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An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.
The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the locality. It can also be simply explained as the depth below which the ground is saturated.
Petroleum geology is the study of the origins, occurrence, movement, accumulation, and exploration of hydrocarbon fuels. It refers to the specific set of geological disciplines that are applied to the search for hydrocarbons.
In geology and sedimentology, connate fluids are liquids that were trapped in the pores of sedimentary rocks as they were deposited. These liquids are largely composed of water, but also contain many mineral components as ions in solution.
In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of "recognizing a commercial well when you drill one".
Hydrocarbon exploration is the search by petroleum geologists and geophysicists for deposits of hydrocarbons, particularly petroleum and natural gas, in the Earth's crust using petroleum geology.
Permeability in fluid mechanics, materials science and Earth sciences is a measure of the ability of a porous material to allow fluids to pass through it.
A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen is created in surrounding rock by the presence of high heat and pressure in the Earth's crust.
Pore water pressure refers to the pressure of groundwater held within a soil or rock, in gaps between particles (pores). Pore water pressures below the phreatic level of the groundwater are measured with piezometers. The vertical pore water pressure distribution in aquifers can generally be assumed to be close to hydrostatic.
In fluid statics, capillary pressure is the pressure between two immiscible fluids in a thin tube, resulting from the interactions of forces between the fluids and solid walls of the tube. Capillary pressure can serve as both an opposing or driving force for fluid transport and is a significant property for research and industrial purposes. It is also observed in natural phenomena.
In petrophysics, Archie's law is a purely empirical law relating the measured electrical conductivity of a porous rock to its porosity and fluid saturation. It is named after Gus Archie (1907–1978) and laid the foundation for modern well log interpretation, as it relates borehole electrical conductivity measurements to hydrocarbon saturations.
Petrophysics is the study of physical and chemical rock properties and their interactions with fluids.
Effective porosity is most commonly considered to represent the porosity of a rock or sediment available to contribute to fluid flow through the rock or sediment, or often in terms of "flow to a borehole". Porosity that is not considered "effective porosity" includes water bound to clay particles and isolated "vuggy" porosity. The effective porosity is of great importance in considering the suitability of rocks or sediments as oil or gas reservoirs, or as aquifers.
Drilling fluid invasion is a process that occurs in a well being drilled with higher wellbore pressure than formation pressure. The liquid component of the drilling fluid continues to "invade" the porous and permeable formation until the solids present in the mud, commonly bentonite, clog enough pores to form a mud cake capable of preventing further invasion.
Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current. In these logs, resistivity is measured using four electrical probes to eliminate the resistance of the contact leads. The log must run in holes containing electrically conductive mud or water, i.e., with enough ions present in the drilling fluid.
Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods. Most groundwater is clean, but groundwater can become polluted, or contaminated as a result of human activities or as a result of natural conditions.
Heavy oil production is a developing technology for extracting heavy oil in industrial quantities. Estimated reserves of heavy oil are over 6 trillion barrels, three times that of conventional oil and gas.
Fault zone hydrogeology is the study of how brittlely deformed rocks alter fluid flows in different lithological settings, such as clastic, igneous and carbonate rocks. Fluid movements, that can be quantified as permeability, can be facilitated or impeded due to the existence of a fault zone. This is because different mechanisms that deform rocks can alter porosity and permeability within a fault zone. Fluids involved in a fault system generally are groundwater and hydrocarbons.
Unconventional reservoirs, or unconventional resources are accumulations where oil and gas phases are tightly bound to the rock fabric by strong capillary forces, requiring specialized measures for evaluation and extraction.
Trapping mechanisms for carbon geosequestration prevent carbon dioxide stored in geological structures from leaking into the atmosphere. As a means to lower greenhouse gas emissions, carbon dioxide from carbon sequestration, especially in terms of carbon capture and storage, is able to be directed from power plants and other sources of greenhouse gas emissions, with carbon dioxide emissions being pumped into subterranean storage facilities. However, there is still the risk of the carbon dioxide leaking from the underground storage facilities. To address this, several trapping mechanisms have been proposed and researched.
References
- ↑ Watts, N.L. (1987-11-01). "Theoretical aspects of cap-rock and fault seals for single- and two-phase hydrocarbon columns". Marine and Petroleum Geology. 4 (4): 274–307. doi:10.1016/0264-8172(87)90008-0.
- ↑ "Burlage, Henry M. et al. Laboratory Manual for Introduction to Pharmacy. New York (330 West 42nd Street): McGraw‐Hill Book Company, 1956. 271 P. $4.50". Science Education. 41 (3). 1957-04-02. doi:10.1002/sce.37304103190. ISSN 0036-8326.
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