Download Petroleum - Research at UVU

PETROLEUM
GEOLOGIC ORIGIN
General Requirements for Formation of Oil Deposits
• Source Rock - sedimentary rock rich in organic matter typically shale or limestone
• Thermal maturation and migration - Source rock is heated to 90 to 150oC to transform solid organic matter into liquid
hydrocarbon (oil and natural gas). The liquid oil then will rise upwards through the pore spaces of the rock, displacing the
water present in most of the overlying sedimentary beds. If the source rock is impermeable, the oil can remain there forming
oil shale.
• Reservoir Rock - Sedimentary rock in which oil accumulates; must contain abundant pore spaces and have relatively high
permeability; typically sandstone or limestone
• Seal Rock - Impermeable sedimentary rock that blocks upward flow of oil and prevents it from escaping the reservoir rock
layer; typically shale or evaporites (salt)
• Trap - Geometric arrangement of reservoir and seal rocks that cause significant amounts of oil to accumulate in one area [see
the figure below]
Specifics of Oil Formation in Middle East
• Shallow seas – the Tethys Sea - covered eastern Arabian Peninsula from Jurassic (200 million years ago) until Early Tertiary
time (35 million years ago).
• In Jurassic time, about 200 Ma (Ma means millions of years ago), limestone source rocks were deposited across the eastern
portions of the Arabian Peninsula.
• In Early to mid Cretaceous time, about 100 Ma, limestone reservoir rocks were deposited across eastern portions of the
Arabian Peninsula.
• In mid to late Cretaceous time, about 100 to 70 Ma, evaporate (salt and gypsum) rocks were deposited (on top of the reservoir
rocks).
• In Early Tertiary time, about 35 Ma, Iraq and the Arabian peninsula collided with Iran and the rest of Europe and Asia. The
collision caused the source, reservoir and seal rocks to slowly bend and become folded. These folds form the traps where large
amounts of oil have accumulated. The collision also caused the Zagros Mountains in Iran to begin to form, as well as the Alps
to the west (in Europe) and the Himalaya mountains to the East.
PETROLEUM CONSUMPTION AND RESERVES
• U.S. currently consumes over 7 billion barrels of oil per year; global use is about 28 billion barrels.
• Global reserves probably are 2 to 4 trillion barrels.
• Important question is how long can production rates keep up with demand (as opposed to “when will we run out of oil?)?
Hubbert Peak Theory predicts that global production rates probably will not increase a great deal in the future, and may even
be beginning to decline. This could have major economic and political consequences.
• Burning petroleum and fossil fuels in general at current rates is also a concern to many people due to pollution – both toxins
(“smog”) and CO2, which is the major cause of global warming. Humans release approximately 27 billion tons of CO2 into
the atmosphere each year. For example, burning 1 lb of gasoline produces about 3.1 lbs of CO2, and a gallon of gas weighs
about 6 lbs.
seal
source
GEOL 1010, M. Bunds, 11/09/2007
reservoir