GEOL 404 FINAL EXAM QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026

GEOL 404 FINAL EXAM QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026 Petroleum exploration needs huge up-front capital investment and has great risk of drilling dry holes which could lead to business failure. Risk analysis in petroleum geology to reduce such risks has the following five components: - Answers source rock, reservoir rock, structural trap, seal and timing The four levels of petroleum investigation proceed in the following order: - Answers Sedimentary basin, petroleum system, play, prospect Plate tectonics is important in petroleum system analysis, because it helps to determine ________. - Answers sedimentary basin types, source property, reservoir types and structure types To know the "Period" names and times of the Phanerozoic is very important because ______________. - Answers the knowledge of the stratigraphic column is needed to calibrate the occurrence of the five system elements including the critical "timing" ______________ is mostly composed of granites, related igneous and metamorphic rocks, as well as sedimentary rocks. - Answers continent crust __________ is thicker than __________. _______ is denser than ______. - Answers continent crust, oceanic crust; oceanic crust, continental crust Higher a mountain, shallower its root. - Answers False Passive margins are usually formed during the stage of _____ in Wilson cycle. - Answers sea floor spreading Foreland basins are usually formed during the stage of _____ in Wilson cycle. - Answers Continental Collision Rocks tend to be more ductile as depth increases to the lower part of the crust or the upper mantle because _______. - Answers both temperature and pressure increase Sandstone usually has more fractures and faults than shale because ____ - Answers shale is more ductile than sandstone Normal faults are produced by _____ - Answers tensional stress Rocks tend to be more ductile as depth increases to the lower part of the crust or the upper mantle because _______. - Answers both temperature and pressure increase Sandstone usually has more fractures and faults than shale because ____ - Answers shale is more ductile than sandstone Normal faults are produced by _____ - Answers tensional stress For conventional hydrocarbon exploration, oil/gas reserves are trapped in __________. - Answers anticlinal structures instead of synclinal ones The San Andreas fault is ________________. - Answers a right lateral fault. __________ is to reveal the present position of rock strata and deformational features and uses the sea level as the datum. - Answers Structural cross-section __________ can use any regionally prominent bed as a relative datum to reveal the depositional history and features of the rock layers below the datum. - Answers stratigraphic cross-section __________ is to reveal the areal shapes of a formation top (surface). - Answers structural map An isopach map is a contour map of ______ whereas an isochore map is a contour map of ________. - Answers true stratigraphic thickness; true vertical thickness A net sand map is a contour map of ______ whereas a net pay map is a contour map of ________. - Answers the sand:shale ratio of a formation; the gross pay : net pay ratio of a reservoir Coarse-grained sand is deposited in _____________ environment. - Answers high energy Clay is deposited in _____________ environment. - Answers low energy Limestone is formed from calcite ______________. - Answers transported by water and precipitated organically from solution. Shale is formed from clay ______________. - Answers transported by water as mineral grains. Permeability is affected strongly by _________. - Answers porosity and grain size as well as sorting Channel bars are formed in _________ whereas point bars in _____. - Answers braided stream systems; meandering river systems Deposition of turbidites is usually found in _______. - Answers deep-marine fan A limestone called mudstone is usually formed ___________. - Answers down the slope During a core description work, you find a coarsening upward sequence which is a characteristic of ________. - Answers sea level fall During a core description work, you find a fining upward sequence which is a characteristic of ________. - Answers sea level rise Gravity survey can be used to map large-scale subsurface structures because it senses ___________. - Answers the density difference between stratas Magnetic survey can be used to map large-scale subsurface structures because it senses ___________. - Answers iron content difference between stratas Seismic survey can be used to map detailed subsurface structures because it senses ___________. - Answers acoustic impedance difference between stratas Mudcake is one of the four important zones in borehole environment. In which formation do expect thick layer of mudcake on the borehole wall? - Answers porous sandstone When you measure the conductivity of a solution in a container, you find its conductivity is very high, which lead yo to conclude: The most favorable scenario is that ___________. - Answers its salinity is high and temperature is high Conductivity of the formation in an uninvaded zone increases _________. - Answers as the conductivity of the formation water, water saturation and porosity increase Conductivity of the formation in an invaded zone increases _________. - Answers as the conductivity of the mud filtrate, mud filtrate saturation and porosity increase Sxo measures the mud filtrate saturation in the invaded zone which is ____________________, whereas Smo is _________. - Answers water and movable hydrocarbon; movable hydrocarbon