In porous rocks

Natural Gas Natural gas is a combustible gas that occurs in porous rock of the earth s crust and is found with or near accumulations of crude oil. It may occur alone in separate reservoirs, but more commonly it forms a gas cap entrapped between petroleum and an impervious, capping rock layer in a petroleum reservoir. Under high-pressure conditions, it is mixed with or dissolved in crude oil. Natural gas termed dry has less than 0.013 dmVm (0.1 gaLlOOO fF) of gasoline. Above this amount, it is termed wet. 

Klinkenberg, L. J. (1951). Analogy between diffusion and electrical conductivity in porous rocks. Bull. Geol. Soc. Am. 62,559-563. 

High pressure equipment has been designed to measure foam mobilities in porous rocks. Simultaneous flow of dense C02 and surfactant solution was established in core samples. The experimental condition of dense CO2 was above critical pressure but below critical temperature. Steady-state CC -foam mobility measurements were carried out with three core samples. Rock Creek sandstone was initially used to measure CO2-foam mobility. Thereafter, extensive further studies have been made with Baker dolomite and Berea sandstone to study the effect of rock permeability. 

In many cases the medium in which the molecules move is not homogeneous and the diffusion motion of the molecules is influenced by the structure of the medium. Examples are the diffusion of water and oil in porous rock or in water-oil emulsions. Many publications have shown that the NMR diffusion results can be used to quantitatively study the porous structure, like the determination of pore and droplet sizes, pore connectivity and pore hopping or of the surface to volume ratio of the pores. 

Magnetic resonance dispersion is a useful aid in the characterization of liquids in porous rocks from which one may extract oil however, the method... 

Mineral wax yellow to dark brown, solid substances that occur naturally and are composed largely of paraffins usually found associated with considerable mineral matter, as a filling in veins and fissures or as an interstitial material in porous rocks. 

Coalbed Methane (CBM) A natural methane gas that is found in coal seams, while traditional natural gas deposits are trapped in porous rock formations. A small amount of CBM is already produced successfully in the Rocky Mountain region of the U.S. 

Swanson, B.F. (1979) Visualizing pores and nonwetting phase in porous rock. J. Petro. Tech. 31, 10-18... 

Asphalt is a natural dark-colored solid made of complex hydrocarbons. This material occurs in solid form, sometimes called asphaltum or gilsonite, or in liquid form when heated. The latter may form pools at the ground surface, like those at La Brea in Los Angeles, California. Asphalt is most often found at or near the Earth s surface, the result of the natural break-down of petroleum. It is sometimes concentrated in porous rock. 

These great differences are due to "sweep," "adverse mobility ratios," "conformance," and other fluid mechanical effects (see next section) that are exacerbated by the natural heterogeneities in porous rocks and whose alleviation is the purpose of sweep and mobility control technology. 

David C., Wong T., Zhu W., and Zhang J. (1994) Laboratory measurement of compaction-induced permeability change in porous rock implications for the generation and maintenance of pore pressure excess in the crust. Pure Appl. Geophys. 143, 425-456. 

Wen, B., 1997a. Physico-chemical modelling of the natural ionic flotation of metals by gas bubbles in porous rocks. In Abstracts of the All-Russian Scientific-Practical Conference of Young Scientists and Specialists, "Geophysics-97". VIRG Rudgeofizika, St.Petersburg, pp. 44-45 (in Russian). 

Natural subsurface reservoir of crude oil. The oil is always accompanied by water and often by natural gas all are confined in porous rock, usually sedimentary rocks such as sands, sandstones, arkoses, and fissured limestones. 

The next question regards the means by which values of any of these quantities to be used in reservoir-engineering calculations may be obtained. There is a continuing history of theoretical attempts to calculate the mobility of foam starting from known quantities and familiar principles of two-phase flow in porous rocks. One of these principally considers the effect of capillary pressure and concludes that this quantity is a principal determinant of the stability and therefore of the population of lamellae. Presuming equilibrium conditions in which the radii of curvature of the Plateau boundaries determines the excess of absolute pressures in the gas over that in the liquid, Khatib et al. (16) computed a limiting value of the capillary pressure. Above this value, the lamellae become too thin for the surfactant to stabilize. Increasing the gas fractional flow decreases the water saturation and raises the capillary pressure. 

Methane formed millions of years ago from microscopic underwater plants and bacteria that dropped to the bottom of the ocean when they died. Over millions of years, they were crushed and heated by the pressure of layers of sand, dirt, and other materials that accumulated on top of them. The mineral components of the undersea mud gradually turned into a type of rock known as shale. Some of the organic components turned into natural gas, which is mostly methane. The natural gas became trapped in porous rocks called reservoir rocks and in larger pockets of the rock called reservoirs or geologic traps. Natural gas is now found in... 

Gundersen, E., Renard, F., Dysthe, D.K., Bj0rlykke, K. Jamtveit, J. 2002a. Coupling between pressure solution creep and diffusive mass transport in porous rocks. Journal of... 

The mass balance of fluid in porous rock can be written as ... 

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