A robust nuclear magnetic resonance workflow for quantitative determination of petrophysical properties from drill cuttings

Determination of petrophysical parameters from surface measurements of drill cuttings, rather than well logs, has long been a subject of interest in the petroleum industry. Analysis of cuttings is presently included in mud logging workflows, although the methods employed tend to be labor-intensive and inefficient with an emphasis on qualitative lithological and mineralogical descriptors. Nuclear magnetic resonance (NMR) has the potential to deliver rapid formation evaluation at the rig site for near-real-time completion decisions. Despite numerous efforts to demonstrate NMR cuttings analysis, dating back to the 1980s, the technique has yet to achieve commercial success. We suggest this failure is due not to the physics of the measurement, which is understood, but rather to inadequate sample preparation. By centrifuging brine-saturated cuttings from conventional formations under a per-fluorinated oil, and using multinuclear NMR to measure liquid volumes, we obtain accurate porosity and permeability values independent of other measurements. Our robust workflow removes the inconsistencies associated with manual sample preparation. We present two case studies and the important requirements for handling actual drill cuttings.