Final answer:
An impermeable caprock is a non-porous layer that traps oil and natural gas in underlying permeable rocks below the Earth's surface. Permeability is necessary for fluids to flow through rock formations, and impermeable rock prevents this movement, making it essential for the containment of hydrocarbons. Hydraulic fracturing, or fracking, is used to extract these resources from rocks with low permeability.
Step-by-step explanation:
Impermeable Rock and Oil Deposits
An impermeable caprock is a geological formation that sits atop more permeable and porous rocks, containing oil and natural gas deposits. This impermeable layer prevents the hydrocarbons within the permeable rock from escaping to the surface. Permeability of a rock formation is critical; it is the measure of the rock's ability to transport fluids and is dependent on porosity and how interconnected the pores are. Highly permeable rocks, such as sandstone and limestone, often form aquifers that can yield significant amounts of water. On the other hand, impermeable rocks like shale, or un-fractured igneous and metamorphic rocks, act as confining layers, preventing fluid flow and trapping resources such as oil and gas below them.
In modern times, fracking is used to extract gas and oil from rocks with low permeability. This method creates fractures in the rock, enabling the trapped oil or gas to flow out. Despite the advances in technology, the extraction rate of oil and gas is limited by the natural properties of the rock, such as the thickness of the seam and its depth. Moreover, new techniques have increased the environmental risks associated with oil and gas extraction, as seen in significant spills and pollution.