The predictive techniques are based on measurements that can be made at surface, such a geophysical measurements, or by analysing data from wells that have been drilled in nearby locations (offset wells). Geophysical measurements are generally used to identify geological conditions which might indicate the potential for overpressures such as salt domes which may have associated overpressured zones. Seismic data has been used successfully to identify transition zones and fluid content such as the presence of gas. Offset well histories may contain information on mud weights used, problems with stuck pipe, lost circulation or kicks. Any wireline logs or mudlogging information is also valuable when attempting to predict overpressures.