Seafloor seismic acquisition using autonomous underwater vehicles

Although narrow-azimuth towed-streamer data provide good image quality for structural interpretation, it is generally accepted that for wide-azimuth marine surveys seabed receivers deliver superior seismic reflection measurements and seismically derived reservoir attributes. However, seabed surveys are not widely used due to the higher acquisition costs when compared to streamer acquisition. In recent years, there have been significant engineering efforts to automate receiver deployment and retrieval in order to minimize the cost differential and conduct cost-efficient seabed receiver seismic surveys. These engineering efforts include industrially engineered nodes, nodes on a rope deployment schemes and even robotic nodes, which swim to and from the deployment location. This move to automation is inevitable, leading to robotization of seismic data acquisition for exploration and development activities in the oil and gas industry. We are developing a robotic-based technology, which utilizes autonomous underwater vehicles as seismic sensors without the need of using a remotely operated vehicle for deployment and retrieval. In this paper, we describe the autonomous underwater vehicle evolution throughout the project years from initial heavy and bulky nodes to fully autonomous light and flexible underwater receivers. Results obtained from two field pilot tests using different generations of autonomous underwater vehicles indicate that the seismic coupling, and navigation based on underwater acoustics are very reliable and robust.     

Morphometric analysis of Chattian–Early Aquitanian Miogypsinidae from Iraq and their stratigraphic distribution in the Arabian Tethys

A biometric study of Chattian–Early Aquitanian taxa from shallow marine transgressive carbonate deposits in the Oligo-Miocene sedimentary basin of Kirkuk, Iraq, provides new insight into their taxonomy, stratigraphy, and palaeobiogeography. Their evolution is based on a distinct change in general nepiont morphology, which agrees with the principle of nepionic acceleration. Each Miogypsinoides group is represented by more than one lineage. We demonstrate for the first time the parallel evolution of Miogypsina and Miogypsinoides in the late Chattian of north-eastern Iraq. We assign specimens into two lineage groups: Miogypsinoides formosensis of the Late Chattian, with smaller embryon and longer post-embryonic spirals, which evolved into Miogypsinoides bantamensis of the Early Aquitanian; and Miogypsinoides sivasensis, with shorter spirals and larger embryon, originally found in late Chattian to Early Aquitanian deposits. This group evolved into large embryon and longer post-embryonic spiral specimens of the upper Azkand Formation, assigned to Miogypsinoides dehaartii and associated with Miogypsina gunteri-basraensis and M. gunteri due to their peculiar morphological features. Miogypsina specimens are related to Miogypsina basraensis, which have much smaller embryon dimensions. This part of the sequence corresponds to Ms. formosensis and is overlain by a Miogypsina ex. interc. gunteri-basraensis succession, a composite species that evolved to Miogypsina gunteri, the most common Miogypsinids taxon in the carbonate upper Azkand Formation, thereby acting as a reference for the evolution of this taxon and its transition to M. ex. interc. tani-gunteri. Miogypsinoides evolution in the Iraqi sedimentary basin is similar to Western Tethys evolution yet differs from Indo-Pacific evolution.     

Impact of rock-water interactions and recharge on water resources quality of the Agadir-Essaouira basin,southwestern Morocco

The Agadir-Essaouira area in the occidental High Atlas Mountains of Morocco is characterized by a semi-arid climate. The scarcity and quality of water resources, exacerbated by long drought periods, constitute a major problem for a sustainable development of this region. Groundwater resources of carbonate units within Jurassic and Cretaceous aquifers are requested for drinking and irrigation purposes. In this study, we collected 84 samples from wells, boreholes, springs, and rivers. Hydrochemical and isotopic data were used to examine the mineralization and origin of water, which control groundwater quality. The chemical composition of water seems to be controlled by water-rock interactions, such as dissolution of carbonates (calcite and dolomite), weathering of gypsum, as well as ion exchange processes, which explain the observed variability. Stable isotopes results show that groundwater from the mainly marly Cretaceous aquifer are submitted to an evaporation effect, while samples from the chiefly calcareous Jurassic aquifer indicate a meteoric origin, due to a rapid infiltration of recharge runoff through the karstic outcrops. The low values of δ¹⁸O and δ²H suggest a local recharge from areas with elevations ranging from 400 to 1200 m for the Cretaceous aquifer and from 800 to 1500 m for the Jurassic units.     

