A2 Porosity and Fluids in Rocks

Question 1

Porosity

Answer 1

the volume of pore space.

Question 2

Permeability

Answer 2

the rate at which a fluid (usually water, oil or gas) flows through a rock.

Question 3

Capillary pressure

Answer 3

the pressure between two immiscible fluids in narrow pore spaces, resulting from interactions of forces between the fluids and the solid grains.

Question 4

Connate water

Answer 4

trapped in the pores of a rock as the rock formed. It includes water trapped in the original sediment and water released during diagenesis.

Question 5

Groundwater

Answer 5

water occupying pores and other spaces in rocks and sediments which is derived mostly from rainfall percolating into the underlying rock.

Question 6

Water table

Answer 6

the surface separating unsaturated rock above from saturated rock below.

Question 7

Hydrostatic pressure

Answer 7

the pressure at a point in a body of water due to the mass of the overlying column of water.

Question 8

Hydraulic gradient

Answer 8

the difference in hydrostatic pressure between two points divided by the distance between them.

Question 9

Aquifer

Answer 9

a body of porous and permeable rock capable of storing and yielding significant amounts of water.

Question 10

Recharge zone

Answer 10

the area of an aquifer open to the atmosphere, allowing replenishment of water.

Question 11

Artesian basin

Answer 11

a large, synclinal confined aquifer under hydrostatic pressure.

Question 12

Artesian wells

Answer 12

hold water under hydrostatic pressure, which rises up the well to the piezometric surface on release.

Question 13

Piezometric surface

Answer 13

an imaginary surface to which groundwater rises under hydrostatic pressure, to produce springs.

Question 14

Abstraction

Answer 14

the removal of water from any source.

Question 15

Cones of depression

Answer 15

occur when there is a lowering of the water table in the vicinity of a well, usually due to abstraction of water.

Question 16

Acid mine drainage

Answer 16

caused when water flows over or through sulfur-bearing materials, for example rocks containing iron pyrites. This causes acidification of the water by iron pyrites reacting with air and water to form sulfuric acid and dissolved iron ions.