https://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Schematic_cross-section_of_general_types_of_oil_and_gas_resources_and_the_orientations_of_production_wells_used_in_hydraulic_fracturing.jpg/500px-Schematic_cross-section_of_general_types_of_oil_and_gas_resources_and_the_orientations_of_production_wells_used_in_hydraulic_fracturing.jpg