ELECTRICAL-CONDUCTIVITY OF STEAM-FLOODED, CLAY-BEARING GEOLOGIC MATERIALS

The effect of clay content on the electrical response of steamflooded geologic material is studied using a combination of laboratory experim ents and numerical simulations. The presence of clay can increase the conductivity of a steam zone by providing a surface conduction path th at is enhanced strongly by temperature increases. Clay also increases the residual water saturation in a steam zone, further increasing cond uctivity. These effects can result in steam zones that are more conduc tive than initial conditions. However, the presence of clay alone is n ot sufficient to make all portions of a steam zone conductive relative to initial conditions. Equally important to the electrical behavior i s the fluid response of the reservoir to the injection of steam. In pa rticular, the speed of the steam front, relative to the speed of the l iquid water in the steam zone, plays a key role. Relatively fast-movin g steam fronts cause distilled water banks to form around the front. T his leads to steam zones with electrically resistive forward sections, even in clay-rich material. The rear sections of these steam zones ca n be either resistive or conductive, depending in part on the clay con tent and the salinity. Relatively stow-moving steam fronts do not caus e distilled water banks to form and allow the formation of steam zones that are completely conductive relative to initial conditions. These experimental results demonstrate the potential complexities in steam-f lood electrical data. The numerical method used in this study can be u sed to help interpret those complexities.