Illinois Petroleum

Salem Oil Field—1943, Marion County, Illinois.

Illinois Oil Production

• Illinois has about 650 oil fields, primarily in the southern half of the state.

• Until about 1970, Illinois was among the top oil-producing States, but today petroleum production is minor.

• Estimate 89 million barrels in petroleum reserves

The First Well

• In the early 1860s, several holes drilled in Clark County produced enough oil for the name "Oilfield" to be given to a small town there, even though commercial-scale production in the area did not begin until 40 years later.

• Natural gas seeps near Oilfield led the company's owners to believe that commercial quantities of oil and gas were there.

The First Well

Early Illinois Oil Production

Early Illinois Oil Production• From 1904 to 1910, numerous shallow oil and

gas reservoirs were discovered beneath eastern Illinois.

• With these discoveries, Illinois leaped to third among states as its annual petroleum production rose from 181,000 barrels in 1905 to 33 million barrels by 1910.

• By 1913, all the easily discovered were drilled and the heyday of the oil fields in eastern Illinois was over.

• By 1936, with few new discoveries to replace fields already pumped dry, the state's total oil production had dropped to less than 4.5 million barrels.

Illinois Sedimentary Basin

During most of Paleozoic time (from 600 – 250 million years ago), sediments and organic material accumulated in the slowly subsiding Illinois Sedimentary Basin.

Illinois Sedimentary Basin

• A sedimentary basin is a geographical feature exhibiting subsidence (sinking) and consequent infilling by mud, sand and other types of sediment.

• As the sediments are buried, they are subjected to increasing temperature and pressure.– Over time, the sediment is lithified into sedimentary

rock.• Organic material deposited in the basin is also

subjected to increasing temperature and pressure.– Over time, the organic material may be altered to

hydrocarbons

Source of Petroleum• When marine

phytoplankton die, their remains settle to the bottom of the ocean and collect in mud.

• As the organisms begin to decay the small amount of oxygen present is used up, the remaining organic matter is preserved and covered with more mud.

Anoxic Events• Increase in greenhouse gasses (usually CO2 from

volcanic eruptions) leads to an increase in global temperature.

• Warmer temperatures result in more rain which leads to an increase nutrients washed into the oceans via rivers.

• Phytoplankton bloom in the nutrient rich water and consume the oxygen dissolved in the water. “Dead Zones” form.

Anoxic Events

• Warmer temperatures also lead to complete or at least large scale stoppage of deep water circulation between the poles and equator.

• Large amounts of organic matter (mainly dead phytoplankton) can sink and accumulate on the anoxic ocean floor due to the stagnant oceans.

• Black, organic-rich muds form on the ocean floor which will later form shale source rocks.

• Over 70% of petroleum deposits were formed in the Mesozoic Era when warm temperatures resulted in a global anoxic ocean environment

Maturation

• Over time and continued burial, the organic material in the source rock is subject to heat and pressure.

• This initiates a series of physical and chemical processes take place that break down the organic material into simpler and gaseous hydrocarbon compounds.

• This processes is called maturation.

Hydrocarbon Kitchen

• Oil in the Illinois Basin is produced from a temperature-pressure zone called the “hydrocarbon kitchen.”

• Here the most important organic-rich, oil-generating black shale (Source Rock) in Illinois, called the New Albany Shale, was “cooked” enough to convert organic matter into petroleum.

Illinois Source RockNew Albany Shale

• The New Albany Shale was deposited under anoxic marine conditions in the Illinois basin during the Devonian Period

Hydrocarbon KitchenThe hydrocarbon kitchen requires the following

conditions:• High pressure from overlying rock layers• Temperatures between 80-145°C

– Less than 80°C: no hydrocarbons will form– Greater than 145°C: hydrocarbons will become all

carbon and not be useful

• At least 2 million years from organic material to mature to petroleum– No rock layers containing petroleum are younger than

2 million years

Hydrocarbon Kitchen

• Because temperature increase with depth, he rule of thumb says that temperatures 7,500 feet down are hot enough to "crack" organic-rich sediments into oil molecules.

• However, beyond 15,000 feet the rocks are so hot that the oil molecules are further cracked into natural gas.

• The range from 7,000 to 15,000 feet is called the "oil window." If you drill deeper than 15,000 feet, you can find natural gas but little oil.

Hydrocarbon Kitchen

Organic Rich Shale(Source Rock)

Tar

Oil

Natural Gas

Rock

80°C (7,500ft)

145°C (15,000 ft)

“Petroleum Window”

Need to cook for millions of years!!

