“…This spectral sensor informs about the presence of K, U and Th in the formation along each borehole with a data point every 5 cm and a spatial resolution of 50 cm. The spectral approach based on 256 energy windows facilitates the determination of the relative contribution of the three elements to the SGR signal (Hesselbo, 1996) thus enabling the identification of zones with high Th and U content, potential sources of natural tracers (radium isotopes), and K-rich layers with higher clay content (Schlumberger, 2009). The Geovista EM51…”
“…This spectral sensor informs about the presence of K, U and Th in the formation along each borehole with a data point every 5 cm and a spatial resolution of 50 cm. The spectral approach based on 256 energy windows facilitates the determination of the relative contribution of the three elements to the SGR signal (Hesselbo, 1996) thus enabling the identification of zones with high Th and U content, potential sources of natural tracers (radium isotopes), and K-rich layers with higher clay content (Schlumberger, 2009). The Geovista EM51…”
“…Well logs (Gamma-ray (GR); Density (RHOB); Neutron (NPHI); PEF; Sonic (DT); Resistivity), core measurements and pressure data were used to evaluate main reservoirs and define the pay zones. First, the lithology of the main reservoir formations was identified using a combination of (Ditch Cuttings description, Core description, well log analysis, and cross plots) 22 . Then, the formation evaluation was conducted based on estimating the main petrophysical parameters: (Shale volume, effective porosity, net thickness, and fluid saturations) of the main reservoirs 23 .…”
Section: Methodsmentioning
confidence: 99%
“… Figure 1 ( a ) Location map of the study area. ( b ) Lithostratigraphic column of the Nile Delta in the Baltim region of Egypt (modified after 18 , 22 ). ( c ) The sequence stratigraphic framework cross section of Abu Madi Formation in Baltim Fields, offshore, Nile Delta, Egypt (Modified after 2 , 3 ).…”
Baltim Eastern and Northern gas fields in the offshore Nile Delta have very high gas condensate accumulations. Therefore, the present research evaluates Abu Madi and Qawasim Formations and defines the petrophysical parameters for them using various data from five wells composed of wireline logs (gamma-ray, density, neutron, sonic, resistivity), core data, pressure data, and cross-plots. In the current study, the formations of the main reservoirs were evaluated qualitatively and quantitatively based on the petrophysical analysis to assess the production potential. Based on the lithological identification, the two main reservoirs (Abu Madi and Qawasim Formations) are composed of sandstone, calcareous shale, and siltstone. The main petrophysical parameters (Shale volume, effective porosity, net thickness, and fluid saturations) were mapped to track the areal petrophysical variations in the field. The results of the petrophysical analysis reveal that the main reservoirs are promising for the hydrocarbon potential with effective porosity of 18%, low shale content with an average value of about 21%, higher gas saturation of average value of nearly 58%, net reservoir thickness ranges from 25.5 to 131.5 m, net pay thickness (effective thickness) ranges from 6 to 61 m. Also, the conventional core analysis affirms that the main reservoirs are of good effective porosity with high horizontal and vertical permeability values. There is a good match between the well-log results and the pressure data with the production data (DST “perforation tests”). Baltim East (BE3) well has the most desired petrophysical characteristics in the Baltim East gas field, while, the Baltim North-1 (BN1) well showed the most favorable petrophysical parameters in the Baltim North gas field. Different fluid contacts (gas water contact GWC) were detected by integrating all reservoir pressures. The integration of different data in our present work (well logs, core measurements, and pressure data) could reduce the drilling risks and help to determine the best locations for future exploration and development, which is considered a big challenge in the petroleum industry.
“…This tool enables geochemical logging by the registration of the K, U and Th curves for each logged borehole with a spatial resolution of 5 cm. The discrimination within the three elements allows obtaining their contribution to the SGR signal (Hesselbo, 1996) and hence localize zones in the aquifer with higher Th and U content that provide a potential source for natural tracers (radium) and K rich layers with high clay content (Schlumberger, 2009).…”
Seawater intrusion (SWI) causes not only salinization of coastal aquifers, but also a reduction submarine groundwater discharge (SGD) and nutrient fluxes to marine ecosystems. We have developed a small scale experimental field site to gain insights into both SWI and SGD. The site is located in a coastal alluvial aquifer at the mouth of an ephemeral stream in the Maresme coastline (Barcelona, Spain). Here, we describe our attempts for a detailed site characterization, which was based on the four pillars of hydrogeology: geology (Lithological description and geochemical analysis of core), geophysics
(borehole logs, Electrical Resistivity Tomography and thermal monitoring), hydraulics (pumping and tidal response tests) and hydrochemistry (major and minor elements, stable isotopes and Radium isotopes for SGD assessment). As it turned out, all four pillars yielded some surprise. The aquifer consists of alluvial sediments, rather than coastal plain deposits. Tidal loading, rather than hydraulic connection to the sea, appears to drive tidal response, in spite of the aquifer being unconfined.
