Sedimentary reading

Question 1

Sedimentary rocks are types of

Answer 1

rock that are formed by the deposition of material at the Earth’s surface and within bodies of water.

Question 2

Sedimentation is

Answer 2

the collective name for processes that cause mineral and/or organic particles (detritus) to settle and accumulate or minerals to precipitate from a solution.

Question 3

sediment

Answer 3

Particles that form a sedimentary rock by accumulating

Question 4

Before being deposited, sediment was formed by

Answer 4

weathering and erosion in a source area,

and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation.

Question 5

The sedimentary rock cover of the continents of the Earth’s crust is

Answer 5

extensive, but the total contribution of sedimentary rocks is estimated to be only 8% of the total volume of the crust

Question 6

Sedimentary rocks are

Answer 6

• only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.
• Sedimentary rocks are deposited in layers as strata, forming a structure called bedding.
• important sources of natural resources like coal, fossil fuels, drinking water or ores.
• may act as source rocks which generate hydrocarbons that accumulate in other sedimentary “reservoir” rocks

Question 7

The study of sedimentary rocks and rock strata provides information about

Answer 7

the subsurface that is useful for civil engineering, for example in the construction of roads, houses, tunnels, canals or other constructions

Question 8

Of particular interest in the petrochemical industry are

Answer 8

organic-rich sedimentary rocks, which are a specific type of sedimentary rock containing significant amounts (>3%) of organic carbon

Question 9

the most common types of organic rich sedimentary

Answer 9

• coal,
• lignite,
• oil shale, or
• black shale

Question 10

The organic material may be disseminated throughout the rock giving it

Answer 10

a uniform dark color, and/or may be present as discrete occurrences of

• tar,
• bitumen,
• asphalt,
• petroleum,
• coal or
• carbonaceous material.

Question 11

An important feature of reservoir rock to consider is its

Answer 11

external geometry

Question 12

The external geometry is defined by

Answer 12

seals or flow barriers that inhibit the migration of hydrocarbons, forming a hydrocarbon trap

Question 13

how does a hydrocarbon reservor form?

Answer 13

The buoyancy force produced by the difference in density between water and hydrocarbons drives migration. Migration will cease, and a hydrocarbon reservoir will form, only where hydrocarbons encounter a trap.