No Petroleum

No Petroleum

Petroleum Migration• Although shale is the source rock, petroleum is

found in rocks such as sandstones and limestones.

• Geologists realized that petroleum must form in one kind of material and then migrate to another at some later time

• Over time, small droplets of oil and gas in the source rock begin to coalesce and are eventually squeezed out by the weight of the overlying rocks.

• For migration to occur the petroleum must encounter a reservoir rock in which it can easily travel through to the surface.

Reservoir Rock

• Here we see what a reservoir rock would look like through a magnifying lens.

• The yellow objects represent sand grains that are packed together.

• Notice, however, the purple areas between the sand grains.

• These areas (also known as "pore spaces") are where the oil fits into the rock.

Reservoir Rock - Sandstone• The most common

reservoir rocks in Illinois are sandstone and limestone

• Reservoir sandstone has individual sand grains that are slightly cemented together.

• These sand grains were originally deposited in river channels and deltas or as sandbars and beaches in the Illinois Basin.

Grains of coarse sand from an oil reservoir, magnified

50 times by a scanning electron microscope. The

oil-water fluid filled the spaces between the grains.

Reservoir Rock - Limestone

• Limestone reservoir rock may consist of sand-sized or larger fragments of corals, sponges, snails, clams, and other marine animals.

• Many ancient limestone reef deposits in Illinois contain oil.

Cap Rock• What prevents petroleum

from leaking out of the reservoir rock onto the earth’s surface?

• A rock with low porosity such as shale gets in the way. Such a rock is called a cap rock.

• Because there is no space between clay particles in shale, oil will not move through this rock - instead, it will be blocked

Migration in The Illinois Basin

• Notice that oil is also found in reservoirs many tens of miles outside the kitchen.

• The oil reached these reservoirs through porous layers that acted like slightly inclined pipes that transported the oil far from the kitchen.

• Geologists say that the oil “migrated laterally” to these reservoirs. The oil fields in western Illinois are good examples of fields that required lateral migration.

Petroleum Trap

A combination of source rock (contributing the organic material), a reservoir rock (allowing for migration of petroleum) and a cap rock (to stop migration) is called a Petroleum Trap.

Anticline Trap

• One the most common traps is the anticline trap.

• The rock layer are arched up and the petroleum accumulates at the top of the arch in the reservoir rock.

Anticline Trap

• Inside the reservoir rock, the oil, water and natural gas will separated due to density differences.

• Natural gas will at the top followed by oil, and then water.

Natural Gas

• Natural gas is a combustible mixture of hydrocarbon gases (mainly methane with lower amounts of butane, propane and ethane) formed at the upper end of the Hydrocarbon window.

• Most of the Illinois reservoir rocks have a small fraction of natural gas near the tops of anticlines structures.

• Most of the natural gas consumed in the Illinois is produced in the Gulf of Mexico and transported by pipelines.

Seismic Exploration • This technique uses sensitive microphones

called "geophones" to record sound waves from ground-level dynamite blasts as they "echo" off the tops of the successive rock layers below.

• The echo data are then used to form a picture of the rock layers below.

Anticlines on a Seismic Profile

Seismic Exploration in Illinois

• Seismic exploration allows geologists to find hidden anticlines—structures too deeply buried or too subtle to be found otherwise.

• Seismic exploration in the 1930s discovered many anticline traps in Illinois.

• The largest trap is the LaSalle Anticline.

LaSalleAnticline

Seismic Exploration in Illinois• Illinois Oil Production rose to its highest level

after seismic exploration techniques were first introduced in the early 1930’s.

Oil Recovery

• Once a potential petroleum trap is discovered, a well is drilled to extract (“produce”) the oil.

• The well bore is created by drilling a hole 13–76 cm wide with an oil rig turning a drill bit.

Oil Recovery • After the hole is drilled, a metal pipe slightly smaller than the hole size (called a ‘well casing') is run into the hole.

• The casing is perforated in the reservoir rock to allow the oil –water mixture to flow into the well bore.

• The oil-water mixture is pumped to the surface through a production pipe located inside the well casing pipe.

A Typical Oil Well in Illinois

At the well head is the rocking pump jack (at the left). A water oil mixture is recovered from the reservoir rock The mixture is pumped to the separator tank (center), and the oil then flows by gravity to one of the two storage tanks (right). The water flows to the other storage tank where it is collected and may be pumped back underground through an injection or disposal well.

