Geol 404 Final

Front 1

What is the first and most important step in petroleum resource assessment?

Back 1

To identify and interpret correctly the fundamental tectonic processes (subsidence, uplift, and deformation), thermal processes and petroleum system processes

Front 2

What is the wilson cycle?

Back 2

Continental rifting
Sea floor spreading
Ocean Closing
Arc Continent Collision
Continent Continent Collision

Front 3

Sediments are deposited with what two initial conditions? and how do they change during burial?

Back 3

Initial porosity and permeability

Due to the overburden, porosity decreases. As porosity descreases, so does permeability.
Water is squeezed out of the sediment, however if permeability is too low to allow the water to escape, the fluid adds pressure to make over pressure
Temperature changes.

Front 4

What controls fluid flow and influences thermal conductivity, subsurface temperature distribution and geothermal gradient?

Back 4

Pressure

Front 5

Temperature and Time are the two dominating factors on what?

Back 5

the maturation of organic matter

Front 6

What is the usual geothermal gradient?

Back 6

25 Centigrade per kilometer

Front 7

What are the two kinds of porosity?

Back 7

Primary (Rock characteristic)
Secondary ( due to solution, recrystallization and dolomitization, fractures and joints)

Front 8

What are porosity depth relationships used for?

Back 8

reconstructing original thickness of sediments (for backstripping) and to trace the thickness change and porosity change through time.

Front 9

What is overpressure?

Back 9

If the escape of fluids is slower than the rate of added overburden pressure in excess of hydrostatic builds, the sediment becomes over pressured.

Front 10

Where does overpressure typically develop?

Back 10

In areas where sedimentation rates are high and where there are fine-grained and/or low permeability sediments present

Front 11

What is a sedimentary basin?
How are they formed?

Back 11

A depression in the crust of the earth, caused by plate tectonic activity and subsidence, in which sediments accumulates.

They are formed by the deformation of the lithosphere ( stretching, cooling, or bending)

Front 12

How many sedimentary basins are there in the world?
What percent of that produce petroleum?

Back 12

about 600
25%

Front 13

What is basin classification based on?

Back 13

sedimentation and tectonic regimes and petroleum characteristics

Front 14

What are the different types of sedimentary basins?

Back 14

Continental rift basins (Marginal, aulacogen, intracontental)
Cratonic interiors ( sag basin)
Passive margins (Delta, miogeocline, eugeocline, abyssal pelagic fill, delta fan)
Strike Slip margins ( pull apart basin)
Subduction margins (backarc basin, forearc basin, trench fill)
C-C/A-C collision margins (foreland basin)

Front 15

What are the basin types for the largest oil fields?

Back 15

1) Collision
2) accreted
3) Rifted Margin
4) composite margin
5) convergeant margin

Front 16

What are distinguishing features of rift basins?

Back 16

underlain by continental crusts
extensive structural styles
rapid syn rift subsidence, slow post rift subsidence

Front 17

What are distinguishing features of sag basins?

Back 17

Located in continental interiors
slow subsidence rates
commonly <5km of fill
low relief surrounding areas

Front 18

What are distinguishing features of passive margins?

Back 18

rifted basement beneath thick sediment wedge
start as intracontinental rifts that continue to seafloor spreading stage

Front 19

What are distinguishing features of strike-slip fault related basins?

Back 19

very rapid subsidence
thick stratigraphic section relative to basin area
very rapid deposition
extreme facies variability
time temperature evolution may not be sufficient for source rock maturation

Front 20

What are some distinguishing features of backarc and forearc basins?

Back 20

small, deep, young
local extension and strike sip in regional compression along convergent plate margins

Front 21

What are distinguishing features of foreland basins?

Back 21

underlain by continental crust
bordered on one side by fold and trust belt
asymmetric in cross section
subsidence highly varied

Front 22

How does the depositional history change between downwarp foreland basins and craton margin foreland basins?

Back 22

in the downwarp basin there are mixed interfingering shallow marine facies.
in the craton margin there are two cycles : 1) mature platform sediments 2) orogenic elastics

Front 23

Abiogenic hydrocarbons found in igenous rocks could have originated from where?

Back 23

deep crust or the mantle

Front 24

What 3 things must be met for petroleum to be created?

Back 24

high rate of deposition of organic material
Quick perservation of material in low oxygen environment
heat and time to create petroleum

Front 25

What percent of the carbon in the carbon cycle doesn't get recycled?

Back 25

1 % dones't get recycled; gets buried instead.

Front 26

What are the major groups of organic matters?

Back 26

1) Carbohydrates (glucose, starch, cellulose)
2) lipids (fats, oils, waxes)
3) lignin (source for coal and gas)
4) proteins/'amino acids
5) nucleic acids

Front 27

What is humic organic matter?

Back 27

organic matter that is rich in ligning, cellulose and lean in lipids (most plants)

Front 28

What is sapropelic organic matter?

Back 28

organic matter that is rich in lipids (algea)

Front 29

A good source rock requires what?