Hydrochemistry suggests an unusually reactive layer, with all cations reflecting some mineral dissolution process, beyond the expected cation exchange. Radium increased with salinity, but the correlation was poor, partly blurred by pH, which was low in the deep portions of the aquifer. These observations were largely explained with the help of geophysics. Both borehole logs and cross-hole ERT helped in identifying silt layers that are frequent in alluvial deposits but proved to play a critical role here. The integration of the different techniques allowed to characterize the different distribution of salt- and freshgroundwater, that in fact yielded an inverse disposition to what is expected in coastal hydrogeology. To improve SGD quantification, we also characterized radium behavior within the aquifer. The recovered sediment during borehole drilling was used to perform both batch and column laboratory experiments. We performed constant salted fluid injections but we also vary the salinity (SWI and SGD simulation) to infer adsorbed Ra from its mobilization. Column experimens were later simulated using a 0D model to interpret the results. We have observed that heterogeneous flux through preferential flow paths occurs in the columns. Variations in these flow paths may explain the observed fluctuations. Such variations may also occur during the freshening and salinization experiments, but the changes in sorption are so dominant that overcome the impact of changes in porosity structure.
La intrusión de agua de mar causa no solo la salinización de los acuíferos costeros, sino también una reducción en la descarga submarina de agua subterránea y en los flujos de nutrientes a los ecosistemas marinos. Para poder entender los efectos que provoca la coexistencia de ambos procesos en acuíferos costeros aluviales, hemos desarrollado un campo experimental a pequeña escala. La zona de campo está ubicada en la desembocadura de una riera efímera en la costa del Maresme (Barcelona, España), en un acuífero aluvial costero. En la presente tesis, se describen los intentos de caracterización detallada del sitio, basada en los cuatro pilares de la hidrogeología: geología (descripción litológica y análisis geoquímico de sedimentos), geofísica (registros de pozos, tomografía de resistividad eléctrica y monitoreo térmico), hidráulica (bombeo y pruebas de respuesta de marea) e hidroquímica (elementos mayores y menores, isótopos estables e isótopos de radio para la evaluación de la descarga de agua submarina). La implementación de los diferentes tipos de técnicas supuso la reconsideración de algunas de las preconcepciones establecidas a priori: la parte del acuífero analizada está constituida por sedimentos aluviales, en lugar de depósitos de llanura costera. A pesar de que el acuífero es libre, parece que la respuesta del acuífero a las mareas está causada por la carga mecánica impuesta por el mar, en lugar de evidenciar la conexión hidráulica con el mismo. La hidroquímica sugiere una capa inusualmente reactiva, con todos los cationes que reflejan algún proceso de disolución mineral, más allá del intercambio catiónico esperado. El radio aumenta con la salinidad, pero no de una manera evidente, debido a que el pH es expecialmente ácido en la zona más profunda del acuífero considerado. La integración de las diferentes técnicas permitió caracterizar la distribución diferentes masas de agua subterránea salada y dulce, que de hecho presentaban una disposición inversa a lo que se espera en zonas costeras. Tanto los registros de pozo como la tomografía eléctrica de resistividad realizada entre los pozos, ayudaron a identificar capas de limo, frecuentes en los depósitos aluviales, pero que demostraron desempeñar un papel fundamental aquí. Para mejorar la cuantificación de los flujos de SGD, también se caracterizó el comportamiento del radio dentro del acuífero. El sedimento recuperado durante la perforación de los pozos se utilizó para realizar experimentos batch y en columna en el laboratorio. Para ello, realizamos lavados consecutivos a salinidad constante, pero también variando la salinidad (simulando eventos de SWI y SGD), para inferir el Ra adsorbido a partir de su movilización. Posteriormente se modelaron los experimentos de columna utilizando un modelo 0D para interpretar los resultados. En las columnas hemos observado flujo heterogéneo a través de caminos preferentes. Las variaciones en estos caminos podrían explicar las fluctuaciones observadas en los experimentos realizados a salinidad constante. Dichas variaciones tambi én pueden ocurrir durante los experimentos de descarga de agua dulce y salinización, pero los cambios en la sorción del radio con la salinidad son tan dominantes que superan el impacto de los cambios en la estructura de la porosidad.
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