Energy Resources

Question 1

What is a source rock

Answer 1

Organic-rich mudstone or shale containing abundant plankton that formed in low-energy, anoxic, marine conditions

Question 2

What is maturation

Answer 2

Process where plankton is converted into petroleum by temperature and pressure during burial

Question 3

What is migration

Answer 3

The movement of petroleum from a source rock to a reservoir rock

Question 4

What is a reservoir rock

Answer 4

Highly porous and permeable rock capable of storing and yielding significant amounts of petroleum

Question 5

What is a cap rock

Answer 5

Impermeable rock on top of reservoir rock preventing migration

Question 6

What is a trap

Answer 6

Geological situation that concentrates petroleum in one place

Question 7

What are the types of traps

Answer 7

Anticline 
Fault
Slat dome
Unconformity
Lithological

Question 8

How can oil and natural gas be destroyed or lost from traps

Answer 8

Heat from an igneous intrusion
Regional metamorphism where temperatures are high
Burial where the geothermal gradient results in temperatures higher than 200 degrees

lost if:
Erosion and removal of the overlying cap rock
Escaping upwards along an unsealed fault plane

Question 9

Seismic reflection surveys

Answer 9

Artificial seismic waves are generated by explosions or vibrations inland and by air guns in water or land by which they drop heavy thumper mounted on a truck

The waves travel through the earth and are reflected at layer boundaries within sedimentary sequences

The waves reflect and are detected by an array of receivers called geophones or hydrophones

The time taken for the reflected waves to arrive back at the receivers is called the travel time this can be used to calculate the depth

Question 10

Gravity surveys

Answer 10

Instrument called a gravimeter measures small variations in the earths gravitational field strength, the gravity data is corrected for the affects of latitude, altitude and topography leaving the variations resulting from the underlying rock types

Maps are plotted

Negative means slat one

positive means anticline or uplifted block bounded by fault

Question 11

Mud logging

Answer 11

Rock chips are brought to the surface in the drilling mud and are examined, shows fossils, rocks types present at different depths

Question 12

Down-hole logging

Answer 12

Porosity
Gamma ray spectroscopy
Resistivity
mounted on a sonde

Question 13

What is primary recovery

Answer 13

Only 20-30 percent can be recovered

drill into the reservoir rock

Question 14

What is secondary recovery

Answer 14

60 Percent can be recovered
Techniques include
Gas cap drive - Natural gas, co2, NO
Thermal methods such as steam injection
Detergents and other chemicals are used to reduce the surface tension of the oil
Bacteriological - Digest and breakdown large hydrocarbons

Question 15

What are the two main types of storage facilities for gas underground

Answer 15

Depleted oil and gas reservoirs, 50 percent must be full to maintain the pressure
Salt caverns these are ideal because the are impermeable

Question 16

North Sea oil and gas

Answer 16

Main source rock is Jurassic Kimmeridge Clay

Southern North sea only contains natural gas so no oil,

Question 17

Unconventional petroleum

Answer 17

Sources include
oil shales
tar sands
Coal-Bided methane

Question 18

Climatic and environmental conditions for the formation of peat and coal

Answer 18

Land plants
Anoxic environment
Rapid burial

Question 19

Coalification

Answer 19

Peat undergoes diagenesis due to the effects of heat and pressure during burial - this is called Coalification
As peat undergoes thermal maturation the weight of the overburden squeezes water and other volatiles out

Question 20

Coal series of increasing rank

Answer 20

Peat - Lignite - Bituminous coal - Anthracite

Question 21

Coke

Answer 21

Coal is used to make coke this is then used in blast furnaces to produce iron and steel

Question 22

Open cast coal mining

Answer 22

Takes place at the surface
Sides and dug at angles to prevent collapse, the angle size depends on
Rock type
Weathering
Structures such as faults and joints

Question 23

What is an adit

Answer 23

A horizontal tunnel dug into a hillside

Question 24

What is longwall mining

Answer 24

Highly mechanised method of underground mining

Question 25

Long wall mining

Answer 25

Main method of underground coal mining
A main shaft is dug from the surface and tunnels or roadways and driven out for the shaft
In long wall retreat mining - Two horizontal roadways are driven out to the furthest point of the area of coal to be extracted a coal face is established
between the two roadways
A shearer moves to and from the coal face cutting the coal, the coal falls onto a conveyor and is transported to the surface

Question 26

Where does geothermal energy come from

Answer 26

Release of stored gravitational energy from the formation of the earth
Radioactive decay of heat producing elements such as uranium and thorium

Question 27

Methods of geothermal energy extraction

Answer 27

Volcanic sources - Groundwater trapped in a similar way to oil and gas, pressure stops it from boiling so it becomes super heated
Borehole is drilled down into the rock, as the water rises up the borehole to reduced pressure causes it to flash and turn into steam and that can be used to turn turbines to generate electricity

Geothermal aquifers - Hot water is pumped to the surface passed through a heat exchanger and used for heating and hot water supply, the cold water is then injected back to maintain the pressure

Hot dry rock sources - Granite intrusions contain a higher concentration of radioactive elements. Paired boreholes are drilled into the granite, the granite is fractured and cold water is pumped down one borehole, heated by the rocks then rises up the second borehole