Saad Mogren

Hydrochemical Facies and Ionic Ratios of the Coastal Groundwater Aquifer of Saudi Gulf of Aqaba: Implication for Seawater Intrusion

ABSTRACT Batayneh, A.; Zaman, H.; Zumlot, T.; Ghrefat, H.; Mogren, S.; Nazzal, Y.; Elawadi, E.; Qaisy, S.; Bahkaly, I., and Al-Taani, A., 2014. Hydrochemical facies and ionic ratios of the coastal groundwater aquifer of Saudi Gulf of Aqaba: implication for seawater intrusion. It is now fairly documented that major ion chemistry of the groundwater can be used to determine an interaction between the groundwater and saline water in the costal aquifers, and that there exists a relationship between total dissolved solids and Cl−, Na+, Mg2+, and concentrations of groundwater. This hypothesis is tested on an aquifer located along the Saudi Gulf of Aqaba coast (Red Sea). Groundwater samples collected from 23 locations show the abundance of ions in the order of: Ca2+ > Na+ > Mg2+ > K+ = Cl− > > > . The Piper trilinear diagram reveals two dominant clusters, i.e. the Ca2+–Cl−– facies and the Na+–Cl−– facies. Besides the major chemical compositions, ionic ratios ( /Cl−, Na+/Ca2+, Na+/Cl−, Ca2+/Cl−, Mg2+/Cl−, K+/Cl−, /Cl−, Ca2+/Mg2+, Ca2+/ , and Ca2+/ ) are used to evaluate the effects of saline water intrusions. Factor analysis of the studied samples demonstrates that changes in the groundwater composition are primarily controlled by mineral dissolution, human activities, weathering of marine sediments, evaporation/salinization of groundwater, and the residence time of water. An attempt has been made to identify hydrochemical processes accompanied with the current intrusion of seawater through the use of ionic exchanges. Following this procedure, about 7.97% mixing rate of seawater intrusion has been estimated for the month of March 2012. Furthermore, the seawater mixing index has also been applied, which resulted in a range of values from 0.395 to 7.922. These results determine 13 of 23 groundwater samples (57%) as saline, with electrical conductivity > 3000 μS/cm.

Incipient status of dyke intrusion in top crust – evidences from the Al-Ays 2009 earthquake swarm, Harrat Lunayyir, SW Saudi Arabia

The 2009 earthquake-swarm in the Al-Ays volcanic zone in Harrat-Lunayyir in NW Saudi-Arabia is unique because of its intense character and focal-depth distribution at two depth bands (5–10 and 15–20 km) in upper crust without volcanic eruption. We investigate an anatomy of the dyke-intrusion model that supports the mechanism for the swarm itself with seismotectonics, pore pressure diffusion process and inference model. Inferred dyke-intrusion initially started at depth had a five-day peak period (15–20 May 2009) since inception of event-recordings, following which the activity diminished. The process of pore pressure perturbation and resultant “r–t plot” with modelled diffusivity (D = 0.01) relates the diffusion of pore pressure to seismic sequence in a fractured poro-elastic fluid-saturated medium. The spatio-temporal b-values show high b-values (>1.3) along the zone of dyke intrusion (length 10 km and height 5 km) at ∼20km depth. The main-shock and other prominent earthquakes originated on a moderate b-value zone (∼1.0). Temporal b-value analysis indicates an exceptionally low b-value (∼0.4) during the main-shock occurrence. The Al-Ays lava-field is inferred to underlie a seismic volume trending NW-SE bounded on both sides by two NW-SE trending fault systems, dipping 40–50° opposite to each other within a proposed nascent rift setting.

Analysis of well log and pressure data of the gas- bearing sand reservoirs of Kafr El-Sheikh formation: Case study from the off-shore Nile Delta-Egypt

