GEOL 404: FINAL EXAM
103 Cards in this Set
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What was the origin of Earth's Water?
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Water released in the partial melting of the mantle and the formation of the crust
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What are the two types of subsurface waters?
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Free Water and Interstitial or irreducible water
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What is the definition of interstitial or irreducible water?
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Water that is bonded to mineral grains- It cannot be removed during the production of oil and gas from a reservoir
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Compare the PH, SO4, bicarbonate, Ca+ and MG+, and Eh (concentration of electrons in groundwater) for meteoric water and connate water
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Meteoric Water- Low PH, high SO4 and biocarbonate ions, low Ca+ and Mg+, oxidizing)
Connate Water- exact opposite
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Rank salinity in brine, fresh water, and sea water in increasing order?
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FreshWater, Sea Water, and Brine
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Is salinity higher in shales or sands?
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Sands
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Does salinity increase or decrease with depth?
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Increase
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Classify the dominant sources for inert gases and hydrocarbons
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Inert Gases- Inorganic
Hydrocarbons- Mainly Organic
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What determines whether a hydrocarbon is classified as sweet or sour?
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The presence of hydrogen sulfide
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What is the definition of condensate?
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Gas at reservoir conditions, mixture of gas and liquid at the surface
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Rank Kerosene, gasoline, diesel fuel, lubricating oil, and residuum from low to high API gravity
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1. residuum 2. Heavy oils 3. Lubricating oils 4. Diesel Fuel 5. Kerosene 6. Gasoline
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Most oils are formed in what temperature window (celsius)
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60 to 160 degrees C
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Secondary porosity is the result of geologic processes most commonly due to what three things?
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1. Solution
2. Re crystallization and dolomitization
3. Fractures and joints
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What are the two types of secondary permeability?
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Fractures, Solution Vugs
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What has to happen with compaction so no overburden pressure builds up?
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The release of pore fluids has to keep pace with the rate of added overburden pressure
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What is the formula for effective pressure?
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Peff= Plitho-Ppore
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What is the formula for the hydrostatic pressure in a drilled well?
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Phyrdo(psi)= 0.052* Mw(lbm/gal)* TVD (ft)
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What are the two controlling factors on maturation of organic matter?
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Temperature and Time
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What four things do temperature of sedimentary basins depend on?
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1. Thermal Conductivity(and rock types)
2. Internal Heat Generation
3. Water Flow and Convective/advective heat transfer
4. Surface temperature change
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Name the source material for the four different kerogen types?
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Type 1- Mainly Algae
Type 2- Mainly plankton, some contribution from algae
Type 3- Mainly higher plants
Type 4- Reworked, oxydized material
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What are three types of explanations of level of uncertainties in petroleum systems and their symbols?
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Known (!)
Hypothetical (.)
Speculative(?)
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What are the three ways in which basins are classified?
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1. Type of crust
2. Position of basin relative to plate margin
3. Type of plate interactions occurring during sedimentation
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Whats an example of the passive rifting style sedimentary basin?
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Mid-Atlantic Ocean Rift and drift system initiated in the jurassic
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What's an example of the active rifting caused by thermal doming sedimentary basin?
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North Sea, Rhine Graben, Gulf of Suez, East African Rift Valleys
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What's an aulacogen?
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Triple Junction
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Examples of narrow rift basins?
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1. Newark Rift Basin
2. Upper Rhine Rift Basin
3. Suez Rift Basin
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What are some examples of extended rift sedimentary basins?
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Nevada Basin and Range Province
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What is another name for an extended rift?
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Super detachment basin
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What is the definition of an intracratonic sag?
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Defined as being located entirely on continental crust in areas of divergence.
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What are some examples of sedimentary basins that can be classified as intracratonic sag?
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Michigan and Williston Basins
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Where do epicratonic basins lie?
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Partly on continental crust, partly on oceanic
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One big example of epicratonic basin?
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Gulf of Mexico
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Continental strike-slip basins (Conservative Boundaries) common characteristics
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Frequently asymmetric, generally very deep, often have high heat flows
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Examples of strike-slip basins (conservative boundaries)?
