Field Testing of a New Nuclear Magnetic Resonance Logging-While-Drilling Tool

Abstract

Abstract Downhole nuclear magnetic resonance (NMR) measurements are evolving into a powerful formation evaluation tool, providing unique and critical information including formation porosity, pore-size distributions, bound-fluid volume (BFV), free-fluid volume (FFV), permeability, and fluid properties. Obtaining this information while drilling can have a significant impact on drilling and completion decisions. In addition, low rates of penetration common in many drilling environments can be advantageous in improving the NMR measurement statistics. This paper describes results gained during field tests of a new NMR logging-while-drilling (LWD) tool that has been designed to run in any standard measurement-while-drilling (MWD) bottomhole assembly. The new tool presents no special operational complications in terms of mechanical specifications or wellsite hardware and software, and it has been tested successfully in both real-time and recorded modes in a wide range of formations and drilling conditions. A key consideration in the design of this tool has been to deliver an NMR measurement of wireline quality with a minimum of interference to the drilling process. To this end, the tool is usable in various modes of operation (stabilized, unstabilized, while drilling, while reaming, etc.). The detrimental effects of tool motion on the NMR measurement are minimized through the hardware design. Motion-effects modeling and log examples address these issues. Having the capability of acquiring data in the conventional T2 mode, this tool offers a familiar interpretation strategy for those users accustomed to evaluating wireline NMR data along with a significant advantage in statistical precision over a T1 acquisition mode.