The off-shore Nile Delta is one of the most promising areas for gas exploration and production in Egypt and the Middle East. The present study deals with evaluation of the gas-bearing sand anomalies at the off-shore Nile Delta of Egypt using the available well logging and the pressure datasets. The early to middle Pliocene sediments (Kafr El Sheikh Formation) of eleven wells scattered in the Darfeel and Port Fouad Concessions are analyzed and studied for determining the different petrophysical parameters necessary for reservoir evaluation. This study reveals the presence of three gas-bearing sand zones (anomalies-1, -2 and -3), with good hydrocarbon potential, encountered at different depth levels at the Early Pliocene sediments of Kafr El Sheikh Formation. The detailed petrophysical analysis of these zones shows that anomalies-1 and 2 attain good reservoir parameters, while anomaly-3 is not penetrated in majority of wells in the study area. However, anomaly-2 exhibits unique characteristics; in terms of the good porosity (27 to 33%), low shale volume (Vsh<10%) and high gas potentiality (42 to 93%), which it attains. The constructed petrophysical property maps of gas anomalies-1 and -2, reveal an observed diminish of gas saturation towards the eastern flank of the study area. The potential accumulations with the best reservoir cut-off parameters, are recognized in the central and western parts of Darfeel Concession. The analysis of pressure data is concerned mainly with locating the different fluid contacts and determining the pressure gradients of the gas-bearing zones. Very close pressure regimes are detected for most of the investigated gas anomalies through out the study area. Pressure gradient ranges of 0.331 to 0.345 psi/ft and 0.314 to 0.444 psi/ft are indicated for anomalies-1 and 2, respectively.

Structural Investigations of Afghanistan Deduced from Remote Sensing and Potential Field Data

This study integrates potential gravity and magnetic field data with remotely sensed images and geological data in an effort to understand the subsurface major geological structures in Afghanistan. Integrated analysis of Landsat SRTM data was applied for extraction of geological lineaments. The potential field data were analyzed using gradient interpretation techniques, such as analytic signal (AS), tilt derivative (TDR), horizontal gradient of the tilt derivative (HG-TDR), Euler Deconvolution (ED) and power spectrum methods, and results were correlated with known geological structures.The analysis of remote sensing data and potential field data reveals the regional geological structural characteristics of Afghanistan. The power spectrum analysis of magnetic and gravity data suggests shallow basement rocks at around 1 to 1.5 km depth. The results of TDR of potential field data are in agreement with the location of the major regional fault structures and also the location of the basins and swells, except in the Helmand region (SW Afghanistan) where many high potential field anomalies are observed and attributed to batholiths and near-surface volcanic rocks intrusions.A high-resolution airborne geophysical survey in the data sparse region of eastern Afghanistan is recommended in order to have a complete image of the potential field anomalies.

Structural interpretation of the Ifal Basin in north-western Saudi Arabia from aeromagnetic data: hydrogeological and environmental implications

The Ifal (Midyan) Basin is one of the well defined basins along the Red Sea coast, north-western Saudi Arabia. Location, geometry, thick sedimentary cover and structural framework qualify this basin for groundwater, oil and mineral occurrences. In spite of being studied by two airborne magnetic surveys during 1962 and 1983, structural interpretation of the area from a magnetic perspective, and its uses for hydrogeological and environmental investigations, has not been attempted. This work thus presents interpretation of the aeromagnetic data for basement depth estimation and tectonic framework delineation, which both have a role in controlling groundwater flow and accumulation in the Ifal Basin. A maximum depth of 3.5 km is estimated for the basement surface by this study. In addition, several faulted and tilted blocks, perpendicularly dissected by NE-trending faults, are delineated within the structural framework of the study area. It is also observed that the studied basin is bounded by NW- and NE-trending faults. All these multi-directional faults/fracture systems in the Ifal Basin could be considered as conduits for groundwater accumulation, but with a possibility of environmental contamination from the surrounding soils and rock bodies.

Utilizing potential field data to support delineation of groundwater aquifers in the southern Red Sea coast, Saudi Arabia

In this paper potential field data are interpreted to map the undulation of the basement surface, which represents the bottom of the water bearing zones, and to delineate the tectonic framework that controls the groundwater flow and accumulation in the southern Red Sea coastal area of Saudi Arabia. The interpretation reveals that the dominant structural trend is a NW (Red Sea) trend that resulted in a series of faulted tilted blocks. These tilted blocks are dissected by another cross-cut NE trend which shapes and forms a series of fault-bounded small basins. These basins and the bounded structural trends control and shape the flow direction of the groundwater in the study area, i.e. they act as groundwater conduits. Furthermore, the present results indicate that volcanic intrusions are present as subsurface flows, which hinder the groundwater exploration and drilling activities in most of the area; in some localities these volcanic flows crop out at the surface and cover the groundwater bearing formations. Furthermore, the gravity and magnetic data interpretation indicates the possible existence of a large structural basin occupying the southeastern side of the study area. This basin is bounded with NW and NE trending faults and is expected to be a good host for groundwater aquifers; thus it is a promising site for hydrogeological investigation.

