Certain knowledge impresses us in the way it affects our lives in significant ways. No other material resource affects us more, whether, physically, financially, socially, politically and psychologically, than oil does. Just what makes it so important? How is it formed? How is it derived?
Hydrocarbons (oil and gas) found in the Earth’s crust provide us with precious and powerful materials for the production and maintenance of so many aspects of human life, from light to energy to transportation and food production. Yet, even prior to the discovery and use of such materials, humans have lived for centuries, albeit in less convenient and less efficient manner.
Oil and gas have been the great game-changers in many facets of modern civilization. Aside from the physical and economic value they hold, they also affect our social and political environment in ways we cannot truly comprehend, especially so in recent contemporary events. It comes as no surprise that oil notoriously holds the other title of “black gold” – and we know that whoever holds the gold (black or otherwise) rules.
But behind the people who rule are people who make it possible for these rulers to understand and harness the secrets of oil and gas: where they are, how much they are worth and how to extract them at viable costs. The geologist and geophysicists are the first experts who have access to the knowledge of the oil hidden down there. Using advanced techniques and tools, they can determine deposits of oil and gas that the Earth has generated and hidden throughout the millennia.
Sedimentary rock strata are the usual source of oil and gas as they could contain organic materials which have been trapped in the long history of geologic processes. These porous rocks (which are solidified deposited rock fragments or silts that have accumulated on top of previous layers) can contain organic matters (dead plants, animals, tiny organisms) which are then subjected to temperatures that transform them into hydrocarbons. From 60 to 120o, oil is formed; while from 100-200o, gas is formed.
Shale, a form of sedimentary rocks produced in deep ocean or lake basins and, therefore, containing remains of organisms, is a rich source of hydrocarbons. On the other hand, shale, because It is made up of fine-grained sediments can also serve to trap hydrocarbon oil and gas or as a seal against migration of hydrocarbons.
Sandstone and dolomite can effectively serve as oil and gas reservoir because of their porous and permeable nature. Since oil and gas are less dense than the surrounding subsurface water, they tend to seep upward and eventually get trapped under shale caps or strata or find their way into the surface as oil seeps and natural gas leaks. Reservoir rocks are a rich source of accumulated oil that can run up to millions or billions of barrels a day in terms of oil-well production.