Application of multirate flowing fluid electric conductivity logging method to well DH-2, Tono Site, Japan

In the flowing fluid electric conductivity (FEC) logging method, well bore fluid is replaced with deionized water, following which FEC profiles in the well bore are measured at a series of times while the well is pumped at a constant rate. Locations where fluid enters the well bore show peaks in the FEC logs, which are analyzed to infer inflow strengths and salinities of permeable features intersected by the borehole. In multirate flowing FEC logging, the flowing FEC logging method is repeated using two or more pumping rates. The results, coupled with those of a conventional well test over the entire borehole, enable the transmissivities and inherent pressure heads of permeable features to be determined. Multirate FEC logging is carried out on a deep borehole in fractured granitic rock using three different pumping rates. Results identify 19 hydraulically conducting fractures and indicate that transmissivity, pressure head, and salinity vary significantly among them. Using three pumping rates rather than the minimum number of two permits an internal consistency check on the analysis that provides a measure of the uncertainty of the results. Good comparisons against static FEC profiles and against independent chemical, geological, and hydrogeological data have further enhanced confidence in the results of the multirate flowing FEC logging method.