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Los Angeles, Dead Sea,
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What is a distinguishing characteristic of fore-arc basins?
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Their extreme length
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How do fore-arc basins form?
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Oceanic plate subducts beneath either continental or oceanic plate
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What are foreland basins usually marked by?
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A major asymmetric down-warping with one margin marked by termination against the outer side by a thrust belt.
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What is an example of a foreland basin?
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Western Canada Sedimentary Basin
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What are the three burial stages of source rock?
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1. Diagenesis
2. Catagenesis
3. Metagenesis
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What is the y and x axis on a Van Krevelen Diagram?
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Y axis Hydrogen/Carbon ratio, X axis oxygen/carbon ratio
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What does humic organic material turn into?
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Coals and Gases
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What does sapropelic kerogen turn into?
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Liquid and Gaseous hydrocarbons
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What are the three burial stages of source rock?
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1.Diagenesis
2. Catagenesis
3. Metagenesis
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What two things do the size of molecules affect?
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Viscosity and Volatility (ease of which they evaporate)
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Describe examples of each length of chain molecules
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short- gases form like methane (less viscous and more volatile)
moderate length chain- occur in liquid form such as gasoline and oils
Long chain molecules- solid forms such as tar and asphaltene
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What are the pressure and temperatures (relative) of diagenesis, catagenesis, metagenesis?
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Diagenesis- normal T&P, Catagenesis- Increase in T&P, Metagenesis- High T
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What is type II Kerogen common in?
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Oil shale deposits
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How is TOC measured in a rock?
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Pyrolysis
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Rich source rocks are primarily concentrated in which stratigraphic interval?
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Phanerozoic
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What are the three main factors that petroleum source rocks during the phanerozoic occur?
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1. Eustacy (rise and falls of sea levels)
2. Subsidence (divergent plate tectonics and collapsing shelf margins)
3. Climate (Global green-house vs. polar conditions)
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Which period is associated with some of the largest concentrations of source rocks?
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Cretaceous Period
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What two factors made cretaceous period such a prolific source rock period?
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1. cretaceous seafloor spreading and the creation of divergent continental margins
2. Global warming and the persistent rise of sea levels causing large scale transgressions
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Which stage is organic matter transformed into kerogen?
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Diagenesis
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Which stage does kerogen turn to oil and gas?
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Catagenesis
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Which stage does kerogen become overcooked and turn into carbon?
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Metagenesis
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What two things does TOC measure?
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Amount of Kerogen and bitumen that form to make carbon in a rock
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Which three things does kerogen degradation depend on?
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1. Temperature
2. Heating rate or time
3. Kerogen Type and Amount
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What do the three peaks for pyrolysis source rock evaluation tell, (S1, S2, S3)?
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S1- Represents the free hydrocarbons present in the rock
S2- Represents the amount of hydrocarbons generated from the kerogen in the rock and is a measure of the remaining generative capacity
S3- Represents the oxygen content of the kerogen
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What are the two basic building blocks for clay mineralogy?
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The silica tetrahedron (Si) and the aluminum octahedron (Ai)
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What are the categories of clay minerals 1:1 clays and 2:1 clays referring to?
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(one tetrahedral sheet for each octahedral sheet) and (two tetrahedral sheets for each octahedral sheet)
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Whats the best example of a 1:1 clay?
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Kaolinite
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Which types of clays have one stage dewatering?
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Illitic or kaolinitic
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Which type of clay has two stage dewatering?
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Smectitic Clays
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What is the relationship between the number of carbons and the expulsion efficiency?
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As the number of carbons increases, the expulsion efficiency will decrease
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What two primary migrations methods are relevant for only small, soluable HC?
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Diffusion and Solution
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What are the four methods of primary migration?
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1. Gas phase
2. Oil Phase
3. Solution
4. Diffusion
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What are the major factors (5) controlling micro fracturing- induced expulsion in source rocks?
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1. Pressure change
2. Kerogen quality
3. Hydrocarbon type or quality
4. Kerogen conversion fraction
5. Source Rock Compliance
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Is movement through fractures within the source rock considered primary or secondary migration?
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Secondary migration
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What is tertiary migration?
