Topics:

• Natural Resources
• Energy Resources
• What is petroleum?
• Origin of petroleum
• How is it found?
• Where is it found?

Everything around us was either:

• Grown
• Mined
• World economy is based on exploitation of natural resources

U.S. Energy Use

• Oil- 40%
• Natural gas - 28%
• Coal - 22 %
• Hydroelectric -5 %
• Nuclear - 4 %
•  

History

• Petroleum was known since Biblical times
• "And God said onto Noah . . . make yourself and arc of gopher wood; make rooms in the arc and cover it inside and out with pitch."Genesis 6: 13-14
• Modern petroleum industry started in the 1860’s in Pennsylvania and West Virginia
• At first main product was kerosene for lighting
• Gasoline was useless until the invention of the internal combustion engine

Oil & Natural Gas = hydrocarbons

• Petroleum
  • Crude oil
  • Natural gas
• Made molecules of carbon and hydrogen atoms
• Usually in chains or rings of carbon atoms
• Crude oil is a mix hydrocarbons
• Refineries: sort the hydrocarbons, break the chains and reshape them

Hydrocarbons

• Short chains (C1 to C10, chains with 1 to 10 carbon atoms)
  • Gases and light liquids
  • Natural gas to gasoline
• Medium length chains (C11-C18)
  • Heavier, more viscous liquids
  • Kerosene
  • Diesel
• Long chains (C19- >40)
  • Very viscous to solid
  • Motor oil
  • Tar

Origin of Petroleum

• Inorganic or Organic?
• Debated for many years
• Now most scientist agree on ORGANIC origin
• Oil forms from the decay and transformation of dead organisms (mainly algae) buried in sedimetary rocks

Factors required to make an Oil deposit

Source rock- rich in organic matter Burial heating-> maturation Reservoir rock- porous and permeable Trap-different geometries are possible structural traps (form in folded or faulted rocks) stratigraphic traps (form due to variation in stratigraophic facies and unconformities)

Source Rocks

• Black organic-rich marine shales
• Organic matter is preserved in low-oxygen water
• Restricted marine basins and zones were water rises from the deep are the most common setting

Maturation of Organic Matter

• Organic matter in sediments is solid (kerogen)
• At about 60 degrees Celsius transformation begins
• Liquid hydrocarbons begin to form
• At 120 degrees Celsius gas begins to form
• At 140 degrees Celsius organic matter is exhausted
• Only gas forms at higher temperature
• The maturation and migration process is very slow it takes 100's of thousands of years to form an oil deposit

Migration of oil

• Oil is less dense than water
• Oil will move up by buoyancy
• Oil needs a permeable rock to move (reservoir rock or migration pathway)
• It will stop when it reaches an impermeable bed (seal or cap rock)

Oil traps

Requirements:

• Permeable reservoir bed (sandstones and fractured limestones are the most common)
• Impermeable seal (shales and salt layers are good seals)
• A trap (the trap has a geometry such that the oil cannot move towards the surface any more)
•  

How is oil found?

• Search for the right geological conditions:
  • Sedimentary basins with rich source rocks
• Search for traps
  • It is very difficult to detect hydrocarbons directly
  • Traps can be found by:
    • Looking at the surface geological structures
    • Using seismic reflection surveys that image the sub-surface structure
    • Drilling

Where is oil found?

• Oil is not uniformly distributed over the Earth
• Subduction zones are generally bad settings for petroleum deposits
• Passive margins and the back side of fold-and-thrust belts (foreland basins) are best
• There are a few places where the geological history is such that all the ideal conditions existed for the formation of oil
• The largest oil deposits are in the Arabian Peninsula, Iran, and Irak
• Other rich petroleum provinces are:
  • Black Sea (former Soviet Union)
  • Gulf of Mexico (USA, Mexico)
  • Venezuela (South America)
  • Nigeria (West Africa)
  • North Sea (Northwestern Europe)
  • North Africa

 

Lecture 32- Energy Future

Reading: Chapter 21 and Lecture Notes

 

Topics:

• Reserves vs. Resources
• US production history
• Global oil supply
• Oil prices
• Non-conventional oil

How long will oil last?

• We don’t know exactly
• How do you measure something you can’t see?
• We are using oil faster than we are discovering it.

Resources vs. Reserves

• Resource:
  • Petroleum believed to exist on the basis of geological parameters
• Reserves:
  • Petroleum known to exist and which can be produced economically.

US Oil Production History

• The oil industry started in the USA
• The US is the biggest oil market
• The US is the best explored part of the world
• We can use the US history as an analogue for the rest of the world

Domestic Oil Production

• USA production (excluding Alaska) peaked in 1970 and has been declining since then
• Decline is inspite of better exploration and production technology
• Decline of US production is like that on a normal oil field

What about the future?

	Peak of oil discoveries was in 1962. Since then discovery of new reserves has been declining in spite of technological improvements. We are currently near the peak of production . This scenario implies that due to lack of new discoveries production will begin to decline by about 2010.
	You can’t produce oil that you have not discovered yet This allows us to forecast future production


The area under the discoveries curve and the production curve must be the same

Will we run out of oil soon?

• No, there is a lot of oil out there.
• However, demand is projected to exceed production at about 2010
• Then a shortage will develop and price will shoot up

What about the market place?

• Price of oil is tied to short term supply and demand
• Price of oil is deeply tied to global politics
• The price of oil determines how much exploration is done at any given time

Why did the price of oil increase in 2004?

