Unit 4 - Energy from Fossil Fuels

Question 1

Define the terms joule and watt. How do these measurements relate to one another?

Answer 1

A joule is the electrical energy needed to maintain a flow of one ampere for one second at a potential of one volt; a watt is a unit of power defined as the consumption of one joule of electrical energy per second.

Question 2

Why did the British begin using coal as their main energy source soon after the onset of the Industrial Revolution?

Answer 2

Soon after the beginning of the Industrial Revolution, it became apparent that wood could not meet the rapidly expanding needs for energy: the demand for wood was threatening to deforest Britain.

Question 3

Where, according to Craig, Vaughan, and Skinner, will the Fossil Fuel Era fit into human history?

Answer 3

The period from about 1880 to about 2100–2200 AD will probably be called the Fossil Fuel Era.

Question 4

List, in decreasing order of importance, the energy sources used by most industrial nations today.

Answer 4

The energy sources used by most industrial nations (in decreasing order of importance) are natural gas, crude oil and lease condensate, coal, hydropower, nuclear power, and “other” sources.

Question 5

What percentage of the organic matter produced is geologically preserved?

Answer 5

Only about one per cent of all organic matter is geologically preserved as hydrocarbons.

Question 6

Which sediment source accounts for the largest percentage of organic carbon found within the Earth? Which accounts for the least?

Answer 6

The largest source of organic hydrocarbon (by far) is tied up in mudrocks and siltstones. Fossil fuels (coal, oil shales, oil, gas) and living organic matter, combined, account for the least.

Question 7

What is swamp gas, and how does it form?

Answer 7

What is commonly called organic swamp gas is actually methane gas. It forms as the primary product of the metabolism of bacteria, fungi, and other micro-organisms as they act on organic matter buried at shallow depths.

Question 8

Identify the major similarities and differences among fossil fuels.

Answer 8

All fossil fuels are chemically composed of hydrocarbon molecules. They differ in the arrangement and sizes of these molecules and in the differing ratios of hydrogen to carbon content.

Question 9

What is the difference between humic coal and sapropelic coal?

Answer 9

Most coal is humic coal, composed of organic material from angiosperms that have gone through a peat stage. Humic coal contains macerals. Sapropelic coal is composed primarily of spores and fine-grained algal debris that collected in oxygen-deficient ponds, lakes, and lagoons.

Question 10

What conditions are necessary for coal to accumulate and develop?

Answer 10

For coal to develop, organic debris must accumulate in swamp-like conditions where stagnant, oxygen-poor water inhibits the decomposition and oxidation of dead plant material. The resulting layer of peat must be buried by sediments to great depths, where pressure and heat transform the peat into coal. Coal beds are most commonly located in former low-lying, coastal swamps that were subjected to a cycle of inundation and emergence from a shallow sea over long periods of time.

Question 11

Why are temperate, not tropical, climates most favourable to peat production?

Answer 11

In tropical climates, plant material is totally consumed by bacterial action, leaving none for peat formation. In temperate to cold climates, there is enough precipitation for abundant plant growth, but the cold temperatures inhibit bacterial growth.

Question 12

In which geological periods was peat production (responsible for present-day coal deposits) most prolific?

Answer 12

Peat production was greatest in the Late Carboniferous (Mississippian) and Permian periods, between 310 and 232 million years ago.

Question 13

Define coalification.

Answer 13

Coalification is the process that turns peat into coal. It basically involves the action of heat and pressure on the organic matter or peat.

Question 14

List the ranks of coal in increasing order, and describe the most important chemical change that results in coal of the highest rank.

Answer 14

The textbook lists peat as the lowest order of coal. However, this is misleading, as peat is not a type of coal, but merely the first stage in the formation of coal. The actual order should read: lignite (or brown coal)—bituminous coal-anthracite. The most important chemical change from the lowest order to the highest order involves a progressive decrease in oxygen and hydrogen content, and a resulting increase in carbon content. As the carbon content increases, more and more recognizable plant remains change into shiny black macerals.

Question 15

Which method (other than direct combustion) is being researched as a future use for peat as an energy source?

Answer 15

Researchers are exploring the conversion of peat into methane gas by bacterial digestion or by thermal breakdown at 400–500 °C.

Question 16

Which are the major coal producing regions in Canada?