Occurrence of jarosite within Quaternary coastal sabkha sediments in Kuwait,Arabian Gulf

X-ray diffractometer analysis and SEM investigation confirmed the occurrence of jarosite and alunogen minerals in the Quaternary siliciclastic sabkha sediments of northern Kuwait within the Bahrah oilfield area, Arabian Gulf. Jarosite is relatively abundant in a near-surface whitish sticky tidal muddy sand layer about 60 cm thick that overlies the ferruginous sandstone of the Oligo-Miocene Ghar Formation. Jarosite occurs as clusters of euhedral pseudo-cubes of about 1 μm in size and as agglomerated nanoglobules of 250 nm in size. A hypogenetic origin related to the reaction of sulfuric acid produced by the oxidation of H₂S associated with hydrocarbon gas seepages with K and Fe leachates is suggested. The restricted occurrence of jarosite within near-surface sabkha sediments may be attributed to limited tidal inundation and prevalence of arid climatic conditions.     

Status of sedimentation in King Talal Dam,case study from Jordan

This paper focuses on characterizing the current status of physical and chemical characteristics of King Talal Dam (KTD) sediments. The quality of sediments was investigated based on several international sediment quality guidelines. The volume of sediment and sedimentation rate in (KTD) was also estimated. Five types of granulometric textural facies were observed for the sediments of KTD reservoir bed, with an average grain size distribution of gravel (1.38%), sand (32.38%), silt (32.35%) and clay (32.38%). The fraction of <63 micron showed that the total mean size was 8.0 micron. Other sediment parameters in KTD were 7.0% for total organic matter (TOM), 7.3 for pH, 35.9% for CaCO₃ and 100.5 meq/100 g for cation exchange capacity, with dominant mineralogical constituents of quartz, calcite, dolomite, clay minerals and minor feldspar. The total concentrations of F, Cl, NO₂, NO₃, PO₄ and SO₄ in sediment samples were lower inward for KTD. The vast majority of trace metals in sediments were generally within the standard limits recommended for soils. TOM and grain size of sediment are major factors governing the trace metal concentrations. The calculated geoaccumulation index (I _geo) and enrichment factor of metals in bottom sediments showed that the metals were in the following order: Cd > Pb > Zn > Co > Cr > Ni > Fe > Cu > Sr > Mn and Cd > Zn > Pb > Co > Cr > Ni > Cu > Sr > Mn, respectively. Based on the sonic survey of KTD reservoir, the annual sedimentation rate was about 0.4061 MCM/year, in which about 18.66% of the reservoir initial storage capacity was lost to sediments and a projected lifespan of about 198 years.     

Numerical estimation of carbonate rock properties using multiscale images

Characterizing the pore space of rock samples using three‐dimensional (3D) X‐ray computed tomography images is a crucial step in digital rock physics. Indeed, the quality of the pore network extracted has a high impact on the prediction of rock properties such as porosity, permeability and elastic moduli. In carbonate rocks, it is usually very difficult to find a single image resolution which fully captures the sample pore network because of the heterogeneities existing at different scales. Hence, to overcome this limitation a multiscale analysis of the pore space may be needed. In this paper, we present a method to estimate porosity and elastic properties of clean carbonate (without clay content) samples from 3D X‐ray microtomography images at multiple resolutions. We perform a three‐phase segmentation to separate grains, pores and unresolved porous phase using 19 μm resolution images of each core plug. Then, we use images with higher resolution (between 0.3 and 2 μm) of microplugs extracted from the core plug samples. These subsets of images are assumed to be representative of the unresolved phase. We estimate the porosity and elastic properties of each sample by extrapolating the microplug properties to the whole unresolved phase. In addition, we compute the absolute permeability using the lattice Boltzmann method on the microplug images due to the low resolution of the core plug images. In order to validate the results of the numerical simulations, we compare our results with available laboratory measurements at the core plug scale. Porosity average simulations for the eight samples agree within 13%. Permeability numerical predictions provide realistic values in the range of experimental data but with a higher relative error. Finally, elastic moduli show the highest disagreements, with simulation error values exceeding 150% for three samples.     

