Fossil fuels (coal, petroleum, natural gas)

In a typical oil and gas field, is most of the gas generated deeper than oil, or is the oil generated at greater depth than most of the gas?

Gas is typically buried deeper than oil.

Has the use of coal to generate electricity in the US increased or decreased in the past 50 years?

Increased

What is the most abundant compound in natural gas?

Methane

What percent of all oil used to date was consumed since Prof. Kelemen was born (1956, 61 years ago)?

95%

Why is it unlikely - impossible, or almost impossible - to find coal deposits in rocks that are more than 350 million years old?

Coal forms from organic plant material. Plants evolved about 250 million years ago

What is the main difference between the organic material that forms coal compared to the organic material that forms oil?

Coal forms from plant material, oil from micro organisms

Describe the formation process of fossil fuels. Give two examples specifying materials, required conditions, and time scale. What does that imply about fossil fuels usage?

Fossil fuels are formed by decayed organic matter accumulating in sedimentary rock and being subjected to progressively higher temperature and pressure as they are buried, which reduces the oxygen content, over a process of millions of years. Coal starts as peat and moves all the way towards anthracite as the plant matter is buried in conditions that escape oxidation (escape getting decomposed by organisms), buried in depths up to 4km (not deeper or they would be burned up by the heat). Oil faces similar conditions but it is made out of marine organisms and forms kerogen first. Because these processes take millions of years, the use of fossil fuels for energy is not renewable on any timescale meaningful to humans.

How do thermogenic maturation of oil and natural gas differ?

Gas maturation occurs at lower depth

Chemically speaking, what distinguishes high-grade coal from low-grade coal?

High grade coal has a higher C/O ratio than low grade coal

What is OPEC?

The Organization of the Petroleum Exporting Countries (OPEC) is a permanent, intergovernmental organization, created at the Baghdad Conference in Sept 1960

What are the differences between near surface (upper few 100 meters) and deeper formation of natural gas?

near surface gases are biogenic - it is produced by organisms that are decomposing other organic material (ie, swamp bubbles). Deeper formations of gas are thermogenic, created by chemical reactions in rocks without living micro-organisms - heat and pressure turn buried hydrocarbons into gas.

What are the limitations to where we might expect to find oil and natural gas?

Only between 1-4km depth; less than 400 million years old; in regions that are not extremely defaulted or reformed

What are the geological characteristics of oil source rocks?

Organic rich sediments formed from algal remains in deep lakes, formed from marine planktonic and bacteria, and formed from terrestrial plant material that has been decomposed by bacteria or fungi

List the geological features necessary for the existence of conventional oil reservoirs

1.5-3.5km depth; rocks less than 400 million years old.

What are typical depth intervals for thermogenic oil maturation? How does this guide scientists and economists in estimating the total amount of recoverable oil? What constraints can we place on the age of rocks likely to form source rocks for oil and gas?

1.5-3.5km. Less than 400 million years old. This can help figure out the total resources of oil because scientists can figure out where the rocks are that fit these criteria and estimate how much oil is there based on known reserves.

About how many coal-fired power plants are being completed in 21st century China: two per day, two per week, or two per month?

2 per week

In chemical terms, what happens during combustion of hydrocarbon fuels? Write an example chemical reaction for combustion of methane, CH4.

C + O2 = CO2 + energy. Carbon combines with oxygen in the atmosphere to create CO2 and energy. CH4 + 2 O2 = CO2 + 2 H2O + energy

What's a "creaming curve" in the context of oil and gas production? What is the relationship between creaming curves and energy returned on energy invested (EROI)?

CC = number of wells vs oil or gas produced from a given reservoir over time, the yield per well decreases, this reflects a decreasing EROI

What are two of the main gases released when fossil fuels are burned?

CO2, N2O, methane (CH4)

How have use of coal, oil, natural gas and nuclear energy sources changed in the US in the last 110 years and why?

