Regional permeability estimates from investigations of coupled heat and groundwater flow, north slope of alaska

Abstract

Earlier studies of terrestrial heat flow in the North Slope Basin, Alaska, found that heat flow varies systematically in a trend perpendicular to the strike of basin strata and the neighboring Brooks Range. Heat flow (~+20%) increases from a low of 27 mW/m 2 in the foothills of the Brooks Range in the south to a high of 90 mW/m 2 on the coastal plain to the north. The thermal pattern can be explained by a regional-scale (-330 km) groundwater flow system which transports heat by advection from regions of high elevation in the Brooks Range and its foothills to lower elevations on the Arctic coastal plain. Permeability data from 2031 core measurements made parallel to bedding and 15 well tests were compiled for 10 geologic units. Arithmetic-mean permeabilities derived from measurements on core samples range from 2.2 x 10 -13 m 2 for sandstones of the Endicott Group to 1.1 x 10 -16 m 2 for limestones of the Lisburne Group. The arithmetic-mean permeability derived from all 2031 core measurements made parallel to bedding is 6.1 x 10 -14 m 2. A numerical model of coupled heat and fluid flow in the North Slope Basin was constructed and a series of model simulations were conducted. A model simulation incorporating permeability data obtained from core measurements resulted in a good match to observed heat flow data, apparently suggesting that permeability in the North Slol•. Basin does not increase significantly from the core scale (~10-2 -10-1 m) to the basin scale (~105 -106 m). This inference, however, is complicated by the possible effects of factors such as sample bias in measurements and choice of an appropriate averaging algorithm. A further series of model simulations were done in which the specified model permeability was homogeneous and anisotropic. Comparisons of heat flow predicted by these simulations with heat flow determined in field studies suggested that the effective basin-scale permeability parallel to bedding (kx) is in the range of 2.5 x 10-14 < kx < 2.5 x 10 -13 m 2 and permeability perpendicular to bedding (kz) is in the range of 1.0 x 1• -16 < kz < 5.0 x 10-16 m2. These constraints depend upon the explicit assumption that groundwater flow is the only mechanism responsible for heat flow variations across the North Slope Basin. migration of hydrocarbons [Hubbert, 1953; Toth, 1988; Garven, distances over which permeability can be directly measured. For 1989; Bethke eta/., 1991; Meissner, 1991]. Crustal fluids are also example, Garven [1989] showed that the formation of the giant involved in virtually all aspects of sedimentary diagenesis and oil sands deposits of Alberta may have been the result of oil play a critical role in the genesis of hydrothermal ore deposits transport by a gravity-driven flow system through the western 'Also at U.S. Geological Survey,

Examining geological controls on baseflow index (BFI) using regression analysis: An illustration from the Thames Basin, UK

“…10 -1 to 10 -8 m/s (Manning and Ingebritsen, 1999, Figure 1), for estimated basin scale values of hydraulic conductivity, e.g. 10 -7 to 10 -11 m/s (Willet and Chapman, 1989;Deming, 1993), and for modelled values of 'equivalent hydraulic conductivity' of heterogeneous sedimentary sequences, e.g. 10 -7 to 10 -8 m/s (Zhang et al, 2007).…”

Numerical simulation of magmatic hydrothermal systems

“…Research studies that attempt to characterize specific systems should include sensitivity analyses in order to explore the full range of conditions that can explain observed phenomena. Formal sensitivity analysis can help identify the appropriate degree of generality for system‐specific modeling and will typically reveal, for instance, that only one to two values of system permeability can be legitimately constrained [e.g., Deming , 1993]. More geometrically complex and heterogeneous models can be useful for heuristic purposes but are generally nonunique.…”

Pore fluid geochemistry from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

“…A topographically driven northward flow of meteoric water could have been active for the past 110 Ma (Hanor et al, 2004). This system is likely to still be actively driving a groundwater flow that is recharged at higher elevations in the Brooks Range and discharges at lower elevations near the Arctic coastal plain (Deming, 1993).…”

“…Uplift and subaereal erosion during the geologic evolution of the basin is thought to have induced significant meteoric flow, which may have displaced some of the older more marine formation fluids (Hanor et al, 2004). A northward topographically driven fluid flow is thought to have been active for the last 110 Ma, as the fluvialdeltaic Brookian systems began prograding from the Brooks Range (Hanor et al, 2004;Deming, 1993).…”