engineers should all find this information useful in assessing the merits of this tool and it’s potential for answering theft needs in evaluating reservoirs for production qualities.