Selective analysis of the surfaces of soil and sediment particles can be used to map hydrocarbon reservoirs deep in the subsurface prior to exploration drilling, substantially reducing the financial risk.  Similarly, mapping of reservoir boundaries can dramatically lower development costs, and  can reveal portions of  resources that may otherwise be overlooked.   Newly developed technologies  detect parts-per-trillion to parts-per-billion level shifts in the concentrations of  up to sixty-eight inorganic analytes.  Revolutionary Enzyme Leach^SM processes are used to remove  analytes from  surface coatings on sediment or soil grains.  Distinctive patterns that are revealed have been found to show both positive and negative apical and halo responses above hydrocarbon reservoirs.  These patterns are thought to be a result of the chemical contrast of accumulations in the subsurface.  Selective extraction patterns have provided valuable indications of hydrocarbon accumulations in a wide variety of geologic environments on several continents.  For example, Enzyme Leach^SM responses were key to the discovery at Talsinnt (50-100 MMBOE), northeastern Morocco.  Additionally, subsurface  faults have been mapped from surface based on the patterns of various critical trace elements.  For example, production from a gas field in the Gulf of Mexico is currently being evaluated, based on apparent structural patterns suggested by an offshore survey.