Permeability basin-scale

Permeabilities in sedimentary basins are known to vary with the scale of observation (e.g. Bredehoeft et al., 1983,1992 Chapman et al, 1991 Neuzil, 1986). Different techniques are being developed to estimate reservoir- and basin-scale permeabilities, e.g. computer-aided techniques based on relations between characteristics of depositional systems and permeability distribution (Weber, 1982,1987 Stam, 1989 Stam et al., 1989 Mijnssen, 1991), and techniques based on numerical simulations of basin-scale groundwater flow in combination with known groundwater pressure distributions (e.g. Bredehoeft et al., 1983, 1992 Burrus et al., 1991), techniques that use numerical models of coupled groundwater flow/heat flow and known thermal characteristics to estimate basin-scale permeabilities (Chapman et al., 1991). 

Chapman, D.S., Willet, S.D. and C. Clauser, 1991. Using thermal fields to estimate basin-scale permeabilities. In England, W.A. and Fleet, A.J. (eds.), 1991. Petroleum Migration. Geological Society Special Publication, no. 59, pp. 123-125 Chebotarev, 1.1., 1955. Metamorphism of natural waters in the crust of weathering. 

Diffusional transfers of potassium and silicon between sandstones and shales may be sufficient to accomplish feldspar dissolution, illitization, and quartz cementation (Thyne, 2001 Thyne et al, 2001). Losses of the magnitude observed for detrital carbonates in shales exceed the capacity of diffusion-mediated transfer. Large-scale advection seems required, although our understanding of shale permeabilities seems to preclude this (Bjprlykke, 1989, 1993 and Lynch, 1997). The possibility of convection driven by salinity heterogeneity within thick shale sequences has been demonstrated by Sharp et al (2001), who note that more information for rock properties and fluid compositions within deep basinal shales is needed before the generality of their results can be assessed. 

Various direct and indirect methods are generally used to determine the permeability of a sedimentary basin. The direct methods include laboratory measurements on core samples wire-line formation tests, single-well tests and interference tests. The data from the different types of well test and interference test can be analysed and interpreted by well-established procedures (Da Prat, 1990 Earlougher, 1977 Kruseman et al., 1990 Matthews and Russel, 1967). The conventional, indirect methods are theoretical, semi-empirical and empirical procedures which are based on the relation between permeability, grainsize characteristics and porosity (e.g. the Kozeny-Carman method, Domenico and Schwartz, 1990 Van Baaren method. Van Baaren, 1979). The laboratory methods and the conventional indirect methods provide permeability values which are representative of only a very small portion of the subsurface (cm-scale). The single-well test and interference test provide information representative of a larger volume of the subsurface (m - km scale). 

On a regional scale, there is an apparent correlation between the extent of mixing and the gross permeability of individual units. For example, Mississippian units and the Sawtooth Formation have a relatively high permeability as compared to the Bow Island Formation. Indications from the SD data (Fig. 10) are that these deeper units also have a higher proportion of meteoric water. Thus, it appears that the pattern of basin flushing depends upon the broad-scale features of hydraulic conductivity. The higher conductivity elements of the flow system represent pathways for initial and continued introduction of meteoric water to the basin. 

Fracturing and fault compartmentalization of sandstones fundamentally affects reservoir properties and may significantly influence the fluid migration pathways in a basin (Knipe, 1993). Open fractures may form high-permeability conduits, whereas cement-sealed fractures form barriers to fluid flow. Seismic, petrophysical and reservoir performance data allow regional (field-scale) effects of faulting on fluid flow to be constrained. However, much fracturing and associated cementation may occur at sub-... 

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