Back 29

high rate of organic matter production
high preservation potential (oceans, lakes, swamps)

Front 30

What is the oxygen minimum layer in water?

Back 30

a layer of subsurface water that has lower dissolved oxygen content than the water layers either above or below (less than 0.02 % O2)
good for source rocks

Front 31

What are some characteristics of organic rich shales?

Back 31

dark brown to black in color
low porosity & permeability
1-10% total organic carbon
well laminated
gamma ray signature usually high
pyrite common in rocks

Front 32

What are some characteristics of organic lean shales?

Back 32

red-brown,tan to bluish or gray in color
low TOC
bioturbation

Front 33

What are source rock characteristics?

Back 33

fine grained clastics and carbonates
commonly 1 - 10% organic material
low matrix porosity and permeability
if brittle may be naturally fractured
coal beds

Front 34

What are the three major factors of source rock formation?

Back 34

high input and preservation of organic matter (deep water low circulating setting or shallow water stagnant setting)
low to moderate sedimentation rate ( to not dilute concentration of ogranic material)
presevation (aka anoxic conditions)

Front 35

When are good oil source rocks deposited?

Back 35

when the oceans poorly circualtes (warm global climate)
and the oceans are on a long term sea level rise

Front 36

WHat is diagenesis?

Back 36

the transformation of suitable types of organic matter to kerogen

Front 37

What is catagenesis?

Back 37

the cooking or maturation process through which kerogen yeilds oil and gas

Front 38

What is metagensis

Back 38

the stage of over cooking or transformation of kerogen to carbon.

Front 39

What are the 4 types of kerogens?

Back 39

1) algai
2) mixed marine
3) coaty (vegetation)
4) inert (fossil charcoal)

Front 40

What are the coal maceral groups and their hydrocarbon potential?

Back 40

1) exinite (rich)
2) vitrinite (hydrogen poor)
3) inertinite (inert)

Front 41

Diagenesis reacts with different organic matter. What are they going from fastest rate of decay to slowest?

Back 41

fastest: proteins
carbohydrates
lipids
slowest: lignin

Front 42

What do amino acids join together to form?

Back 42

peptides, polypetides or proteins

Front 43

How does protein form methane?

Back 43

going through acidificatin (ammino acid to acetic acid)
then bio gas formation (acetic acid to methane)

Front 44

What is the oil window (T)

Back 44

between 60 to 175 Centagrade

Front 45

What is the gas window (in terms of temperature)?

Back 45

100 to 300 centagrade

Front 46

What happens to kerogen in catagenesis?

Back 46

it changes color from light to dark
forms petroleum

Front 47

What types of organic matter are in sedimentary rocks?

Back 47

kerogen and vitrinite

Front 48

What are some ways to measure maturity?

Back 48

vitrinite reflectance (con: not in all rocks)
Pyrolysis tmax
Thermal alteration index (con: subjective method)
Conodont Alteration index (pro : plentiful in carbonate rocks where pollen and vitrinite often is absent
cons: conodonts not present in rocks younger than triassic)

Front 49

What are conodonts?

Back 49

microfossils that form a group of extinct soft bodied marine invertebrates

Front 50

What is LOM?

Back 50

level of organic metamorphism

determination of source rock matruty based on method similar to coal ranking

Front 51

What are some analytical techniques for source rock evaluation?

Back 51

column chromatography
gas chromatography
GC-MS
Leco carbon analyzer
Rock eval pyrolyzer

Front 52

What does rock eval pyrolysis show?

Back 52

three peaks
S1 = free hydrocarbons in rock
S2 = amount of hydrocarbons generated from kerogen in the rock and it a measure of reamining generative capacity
S3 = oxygen content of the kerogen

Front 53

What are isoprenoids?

Back 53

straight chain of carbon atoms with a methyl branch on every fourth column. Some of the most important hydrocarbons in organic geochemistry. Ranges from 6 to 40 carbon atoms

Front 54

What does the GC-MS reveal about petroleum?

Back 54

Carbon preference
pristane-phytane ratio
abundance of heavier waxy compounds
history of oils.

Front 55

What is shale?

Back 55

minerals (clay and others) + organic matter + pore water (free water + bounded water to grain surfaces)

Front 56

What are clay minerals?
What are the basic building blocks of clay minerals?

Back 56

silicate layer'd sheets (layer of tetrahedral silica or layer of octahedral gibbsite)

silica tetrahedron
aluminum octahedron

Front 57

What is isomorphous substitution?

Back 57

the replacement of one ion for another of similar size within the crystalline structure of the clay. This changes the total charge and location of the charge on the mineral (which changes the properties of the clay)

Front 58

What is bounded water?
What is constitutive water?

Back 58

structured water + mobile water in the interlayer of clays

water in the octahedral layer

Front 59

What are the two types of general clay minerals?
What are some examples of each?

Back 59

1:1 clays (one tetrahedral sheet for each octahedral sheet)

Kaolinite

2:1 Clays (two tetrahedral sheets for each octahedral sheet)

Smectite, vermiculite, illite, chlorite

Front 60

What are some changes that occur to clays with burial?