• Global demand increased due to economic growth in China
• OPEC is producing at near full capacity (no spare capacity)
• There were lost of disruptions of the supply chain
  • Hurricanes in the Gulf, messy politics in Venezuela, unrest in Nigeria, war in Irak, etc
    
    

Are we sure about our forecast for the future?

• NO
• Resource is much greater than reserves
• Global reserves are very poorly known
• Countries routinely over-estimate reserves
  • Irak doubled its reported reserves in 1987 from 50 bbl to 100 bbl
  • Some companies over-estimate reserves to drive stocks up
• Reserves depend on economics
• Reserves = Petroleum known to exist and which can be produced economically
  • As price increases more expensive methods of extraction are possible

Non Conventional Petroleum Resources

• These could add a large amount to the resource base:
  • Tar sands
    • sand impregnated with heavy oil that can be mined
  • Shale oil
    • source rocks that never gave up their oil, they can be mined and cooked
  • Gas hydrates
    • methane-bearing ice found on the continental shelves
    • we don't know how to exploit it yet.
• As price increases technology to develop these resources becomes economical

Better efficiency will extend the life of the resource

 

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Lectures 33 and 34- Groundwater

Reading: Chapter 11 of Tarbuck and Lutgens, 8th edition

Topics:

1. Groundwater

2. Porosity and permeability

3. Water Table

4. Aquifers

5. Movement of groundwater

6. Streams and springs

7. Groundwater: a resource

8. Issues

9. Geothermal energy

 

Ground Water Glossary

GROUND WATER

• Water filling pore space, cracks & crevices in sediment and rocks
• Part of the hydrologic cycle
• There is greater volume of water in the ground water system than in lakes and rivers combined

Porosity and Permeability

• Porosity
  • % of rock or sediment that is open space
  • determiners the ability of the rock to hold water
  • Values range from 30% to 0% depending on compaction
• Permeability
  • ability to transmit water
  • Pore spaces must be connected

Rocks Properties

• Sandstone: Porous and permeable
• Shale: Porous but impermeable
• Limestone: Very variable, fractures and dissolution cavities can make it very permeable
• Basalt, granite, etc: Only permeable when fractured

Water table

• Saturated zone
• All pores filled with water
• Water table- upper surface of saturated zone
• Unsaturated zone (zone of aeration)
• Capillary fringe
• Water table is an extension of the surface water bodies

Aquifers

• Highly permeable rock layers that are saturated with water
• Good aquifers:
  • Sandstones, fractured limestones, etc
• Aquiclude
  • Impermeable layers
  • Shales, mudstones, etc.
• Unconfined aquifer
• Confined aquifer
  • bound above and below by aquicludes

Movement of ground water

• Moves in response to differences in water pressure & elevation
• Velocity influenced by
  • Slope of water table
  • Permeability of rock
• Think of a buried pipe filled with sand

Ground water and Streams

• Both are part of a single system
• Groundwater can contribute to stream flow
• Streams can recharge the groundwater system
• Sometimes rivers go underground into cave systems
• Gaining Stream - Receives groundwater
• Loosing Stream- drains into the Aquifer

Springs

• Found where the water table intersects the surface
• Fractures of fault systems serve as conduits from a confined aquifer to the surface
• Caves sometimes feed springs

Wells

• Objective: To drill an aquifer within the saturated zone
• Most of the subsurface is saturated with water so the questions are:
  • Rate of flow?
  • Quality of water?
• Water table rises and falls during seasons
• Recharge vs. discharge
• Cone of depression
  • Drawdown around a well
  • Water table drops around the well

Artesian Wells and Springs

• Confined aquifer
• Water will flow up to a level determined by the elevation of the recharge area
• Water can flow like a fountain driven by the pressure head

Groundwater: A resource

• Renewable or non-renewable?
• Depends. . .
• Eastern US:
  • Wet climate
  • Fast recharge
  • Renewable
• Southwestern US:
  • Semi-arid climate
  • Slow recharge
  • Non-renewable (at a human time scale)

High Plains Aquifer (0gallala aquifer)

• Underlies parts of the Dakotas, Nebraska, Kansas, Oklahoma, Texas, New Mexico, Colorado
  • 4,000 square miles
  • 13,000,000 acres irrigated
  • 18,000,000 acre-feet produced in 1980
  • 30% of the irrigation groundwater in USA

Recharge of the High Plains Aquifer

• Most recharge takes place in the Rocky Mts.
• Water levels in the aquifer have declined due to irrigation.
• Declines of water table:
• 25 feet in parts of Colorado
• 100 feet in parts of New Mexico
• Water pumped today in West Texas entered the aquifer 10,000 years ago

Groundwater Issues

• Rational use
• Surface subsidence
• Water quality
• Pollution of ground water

Rational Use:
Balancing Withdrawal & Recharge

• Overpumping results in:
  • Falling water table
  • Ground subsidence
  • Setting Priorities
• Biggest user: agriculture
• Does it make sense to grow thirsty crops in dry climates?

Pollution of Ground Water

• Pollutants
  • Pesticides & herbicides
  • Fertilizers
  • Heavy metals
  • Bacteria, viruses, parasites
  • Acid mine drainage
  • Radioactive waste
  • Gasoline
• Natural pollution
  • Seawater invasion

Hot Water Underground

Water heats up as it travels deep in the earth

• If it can come to the surface fast enough to retain its heat, a hot spring forms
• Hot springs
  • Near magma or cooling igneous rocks
  • Deep-circulating groundwater
  • Associated with faults
• Geothermal Energy
  • Hotsprings allow us to tap the internal heat of the Earth
  • An under-developed resource
  • Not so easy to harness, hydrothermal water is often corrosive

Revised 11/15/04