Answer 16

The major coal producing regions in Canada are in central and southern Alberta and southern Saskatchewan. In these areas, the coal occurs in easy-to-mine, sub-horizontal seams that lie just below the Earth’s surface. Deposits of coal that lie deeper are found in the foothills and mountains between Alberta and British Columbia. The thrusting associated with mountain-building in this area has produced coal seams with steeply dipping structures. Coal is also produced in eastern Canada at the Sydney coalfield in Nova Scotia and at the Minto coalfield in New Brunswick.

Question 17

Why is it easier to mine coal in the Rocky Mountains by open-pit methods rather than underground techniques?

Answer 17

The coal deposits in the Rocky Mountains between Alberta and British Columbia are difficult to mine by underground methods because the thrusting associated with the orogenic activity resulted in displacement and breaks in the coal seams. The coal seams are also often inclined because of the thrusting, so it is easier to extract the coal by open-pit methods than by underground techniques.

Question 18

What are the six main stages that the Canadian coal mining industry goes through in exploiting coal resources?

Answer 18

The six main stages that the Canadian mining industry goes through in exploiting coal resources are

1. exploration: deposits are identified and assessed;
2. the development stage: an inclusive consultation process that receives input from economic, environmental, government, and local communities;
3. the mining stage: entails the extraction of the coal and reclamation of affected land;
4. the coal processing stage: a continuation of the mining stage;
5. the transportation stage: the shipment and distribution of coal to the market; and
6. coal use: coal is used by power plant operators, industry, (e.g., cement makers), pulp and paper manufacturers, and steel plants (to name a few).

Question 19

What caused a drop in demand for Canadian coal between 1950 and 1960, and what developments ended this downturn?

Answer 19

Between 1950 and 1960, the discovery of crude oil in Alberta led to a downturn in the demand for Canadian coal. Railways, which had been the largest consumer of coal, suddenly switched to diesel-powered locomotives; by 1960, coal only contributed about twenty per cent of Canada’s energy supply.
After 1960, Japan began importing increasing quantities of Canadian coal. Power supply companies also commissioned new plants that used coal as an energy source. These developments caused a steady rise in the demand for coal. By 2001, the coal industry had grown by over 500 per cent.

Question 20

Describe the various by-products of the coking process. How is coke used in a blast furnace?

Answer 20

To make coke from coal, coal is pulverized and then heated to temperatures of up to 700 °C. This process expels moisture, gases, oils, and coal tar. About 70 per cent of the original coal remains, constituting a porous material called coke. Ammonia, light oils, and coal tar are separated from the hot gases emitted by the coking process. The ammonia is used to manufacture fertilizers while the oils and tars are used in producing a range of organic solvents and fertilizers. The remains of the hot gases are used as fuel in blast furnaces.
Coke used in a blast furnace has three main functions. First, in burning, it provides the high temperatures needed to melt iron ore. Second, it provides the carbon monoxide necessary to reduce iron ore to metallic iron. Finally, it provides a strong physical structure through which the air blast and reducing gases can move evenly up through the iron ore, allowing molten iron ore to drain to the bottom of the furnace.

Question 21

What oil discovery is generally recognized as the beginning of the modern oil industry?

Answer 21

The first American oil well is generally recognized as the beginning of the modern oil industry. It was drilled at Titusville, Pennsylvania in 1859, by Edwin Drake.

Question 22

How do petroleum and natural gas differ in origin and composition?

Answer 22

Petroleum forms almost exclusively from the organic matter in marine sediments, while natural gas can form in both marine and terrestrial rock. Petroleum consists of many different hydrocarbon compounds, whereas natural gas is mainly (often ninety-nine per cent) composed of methane.

Question 23

What is the principal difference between the organic material that forms oil and that which produces coal?

Answer 23

Petroleum and natural gas form from the remains of floating planktonic organisms (phytoplankton and zooplankton) that are constantly deposited on the ocean floor. This organic material is rich in lipids (fats), proteins, and carbohydrates. Coal forms from terrestrial plant remains that contain a large percentage of cellulose and lignin (woody tissue).

Question 24

Outline the stages of oil and gas formation in marine sediments.