Back 60

pore-fluid pressure and temperate increases
porosity decreases
pore size decreases
sediments compact
size of organic molecules decrease

Front 61

What clays have one stage of dewatering?
What clays have two stages of dewatering?

Back 61

Illicit or kaolinitic clays (one stage)
Smectitic clays (two stages)

Front 62

What are the main ideas behind primary migration?

Back 62

Majority of theories involves combinations of kerogen networks, pressure build-up resulting in micro cracks with subsequent movement of hydrocarbons.

Front 63

What are the IUPAC Pore classifications and sizes?

Back 63

Macropores > 50 nanometers
Mesopores = 2 - 50 nanometers
Micropores 0.8 - 2 nanometers
ultramicropores < 0.8 nanometers

Front 64

What are the effective moleuclar diameters for water, nitrogen, CO2, methane, and ethane?

Back 64

Water = .3 nanometer
Nitrogen = .3 nanometer
CO2 = .47 nm
methane = .38 nm
ethane = .55 nm

Front 65

Natural fractures allow what to occur?

Back 65

enhanced primary hydrocarbon migration
make the source rock more compliant

Front 66

What creates the force to expel hydrocarbons from the source rock?

Back 66

The volume generated by the expansion of kerogen and fluids. This extra volume creates fractures to reduce pressure and allows hydrocarbons to flow

Front 67

What is the driving force of primary migration?

Back 67

hydrocarbon generation

Front 68

What are the primary migration methods?

Back 68

Gas phase, oil phase, diffusion, and solution

Front 69

What is the driving force of secondary migration?

Back 69

buoyancy and water flow

Front 70

What is a restraining force on petroleum migration?
What causes it to increases?

Back 70

Capillary Pressure

Increases with decreasing pore throat size, increasing interfacial (surface ) tension, and increasing wettability

Front 71

If the rock is water wet what is the interfacial tension angle?
If the rock is oil wet what is the interfacial tension angle?

Back 71

water wet < 90
oil wet > 90

Front 72

What is the simplest model for secondary migration based on?

Back 72

Based on buoyancy and assumes that petroleum moves vertically until it hits a barrier then follows the steepest gradient along the barrier

Front 73

What is the degree of petroleum concentration?

Back 73

the ratio of generated petroleum from the effective drainage area to the volume of the trap

Front 74

Why are fault planes (in most cases) unable to focus or concentrate petroleum flow?

Back 74

They aren't planar or concave

Front 75

What are 2 requirements for a petroleum reservoir?

Back 75

Porosity, permeability, saturation, pressure, and temperature are at correct reservoir conditions
pore scale and large sacle reservoir connectivity and dynamics

Front 76

What are some requirements for seals?

Back 76

Need a high capillary entry pressure on thick laterally continuous ductile rocks
If the top seal is geometrically convex upward, no other seal is needed
lateral seals are needed for stratigraphic traps
base seals are not really needed

Front 77

What are the 4 types of traps?

Back 77

Structural (folds/faults)
Stratigraphic (facice changes, reef bulidup boundaries)
Combination (structural and stratigraphic)
Hydrodynamic

Front 78

What are some examples of the 4 types of traps?

Back 78

Structural : synclines, anticline,salt dome, faults
Stratigraphic: carbonate reef,pinch out, eolian dome, lateral facies change
Combination : uncomformity/fault

Front 79

What form does oil and gas migrate in pores?

Back 79

Stringer

Front 80

What determines the sealing capacity for a trap?

Back 80

the capillary entry pressure

Front 81

What influences porosity and permeability?

Back 81

mineralogy
texture
chemistry of pore fluids
temperature and pressure
depositional environments
compaction and lithification
diagenesis
tectonics
cementation
solution
biological processes

Front 82

Reservoir heterogeneity is largely determined by what?

Back 82

the original depositional environments. Geologic time and diagenesis have little impact on reservoir continuity

Front 83

What are the carbonate rock types?

Back 83

Mudstone, Wackestone, Packstone, grainstone, boundstone, crystalline

Front 84

What are the carbonate pore types?

Back 84

depositional
fracture
diagenetic
depositional/fracture
depsitional/diagentic
fracture/diagentic

Front 85

What is surface diagenesis for a carbonate system? subsurface diagenesis?

Back 85

karsting
thermochemical sulfate reduction

Front 86

What is reservoir description?

Back 86

the process of describing and quantifying the reservoir properties including their spatial distribution to predict what is between the wells

Front 87

What are the two types of quantitative models for reservoir description?

Back 87

Stochastic models (statistical distribution of sand and shale works for wells not spaced close together)
Deterministic models (give specific distribution of sand and shale, works for closely spaced wells)

Front 88

What is included in a reservoir description?

Back 88

Depositional environment
work flow (logs)
depositional system
main system (e.g. fluvial system)

Front 89

What are different types of reservoir models

Back 89

Structural/geological model
petrophysical model
reservoir fluid flow simulating and production