Depositional Environments, Source Rocks, and Migration

Question 1

anoxic water

Answer 1

water depleted of dissolved o2 (less than 0.5 mg/L)

Question 2

when do anoxic conditions develop

Answer 2

where o2 demand exceeds supply

– Oxygen demand is caused by the degradation of dead organic matter.
– Oxygen supply is controlled by the circulation of oxygenated water.

Question 3

oxic environments

anoxic environments

Answer 3

lower quality of organic matter.

higher quality

Question 4

biological reworking is reworked by…

Answer 4

the absence of animal scavengers

restricted diffusion of oxidants into undisturbed sediment.

Question 5

upwelling

Answer 5

bringing nutrient rich deeper waters to the surface.

Question 6

Source rock

Answer 6

a fine grained, organic-rich rock that generates significant amounts of oil and gas e.g shale.

formed in quiet environments, deep down away from oxygen supplying o2

Question 7

Reservoir

Answer 7

any porous and permeable rock that contains large quantities of oil and gas; e.g porous sandstone, carbonate, and fractured shale. works hand in hand with source rock.

Question 8

Migration

Answer 8

the movement of gas and oil generated from kerogen within subsurface

Question 9

primary migration

Answer 9

the first phase of migration, whereby oil and gas are expelled from the source rock into the carrier bed

Question 10

secondary migration

Answer 10

the movement of oil and gas within the carrier bed

Question 11

what is required for effective secondary migration?

Answer 11

High permeability.

Question 12

what is required for accumulating oil and gas in reservoirs?

Answer 12

high porosity.