Coal is no longer the most important fossil fuel as it was 110 years ago, mostly because of the critical importance of oil as a transportation fuel (for cars, planes, ships, etc). Coal has become decreasingly important for electricity generation as well since natural gas has become more available and cheaper. Natural gas and coal are now responsible for a similar amount of energy production in the US and gas is expected to increase as coal decreases. Nuclear energy increased rapidly in the US in the 1940s-50s, but has not grown significantly since the 1980s due to several accidents (Three Mile Island, Chernobyl) that led to people questioning its safety, and because the problem of storing nuclear waste has still not been solved in the US.

What distinguishes the buried material that ultimately produces coal from the material that ultimately produces oil?

Coal is plant-life buried terrestially. Oil is micro-organisms (usually marine) that are buried at the bottom of the ocean.

What is enhanced oil recovery?

Enhanced oil recovery (EOR) is the implementation of various techniques for increasing the amount of crude oil that can be extracted from an oil field.

How has this changed over the past 20 years? What are the advantages of horizontal drilling for oil & gas extraction?

Horizontal wells can cut across wider producing zones or multiple vertical oil reservoirs. Furthermore, separate directional wells can be directed from a single drill which decreases both environmental impacts (fewer rigs dotting the landscape) and costs.

What does Hubbert's curve predict?

Hubberts curve is an approximation of the production rate of a resource over time; it predicted that peak oil production in the United States would occur in the 1970s

What distinguishes the chemical conditions for formation of geological hydrocarbon resources from those for formation of carbonate deposits such as limestones?

Hydrocarbon resources can be formed via physical attributes like heat and pressure, while carbonate deposits are the result of a chemical reaction.

In a world in which almost all usable energy is derived from combustion of hydrocarbon fuels, what might place a quantitative limit on "technically recoverable resources" of hydrocarbon fuels?

Hydrocarbons are created much slower than they are used by humans; thus, eventually, because these resources are finite there will have to be a limit that runs out.

Why is it important for there to be very little oxygen present when fossil fuel forms?

If buried carbon is oxidized, it will form CO2 gas or solid carbonate minerals rather than oxygen-poor hydrocarbon fuels

In the lifetime of a really good petroleum reservoir, what methods are used to extract and collect oil? Why is Enhanced Oil Recovery (EOR) used for conventional petroleum reservoirs?

Initialyl drilling works fine and the oil gushes out. But this only gets 40%. So you need to use hydraulic fracture + pumping water/steam 1. oil comes out spontaneously, technical problem is to limit flow so that oil can be efficiently collected and stored 2. pumping is needed to pull oil up from depth 3. enhanced oil recovery methods are needed: heating to reduce viscosity, hydraulic fracture to increase permeability, injection of water, CO2 to "push" oil toward and up a production well

Is there oil beneath the seafloor in the deep ocean basins far from continents? Why or why not?

No, because the accumulating dead plankton's keep getting subducted away.

What is a petroleum reservoir rock? What physical characteristics are required to form and preserve a conventional petroleum reservoir? What is a petroleum source rock?

Reservoir rocks are rocks that petroleum has migrated to from source rocks and usually is trapped in. Reservoir rocks must be porous and permeable, like limestone and sandstone. It is relatively easy to extract oil from reservoir rocks because it is close together and not super viscous. In petroleum geology, source rock refers to rocks from which hydrocarbons have been generated or are capable of being generated. These are sedimentary rocks rich in organic matter which has been generated in small, dispersed amounts.

Name the two countries listed in the textbook with the highest proven oil reserves

SA, Canada

Why did the proportion of total primary energy production from coal decline relative to oil? Why is the proportion of energy production from gas increasing in this century, relative to oil?

Shifting market prices (oil is cheaper than coal; natural gas has become cheaper than oil) and emissions regulations that discourage energy generation from coal and oil

What is thermal maturation of hydrocarbon fuel resources? How does this relate to the depth of burial of hydrocarbons? How does this influence estimates of "total recoverable resources"?

Thermal Maturation is when light fractions have been driven off or converted to gas due to natural heating. Based on the depth of burial for hydrocarbons, their surrounding temperature is different, so their ability to heat naturally is different.

About how many coal mining deaths were there per year in China in the 21st century up to 2013 (to the nearest order of magnitude)?

Thousands per year