To have the concept about in which environment oil and gas can be formed.....

1. PETROLEUM FORMATION AND PETROLEUM
FORMING ENVIRONMENT
SUBHASIS PAL
ADMISSION NO- 17MC000387
5th SEMESTER
M.Sc.TECH APPLIED GEOLOGY

2. What is hydrocarbon?
Hydrocarbon is the compound that is mainly made up of hydrogen and carbon
atoms or other elements like N, O, S etc. Hydrocarbon can occur in different
states in nature.
What is crude oil?
Crude oil is defined as “a mixture of hydrocarbons” that existed in the liquid to
semi-liquid phase in natural underground reservoirs.
What is petroleum?
Petroleum is also mixture of hydrocarbons (liquid state) or a fossil fuel. The
name petroleum covers both naturally occurring unprocessed crude
oil and petroleum products that are made up of refined crude oil.

3. Generation of oil and gas(hydrocarbon)
DIAGENESIS
• Formation of kerogen and biogenic
gas from organic matter.
CATAGENESIS • Formation of oil and wet gas from
kerogen
METAGENESIS
• Formation
of dry gas

5. Type I: A rare type of high-grade, algal sediment, commonly
lacustrine, containing sapropelic OM. It includes oil shales
Type-II:Type of intermediate derivation, commonly marginal
marine, with admixture of continental and aquatic (especially
planktonic) OM. Algal tissue , pollen, and spores are important
contributors. This type includes the principal source sediments
for oil , and some ancient oil shales of marine origin. H:C ratio
about 1.4.
Type III Sediment containing primarily humic OM, of terrestrial,
woody origin. The material was deposited at the oxic
sediment/water interface; it is gas prone. H:C ratio 1.0 or less
(that is, there are more carbon atoms than hydrogen atoms).
Type IV OM may have come from any source, but it has been
oxidized, recycled, or altered during some earlier thermal event.
The inert carbonaceous material is now deficient in hydrogen
(H:C ratio about 0.4 or less), has no evolutionary path left for it,
and yields negligible or no hydrocarbons.

6. PETROLEUM FORMING ENVIRONMENTS AND
CONDITIONS
SUITABLE ENVIRONMENTS AND
CONDITION OF THE DIAGENESIS
SIUTABLE ENVIRONMENT AND
CONDITION FOR THE CATAGENESIS

7. SUITABLE ENVIRONMENTS AND
CONDITION OF THE DIAGENESIS
Selective organic matter accumulation
Productivity of organic matter
Rate of sedimentation
Preservation of organic matter in anoxic condition

8. Fig. Main groups of microfossils in the
marine environment. (After Moore,
1969)
Main groups of microfossils
in the non marine environment.
(After Moore, 1969)
Organic productivity in time

10. Primary biological productivity (org. carbon m-2 yr- I) in
the world oceans. Productivity is relatively high in
coastal areas, upwelling along the west coast of the
American and African continents. (Adapted from
Debyser and Deroo,
1969)
Organic productivity in space
The biological productivity in the marine
environment is mainly controlled by light,
temperature, and mineral nutrients, such as
phosphate and nitrate.

11. • A fundamental difference exists between the chemical composition of marine planktonic
algae and terrestrial higher plants. The organic matter of marine plankton is mainly
composed of proteins (up to 50% and more), a variable amount of lipids (5 to 25%), and
generally not more than 40% carbohydrates. Higher terrestrial plants are largely
composed of cellulose (30 to 50%) and lignin (15 to 25%). Both constituents fulfil mainly
supporting functions, and are not needed in aquatic, planktonic organism.
• Predominantly land-derived organic matter with high contents of lignin and
carbohydrates.
• All organisms are basically composed of the same chemical constituents: lipids, proteins,
carbohydrates and lignins in higher plants. However, there are very characteristic
differences with respect to relative abundance of compound and detailed chemical
structure. With respect to the formation of petroleum, the lipids are most important. Lipids
encompass fat substances.
Selective organic matter accumulation

12. Sedimentation rate

13. Oxidizing/Aerobic/open sea environment
Reducing/ Anaerobic/Restricted water environment
(Role of microbiota)
(Role of microbiota)
(Role of sediments)
(Role of sediments)
Organic matter : Microbiota converts to CO2+H2O
Organic matter : Microbiota converts to CO2+CH4 (Marsh Gas/Biogenic gas)
Preservation of organic matter in anoxic
condition

14. Different anoxic conditions of modern and ancient
environment

15. Oxygen minimize zone in modern ocean

16. Modern oceanic condition

17. Deltaic- lacustrine environment

19. The origin of the organic matter is frequently marine or freshwater algae, but other
planktonic organisms and also bacterial biomass may contribute significantly. When
compared with the classification established for petroleum source rocks, kerogen of the
oil shales belongs to type I or 11.
Oil shales have been deposited in lake basins, shallow seas, bogs and lagoons from late
Precambrian to Tertiary. Shale oil contains a significant proportion of unsaturated olefins
which are absent in natural crude oils. Sulfur and nitrogen are also abundant in shale oil.
Petroleum formation in marsh, swamp and
estuary?
What’s about fluvial floodplain Or fluvial?,
Aeolian? and oil in mountain?.

