An Interpretation of Various Well Logs Acquired In Unconsolidated Soil for Hydraulic Property Estimation

In order to obtain some parameters for hydraulic property estimation, we carried out various well loggings, including velocity (Vp, Vs), electric, induction, IP, density, natural gamma, water conductivity, and temperature. This time, we considered a simple sand-clay model and tried to estimate its hydraulic conductivity from well logs. In this process, we recognized that the grain size or pore size crucially affects hydraulic conductivity if we calculate it from porosity by such kind of Kozeny-Carman equation. Although the natural gamma log is commonly used for discriminating sand and silt formations, we could not use it, because not all part of high gamma zone of the well corresponded to clay rich zone. Therefore, we examined a possibility of discriminating sand and clay by fuzzy clustering techniques (Imamura and Nakayama, 1997). The computed soil classification by fuzzy clustering using following three logs: conductivity, P-velocity, and density, showed good agreement with the soils determined by core observation. Among these three logs, we tried to apply conductivity log as an indicator of content of small particles. Using the conductivity log, we calculated pseudo clay content log and average grain size of sand-clay mixture. The calculated average grain size and porosity were substituted to Kozeny-Carman equation, and then hydraulic conductivity could be estimated. The estimated hydraulic conductivity was consistent with that measured by slug test and EKL deeper than 50m depth.