Geologic ResourcesChapter 21

Oil Field in Wyoming

Geologic Resources and Earth’s Systems

• Geologic resources - valuable materials of geologic origin that can be extracted from the Earth– Many geologic resources originate in the hydrosphere

• Petroleum and coal come from organisms that lived and died in water

• Halite (salt) and other evaporite minerals come from dry lake beds

– Weathering interactions between geosphere, atmosphere and hydrosphere produce metal oxide ores

– Humans (biosphere) interact directly with the geosphere, hydrosphere, and atmosphere when extracting and utilizing geologic resources

– Groundwater (hydrosphere) is a renewable geologic resource

• If it can’t be grown, it must be mined

Types of Geologic Resources• Geologic resources are grouped

into three major categories:– Energy resources - petroleum

(oil and natural gas), coal, uranium, geothermal resources

– Metals - iron, copper, aluminum, lead, zinc, gold, silver, platinum

– Non-metallic resources - sand and gravel, limestone, building stone, salt, sulfur, gems, gypsum, phosphates, groundwater, etc.

Resources and Reserves

• Resources - the total amount of a valuable geologic material in all deposits, discovered and undiscovered

• Reserves - discovered deposits of geologic resources that can be extracted economically and legally under present conditions– The short-term supply of a

geologic materials

Energy Resources - Coal

• Fossil fuels (oil, natural gas, and coal) account for nearly 90% of U.S. energy

• Coal is a sedimentary rock that forms from the compaction of plant material that has not completely decayed– Forms from shallow burial and

compaction of peat

• Four varieties of coal– Lignite (brown coal) is soft and crumbly

– Sub-bituminous and bituminous coal (soft coal) • black and dusty

• burn with a smoky flame

• commonly strip-mined

– Anthracite (hard coal) • shiny and dust-free

• burns with a smokeless flame

• low-level metamorphic rock

• Burning of high-sulfur coal can produce acid rain; strip mines can scar landscape

• U.S. coal reserves could last for centuries

Energy Resources - Coal

Energy Resources -Petroleum

• Petroleum - oil and natural gas - occurs in underground pools

• Occurrence of oil pools requires:– A source rock (rich in organic matter)

– A reservoir rock in which it can be stored and transmitted (e.g., sandstone)

– An oil trap (set of conditions holding rock in reservoir rock and preventing migration)

– Deep enough burial (and sufficient time) to “cook” the oil and gas out of the organic matter

Structural Traps for Gas and Oil

2300 m – 4600 m = Oil formation4600+ m = Gas formation

Eroded anticline forms trap in Landers oil field in Wyoming.

Energy Resources - Petroleum

Other Oil Traps in Geological Structures

Petroleum Recovery

• Oil fields are regions underlain by one or more oil pools – Largest in U.S. are in Texas and Alaska

• Oil and natural gas are removed through wells drilled down into an oil trap within a reservoir rock

• Negative environmental effects resulting from oil recovery and transport include oil spills, brine contamination of surface water, and ground subsidence

Oil Peak, Oil Panic ?(Study by Amos Nur - Stanford)

U.S., Canada, Japan, Germany, France, Italy, UK, are the biggestconsumers of oil reserves worldwide.

Oil Peaks – 1960's

In the 1850's oil mainly used for kerosene lamps – remaining was burned or disgarded.

Current oil production rates peakedin 1960's but U.S. consumption ratesincrease dramatically above this.

Don't panic! -Try to conserve energy -Seek alternative energy sources

At current rate of use, worldwide oil reserves should last 30-40 years, and natural gas reserves somewhat longer (estimates from USGS)

Petroleum Reserves

Petroleum Reserves• As petroleum prices rise, alternate

petroleum sources, such as heavy crude, oil shale and oil sand, will be increasingly exploited

– Heavy crude is dense, viscous petroleum

– Oil shale is black or brown shale with high solid organic matter content from which oil can be extracted by distillation

– Oil sands (or tar sands) are asphalt-cemented sand or sandstone deposits

Jobs and Salaries in Geology

Starting salaries for petroleum geologists with 0-2 yrs experience.

Mixture of B.S. and M.S. Degrees.

Jobs and Salaries in Geology

Geologists in Environmental (e.g. EPA, Geotechnical firms) and Geologists in Government make $ 50 K – 75 K

Geology Ph.D. faculty starting salaries in 2007 ($70 K – 80 K)\

Metals and Ores• Metal ores - naturally occurring

materials that can be profitably mined

• Whether or not a mineral deposit is an ore depends on chemical composition, the percent extractable metal, and current market value of the metal

• Metallic ore deposits originate from crystal settling in igneous intrusions, hydrothermal fluids cooling in pores and factures, chemical precipitation in water, or sedimentation in rivers (placers)

Mining and Metals• Mining can be done at Earth’s surface

(strip mines, open-pit mines, and placer mines) or underground– Metals mined include iron, copper,

aluminum, lead, zinc, silver, gold and many others

• With care, negative environmental effects of mining, including unsightly tailings piles, surface scars, land subsidence, and acid mine drainage can be minimized

Non-metallic Resources

• Non-metallic resources - not mined to extract a metal or an energy source– construction materials

• sand, gravel, limestone, and gypsum

– agriculture • phosphate, nitrate and potassium compounds)

– industrial uses • rock salt, sulfur, asbestos)

– gemstones • diamonds, rubies, etc.

– household and business products• glass sand, fluorite, diatomite, graphite)