20. There is thus a range of temperatures through which the generation of
oil can take place if the source sediments are suitable (Fig ).
At temperatures below the critical jump temperature of about 60oC ,
the sediments are immature; at temperatures beyond some higher
critical temperature (typically about 120oC) they are post-mature
Environment for catagenesis

21. TTI as catagenesis parameter

22. THANK YOU

23. Main natural associations of organic matter
in aquatic sediment during geological
history. Cambrian through Silurian
sedimentary rocks mainly contain remnants
of bacteria, algae and zooplankton. Devonian
through Jurassic sedimentary rocks generally
contain remnants of algae, zooplankton and
bacteria, but in addition some higher plant
matter, especially in near-shore
environments. Cretaceous to Recent
sedimentary rocks gene rally contain
relatively less planktonic organisms and
bacteria and frequently a greater part of
higher plant remains.

24. What are Phytoplankton?
Derived from the Greek words phyto (plant) and plankton (made to wander or drift),
phytoplankton are microscopic organisms that live in watery environments, both salty and
fresh.
Some phytoplankton are bacteria, some are protists, and most are single-celled plants.
Among the common kinds are cyanobacteria, silica-
encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores.
Phytoplankton are extremely diverse, varying from photosynthesizing bacteria (cyanobacteria), to
plant-like diatoms, to armor-plated coccolithophores (drawings not to scale). (Collage adapted
from drawings and micrographs by Sally Bensusen, NASA EOS Project Science Office.)
Like land plants, phytoplankton have chlorophyll to capture sunlight, and they use
photosynthesis to turn it into chemical energy. They consume carbon dioxide, and release
oxygen. All phytoplankton photosynthesize, but some get additional energy by consuming
other organisms.
Phytoplankton growth depends on the availability of carbon dioxide, sunlight, and
nutrients. Phytoplankton, like land plants, require nutrients such as nitrate, phosphate,
silicate, and calcium at various levels depending on the species. Some phytoplankton
can fix nitrogen and can grow in areas where nitrate concentrations are low. They also
require trace amounts of iron which limits phytoplankton growth in large areas of the
ocean because iron concentrations are very low. Other factors influence phytoplankton
growth rates, including water temperature and salinity, water depth, wind, and what kinds
of predators are grazing on them.

25. Main natural associations of organic matter in aquatic sediment during geological history.
Cambrian through Silurian sedimentary rocks mainly contain remnants of bacteria, algae
and zooplankton. Devonian through Jurassic sedimentary rocks generally contain remnants
of algae, zooplankton(heterotrophic) and bacteria, but in addition some higher plant matter,
especially in near-shore environments. Cretaceous to Recent sedimentary rocks gene rally
contain relatively less planktonic organisms and bacteria and frequently a greater part of
higher plant remains.(FIRST LAND PLANT AROUN 470MY AGO) and first fungi in
Cambrian.
the main producers of organic matter in the marine environment are the various
groups of unicellular, microscopic phytoplanktonic organisms. The main groups
are diatoms, dinoflagellates, Cyanophyceae (bluegreen algae) and very tiny, naked
phytoflagellates or nonmotile cells, the
nannoplankton.
Phytoplankton.(microscopic marine algae, autotrophic), , the primary producer of
organic matter, forms the basic member of the food chain and hence of the
pyramid of life. Diatoms, dinoflagellates, and coccolithophores are the main
producers in this sequence.
The main groups are diatoms, dinoflagellates, Cyanophyceae (bluegreen algae)
and very tiny, naked phytoflagellates or nonmotile cells, the nannoplankton.
Quantitatively, the four most important contributors to organic matter in
sediments are phytoplankton, zooplankton, higher plants and bacteria. Higher
organized animals, such as fishes, contribute on the average so little to organic
matter in sediments that they can practically be neglected. Heterotrophic bacteria
are abundant where organic matter is available as a source of food.

26. The biological productivity in the marine environment is mainly controlled by light,
temperature, and mineral nutrients, such as phosphate and nitrate. The larger part
of
biological production is concentrated in the upper 60 to 80 m of the water column.
Many researchers have observed a so-called landmass or island effect, where,
as a broad generalization, primary productivity is greater ne ar the coast of
continents and islands
The two most important extremes, barren oceans and zones of upwelling,
Barren oceans: Most of the tropical oceans between latitudes 10° and 40°, and
stagnant tropical gyres like the Sargasso Sea, are very unproductive
Continental shelf upwelling: The effect of prevailing winds and of the Coriolis
force on ocean currents off the west coast of continents may cause upwelling, and
therefore great fertility (2 g Cm -20 day-I and more).
This relationship has existed since the emergeney of
zooplanktonie organisms in the Precambrian, such as unieellular foraminifera and
radiolarii. It also applies to other organisms of the animal kingdom, like worms,
mollusks, and arthropods. There are a few landmarks with respect to the
oeeurrenee of zooplankton.
An oceasionally massive oceurrenee of trilobites during the Cambrian, Ordovieian
and Silurian, as weIl as the explosive emergence of foraminifers during the Late
Jurassic. Planktonic foraminifera must be considered as major contributors of
organic matter to certain marine sediments.

