Simulated changes in water levels in the Minjur Aquifer, Riyadh area, Saudi Arabia

Williams, James F.; Sagaby, I.A.

doi:10.3133/ofr82371

Cited by 2 publications

(2 citation statements)

References 4 publications

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“…A 10‐m difference equates to approximately 15 psi above the actual water column pressure on a freshwater basis, representing an overestimate of pressure if a hydrostatic trend was datumed at ground level. At high elevations and rugged landscapes, for instance parts of the Arabian plate and the Rocky Mountains, the water table is tens or even hundreds of metres deeper than this (e.g., Quade et al, 1995; Williams & Al‐Sagaby, 1982). Water table depth may also vary locally by tens of metres or more on a decadal timeframe where rates of groundwater extraction exceed recharge (Ouda, 2014; Sultan et al, 2019).…”

Section: Hydrostatic Pressure Gradient Determinationmentioning

confidence: 99%

Hydrostatic pore water pressure revisited

Stewart

Albertz

2022

Basin Research

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Hydrostatic or “normal” pressure can be easily visualized as a water column with pressure given by ρgh and any departures classified as abnormal pressure. This is the basis for commonly used hydrostatic pressure depth trends in sedimentary basins that are constructed on assumptions of constant gradients and are datumed at mean sea level or ground level. But the straightforward water column concept does not upscale in a simple way to sedimentary basins where the zones of interest are several thousands of metres below the land or sea surface. Sedimentary basins are heterogeneous, including stacked, confined reservoirs and variations in pore water composition. It is possible to construct pressure‐depth profiles that honour the geology and hydrostratigraphy of a basin and these give different hydrostatic baselines from simple constant gradients hung from familiar local datums such as ground level. Key steps are using a reservoir‐specific datums such as the water table or potentiometric surface relevant to that unit, then building a pressure‐depth trend that represents the pore fluid salinity variation and density profile throughout the reservoir unit. At a given depth, this version of hydrostatic may predict pressures several hundred psi different from a single density gradient hung from a datum local to the well, and exhibit a notched profile reflecting the geological and hydrological stratigraphy. This construct redefines normal and abnormal pore fluid pressures in sedimentary basins. The impacts of this alternative approach to sedimentary basin hydrostatics, even if data are limited and pressure profiles have to be framed probabilistically, extend to many aspects of studying and interacting with fluid systems in sedimentary basins including basin modelling, petroleum systems analysis, well planning and well operations.

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Section: Hydrostatic Pressure Gradient Determinationmentioning

confidence: 99%

Hydrostatic pore water pressure revisited

Stewart

Albertz

2022

Basin Research

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“…This group has been extensively described in outcrop by Le Nindre et al ( , 1990, and is also referred to in GeoArabia publications concerning the Khuff Formation and Permian/Triassic boundary (Vaslet et al, 2005;Vachard et al, 2005;Crasquin-Soleau et al, 2006, Angiolini et al, 2006Nicora et al, 2006;Berthelin et al, 2006, Chirat et al, 2006 and in the Explanatory Notes to the BRGM-DMMR 1:250,000-scale geological maps of the Ba'qa , Qibah (Robelin et al, 1994), Buraydah (Manivit et al, 1986), Al Faydah (Vaslet et al, 1985a), Ad Dawadimi (Delfour et al, 1982) Ar Rayn (Vaslet et al,1983a, b), Wadi al Mulayh (Manivit et al, 1985), Sulayyimah (Vaslet et al, 1985b) and Wadi Tathlith (Kellogg et al, 1986) quadrangles. Nevertheless, the amount of literature published on the Triassic formations overlying the Khuff Formation is very limited, particularly concerning the Minjur Sandstone, even though this is one of the main aquifers supplying water to the city of Riyadh (Sogreah, 1967(Sogreah, , 1968Mott MacDonald, 1975, Williams, 1982El-Sharif, 1985;Al-Saleh, 1992;GTZ, 2010). The Minjur Sandstone is a complex assemblage of sandstone and shale with minor evaporites that was assigned by Le Nindre (1987) to a dominantly fluvial-deltaic system.…”

Section: Introductionmentioning

confidence: 99%

Managing clastic reservoir heterogeneity I: Sedimentology and sequence stratigraphy of the Late Triassic Minjur Sandstone at the Khashm al Khalta type locality, Central Saudi Arabia

Issautier

Nindre

Memesh³

et al. 2012

GeoArabia

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The Late Triassic (Norian–Rhaetian) Minjur Sandstone provides a remarkable case study for understanding and modelling the spatial distribution of sand bodies in a fluvial-deltaic system. As such it has been studied in connection with the geological storage of CO2 in complex heterogeneous formations. Detailed sedimentological mapping of the formation’s vertical and lateral variations in and around the type section at Khashm al Khalta (Khashm al Minjur), which is the area of interpreted maximum inlet/outlet activity, has provided a relatively detailed picture of the sequence stratigraphy. As originally described, shallow-marine flooding with the development of tidal mud flats and carbonate facies occurred near the middle of the formation, splitting it into a lower member dominated by subtidal, brackish and scattered fluvial environments, and an upper member marked by the appearance of meandering point bars capped upward by very proximal deposits forming thick (20 m) coarse-grained sandstone bars that can be followed over several kilometers. The general trend at formation scale is thus upward thickening and coarsening sedimentation related to an increasing clastic influx and the development of fluvial systems, with the fluvial upper member being dominated by amalgamated sand bars. The sequence stratigraphy indicates nine depositional sequences involving four depositional environments: sabkha, tidal, estuarine and fluvial-continental. The lower Minjur is a transgressive tract of four sequences of which Sequence 4 reflects maximum flooding and correlates with maximum flooding surface (MFS) Middle Norian Tr80. Sequence 5 corresponds to a meander system at the base of the upper Minjur, and is followed by sequences 6 to 9 reflecting an increasing clastic influx generating amalgamated coarse-grained bars. The upper Minjur thus represents a highstand systems tract.

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Simulated changes in water levels in the Minjur Aquifer, Riyadh area, Saudi Arabia

Cited by 2 publications

References 4 publications

Hydrostatic pore water pressure revisited

Hydrostatic pore water pressure revisited

Managing clastic reservoir heterogeneity I: Sedimentology and sequence stratigraphy of the Late Triassic Minjur Sandstone at the Khashm al Khalta type locality, Central Saudi Arabia

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