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Movement of a previously formed oil and gas accumulation either to a fresh trap or leakage to the surface
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What is the main driving force of secondary migration?
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buoyancy caused by density difference between oil and formation water
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What are the three parameters that control secondary migration?
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1. Buoyant Rise
2. Capillary Pressures that determine multiphase flow
3. Hydrodynamic fluid flow
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When does a hydrostatic condition exist and when does a hydrodynamic condition exist?
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Hydrostatic- Exists as long as the aqueous pore fluids in the subsurface are stationary, and the only driving force for secondary migration is buoyancy
Hydrodynamic Conditions exist if there is water flow in the subsurface and the buoyant rise of oil and gas is modified by this water flow
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What do orthocontour lines depict?
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Maximum Dip
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Describe the meniscus in water wet and oil wet systems as convex or concave?
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Water wet pore systems=convex. Oil wet system= concave
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If theta is less than 90, is it water wet or oil wet?
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Water wet- theta less than 90. Oil Wet- greater than 90.
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Which is better for oil recovery, water wet or oil wet rocks?
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Water wet
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What is the relationship between capillary pressure of a reservoir and pore throat diameter?
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Capillary pressure of a reservoir increases with decreasing pore size
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What type of fluid is injected into a core plug to determine its capillary pressure characteristics?
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A non-wetting fluid such as mercury
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What is main driving force of sealing?
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buoyancy
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What is the main restricting force of seals?
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Capillary or displacement pressure
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When does a capillary seal occur in relation to capillary pressure and buoyancy pressure?
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A capillary seal only occurs when the capillary pressure across the pore throats is greater than the buoyancy pressure of the migrating hydrocarbons
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What is the relationship between pore throat and capillary pressure?
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The smaller the pore throat the higher the capillary pressure so the better the seal
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What six characteristics do good seals have?
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1. Small pore throats without large connected pores
2. Homogeneous both vertically and laterally
3. Laterally continuous
4. Thick beds
5. No bypass systems
6. Water wet to increase capillary effects
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What are the four different types of traps?
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1. Structural
2. Stratigraphic
3. Combination
4. Hydrodynamic
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How are diapiric traps formed?
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Upward movement of sediments that are less dense than those overlying them
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If the buoyant force of the hydrocarbon column exceeds the resistant force of the displacement pressure in a lateral seal what will happen?
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Oil and gas could leak laterally up dip through the displacement pressure barrier and continue to migrate up dip through the reservoir carrier beds
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What are two examples (geographically) that represents gravitational structures?
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Gulf of Mexico and Niger Delta
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How are diapiric traps formed?
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Produced by the upward movement of sediments that are less dense than the ones overlying them
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What are clastic reservoir rocks composed of?
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Silicates
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What is the usual clastic reservoir?
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sandstone
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What is the main component of sandstone reservoirs?
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Quartz
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What is the name of the scale for the fourth order heterogenity?
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Microscropic (um to mm scale)
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What is the name of the 3rd order heterogenety scale?
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Mesoscopic
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What is another name for second order heterogenety?
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Macroscopic (cm to m)
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Rank Hexagonal, rhombohedral, and cubic packing in order from greatest to least permeability
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Cubic Packing, Hexagonal packing, Rhombohedral Packing
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How does pressure solution affect sandstone reservoirs?
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It greatly reduces the porosity and permeability of sandstones
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Are feldspar grains and calcite cements relatively unstable or stable under surface conditions of high temperature and pressure?
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Unstable
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What is the usual porosity range for petroleum reservoirs?
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10 to 20 percent
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How should core plugs be cut for optimum results?
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Core plugs should be cut either parallel or perpendicular to the bedding planes or lamination
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What does the mesoscopic (3rd order heterogeneity) scale encompass?
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Cores and well logs
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What are the smallest to largest component layers of a clastic sand waves, dune, ripples etc?
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Smallest - Laminae, laminae sets, beds, beds sets largest
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What does "bell-shaped" or "x-mas tree" shape infeer when describing a gamma ray curve?
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Fining Upwards
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What does a "funnel" or "inverted x-mas tree" signify about a gamma ray log?
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coursing upwards
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GEOL 404: EXAM 1