28. Sulfate-reducing bacteria (Desulfovibrio) utilize oxygen from SO~- and reduce the sulfur to S2- under anaerobic conditions. This normally happens below the water-sediment
interface where interstitial water is separated from the overlying free water: bacteria extract the limited amount of sulfate initially present in interstitial water or
provided by the slow process of diffusion. The zone of sulfate reduction is normally confined within the upper level of sediment, and the
water
column above the sediment does not contain hydrogen sulfide . Sea or lake water
usually contains dissolved oxygen, and hydrogen sulfide emanating from the
sediment interface is oxidized again into sulfate, under aerobic conditions, by
other types of bacteria (Thiobacillus). Thus, an equilibrium is established
between supply and destruction of H2S:Thus, an equilibrium is established
between supply and destruction of H2S: Orr (1974) (Fig. 11.2.2). In some cases,
however, the bottom water layer of the sea or lake becomes devoid of oxygen,
and sulfur-oxidizing bacteria cannot work in such anaerobic conditions - except
photosynthetic colored bacteria in shallow waters. Furthermore the free water
becomes subject to sulfate reduction; large quantities of H2S and free sulfur may
be produced from seawater; and the benthic life disappears, except anaerobic
microbes, partly due to lack of oxygen, and partly due to toxicity of H2S (Fig).
The phenomenon may occur for various reasons, but it is due mainly to restrictions in water circulation and
to eutrophic conditions. Restrictions in water circulation may prevent oxygen supply of water layers. For
example the Black Sea, nearly separated from the Mediterranean Sea, receives more freshwater from rains
and rivers than is lost by evaporation. This results in a low salinity and a low density of surface waters, thus
preventing convection. Therefore the water column is stratified and bottom waters remain deprived of
oxygen. Anaerobic bacteria generate abundant H2S, but it is not destroyed by aerobic sulfuroxidizing
baeteria. Eutrophie conditions result from superabundant supplies oforganic matter or nutrients
(phosphate, nitrate) to lake or seawaters, as ispresently happening in Lake Erie due to human pollution.
Populations of bacteria and other organisms that live at the expense of the organic matter and use
dissolved oxygen grow considerably. They subsequently eliminate oxygen from the bottom waters. The

29. Sulfur is not incorporated in the bacterial cell. In clay muds, where iron is
usually abundant, it is likely that sulfur readily recombines with iron to
form
hydrotroilite and troilite, which are slowly converted to pyrite. In
carbonate
muds, however, where iron is much less abundant, sulfur may recombine
mainly
with residual organic matter. Massive incorporation of sulfur into
sediments in
certain confined environments with H2S-saturated bottom water may
lead to a
subsequent recombination with organic matter during late diagenesis
and finally
explain the origin of a sulfur-rich petroleum formed during catagenesis.
Fermentation is an anaerobic process by which bacteria, instead of using
molecular oxygen (respiration), use oxidized forms of organic matter,
particularly
carbohydrates. Cellulose is degraded enzymatically by bacteria, such as
Clostridia (Doose, 1980), producing the low molecular weight precursors
for
methane formation (acetate, bicarbonate) and the final stage is a
reduction of
carbon dioxide or acetate by methane-generating bacteria, such as

30. The fourth setting for the deposition of organic sediment is in an anoxic ocean basin. There
is no known Recent instance of this situation. Most modern ocean floors are reasonably well
oxygenated. Deep oceanic circulation is caused by density currents, where cold polar waters
flow beneath warmer low-latitude waters. It has been argued, however, that deep oceanic
circulation may not have existed in past periods when the earth had a uniform, equable
climate without the polar ice caps of today; this seems to have been particularly true of the late
Mesozoic Era (Allen et al., 1994). At such times, global “anoxic” events may have
been responsible for the worldwide deposition of organic-rich sediment (Fig. 5.8(D)). This
mechanism has been proposed to explain the extensive Upper JurassiceLower Cretaceous
black shales that occur in so many parts of the world, notably in the Atlantic Ocean
and its environs.

32. Petroleum formation in marsh and swamp environment?
Petroleum formation in modern environmrnt?
Mainly delta, continental shelf and lacustrine, in modern days marine
anoxic condition is less likely to achieve.
Whats about fluvial, Aeolian(example Rotligend sandstone of
Permian age in southern North Sea and flood plain and oil in
mountain( Zagros region is an important area for oil production. Salt
domes and salt glaciers are a common feature of the Zagros,
Appalachian Basin The success of the Drake well quickly led to oil drilling in other locations in the western Appalachian mountains, where oil was seeping to the surface