Answer 24

Diagenesis occurs from the surface of the ocean floor to depths of several hundred metres, where temperatures rarely exceed 50 °C. Much of the organic matter is oxidized or consumed by burrowing organisms or bacteria; these processes release considerable amounts of biogenic gas. Below this region, catagenesis takes place to depths of three and one-half to five kilometres, where pressures can reach 1500 bars (1 bar = 100 000 Newtons per square metre = approximately 1 atmosphere) and temperatures range from 50–150 °C. Here, sediments are compacted into rock, and most of the water is squeezed out. The organic matter is converted to kerogen, and produces liquid petroleum. While biogenic gas-producing processes increase, gas forms by thermal cracking of some of the kerogen. As depth, pressure, and temperature continue to increase, petroleum production ceases and gas production dominates. At temperatures higher than 150 °C and pressures greater than 1500 bars, metagenesis occurs, producing nearly pure methane and a carbon-rich residue. Below these depths carbon metamorphosizes into graphite.

Question 25

Compare textbook Figure 5.33 (p. 152) with Figure 5.11 (p. 134). In terms of geological time, what is the principal difference between the abundance of oil and gas reserves and that of coal reserves?

Answer 25

Major coal reserves were formed during the Late Carboniferous (Mississippian) and Permian periods, while the oil and gas reserves are found in rock of more recent age. Coal is found mainly in older rock, because the geological periods when coal began forming were characterized by the repeated advance and retreat of shallow seas over low-lying land areas. Oil and gas reserves generally increase with more recent geological times partly because plankton populations (from which they are produced) have steadily increased. Remember, however, that once oil and gas form, they tend to migrate towards the Earth’s surface until they become trapped in rock structures or dissipate at the surface.

Question 26

What three methods are commonly used to increase the flow of oil through reservoir rock?

Answer 26

One method used to increase the flow of oil through reservoir rock is to inject strong acid solutions down the borehole to dissolve the natural cement (usually calcium carbonate) that binds the grains together; this makes the reservoir rock more permeable. Another method is to pump water and coarse sand under great pressure down the borehole to fracture the rock. In some cases, high calibre bullets or small explosives are used to fracture the rock near the well (a third method).

Question 27

Describe the principle of primary recovery from an oil well.

Answer 27

The three natural processes used in the primary recovery of petroleum are water drive, gas expansion, and evolution of dissolved gas. In many structural traps, the oil is overlain by natural gas and underlain by water. In the water drive process, the water, which is usually under pressure, pushes the oil up the pipe into the oil portion of the trap. The gas expansion process uses the overlying gas as a propulsion agent. As the petroleum begins to flow up the well, the reduced pressure allows the gas to expand and force the oil upwards. Finally, as pressure decreases, gas (which is dissolved in the oil) comes out of solution, applying pressure to the oil.

Question 28

Describe the secondary recovery techniques for oil.

Answer 28

Secondary, or artificial, recovery techniques include water flooding, steam flooding, and chemical flooding. In water flooding, a second borehole is drilled at a strategic location opposite the oil recovery well, and water under high pressure is forced down and through the reservoir, pushing some of the remaining oil in front of it. Steam flooding uses the same technique. The steam heats the oil, making it less viscous, and causes it to flow up the recovery well. Chemical flooding uses chemicals, often detergents, to loosen oil adhering to the rock, much like dish soap lifts grease off dinner plates in a kitchen sink.

Question 29

Describe the steps involved in refining petroleum.

Answer 29

Refining petroleum involves two steps: distillation and cracking. In distillation, crude oil is heated to nearly 500 °C and then slowly cooled, causing the various hydrocarbons to arrange themselves according to condensation temperatures. Each product locates itself in the refractor at a specific level.
As the demand for gasoline increased, heavy hydrocarbons needed to be broken into lighter ones; this is called cracking. Thermal cracking uses heat and pressure; catalytic cracking uses a catalyst, usually a synthetic zeolite mineral, that speeds and facilitates the process.

Question 30

Why did Dr. M. King Hubbert’s 1948 prediction concerning world oil production fail to come true?

Answer 30

The OPEC oil embargo of 1973 created an “oil crisis” and a reduction in world oil consumption that persisted long afterwards. Dr. Hubbert did not foresee this.

Question 31

What is a hydrocarbon trap? What are the three basic prerequisites for an effective hydrocarbon trap?

Answer 31

Rocks that stop hydrocarbon migration and allow their accumulation are called hydrocarbon traps. An effective hydrocarbon trap requires three basic features:

A. a porous rock to hold the oil or gas. Sandstones and limestones usually form good trap rocks;

B. an impermeable rock overlying the hydrocarbon host rock, to prevent escape of hydrocarbons;

C. a source of hydrocarbons that can become trapped.

Question 32

Explain the role of seismic surveys in onshore petroleum and gas exploration programs.

