ASBOG Ch. 6 - Economic Geology
Exam-Graded A
recoverable stock-tank oil - ANS-STO = A t (phi) So R / FVF
A = Area
t = thickness
(phi) = porosity of reservoir rock
So = oil saturation = 1 - water saturation
R = recovery factor
FVF = formation volume factor (expressed as a number slightly greater than 1)
U.S. barrels conversion - ANS-5.615 cubic feet = 1 U.S. barrel = 42 gallons
Describe the four recoverable resource classes for petroleum - ANS-1. *Production* is
the quantity of oil and natural gas already recovered
2. *Reserves* are resources that are commercially recoverable and remain to be
developed
3. *Contingent Resources* are less certain than reserves b/c there are technological,
environmental, or business hurdles. To be classified as contingent, there must be
evidence of an intention to proceed with development within a 5-yr time frame
4. *Prospective Resources* are undiscovered hydrocarbons whose volumes are
estimated and have not been drilled
5% to 30%, and most commonly 10% to 20% - ANS-Typical values of porosity for
reservoir rocks
magmatic segregation deposits - ANS-produced by differentiation or direct
crystallization of magmas
types of mafic magmatic segregation deposits - ANS-1. Layered mafic intrusions
2. anorthosites
3. kimberlites
4. carbonatites
5. ophiolites
6. intrusive igneous iron deposits
deposits associated with Felsic-Intermediate intrusions - ANS-1. Porphyry base metal
deposits
2. Skarns
3. Hydrothermal iron deposits
4. Cordilleran vein deposits
, Pegmatites - ANS-unusually coarse-grained igneous rocks that are important sources of
Be, Li, Rb, Ce, U, Th, REEs, Mb, Sn, Sb; crystal specimens and gemstones
Mississippi Valley Deposits - ANS-Type of deposit:
-Principle source of lead-zinc
-Occur in passive areas, such as craton of U.S.
-Deposits are laterally extensive but thin
Western States uranium, three regions provide >90% of U.S. production of uranium and
vanadium, and 40% of world's uranium - ANS-1. Roll-front deposits of Colorado and
Wyoming
2. Salt-wash type deposits of Utah
3. Humates from New Mexico
Athabascan uraniferous deposits in Saskatchewan, Canada - ANS-Uranium source in
Canada. Similar to U.S. deposits but at slightly higher temperatures
Deposits related to solution-remobilization - ANS-These deposits form from circulating
fluids that scavenge metallic ions from adjacent rock lithologies, dissolve, transport and
redeposit them in fractures as vein deposits
Subaerial volcanic deposits - ANS-formed by the eruption of intermediate to silicic
volcanic rocks at temperatures 100 to 200 degrees C. Most deposits are epithermal
Volcanogenic deposits - ANS-stratabound deposits formed underwater by volcanic
processes and the activities of thermal springs
types of volcanogenic deposits - ANS-1. volcanogenic massive sulfide deposits
2. exhalites
3. black-shale-hosted ores
Regional metamorphic deposits - ANS-typically form under high temperatures and
pressures. Two types:
1. Deposits in which new metamorphic rocks and minerals are formed by redistribution
of mineral components due to their increased chemical mobility
2. Deposits in which ore constituents mobilize and re-emplace
Types of chemical sedimentation deposits - ANS-1. Sulfide deposits
2. Black and phosphatic shales
3. Sed. iron ores - oolitic iron, siderite, limonite
4. Sedimentary manganese deposits
5. Phosphorus deposits
6. Evaporites
7. Manganese nodules
Exam-Graded A
recoverable stock-tank oil - ANS-STO = A t (phi) So R / FVF
A = Area
t = thickness
(phi) = porosity of reservoir rock
So = oil saturation = 1 - water saturation
R = recovery factor
FVF = formation volume factor (expressed as a number slightly greater than 1)
U.S. barrels conversion - ANS-5.615 cubic feet = 1 U.S. barrel = 42 gallons
Describe the four recoverable resource classes for petroleum - ANS-1. *Production* is
the quantity of oil and natural gas already recovered
2. *Reserves* are resources that are commercially recoverable and remain to be
developed
3. *Contingent Resources* are less certain than reserves b/c there are technological,
environmental, or business hurdles. To be classified as contingent, there must be
evidence of an intention to proceed with development within a 5-yr time frame
4. *Prospective Resources* are undiscovered hydrocarbons whose volumes are
estimated and have not been drilled
5% to 30%, and most commonly 10% to 20% - ANS-Typical values of porosity for
reservoir rocks
magmatic segregation deposits - ANS-produced by differentiation or direct
crystallization of magmas
types of mafic magmatic segregation deposits - ANS-1. Layered mafic intrusions
2. anorthosites
3. kimberlites
4. carbonatites
5. ophiolites
6. intrusive igneous iron deposits
deposits associated with Felsic-Intermediate intrusions - ANS-1. Porphyry base metal
deposits
2. Skarns
3. Hydrothermal iron deposits
4. Cordilleran vein deposits
, Pegmatites - ANS-unusually coarse-grained igneous rocks that are important sources of
Be, Li, Rb, Ce, U, Th, REEs, Mb, Sn, Sb; crystal specimens and gemstones
Mississippi Valley Deposits - ANS-Type of deposit:
-Principle source of lead-zinc
-Occur in passive areas, such as craton of U.S.
-Deposits are laterally extensive but thin
Western States uranium, three regions provide >90% of U.S. production of uranium and
vanadium, and 40% of world's uranium - ANS-1. Roll-front deposits of Colorado and
Wyoming
2. Salt-wash type deposits of Utah
3. Humates from New Mexico
Athabascan uraniferous deposits in Saskatchewan, Canada - ANS-Uranium source in
Canada. Similar to U.S. deposits but at slightly higher temperatures
Deposits related to solution-remobilization - ANS-These deposits form from circulating
fluids that scavenge metallic ions from adjacent rock lithologies, dissolve, transport and
redeposit them in fractures as vein deposits
Subaerial volcanic deposits - ANS-formed by the eruption of intermediate to silicic
volcanic rocks at temperatures 100 to 200 degrees C. Most deposits are epithermal
Volcanogenic deposits - ANS-stratabound deposits formed underwater by volcanic
processes and the activities of thermal springs
types of volcanogenic deposits - ANS-1. volcanogenic massive sulfide deposits
2. exhalites
3. black-shale-hosted ores
Regional metamorphic deposits - ANS-typically form under high temperatures and
pressures. Two types:
1. Deposits in which new metamorphic rocks and minerals are formed by redistribution
of mineral components due to their increased chemical mobility
2. Deposits in which ore constituents mobilize and re-emplace
Types of chemical sedimentation deposits - ANS-1. Sulfide deposits
2. Black and phosphatic shales
3. Sed. iron ores - oolitic iron, siderite, limonite
4. Sedimentary manganese deposits
5. Phosphorus deposits
6. Evaporites
7. Manganese nodules
