Permeability rock formation

Deep-Well Injection Deep-well injection for the disposal of liquid wastes involves injecting the wastes deep in the ground into permeable rock formation (typically limestone or dolomite) or underground caverns. 

The key questions to be addressed are how large is the world s geological storage capacity and does it occur where it is needed Not all sedimentary basins are suitable for the containment of carbon dioxide. Some are too shallow and others are dominated by rocks with low permeability or poor confining characteristics. Favourable basins have permeable rock formations saturated with saline water (saline formations), extensive covers of low-porosity rocks ( caprock , which serves as a seal to retain the gas) and structural simplicity. 

The drilling fluid provides hydrostatic pressme to prevent ground water and other fluids from entering into the bore hole from the surrounding permeable rock formations. 

With regard to hydrogeological studies for current project, there are at least two different aquifers in the investigated area A shallow aquifer and other confined by low permeability rock formations. The shallow aquifer is located in the alluvium quaternary deposits, which have a permeability grade dependent by the percentage of fine fraction. The deep aquifer is located in more permeable rock formations such as sandstones and conglomerates and confined by low permeability rock formations as marlstone and claystone. 

Hydraulic fracturing is a method of stimulating production of oil or gas from rock formations. A fluid is pumped under conditions of high pressure and high rate Into the formation to fracture it. The fluid also carries sand or a similar proppant material into the fractures. When the pumping is stopped and the hydraulic pressure is released at the wellhead, the fracture partially closes on the sand leaving a highly permeable channel for the oil or gas to flow back to the well. 

This equation defines the permeability (K) and is known as Darcy s law. The most common unit for the permeability is the darcy, which is defined as the flow rate in cm3/s that results when a pressure drop of 1 atm is applied to a porous medium that is 1 cm2 in cross-sectional area and 1 cm long, for a fluid with viscosity of 1 cP. It should be evident that the dimensions of the darcy are L2, and the conversion factors are (approximately) 10 x cm2/darcy C5 10-11 ft2/darcy. The flow properties of tight, crude oil bearing, rock formations are often described in permeability units of millidarcies. 

By far the most widespread use of NMR in an on-line production environment is the utilization of downhole exploration tools by petroleum service companies such as Schlumberger, Halliburton, and Baker Hughes. Articles on these unilateral NMR systems are found in the patent databases, " academic literature, and on-line resources provided by the exploration companies. The references provided here are just a few examples in a very prolific field. The technique is applied in high-temperature and pressure situations and currently is used down to a depth of about 10 km (6 miles) to produce a picture of water/oil content in the adjacent rock formations as well as to derive permeability, diffusivity, and hydrocarbon chemistry information. Mobile unilateral NMR systems such as the NMR-MOUSE are also being developed in order to take benchtop NMR systems into the field to perform analysis of geological core samples at the drill site. NMR analyzers are also being developed to determine the bitumen content and properties in tar sand production and processing. " " ... 

SERF is not appropriate for treatment in nonpermeable or low permeability strata such as rock or thick clay layers. Fractured rock formations and geological structures with high permeability tunnels within them would cause preferential steam flow and would not allow most areas of soil to be appropriately treated by the technology. 

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 permeability upper boundary that maintains the interstitial water within the aquifer at pressures greater than atmospheric. For both types of aquifers, the lower boundary is frequently a low permeability 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. 

Alkaline solutions erode formation rocks and clays. In some cases, the permeability could be increased owing to the erosion. In most cases, permeability is reduced because eroded rocks and clays migrate and block pore throats. The permeability reduction in low permeabihty rocks is higher than that in high permeability rocks, as shown in Figure 13.36. The reason is that the pore throats... 

The third equation above describes a reaction that helps the oil industry extract more oil from a well. For oil to be pumped from deep in the earth to the surface, it must first seep through underground rock formations to the base of the oil well s pipes. Limestone, which is composed of CaC03, can be made more permeable to oil by pumping hydrochloric acid down into the limestone formations, converting the insoluble calcium carbonate to soluble calcium chloride. 

Aquifer layers in the underground are built up of unconsolidated formations, such as gravel, sand or silt, or semi-consolidated or fissured hard rock formations that are permeable enough to store and transmit noticeable quantities of groundwater. Therefore, the geological conditions, in particular the lithological composition, the bedding... 

Equation 71 is the basic equation that relates permeability of a porous medium to its other properties. However, equation 71 contains the hydraulic diameter of the passage (pore), tortuosity, and areal porosity of the medium, which may not be easily accessible. For example, sandstones or rock formations have irregular pore structure and often have inconsistent pore size measurement values (see previous section). It is rather difficult to measure the average hydraulic pore diameter. On the other... 

Permeability for a Rock Formation. For natural consolidated porous medium, however, the definitions of the equivalent spherical diameter and the specific surface area per unit volume are not widely used because of its difficulty in determination and relation to other measurable quantities. Just to serve as a comparison, we give the permeability equation based on the previous passage model with the tortuosity given by equation 61 and assuming that the areal porosity equation 54 still holds. The permeability can then be given by... 

Production of petroleum is often hampered by damage to the permeability of reservoir rocks resulting from interaction of injected fluids with the porous rock formation. Fine particles of clays and other minerals are often found attached to the pore walls of reservoir rocks. The interaction between injected fluids and the rock can cause their movement by a combination of mechanical shear forces, colloid-chemical reactions and geochemical transformations. This chapter reviews several different aspects of the fines migration process. 

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