A petroleum geologist is an occupation that involves all aspects of oil discovery and production in the field of petroleum geology

Petroleum geology

Petroleum geology refers to the specific set of geological disciplines that are applied to the search for hydrocarbons .-Sedimentary basin analysis:...

. Petroleum geologists are usually linked to the actual discovery of oil and the identification of possible oil deposits

Oil field

An oil field is a region with an abundance of oil wells extracting petroleum from below ground. Because the oil reservoirs typically extend over a large area, possibly several hundred kilometres across, full exploitation entails multiple wells scattered across the area...

 or leads. It can be a very labor intensive task involving several different fields of science and elaborate machinery. Petroleum geologists look at the structural and sedimentary aspects of the stratum

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

/strata to identify possible oil traps.

Profile

Petroleum geologists make the decision on where the location of drilling will occur. This is done by locating prospects within a sedimentary basin. Petroleum geologists determine a prospect’s viability looking at seven main aspects, according to the orthodox view of petroleum exploration:

• Source- The presence of an organic-rich source rock
  Source rock
  In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. They form one of the necessary elements of a working petroleum system. They are organic-rich sediments that may have been deposited in a variety of environments including...
  
   capable of generating hydrocarbon
  Hydrocarbon
  In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
  
  s during deep burial.
• Reservoir- The porous rock unit that collects the hydrocarbons expelled from the source rock and holds them inside a trap.
• Seal- The rock unit that inhibits the oil or gas from escaping vertically out of a hydrocarbon bearing reservoir rock .
• Trap- Structural or stratigraphic feature that captures migrating hydrocarbons into an economically producible accumulation.
• Timing- Geologic events must occur in a certain order e.g. that the trap formed before migration rather than after.
• Maturation- The process of thermal maturing of a source rock, leading to the cracking of its organic matter into oil and gas.
• Migration- The movement of the (less dense) oil or gas from the source rock into a reservoir rock and then into a trap.

These seven key aspects allow the Petroleum geologist to obtain a 1-dimensional idea of the subsurface.
Some other data may be obtained via Geophysical methods. Geophysical logs show the seismology

Seismology

Seismology is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,...

 data of elastic waves

Linear elasticity

Linear elasticity is the mathematical study of how solid objects deform and become internally stressed due to prescribed loading conditions. Linear elasticity models materials as continua. Linear elasticity is a simplification of the more general nonlinear theory of elasticity and is a branch of...

, mainly seismic reflection. This allows a 3-dimensional look of the trap, and source rock. More data may be obtained from the mudlogger, who analyzes the drill cuttings and the rock formation thicknesses.