Economic Geology and Energy Flashcards

Which geologic structure is MOST favorable for trapping oil and gas in a conventional reservoir?

Answer: Anticline sealed by an impermeable caprock

An anticline capped by impermeable rock is the classic structural trap for hydrocarbons, as buoyant fluids migrate upward and accumulate.

In petroleum geology, 'source rock' refers to:

Answer: Fine-grained rock rich in organic matter that generates hydrocarbons upon burial and heating

Source rock is organic-rich fine-grained rock (typically shale) that generates oil and gas when thermally mature.

The Bingham Canyon copper mine in Utah is the world's largest man-made excavation and an example of which deposit type?

Answer: Porphyry copper

Bingham Canyon is a classic porphyry copper deposit formed by hydrothermal fluids from a Eocene intrusion.

Which parameter is used to describe the thermal maturity of organic matter in potential source rocks?

Answer: Vitrinite reflectance (%Ro)

Vitrinite reflectance (%Ro) measures how much incident light is reflected by vitrinite particles, indicating the degree of thermal maturation.

A 'placer deposit' forms primarily through which process?

Answer: Mechanical concentration of dense minerals by gravity in stream or beach sediments

Placer deposits form when dense, resistant minerals (e.g., gold, cassiterite, ilmenite) are concentrated by flowing water or wave action.

Mississippi Valley-type (MVT) lead-zinc deposits are typically hosted in:

Answer: Platform carbonate rocks (limestone and dolomite) in tectonically stable cratons

MVT deposits form in platform carbonate sequences when basinal brines migrate into structural or diagenetic traps in stable cratonic settings.

Coalbed methane (CBM) differs from conventional natural gas reservoirs primarily because:

Answer: The gas is adsorbed onto coal matrix rather than occupying pore space

CBM gas is stored by adsorption onto coal macerals rather than as free gas in pores, requiring dewatering to reduce pressure before gas desorbs.