From the spectral gamma ray log, the K-TH log gives a good indication of __________ whereas the very high U log reading means ___________. - Answers clay content; high organic content. Density log gives ____________, Pe log gives ____________, and neutron log gives _____________. - Answers bulk density; matrix density; porosity Which of the following statements is not true? - Answers Seismic waves travel faster in the crust than in the mantle. Which of the following statements is true? - Answers Continental crust has high silica and aluminum content. Which one of the following shows the correct order of the Wilson Cycle? - Answers Continental rifting, seafloor spreading, ocean closing, arc-continent collision, continent-continent collision. Which one of the following statements is true? - Answers Shale is more ductile than sandstone. Which of the following statements is true? - Answers A reverse fault is produced by compression. For conventional hydrocarbon exploration, oil/gas reserves are trapped in __________. - Answers anticlinal structures instead of synclinal ones A geologist walking across a plain observed the age change of the eroded outcrops in the following order: Permian, Triassic, Jurassic, Triassic, Permian. The geologist concluded that the eroded structure - Answers a syncline. Which of the following statements is true? - Answers Isopach map shows contours of true stratigraphic thickness of a formation. __________ is to reveal the shapes of a formation top (surface). - Answers structural map A net sand map is a contour map of ______ whereas a net pay map is a contour map of ________. - Answers the sand:shale ratio of a formation; the gross pay : net pay ratio of a reservoir Compared to clastic rocks, evaporites precipitated inorganically from solution are _________. - Answers excellent seal rock. When sediments are moved from the source to the ocean, _________________ - Answers coarse-sized grains are deposited nearer to the source than fine-sized grains. Clay is deposited in _____________ environment, whereas organic matter is deposited in _____________ environment. - Answers low energy; low energy Limestone is formed from calcite ______________. - Answers transported by water and precipitated organically from solution. Shale is formed from clay ______________. - Answers transported by water as mineral grains. Permeability is affected strongly by _________. - Answers porosity and grain size as well as sorting In exploration, a thick coal deposit is found. A geologist concluded that the depositional environment is _________________. - Answers terrestrial What is the correct order of the following facies from land towards basin? - Answers Beach, Lagoon, Reef, Slope Deposition of turbidites is usually found in _______. - Answers deep-marine fan An unconformity is ______________________. - Answers a surface in rock succession indicating a time gap caused by uplifting, folding and erosion or non-deposition An oil reservoir has an average porosity 20%. The water resistivity Rw at the reservoir temperature is 0.02 ohm.m. Let both the cementation exponent (m) and the saturation exponent (n) be 2, tortuosity (a) be 1. If the true formation resistivity Rt measured from well logging is 50 ohm.m, calculate the oil saturation. - Answers 0.9 There are two reservoir units in an oil field. The upper unit is a sandstone reservoir and the lower unit is a carbonate reservoir. The water saturation estimated from well log data is 30% in both reservoir units. However, the saturation of movable fluid in the flushed zones of the sandstone reservoir is 45% whereas the saturation of movable fluid in the flushed zones of the carbonate reservoir is 35%. What is the recovery factor in the sandstone and carbonate reservoir respectively? - Answers 21% and 7% Sound wave transmission in rocks is affected by _________. - Answers lithology, fluid type and amount, pressure, porosity, rock structure Compressional wave is related to _________ and shear wave is caused by ________. - Answers volumetric and shape changes; shape change only Sound wave travels faster in rocks of ________ porosity. - Answers smaller In electrical imaging logs, electric current is used to detect vuggs, fractures and other small-scale structures because ___________. - Answers these structures usually contain conductive fluids whereas dense rocks are resistive to electric current The T2 time in the NMR log is ________ in rocks containing more clay because _________. - Answers smaller; water molecules are bounded to the grains and not easy to move Clay particle in rocks is part of the __________________. - Answers solid matrix Connate water is _________________________. - Answers water that can potentially freely move like meteoric water but is trapped by surrounding rocks The state of hydrocarbon molecules in paraffins (i.e., gas, liqiud or solid), is determined by ______________. - Answers the carbon number By definition, "heavy oil" is ________ than water and "extra heavy oil" is _____________ than water. - Answers lighter; heavier During the burial of sediments and sedimentary rocks, compaction occurs in which __________ - Answers bulk rock mass gets more consolidated but the amount of solid mass does not change as the burial depth increases. A rock at a depth is overpressured if ____________ - Answers its pore pressure is greater than the hydrostatic pressure at the same depth. The temperature of a sedimentary basin is higher if ___________. - Answers it thermal conductivity is smaller and it has more internal heat generation Heat is conducted more efficiently in sedimentary rocks if they contain more _____. - Answers a lot