Gravimetric monitoring of the first field‐wide steam injection in a fractured carbonate field in Oman – a feasibility study

Gas‐Oil Gravity Drainage is to be enhanced by steam injection in a highly fractured, low permeability carbonate field in Oman. Following a successful pilot, field‐wide steam injection is being implemented, first of this type in the world. A dedicated monitoring program has been designed to track changes in the reservoir. Various observations are to be acquired, including, surface deformation, temperature measurements, microseismic, well logs, pressure and saturation measurements to monitor the reservoir. Because significant changes in the reservoir density are expected, time‐lapse gravimetry is also being considered. In this paper we investigate the feasibility of gravimetric monitoring of the thermally enhanced gravity drainage process at the carbonate field in Oman. For this purpose, forward gravity modelling is performed. Based on field groundwater measurements, the estimates of the hydrological signal are considered and it is investigated under what conditions the groundwater influences can be minimized. Using regularized inversion of synthetic gravity data, we analyse the achievable accuracy of heat‐front position estimates. In case of large groundwater variations at the field, the gravity observations can be significantly affected and, consequently, the accuracy of heat‐front monitoring can be deteriorated. We show that, by applying gravity corrections based on local observations of groundwater, the hydrological influences can to a large extent be reduced and the accuracy of estimates can be improved. We conclude that gravimetric monitoring of the heat‐front evolution has a great potential.     

Concentration,composition and sources of PAHs in the coastal sediments of the exclusive economic zone (EEZ) of Qatar,Arabian Gulf

Surface sediments were collected from sixteen locations in order to assess levels and sources of polycyclic aromatic hydrocarbons (PAHs) in sediments of Qatar exclusive economic zone (EEZ). Samples were analyzed for 16 parent PAHs, 18 alkyl homologs and for dibenzothiophenes. Total PAHs concentration (∑PAHs) ranged from 2.6 ng g⁻¹ to 1025 ng g⁻¹. The highest PAHs concentrations were in sediments in and adjacent to harbors. Alkylated PAHs predominated most of the sampling locations reaching up to 80% in offshore locations. Parent PAHs and parent high molecular weight PAHs dominated location adjacent to industrial activities and urban areas. The origin of PAHs sources to the sediments was elucidated using ternary plot, indices, and molecular ratios of specific compounds such as (Ant/Phe + Ant), (Flt/Flt + Pyr). PAHs inputs to most coastal sites consisted of mixture of petroleum and combustion derived sources. However, inputs to the offshore sediments were mainly of petroleum origin.     

Geologic and hydrologic settings for development of freshwater lenses in arid lands

Satellite observations were used to test the validity of previously identified favourable conditions for the formation of freshwater lenses, identify additional potential occurrences, and model modern potential recharge in the Raudhatain Watershed (3696) in northern Kuwait. Favourable conditions include infrequent yet intensive precipitation events, drainage depressions to collect the limited runoff, and presence of conditions (e.g. high infiltration capacity) that promote groundwater recharge and preservation (e.g. underlying saline aquifer) of infiltrating groundwater as freshwater lenses floating over saline aquifer water due to differences in density. Specifically, the following field and satellite‐based observations were noted for the Raudhatain Watershed: (1) Over ~30 precipitation events were identified from the Tropical Rainfall Measuring Mission precipitation data (1998–2009); (2) slope is gentle (2 m/km), and the surface is largely (80%) covered by alluvial deposits with high infiltration capacities (up to 9 m/day); (3) no flows and long‐term ponding were reported at the watershed outlet or detected from Landsat thematic mapper images; (4) infiltration is high based on increases in soil moisture content (from an advanced microwave scanning radiometer) and vegetation index following large precipitation events; and (5) freshwater lenses that overlie highly saline [total dissolved solids (TDS): >35 000] unconfined aquifers underlying the watershed are absent in the southern regions, where infiltrating fresh water mixes with the less saline groundwater (TDS: <10 000). Twenty potential locations (size: 1 to 75 km²) for freshwater lens development were identified in northern Kuwait, and continuous rainfall–runoff models (Soil Water and Assessment Tool) were applied to provide a first‐order estimation of the average annual recharge in the watershed (127 × 10⁶ m³) and freshwater lenses (8.17 × 10⁶ m³). Results demonstrate the settings for enhanced opportunities for groundwater recharge, outline the amounts of and preservation conditions for the groundwater feeding the freshwater lenses, and highlight potential applications and locations of freshwater lenses in similar settings elsewhere in the Arabian Peninsula and beyond. Copyright © 2013 John Wiley & Sons, Ltd.     

Concentration of selected radionuclides in seawater from Kuwait

No baseline existed for the radionuclides in Kuwait territorial water. With changing trend in the region to embrace nuclear energy, the baseline study is imperative to create a reference and to record the influence-functioning of upcoming power plants. The first one in Bushehr, Iran is ready to start and several more are likely to come-up in UAE, Saudi Arabia and Kuwait. The present baseline concentration of the four considered radionuclide's show low concentration of tritium, polonium, strontium and cesium; their concentration is comparable to most oceanic waters.