The science of petroleum geology is at the heart of D & L Energy Group's oil and gas exploration arm & L Energy, which drills primarily within the Appalachian basin. D & L Energy's petroleum geologists are highly selective, searching for quality reserves of oil and gas. These "traps"-layers of subterranean rock that form reservoirs for oil and gas-may be stacked vertically, creating oil and gas reserves at several depths. To determine what is beneath the surface, the geologists study other wells in the area along with seismic data gathered from sound-transmitting and reflecting properties of different types of rock formations.

In seismic surveys, the sound-wave source may be a small explosion in a shallow drilled hole or vibrating steel pads. Geophones record the sound waves intensity and time of arrival at various locations as they travel and reflect back through underground rock. Using computers, seismologists interpret the records to map the underground formation contours and determine whether an area contains enough oil and natural gas to warrant drilling.

Before drilling can begin, mineral leases must be obtained. Landowners in the United States hold both surface rights and mineral rights to their property, but may agree to sever or divide those rights. After a minerals agreement has been signed, the title is cleared for oil and natural gas to be extracted from the property. An attorney must review all historic documents, abstracts, conveyances, and current agreements.