Origin of Oil and Natural gas
100 - 200 degrees
At what temperatures do most gas' form?
Most oils form between 50 to 100 degrees
At what temperatures do most oils form?
50 - 200 degrees
At what temperatures does petroleum form?
High temperature - low vidcosity = more easy to flow down gradient.
How can high temperatures aid migration of oil?
Sapropel is formed due to the partial decay of plankton via anaerobic bacteria.
How is sapropel formed?
A source rock, maturation, migration, a resevoir rock, a cap rock, a trap.
What are the 6 requirments to form economic accumalations of oil and gas?
All traps require the pressure of a porous and permeable resevoir rock overlan by a impermeable cap rock
What do traps require?
Dead plankton
What forms oil and gas?
Hydrocarbons denature and are destroyed
What happens above 200 degrees?
Below 50 degrees biogenic gas forms, but due to its shallow burial it is usually lost.
What happens at below 50 degrees?
A common misconseption is that oil and gas rise upwards because they are less dense than rock. instead it is because they are less dense than the water in the pore spaces
What is a common misconseption of oil and natural gas?
It is an organic rich sedimentary rock which can be black oil shales and mudstones.
What is a source rock?
Traps are where the geology allows oil and gas to be concentrated in one place, making them economic to extract.
What is a trap?
The environment of deposition must be low energy so that plankton can settle on the sea bed. conditions on the sea bed need to be anoxic so the plankton will not decay.
What must the environment be like so that oil and gas form?
Oil and natural gas originate in sedimentary basins
Where does oil and natural gas originate?
So that oil can migrate down a pressure gradient and percolate upwards till impermeable rock is reached.
Why must there be permeable rock between source and resevoir rocks?
Anticline traps, fault traps, salt dome traps, unconformity traps.
what are the four main traps?
The maturation process is where plankton is converted into petroleum by the effects of temperature and pressure during burial.
what is maturation?
Clay, mudstone, shale
what makes a good cap rock?