Answer 32

Seismic surveys provide information that can be used to create structural models of the rock formations below the ground. Seismic surveying measures the ability of different types of rock to reflect or refract waves of energy generated using explosives or vibrations. Geological settings amenable to seismic surveys include areas where the subsurface comprises layers with different thicknesses and consistencies. When exploring for hydrocarbons, faulting and folding can create structural traps for which seismic surveys can produce useful data. Geological models created using seismic survey data can be two- or three-dimensional.

Question 33

Which drilling technique is most commonly used for onshore oil and gas operations in Canada?

Answer 33

Rotary drilling is the most widely used drilling technique in Canada today. In rotary drilling, a pipe with a drill bit at the end rotates so that the bit cuts through the rock. The rotation can be driven by a rotating table on the floor of a rig, but top-drive rigs, which have a motor at the top of the drill pipe, are becoming more common.

Question 34

Describe the type of rigs that are used for drilling operations in deep water.

Answer 34

Offshore drilling rigs require a platform for support. Depending on the water’s depth, there could be hundreds or thousands of metres of water between the sea floor and the platform. In shallow water, a drilling platform may rest directly on the sea floor. In deeper water, however, this becomes impractical, so floating platforms are used. Semi-submersible rigs can be raised and lowered by simply flooding part of the structure with water.

Question 35

What is surface casing, and what purpose does it serve in oil wells?

Answer 35

Surface casing is pipe (usually steel) that is inserted into the upper part of an open hole (40–400m depth) to prevent geological formations from collapsing. This casing also directs the flow of drilling mud and other fluids that emanate from the geological formations. Surface casing also prevents contamination of groundwater by drilling fluids.

Question 36

How do drillers prevent formation fluids (from the reservoir) from flowing into the well during drilling operations?

Answer 36

To prevent the flow of fluids from the geological formations (being drilled) into the wellbore, drillers adjust the density of the drilling mud by adding a heavy mineral such as barium sulphate. It is important, however, to keep the density of the mud low enough that it does not penetrate the geological formations being drilled, because this may damage the reservoir.

Question 37

Why is natural gas more easily extracted from wells than is petroleum?

Answer 37

Because it is a gas, natural gas moves through pores and cracks in the rocks more easily than does liquid oil. Also, natural gas does not stick to mineral grains.

Question 38

Describe the process of natural gas transportation from remote oil fields around the world to major industrial centres.

Answer 38

Transporting natural gas involves liquifying it (LNG) so that it may be transported by ship. The gas is cooled to temperatures below −162 °C, at which point it becomes a liquid, occupying only 1/1600 of its gaseous volume. Once it is delivered to the consumer, it is warmed, returning it to the gaseous state.

Question 39

Name the four countries that have the largest natural gas reserves and the four countries that are the largest natural gas producers.

Answer 39

The four countries with the largest natural gas reserves are Russia, Iran, Qatar, and Saudi Arabia. As of 2013, the four leading producers of natural gas are the USA, Russia, Qatar, and Iran.

Question 40

Describe the range of sectors in which natural gas is used in Canada.

Answer 40

In Canada, natural gas is used as a heat source in residential and commercial appliances that include high-efficiency furnaces, water heaters, clothes dryers, stoves, fireplaces, barbecues, heat pumps, etc. Natural gas is also used for generating electricity.
In a number of commercial settings, natural gas is a source of up to forty-five per cent of the energy used. Industries that rely on gas include cement, steel, and fertilizer manufacturing, and the processing of forestry products. Natural gas is also an important raw material in the petrochemical industry and in the extraction of bitumen from oil sands.

Question 41

Why is natural gas more environmentally friendly than other fossil fuels?

Answer 41

Compared to other fossil fuels, natural gas burns relatively cleanly. Because it contains carbon and a high proportion of hydrogen, the only by-products of its combustion are water vapour and carbon dioxide. Its contribution to greenhouse gas output is comparatively less than that of other fossil fuels. It should be noted, however, that the drilling of wells to extract natural gas and the construction of pipeline facilities can cause significant environmental interference.

Question 42

What are the characteristics of heavy oil and bitumen?

Answer 42

Heavy oil and bitumen
A. are dark in colour;
B. are extremely viscous. They will not flow under natural conditions, so they respond poorly to primary and secondary recovery techniques;
C. have a high sulphur content (three to six per cent) and a high nickel and vanadium content (500 ppm); and
D. are rich in asphaltines.

