Resistivity measurements have clearly outlined the lateral limits of the Broadlands field to depths of about 1 km. Temperature profiles in 31 wells about 1 km deep show a pattern in good agreement with the reservoir boundary outlined by the resistivity measurements.

Locating zones of enhanced permeability is an important requirement but has proved a more difficult task. Measurements of the resistivity anisotropy at about 0.5 km depth show a reasonable correlation with flow rates in one area. Two areas where very high temperatures (>260°C) are measured at all depths are interpreted as being places where upwellings of hot source water may be rising through deep permeable channels.

Gravity anomalies indicate that the depth of the graywacke basement rocks ranges from 1 to 2 km across the field and that there are areas of enhanced near-surface density which coincide with long-term discharge paths.