Primary Oil Recovery

• A familiar oil-well image is an uncontrolled "gusher" spewing oil high into the sky to rain down on the joyous drillers. Oil gushes because it is under pressure in the ground.

• Oil produced under this natural driving pressure is the "primary recovery" or "primary production" of a field.

Primary Recovery

• Once the natural pressure is reduced, a well pump jack is installed at the surface to pump out the oil from the reservoir rock.

• The pump jack at the surface rocks up and down, opening and closing values in the well.

• Each stroke brings a cup or two of fluid up to the surface.

• This primary recover technique pumps out only 15% of the oil in the reservoir rock

Secondary Oil Recovery• Water is injected into the reservoir rocks to maintain

reservoir pressure as the oil is withdrawn, and to sweep the oil out of the reservoir rocks and toward the well.

• In the most commonly used technique, the five-spot pattern, water is pumped into the reservoir rocks at four wells arrayed around a central producing well.

• This water flooding technique can yield another 20% of the available oil in the reservoir rock

Secondary Oil Recovery• Using secondary recovery techniques, Illinois'

total oil production rose to about 82.3 million barrels in 1956, a peak from which it has been declining almost continuously ever since.

Enhanced (Tertiary) Oil Recovery

• Steam or CO2 gas is injected into the reservoir rock to force from the reservoir rock to the surface.

• Very Expensive and not cost effective in Illinois with the price of oil.

• Additional 10% recovery

• Still almost 55% of oil in reservoir rock remain in the ground!

Enhanced (Tertiary) Oil Recovery• Some enhanced recovery techniques were used

in Illinois in the 1980s, but price of oil makes this method cost prohibitive at the moment.

The Future of Illinois Oil Production

• There is still an abundance of possible oil and natural gas reserves available in the Illinois Basin.

• For the Illinois Basin, the USGS estimated the quantities of undiscovered, technically recoverable oil and gas resources as follows– a mean of 214 million barrels of oil,– a mean of 4.65 trillion cubic feet of natural gas

• Because it is centrally located within the US borders, transportation costs are extremely low, providing for more profit margins.

Unconventional Petroleum

• Unconventional petroleum produced or extracted using techniques other than the traditional oil well method.

• Unconventional oil production is less efficient and has more environmental impacts than conventional oil production.

• There are three main unconventional petroleum sources: oil shale, tar sands, and shale gas

Oil Shale• Oil Shale is a source rock that was not cooked

enough in the hydrocarbon kitchen.• The petroleum in oil shale are solid and cannot

be pumped directly out of the ground. • Oil shale deposits in the western U.S. are

estimated to contain over 2 trillion barrels of oil: equivalent to 1 to 2 times total world oil reserves.

• The oil shale has to be removed from the ground and cooked at high temperatures to be converted in to liquid oil. This is expensive and requires a significant energy input.

Oil Shale• An in situ conversion process (ICP)

involves heating underground oil shale, using electric heaters placed in deep vertical holes drilled through a section of oil shale.

• The volume of oil shale is heated over a period of two to three years, until it reaches 650–700 °F, at which point oil is released from the shale.

• The released product is gathered in collection wells positioned within the heated zone.

Tar Sands• Tar sands are sandstone that contain a

thick asphalt like oil called “bitumen” which cannot be recovered by conventional petroleum recovery methods.

• Because bitumen flows very slowly, if at all, the sands must be extracted by strip mining or the made to flow into wells by injecting steam, solvents, and/or hot air into the sands.

• About two tons of tar sands are required to produce one barrel of oil.

Tar Sands

Tar Sands• Much of the world's oil (more than 2 trillion

barrels) is in the form of tar sands, although it is not all recoverable.

• While tar sands are found in many places worldwide, the largest deposits in the world are found in Alberta Canada.

• Approximately 20% of U.S. crude oil come from Canada, and a substantial portion of this amount comes from tar sands.

• Most of the petroleum refined in Illinois is from the Alberta Tar Sands

Shale Gas

• Shale gas is defined as natural gas from shale formations.

• The shale acts as both the source and the reservoir for the natural gas.

• In the united States, over 600 trillion cubic feet of natural gas may be found in shale gas deposits.

• In Illinois, recoverable shale gas in the New Albany Shale has been estimated to be between 1.9 and 10.2 trillion cubic feet.

Producing Shale Gas

• A well is drilled vertically into the shale, then travels horizontally along the formation to create a larger area from which to collect the gas

• A mixture of water and additives is forced into the well at a high pressure, creating multiple fractures, freeing more gas to collect in it.