A New Method for Estimating Formation Water Rw Using NMR Logging Data

摘要

Saturation determination from a resistivity-based technique requires the information of formation water resistivity, Rw or, equivalently, the reservoir formation water salinity. If the reservoir salinity varies with depth, it is important that one has the capability of estimating salinity or Rw in-situ. We introduce a new method of estimating formation water salinity using NMR logging data. Specifically, we use the quality factor, Q, a quantity often used as a tool QC indicator, for estimating formation water resistivity. We describe the method of identifying the effects on Q due to instrument, formation, and the borehole. We also discuss the application envelope of this technique in terms of borehole environment and formation conductivity ranges. Examples are provided to demonstrate the efficacy of the technique.