Accounting For Saturation Heterogeneity In Obtaining Estimate Of Water Content From Dielectric Data

Measurements of dielectric constant can be used to determine water content or saturation in<br>the vadose zone; estimates of these parameters are needed in modeling contaminant transport. If a<br>sedimentary system is a homogeneous mixture, the dielectric constant-water content or saturation<br>relationship can be described by the time propagation (TP) model. If the sedimentary system<br>consists of thin layers, effective medium theory (EMT) describes the system; whereas if the system<br>consists of thick layers, ray theory describes the system.<br>In this paper, we present a flow chart for determining water content and saturation from<br>field measurements. In this procedure we look only at binary (e.g. clay-sand) sedimentary<br>systems and assume that if layers are present they are parallel to the surface. Using dielectric<br>measurements taken perpendicular to the surface of the earth and measurements taken parallel, we<br>can determine whether the system is homogeneous or layered. We then use the dielectric<br>measurements and lithologic information determined from direct sampling to calculate the water<br>content and saturation of the system. This method not only gives the global water content and<br>saturation of the whole system, but also gives the water contents and saturations of the two<br>different sedimentary layers if they are present. We also present examples of the error that can be<br>incurred if this method is not followed and an incorrect relationship is used to interpret to dielectric<br>data.