Question 43

List the five countries or regions in which large deposits of tar sands are found.

Answer 43

Large deposits of tar sands are found in Canada, Venezuela, the USA, Russia, and the Middle East.

Question 44

Describe three processes by which bitumen can form from petroleum.

Answer 44

Bitumen (also known as heavy oils and oil sands) can be found alone or together with liquid petroleum. There are three theories about bitumen formation. It is believed that some bitumens are produced when liquid petroleum is oxidized. This oxidation results in the loss of lighter and more volatile fractions, leaving behind heavier organic molecules that form bitumen.
Bitumen may also form from liquid petroleum through thermal maturation, whereby liquid petroleum is heated and lighter components are driven off as volatiles. A third possible mode of formation is biodegradation through which bacterial decomposition eliminates the lighter hydrocarbon fractions, leaving behind the heavier bitumens.

Question 45

What is synthetic crude oil, and how is it produced?

Answer 45

Bitumen’s low hydrogen-to-carbon ratio is different from that of conventional crude oil. Consequently, to make it valuable for refining, some of the carbon must be removed or hydrogen must be added. Since these enriching processes are artificial, the resulting crude oil is called synthetic.

Question 46

What is the ultimate potential for bitumen reserves in the Alberta oil sands? How long would these reserves supply Canada’s needs?

Answer 46

According to a 1998 report by the Alberta Energy and Utilities Board, the ultimate potential for bitumen reserves in the Alberta oil sands is 273 billion cubic metres or 1.655 trillion barrels (Athabasca—213 billion m3; Cold Lake—32 billion m3; Peace River—25 billion m3). The latest (2006) estimates, however, place the reserves between 1.7 and 2.5 trillion barrels.

Question 47

How were the sands that host bitumen initially deposited? What is the theory on how they became saturated with bitumen?

Answer 47

About 100 million years ago, streams flowing from the newly emerging Rockies to the west and from the Precambrian Shield to the east deposited the sand between a series of northeast/southwest trending ridges in what is now Alberta and Saskatchewan. As yet, there is no definitive agreement on how the oil saturated the sand. One theory suggests that the bitumen was never exposed to the high temperatures and pressure that produce normal crude oil, and that it came into contact with fresh water (likely groundwater) which removed the more soluble light hydrocarbons and provided oxygen. This oxygen allowed bacteria to attack the hydrocarbons and reduce its light fractions even more. The resulting bitumen would have been extremely viscous, prohibiting its further migration to the surface and causing it to adhere to the sand grains.

Question 48

How do the characteristics of heavy oil and bitumen differ? How do the locations of their Alberta deposits differ?

Answer 48

Heavy oils have the same general chemical composition as bitumen, but differ in viscosity: heavy oils are less viscous than bitumen. Heavy oil deposits are located in central Alberta, southern Alberta, and Saskatchewan. The farther south the deposit, the more fluid the heavy oil.

Question 49

In which situations is surface mining used for the recovery of oil sands? What techniques are used when surface mining is impossible?

Answer 49

Surface mining can be used to recover oil sands that lie close to the Earth’s surface and in areas where there is little overburden. When deposits are buried too deep for economical surface recovery, in-situ methods are used. In these methods, steam or a solvent is injected into the deposit, or a fire is ignited to generate heat that mobilizes the bitumens.

Question 50

Describe the general process involved in recovering bitumen from surface-mined oil sands.

Answer 50

After recovery, surface-mined oil sand is rotated in large drums with hot water, steam, and a caustic solution. At a temperature of 80 °C, the bitumen separates into small globules in the mixture. Rocks, clay, and lumps of tar are screened out, and the mixture goes into a separation tank where most of the bitumen rises to the surface as a froth. The rest of the bitumen, suspended in the solution, goes through a second froth flotation, and then both batches of froth, (which contain virtually all of the bitumen) are heated and diluted with naphtha to make the bitumen more fluid. The solution then goes through two centrifuges to render only bitumen and naphtha, the latter of which is then removed, resulting in pure bitumen.
New extraction techniques are being developed such as the multi-stage counter current decantation process, which yields partially upgraded bitumen in the field. In this method, after the bitumen is extracted, it is mixed with a paraffin-based solvent which eliminates asphaletenes by precipitation. The resulting product will not require coking at the refineries.

