PNG 301
Introduction to Petroleum and Natural Gas Engineering

2.0: Lesson Overview



Petroleum and natural gas are found within the pore-spaces of porous rock which forms the crude oil and gas reservoirs. Typically, the oil and gas are found with saline water which may be mobile or immobile. This is in contrast to the popular belief that crude oil is found as “oceans of oil” in vast underground caverns. The pore-space in porous rock is identical to the pore-space found within the sand grains of beach sand.  If you were to dig a hole in the sand at the beach and fill it with ocean water, then that water would eventually drain out of the bottom of the hole and migrate through the sand back to the ocean.  Oil and gas storage and transport are identical to the storage and transport of ocean water in beach sand. In fact, the physical laws that govern the storage and transport of fluids in porous rock and unconsolidated sand are identical.

Learning Objectives

By the end of this lesson, you should be able to:

  • illustrate the types of geologic structures where crude oil and natural gas accumulate and/or exit;
  • list the five elements that are required to form a hydrocarbon reservoir;
  • describe the rock characteristics that are typically associated with hydrocarbons;
  • explain the process by which hydrocarbons pass from source rock to reservoir trap;
  • describe the geologic properties that make up a reservoir rock and what properties determine the commercial quality of the reservoir rock;
  • identify the four hydrocarbon types that make up crude oil and natural gas;
  • apply the Gibbs Phase Rule and explain how it governs the phase behavior of complex hydrocarbon mixtures;
  • explain how the local hydrostatic gradient and thermal gradient determine the pressure and temperature of a hydrocarbon reservoir at discovery; and
  • summarize how the location of the original pressure and temperature of the reservoir within the phase envelope of the phase diagram determines the type of crude oil or natural gas system that will be produced from the reservoir.

Lesson 2 Checklist

Lesson 2 Checklist
To Read Lesson 2: Origin and Occurrence of Hydrocarbons Click the Basic Earth Geology link below to continue reading the Lesson 2 material
To Do Submit the Lesson 2 quiz Located in the Lesson 2 module in Canvas

Please refer to the Calendar in Canvas for specific time frames and due dates.


If you have questions, please feel free to post them to the Course Q&A Discussion Board in Canvas. While you are there, feel free to post your own responses if you, too, are able to help a classmate.