Aquifers formations

A series of processes will control the behaviour of C02 in saline aquifer formations. First, the C02 will displace the formation water (brine) originally in place and will lead to a local increase in pore fluid pressure (van der Meer, 1992). The injected C02 will not be distributed evenly, but will finger out, owing to the lower density than the pore waters and the heterogeneities of the aquifer. Doughty et al. (2001) point out that the shape of the C02 plume in the aquifer will be highly site- and case-specific. Carbon dioxide will rise to the top of the aquifer and migrate at the bottom of the... 

Suaveplane, C., 1984, Planning Test Analysis in Fracture Aquifer Formations State of the Art and Some Perspectives Ground Water Hydraulics, Water Resources Monograph Series No. 9, pp. 171-206. 

Aquifers for gas storage were first used in 1946 in Kentucky (United States). They are around 80 storage facilities in aquifers in the world today, most of them in the United States, the former Soviet Union and Western Europe (France, Germany and Italy). The principle of aquifer storage is to create an artificial gas field by injecting gas into the voids of an aquifer formation (involved gas volumes are similar to depleted fields). For this reason, the following geological conditions are necessary ... 

Geochemical reactions can change the hydraulic properties of the aquifer (formation damage) and therefore result in fluid migration to overlying USDW. 

Figure 5.2.1 Conceptual framework of the complex system of groundwater and aquifer formations...

FIGURE 4.1 Tube wells sunk into arsenic-containing aquifer formations may yield water contaminated by toxic soluble arsenic. Use of the water for irrigation can contaminate soil with arsenic and provide a pathway for arsenic to get into food crops such as rice. The problem has been especially acute in Bangladesh, but has occurred in other parts of the world as well. 

Water on and beneath the surface of the geosphere plays a strong role in pollution and the distribution of toxic substances. Toxic substances from wastes improperly disposed to the geosphere can leach into groundwater and contaminate water supplies. Radioactive radium resulting from the decay of uranium in aquifer formations has caused some groundwater sources of drinking water to be abandoned. 

Brine Analyses in Various Michigan Aquifer Formations... 

Data gathering in the water column should not be overlooked at the appraisal stage of the field life. Assessing the size and flow properties of the aquifer are essential in predicting the pressure support which may be provided. Sampling of the formation water is necessary to assess the salinity of the water for use in the determination of hydrocarbon saturations. 

Hydrocarbon-water contact movement in the reservoir may be determined from the open hole logs of new wells drilled after the beginning of production, or from a thermal decay time (TDT) log run in an existing cased production well. The TDT is able to differentiate between hydrocarbons and saline water by measuring the thermal decay time of neutrons pulsed into the formation from a source in the tool. By running the TDT tool in the same well at intervals of say one or two years (time lapse TDTs), the rate of movement of the hydrocarbon-water contact can be tracked. This is useful in determining the displacement in the reservoir, as well as the encroachment of an aquifer. 

The term aquifer is used to denote an extensive region of saturated material. There are many types of aquifers. The primary distinction between types involves the boundaries that define the aquifer. An unconfined aquifer, also known as a phraetic or water table aquifer, is assumed to have an upper boundary of saturated soil at a pressure of zero gauge, or atmospheric pressure. A confined aquifer has a low permeabiUty upper boundary that maintains the interstitial water within the aquifer at pressures greater than atmospheric. For both types of aquifers, the lower boundary is frequendy a low permeabihty soil or rock formation. Further distinctions exist. An artesian aquifer is a confined aquifer for which the interstitial water pressure is sufficient to allow the aquifer water entering the monitoring well to rise above the local ground surface. Figure 1 identifies the primary types of aquifers. 

Nested wells can also be used to analyze multilayer aquifer flow. There are many situations involving interaquifer transport owing to leaky boundaries between the aquifers. The primary case of interest involves the vertical transport of fluid across a horizontal semipermeable boundary between two or more aquifers. Figure 4 sets out the details of this type of problem. Unit 1 is a phraetic aquifer, bound from below by two confined aquifers, having semipermeable formations at each interface. 

The demand for gas is highly seasonal. Thus pipeline companies economi2e by si2ing production faciUties to accommodate less than the system s maximum wintertime demand. Underground storage faciUties are used to meet seasonal and daily demand peaks. In North America, gas is stored in three main types of underground formations depleted oil or gas fields, aquifers that originally contained water, and caverns formed by salt domes or mines. 

Adsorption of Metal Ions and Ligands. The sohd—solution interface is of greatest importance in regulating the concentration of aquatic solutes and pollutants. Suspended inorganic and organic particles and biomass, sediments, soils, and minerals, eg, in aquifers and infiltration systems, act as adsorbents. The reactions occurring at interfaces can be described with the help of surface-chemical theories (surface complex formation) (25). The adsorption of polar substances, eg, metal cations, M, anions. A, and weak acids, HA, on hydrous oxide, clay, or organically coated surfaces may be described in terms of surface-coordination reactions ... 

Porous Media Packed beds of granular solids are one type of the general class referred to as porous media, which include geological formations such as petroleum reservoirs and aquifers, manufactured materials such as sintered metals and porous catalysts, burning coal or char particles, and textile fabrics, to name a few. Pressure drop for incompressible flow across a porous medium has the same quahtative behavior as that given by Leva s correlation in the preceding. At low Reynolds numbers, viscous forces dominate and pressure drop is proportional to fluid viscosity and superficial velocity, and at high Reynolds numbers, pressure drop is proportional to fluid density and to the square of superficial velocity. 

Another problem is when the carbon dioxide content of natural gas is too high and must be lowered to produce pipeline-quality gas. Although the current practice is to vent this CO, sequestration of CO, in underground geologic formations is being considered. Already, in the Norwegian sector of the North Sea, CO, has been injected into saline aquifers at a rate of 1 million tons a year to avoid... 

C22-0083. Many places have underground water, called aquifers, that can be tapped using wells. Depending on the types of geological formations above these aquifers, water from the surface may or may not reach these underground reservoirs. How could radioactive tracers be used to determine if rainwater falling on a particular location makes Its way down into an aquifer beneath that location ... 

An aquifer is in practice defined to be a limited geological formation from which ground water can be pumped by using water wells. 

There are two kinds of aquifers. If the groundwater stands in direct contact with the atmosphere as in the figure above, the aquifer is regarded as unconfined. If, on the other hand a permeable formation below the groundwater table is covered by a less permeable layer, the aquifer is regarded as confined, see Figure 33. 

Subsurface formations can be divided into the overburden (unconsolidated) and bedrock according to its solidarity. The upper subsurface can be further divided into the unsaturated zone and the saturated zone depending on pore structure and moisture saturation. The saturated zone is the zone in which the voids in the rock or soil are filled with water at a pressure greater than atmospheric. The water table is at the top of a saturated zone in an unconfined aquifer. The unsaturated zone is the zone between the land surface and the water table, and is also called the zone of aeration or the vadose zone. The pore spaces contain water at less than atmospheric pressure, air, and other gases. This zone is unsaturated except during periods of heavy infiltration. 

The relative importance of pressure and gravitational heads depends on whether the water formation is in a free water table condition or in a confined aquifer condition. 

The Eh of connate waters (water entrapped in the interstices of sediment at the time of deposition) ranges from 0 to -200 mV. For example, formation water from two monitoring wells in the lower limestone of the Florida aquifer near Pensacola ranged from +23 to -32 mV,67 and formation fluids from a Devonian limestone in Illinois used for injection at a depth of about 3200 ft had an Eh of -154 mV.16... 

---