Question 51

Describe the process by which bitumen is upgraded to synthetic crude oil.

Answer 51

To upgrade bitumen into synthetic crude oil, the big molecules in the bitumen are cracked to smaller fractions using coking and/or hydrocracking. In coking, the carbon is removed, whereas in hydrocracking, hydrogen is added. After cracking, the bitumen is passed through a hydrotreatment process to stabilize the cracking products and to eliminate impurities such as sulphur. Both hydrocracking and hydrotreating use hydrogen produced from steam and natural gas. The liquid products are recombined to form synthetic crude oil, which can be piped to markets.

Question 52

Describe the two in-situ recovery methods that use steam, and list their advantages disadvantages.

Answer 52

The two in-situ recovery methods using steam are known as cyclic steam stimulation and steam-assisted gravity drainage (SAGD). The former, also known as the “huff and puff” method, uses only one well for both stimulation and recovery. High pressured steam is pumped down the well for up to several weeks. After turning off the steam, the reservoir is allowed to settle. Generally, the injection of steam reduces the viscosity of the bitumen. The resulting fluid oil and water are pumped out. When the volume of bitumen in the recovered mixture drops below a certain level, steam is reintroduced and the cycle repeated until it becomes profitable. The advantage of this method is that it takes only a short period of time to reach commercial production; the disadvantage is that only five to ten per cent of the bitumen can be recovered.
The SAGD technique uses two types of wells for recovery: steam injection wells and recovery wells. The process is similar to cyclic steam simulation, but there is no need to stop and start recovery. The main advantage of SAGD is that the total recovery rates are much higher than in the cyclic steam circulation method. The disadvantage is that, to reach the recovery well, the heated, less viscous oil must pass through an unheated portion of the formation.

Vapour extraction (VAPEX) is a variation of the SAGD procedure whereby natural gas liquids (e.g., propane and butane) replace steam to free bitumen.

Question 53

Explain how fire can be used as an in-situ recovery method, and list the advantages and disadvantages.

Answer 53

The forward combustion technique is one variation of the techniques that use fire to free the bitumen from the sands. In this method, air is forced down the injection well and ignited. The heat cracks the bitumen, reducing some of it to coke, which then acts as a fuel source itself. As the fire moves through the formation, it drives the lighter fractions towards the recovery well. An advantage of forward combustion is that the bitumen need not be as mobile as with steam drive, because the combustion gases heat the oil ahead of the fire. The main disadvantage is the same as with steam drive: the area through which the oil has to flow is cold.

Question 54

What environmental problems can arise from in-situ bitumen extraction methods?

Answer 54

While the extraction of bitumen by in-situ methods does not require surface clearance of large areas nor the excavation of surface materials, establishing the necessary infrastructure can significantly disrupt the environment. Setting up seismic survey networks during the exploration phase, and constructing roads, power lines, and pipelines can interfere with wildlife, vegetation, and wetland ecosystems. Such “linear disturbances” can fragment natural ecosystems by affecting sensitive species and increasing human traffic into previously inaccessible areas.

Question 55

Describe the characteristics of kerogen, the organic component of oil shale.

Answer 55

Kerogen is a waxy, insoluble mixture of hydrocarbons composed of complex molecules with high molecular weights. They can be converted to oil at temperatures of 500 °C or more.

Question 56

How did oil shales form?

Answer 56

Oil shales formed in quiet bodies of water that were rich in organic matter. Although many types of organic debris contributed to kerogen formation, lipids from blue-green algae seem to have been the most important. Fairly high rates of accumulation of clays and organic debris occurred under stagnant conditions, which limited decomposition by oxygen and bacteria and prevented organic destruction. Continued burial increased depth below the surface and provided the pressure and heat to form shale. The heat, however, was only 100–150 °C, so conversion to crude oil could not take place.

Question 57

Describe the two proposed methods of recovering hydrocarbons from oil shale.

Answer 57

Surface mining of hydrocarbons from oil shale involves mining the shale, grinding it into fine particles, and heating it to about 500 °C in large retorts. The resulting hydrocarbon vapours are cooled and separated as in conventional refining operations. The in-situ process begins by constructing of underground tunnels to break up the shale. The fractured rock is then ignited and kept burning with a flow of air, diesel fuel, and steam. The rock ahead of the combustion zone is heated to about 500 °C; this heat vaporizes the kerogen, which is driven toward the recovery well.