LESA is a comprehensive, service company independent, interpretation system for open/cased hole logs, designed for a PC running under Microsoft� Windows�. Data input/output is from LAS/ASCII files (LIS may be imported through a conversion step). The system will accept English, Metric or mixed-unit input. Full shaley formation and complex lithology deterministic models are available, together with extensive core-log comparisons. For evaluation of oil and gas potential, both quick-look and in-depth analytic modules are included. Extensive on-line help is available, describing all interpretive procedures. User-defined routines and plots allow customized interpretation. Additional modules include time lapse neutron interpretation for gas storage, evaluation of coal bed methane potential, calculations of oil shale organic carbon content and multi-mineral analysis. LESA also has various command line options, DDE connections and OLE automation to allow the software to be linked to other applications.