Sedimentary Resources Flashcards
Describe different types of resources hosted by sedimentary rocks.
Groundwater: Water present beneath Earth’s surface in soil pore spaces and fractures of rock formations.
Petroleum (crude oil): A naturally occurring yellowish-black liquid found in geological formations (reservoirs) between Earth’s surface.
Natural gas: A naturally occurring hydrocarbon gas mixture found in deep underground rock formations.
Coal: A combustible black/brown sedimentary rock formed as rock strata.
Ore: A natural occurrence of rock or sediment that contains sufficient economically important minerals, typically metals.
Explain the processes associated with groundwater aquifers and petroleum reservoirs.
Groundwater: Water present below the Earth’s surface in soil pore spaces and fractures of rock formations. It is stored in aquifers, which are underground layers of water-bearing permeable rock, rock fractures, or unconsolidated materials.
Petroleum reservoirs: Petroleum is formed from deeply-buried organic-rich source rocks. To form a petroleum reservoir, three conditions must be present: a source rock rich in hydrocarbon material buried deep enough, a porous and permeable reservoir rock to accumulate the petroleum, and a cap rock (seal/trap) to prevent the escape of petroleum to the surface.
Describe the relationship between fluid characteristics, rock characteristics, and hydraulic conductivity.
Hydraulic conductivity is a measure of the ease with which a fluid can move through pore spaces or fractures in rock formations. It depends on the fluidity of the fluid and the intrinsic permeability of the rock.
Fluidity refers to the ability of molecules to flow or glide past one another and depends on the density and viscosity of the fluid.
Intrinsic permeability is the ability of a porous material, such as a rock or unconsolidated material, to allow fluids to pass through it. It is related to the porosity of the rock.
Higher fluidity and higher intrinsic permeability result in higher hydraulic conductivity, indicating that fluids can flow more easily through the rock.
Explain how sedimentary characteristics control porosity and permeability, and give examples of environments that are likely to produce high-quality reservoir/aquifer rocks.
Sedimentary characteristics such as grain size, sorting, and rounding control porosity and permeability in sedimentary rocks.
Larger grains, well-rounded grains, and well-sorted grains tend to result in higher porosity because there are more spaces between the grains.
Sedimentary environments that are likely to produce high-quality reservoir/aquifer rocks include sand dunes and beaches, alluvial fans and braided rivers, and coral reefs.