Surface Soil Assessment in the Ubhur Area, North of Jeddah, Western Saudi Arabia, Using a Multichannel Analysis of Surface Waves Method

Ten boreholes drilled in Ubhur area up to the depth of bedrock indicted the shallow depth of bedrock where the average depth ranges between 10 and 15 m. The standard penetration test N-values of these boreholes were measured and averaged. Based on N-values to the depth of bedrock, Ubhur area can be classified as site class C and D. Multichannel analysis of surface waves technique has been applied along seventy six profiles using 24-channel geophone array and 4.5Hz vertical geophones with 1m geophone spacing and sledgehammer and/or weight drop as seismic energy sources. Values of shear wave velocity to 30 m are calculated and then averaged (Vs30) where it ranges between 310.08 m/s and 1139.8 m/s. Therefore, Ubhur area can be classified into site class B, C and D based on site classification of the national earthquake hazards reduction program (NEHRP) recommendations. Accordingly, the greatest part of the study area falls in site class C while class B and D covered limited areas in the western and the eastern parts respectively. Depending on the shallow depth of bedrock in the study area, the Vs30 parameter is not applicable in the study area so the average values of Vs for the soil thickness, excluding the bedrock, have been calculated and mapped for site class C and D only. So Vs30 approach is not applicable for areas with shallow depth of bedrock which gives higher classification.

Seismicity constraints on stress regimes along Sinai subplate boundaries

The relative movement between African, Arabian and Eurasian plates has significantly controlled the tectonic process of Sinai subplate region, although its kinematics and precise boundaries are still doubtful. The respective subplate bounded on both sides by the Aqaba-Dead Sea transform fault to the east and the Gulf of Suez, the only defined part, to the west. Seismicity parameters, moment magnitude relation and fault plane solutions were combined to determine the active tectonics along the aforementioned boundaries. Seven shallow seismogenic zones were defined by the heterogeneity in stress field orientations. Along the eastern boundary, the average fault plane solution obtained from the moment tensor summation (MTS) reveals a sinistral strike-slip faulting mechanism. The corresponding seismic strain rate tensor showed that the present tectonic stress producing earthquakes along the boundary is dominated by both NW-SE compression and NE-SW dilatation. Towards the north, the average focal mechanism showed a normal faulting mechanism of N185°E compression and an N94°E extension in the Carmel Fairi seismic zone. On the other hand, the active crustal deformation along the western boundary (Gulf of Suez region) showed a prevailing tensional stress regime of NE to ENE orientations; producing an average fault plane solution of normal faulting mechanism. The seismic strain rate tensor reveals a dominant stress regime of N58°E extension and N145°E compression in consistence with the general tectonic nature in northeastern Africa. Finally, the extensional to strike-slip stress regimes obtained in the present study emphasize that the deformation accommodated along the Sinai subplate boundaries are in consistence with the kinematics models along the plate boundaries representing the northern extremity part of the Red Sea region.

Statistical analysis of different chemical elements in groundwater of northwestern Saudi Arabia

A total of 72 water samples were collected from the sub-surface aquifer system in the Midyan basin and analyzed for 24 major, minor and trace elements. Histograms and normal quantile plots were used to delineate the sub-populations of the chemical constituents in the studied groundwater samples. Some of the elements such as Al, K, Ca, Mg, Na and Cl have concentrations that could be linked to the weathering of the surface rock strata. On the other hand, the elements like As, Pb and Sb have concentration, that can be linked to agricultural practices in the area. The use of simple statistical analysis, frequency histograms, and Q-Q plots were useful for the detection and evaluation of elemental constituents in the groundwater of the study area.

Water exploration using Magnetotelluric and gravity data analysis; Wadi Nisah, Riyadh, Saudi Arabia

Abstract Saudi Arabia is a desert country with no permanent rivers or lakes and very little rainfall. Ground water aquifers are the major source of water in Saudi Arabia. In the Riyadh region, several Wadies including Wadi Nisah store about 14 × 106 m3 of water, which is extracted for local irrigation purposes. In such areas, the water wells are as shallow as 200–300 m in depth. The importance of Wadi Nisah is because the subsurface water aquifers that are present there could support the region for many years as a water resource. Accordingly, in this study, we performed a Magnetotelluric survey using a portable broadband sounding system (MT24/LF) to evaluate the ground water aquifer at great depths. We collected 10 broadband Magnetotelluric sounding stations (1 station/day) with an interval of about 2–3 km reaching a profile length of about 25–30 km along Wadi Nisah. Additionally, we used available gravity data to image the subsurface structure containing the aquifer. MT results indicated a low resistivity layer, associated with alluvium deposits, which was defined at a depth of about 1–2 km and extended horizontally about 15 km. Gravity data analysis was used to model this resistivity layer indicating a basement surface at 3–4 km depth.