Sedimentary basin

Seward 1989, Naeser et al. 1990, Buane and Brown 1991, Naeser 1993, Issler at al. 

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Keywords plate tectonics, sedimentary basins, source rocks, maturation, migration, reservoir rocks, traps, seismic, gravity survey, magnetic survey, geochemistry, mudlogs, field studies. 

Several conditions need to be satisfied for the existence of a hydrocarbon accumulation, as indicated in Figure 2.1. The first of these is an area in which a suitable sequence of rocks has accumulated over geologic time, the sedimentary basin. Within that sequence there needs to be a high content of organic matter, the source rock. Through elevated temperatures and pressures these rocks must have reached maturation, the condition at which hydrocarbons are expelled from the source rock. 

The features created by crustal movements may be mountain chains, like the Himalayas, where collision of continents causes extensive compression. Conversely, the depressions of the Red Sea and East African Rift Basin are formed by extensional plate movements. Both type of movements form large scale depressions into which sediments from the surrounding elevated areas ( highs ) are transported. These depressions are termed sedimentary basins (Fig. 2.3). The basin fill can attain a thickness of several kilometres. 

Hydrocarbons are of a lower density than formation water. Thus, if no mechanism is in place to stop their upward migration they will eventually seep to the surface. On seabed surveys in some offshore areas we can detect crater like features ( pock marks ) which also bear witness to the escape of oil and gas to the surface. It is assumed that throughout the geologic past vast quantities of hydrocarbons have been lost in this manner from sedimentary basins. 

Even if all of the elements described so far have been present within a sedimentary basin an accumulation will not necessarily be encountered. One of the crucial questions in prospect evaluation is about the timing of events. The deformation of strata into a suitable trap has to precede the maturation and migration of petroleum. The reservoir seal must have been intact throughout geologic time. If a leak occurred sometime in the past, the exploration well will only encounter small amounts of residual hydrocarbons. Conversely, a seal such as a fault may have developed early on in the field s history and prevented the migration of hydrocarbons into the structure. 

Miall, Andrew (1984) Principles of Sedimentary Basin Analysis,468p, Springer Verlag North, F. K., (1985) Petroleum Geology, 607p, Allen Unwin... 

Figure 2-56 shows a plot of the theoretical maximum overburden pressure and the theoretical minimum pressure as a function of depth. Also plotted are various bottomhole fluid pressures from actual wells drilled in the Gulf Coast region [33]. These experimentally obtained pressures are the measurements of the pressures in the fluids that result from a combination of rock overburden and the fluid hydraulic column to the surface. These data show the bottomhole fluid pressure extremes. The abnormally high pressures can be explained by the fact that the sedimentary basins in the Gulf Coast region are immature basins and are... 

The fluid pressure in the rock at the bottom of a well is commonly defined as pore pressure (also called formation pressure, or reservoir pressure). Depending on the maturity of the sedimentary basin, the pore pressure will reflect geologic column overburden that may include a portion of the rock particle weight (i.e., immature basins), or a simple hydrostatic column of fluid (i.e., mature basins). The pore pressure and therefore its gradient can be obtained from well log data as wells are drilled. These pore pressure data are fundamental for the solution of engineering problems in drilling, well completions, production, and reservoir engineering. 

The constant value of 0.25 for Poisson s ratio versus depth reflects the geology and the rock mechanics of the mature sedimentary basin in the West Texas region. Since mature basins are well cemented, the rock columns of West Texas will act as compressible, brittle, elastic materials. 

The Cenozoic portions of the Gulf Coast sedimentary basins are immature therefore, little cementing of the sediments has taken place. Poisson s ratio varies with depth for such sedimentary columns, reflecting the variation of properties through the column. At great depth (i.e., approaching 20,000 ft), Poisson s ratio approaches that of incompressible, plastic materials (i.e., 0.5) [35]. 

Tar sands (oil sands) are large deposits of sand saturated with bitumen and water. Tar sand deposits are commonly found at or near the earth s surface entrapped in large sedimentary basins. Large accumulations of tar sand deposits are few. About 98% of all world tar sand is found in... 

The changes in stress fields, and intensities of igneous and hydrothermal activities seem to correlate to oscillatory motion of the Pacific plate (Jackson s episodes) (Jackson et al., 1975 Jackson and Shaw, 1975) (Masuda, 1984). Masuda (1984) and Takeuchi (1987) pointed out that the oscillatory motion of Pacific plate during the least 42 Ma correlates with magmatism, the intensity of tectonism, the change of stress field and the history of sedimentary basin in arc-trench system (Fig. 1.147). The above arguments also suggest that the mineralizations in arc and back-arc systems relate to the oscillatory motion of the Pacific plate. 

Masuda, F. (1984) Sedimentary basins in arc-trench system as a high-sensitive recorder of oceanic plate motion. Mining Geology, 34, 1-20 (in Japanese). 

Takeuchi, A. (1981) Temporal changes of regional stress field and tectonics of sedimentary basin. J. Geol. Soc. Japan, 87, 737-751 (in Japanese). 

Kreitler, C.W., Hydrogeology of sedimentary basins as it relates to deep-well injection of chemical wastes, in Proc. Int. Symp. Subsurface Injection of Liquid Wastes, New Orleans, National Water Well Association, Dublin, OH, 1986, pp. 398-416. 

Bachu S., Bonijoly D., et al. Screening and ranking of sedimentary basins for sequestration of C02 in geological media in response to climate change. 2003 Environmental Geology 44 277-289. 

KharakaY.K., Cole D.R., et al. Gas-water-rock interactions in Frio formation follow-ing C02 injection implication for the storage of greenhouse gase in sedimentary basins. 2006 Geology 34 577-580. 

Fig. 2.4. Example of a sliding-fugacity path. Deep groundwaters of a geopressured zone in a sedimentary basin migrate upward to lower pressures. During migration, CO2 exsolves from the water so that its fugacity follows the variation in total pressure. The loss of CO2 causes carbonate cements to form.

Bethke, C. M., M.-K. Lee and R. F. Wendlandt, 1992, Mass transport and chemical reaction in sedimentary basins, natural and artificial diagenesis. In M. Quintard and M. S. Todorovic (eds.), Heat and Mass Transfer in Porous Media. Elsevier, Amsterdam, pp. 421 —434. 

Bjorlykke, K. and P. K. Egeberg, 1993, Quartz cementation in sedimentary basins. American Association of Petroleum Geologists Bulletin 77,1538-1548. 

Harrison, W. J., 1990, Modeling fluid/rock interactions in sedimentary basins. In... 

Shock, E. L., 1988, Organic acid metastability in sedimentary basins. Geology 16, 886-890 (correction, 17,572-573). 

The Cretaceous sedimentary rocks of the Western Canada Sedimentary Basin (WCSB), renowned for their hydrocarbon resources, are seldom considered to have potential to host base metal sulphide mineralization. These sedimentary rocks have also discouraged those who presumed that the Precambrian rocks of the Canadian Shield to the east and north are more favourable hosts of base metal mineralization (ctMacqueen 1997). 

Paradis, S., Turner, W.A., Coniglio, M., Wilson, N. Nelson, J.L. 2006. Stable and radiogenic isotopic signatures of mineralized Devonian carbonates of the Northern Rocky Mountains and the Western Canada Sedimentary Basin. In Hannigan, P.K. (ed) Potential for carbonate-hosted lead-zinc Mississippi Valley-type mineralization in northern Alberta and southern Northwest Territories Geoscience Contributions,... 

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